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In hot and dry climatic zones, direct evaporative cooling (DEC) system is used as an economical and efficient alternative to traditional air conditioning systems. The present paper concerns comprehensive experimental investigations and analysis of heat and mass transfer characteristics and thermal performance parameters of a bee-hive construction of corrugated-cellulose papers as a new cooling pad material. The performance parameters used to evaluate the effectiveness of the cooling pad materials are the outlet air temperature and relative humidity, pressure drop, humidifier effectiveness, rate of the evaporated water, sensible cooling capacity, specific cooling capacity (SCC), coefficient of performance (COP), specific water consumption (SWC), and Nusselt and Sherwood numbers. The cooling pad performance was investigated for a wide range of air and water temperatures and flow rates and pad thicknesses. The results show the enhancements of heat and mass transfer coefficients and the performance parameters with rising air temperature and water flow rate to humidifier. High values of the performance parameters (h c = 45 W/m2oC and h m = 0.23 m/s, ε h u m = 0.85 and COP = 170) are obtained compared to the traditional pad materials. Experimental correlations for the evaporative cooler performance parameters in terms of air and water temperatures and flow rates pad thicknesses are presented. • Cellulose paper, bee-hive structure has efficient thermal to be used as evaporator cooling pads. • Good thermal-hydraulic characteristics at a wide range of operating and design conditions are obtained. • Presented empirical correlations predict the performance parameters very well. • High values of the performance parameters of the proposed cooling pad were obtained. • The highest saturation efficiency is 84% with associated temperature and pressure drops 18 °C and 8 Pa. [ABSTRACT FROM AUTHOR]

In a construction environment, project scheduling is an essential tool to measure the success of all projects. This research paper will use project crashing of Activity to decrease the project completion schedule through the CPM method of time-cost trade-off and to minimize project cost. It includes linear programming with the aid of Microsoft Excel Solver to determine the result. And at the end of the research paper, it will show the impact of crashing the activities for the HVAC mechanical installation in a project for both normal and crash time, which displays that the selected Activity that had been crashed generated an increase of 9.8 % total cost from the total project cost. [ABSTRACT FROM AUTHOR]

• Realization of an experimental heat pump based on elastocaloric effect. • The device is made of elastocaloric wires crossed by air as heat transfer fluid. • The energy and environmental impacts of the device with many elastocaloric materials were tested. • Evaluation of the environmental impact through a TEWI analysis compared with a HFC32 heat pump. • Ni 55.92 Ti 44.08 and (Ni 50 Mn 31.5 Ti 18.5) 99.8 B 0.2 provide a significant reduction of the environmental impact (−50/−60 %) with respect to HFC32 heat pump. Solid-state refrigeration can constitute a breakthrough point since based on solid-state refrigerants that do not have any direct greenhouse effect (GWP = 0). The refrigeration systems based on caloric effect can be categorized as: magnetocaloric, electrocaloric, elastocaloric or barocaloric. The theme of interest for the investigation introduced in this paper is elastoCaloric Effect (eCE). In this paper the environmental impact in terms of Total Equivalent Warming Impact (TEWI) of an elastocaloric rotary device ensuring continuous fluxes of cold/hot air for the air conditioning applications is evaluated. The final aim is the construction of an experimental device based on eCE working as a heat pump that operates at peak performance and that would be eco-friendly. Indeed, a rotary two-dimensional model based on finite element method was developed to couple with the device during its realization. The device has been virtually tested while mounting various elastocaloric effect materials to examine and select the ones resulting most suitable both from energetical and environmental points of view. The evaluation of the environmental impact has been perpetuated through a TEWI analysis comparing the indexes of the elastocaloric prototype operating with different elastocaloric materials (Ni 50.8 Ti 49.2 , Ni 55.9 Ti 44.1 , Ni 45 Ti 47.2 Cu 5 V 2.75 , (Ni 50 Mn 31.5 Ti 18.5) 99.8 B 0.2 and PbTiO 3) and a vapor compression heat pump (A ++/ A +) working with HFC32. The analysis was perpetuated for both the functioning modes: cooling and heating modes. The most remarkable data on the analysis is that only Ni 55.92 Ti 44.08 and (Ni 50 Mn 31.5 Ti 18.5) 99.8 B 0.2 provide a significant reduction of the environmental impact (−50/−60 %) appropriately selecting the operative conditions (air velocity ranging from 9 to 12 ms−1 and cycle frequency 0.4 ÷ 0.5 Hz). [ABSTRACT FROM AUTHOR]

This paper is aimed at clear ice making. To this end, a purpose-built apparatus that controls the solidification rate was specially designed and constructed to assess the trade-offs between ice clearness (quality) and production rate (quantity). An image-based ice clearness evaluation technique was devised and adopted to compute a figure-of-merit for the ice quality. 30 ml ice cube samples were produced in a closed ice tray for either prescribed heat flux (650, 1300 and 1700 W m−2) or surface temperature (−4, −8 and −12 °C) at the bottom wall, while a 25 mm EPS insulation was adopted for top and lateral walls. The experiments were carried out using both tap and boiled water, whose initial amount of dissolved gas was monitored. The results pointed out the heat transfer and initial air concentration conditions that rule the quality and quantity trade-offs in clear ice making. [ABSTRACT FROM AUTHOR]

• To improve data center performance, it must be efficiently cooled. • This paper undertakes a detailed examination of the most recent cooling optimization techniques. • Several methods are discussed like regular air conditioning, free cooling, and liquid cooling. • An assessment of overhead and underfloor air delivery technologies is presented. • The effects of baffles, variable airflow control, and server placement are investigated. In order to increase data centers' efficiency and performance, a proper cooling system should be applied. This article provides a comprehensive assessment which explores current cooling optimization technologies for data centers. Standard traditional technologies like air conditioning, free cooling, and liquid cooling are investigated. Their limitations as well as proposed improvements are thoroughly discussed. The article also delves into underfloor and overhead air supply technologies, presenting their advantages and drawbacks. The review introduces novel approaches at the rack level cooling, including baffles, variable airflow management, and optimal server placement. Key findings stress the efficacy of optimized airflow systems and innovative rack-level cooling, underlining their role in reducing energy consumption and enhancing overall performance. Notably, potential energy savings of up to 67.2 % compared to traditional methods are demonstrated. The adoption of advanced cooling technologies, such as direct and indirect natural cooling, liquid-cooling cold plates, submersion, heat pipe, and thermosiphon-based cooling, exhibits promising energy efficiency gains and reduced Power Usage Effectiveness (PUE) values. Research into content-specific efficiency enhancements, adaptable energy-saving tactics, and all-encompassing server power consumption models is necessary. To work toward future sustainable, energy-efficient data centers, researchers should investigate how CRACs and server fans interact, find ways to integrate thermal and power management, and how artificial intelligence can be used to cool servers in an eco-friendly way. [ABSTRACT FROM AUTHOR]

The Internet of Things (IoT) is a significant trend in the field of information technology and encourages the implementation of cyber-physical systems, smart connected products, and new business models. Many enterprises struggle to create business value from IoT technology because they have difficulties defining their organizational integration. Model-driven engineering (MDE) is considered an effective technique to address the complexity of IoT application development. Existing approaches focus on requirements from a technical perspective and exhibit a lack of integration with organizational and business model aspects. The paper proposes a modeling approach and a tool to support the development and configuration of IoT solutions in the example of air conditioning and cleanroom technologies (ACT) facilities. The main contributions of this paper are (a) an architecture for the IoT application, (b) a modeling language and tool support for IoT modeling, and (c) the expected practical benefits in the industrial case. [ABSTRACT FROM AUTHOR]

• This study analyzes the effects of temperature anomalies on health using CGSS. • For every 1 °C rise in temperature anomalies, the fitness level decreased by 0.255 units. • The use of air conditioning can avoid negative effect of temperature. We explore the causal relationship between temperature and health at fitness levels in this paper by constructing temperature anomalies using the Chinese General Social Survey (CGSS). The results indicate that for every 1 °C rise in temperature anomalies, the fitness level decreased by 0.255 units, a decrease of 7.081 % of the average. We use the order probit model and the traditional temperature bins to test the results, which are consistent with the benchmark results. The effect of temperature anomalies on health is considerably stronger for males, people over 85 years old, low education, and low-income groups. Further analysis shows that the use of air conditioning can avoid such effects. In addition to the direct impact of temperature, we found that rising temperatures will lead individuals to reduce outdoor activities, thereby affecting their health level. [ABSTRACT FROM AUTHOR]

An efficient fault diagnosis strategy is crucial for the operation of air conditioning systems. In this paper, a novel fault diagnosis strategy based on the signal demodulation method and deep learning model is proposed for a small sample set's fault diagnosis. The potential application of the novel method in air conditioning systems has been discussed through three fault experiments and model evaluation indicators. The signal demodulation method based on principal component analysis (DPCA) is applied in the field of image enhancement innovatively. Compared with the time-domain sample set, the DPCA sample set has stronger features and higher discrimination. The correct rate of the model using the DPCA sample set has been improved by 10.44 %, the loss rate has been reduced by 34.68 %, and the running time has been reduced by 57.13 %. The Back Propagation Neural Network- Principal Component Analysis (BPNN-PCA) model is applied to air conditioning fault diagnosis. Compared with the traditional BPNN and the CART model, the BPNN-PCA model has better fault diagnosis performance and computational efficiency. Through the test and the model performance evaluation indicators, the model optimization strategy has been proposed, and its effectiveness has been verified. This lays the foundation for the optimization and improvement of the model. [ABSTRACT FROM AUTHOR]

In a vapor compression refrigeration system, the oil enhances the efficiency of the compressor but impairs the performance of the heat exchanger. This paper focuses on the experimental study of the influence of oil quantity on the operational stability of CO 2 air conditioning system. The operational stability of the system under different oil charge quantity and operating conditions is studied. The experimental results indicate that when the oil circulation rate increases to a certain value, the adjustment of electronic expansion valve (EXV) opening or the compressor speed will cause system fluctuation and the outlet of evaporator gets close to no superheat. The critical oil circulation rate of the experimental system is about 9.2 %. The analysis of the fluctuation shows that it becomes more severe with the increasing of the refrigerant mass flow rate. When the mass flow rate increases from 210 kg∙ h −1 to 250 kg∙ h −1 at 7000 r min−1 of compressor speed, the fluctuation frequency increases from 0.072 Hz to 0.095 Hz. The occurrence of unstable phenomena has remarkable impact on system performance, the maximum difference of this system in instantaneous cooling capacity and COP during the fluctuation period is respectively 0.5 kW and 0.13. [ABSTRACT FROM AUTHOR]

In this paper, we propose an event-triggered collaborative neurodynamic approach to distributed global optimization in the presence of nonconvexity. We design a projection neural network group consisting of multiple projection neural networks coupled via a communication network. We prove the convergence of the projection neural network group to Karush–Kuhn–Tucker points of a given global optimization problem. To reduce communication bandwidth consumption, we adopt an event-triggered mechanism to liaise with other neural networks in the group with the Zeno behavior being precluded. We employ multiple projection neural network groups for scattered searches and re-initialize their states using a meta-heuristic rule in the collaborative neurodynamic optimization framework. In addition, we apply the collaborative neurodynamic approach for distributed optimal chiller loading in a heating, ventilation, and air conditioning system. [ABSTRACT FROM AUTHOR]

• FDD methods and process discussed in detail. • IoT and cloud technology for FDD is discussed. • Presents the detailed discussion on fault modeling. • Challenges and future prospects of FDD systems are discussed. This review study examines the latest research and developments in the fault detection and diagnostics of Heating Ventilation and Air Conditioning (HVAC) systems. This review describes the basics of Fault detection and diagnostics in the HVAC systems, and the methods developed for the FDD have been discussed in detail. Machine learning methods have become prevalent in the FDD. Supervised and unsupervised machine learning methods have been discussed. Data preprocessing and feature selection are the two essential steps of the FDD process using machine learning. Fault prognosis has also been discussed in brief. Further, fault modeling and its applications in the FDD have been covered. Various approaches have been used to model the different faults in HVAC systems. This paper reviews FDD systems based on four aspects, i.e., detection, diagnostics, prognostics, and modeling of faults. Then this review provides a comparative study of different FDD methods. Finally, the paper discusses future challenges for the more efficient FDD systems to reduce the energy consumption of the HVAC systems. [ABSTRACT FROM AUTHOR]

• This paper presents the thermophysical properties of five commercial PCM • The thermal conductivity of the five PCM is 72-74% lower than water • The dynamic viscosity of the five PCM is from 2.2 to 8.3 times higher than water • The five PCM exhibit significantly lower heat transfer performance than water This paper presents the measurement of liquid phase density, thermal diffusivity, thermal conductivity, and dynamic viscosity of five commercial PCM (RT2HC, RT5HC, OM05-P, OM08, CrodaTherm9.5) in the temperature range 2 − 30 °C. The density of RT2HC, RT5HC, OM05-P is 23-24% lower than water, that of OM08 is 6% higher than water and that of CrodaTherm9.5 is 14% lower than water. The thermal diffusivity of RT2HC, RT5HC, OM05-P is 22-24% lower than water, that of OM08 is around a half of water and that of CrodaTherm9.5 is 38-40% lower than water. The thermal conductivity of the five PCM is 72-74% lower than water. The dynamic viscosity of RT2HC, RT5HC, OM05-P and OM08 is 2 − 3 times higher than water, and that of CrodaTherm9.5 is from 7.4 to 8.3 times higher than water. The five PCM are expected to provide convective heat transfer performance significantly lower than water. [ABSTRACT FROM AUTHOR]

HFC refrigerants as R134a, R404A, R407C and R410A are commonly used in heating, air conditioning and refrigeration (HACR) systems since Kyoto protocol. However, they are phased-out due to their high global warming potential (GWP). There are various options to replace high GWP refrigerants, among all hydrofluorolefin (HFO) fluids, such as R1234yf, represents an excellent alternative. With GWP <1, R1234yf is a promising substitute for R134a. This paper presents the most relevant researches concerning the application of R1234yf in the last decade. This review paper regroups experimental and theoretical studies which assess the performance of pure R1234yf as working fluid of the compression systems such as mobile and residential air conditioning, air and water heat pump, domestic refrigerator and freezer. Studies depict that R1234yf can be recommended for small-scale systems instead of R134a, but an optimization process is necessary to achieve the optimum operating conditions. [ABSTRACT FROM AUTHOR]

The refrigerant distributor helps resolve non-uniform flow distribution issues in multi-path evaporators. Using the CFD method, this paper investigates the distribution mechanism of R410A in a centrifugal distributor under air-conditioning conditions and explores the impact of structural factors on its distribution performance. The Taguchi method is employed to identify the optimal combination of structural parameters and optimization direction for achieving distribution uniformity. Furthermore, the flow distribution characteristics of the optimized distributor are investigated under different conditions. The results show that, under the working conditions of an inlet mass flow rate of 50 kg· h −1 and an inlet quality of 0.1, the non-uniformity of the mass flow rate in the outlet branches of the optimized distributor is only 1.07 %, which represents a decrease of 7.64 % compared to the original distributor. Additionally, the non-uniformity of the outlet branch quality also decreased by 9.41 %. These findings indicate that the optimized distributor exhibits superior distribution performance. Nonetheless, the degradation of the optimized centrifugal distributor's uniform distribution performance with increasing refrigerant inlet mass flow rate and quality suggests that it is more suitable for low mass flow rate and quality conditions. [ABSTRACT FROM AUTHOR]

• Almost all the investigated PCMs are compatible with aluminium, copper, stainless steel, and plastic. • Differences in thermal behaviour were observed despite the same operating conditions were applied. • The thermophysical and transport properties deeply affect the thermal performance of PCMs. • The charging time differs from the discharging one despite the same operating conditions. • The presence of metal lattice structures reduces the charging time more than the discharging one. Refrigeration, air conditioning and heat pump sector represents between 25 and 30% of the global consumption of electricity and this figure is expected to rapidly grow due to the current trend of electrification. To increase the efficiency of these systems or to maximize the use of renewable energy, latent thermal storage systems are being studied and recommended. However, there is a lack of reliable design rules based on trustable data that could help the thermal experts to design efficient and cost-effective latent thermal energy storage. This paper follows a previous work recently published (Longo et al., 2022) where the thermo-physical and transport properties of a few low temperature PCMs (i.e. 2–9 °C of melting temperature) were measured and discussed. In the present work, the attention is focused on two other fundamental aspects: the PCMs' compatibility with the most common construction materials and their thermal behaviour during the solid/liquid phase change. The collected results will contribute to add currently unavailable data in the literature and to highlight interesting insights on the performance of the selected PCMs. [Display omitted] [ABSTRACT FROM AUTHOR]

The scroll compressor is the core component of the air conditioning system. It is important to accurately evaluate the operation status of the air conditioning system. In this paper, the condenser failure is simulated to explore the impact on the scroll compressor by building an air conditioning system experimental platform. The characteristic frequencies and generation mechanisms of vibration and noise signals are discussed through Time-frequency analysis. The characteristic frequencies in the x, y, and z directions are shaft frequency, second harmonic frequency of stator slot and magnet frequency. Abnormal vibration of the scroll compressor caused by changes in pressure and unbalanced electromagnetic force. The modulation characteristic frequency of the signal and the trend of modulation characteristic changes under fault conditions are discussed through signal demodulation methods. The amplitude modulation of the characteristic frequency is enhanced by the unbalanced electromagnetic force on the shaft rotor. The amplitude of the modulation characteristic frequency of the vibration signal in the three directions and the noise signal increases by 45.0%, 17.3%, 71.4% and 123.0%. This study reveals the mechanism and modulation characteristics of vibration and noise of the scroll compressor, and provides support for its fault diagnosis and status recognition. [ABSTRACT FROM AUTHOR]

• Drop-in comparison of R513A and R516A for R134a were tested in refrigeration and air conditioning conditions. • R516 proved to be more suitable for low. • Compressor volumetric efficiency, pressure ratio and superheating for R516A have a similar behavior to R134a. refrigeration temperatures. • The differences in COP of R516A are reduced by up to 5.4% compared to R134a. This paper presents the experimental energy behavior of R516A and R513A compared to R134a as baseline refrigerant in refrigeration and air conditioning temperatures. The comparative is made in an evaporating temperatures range of 261 K to 285 K with step 4 K increases, taking condensing temperatures of 308 K, 313 K, and 318 K. Results show that the best energy performance was reached by R134a while the worst were for R513A in all experimental tests, here R516A shows the smallest difference respect to R134a being just 5.4%. Also, R134a showed lower values in discharge pressure respect to its replacements, while R516A exhibited the lower discharge temperatures. R513A showed lower useful superheating for refrigeration applications, while R516A achieved the minor useful superheating for air conditioning temperatures only below R134a. Finally, R513A reached the higher value of volumetric refrigeration capacity for air conditioning temperatures at 308 K condensing temperature. All results were obtained considering the optimal refrigerant mass charge which were 682 g, 655 g, and 632 g for R134a, R513A and R516A, respectively. [ABSTRACT FROM AUTHOR]

• A CFD fluid-solid coupling simulation model to study the temperature distribution of stator coils and inverter of an electric scroll compressor was developed and validated. • The temperature distribution of stator coils and inverter under different refrigerant conditions was simulated and analyzed. • The working reliability of stator coils and IGBT modules under the studied refrigeration conditions was checked. • The heat dissipation of IGBT modules and the proportion of heat exchange amount between different parts of compressor housing and suction gas were analyzed. In the electric scroll compressor for vehicle air conditioning, the heat generated by motor and inverter is mainly taken away by suction gas. It is necessary to maintain the working temperature of motor and inverter within a safe range to void overheat or burnout. The temperature distribution of motor and inverter under refrigeration conditions are studied using computational fluid dynamics (CFD) simulation in this paper. At first, a CFD fluid-solid coupling simulation model is developed and verified by temperature measurement experiment. The maximum deviation between the simulated temperature at three points on the compressor housing and the measured results does not exceed ±3°C. Then the velocity and pressure distribution of fluid domain, and the temperature distribution of solid domains including the compressor housing, the stator coils and insulated gate bipolar transistor (IGBT) modules are analyzed. Next, the effects of operation conditions on the maximum working temperature and temperature distribution unevenness of stator coils and IGBT modules are discussed in detail. In addition, the working reliability of IGBT modules under refrigeration conditions is checked and the heat dissipation of IGBT modules is analyzed. [ABSTRACT FROM AUTHOR]

Both temperature control and humidity control are important in buildings. However, usually only temperature is controlled in small and medium-sized buildings using direct expansion (DX) air-conditioning (A/C) systems, while dehumidification is a by-product of cooling, and indoor humidity is in an uncontrolled state. Weights-based fuzzy logic control algorithm (WBFLCA) is a novel fuzzy control algorithm that can be applied to DX A/C systems with good simultaneous temperature and humidity control performance. However, the setting of weight values for WBFLCA is still highly dependent on expert experience and lacks a systematic optimization theory, which hinders the application of WBFLCA. In order to establish a weights setting rule for WBFLCA used in DX A/C systems, a coupled control simulation model is built in this paper to simulate the effect of simultaneous control of temperature and humidity with all 16 basic weights distribution mode combinations. All the 16 combinations are also experimentally tested on an experimental DX A/C system to reveal the control performance of different combinations in a real system. Four of them with good control performance are found. The reasons why these four combinations are good are also analyzed in this paper. Based on the simulation and experimental results, the weights setting rule of WBFLCA applicable to the simultaneous temperature and humidity control of DX A/C systems are summarized. The approach proposed in this paper of finding appropriate pattern combinations from the basic weights distribution patterns has the potential to be applied to solve other decoupling control problems as well. [ABSTRACT FROM AUTHOR]

Most methods for creating an indoor thermal environment are based on controlling heating, ventilation, and air conditioning (HVAC) systems and do not consider the various needs of individuals in a multiperson space. Personal comfort systems (PCS) and personal comfort models (PCM) are popular technologies for achieving personal thermal comfort. This paper presents a thermal environmental collaborative control system (TECCS) that regulates environments at different spatial scales by leveraging the advantages of the HVAC system, PCS, PCM, and PCM-based automatic control to address the issue of individual differences in thermal demand in multiperson environments. The TECCS predicts thermal sensation votes (TSV) by combining facial skin temperature data obtained by an infrared sensor with environmental parameters. Subsequently, it performs the corresponding PCS control and adjusts the air conditioner according to the operating state of the PCS. This study proposes a collaborative control strategy with PCS at the core, enabling communication between thermal state recognition, HVAC system, and PCS. Twenty-eight adult males participated in the experiments testing the TECCS's performance. The results indicate that the TECCS can automatically regulate environments at different spatial scales based on thermal sensation prediction and that the operating state of the PCS can effectively guide air conditioning operations. Compared with constant setpoint control, the TECCS offers the advantage of improving thermal comfort. This paper also proposes future optimization directions based on the research results, focusing on recognition, equipment, and control. [Display omitted] • Skin-temperature-based comfort model and device collaborative control strategy. • Match occupant needs with environmental heat and cold supply. • Personal comfort system plays the role of both feedback and effector. • Realize the information interaction between occupants, PCS, and HVAC. • Prove the comfort improvement effect of the proposed system by subject experiments. [ABSTRACT FROM AUTHOR]

The electricity required for air conditioning is soaring worldwide. Absorption chillers represent an alternative to classical vapor compression systems, using heat instead of electricity. However, absorption chillers powered by renewable geothermal heat have received little attention so far. This paper introduces a system using a hot geothermal fluid (typically in the range of 80–110 °C) to produce cooling through a single-effect absorption chiller, and Domestic Hot Water (DHW) through a heat exchanger. It considers a hotel located in Martinique, a French Caribbean island. The electric consumption of every subsystem has been thoroughly estimated. The originality of this paper is twice: i) the system is modelled in TRNSYS software considering dynamic conditions, ii) the system undergoes surrogate modelling and multi-objective optimization to minimize both the cost and the CO 2 content of the delivered thermal energy. Several scenarios are considered, depending upon the geothermal temperature, mass flow rate, well remoteness, and demand size. The studied system appears to be systematically more expensive than a combination of a classical vapor compression chiller and a boiler for DHW. However, it can significantly decrease the CO 2 content of the provided energy, especially in an island where most electricity is generated from fossil fuels. The proximity of the geothermal well and the use of the warm water leaving the absorption generator (here for DHW production) appear to be key factors for system relevance, along with a hotter geothermal fluid (e.g., 110 °C instead of 80 °C). • A geothermal absorption chiller in tropical climate is modelled. • The influence of design parameters on electricity consumption is investigated. • The system undergoes multi-objective optimization. • The well proximity and geothermal temperature are keys to the system relevance. [ABSTRACT FROM AUTHOR]

In their quest to enhance energy efficiency and carbon footprint management, many enterprises are turning their attention towards optimizing their facilities through amplified data monitoring and innovative control methods. In this context, this research highlights a practical solution in a commercial building located in the United States. It explains the creation, implementation, and costs of a universally applicable model predictive control (MPC) framework for the building's heating, ventilation, and air conditioning (HVAC) system. The paper elaborates on both the hardware and software used to accumulate pertinent data and the formulation of the MPC system. This approach leverages cloud-based microservices and can be seamlessly integrated into current building management systems. In this regard, this paper presents three innovative strategies: Proportional–integral (PI)+Preheating, MPC, and occupancy-based control. These scenarios were designed to improve energy efficiency and thermal comfort significantly by reducing temperature fluctuations and adhering more closely to the setpoint temperature. The implementation of these strategies resulted in substantial energy savings, with reductions in energy consumption of 12.83%, 19.21%, and 14.98%, respectively. • A novel cloud-based MPC scheme is proposed for controlling the educational building HVAC system. • Real-world case installation details are provided with a focus on cost and sensor information. • A comprehensive discussion on thermal modeling, occupants' comfort, and control performance. [ABSTRACT FROM AUTHOR]

In many countries distributed energy resources (DER) (e.g. photovoltaics, batteries, wind turbines, electric vehicles, electric heat pumps, air-conditioning units and smart domestic appliances) are part of the 'Green Deal' to deliver a climate neutral society. Policy roadmaps, despite providing a framework and penetration targets for DER, often lack the network planning strategies needed to transition from passive to active distribution networks. Currently, DER's dynamic performance parameters and location identification techniques are not fully standardised. In fact, it can be very ad hoc. Standardised distributed load modelling and non-intrusive load monitoring (NILM) for equipment manufacturers, installers and network operators is critical to low and medium voltage network management in order to facilitate better balancing, flexibility and electricity trading across and within the power system for mass DER deployment. The aim of this paper is to fill this load modelling and NILM knowledge gap for DERto inform the 'Green Deal' transition and support standardisation. In the paper, existing load modelling techniques and NILM methodologies are critically examined to inform and guide research activity, equipment development and regulator thinking, as well as network operators. Seven key findings that need urgent attention are identified to support a smooth power system reconfiguration. [Display omitted] • A thorough review of existing monitoring and modelling methods for DER on distribution networks is provided. • Efficacies between 65% and 95% for conventional load identification exist. • Increasing DER penetrations are creating technological challenges in distribution networks. • Optimum DER integration in low voltage networks is vital for electric networks reliability. • Seven aspects to enable massification of DER on distribution networks are established. [ABSTRACT FROM AUTHOR]

Life Cycle Climate Performance (LCCP) is a widely accepted metric to evaluate the carbon footprint of air conditioning (AC) systems "from cradle to grave." This paper: (1) reviews the invention and evolution of LCCP, including a comprehensive timeline and bibliography; (2) documents the successful application of LCCP in the replacement of HFC-410A with HFC-32 in room air conditioners; (3) compares the conceptual frameworks and the operational approaches; and 4) reflects on the drawbacks of current LCCP research and points out possible future work. The major policy-relevant findings are: 1. The indirect emissions caused by energy consumption is 70 to 80 percent of the LCCP of AC systems in most countries but will decline in importance as electric power supply shifts rapidly from fossil fuel to renewable energy sources, which have near-zero carbon intensity; 2. The embodied greenhouse gas (GHG) emissions in refrigerant manufacture are, in most cases, negligible but the physical and chemical properties are crucial for system optimization for low carbon footprint; 3. The LCCP metric can be used for multiple purposes such as refrigerant selection and AC system architecture optimization; and 4. Data limitations in material manufacturing and the carbon intensity of electric power are the most significant challenges. Finally, this paper describes a variety of methods to fill in data gaps, including the correction factor method , the data-driven method , and the database searching method. The next-generation LCCP will be an enhanced evaluation process considering local climate, heat islands, and local power supply characteristics. [ABSTRACT FROM AUTHOR]

This paper reviews the progression in refrigerants for chillers, from historical selections through current options and projections for the future. It examines the global environmental issues that catalyzed recent changes. It then discusses candidate refrigerants in the context of future availability (or phaseout) based on controls for environmental protection, efficiency, toxicity, flammability, and escalating future costs. It notes that negative marketing and conflicting claims, intended to discredit competitor''s approaches, create confusion and retard replacement of older, less-efficient equipment. The result hurts the environment, increases costs, and stifles the chiller market. The paper concludes that most of the current anxiety with refrigerant selections is unwarranted. Engineers, building owners, and others involved in chiller decisions should revert to traditional chiller specifications based on cost, performance, local manufacturer support, service options, and reliability. Anticipating more stringent environmental regulations, they also should take all practical steps to reduce refrigerant releases and increase efficiency. The paper examines future refrigerant options for chillers. Noting that there are no ideal refrigerants and that none are likely to be found, it recommends scientific determination of acceptability rather than market manipulation. [Copyright &y& Elsevier]

• Two CO 2 air conditioning systems based on liquid cooled gas cooler (LCGC) were developed. • The cooling performances of direct and secondary loop systems were experimentally compared. • The effects of refrigerant charge, CO 2 cycle parameters, and air-side parameters were investigated. • Exergy analysis revealed the enhancing potentials of the Chiller and evaporator. As a natural refrigerant, CO 2 is considered one of next generation refrigerants of electric vehicle (EV) applications for excellent environmental and heating performance. The integration and safety performance of CO 2 systems could be enhanced by secondary loop configuration, which is highly valuable for practical applications. This paper investigates the cooling performance characteristics of direct (DAC) and secondary loop (SLAC) transcritical CO 2 air conditioning systems based on liquid cooled gas coolers (LCGC). A series of steady-state experiments were carried out for both systems to study the effects of compressor speed, EXV opening, outdoor air velocity, and indoor air flow rate on the cooling performances. Furthermore, the exergy destruction of each component and the exergy efficiency of both systems were analyzed based on the experimental results, showing that the evaporator needs to be better designed to balance heat transfer performance with pressure loss performance. The results showed that the cooling capacity and COP of SLAC system were reduced by up to 9.1% and 10.8% under the same compressor speed, compared with the DAC system. This study presents experimental references for further research and practical extension of the CO 2 mobile air conditioner. [ABSTRACT FROM AUTHOR]

• Vacant heating core in cooling mode was first utilized for evaporation. • A series cross-parallel dual-evaporator configuration was recommended. • An automotive CO 2 air conditioner with the recommended configuration was tested. • COP was improved by 6∼12% without additional cost. Inefficient performance of CO 2 refrigerant in hot climates has become a major obstacle to its wide application in electric vehicles. In this paper, the vacant heating core in cooling mode was exploited to increase the heat transfer area of evaporator and improve system performance. With the aid of a validated evaporator model and an experimental test rig, performance improvements brought by this added area were evaluated. Results indicated that this area is not suggested to be directly added to cooling core. This necessitates a dual-evaporator (D-E) configuration. For case I (small CO 2 pressure drop), the growth rate in heat transfer rate brought by D -E configuration is 19∼20% and less sensitive to parallel or series operation. Nevertheless, this growth rate for case II (large CO 2 pressure drop) is greatly affected, 30.6∼32.6% for parallel operation and 7.5∼17.6% for series operation. Specifically, it is around 17.5% and 7.5∼13.6% for series cross-parallel and cross-counter arrangements, respectively. By comprehensive consideration, the cross-parallel arrangement is recommended to be adopted. Experimental results indicated that the cross-parallel D -E configuration greatly increases the evaporation temperature and exhibits a slight impact on optimum high pressure within the transcritical cycle. The enhancement in COP brought by this configuration is around 6∼12% without additional cost, and it rises with the decreased air flowrate through evaporator and air velocity through gas cooler and the increased ambient temperature. This indicates that this configuration is an effective and economical technology to alleviate the efficiency degradation issue of transcritical CO 2 automotive air-conditioners. [ABSTRACT FROM AUTHOR]

This paper discusses the design procedure and first results of a large-scale magnetic air-conditioning system prototype demonstrated in a relevant environment compatible with the Technology Readiness Level (TRL) 6. The prototype, which contains all components of a functional cooling system, was experimentally evaluated in an especially developed calibrated calorimeter designed according to international technical standards for testing split-type air-conditioning units. The proposed experimental analysis is one of the first to quantify the impact of external losses associated with the heat exchangers on the cooling system performance. For outdoor and indoor temperatures fixed at 35 and 27 °C, respectively, the coefficient of performance disregarding thermal, flow and mechanical losses beyond the limits of the active magnetic regenerator was 5.72, corresponding to a second-law efficiency of 20.7%. When these losses and other essential operating variables, such as the heat exchanger fan power and the valve power consumption, are included, one-order-of-magnitude reductions are observed in the performance parameters, indicating that they should not be neglected in realistic assessments of not-in-kind cooling technologies. • Design and evaluation of a TRL-6 magnetic air-conditioning prototype is presented. • Tests conducted in a calibrated calorimeter for split-type air-conditioning units. • Impact of heat exchanger losses on the performance parameters is quantified. • The AMR coefficient of performance and second-law efficiency are 5.72 and 20.7%. • Internal and external losses are highly detrimental to the system performance. [ABSTRACT FROM AUTHOR]

• The performance of a scroll compressor under two operating conditions was assessed. • The optimal OCR values for the two conditions were found to be 3.5% and 5.5% respectively. • Optimal air injection pressures on the two conditions were 0.27 and 0.45 Mpa respectively. • An empirical formula for the heating capacity as a function of vapor injection coefficient and OCR was derived. Heat pump air conditioning (AC) based on a vapor injection scroll compressor has proven to be a promising solution to the current driving range limitations of electric vehicles (EV), especially in freezing climates. The lubricating oil inside the compressor is critical in promoting sealing and cooling, but it also exhibits a low performance under extreme working conditions. In addition, the effects of oil retention on compressor behavior and the optimal charge amount at low temperatures require further investigation. This paper adapts a second refrigerant calorimeter method to study the effects of different injection pressures on compressor performance. The results indicate that the mass flow rate, discharge temperature, compressor power consumption, and volume efficiency performance would increase significantly compared with the non-vapor injection (NV). The effects of oil circulation rate (OCR) on the performance of a vapor injection scroll compressor under two low-temperature operating conditions were also studied. The flow and heat transfer parameters were analyzed, and heating capacity was found to increase and decrease with enlarged OCR. The highest coefficient of heating performance (COP) was obtained at an OCR of 3.5% with a vapor injection pressure of 0.28 MPa. Compared with the non-vapor injection (NV) condition, the heating capacity and COP of the system at the same pressure of 0.28 MPa were increased by 6.2% and 1.8%, respectively. At extremely low temperatures, the heating capacity and COP were maximized at an OCR of 5.5% and an injection pressure of 0.45 MPa. Compared with that of NV, the heating capacity and COP of the heating system at the injection pressure were increased by 6.7% and 2.6%, respectively. The compressor discharge temperature decreased obviously with the increasing OCR. An empirical formula was devised to calculate the heating capacity for varying OCR. [ABSTRACT FROM AUTHOR]

With recent energy and environmental crises, the energy consumption prediction of air conditioning (AC) is essential. Notably, existing general prediction systems use the air temperature, real-time AC usage, time, occupancy, and AC historical energy consumption as inputs and employ feedforward neural networks. However, such systems face certain challenges. First, the input system may be difficult to reflect the real-time interaction among the building environment, occupants, and energy system; Second, the algorithms need to be upgraded to further improve accuracy, speed up convergence, and avoid overfitting. his paper introduces a novel parameter (group occupant behavior probability, GOBP) in the input system; and uses swarm intelligence algorithms with chaotic mapping and adaptive weight adjustment as optimization with LSTM and BP as the basic algorithms. The verification results obtained from five different buildings indicate the following: (1) The novel prediction system improved prediction performance with 20.08%–78.37 % of MAPE and 3.99%–53.28 % of CV-RMSE, however, it will increase 148.70s–1065.11s of calculation time. (2) For accuracy, using GOBP will improve the 0.30%–51.87 % and 0.18%–64.77 % by using swarm intelligence optimization algorithms. (3) This paper discusses the priority of selecting suitable inputs, algorithms, and optimization to combine a whole prediction system. • The definition of a simplified model using the group occupant behavior probability is proposed. • The chaotic mapping and adaptive weight adjustment are used for optimizing the swarm intelligent algorithms. • A reconstituted AC energy consumption prediction system is proposed with novel inputs and improved algorithms. • The reconstructed prediction system demonstrates improved prediction accuracy and data acquisition difficulty\. • The best combination of inputs and algorithms is discussed based on 60 groups of comparative experiments. [ABSTRACT FROM AUTHOR]

In this paper, the integral performance indicator for selecting HVAC systems (ACPI) is applied to select the Air Conditioning (AC) system with better results in their life cycle for a typical building in Barranquilla, Colombia. The AC systems under study were: direct expansion system (Split and VRF), air-cooled system (VAC and VAV), and water-cooled system (Chiller). Of the six selection criteria of ACPI, the energy consumption index (EC) and thermal comfort (TC) were calculated through energy simulation of buildings, the regulations were used for IAQ and carbon emissions (CE), and were estimated the investment costs (IC) and operating and maintenance costs (OMC). The best-performance AC system for the building was the air-cooled AC system got the best ACPI values between 25 % and 22.4 %, followed by the water-cooled system with 22.3 %, and finally the direct expansion systems between 16.8 % and 13.5 %, influencing in this level of priority the IAQ and IC criteria. This study contributes to introducing in Colombia a multifactorial analysis to select the more proper AC system technology according to the building and location conditions. [ABSTRACT FROM AUTHOR]

The widespread adoption of low GWP alternative refrigerants across Europe is critical to achieving long-term carbon reduction emissions from the Refrigeration, Air Conditioning and Heat Pump (RACHP) sector. The RACHP sector has been identified as being responsible for significant greenhouse gas emissions through direct emission (leakage of high GWP refrigerants) and indirect emissions (energy use). The changes to EU's Fluorinated greenhouse gases (F-gas) regulation No 517/2014, which came to force since 1st January 2015, has enacted restrictions on the use of halocarbon refrigerants in certain applications with the intent of reducing the F-gas associated emissions in the EU region. There are currently inconsistent levels of knowledge and awareness of how alternative refrigerants can be sustainably procured and utilised. This paper provides an understanding of the needs for skills in some European countries, specifically covering the general overview of the "as installed" RAC use, the current training provision, the potential use and status of alternative refrigerants and recommendations on procurement process. Furthermore, the paper discusses the availability of skills and existing training materials and template in specific European countries. [ABSTRACT FROM AUTHOR]

This paper covers a basic model for analyzing the performance of the Claridge-Culp-Liu dehumidification process. The fundamental process efficiency limit for dehumidification is close to COP Carnot , but for the eight dehumidification cases examined, the limiting or ideal energy use required is 26% to 56% that of a Carnot condensing system as shown in an earlier paper. The model presented in this paper is used to show the membrane system performance reduction caused by finite membrane area, finite water vapor permeance, non-zero air permeance, non-zero system air pressure drop, non-ideal compressors, vacuum pumps, and condensers. The performance of a "conservative" membrane system based on the use of existing components is computed for eight specific conditions along with that of a "target" system that assumes expected component performance after additional future component development. The "conservative" membrane system would use 36% to 66% as much energy as a system with a COP=7 chiller to produce the same dehumidification for the eight cases examined while the "target" system would use 15% to 40% the energy of a system with a COP=7 chiller. In addition to the significant energy reduction over conventional technology, the membrane system offers the advantages of: 1) no HFC refrigerant use; 2) direct isothermal control over humidity ratio setpoint; 3) maximum capacity occurs at design conditions; and 4) system generates pure water extracted from air as a by-product. [ABSTRACT FROM AUTHOR]

This paper presents the design of a testing facility at Oklahoma State University that enables performance testing of commercial-sized air to refrigerant heat exchanger coils. The closed-loop facility contains the necessary equipment to condition the air supplied to the tested coil. This includes the glycol conditioning system for the air conditioning heat exchangers, fans, electric heaters, and a steam humidification system. The design is compliant with multiple ASHRAE standards; the airflow measurement apparatus is compliant with both, Standard 41.2 (1987 and 2018). The test section's cross section is 2.13 m wide by 2.44 m tall with a maximum airflow rate of 3.78 m3 s−1. The thermal model presented in this paper predicts a maximum capacity of 80.9 kW for air heating coils (e.g. refrigerant condensers) at an air inlet temperature of 19.4 °C. The specified air flowrate and facility's maximum flowrate limit the capacity of air cooling (e.g. refrigerant evaporators) to a range of achievable values. The facility will operate over an air temperature range of −17.8 °C to 60 °C. Future work includes completion of construction of the facility including physical assembly, assembly of psychrometers, and commissioning of the developed facility control software. [ABSTRACT FROM AUTHOR]

In industrial applications, model predictive control (MPC) is typically installed in a hierarchical operational framework above regulatory layer proportional–integral (PI) controllers. Traditional MPC implementations do not include a dynamic model of the regulatory layer PI controller in the MPC optimization problem. This paper presents case studies to illustrate the advantages of modeling the PI controller in the MPC optimization problem. A PI controller implemented with an antiwindup scheme introduces significant nonlinearity into the MPC model that can be challenging to optimize with standard nonlinear solvers. Therefore, an approximate linear PI control law model is proposed for use in the MPC optimization problem. Hard constraints of the plant actuator manipulated by the PI controller are also included in the MPC problem. We illustrate using simulation studies that this PI controller modeling approach in the MPC optimization problem provides the following advantages: (i) systematic constraint handling in the presence of an unmeasured disturbance in the PI feedback loop, (ii) disturbance rejection forecast of the PI controller in the MPC optimization problem for a slow PI feedback loop, and (iii) optimizing plant economics of a cascade control architecture in which the PI controller manipulates a variable that directly influences the economic objective. Case studies on a continuous stirred tank reactor (CSTR) and heating, ventilation, and air-conditioning (HVAC) system are presented to highlight these advantages of modeling the PI controller in the MPC optimization problem. • Advantages of modeling PI controllers in MPC optimization problems are presented. • Modeling PI controllers enables the MPC to treat disturbances in the PI loop. • The PI controller modeling approach also aids the MPC to optimize plant economics. [ABSTRACT FROM AUTHOR]

• A Thermal Diode Tank (TDT) passively produces water at a minimum ambient temperature. • A Radiation-enhanced TDT (RTDT) has better performance than a Conventional TDT (CTDT). • Increasing heat pipe condenser areas is the best way to improve RTDT performance. • The RTDT Heat Transfer Capacity is about double the CTDT under similar conditions. • Cooling the RTDT water to below the ambient temperature is neither cost-effective nor practical. A Thermal Diode Tank (TDT) is invented for energy conserving purposes that can passively produce cooling water at a minimum night ambient temperature. The TDT is an insulated water tank equipped with heat pipes, which provides unidirectional heat transfer from the TDT water to its surroundings. The conventional heat pipes dissipate heat mainly by convection heat transfer, which are termed Convective Heat Pipes (CHPs), and a TDT equipped with CHPs is a Convection TDT (CTDT). To promote the TDT performance in generating cooling water at a lower temperature, a Radiation-enhanced Heat Pipe (RHP) is proposed with a flattened hollow cuboid as its condenser section to radiate heat to the night sky, while maintaining the convection heat transfer with air. Such a Radiation-enhanced TDT (RTDT) is expected to have a better water-cooling performance than CTDT currently obtains, and could potentially cool the water below the minimum ambient temperature. In this paper, performance simulation models for both RTDT and CTDT have been developed and validated by the experiment. The results reveal that the RTDT generates colder water than CTDT does, and the heat transfer capacity of the RTDT is approximately twice as high as that of the CTDT if they are made from the same quantity of materials. It is found not advisable to promote the TDT performance by increasing the air circulation at the heat pipe condenser. However, analysis shows that increasing the heat pipe condenser area dominantly contributes to the enhancement of TDT performance, especially for RTDT. [ABSTRACT FROM AUTHOR]

• An Eulerian-Lagrangian model is used to predict dispersion of COVID-19 droplets. • Quality distribution of infection in a conference hall has been explored. • The effect of the ventilation registers displacement on air flow is studied. • Proper layout of ventilation register to decrease the exposure time are proposed. The outbreak of the COVID-19 has affected all aspects of people's lives around the world. As air transmits the viruses, air-conditioning systems in buildings, surrounded environments, and public transport have a significant role in restricting the transmission of airborne pathogens. In this paper, a computational fluid dynamic (CFD) model is deployed to simulate the dispersion of the COVID-19 virus due to the coughing of a patient in a conference hall, and the effect of displacement of supply and return registers of the air conditioning system is investigated. A validated Eulerian-Lagrangian CFD model is used to simulate the airflow in the conference hall. The particles created by coughing are droplets of the patient's saliva that contain the virus. Three cases with different positions of supply and return registers have been compared. The simulation results show that case1 has the best performance; since after 80 s in case 1 that the inlet registers are in the longitudinal wall, the whole particles are removed from space. However, in other cases, some particles are still in space. [ABSTRACT FROM AUTHOR]

Hydrofluoroolefins (HFOs) have been attracting increasing attention over the recent decade, and some of them are regarded as candidates for next-generation refrigerants. In this paper, the flammability characteristics of forty-eight HFOs and blends have been relatively comprehensively and systematically summarized, for a variety of experimental conditions on the basis of the results reported in academic journal papers, professional books, conference proceedings, technical reports, patent applications, material safety data sheets, and presentations. The following flammability characteristics of HFOs are reviewed, including the lower flammability limit, upper flammability limit, burning velocity, minimum ignition energy, hot surface ignition temperature, autoignition temperature, thermal decomposition temperature, heat of combustion, product of combustion, etc. Besides, a new correlation equation has been suggested to roughly indicate the burning velocity and heat of combustion rankings of the fluorinated hydrocarbons once their basic molecular characteristics are known. In addition, the experimental methods, influencing factors, inerting mechanism, and developing tendency of the flammability of the HFO refrigerants are discussed. The details presented are expected to be useful for researchers working in the field of heating, ventilation, and air conditioning and refrigeration. [ABSTRACT FROM AUTHOR]

This article provides details of some significant patent, patentee and invention anniversaries falling in 2006, for example those for improved paper making and sugar production, Brunel, iron and steel manufacture – the Bessemer process, aniline dyes, an improved electric clock, air conditioning, an improved flying machine, and radio navigation for aircraft. [Copyright &y& Elsevier]

[Display omitted] • The LCA methods and findings of 41 papers on air-conditioning systems are examined. • Retrieved studies presented discrepancies in the LCA goals and scope definition. • The global warming potential (GWP) was the most evaluated indicator across papers. • Grid-connected electrical heat pumps generally had a higher life cycle GWP. • Improvements related to AC energy sources and other life cycle aspects are proposed. Air conditioning (AC) has become the fastest-growing energy end-use in buildings worldwide, and its adoption is expected to increase further due to various socioeconomic factors and climate change. Despite this, the decarbonization of space cooling is progressing slowly; hence, the emissions burden at each stage should be examined in detail. Given this context, it is crucial to assess the environmental performance of AC systems by considering a comprehensive approach like the Life Cycle Assessment (LCA). While several studies have already targeted the LCA of AC systems, a clear overview of those studies' methodologies, assumptions, and results is still lacking. Therefore, this systematic review examined the methods and key findings of 41 peer-reviewed articles. Although the results revealed discrepancies among the goals and scope, impact assessment methods, and indicators, most articles predominantly focused on the global warming potential (GWP) impact, and its reported quantification was further analyzed. It was observed that grid-connected vapor-compression heat pumps/chillers (conventional systems) presented higher GWP impacts than other AC systems powered by renewables, which in contrast, exhibited higher impacts in some toxicity and resource depletion-related indicators. However, the share of GWP showed different distributions, as the pre-operation emissions of solar-powered AC systems (either PV or thermal) were higher than those of conventional systems, mainly driven by reduced energy consumption usage. This review concludes with some recommendations for each stage of the life cycle. Since the operation phase generally showed the highest impact, more efforts should be devoted to accelerating the transition to a 100% clean electricity power system at a national scale. In contrast, the need to power AC systems with on-site renewables should be carefully assessed based on the context. [ABSTRACT FROM AUTHOR]

• The research carried out in the present article and the results obtained are innovative. Based on experimental and numerical research, new proprietary parameters were developed to determine the properties of laminated glass consisting of VSG laminated glass reinforced with PVB interlayers exposed to vehicle impact. • This paper presents an analytical model, developed for laminated glass subjected to a low-velocity impact. It has the ability to capture glass cracks as well as large non-linear deformations. • We also assessed the strength of the laminated glass wall (taking into account the new material parameters) with an appropriate thickness at ground floor level in a building with a high degree of terrorist threat in terms of vehicle impact. • New strength parameters of laminated glass with PVB vinyl interlayers were clearly indicated and identified, and the method of obtaining them was determined. These parameters were proved to very accurately reflect the mechanics of glass cracking in the non-elastic range under the impact of a motor vehicle depending on the prevailing weather conditions and air temperature. • The new parameters of laminated glass can be implemented as a ready-made input.mat file of the material available in the material library under the name MAT_112-FINITE_ELASTIC_STRAIN_PLASTICITY in the LS-DYNA suite. • The developed analytical model allows for a quick and reliable assessment during the initial design of safety glass, where a full-scale FE analysis is often too time-consuming. This paper presents an analytical model, developed for laminated glass subjected to a low-velocity impact. It has the ability to capture glass cracks as well as large non-linear deformations. It is based mathematically on the first-order deformation concept, which considers the effect of membrane and transverse shear as well as bending. This theory uses damage mechanics to capture the glass cracking. For this purpose, several experiments have been carried out based on PVB laminated glass. The history of acceleration, transverse central displacement and velocity estimated over time is in a favourable relationship with the experimental information. In terms of laminated glass, non-dimensional coefficients have been suggested that regulate both the first peak contact force and the maximum transverse displacement. Laminated glass consists of several layers of soda-lime glass sheets bound together by intermediate layers of polyvinyl butyral (or PVB). Cracking of the glass layer is the main cause of laminated glass damage under both low and high-speed impacts. The main objective of the present article is to conduct experimental studies and numerical analyses of the glass ply cracking mechanism as part of the development of new strength parameters for PVB laminated glass. The non-linear characteristics of PVB are described using the Mooney-Rivlin constitutive model. The present article proves that it is possible to precisely model a wall made of VSG (Verbund Sicherheits Glas) laminated glass reinforced with a vinyl interlayer of appropriate thickness, and further, that such walls can constitute an element absorbing the impact energy of vehicles with specific parameters such as a passenger car, buses, and HGVs (Heavy Goods Vehicle). Based on the results of our study, new parameters were elaborated to determine the properties of PVB laminated glass exposed to vehicle impact. These new parameters were verified qualitatively by comparing the simulation results with experimental observations. We also assessed the strength of a wall of adequate thickness made of laminated glass at the ground floor level of a building exposed to a high-risk terrorist attack. The developed analytical model allows for a quick and reliable assessment during the initial design of safety glass, where a full-scale FE analysis is often too time-consuming. [ABSTRACT FROM AUTHOR]

This paper presents the design and application of a virtual sensor used in case of failure of the main physical sensor for temperature readings in automotive air conditioning. Using auxiliary temperature and pressure physical sensors combined with Support Vector Machine (SVM) Regression, the model of the virtual sensor is derived and prepared to be used as a redundant sensor until the broken physical sensor maintenance. Thus, enabling the system to operate continuously and maintaining its original power and thermal comfort features until the physical sensor replacement. In total, 32 h of training and test data involving different environmental conditions were used to generate the model that was further integrated. The designed virtual sensor presented a Mean Square Error (MSE) of 1 , 3 o C , a Mean Absolute Percentage Error (MAPE) of 3 , 6 % , and a Pearson Correlation Coefficient of 0,90. The results enabled the continuous and autonomous operation of the air conditioning plant respecting the designed thermal comfort guidelines even when under the physical sensor failure condition. [ABSTRACT FROM AUTHOR]

Ducts are conduits or passages used to supply, return, or exhaust air, needed for heating, ventilation, or air conditioning in multistory gigantic building structures. Rapid growth in population (especially in industrially concentrated regions) has led to the culture of constructing skyscrapers of tens of storeys, in which vertical ducts are the natural choice for removing polluted air. Due to the compactness of the building design, high voltage current-carrying wires are usually located very close to exhaust ducts carrying polluted air. Consequently, a natural motivation is to study how the magnetic field produced by such a wire affects the flow, driven by an external pressure gradient (for example, exhaust fan, vacuum pump, etc.) in a vertical duct. Therefore, the paper is devoted to understanding the interaction of the developed (thermally and hydrodynamically) flow in a vertical square duct with the magnetic field produced by a nearby placed current-carrying wire. The flow is assumed to be laminar and is driven by a constant external pressure gradient. For the thermal boundary condition, we assume a uniform heat flux across the unit axial length whereas a fixed temperature is also assumed over the peripheral surface of the duct. As a result of the mathematical modeling of the problem, we come across a system of coupled Poisson-like equations which are solved numerically by following a finite volume approach. We have noted that a sufficiently higher Rayleigh number may cause a reverse flow while reducing and flattening the thermal distribution in the middle of the duct. In addition the magnetic field further reduces the flow velocity, particularly near the duct wall where the current-carrying wire (causing the magnetic field) is positioned. [ABSTRACT FROM AUTHOR]

The offshore wind turbine three-bucket jacket foundation (TBJF) bears some complex force at the stage of lowering though splash zone, and two nonlinear phenomena appear in the bucket foundation: The air cushion structure is formed in the bucket and generates a slamming force on the roof. This paper point at two nonlinear phenomena, the model tests research on the lowering and installation of the TBJF are carried out. The effects of waves and control conditions on air cushion response, the variation law of sling tension and the dynamic characteristics of foundation are investigated. Moreover, the calculation formula of air pressure during foundation lowering process on comprehensively considering various factors to be deduced. In contrast to the experiment tests, the contraction coefficient is revised. In addition, different theoretical analysis models of slamming load on roof during lowering process are established. The influence mechanism of the foundation structure, perforation ratio and lowering speed on the response of air cushion structure and slamming load are revealed. Meanwhile, the attitude control mode during the lowering process of the TBJF is defined. This study provides a theoretical basis for the optimization of foundation installation construction technology and cost control. [ABSTRACT FROM AUTHOR]

Regulatory changes worldwide are requiring air conditioning and heat pump equipment manufacturers to switch refrigerants to alternatives with reduced global warming potential (GWP). Design of air-to-refrigerant fin-and-tube heat exchangers (FTHXs) is critical to overall performance of this equipment and is not currently well understood with low-GWP refrigerants. This paper presents a simulation study exploring the impact of design changes for a FTHX used in an indoor residential evaporator originally designed for R410A. Simulation results are used to generate design guidelines for FTHXs using HFO refrigerants R1234yf and R1234ze(E), evaluated using cooling capacity, refrigerant-side pressure drop and ratio of the two as critical metrics. When evaluated at identical operational conditions, with fixed refrigerant outlet superheat, it was found that for a fixed slab size, the FTHX was most sensitive to number of circuits, followed by tube diameter, number of tubes in the FTHX, and fin density. For the low-GWP HFOs, circuitry modifications led to maximum increase in FTHX capacity of 20%, and maximum decrease in refrigerant-side pressure drop of 88.6%. Based on simulation results, it is concluded that additional coil face area is required to match both capacity and refrigerant pressure drop, compared with R410A, this is demonstrated with two proposed FTHX designs. One design prioritizes increased FTHX capacity, and the other a reduction in refrigerant pressure drop. All these results culminated in design guidelines for HFOs that suggest it will be challenging to achieve both the same capacity and pressure drop characteristics as R410A without modifications to FTHX size. [ABSTRACT FROM AUTHOR]

• Validated simulation model for a new compination air conditioning systems were presented. • Two different integration cases were presented according to the air condtioning system used. • Energy and Exergy analysis of new compination systems were studied under two different climates. • A reduction in CO 2 emissions was observed when using the proposed ssystems. This paper introduces novel modification for conventional air conditioning systems through utilizing a thermal ice storage system integrated with solar panels. Alexandria and Aswan, cities in Egypt, are chosen to represent two climates for hot-humid and hot-dry climates respectively. Exergy analysis is performed for the proposed solar-ice thermal storage system based on transient analysis. Results showed that, the proposed system is more effective approach in hot-humid than hot-dry climate and more efficient with all-water system than with all-air system. The maximum energy saving is 205.16 GJ having a percent of 27.5% in August for all water system in case of Alexandria city and 224.67 GJ with a percent of 25.38% in August for all-water system in case of Aswan city. All air system simulation showed maximum energy saving of 175.05 GJ with a percent of 18.13 % in case of August for Alexandria and 175.45 GJ having a percentage of 17.43% in case of Aswan in August. Moreover, the all-water system achieved a reduction in CO 2 emissions by 467 tons/year in Aswan city and 390 tons/year in case of Alexandria city. These reductions decrease to be 435 and 353 tons/year when the all-air system used for the same two cities. [ABSTRACT FROM AUTHOR]

The advance of air-conditioning systems has become a popular topic, due to its huge energy consumption and the increasing demand of improving indoor air quality. Although various approaches have been proposed for humidity, temperature and CO 2 control, their coordination has not yet been studied. In this study, the technologies of desiccant dehumidification, indirect evaporative cooling and direct CO 2 capture are innovatively integrated in an air-conditioning system, by which their respective advantages can be exerted and limitations can be compensated. Under a base working condition with ambient temperature of 35 °C and relative humidity of 80%, the overall coefficient of performance of the integrated system reaches 0.93, with an improvement of 53.3% against a conventional scheme. The integrated system is more efficient at higher crowdedness. With occupant number from 2 to 22 in a room, the advantage of the integrated system ranges from 50.7% to 85.6%. Parametric studies on different indoor and outdoor conditions are conducted, indicating that the energy efficiency advantage is more outstanding at higher indoor temperature, lower ambient temperature and lower ambient humidity. The factors of economic, environment and health are discussed, where the integrated system exhibits superiority against conventional systems and existing studies as well. Approaches are raised to improve the performance and promote future studies. The results in this paper contribute to providing a scheme for the integration of different technologies and enlightening insights for the advance of air-conditioning systems for the sake of air quality improvement, energy saving and emission reduction. • An integrated air-conditioning system is proposed for improving energy efficiency. • Different technologies for temperature, humidity and CO 2 control are coordinated. • 53.3% improvement on energy efficiency is obtained for base working condition. • Parametric analyses indicate advantage for the integrated system at most cases. • Economic and environmental issues are discussed compared with existing studies. [ABSTRACT FROM AUTHOR]

In this paper, the (Bi 2 O 3) 1–x–y (Tm 2 O 3) x (Yb 2 O 3) y ternary systems were successfully synthesized by the solid–state reaction method under air conditions. All powder compositions were then heat treated for 100 h at 750 °C to allow for partial substitution of dopant cations, Tm3+ and Yb3+, between host Bi3+ cations. Characterizations of fabricated compositions were carried out by XRD, TG and DTA, FPPT, and FE–SEM techniques. Stacked XRD patterns verified that all compositions included solely single–phase peaks, with the exception of Bi 0.92 Tm 0.04 Yb 0.04 O 1.5–δ and Bi 0.88 Tm 0.04 Yb 0.08 O 1.5–δ , whose patterns suggested mixed phases. The DTA curves, depending on temperature, detected the endothermic peaks at around 600 °C, implying that an order–disorder transition occurs in the anion sublattice of the doped crystal. At 700 °C, the conductivity of the Bi 0.88 Tm 0.08 Yb 0.04 O 1.5–δ system was found to be 0.432 S/cm, surpassing the conductivity of a single–doped (Bi 2 O 3) 0.80 (Er 2 O 3) 0.20 system, which had a value of 0.37 S/cm at the same temperature. • The cubic δ-phase with high ion conductivity became stable in the majority of fabricated compositions. • The magnified XRD patterns indicated a peak shift because of doping. • The DTA curves reveal the endothermic peaks at around 600 °C, signifying an order-disorder transition. • The highest conductivity is found to be 0.432 S/cm at 700 °C for the Bi 0.88 Tm 0.08 Yb 0.04 O 1.5–δ composition. • The order-disorder transition is noticeable on the Arrhenius plots at around 600 °C. [ABSTRACT FROM AUTHOR]

The conventional air conditioning system used in high-speed railways has limitations in heating performance and environmental impact, necessitating the exploration of alternative refrigerants. The transcritical CO 2 system has gained popularity due to its exceptional heating efficiency and environmental benefits. This study aims to evaluate the energy and environmental potentials for transcritical CO 2 systems in high-speed trains based on four-vertical-and-four-horizontal railway lines within different climatic regions of China. A high-fidelity transcritical CO 2 system model was first developed and validated through experiments. Then, a comprehensive energy and environmental evaluation method was proposed and applied to the four-vertical-and-four-horizontal railway lines. The results indicated that the transcritical CO 2 system had a superior heating performance and competitive cooling performance based on daily and annual operations. Furthermore, the transcritical CO 2 system exhibited significant environmental advantages with lower total life cycle climate performance for all lines, with an average emissions reduction ratio of 17.6% and a maximum emissions reduction ratio of 26.98%. These findings highlight the competitive energy performance and outstanding environmental benefits offered by transcritical CO 2 systems as promising alternatives to air conditioning systems in railway transportation. • This paper evaluates the potential of theCO 2 system in high-speed trains from an energy performance and environmental benefits perspective. • A high-fidelity model of the transcritical CO 2 system is developed and validated for effectiveness through experiments. • The energy and environmental evaluations are conducted based on China's four-vertical-and- four-horizontal railway lines. • The results indicate that the CO 2 system presents a competitive alternative for air conditioning systems in high-speed trains. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mathematical modeling of membrane distillation considering concentration polarization. • Integration of membrane distillation into a liquid desiccant air conditioning system. • The hybrid system driven by solar energy with a batch-wise operation. • Feasibility analysis of the hybrid system in a hot and humid climate area. • System performance evaluation in terms of air dehumidification and water production. Membrane distillation (MD) is a promising method for liquid desiccant (LD) regeneration as it can mitigate LD carryover and produce freshwater as a by-product. Previous research on MD regeneration was mainly focused on performance evaluation and optimization of the regenerator itself. This paper proposed a hybrid solar-driven direct contact MD (DCMD) regeneration-assisted liquid desiccant air conditioning (LDAC) system for air dehumidification, cooling, and freshwater production. A mathematical model for the DCMD regenerator was first developed by considering both temperature and concentration polarizations. This model was validated against the experimental data in terms of the outlet channel temperature and LD solution concentration in the feed tank with relative deviations of ± 9.8 % and ± 0.5 %, respectively. The DCMD model was further integrated into an LDAC system with a batch-wise operation. To investigate the technical feasibility of the proposed system, a one-week simulation was conducted in a residential house during summer in a tropical climate area of Australia. The results showed that the latent heat load was effectively removed from the process air and the regenerated liquid desiccant solution can meet the dehumidification requirement with a concentration over 30.0 wt%. The dehumidification rate and regeneration rate were at 0.49–1.25 kg/h and 0.95–4.25 kg/h, respectively. Solar energy contributed to 52 %-78 % of the total system thermal energy consumption. Furthermore, this system can produce 11.0–12.8 kg of water daily. [ABSTRACT FROM AUTHOR]