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In recent years, the global community has consistently advocated for the advancement of novel vapor compression refrigeration systems that utilize environmental friendly refrigerants, with the objective of phasing out systems that rely on non-ecological refrigerants. This system is extensively utilized in cooling technology which consumes a large amount of available energy as a compressor work. The researchers are aiming to minimize the compressor work and concurrently enhance cycle efficiency through the incorporation of nanoparticles characterized by enhanced thermo-physical attributes. This study presents the exergetic, economic, and environmental assessment of vapor compression test rig by employing different volume concentrations of graphene nanosheets (0.1 %, 0.15 %, 0.20 %, 0.25 %, and 0.3 %) dispersed in 200 ml of mineral oil charged with iso-butane (R600a) refrigerants (75 g, 100 g, and 125 g). The pull-down test, environmental assessment based on total equivalent warming impact, thermo-economic evaluation, relative irreversibility exergy efficiency, and the total plant cost rate (C˙ total) were assessed. A comparable methodology was employed to analyze the total exergy loss. The results revealed that the system utilizing R600a/GNs exhibits superior energy, exergy, environmental, and economic performance compared to pure R600a/Mineral oil. The actual COP and exergy efficiency improved up-to 12.16 % and 23.65 % respectively. In addition, the total equivalent warming impact and exergy loss reduced by 3.67 % and 16.17 % respectively. Lastly, the running cost rate was the most significant, accounting for over 74.87 % of the C˙ total value. In contrast, the penalty cost rate due to CO 2 emissions was the least significant, representing less than 2.69 % of the C˙ total value. [ABSTRACT FROM AUTHOR]

The increasing demand for sustainable energy solutions has spurred significant interest in cogeneration technologies. This study introduces a novel integrated organic Rankine cycle (ORC) and vapor compression cycle (VCC) system, specifically designed to enhance energy efficiency and reduce greenhouse gas emissions in industrial applications and district heating systems. The key innovation lies in the development of an advanced coupling mechanism that seamlessly connects the ORC and VCC, enabling more efficient utilization of low-grade heat sources. By optimizing working fluid selection and implementing a shared shaft connection between the ORC turbine and VCC compressor, the system achieves dual functionality—simultaneous electricity generation and cooling—with higher efficiency than conventional methods. Thermodynamic analyses and experimental results demonstrate that the proposed ORC–VCC system can significantly reduce operational costs and decrease reliance on fossil fuels by leveraging renewable energy sources and industrial waste heat. Additionally, the study addresses integration challenges by introducing specialized components and a modular design approach that simplifies installation and maintenance. This innovative system not only enhances performance but also offers scalability for various industrial applications. By providing a detailed evaluation of the ORC–VCC integration and its practical implications, this work underscores the system's potential to contribute substantially to a sustainable energy transition. The findings offer valuable insights for future research and development, highlighting pathways to overcome existing barriers in cogeneration technologies. [ABSTRACT FROM AUTHOR]

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]

This study proposes a modification to the two-stage cascade vapor compression refrigeration system by adding internal heat exchangers that function as subcoolers and desuperheater. The influence of each internal heat exchanger proposed on the exergy destruction rate, exergy efficiency, compressor power consumption, ECOP, and COP of the system was investigated. Additionally, various refrigerant combinations were considered as working fluids to evaluate which combination is the most suitable for the proposed system. Mathematical models based on the principles of thermodynamics were established in Engineering Equation Solver (EES), a software used for energy and exergy analysis. The results reveal that the addition of specific internal heat exchangers causes either an increase or decrease in overall system performance, depending on the type of refrigerant combination used. Consequently, there exists an optimal system configuration for each refrigerant combination. Compared with the conventional two-stage cascade refrigeration system, the optimal system configurations in the present study exhibited higher overall system performance. A maximum increase in exergy efficiency, ECOP, and COP of 7.31 %, 9.8 %, and 7.3 %, respectively, can be observed with the refrigerant combination R450A/R404A. Additionally, the results of the exergy analysis identify that the HTC compressor, condenser, LTC compressor, and cascade condenser are the primary contributors to the exergy destruction rate within the system. [ABSTRACT FROM AUTHOR]

• A discharge side oil separator was used to separate oil from refrigerant flow. • Mass flow rates leaving the oil and vapor outlet ports of separator were corrected. • True refrigerant and oil mass flow rates obtained were used to calculate O C R. • O C R from oil separator-based approach shown to be within 6 % of sampling results. • Separation efficiencies cannot be the only metrics for oil separator performance. Oil circulation ratio (O C R) is defined as the ratio of the mass flow rate of oil to the total mass flow rate of refrigerant-oil mixture in a vapor compression system. The standard method for measuring O C R uses liquid line sampling as described in ASHRAE Standard 41.4. Sampling is tedious, alters the steady state operation of the system, depends on different parameters, and only applies to miscible refrigerant-oil pairs. A potential method for measuring real-time O C R is by using an oil separator to separate the refrigerant flow from the oil flow and using the individual flow rates to calculate O C R. Neither a liquid line, nor refrigerant-oil miscibility are necessary for this separation-based method. No oil separator is perfect as some oil always escapes with the separated refrigerant, and some refrigerant, dissolved in oil, always escapes with the separated oil. This can significantly reduce the accuracy of the procedure. The present study investigates O C R measurements using an oil separator-based approach for a full vapor compression cycle working with R134a and PAG ISO 46 oil. A full cycle allows sampling to also be performed in parallel for validation. Mass flow corrections were performed to account for refrigerant dissolved in separated oil, and for oil entrained by separated refrigerant. O C R values from the oil separator-based approach, upon mass flow correction, were within 6 % of the sampling results. The usefulness of the oil separation efficiencies at the oil and vapor outlet ports for the oil separator-based approach is discussed. [ABSTRACT FROM AUTHOR]

This study proposes a cogeneration system for the simultaneous production of cooling and freshwater. A double-stage cascade compression cooling system consists of two interconnected vapor compression cycles. The proposed system integrates a double-stage cascade compression cooling system with a water desalination unit, which takes advantage of the heat released by the cascade system. The system performance was evaluated using various refrigerants selected based on their energy efficiency, environmental impact, and widespread use. Multiple combinations of the fluids were used in the high-temperature cycle (HTC) and low-temperature cycle (LTC) to analyze their impact on system performance. A parametric analysis was conducted by developing a mathematical model in MATLAB. The model's input parameters were the evaporation temperature and the temperature difference between the inlet and discharge of both compressors (ΔLTC and ΔHTC). System performance was assessed from a first-law point of view through the coefficient of performance (COP), the energy utilization factor (EUF), and the gain output ratio (GOR). The results revealed that the maximum (105 °C) and minimum (−13 °C) temperatures, essential for desalination and cooling, respectively, were achieved using R134a in the LTC and R123 in the HTC, with ΔLTC = 65 °C and ΔHTC = 70 °C. However, the best performance was observed with R123 in both cycles, with ΔLTC = 45 °C and ΔHTC = 70 °C. This configuration achieved a COP of 1.06, a GOR of 1.61, and an EUF of 2.74. [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]

Mechanocaloric cooling/heat pumping with zero carbon emission and high efficiency shows great potential for replacing traditional refrigeration with vapor compression. Mechanocaloric prototypes that are developed using shape memory alloys (SMAs) face the problems of a large driving force and high cost. In this work, we report a low-crystalline thermoplastic polyetherurethane (TPU) elastomer fiber with a low actuation force and good mechanocaloric performance. We fabricate the TPU fiber and develop a multifunctional mechanical tester to measure both the elastocaloric and twistocaloric effects. In the experiments, the applied stress required to induce mechanocaloric effects of the TPU fiber is only 10~30 MPa, which is much lower than that of widely used NiTi elastocaloric SMAs (600~1200 MPa). The TPU fiber produces a maximum twistocaloric adiabatic temperature change of 10.2 K, which is 78.9% larger than its elastocaloric effect of 5.7 K. The wide-angle X-ray scattering (WAXS) results show that the strain-induced amorphous chain alignment and associated configurational entropy change are the main causes of the good mechanocaloric effects of the TPU fiber, rather than the strain-induced crystallization. This work demonstrates the potential of achieving low-force heat-efficient mechanocaloric cooling using thermoplastic elastomer fibers. [ABSTRACT FROM AUTHOR]

In this paper, we present the development of a gray-box model for unitary air conditioning equipment that can be trained with as little as 5 data points with higher accuracy on test data. The model utilizes the same model inputs as is typical in building energy simulation, and is accurate. While black-box models require large data sets to deliver accurate results, white-box models require higher computational and engineering efforts along with detailed knowledge of the system, and are often difficult to obtain. The model presented here addresses a hybrid solution that is a steady-state, component-based, gray-box model that requires inputs from the source and sink fluids and rated performance of the specific piece of equipment, only. The basic physics of a vapor compression cycle are captured in individual component models for the heat exchangers, compressor, and expansion valve. These components are generalized to eliminate refrigerant-side inputs. A key addition is the development of correlations for the overall heat transfer coefficient times surface area (UA) obtained from Symbolic Regression (SR). The model successfully predicts the cooling capacity, coefficient of performance (COP), and sensible heat ratio (SHR) for three state-of-the-art variable speed, split-system, air conditioning systems with capacities of 12.3(3.5), 14(4), and 17.6(5) kW(tons), achieving a mean absolute percentage error (MAPE) of less than 3.4%. These results suggest that the gray-box model can be useful in predicting the performance of similar systems in the future, which could be valuable for energy management and optimization purposes. • Development of a component-based gray-box model of a unitary air conditioner using symbolic regression. • Genetic algorithm used to formulate overall heat transfer coefficient correlation. • The model exhibits robustness and generalization, even with minimal training data. • Novel model utilizes only ambient temperatures and operational inputs, facilitating seamless integration into existing BEMs. [ABSTRACT FROM AUTHOR]

• The dynamic model for VCRS based on the Switched Moving-Boundary method is built. • The impact of environmental disturbances on the refrigeration performance is studied. • A hybrid paradigm combining online identification and adaptive control is proposed. • The overshoot performance is optimized at 10–4 magnitude in uncertain environments. • Adaptive control's IAE by 2–3 orders of magnitude compared to traditional control. Vapor compression refrigeration systems (VCRS) occupy a crucial position in modern society and in the field of thermal sciences. However, the operation of VCRS is subjected to both external disturbances (dynamic-changing environment) and inherent system characteristics (coupling or nonlinear features), leading to issues like reduced refrigeration efficiency and significant fluctuations in cooling capacity. To address these challenges and enhance the adaptability of VCRS in dynamically changing environments, this study establishes a dynamic simulation model for VCRS based on the Switched Moving-Boundary method. The impact of external environmental disturbances on refrigeration performance is investigated, and continuous online identification methods are employed to elucidate its internal coupling characteristics and nonlinear features. The adaptive temperature control method is introduced, benefiting from the developed recursive least squares method with a forgetting factor for online identification, achieving precise model identification which facilities the real-time parameters tuning of adaptive controller. The results indicate that the hybrid paradigm of online identification and adaptive control algorithm not only effectively handles various disturbances but also reduces overshoot and IAE by 2–3 orders of magnitude compared to traditional PID controllers. Adaptive PID control maintains overshoot in the 10–4 order of magnitude and IAE in the 10–5 order of magnitude. [Display omitted] [ABSTRACT FROM AUTHOR]

The editorial in the journal "Entropy" discusses the importance of thermodynamic optimization in industrial energy systems to reduce energy consumption and environmental impact. Various techniques like heat integration and exergy analysis are used to enhance system performance. The editorial highlights research articles focusing on optimizing polygeneration systems, bio-energy with carbon capture and storage, biomass-based combined cycles, and waste heat management in different industrial processes. These studies aim to improve energy efficiency, reduce emissions, and promote sustainable energy practices. [Extracted from the article]

In light of the intensifying global climate crisis and the increasing demand for efficient electricity and cooling systems, the exploration of advanced power generation technologies has become crucial. This paper presents a comprehensive analysis of Organic Rankine Cycle–Vapor Compression Cycle (ORC-VCC) systems utilizing low-grade waste heat for the dual purpose of electricity and cooling production. The study focuses on systems that harness waste heat below 90 °C with thermal inputs up to 500 kW. An in-house Python code was developed to calculate cycle parameters and perform multi-objective optimization targeting the maximization of both ORC-VCC efficiency and power output. The optimization was conducted for 10 different cases by evaluating five working fluids across two different ambient temperatures. The analysis reveals that the optimized system achieved an impressive overall cycle efficiency exceeding 90%, demonstrating the significant potential of ORC-VCC technology in waste heat recovery applications. The Non-Dominated Sorting Genetic Algorithm II (NSGA-II) multi-objective optimization approach was found to be particularly effective at navigating the multi-dimensional solution space and identifying the global optimum. This study provides valuable insights into system performance across a range of operating conditions and design parameters. Sensitivity analyses highlight key factors influencing cycle efficiency and power output. These findings have important implications for the development and deployment of ORC-VCC systems as a sustainable and efficient solution to meet growing energy needs while reducing greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

The increasing global demand for energy-efficient cooling systems, combined with the need to reduce greenhouse gas emissions, has led to growing interest in using low-GWP (global warming potential) refrigerants. This study conducts a multi-objective optimization of a small-scale organic Rankine cycle–vapor compression cycle (ORC-VCC) system, utilizing refrigerants R1233zd, R1244yd, and R1336mzz, both individually and in combination within ORC and VCC systems. The optimization was performed for nine distinct cases, with the goals of maximizing the coefficient of performance (COP), maximizing cooling power, and minimizing the pressure ratio in the compressor to enhance efficiency, cooling capacity, and mechanical reliability. The optimization employed the Non-dominated Sorting Genetic Algorithm III (NSGA-III), a robust multi-objective optimization technique that is well-suited for exploring complex, non-linear solution spaces. This approach effectively navigated trade-offs between competing objectives and identified optimal system configurations. Using this multi-objective approach, the system achieved a COP of 0.57, a pressure ratio around 3, and a cooling capacity exceeding 33 kW under the specified boundary conditions, leading to improved mechanical reliability, system simplicity, and longevity. Additionally, the system was optimized for operation with a cooling water temperature of 25 °C, reflecting realistic conditions for contemporary cooling applications. [ABSTRACT FROM AUTHOR]

A novel heat-driven ejector refrigeration machine for an onboard air-conditioning system of a merchant ship was conceptualized and analyzed. The source of waste heat is low-pressure steam from the exhaust gas boiler (0.5-0.7 MPa). However, the steam from auxiliary boilers is used in port. It was proposed to include a thermal energy storage unit in the ejector refrigeration machine design to reduce fuel consumption by auxiliary boilers in the port. A phase change material with a melting point of 142 °C was proposed for use as thermal energy storage material. It was admitted for the TES unit to replace half of the generator load for 1 day of operation. For such conditions the volume and mass of the thermal energy storage unit were 16.5 tons and 125 m3 at an ejector refrigeration machine cooling capacity of 174 kW. It was shown that ejector refrigeration machine with thermal energy storage unit inherent the lower fuel consumption for its operation compared to the vapor-compression refrigeration machine: 53916 vs. 80567 kg of fuel per year. It is advisable to use the proposed ejector refrigeration machine with a thermal energy storage unit on ships that have short voyages and frequent stays in port. The problems in the TES unit design that need to be studied further have been noted in the paper. [ABSTRACT FROM AUTHOR]

• The evaluation of refrigeration systems due to the presence of malfunctions in their components was conducted through thermoeconomic methodology. • This methodology used splits physical exergy into its thermal and mechanical terms, in addition to using the fictitious term of negentropy. • A prognosis of system behaviour was derived, enabling utilization in maintenance scheduling and facilitating comprehensive energetic and exergetic analyses of both the refrigeration system and its individual components. In recent years, it has been possible to observe a significant expansion of the refrigeration and air conditioning industry. Considering that food refrigeration systems (blast chilling or freezing, cold storage, retail display, etc.) and air conditioners are large energy consumers, this work presents a methodology for evaluating the performance and behaviour of these systems using the thermoeconomic diagnosis concept. The thermoeconomic model used allowed the definition of the condenser and expansion device products, which is not trivial for these components. With that, the thermoeconomic diagnosis was used to evaluate the degradation of refrigeration system components, together with the influence of individual component degradations on efficiency, cooling capacity, operating parameters, and power consumption of the whole system. Through this analysis, a prognosis of system behaviour was obtained, which can be used for maintenance scheduling, as well as for the comprehensive energetic and exergetic analysis of a refrigeration system and each of its components. [ABSTRACT FROM AUTHOR]

Magnetic refrigeration based on magnetocaloric effect (MCE) has become a promising cooling technology to replace the traditional vapor compression refrigeration. However, traditional methods for searching MCE materials require producing many different compositions, causing unbearable workload and long experimental periods. Here, 3D printed La0.7Ce0.3Fe11.65Si1.35–Fe compositionally gradient alloys (CGAs) are successfully prepared using laser powder bed fusion equipped with a powder hopper with dual‐bin structure. This CGAs accelerate the high‐throughput screening for the best composition of La(Fe, Si)13/Fe with both high MCE and mechanical properties. The good interfacial compatibility between brittle 1:13 phase and reinforcing α‐Fe improves the mechanical properties significantly. Even after hydrogenation, the compressive strength and ultimate strain of the La(Fe, Si)13/Fe hydrides are ≈220% and ≈150% higher than those of stoichiometric La(Fe, Si)13. Meanwhile, the hydrogenated composite exhibits a large MCE under low magnetic field, e.g., the magnetic entropy change |ΔSM|max of 7.6 J kg−1 K−1 under 2 T is 52% higher than that of the benchmark Gd (5.0 J kg−1 K−1). Furthermore, this La(Fe, Si)13/Fe is 3D printed into various complex shapes suitable for heat exchangers. This study provides an innovative strategy for high‐throughput screening of new materials. [ABSTRACT FROM AUTHOR]

In this study, a validated mathematical model for a composite air conditioning system was established based on onsite test data. The system consists of a refrigerant pump driven two-phase cooling loop (RPTCL) and vapor compression refrigeration (VCR) cycles. The system can be switched to refrigerant pump (RP) mode, compressor mode, or hybrid mode, according to the outdoor temperature. By analyzing, the inadequacy of the existing Internet Data center (IDC) air conditioning system operation strategy was confirmed, and subsequently, five optimization strategies were proposed. The optimization strategies took two identical composite air conditioning systems as optimization unit, and under the premise of meeting the demand for cooling capacity, maximizing the operating time of RP and hybrid mode, which with higher energy efficiency, through complementary cooling capacity, to reduce the energy consumption. Meanwhile, when the cooling supply was higher than the demand, paired with optimization unit's ON/OFF ratio control, the unit's energy consumption was further reduced. The most optimization strategy provided 525.6 MWh of cooling energy to meet demand while consuming a minimum of 182.5 MWh. The optimization strategy also achieved a minimum of 12.1% and a maximum of 52.5% energy savings for IDCs in other climate zones of China. [ABSTRACT FROM AUTHOR]

Inadequate refrigerant charges can affect the vapor compression refrigeration systems' thermal and energy performance. To delve deeper into the subject, this study experimentally evaluated the performance of a domestic refrigerator operating at different refrigerant charges. Some of them simulate refrigerant leaks (70 and 80 g), and some others simulate an excess (100 and 110 g). Through a statistical analysis (Tukey test and control graphs), the temperature data with the greatest impact were analyzed, including the temperatures in the suction and in the compressor casing, the temperatures in the middle position and outlet of the condenser and evaporator, as well as the temperatures in the freezer. The operation of the refrigerator was affected to a greater extent when it worked with an overcharge of 110 g; here, the discharge pressure and the run time increased by 1.3 bar and 21%, respectively, compared to the conditions of the refrigerator operating with the reference charge (86 g). In addition, the excess charge also caused an increase in energy consumption of 0.56 kWh/day and a decrease in EER of 0.5 regarding the reference charge. Finally, the increase in energy consumption was projected to $0.03 USD per day with respect to the reference cost. [ABSTRACT FROM AUTHOR]

This research involves an experimental study of vapour compression refrigeration system (VCRS) with hybrid-nanofluids zeotropic blends of (23%-R32/25%-R125/52%-R134a) in the ratio of (0.03 - 0.15 %.Vol.) with elven samples as thus: 001, 010, 100, 011, 111, 211, 121, 112, 221, 212 and 122 gram). A morphology characterization test was conducted using scanning electron microscope (SEM) and X-ray Diffraction (XRD) amongst the selected ratios using compressor work efficiency, power consummation rate and Coefficient of performance (COP) as the core enhancement parameters. The most favorable blend produced the optimum COP in three different fraction ratios (011, 111 and112). The outcome indicated that thermo-physical and vapor compression properties of hybrid-nanofluids zeotropic (011) zero gram-TiO2, 7.5g-Al2O3/CuO; (112) 3.75 g-TiO2/Al2O3, 7.5 g-/CuO and (111) 5.0g-TiO2/Al2O3/CuO produced the best optimum performance of 3.1%, 1.41% and 1.21% respectively. The COP was found to be highest at (011) blend by about 3.1% at refrigerant temperature of -7 oC. The maximum compressor power coefficient, volumetric cooling capacity and TEGWI were found to increase by 13.51%, 5.78 % and 1.06 kg/sec CO2. The study also revealed that nanoparticles mixed in the base fluid increased the heat transfer coefficient even with a smaller particle portion of 0.003%, with optimum improvement of 0.0075 Vol % application. The calculated values of exergy destruction in each component at various % fractions are presented in Appendix I. Outcome of the study confirmed that hybrid-nanofluids zeotropic blend is energy efficient and environmentally friendly with good characteristics healthier than CFCs and HCFCs, and can offer healthier compressor/refrigerator working fluid substitute to be adopted in VCRS and air conditioning operations. [ABSTRACT FROM AUTHOR]

One of the promising approaches to compensate for imminent depletion of fossil energy resources and their adverse global impacts is enhancing the efficiency of systems utilizing low-temperature heat sources. The initial target of the research is to present a promising system for simultaneous production of power, refrigeration, heat, and hydrogen utilizing a combination of the absorption power cycle, the vapor compression refrigeration cycle, and a proton exchange membrane electrolyzer. On this subject, a comprehensive modeling of the energy and exergy of the proposed set-up is presented, and its thermodynamic performance is scrutinized. Furthermore, a comprehensive study of various parameters is performed to evaluate their impacts on system performance. The research aims to enhance and optimize the use of energy and various resources, contributing to the development of more sustainable efficient energy systems. Thermodynamic analysis of the multiple generation system shows that under baseline conditions and initial design, the system has the capability to produce net electrical power of approximately 17.12 kW, cooling power of about 201.5 kW, heating power of around 697.1 kW, and produce pure hydrogen at a rate of 0.153 kilograms per hour. The system exhibits an energy efficiency ratio of 1.364 and an exergy efficiency of 36.58 %. Moreover, optimization with single and multiple objectives with different weighting coefficients reveals that higher values of these parameters can be obtained. In other words, in the MOOM optimization mode, exergy efficiency increases to 7.16 %, and the energy performance ratio rises to 85.73 % compared to the BM mode. Additionally, through a parametric assessment to define the effect of input parameters on system performance, it demonstrates that increasing the temperature of the heat source may simultaneously increase the exergy efficiency and energy performance ratio of the system. The Grassmann diagram also indicates that the total exergy of the input fuel is about 196.9 kW. From this amount, approximately 121.5 kW are destroyed through the components of the system. Furthermore, about 3.39 kW are lost through the absorber coolant and waste from the hydrogen production unit. About 72.4 kW are attributed to products. [ABSTRACT FROM AUTHOR]

Air conditioning is vital for indoor comfort but traditionally relies on vapor compression systems, which raise electricity demand and carbon emissions. This study presents a novel thermo-mechanical vapor compression system that integrates an ejector with a conventional vapor compression cycle, incorporating a thermally driven second-stage compressor powered by solar energy. The goal is to reduce electricity consumption and enhance sustainability by leveraging renewable energy. A MATLAB® model was developed to analyze the energy and exergy performance using R1234yf refrigerant under steady-state conditions. This study compares four solar collectors—evacuated flat plate (EFPC), evacuated tube (ETC), basic flat plate (FPC), and compound parabolic (CPC) collectors—to identify the optimal configuration based on the collector area and costs. The results show a 31% reduction in mechanical compressor energy use and up to a 44% improvement in the coefficient of performance (COP) compared to conventional systems, with a condenser temperature of 65 °C, a thermal compression ratio of 0.8, and a heat source temperature of 150 °C. The evacuated flat plate collectors performed best, requiring 2 m2/kW of cooling capacity with a maximum exergy efficiency of 15% at 170 °C, while compound parabolic collectors offered the lowest initial costs. Overall, the proposed system shows significant potential for reducing energy costs and carbon emissions, particularly in hot climates. [ABSTRACT FROM AUTHOR]

Barocaloric cooling as an emerging cooling technology offers an eco‐friendly alternative to traditional vapor compression refrigeration. Research on barocaloric materials primarily concentrates on solid–solid phase change materials (PCMs), among which plastic crystals exhibit colossal barocaloric effect. Solid‐liquid PCMs such as paraffin also exhibit giant barocaloric effect, however, their potential is often overshadowed by leakage issues. In this work, a strategy is demonstrated by encapsulating solid‐liquid PCMs into porous carbon matrixes to generate a large family of colossal barocaloric materials. In practice, by orthogonally combining paraffins with encapsulation matrixes like graphene foam, carbon nanotube foam, and carbon foam, it can be obtained composites that work without leakage issues. The significant advantage is their colossal barocaloric effect with the highest entropy value up to 570 J K−1 kg−1 in paraffin‐20@graphene foam. Moreover, the composites possess thermal conductivity up to 89.9 W m−1 K−1 in paraffin‐20@carbon foam, and tunable working temperature in the range of 270—330 K. Most importantly, this strategy, demonstrated with 5 solid‐liquid PCMs and 3 encapsulation matrixes in this work, is just the beginning. Further exploration with more materials can develop a huge family of encapsulated solid‐liquid PCMs with colossal barocaloric performance for modern cooling technology. [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]

The current small passenger car vapor compression refrigeration systems use high global warming potential (GWP) refrigerants causing the greenhouse gas effect. In the present work, the low GWP of two pure refrigerants, R1234yf and R1234ze (E), and 16 blends of R134a, R1234yf, and R1234ze (E) are analyzed numerically. The experiments were conducted with R134a refrigerant to validate the numerical results. The experiments were conducted at the compressor speed of 600–1500 rpm and the condensing air at 30–40°C, relative humidity of 85%, and velocity of 1–3 m/s. The simulation and experimental results for R134a are deviated by a minimum of 10% and a maximum of 15%. It is found that the latent heat of vaporization of the two refrigerant mixtures with 80% R134a–20% R1234yf and the three refrigerant blends of 50% R134a–10% R1234yf–40% R1234ze (E) are the highest among 16 combinations. The other blends show a moderate difference of latent heat with R134a, but for maximum cooling capacity, the blends with 80% R134a–20% R1234yf and 50% R134a–10% R1234yf–40% R1234ze (E) are found to be more suitable for practical applications. [ABSTRACT FROM AUTHOR]

• Developed a dynamic model of a triple-evaporator domestic refrigerator/freezer. • Dynamic model validated within a 2 % deviation in average power consumption. • Implemented a two-stage economized cycle and its control scheme. • Achieved 12.9 % and 80 kWh/year reduction in power and energy consumption, respectively. • Estimated 18 TWh/year in global energy savings by 2030 with 10 % market penetration. Domestic refrigerator/freezers account for approximately 6 % of all energy consumption around the globe and mainly rely on vapor compression cycles to operate. Researchers have investigated alternative cycle architectures such as dual-loop cycles and parallel circuit cycles to improve their efficiencies. Despite the demonstrated energy saving potential of these advanced cycles, additional implementation costs are often not justifiable. However, to meet forthcoming stricter energy standards while ensuring flexible multi-temperature operation of domestic refrigerator/freezers, advanced cycle architectures are needed. In this paper, a state-of-the-art bypass circuit cycle triple-evaporator domestic refrigerator freezer with R-600a and a reciprocating compressor has been used as the baseline cycle investigate an alternative cycle configuration. Specifically, this work presents a two-stage vapor-injected cycle with a multi-evaporator system to enable energy savings and cost-effectiveness. The cycle establishes two separate evaporation temperatures to better match the cabinet temperature of fresh food and freezer compartment. The reduced difference between cabinet temperature and its evaporation temperature decreases the irreversibilities in the heat exchanger and improves overall system efficiency. Moreover, the addition of the economization line from the medium temperature evaporator reduces the compressor work. To capture the complex transient behavior of both the baseline system and proposed cycle architecture with their control strategies, a dynamic model has been developed and validated with experimental data. The validated dynamic model with the baseline cycle was modified to consider the two-stage vapor-injected cycle and its control logic, and simulation results yielded up to 13 % energy consumption reduction with respect to the baseline system. [ABSTRACT FROM AUTHOR]

• A compression-assisted absorption refrigeration cycle using R32/DMAC is developed. • Enable the implementation of solar absorption refrigeration in refrigerated warehouses. • Using 60∼80 °C solar hot water obtains a low evaporation temperature of −20∼0 °C. • There is an 18.2 % reduction in electricity consumption compared to traditional method. Solar absorption refrigeration technology is considered an ideal alternative to energy-intensive refrigerated warehouses due to its decarbonization and environmental friendliness. However, it faces challenges in competing with vapor compression refrigeration, such as high driving heat source temperature (>100 °C) and a long payback period. In this paper, we address these challenges by focusing on cycle structure and working pair, and propose a compression-assisted absorption refrigeration cycle (CARC) using R32/dimethylacetamide (DMAC) as working pair. The aim is to significantly reduce driving heat source temperature by adjusting absorption pressure utilizing an auxiliary compressor, enabling the cycle to be connected to low-cost and efficient non-concentrating solar collectors, thereby effectively shortening its payback period. This cycle includes two operating modes: CARC mode powered by solar energy during the daytime and vapor compression refrigeration cycle mode driven by off-peak electricity at night, ensuring 24-hour cooling capacity for refrigerated warehouses. The results indicate that this cycle can flexibly utilize 60∼80 °C solar hot water easily obtained as driving heat source and its evaporation temperature decreases to -20 °C. To assess its performance benefits, a compression-assisted absorption refrigeration system is developed and implemented. By utilizing the limited roof area of a refrigerated warehouse, it can achieve an 18.2 % reduction in electricity consumption and a 24.2 % reduction in carbon emissions compared to the vapor compression one annually. Additionally, during peak electricity demand periods in summer, the system exhibits significant energy-saving effects, and its payback period is about 4.2 years. Ultimately, this cycle provides a viable solution for energy-saving and emission reduction in refrigerated warehouses. [ABSTRACT FROM AUTHOR]

There is an enormous amount of water vapor in ambient air that can be converted into liquid water by several methods. A method that is capable of producing a large amount of water is a vapor compression system. However, this method requires significant power input, which may cause the cost of producing water to be prohibitive. In this paper, it is proposed that a vapor compression refrigeration system that is used to cool air in a combined cycle power plant has the potential to be a viable method of atmospheric water generation. This system produces saturated air by mixing atmospheric air with water, and reduces air temperature and humidity using a mechanical chiller. The reduction in inlet air temperature enables the combined cycle power plant to generate more power output, which is used to operate the air cooling system. Therefore, the air cooling system can harvest atmospheric water without requiring external power input. This concept is proven by simulating system performance in various atmospheric air conditions using system models of mass and energy balances. [ABSTRACT FROM AUTHOR]

Postharvest losses and spoilage of agricultural products are a major problem for tropical countries, and it is even more challenging for countries encountering fluctuating power shortages, such as Pakistan. Therefore, this study focused on the energy and economic analysis of cold storage to store three products (potatoes, pomegranates, and potatoes) according to the season and storage span throughout the year. The cooling load of the cold store was supported by a LiBr‐H2O vapor absorption and vapor compression refrigeration system to maintain the desired temperature for each product during cold storage. A solar thermal PV system is installed to operate cold storage refrigeration systems. Cold storage performance was analyzed by developing thermal models of integrated systems using the ambient conditions of Lahore, Pakistan. A parametric study was also conducted to analyze the impact of various working parameters on integrated system performance, and it was found that the maximum peak cooling load of 91 kW inside cold storage is attributed to pomegranates owing to high ambient conditions during its loading month. The product loading rate significantly affects the cooling load of cold storage and varies directly with it, as observed for an increase in the product loading rate from 0 to 50 000 kg/day cooling load also increases from 34 to 87 kW. To meet the thermal demand of the generator of the vapor absorption system, parabolic troughs were installed to operate cold storage, and it was found that a minimum of four PTC were needed to support the peak cooling load at the maximum product loading rate and minimum DNI value. To meet the electrical demand of cold storage electrical equipment and the compressor of the vapor compression system, solar photovoltaic panels were installed, and it was found that a minimum of 618 panels was required at a minimum tilted radiation value. To validate the viability of proposed design system economic analysis was also conducted which revealed a payback period of 12 years for Kinnow and potatoes and 16 years for pomegranates. [ABSTRACT FROM AUTHOR]

Gravity-assisted separation heat pipes (GSHPs) are extensively utilized in telecommunications base stations and data centers. To ensure year-round cooling, integrating GSHPs directly with a vapor compression refrigeration system is a viable solution. It is unavoidable that the refrigeration system's lubricant will infiltrate the heat pipe loop, thereby affecting its thermal performance. This paper examines the performance of a GSHP, which features a water-cooled plate heat exchanger as the condenser and a finned-tube heat exchanger as the evaporator, when the working fluid (R134a) is contaminated with a lubricant (POE, Emkarate RL-46H). The findings are compared with those from a system free of lubricant. The experimental outcomes indicate that the presence of lubricant degrades the heat transfer efficiency, particularly when the filling ratio is adequate and no significant superheat is observed at the evaporator's outlet. This results in a 3.86% increase in heat transfer resistance. When the charge of the working fluid is suboptimal, the average heat transfer resistance remains relatively constant at a 3% lubricant concentration yet increases to approximately 5.27% at a 4–6% lubricant concentration, and further to 12.32% at a 9% lubricant concentration. Concurrently, as the lubricant concentration fluctuates between 3% and 9%, the oil circulation ratio (OCR) varies from 0.02% to 0.11%. [ABSTRACT FROM AUTHOR]

Improvement of vapor-compression refrigeration systems taking into account ecological requirements will undoubtedly lead to the use of modern ozone-safe and non-greenhouse effect refrigerants. Increase of heat transfer and thermodynamic efficiency in general has raised the problem of selection of material and concentration of nanoparticles in the working mixture of refrigerant with mineral oil of compression refrigeration systems. The purpose of this study is to determine the influence of TiO2 and Al2O3 nanoparticles on the energy efficiency of refrigeration systems. Research methods: The study of operational and energy characteristics of compressor operation on the investigated mixtures was carried out on the experimental unit. Isobutane R600a refrigerant was used for the study. Efficiency is determined by power consumption, cooling capacity and efficiency. The refrigerant flow rate and nanoparticle concentration are varied during the experiment. Results: The experimental results concluded that Al2O3 nanoparticles with a mass concentration of 0.5% maximized the performance of the compressor refrigeration system. The addition of nanoparticles resulted in a significant increase in the cooling capacity, especially when compared to the original refrigeration-oil mixture with the cooling capacity parameter of 70 W. This parameter is about 79 W with the addition of TiO2 nanoparticles regardless of their concentration. When Al2O3 nanoparticles are added at concentrations of 0.1 and 0.5 wt.%, respectively, these parameters are 88 W and 102 W. [ABSTRACT FROM AUTHOR]

• For the first time, nanoparticles have been added into the cascade cycles. • An 6.37 % increase in performance was achieved with nano-refrigerant application. • With nano-refrigerant the emission of the CO 2 has decreased by 13.03 %. There is a lack of research in the literature on the application of nanoparticles to different cascade cycle configurations with environmental refrigerants in ultra-low temperature refrigeration applications. This study is the first on the use of nano-refrigerants in cascade refrigeration cycles. In this study, the effect of 2 wt.% of CuO to RE170 and R170-pure refrigerant utilization in cascade vapor compression refrigeration cycle (CVCRC), cascade ejector refrigeration cycle (CERC) and cascade ejector intercooler refrigeration cycle (CEIRC) are investigated to achieve higher performance values in ultra-low temperature applications. For CVCRC, CERC and CEIRC, the increases in terms of coefficient of performance (COP) with the use of nano-refrigerant were found to be 12.77 %, 8.20 %, and 6.37 %, respectively, and 18.55 %, 14.05 %, and 6.07 %, for exergy efficiency. Upon scrutinizing the results with nano-refrigerant in relation to the COP, the analysis revealed that the CEIRC cycle exhibited an improvement ranging from 13.43 % to 20.49 % in comparison to CERC. Additionally, with nano-refrigerant, the CEIRC cycle demonstrated an increase ranging from 42.39 % to 75.41 % when compared to CVCRC in COP. It was observed that the utilization of CEIRC led to a 13.03 % decrease in kg CO 2 emissions in compared to CERC and a reduction of 32.53 % compared to CVCRC with using nano-refrigerant. [ABSTRACT FROM AUTHOR]

Isentropic (adiabatic) compression of superheated vapor in vapor compression refrigeration cycles usually results in some discharge superheat, i.e. the discharge temperature exceeding the condensing temperature. Large discharge superheat reduces both operating range and compression efficiency. Sub-isentropic compression with heat rejection to the heat sink is therefore superior to adiabatic compression, as it results in lower discharge superheat and improved efficiency. However, significant temperature reduction by heat transfer through the working chamber walls is difficult to facilitate in common refrigeration compressors, particularly reciprocating compressors. Refrigerant and oil injection is a well-established method for reducing temperatures and increasing efficiency in screw and scroll compressors, as well as multi-stage systems. In comparison, effective methods for temperature reduction in single-stage reciprocating compressors are fairly limited. Therefore, a concept for high-pressure liquid injection is proposed. By means of a pump and injection valve, high-pressure liquid refrigerant is injected into the working chamber and atomized. The compressed gas is cooled through the evaporation of the injected liquid. The injection valve allows for control over the injection timing and quantity, enabling adjustment of the temperature profile, which is a major distinction from existing refrigerant injection methods. The coupled compression-injection process is evaluated for various refrigerants using an energetic chamber model. The injection is found to be particularly suitable for refrigerants with a large evaporation heat and a shallow dew line slope. For the example of ammonia, a theoretical reduction in compression work of 8.9% at an evaporation temperature of −10 °C and a condensing temperature of 45 °C is found. • Proposal of high-pressure liquid injection for reciprocating compressors. • Theoretical evaluation using energetic chamber model. • Potential for significant efficiency improvement compared to isentropic compression. • Increased operating range due to reduced discharge temperature. [ABSTRACT FROM AUTHOR]

This research paper figures out thermal performance analysis for vapor compression refrigeration (VCR) driven by the organic Rankine cycle (ORC) implementing MATLAB software. The ORC system is powered by improved evacuated tubes and compound parabolic collectors. The paper evaluates the overall exergetic efficiency and coefficient of performance using the working fluid Pentane/R245fa. The result of the present paper indicates that optimum COP of 0.75 and exergetic efficiency of 28% is obtained at 340 K of collector output temperatures, 0.1/0.9 of fractional mass of the working fluid, and 285, 300 K for VCR condenser and evaporator temperature, respectively. Sensitivity analysis pointed out that condenser temperature was the most impactful parameter for both exergetic efficiency and COP owing to higher F-value 'of 156.06' and '89.28,' respectively. Further, collector output temperature and fractional mass of the working fluid were the least impactful parameters owing to lower F-value '1.95' and '1.02' for exergetic efficiency and COP, respectively. [ABSTRACT FROM AUTHOR]

Solar-driven ejector cooling is a potential alternative for reducing overall energy usage. Hence, a review of solar-driven ejector refrigeration cycles, along with their integration with multi-generation systems, has been conducted, and they are structured into several sections. Initially, the basics of ejector technology, the standard ejector refrigeration cycle, and its performance parameters are discussed. Concise summaries of impactful studies on solar-driven ejector refrigeration cycles containing cycle modification and hybridization, working fluid selection, and available solar collectors, alongside thermal energy storage technologies, have also been added. The solar-driven multi-generation systems with ejector refrigeration cycles, as well as various recent studies on data-driven modeling of the ejector refrigeration cycle, are effectively discussed. Apart from this, the different challenges, along with the future outlooks of the solar-driven ejector refrigeration cycle, are also analyzed. Lastly, it is concluded that developing an energy-efficient solar-driven ejector refrigeration cycle may be a potential replacement for the existing electricity-driven vapor compression refrigeration cycle. Therefore, this review would be helpful for newcomers to understand complete incite ejector refrigeration cycles along with their integration with solar energy, which is essential for the sustainable development of human civilization in the current energy scenario. [ABSTRACT FROM AUTHOR]

Room-temperature elastocaloric cooling is considered as a zero-global-warming-potential alternative to conventional vapor-compression refrigeration technology. However, the limited entropy and large-deformation features of elastocaloric polymers hinder the creation of the breakthrough in their caloric responses and device development. Herein, we report that the addition of a small amount of inorganic nanofillers into the polymer induces the aggregate of the effective elastic chains via shearing the interlaminar molecular chains, which provides an additional contribution to the entropy in elastocaloric polymers. Consequently, the adiabatic temperature change of −18.0 K and the isothermal entropy change of 187.4 J kg−1 K−1 achieved in the polymer nanocomposites outperform those of current elastocaloric polymers. Moreover, a large-deformation cooling system with a work recovery efficiency of 56.3% is demonstrated. This work opens a new avenue for the development of high-performance elastocaloric polymers and prototypes for solid-state cooling applications. In this work, inorganic nanofillers are added to SEBS polymers to induce shearo-caloric effects, enhancing the elastocaloric response. Authors design and demonstrate a double-unit cooling device with a work recovery efficiency of 56.3% and a system coefficient of performance of 8.3. [ABSTRACT FROM AUTHOR]

The present investigation focuses on enhancing the efficiency of a vapor compression refrigeration system (VCRS) by proposing a Multiple Input Multiple Output (MIMO) control strategy based on the evaporator's two-phase length and superheat temperature. A moving boundary dynamic model for the VCRS is implemented using the Thermosys Matlab Toolbox. The study analyzes the influence of actuation parameters, specifically compressor speed and expansion valve opening, on control parameters, namely two-phase length and superheat temperature. A comprehensive analysis based on the first and second laws of thermodynamics is conducted across a wide range of operating conditions. Simulation results demonstrate that two-phase length can be effectively utilized as a control parameter by selecting operating points that maximize the system efficiency. Additionally, the study reveals that extending the evaporator's two-phase length to 80–90% of its limit increases system efficiency, enabling a reduction in compressor speed while maintaining the cooling capacity. [ABSTRACT FROM AUTHOR]

The electrocaloric effect (ECE) is considered as an environmentally friendly refrigeration technology, which can be used to replace vapor compression refrigeration. Lead-free antiferroelectric (AFE) ceramics are promising electrocaloric materials because of large saturation polarization and polarization change with temperature, which can generate large positive or negative ECE. In this work, the lead-free Ag(Nb 1-0.8x Hf x)O 3 (x = 0, 0.001 and 0.003) AFE ceramics are fabricated through a conventional solid-state reaction method which shows a decreased the phase transition temperature of M 1 - M 2 toward room temperature (RT), and a large negative ECE (Δ T = −2.3 K under 130 kV cm−1) is obtained near the ambient temperature by using an indirect measurement in ANH0.001 AFE ceramic. The large negative ECE behavior is ascribed to dipole disordering (i.e. the anti-parallel dipoles are broken and gradually becomes disordered under an external electric field) resulting from the field-induced phase transition under a modest electric field. This work shows that AgNbO 3 -based AFE ceramics could be used in the refrigeration devices as an electrocaloric material. [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]

In this study, the refrigerant R1234yf was subjected to experimental investigation in conjunction with a variety of nanoparticles as a potential alternative to R134a in a vapor compression refrigeration system. Initially, the performance of pure R1234yf was evaluated in the absence of modifications to the VCRS, employing energy and exergy analyses. The results demonstrated that R1234yf resulted in a 9% increase in compressor power input, an 8% reduction in cooling capacity, and a 17% decrease in EER in comparison to R134a. Furthermore, the second law efficiency exhibited a decline of 8%. In order to address these declines, Al2O3, graphene, and CNT nanoparticles were introduced to the VCRS with R1234yf via compressor oil at varying mass fractions. The greatest improvement in system performance was observed with the addition of 0.250% graphene by mass. This resulted in a 24% and 14% enhancement in cooling capacity and an increase in EER by 32% and 13%, respectively, when compared to pure R1234yf and R134a. The second law efficiency exhibited a slight improvement with the addition of graphene. [ABSTRACT FROM AUTHOR]

The process of air entering the vapor compression refrigeration system is very common, and it can happen during installation, maintenance, or charging. Since air is a non-condensable gas compared to the refrigerant gas inside the system, it causes deterioration in the system mainly due to high condensing pressure. This experimental study contributes to verifying the negative effects that can be left by non-condensable gases in the vapor-compression refrigeration system via analyzing the performance of a chest freezer charged with R134a refrigerant without an air fraction and with three air fractions 1.7%, 2.5% and 3.3% under steady-state conditions and an ambient temperature of 32°C. The results revealed that the performance of the chest freezer deteriorated clearly with the increase in air fraction; at an air fraction of 3.3% the power consumption increased by 37.1% and the coefficient of performance decreased by 42.8% compared to without air fraction. In addition to high noise and vibration. [ABSTRACT FROM AUTHOR]

This study examined the performance of reversed Brayton cycle heat pumps to supply heat above 300 °C. The aim was to overcome the current temperature limitations faced by heat pump technology in industrial heat supply sectors by examining the viability of the reversed Brayton cycle. In particular, the effects of the operating conditions on the cycle performance, such as the waste and return heat temperatures, were analyzed through thermal performance analysis. The reversed Brayton cycle heat pumps showed improved performance over conventional vapor compression cycle heat pumps when a heat supply above 215 °C was required. Furthermore, integrating additional heat exchangers into the cycle configuration was proposed in this study as a method to enhance waste heat utilization and recover unused heat from industrial processes. By incorporating preheating and recuperated cycles, these modifications broaden the operational range under the same operating conditions. They also improve the coefficient of performance (COP) of the reference cycle by up to 23% and 27.4%, respectively. This study explored the potential of reversed Brayton cycle heat pumps to supply heat above 300 °C and provided fundamental guidelines for the efficient design and operation of reversed Brayton cycle heat pumps. The results are expected to enhance our understanding of the performance characteristics of reversed Brayton cycle heat pump technology and expand its use as an alternative to fossil-fuel-based heat supply systems. [ABSTRACT FROM AUTHOR]

Preservation of perishable food produce is a major concern in the cold chain supply system. Development of an energy-efficient on-farm cold storage facility, hence, becomes essential. Integration of thermal storage into a vapor compression refrigeration (VCR)-driven cold room is a promising technology that can reduce power consumption and act as a thermal backup. However, designing a latent heat energy storage heat exchanger encounters challenges, such as low thermal conductivity of phase change materials (PCMs) and poor heat exchanger efficiencies, leading to ineffective charging–discharging cycles. The current study investigates the effect of the integration of a Phase Change Material (PCM) in terms of the selection of the PCM, the optimal positioning of the PCM heat exchanger, and the selection of heat exchanger encapsulation material. Numerical analysis was undertaken using 3D Experience software (version: 2024x.D31.R426rel.202403212040) by creating a 3D model of a 3.4 m3 micro-cold storage unit to understand the inner temperature distribution profile. Further, the experimental setup was developed, and tests were conducted, during which the energy consumption of 1.1 kWh was recorded for the total compressor run time of 1 h. Results indicated that an improved cooling effect was achieved by positioning the PCM trays on the wall opposite the evaporator. It is seen that a temperature difference in the range of 5 to 7 °C exists between the phase change temperature of PCM and the optimal storage temperature depending on the encapsulation material. Hence, PCM selection for thermal storage applications would have an important bearing on the material and configuration of the PCM encapsulation. [ABSTRACT FROM AUTHOR]

Ammonia is a vital chemical with numerous applications. Currently, the primary methods for generating the necessary reactants for ammonia production involve steam methane reforming (SMR) and cryogenic air separation unit (CASU), while the Haber-Bosch process converts these reactants into ammonia. However, the SMR process releases substantial amounts of CO 2 , making it imperative to employ an efficient and cost-effective CO 2 capture technology to mitigate emissions. This investigation focuses on evaluating the cryogenic CO 2 capture (CCC) process for blue ammonia production and provides a thorough economic analysis, estimating both the initial investment costs and operational expenses involved in producing blue ammonia. The results indicated that the CCC process can capture 90% of the CO 2 content in the flue gas emitted by the SMR, incurring an energy penalty of 0.724 M J e / k g C O 2 while capturing CO 2 in the liquid phase with purities exceeding 99.9%. In this case, the estimated CO 2 capture costs would be 18.05, 45.1, and 16.65 USD/ton in 2021, 2022, and 2023, respectively. This represents a 40% reduction compared to the CO 2 capture costs associated with conventional amine-based technology. The results of this study indicate that the annual electricity costs for ammonia production increase by 38.5% and 64.2% when employing the CCC and amine-based processes, respectively. This investigation employed an isothermal reactor for ammonia synthesis, using the heat from the exothermic reaction in a water ammonia absorption refrigeration cycle (ARC) to condense and purify ammonia. The results show that the ARC system can effectively condense ammonia at −6 °C, producing a liquid ammonia stream with 99.3% purity. This leads to a 95% reduction in power consumption compared to a vapor compression refrigeration cycle (VCRC). Consequently, this method has the potential to decrease the annual operational costs for ammonia production by 2.92%, 2.69%, and 3.13% in 2021, 2022, and 2023, respectively. This study indicated that the hydrogen production unit incurs the highest initial investment costs, as well as operating costs, in the blue ammonia production process, followed by CASU and the Haber-Bosch process. • The performance of the CCC process for blue NH 3 production was thoroughly evaluated. • The economic impacts of CCC process were compared with those of amine-based method. • An energy efficient method for condensation of NH 3 in Haber-Bosch process is given. • Natural gas costs mainly influence the operating costs of blue NH 3 production. [ABSTRACT FROM AUTHOR]