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With global cooling demand increasing, there is a need for refrigeration cycles that use low global warming potential (GWP) refrigerants. Researchers have flirted with the idea of using the Brayton cycle for refrigeration over the years, but it has yet to prove competitive in performance or cost when compared to the widely used vapor compression cycle. The recent development of an electrochemical Brayton refrigeration cycle has renewed interest in the thermodynamics of Brayton refrigeration. This work provides a parametric study of the COP of a Brayton cycle air conditioner (either mechanical or electrochemical in nature) as a function of the characteristics of the cycle components (thermal conductances and isentropic efficiencies). When the isentropic efficiencies of the adiabatic components (i.e., the compressor and turbine in the mechanical Brayton cycle) are 90 %, the cycle COP is limited to a value of ∼1. Furthermore, a thermodynamic comparison to the vapor compression cycle reveals that the Brayton refrigeration cycle generates ∼8 × more entropy, and that the thermodynamic favorability of the vapor compression cycle is due to the presence of phase change. [ABSTRACT FROM AUTHOR]

Solar thermochemical hydrogen production is a promising pathway for producing sustainable fuels and chemicals. One of the main challenges in the development of these processes is their low steam conversion extent, dictated by its restrictive thermodynamics requiring extremely high temperatures over 1500 °C and low oxygen partial pressure to obtain a steam conversion over 10%. While condensing the unreacted steam is technically simple, the latent heat is thus rendered useless for the process. In many cases, this lost heat can be larger than the higher heating value of the produced hydrogen. We propose a new separation method based on a mechanical vapor recompression cycle, enabling the recovery of the latent heat by compressing the steam–hydrogen mixture prior to the condensation process, thus creating a temperature difference between the hot exhaust and cold inlet streams. We show that this separation method can recover the latent heat and keep its quality in relevant operating conditions while requiring less than 14% of the recovered heat for compression work, resulting in a coefficient of performance over 7. This method increases the viability of solar thermochemical hydrogen production cycles, especially under limited steam conversion conditions. • A new method for hydrogen–steam separation based on mechanical vapor recompression. • Coefficient of performance can achieve value over 10 for low steam conversion cases. • At higher conversion additional heat is needed to complete the boiling of the fresh steam. • Applications in solar thermochemical hydrogen production can increase overall system efficiency. [ABSTRACT FROM AUTHOR]

While forced-air convective systems remain the predominant method for heating and cooling worldwide, radiant cooling and heating systems are emerging as a more efficient alternative. Current radiant cooling systems primarily rely on hydronic chilled water systems. This study introduces direct-expansion radiant cooling as a novel technique that could enhance the efficiency of radiant cooling and reduce its environmental impact. Water (R-718) has been tested as a refrigerant due to its favorable thermodynamic properties and environmental advantages; however, to the author's knowledge, it has yet to be tested in direct-expansion radiant cooling. This research investigated several refrigerants, including water (R-718), ammonia (R-717), R-410a, R-32, R-134a, and R-1234yf, for this application. The findings indicate that water demonstrates efficiency comparable to other non-natural refrigerants, making it a promising candidate, given its favorable thermodynamic properties and substantial environmental benefits. Despite challenges such as a high compression ratio necessitating multi-stage compression, a high compressor discharge temperature exceeding 300 °C and requiring specialized blade materials, and a high suction volume flow rate, direct-expansion radiant cooling operates within a different temperature range. Consequently, the compressor discharge temperature can be reduced to 176 °C, and the compression ratio can be lowered to approximately 3.5, making water a more viable refrigerant option for this application. [ABSTRACT FROM AUTHOR]

Refrigerants are used as working fluids in the heating and cooling industry. In order to prevent environmental issues such as greenhouse gas emissions and global warming, which are on the rise due to increasing environmental problems worldwide, the use of environmentally harmful fluids is tried to be reduced. In this study, the theoretical analysis of a vapor compression refrigeration system using alternative refrigerants instead of R404A, which has a high global warming potential (GWP), was carried out using the Engineering Equation Solver (EES) program. R454A, R454C, R455A, R457A and R459B refrigerants with low GWP were used in the vapor compression refrigeration system. The thermodynamic properties of the refrigerants were obtained from REFROP software. As a result of the analysis, the highest coefficient of performance (COP) value was found to be 8.03 in the system operating with R457A refrigerant when the condenser temperature was 30°C and the evaporator temperature was 5°C. Under the same conditions, the COP value was found to be 7.94 in the system operating with R404A refrigerant. The highest exergy efficiency was found to be 0.59 in the system operating with R457A refrigerant when the condenser temperature was 30°C and the evaporator temperature was -5°C. Under the same conditions, the exergy efficiency was found to be 0.58 in the system operating with R404A refrigerant. The highest exergy destruction was observed in the evaporator of the cooling system. As a result, it was determined that R457A is one of the most suitable alternative refrigerants that can be used instead of R404A in terms of both GWP and COP and exergy efficiency. [ABSTRACT FROM AUTHOR]

Nowadays, refrigerated food storage and transport vehicles are very common. However, with regard to the engine of vehicles, a significant amount of heat is discharged into the environment in the form of exhaust gas and jacket water. If the cooling system is used to convert this waste heat into cooling capacity, the thermal efficiency of the engine will be improved to a certain extent. Therefore, this paper uses two waste heat recovery jet refrigeration systems to recover heat from the exhaust gas and jacket water of the refrigerated vehicle. One is a conventional jet refrigeration system that uses only engine exhaust as the heat source, and the other is a system that adds a preheater upstream of the generator based on the conventional system, using engine jacket water to preheat the working fluid. This paper presents the results of comparing the impact of R141b/R123, R141b/R245fa, R142b/R134a, and R142b/R152a working fluids on system performance, and considers the effects of operating temperature and secondary flow pressure drop in the ejector receiving chamber on the system performance. The research results indicate that of the four selected working fluids, the R141b/R245fa (0.4/0.6) blend has the best overall performance. After the addition of a preheater, the system using R142b/R134a (0.6/0.4) hybrid working fluid achieves the maximum cooling capacity of 16.0994 kW and the maximum thermal efficiency of 5.45%, and the exergy loss in the generator is 1 kW lower than without the preheater. [ABSTRACT FROM AUTHOR]

This study presents a thermodynamic analysis of a solar-driven vapor compression refrigeration (VCR) system designed for use in the region of Ghardaïa (Southern Algeria) which is located in a desert with a semi-arid climate where the demand for cooling is high, and the solar radiation is abundant. Two working fluids are tested and compared, the HFC high GWP going to phased out, R134a and the low GWP, HFO refrigerant recently introduced R1234ze. The performance of the solar VCR system was evaluated using a numerical model developed in MATLAB software, based on thermodynamic properties of R1234ze and R134a refrigerants. The results showed that coefficient of performance (COP) and thermodynamic efficiency of the solar VCR system increased with decreasing ambient temperature due to the increase in the compressor power consumption. The COP during the 21st day of July month is obtained in the range of 4.37-5.77 for R1234ze refrigerant which are close and more than 90% of the maximum COP value, while it is in the range of 2.56-3.17 for R134a fluid. The lowest COP values are found around noon hours during 12:00 AM and 15:00 PM. In addition, the greatest amount of the PV power production for R134a and R1234ze refrigerants occurs in the middle of the day (12:00 PM) as 2.8 and 1.6 kWh, respectively. [ABSTRACT FROM AUTHOR]

Refrigeration and air conditioning systems are essential in residential, commercial, and industrial segments. The data acquisition and the control of equipment results in an improvement in efficiency and a decrease in energy consumption, considering that the data obtained bring a better visualization and understanding of the components of the system. This work aims to automate data acquisition from a vapor compression refrigeration workbench by developing a low-cost data acquisition system. The system was developed using Arduino and LabView with the assistance of LINX software. After the communication between the controller and the program, six thermocouples were installed on the refrigeration workbench to acquire the temperatures in the program of the data acquisition system. For reading system pressure values, a camera was used to capture images from six analog pressure gauges. From reading these data, the pressure-enthalpy diagram of the thermodynamic cycle was obtained. The experimental refrigeration workbench has been used in teaching and research activities. The data acquisition system developed for the refrigeration workbench improved the realization of experiments, allowing a better comparison between experimental and theoretical results. [ABSTRACT FROM AUTHOR]

The use of refrigerants used in most refrigeration systems in use today has been or will be banned soon. Therefore, it is extremely important to search for alternative refrigerants. In this study, the thermodynamic properties of R471A, a very new refrigerant with low global warming potential, were estimated using a data mining approach. The results obtained from the data mining were compared with the actual data obtained from the REFROP program. The correlation coefficients (R2) for the saturation liquid enthalpy (hf), saturation vapor enthalpy (hg), saturation fluid entropy (sf), saturation vapor entropy (sg), superheated vapor enthalpy (hsh), superheated vapor entropy (ssh) have been found 0.9999, 0.9997, 1, 0.9884, 0.9992, and 0.9601, respectively. In addition, compared the hf, hg, sf, sg, hsh, and ssh values with the values calculated using the data mining and the actual values, and the percent error values. It was seen that the values calculated from the obtained formulations and the actual values are in good agreement. This study shows that the data mining approach can be successfully applied to determine enthalpy and entropy values for any temperature and pressure of R471A refrigerant. Thus, the determination of the thermodynamic properties of refrigerants and the simulation of vapor compression refrigeration systems become quite easy. [ABSTRACT FROM AUTHOR]

Copyright of ESPOCH Congresses: The Ecuadorian Journal of S.T.E.A.M. is the property of Knowledge E DMCC and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The main objective of this study is to describe the teaching experience in an applied thermodynamics course, using MATLAB applications developed with MATLAB® App Designer. This course is compulsory for students in their sophomore year of the BSc in Chemical Engineering. MATLAB applications are developed to serve as tools for the teaching of thermodynamic cycles: steam and gas power, and vapor‐compression refrigeration cycles. The computer applications are case‐based problem generators, that is, based on chosen groups of initial variables, which values are randomly selected each time the MATLAB applications are run. Solutions of the cycle problems, which include thermodynamic cycles plotted in p–h, T–s, and p–v diagrams, and thermodynamic properties of each state of the cycle, are shown when students want to check their calculations. Moreover, the applications allow exporting initial data and solutions to an MS Excel file. The usability and learning experience of the applications were evaluated through anonymous surveys to students and the feedback of the academic staff involved in the course. The main problem, that the students referred, to was the utilization of the MATLAB applications that they considered it was not straightforward. The students believed that the utilization of these computer applications represented a significant improvement in teaching (70%) and expressed their interest in having similar materials in other degree courses (75%). After implementing the computer applications, the academic results showed an increase of ca. 16% in the pass rate. [ABSTRACT FROM AUTHOR]

R-1132a is increasingly being considered as a low global warming potential component in alternative mixtures to R-23 in specialized low temperature and ultra-low temperature refrigeration systems. Though the thermodynamic properties of R-1132a were investigated in several studies up to 2018, reinvestigations have been carried out in recent years. In order to contribute toward these renewed measurements, the critical parameters of R-1132a were experimentally re-determined. Thirty-two vapor pressures from 240 K to the critical temperature, fifteen saturated vapor and six saturated liquid densities above 254 K and the PvT properties in both the vapor phase (98 points) and liquid phase (34 points) from densities of 50 kg·m−3 to 760 kg·m−3 were also measured. Specific correlations for each of these properties were optimized and compared to previously available data from the literature. Additionally, the Peng–Robinson equation of state was used to represent the aforementioned properties and further utilized to determine the enthalpy and entropy of R-1132a. [ABSTRACT FROM AUTHOR]

Cooling refrigeration systems ingest prime energy and contribute to universal negative impact due to ecologically unfavorable working fluids used. Hence, the quest to improve the performance of Vapour Compression Refrigeration System (VCRS) with more efficient and eco-friendly refrigerant such as nanoparticles becomes imperative. In this study, performance analysis of hybrid nanofluids-zeotropic mixtures in a VCRS were experimentally investigated to determine the best operating optimum performance using exergy based approach. To achieve this, varying concentrated mixtures were selected using ternary graph. The results revealed that all the designated ratios of the mixed refrigerant with different fractions achieved good performance improvement with optimum values obtained at (011) zero gram of TiO2, 7.5g-Al2O3/CuO. All the selected hybrid mixtures led to an improved outcome in terms of Coefficient of Performance (COP), less power consumption and high performance exergetic efficiency, with COP values ranging from 0.31% to 3.10% and exergetic efficiency from 0.32 to 1.43%. The value for thermal conductivity, dynamic viscosity, density and specific heat were found to be highest (0.0958 W/m.K; 0.00164 W/m.K; 686.82 kg/m³ and 359.82 kJ/kg.K) at the same concentration of zero grams TiO2 in the mixture. Comparison made from the performance characteristics curve (with global parameters) indicated that maximum power coefficient and cooling capacity for the various concentrations were found at (001) 7.5g-TiO2, zero grams Al2O3/CuO equal to 2.2 kW, and the minimum value at concentration of 5 was 0.61% at (111) 5g-TiO2/Al2O3/CuO, and 0.87% for (121). An increase was observed in the maximum power coefficient, cooling capacity and COP increased by 13.51%, 5.78% and 10.33%. It was also observed that hybrid nanofluid-zeotropic refrigerant worked seamlessly with VRCS, making it a sustainable, green and clean as well as eco-friendly alternative with near-zero to zero negative effects on public health safety and environment. [ABSTRACT FROM AUTHOR]

In the analysis of vapor compression refrigeration systems, simple and effective mathematical formulas are required to determine the thermodynamic properties of refrigerants. This study aims to determine the thermodynamic properties such as enthalpy, entropy, and specific volume of environmentally friendly new-generation refrigerants (R515B and R450A) with low global warming potential using gene expression programming (GEP). The thermodynamic properties calculated using the formulations obtained from the GEP model and the actual thermodynamic properties obtained from the REFROP software were compared. Performance evaluation criteria such as R2, root mean square error, and mean absolute percent error are in the range of 0.86 to 0.999, 0.0000285–6.489, and 0.0009–0.35, respectively, and these values are acceptable. This study offers simple and efficient formulations to calculate the thermodynamic properties of new-generation refrigerants without the need for any software. So, the simulation of cooling and heat pump systems will be greatly facilitated. [ABSTRACT FROM AUTHOR]

• CYCLE_D-HX: vapor-compression cycle model w/ thermodynamic & transport properties. • CYCLE_D-HX: screen refrigerants & design systems w/ tube-based forced-convection HX. • Tests with R-134a, R-410A, R-513A, R-450A, Tern-1, R-1234yf, R-32, R-452B, R-454B. • COP and volumetric capacity predicted within 3%; for basic cycle. • Low-GWP refrigerants evaluated using simulations w/ optimized HXs and compressor. CYCLE_D-HX is a semi-theoretical model that simulates the performance of a vapor-compression cycle with forced-convection heat exchangers for specified temperature profiles of the heat source and heat sink. In this study, we validated CYCLE_D-HX using experimental measurements from a small (< 4 kW capacity) heat pump test apparatus operated in cooling mode. The tested refrigerants included the medium-pressure refrigerant R-134a and candidate replacements with a lower global-warming potential (GWP): R-513A, R-450A, Tern-1 (R-134a/1234yf/1234ze(E) 49.2/33.8/17.0 mass fraction,%), R-515B, and R-1234yf. We also tested high-pressure refrigerant R-410A and candidate replacements with lower-GWP: R-32, R-452B, and R-454B. The model generally agreed with experimental results, with COP and volumetric capacity overpredicted by (0 – 3)% for the basic cycle, and by (0 – 5)% for the cycle with the liquid-line/suction-line heat exchanger (LLSL-HX). We applied the model to evaluate the performance of the refrigerants in a system with optimized refrigerant circuitries in the evaporator and condenser. The simulations showed the lower-GWP medium-pressure refrigerants, including some non-flammable blends, had COP (0.2 – 2.3)% less than R-134a. The lower-GWP high-pressure refrigerants, which all have the '2L' flammability rating, had COP (2.3 – 3.2)% higher than R-410A. [Display omitted] [ABSTRACT FROM AUTHOR]

Combining fresh material drying/cooling and environment regulation of residential buildings, a new integrated energy supply (IES) system based on heat pump is proposed to improve the energy efficiency, comfort of living condition and retention rate of agricultural products in rural areas. To balance supply and demand, the IES system, based on the characteristics of energy utilization in rural areas, is able to operate among four basic modes: Building Heating (BH), Building Cooling (BC), Material Drying (MD), Material Cooling (MC), and two integrated modes: BHMC and BCMD. Under typical working conditions, thermal performances including cooling capacity, heating capacity, compressor input power and coefficient of performance (COP) are compared among different operation modes when refrigerants are R32, R152a, R22 and R1234yf, respectively. It can be found that integrated energy supply system have lower cooling and heating capacity, and higher compressor power, but its COP is also the biggest. Comparison results also show that the time ratio of integrated operation mode (t r) and time ratio of one operation mode (t s) are important factors effecting the entire energy efficiency. • An IES system is used to supply energy for living and produce processing in rural areas. • Performance are simulated for six running modes with four different refrigerants. • Much Higher COP can be got in integrated modes than in one-purpose ones. [ABSTRACT FROM AUTHOR]

High-temperature heat pumps (HTHPs) provide a promising approach to reducing CO 2 emissions in industrial heating applications. However, developing large-scale, high-temperature-output, and large temperature-lift heat pumps that utilize low-GWP refrigerants remains a challenge. Natural working fluids, particularly water, show potential due to their exceptional thermodynamic properties and environmental friendliness. Our findings indicate that by employing water as a refrigerant, high-temperature heat pumps can achieve a significant temperature lift of up to 100 °C while maintaining a satisfactory coefficient of performance (COP). Additionally, these systems demonstrate high flexibility, enabling them to operate as closed-cycles, hybrid closed and open cycles, or hybrid vapor compression and absorption systems. Furthermore, we identify feasible matching strategies for industrial high-temperature heat pumps, focusing on working fluids, components, and cycle structures, with variables such as compressor type, heating temperature, and capacity. Through this research, we highlight the unique performance advantages of water across a 100 °C temperature range and propose detailed design sketches centered on water, capable of achieving large temperature lifts and high-temperature outputs. These include compression cycles, absorption cycles, and mechanical vapor compression cycles, with particular attention to closed and open cycle combinations. Moreover, we emphasize the research gap in current industrial heat pump technologies, providing a forward-looking technological perspective on heat pumps as a key component in further industrial decarbonization. • Offered matching strategies for industrial heat pumps, varying compressor, temperature, and capacity. •Evaluated low-GWP refrigerants, highlighting benefits of natural fluids, especially water. •Presented water-based designs for large temp lift and high output, including combined cycles. •Identified research gaps and provides tech perspectives for industrial heat pump. [ABSTRACT FROM AUTHOR]

An overview of low global warming potential (GWP) refrigerants focused on R-513A, and other low GWP refrigerants such as R-1234yf, R-1234ze(E), R-290, and R-152a which are considered as potential replacement (drop-in/retrofit) of R-134a in heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems is presented in this study. The present comprehensive review analyzes the associated energy consumption, exergy analysis, coefficient of performance (COP), energy efficiency ratio (EER), and heat transfer performance (including convective boiling/condensation, and nucleate pool boiling). Analysis of the existing studies reveals that R-513A, R-1234yf, R-1234ze(E), R-152a, and R-290 may replace the R-134a in the HVAC&R systems depending on the configuration of the systems/applications and types of components such as compressor, evaporator, condenser, expansion valve, etc. For instance, energy consumption, exergy analysis, efficiency ratio, and COP of the cooling/heating systems mainly depends on the types of compressors and evaporators (followed by expansion valve and condenser) along with thermodynamic and transport properties of the alternative refrigerants. Hence, some HVAC&R systems (such as centrifugal compressors) require modifications in their configuration and components upon direct replacement with R-513A while some systems may not require due to comparable performances (either higher or lower) such as for small vapor compression refrigeration systems with reciprocating/twin compressors due to differences in thermophysical properties. [ABSTRACT FROM AUTHOR]

Copyright of Dokuz Eylul University Muhendislik Faculty of Engineering Journal of Science & Engineering / Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi is the property of Dokuz Eylul Universitesi Muhendislik Fakultesi Fen ve Muhendislik Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

High pressure miniature air compressor plays an irreplaceable role in some areas such as refrigeration and pneumatic ejection in the fighter. But, as a lot of heat is produced during compression, the cooling system consumes relatively more energy and its volume and weight even exceeds the compressor itself. So, how to design cooling system becomes the key factor. A novel self-air-cooling reciprocating compressor (SACRC) is first proposed in this paper, which can continuously cool the compressor through ingenious structural design without any auxiliary equipment. The SACRC's model is established considering of thermal dynamics and heat exchange characteristics of all the units, which regards the spiral groove in the cooling system as a chamber with compressibility and heat exchange. The characteristics of SACRC are studied by comparative simulation and experiment validation with traditional reciprocating compressor (TRC). The research results showed that the volumetric efficiency and temperature characteristics of SACRC are both improved significantly especially at high output pressure and long working time, which is pioneering significance to further improve the miniaturization of high pressure compressor. [ABSTRACT FROM AUTHOR]

Nowadays about 20% of the worldwide energy consumption is attributable to refrigeration almost based on vapor compression. In the scientific literature in the class of the ecofriendly cooling technologies alternative to vapour compression there is solid state cooling. In this field, the scientific community has devoted the attention specifically toward elastocaloric refrigeration. Elastocaloric refrigeration is based on the latent heat associated with the transformation process of the martensitic phase, found in Shape Memory Alloys (SMA) when they are subjected to uniaxial stress cycles of loading and unloading. SMAs are characterized by the mechanical property of being able to return to the initial form once the uniaxial stress has been removed. By exploiting this effect in a reverse regenerative thermodynamic cycle called Active elastocaloric regenerative refrigeration cycle (AeR), a satisfactory cooling effect is achievable. In this paper, the results of a numerical investigation conducted, through a 2-D model, on a single bunch of elastocaloric elements are shown. Specifically, the heat transfer and the energy performances are studied both by varying the geometrical parameters of the elements and by varying the auxiliary fluid (air) velocity. [ABSTRACT FROM AUTHOR]

The high global warming potential of current refrigerants in cooling equipment based on the vapor-compression cycle has triggered a major effort to find and implement more environmentally benign alternatives. Here, we review the basics of the vapor-compression cycle together with the safety, environmental, and thermodynamic constraints that have led to the current and next generation of refrigerants. The development of new fluids has focused on fluorinated olefins, known as hydrofluoroolefins (HFOs), and blends that contain HFOs. Many of these are slightly flammable, presenting trade-offs between safety and environmental considerations. Engineers also have options with a resurgence of the “natural refrigerants” (ammonia, carbon dioxide, propane, and isobutane). Innovative system designs that reduce the required quantity of refrigerant may allow a wider choice of refrigerants. [ABSTRACT FROM AUTHOR]

In this study, COP and heat capacities of evaporator and condenser were calculated by artificial intelligence and machine learning method in a vapor compression mechanical refrigeration cycle using well-known R134a as a refrigerant. Dataset was obtained with CoolPack software to train the model. Evaporating, condensing, superheating and subcooling temperatures are selected as input data. COP, heat capacities of evaporator and condenser are included in the dataset as target values. Artificial Neural Network (ANN) model was created with Matlab R2018b software and validated with target data. The output files obtained were compared with the target files and it was found that the mean square error value was quite close to one. The results of this study show that the ANN method can be used to obtain cycle parameters in one stage refrigeration cycle with high accuracy. [ABSTRACT FROM AUTHOR]

In this work, the UMR-PRU model is extended to refrigerant mixtures. Key properties of pure refrigerants, such as vapor pressure, saturated volume, heat capacity and enthalpy of vaporization are examined with the Peng-Robinson equation of state, to which UMR-PRU reverts for pure components, and appropriate modifications to the attractive and repulsive terms are made. For the extension of UMR-PRU to refrigerant mixtures, four new UNIFAC groups are introduced and binary UNIFAC interaction parameters are fitted to experimental vapor-liquid equilibrium data. The predictive capability of the model is tested in ternary refrigerant mixtures. A comparison is made between UMR-PRU and the REFPROP model, which is currently considered as the state-of-the-art model for refrigerants. The results reveal that UMR-PRU describes the vapor-liquid equilibrium of refrigerant mixtures with similar accuracy as REFPROP. Both models are also employed for performing process simulations of vapor compression refrigeration cycles, yielding very comparable results regarding the COP and mass flowrate of the working fluid. [ABSTRACT FROM AUTHOR]

Efficient cooling of the trans-critical CO 2 vapor compression cycle to improve system performance is a crucial research topic. This paper proposes an innovative approach called distribution compression (DC) to achieve the same effect as subcooling in a trans-critical CO 2 thermodynamic cycle. In the DC system, the trans-critical CO 2 at the gas cooler outlet is no longer further cooled but subjected to a secondary pressure boost and releases heat in ordinary heat sink conditions as in the gas cooler. Thermodynamics calculated the change in performance of the DC system under different working conditions with different secondary boost ratios. The optimal secondary boost ratio related to evaporation and gas cooler outlet temperatures under optimal discharge pressure based on the baseline system was obtained. The results show that compared with the baseline system, the DC system can effectively improve the system performance, and the maximum refrigeration COP increase is between 8.2 % ∼ 10.76 %, and the maximum heating COP increase is between 5.37 % ∼ 6.34 %. The cooling or heating capacity increase can reach up to about 26 %. The ideal secondary boost ratio in a DC system is not highly demanding, and the increased input power for the second input power for the secondary boost will not exceed 20 % relative to the baseline system. Comparing the COP of the DC system over current systems that only use a single subcooling technology still shows advantages. The DC system provides a new idea to improve the performance of the trans-critical CO 2 vapor compression cycle. [ABSTRACT FROM AUTHOR]

This paper deals with the thermodynamic processes governing an Oscillating Water Column (OWC) device, focusing on the entropy variation and the energy and heat budgets over the expansion–compression cycles. The influence of the thermodynamic performance on the Levelized Cost of Energy (LCOE) and the carbon footprint is analysed. The research deals with an experimental research on a simple OWC off-shore model for the purpose, with the open gas system inside the chamber formulated by a real gas model, and conceptually represented by an equivalent closed one in order to apply the First Principle of Thermodynamics appropriately. Analysed results show that the compression process is an active process, while the expansion process is a passive one. In addition, the observed non-adiabatic performance of the complete cycle implies a efficiency reduction, with consequences on the LCOE. Furthermore, an approach to emergy (embodied energy) analysis is considered, providing with concluding remarks on OWC renewability and possible impacts on the biosphere and GHG emissions. An utter approach on OWC energy and emergy assessment will be develop on future researches. • The air expansion/compression process can be considered as cyclic since Δ U = Δ S = 0. • The cyclic process can be divided in an active compression and a passive expansion. • Enthalpy and exergy variation indicates the useful and wasted energy obtained. • The heat exchange reduces the efficiency and increases the LCOE. • Emergy analysis shows a similar renewability than other renewable sources. [ABSTRACT FROM AUTHOR]

This study aims to comparatively investigate the performance of a cascaded vapor compression absorption refrigeration system (CVCARS) operated with different refrigerants such as R1234yf, R134a, R717 and R290 in vapor compression cycle. Two design objectives are considered for performance evaluations. Total annual cost is the first design objective which includes investment and operational cost along with the social cost associated with carbon emissions. Exergy efficiency is the second considered objective which is related to thermodynamic issues. These problem objectives are individually and concurrently optimized by means of Artifical Cooperative Search metaheuristic algorithm and best results are compared for each cycle configuration. Single objective optimization results reveal that CVCARS working with R717 in vapor compression cycle has the lowest total annual cost whereas the maximum second law efficiency is obtained by the refrigeration system operated with R290 in vapor compression cycle. Following that, multi objective optimization is applied to acquire the Pareto optimal solutions which are nondominated to each other and no solution between them prevails over the other. Reputed decision making method TOPSIS is applied to choose the final best answer among the Pareto curve. It is seen that solution found by TOPSIS is skewed towards the minimum total annual cost and second law efficiency for each cycle configuration. Sensitivity analysis is then put into practice to observe the influences of variations of decision variables on design objectives as well as performance coefficients of the different cycles in the refrigeration system. [ABSTRACT FROM AUTHOR]

Abstract The need for more energy efficient heating and cooling technologies will increase over the coming decades. Climatic concerns associated with greenhouse gas emissions as well as energy costs associated with powering heating and cooling systems necessitate more efficient systems. This work presents an alternative to traditional vapor compression cycles used for heating and cooling. The chemical looping heat pump system is an indirect chemical heat pump that utilizes the possibility of condensation after a chemical reaction to allow the working fluid's compression to take place in the liquid phase. A thermodynamic model of the cycle is developed using electrochemical cells as the reaction drivers of the cycle. Sensitivity analysis is used to identify the most critical components of the system. The chemical looping heat pump may provide a potential COP increase of over 20% when compared to traditional vapor compression systems for representative device efficiencies. [ABSTRACT FROM AUTHOR]

According to day-by-day consumption increase, energy high costs and nonrenewable energy destroying effects, clean technologies such as fuel cells lead a remarkable decline in consumption. In the present study, waste heat recovery from a hybrid system of an 1180 kW low-temperature polymer electrolyte membrane fuel cell and a vapor compression refrigeration cycle is surveyed using a recuperative organic Rankine cycle. The fuel cell system is equipped with a metal hydride storage. The heat absorbed from stack is divided into two streams. One stream flows into the recuperative organic Rankine cycle to produce power, and the other goes for waste heat recovery of the refrigeration cycle condenser; then, it is utilized for other components of fuel cell system including metal hydride to release hydrogen and H2 preheater to preheat the hydrogen to the stack temperature. Effects of operational parameters including fuel cell thermal efficiency, cooling load, pressure ratio, mass flow rate and working fluid of recuperative organic Rankine cycle were thermodynamically analyzed. Two working fluids were surveyed including R-245fa and R-134a. Results indicate that hybrid system thermal efficiency falls down by increase in turbine pressure ratio. The maximum system consumption power was dedicated in the case in which the fuel cell has its highest thermal efficiency in addition to minimum net produced power. Additionally, R-134a was determined as the best working fluid. Net output power and efficiency of the system with R-134a are about 1.2 and 20% more than R-245fa, respectively. [ABSTRACT FROM AUTHOR]

With great requirements of ice in handling, storage, and supply of food products, it is significant to investigate the operation performance of ice making machine and improve the efficiency of refrigeration system. This paper presents an experimental investigation on a vapor compression refrigeration cycle with a subcooler applied in an ice-making machine. A multichannel evaporator is selected to generate ice cubes. To investigate the basic operation performance of refrigeration system in an ice-making machine, the fluid temperature distribution in multichannel evaporating coils and the dynamic variation in each cooling loop are measured in detail with a multichannel data acquisition instrument. Moreover, the ice generating and thawing phases are investigated. Parts of main conclusions are arrived at based on the analysis of the collection data. Meanwhile, some potential operational issues are also detected. To improve the operation performance of the ice machine, some suggestions and improvements are proposed. [ABSTRACT FROM AUTHOR]

In this study, cooling performance of a refrigeration system under the effects of nanoparticle (TiO2) addition to the compressor oil (poly alkaline glycol (PAG)) was experimentally investigated. Thermodynamics analysis of the vapor-compression refrigeration system with various nanoparticle volume fractions of TiO2 (between 0.5%, and 1%) added to the compressor oil was performed. R-134a was used as the refrigerant. Twostep method was used to prepare the nano-lubricant for different solid particle volume fractions. It was observed that COP of the refrigeration system enhances with the addition of nanoparticles and it is an increasing function of nanoparticle volume fraction. [ABSTRACT FROM AUTHOR]

Highlights • The self-heat reception technology was applied to heterogeneous distillation. • The vapor compression system was optimized to reduce energy consumption. • The heat exchanger network was used to design the heat integration. • The HAD-SHRT process can reduce energy consumption and cost effectively. Abstract Azeotropic distillation is one of the most energy intensive processes and widely used to separate thermos-sensitive azeotropes. In this work, several heterogeneous azeotropic distillation processes based on the vapor recompression heat pump (VRHP) and self-heat recuperation technology (SHRT) are proposed to study the energy-saving performance. The results show that the heterogeneous azeotropic distillation process based on self-heat recuperation technology (HAD-SHRT) has better performance in economic and environment. In HAD-SHRT process, the sensible heat and latent heat of the vapor streams are recuperated and supplied to the reboilers. The remaining sensible heat is supplied to the preheaters through the heat exchanger network (HEN). Adding a preheater can reduce the duty of compressor by increasing the initial temperature of the stream. Compared with the conventional heterogeneous distillation process, the HAD-SHRT process can save 38.50% of TAC, 93.30% of CO 2 emissions, and 80.92% of energy consumption. The thermodynamic efficiency can increase to 13.51%. [ABSTRACT FROM AUTHOR]

Abstract The dew point evaporative cooler has been proposed to replace the mechanical vapor compression chiller in air sensible cooling, for its significantly larger energy efficiency and simpler system layout. Many of the existing studies focused on applying a first-law thermodynamic analysis to the dew point evaporative cooler, however, its performance involving the second-law thermodynamic assessment remains unclear. Therefore, in this paper, an exergy analysis of the counter-flow dew point evaporative cooler is conducted. The exergy performance of the dew point evaporative cooling process is examined by incorporating the first law of thermodynamics for energy and mass balances. A counter-flow dew point evaporative cooler prototype has been designed, fabricated and tested to investigate its cooling performance. A 2-D computational fluid dynamics (CFD) model is then formulated to simulate the flow, temperature and humidity fields of the cooler. The model agrees well with the acquired experimental data with the maximum discrepancy of ±5.6%. The exergy flow, efficiency and efficiency ratio of the cooler are discussed under various simulation conditions. Key findings that emerged from this study reveal that the saturated air state at ambient temperature is the rational dead state to properly describe the physical mechanisms involved in the dew point evaporative cooling process. The exergy efficiency ratio of the dew point evaporative cooler is greater than 1.0, highlighting a remarkable second-law efficiency for air conditioning applications. Highlights • An in-depth exergy analysis is carried out for the dew point evaporative cooling. • A counter-flow dew point evaporative cooler is developed and investigated. • A 2-D CFD model is derived for the first- and second-law thermodynamic analysis. • The selection of an appropriate dead state is judiciously discussed. • The exergy performance of the cooler is investigated under different conditions. [ABSTRACT FROM AUTHOR]

The present study investigates the theoretical thermodynamic performance analysis and flammability study of various new ozone friendly refrigerants as replacements to R22. In this work, five non azeotropic refrigerant blends comprising of R152a, R134a, R32, R290 and R1270, at various compositions were developed. Flammability study of all the five refrigerant mixtures considered were carried out by using Refrigerant Flammability (RF) number. The cycle followed during the performance investigation of refrigerants was the actual vapour compression refrigeration cycle. Thermodynamic performance characteristics of all the five investigated refrigerants were compared with the baseline refrigerant R22. Theoretical results showed that COP of refrigerant M40 was 0.51% higher, compared to R22 and the five refrigerants studied. Compressor discharge temperature of M40 was lowered by 11.6°C compared to R22. Power consumed to produce per ton of refrigeration of M40 was 0.52% lower, compared to R22 and the five refrigerants considered. Heat transfer rate through the condenser for M40 was 3.66% higher than R22. Volumetric refrigeration capacity of M40 was the highest among the five studied refrigerants and it was very close to the volumetric capacity of R22. Flammability analysis revealed that all the five investigated refrigerant mixtures were classified into the weakly flammable category. Overall, the thermodynamic performance of new ternary blend M40 (R32/R134a/R1270 5/60/35 by mass percentage) was higher than R22 with reasonable saving in power consumption and hence, M40 is a viable candidate to replace R22. [ABSTRACT FROM AUTHOR]

In this study, the energy parameters (i.e., cooling capacity and COP) were theoretically investigated for three different vapour compression refrigeration system (basic cycle, basic cycle with liquid-to-suction heat exchanger and two-stage cascade cycle) for which R1234yf, R1234ze(E), R513A, R445A and R450A alternative refrigerants with low GWP value were used instead of R134a. The studied refrigerants demonstrated similar thermodynamic behaviour. The exergetic efficiency of the systems was also compared. The comparison of the energy parameters was carried out for two different evaporation temperatures (-30 and 0°C) and two condensing temperatures (40 and 55°C). According to the calculation results, R450A which almost has the same COP values as R134a comes into prominence with 58% lower GWP value compared to R134a. Among the studied refrigeration cycles, system with LSHEX can be suggested for providing a better effect in terms of COP for the considered refrigerants and temperature cases as well as assumed system parameters. It was seen for the investigated cycles that the highest exergetic efficiency could be obtained in the case of R445A. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a theoretical thermodynamic analysis of a novel Ejector Enhanced Vapor Compression Refrigeration (EEVCR) cycle using zeotropic mixture of propane and isobutane (R290/R600a) as a refrigerant to replace R134a in domestic refrigerators/freezers. 1 D thermodynamic model for a constant area mixing ejector is used to estimate the cycle performance under the condition of optimal operating regime. The Coefficient of Performance (COP), the Volumetric Cooling Capacity (VCC), Q v and the compressor pressure ratio are studied for the novel EEVCR cycle and the results are compared to the conventional cycle using pure fluid R134a and zeotropic mixture R290/R600a. A comparative study was carried out to determine the propane mass fraction, z in the zeotropic mixture that would be a suitable replacement for R134a. The results indicated that the cycle COP and Q v could be improved by 23% and 62.71%, respectively. In addition, the cycle COP and Q v for the proposed EEVCR cycle were higher by 70% than those for a modified ejector expansion cycle. Finally, the propane mass fraction of 60% in the zeotropic R290/R600a mixture was found to have similar saturation pressure as R134a and the cycle COP and Q v were found similar to those of R134a. Highlights • An EEVCR for dual evaporator refrigeration systems using zeotropic mixture is studied. • Energy analysis of EEVCR cycle is theoretically conducted and compared with the conventional cycle. • A comparative study of the cycle parameters is performed. • The COP and Q v of the cycle can be improved by 24% and 63%, respectively. • The R290/R600a mixture with 60% propane is a good replacement for R134a in EEVCR. [ABSTRACT FROM AUTHOR]

Caloric refrigeration can be a viable alternative to the traditional vapour compression technology since a caloric solid refrigerant has zero vapour pressure and therefore is ecological with no direct Ozone Depletion Potential and zero direct Global Warming Potential. Caloric refrigeration embraces four main cooling techniques, each one based on a different caloric effect. This paper is focused upon materials that display mechanocaloric properties, with a transition induced through the application of variable pressure (barocaloric cooling) or uniaxial stress (elastocaloric cooling). Materials that display solidstate caloric effects driven by applied pressure/stress could lead to more accessible and economic technological solutions. By means of a two-dimensional mathematical model an energy analysis is performed with the most performing elastocaloric and barocaloric materials to explore the potential of mechanocaloric cooling. Temperature span, cooling power and coefficient of performance have bene evaluated. Results demonstrate best mechanocaloric materials, like Cu68.13Zn15.74Al16.14 and (NH4)2MoO2F4, provide energy performances better than those of traditional vapour compression plants. [ABSTRACT FROM AUTHOR]

Controlling the pressure of a propellant tank while minimizing the propellant mass loss is the primary technical demand of cryogen storage missions in the reduced gravity environment in space. Thermodynamic vent system (TVS) has been considered as a potential solution for this issue. Before conducting studies on TVS-equipped cryogen storage technology in space and on the ground, a TVS unit at room temperature with refrigerant R141b as the substituting phase-changing fluid was designed and tested. The performance of the TVS was evaluated at different combinations of the operation parameters including the fill level (35%, 50%, 65%), heat load (74.7 W, 108.8 W, 148.4 W), and control strategies. Mass loss, which is an unavoidable result of tank pressure control, was quantitatively compared between the TVS method and the direct gas vent method over a given period of time. Taking the heat load of 74.7 W as an example, the results showed that the mass loss can be reduced by as much as 79.3%. Assuming the vented stream contains 40% mass fraction of liquid if vented directly at zero-gravity, TVS can not only control the tank pressure within a designated range but also significantly help to reduce the mass loss. [ABSTRACT FROM AUTHOR]

The need for more efficient and sustainable refrigeration systems has promoted the development of new configurations. Subcooling have shown to improve the coefficient of performance whereas thermal energy driven configurations allow renewable sources to be employed. In this study thermodynamic models have been developed for simple, suction line heat exchanger, integrated and dedicated subcooling vapor compression systems using R-134a as the primary refrigerant and for a single-stage absorption refrigeration system with H20/LiBr. The variation exhibited by the performance of the refrigeration systems is examined at various operating conditions finding that COP increases as condenser temperature decreases and evaporator temperature increases; high COP values are obtained with increasing generator temperature and LiBr concentration in the case of the absorption system. Low and zero emissions associated to subcooling strategies and absorption systems, due to the higher efficiencies and renewable character of the energy source respectively, were obtained when comparing the environmental impact. [ABSTRACT FROM AUTHOR]

The present work aims to perform the thermodynamic analysis of an ejector expansion refrigeration cycle (EERC) with a constant-pressure two phase flow ejector and to present the effect of primary nozzle throat diameter on cooling capacity of the EERC. The refrigerant is R134a. In order to achieve these objectives, a computational program is developed using EES software to simulate the system. Mathematical modeling of EERC and applied computational procedure are reported in detail. Operation under critical mode is favorable in ejector operation in terms of high entrainment ratio and enhanced ejector performance. As a result, in this present study, ejector of the refrigeration cycle operates under critical conditions and normal shock occurs at the end of the constant area mixing section. Not an iteration process but Henry and Fauske model is applied to determine the physical properties of the fluid under critical conditions. [ABSTRACT FROM AUTHOR]

The exergy analysis of a process to quantify the irreversibilities is advantageous over the entropy analysis in that it provides the definition of efficiency of a process, referred to as exergetic efficiency (defined as the ratio of exergy recovered to exergy supplied to the process). Unfortunately, the exergy analysis of practical multi-unit cyclic processes is rarely covered adequately in the undergraduate courses in engineering thermodynamics. In this article, the quantification of irreversibilities is illustrated in detail for a practical cyclic steam power plant using exergy analysis and Gouy-Stodola theorem. The efficiencies are determined for the various components and for the whole process. The theoretical background related to exergy, exergy analysis, and Gouy-Stodola theorem is also covered briefly for the benefit of the students. An assessment problem dealing with vapor-compression refrigeration cycle is included at the end in order to assess the intended learning outcomes of this article. The key solution steps along with answers are also provided for the benefit of the readers. As exergy analysis involves advanced level concepts in thermodynamics, the appropriate place for the introduction of the material presented in this article is the second, advanced level, course in thermodynamics. [ABSTRACT FROM AUTHOR]

Air conditioning approach using two separate units for latent heat and sensible heat removal opens up opportunities and challenges for improved efficiency. In such systems, the dehumidification device removes moisture from the air stream usually without condensation whilst the remaining sensible load is handled by a conventional mechanical vapour compression (MVC) machine. This article investigates the thermodynamic feasibility of such hybrid dehumidifier + MVC systems as potential replacements for the conventional MVC devices. We shed some light on the minimum efficacy requirement in terms of COP or simply the breakeven COP for the coupled dehumidification system. Thermodynamic investigation has been conducted using classical Carnot, endoreversible technique and the experimental approaches. The breakeven COPs for a dehumidifier + MVC system where the latter using HFC-R14a, HFC-R32 and HFO-R1234yf as refrigerants have been investigated at assorted outdoor air ratios. Performance enhancement in terms of COP and the cooling capacity at elevated temperatures for sensible cooling are accounted for. It is observed that the breakeven COP for the dehumidification system ranges from 9 to 17 (Carnot approach) and 4.3 to 6.8 (Ideal cycle) in order to be realistically competitive with the current efficiency offered by a MVC system for the both dehumidification and sensible cooling. The life cycle cost (LCC) analysis is further performed to assess the fresh air-handling systems using a conventional MVC system and a dehumidifier + MVC system. The unprecedented improvement in the performance of the MVC systems further raises the ceiling for the breakeven COP of the dehumidification systems. [ABSTRACT FROM AUTHOR]

This paper presents thermodynamic and thermoeconomic analyses as well as optimization of a re-compression supercritical CO 2 cycle. A gas turbine cycle (GT) is adapted as a model to an existing plant to generate additional power in Gaziantep Municipal Solid Waste Power Plant (GMSWPP). The total capital cost rate and total cost rate of the GT cycle are found to be 20.47 $/h and 77.14 $/h, respectively utilizing SPECO by using the exhaust gas of 16 kg/s with 1.9 bar and 566.7 °c. The net power, the energy and exergy efficiencies, the total cost and the total capital cost rates of the GT cycle are optimized by +1.73%, +3.21%, +2.45%, −1.11% and −1.64%, respectively using NSGA-II in MATLAB in the range of 2.5 ≤ P R ≤ 4 , 200 ≤ P 6 ≤ 216 , 16 ≤ T 0 ≤ 23 and 9.1 ≤ L M T D ≤ 12.9 . This paper provides an originality such that optimization as well as thermodynamic and thermoeconomic analyses is performed simultaneously for an existing MSW power plant, which can be stressed that there are scarce amounts of studies related on this field. Moreover, as another novelty, it can be emphasized that net power output of such like plants which have similar capacity can be improved using the developed model and NSGA-II optimization method. [ABSTRACT FROM AUTHOR]

Due to the reason of water injection, twin screw water vapor compressor can realize higher pressure ratio and saturated temperature lift of compressed vapor. Its application in mechanical vapor compression (MVC) heat pump systems has drawn much attention recently because of the great energy-saving potential and reliability. In this paper, a thermodynamic model of the working process in water injected twin screw water vapor compressor is established, in which heat and mass transfer between water liquid and vapor are considered. Its accuracy is validated by the experimental recorded p – V indicator diagrams. With the proposed model, the compressor performance is simulated and studied. According to the simulation results, water injection can increase the volumetric efficiency 5% and adiabatic indication efficiency 6%. Once the discharged vapor has been cooled to saturation, the shaft power of the compressor will increase while the adiabatic indication efficiency and the volume flow rate together with the volumetric efficiency change little with the continuous increase of injected water. Since the sensible heat of water is much smaller than latent heat, the temperature of injected water has little effect on the performance. Both the volume flow rate and shaft power increase linearly with the rotor speed. In addition, the volume flow rate of injected water should be adjusted with the regulation of rotor speed to guarantee a saturate discharge temperature. The volumetric efficiency will increase and the adiabatic indication efficiency will decrease slowly with the rise of rotor speed. Due to the cooling and evaporation effects of liquid water at the discharge chamber, the adiabatic indication efficiency does not decline when it operates at under compression condition. Water injection can greatly improve the compressor performance when the compressor operates at under compression or over compression condition, especially where a high saturated temperature lift of compressed vapor is in demand. [ABSTRACT FROM AUTHOR]

The amount of improvement of the cooling output from the subcooling power has not been adequately studied by thermodynamics, and the corresponding trend has still not been realized. Therefore, this paper contributes to the understanding of the thermodynamic relationship of the subcooling power and increase of the cooling capacity. The parameter RICOSP, defined as the ratio of the rise in the cooling output to the subcooling power, is employed as the critical indicator and its expression is derived. A vapour compression chiller with subcooling is simulated to analyse RICOSP under different working conditions. It is shown that the subcooling power cannot be fully transformed into an increase of the cooling output as the speed of compressor, inlet temperature and flow rate of cooling water as well as chilled water for the chiller with the subcooling is identical to that for the system without the subcooling. Additionally, the dependence of RICOSP on the speed of the compressor, as well as on the flow rate of cooling water and chilled water, is strong. RICOSP increases by 17.4% and 8% when the speed of compressor and flow rate of cooling water are reduced by 80%, respectively. RICOSP decreases by 22.5% when the flow rate of chilled water is reduced by 80%. However, RICOSP is nearly independent of the inlet temperature of cooling water and chilled water. This paper deepens the understanding of a vapour compression chiller with subcooling. [ABSTRACT FROM AUTHOR]

In recent years, liquid desiccant air-conditioning system (LDAC) has shown a great potential alternative to the conventional vapor compression systems. LDAC not only greatly improves the indoor air quality by controlling the humidity and temperature independently, but also deceases the electrical energy consumption of the conventional air conditioner. In this work, the liquid desiccant and humidification cycle is driven by the exhaust heat of the compressor. Cycle performance of a small-scale heat pump type air conditioner coupled with a liquid desiccant/humidification cycle has been theoretically and experimentally evaluated by the present study. Parametric analysis on cycle performance of the present cycle is carried out through both theoretical and experimental methods, and lithium chloride aqueous solution is used as the working fluid of the solution cycle. The thermodynamic analysis results show that while the evaporating temperature of the present cycle increases to 15 °C, the energy consumption decreases by about 22.64% when compared with conventional air conditioner. Theoretical results also indicate that the coefficient of performance (COP) of the novel system has a potential improvement of about 35.3%. Based on the theoretical results, experimental analyses of this novel cycle under summer and winter working conditions are carried out. In addition, comparison of the humidification and dehumidification ability as well as COP of the present novel system and the traditional one are carried out. Researching results of the present study provide important reference for investigator of this field. [ABSTRACT FROM AUTHOR]

This paper presents a study on the performance of irreversible vapour absorption refrigeration (VAR) system using finite time thermodynamic approach. The complete VAR system is considered to be consisting of two sub-systems; generator-absorber assembly and evaporator-condenser assembly. The former is assumed to be an irreversible heat engine cycle whereas the latter is assumed as an irreversible refrigeration cycle. The influence of rate of heat leak along with heat resistance and irreversibilities due to internal dissipation of the working fluid on performance of VAR system was also considered. This was accomplished by adding a heat leakage term into an irreversible model of VAR system. Overall coefficient of performance of the VAR system is optimised with respect to source/sink side heat exchanger areas using the Langrangian multiplier method. Furthermore, the effects of variations in the cycle parameters on performance deviation of the VAR system were studied using detailed numerical examples. The results from the presented study are useful for optimal design and performance improvement of absorption refrigeration cycles. [ABSTRACT FROM AUTHOR]

Recently, next-generation HVAC technologies have gained attention as potential alternatives to the conventional vapor-compression system (VCS) for dehumidification and cooling. Previous studies have primarily focused on analyzing a specific technology or its application to a particular climate. A comparison of these technologies is necessary to elucidate the reasons and conditions under which one technology might outperform the rest. In this study, we apply a uniform framework based on fundamental thermodynamic principles to assess and compare different HVAC technologies from an energy conversion standpoint. The thermodynamic least work of dehumidification and cooling is formally defined as a thermodynamic benchmark, while VCS performance is chosen as the industry benchmark against which other technologies, namely desiccant-based cooling system (DCS) and membrane-based cooling system (MCS), are compared. The effect of outdoor temperature and humidity on device performance is investigated, and key insights underlying the dehumidification and cooling process are elucidated. In spite of the great potential of DCS and MCS technologies, our results underscore the need for improved system-level design and integration if DCS or MCS are to compete with VCS. Our findings have significant implications for the design and operation of next-generation HVAC technologies and shed light on potential avenues to achieve higher efficiencies in dehumidification and cooling applications. [ABSTRACT FROM AUTHOR]