Vapor Compression Refrigeration System Research Articles

Performance of Solar Hybrid Cooling Operated by Solar Compound Parabolic Collectors under Weather Conditions in Riyadh, Kingdom of Saudi Arabia

The scientific aim of this work is to encourage energy conservation. This article offers a fresh perspective on renewable energy in the air conditioning sector, the country’s economic growth, and environment-friendly techniques to overcome global warming challenges. In this research, a solar vapor absorption refrigeration (SVAR) system was combined with a conventional vapor compression refrigeration (VCR) system to analyze their combined performance, employing a compound parabolic collector (CPC). The goal was to assess the performance of a solar hybrid cooling system using this non-tracking solar collector. CPC was validated for heat output with 2.9% uncertainty by utilizing an engineering equation solver (EES). Other system components were also validated with EES and then extended to a larger-capacity solar hybrid cooling system. The results of this research indicate that CPC is effective in providing the required heat to SVAR throughout the year without any tracking, and the integration of SVAR in series with the VCR condenser produces 83% higher COP than the system that integrates VCR with the condenser of the SVAR system for Riyadh. The configuration results in high values of exergy COP and an efficiency of 88% and 84%, respectively, increases the cooling capacity of the VCR by 68%, and decreases the carbon emission by 166.4%.

A novel approach of using TiO2 and SiO2 nanoparticles and hydrocarbon refrigerant R600a in retrofitted vapour compression refrigeration system for environment protection and system performance enhancement

A novel approach of using TiO2 and SiO2 nanoparticles and hydrocarbon refrigerant R600a in retrofitted vapour compression refrigeration system for environment protection and system performance enhancement

On the Use of Ultrasonic Flowmeters for Cooling Energy Metering and Sub-Metering in Direct Expansion Systems

The Energy Efficiency Directive (EED, Directive 2012/27/EU) has made mandatory the installation of individual metering systems in the case of buildings with centralized heating/cooling and hot water sources (multi-apartment and multi-purpose buildings), provided it is economically and technically feasible. Individual metering of heating/cooling systems is mainly based on thermal energy meters (TEM), which are widely used for direct metering in heating applications. On the other hand, direct metering of energy consumption in cooling systems still represents a challenge, given the different types of cooling units and the lack of regulations from the technical and legal points of view. In this context, this paper briefly overviews the available centralized cooling systems and the possible solutions for metering and sub-metering, which depend on the specific application. Vapour Compression Refrigeration (VCR) systems are spreading worldwide for air conditioning applications. Particular attention has been paid to the direct metering of cooling energy and specifically to refrigerant flow rate measurement, which represents a critical issue because of the small-diameter pipes and the different thermodynamic properties of the fluid used. Thus, an experimental campaign has been developed and carried out in order to compare a clamp-on ultrasonic flowmeter with a more accurate Coriolis one in a direct expansion (DE) system. The experimental tests have been performed at two different temperature conditions, showing a relative error in the mass flow rate measurements within ±10%.

Thermodynamic performance analysis of a low-temperature absorption refrigeration system in a proton exchange membrane fuel cell refrigerated vehicle

To utilize the waste heat of a proton exchange membrane fuel cell (PEMFC), an absorption refrigeration system (ARS) with a novel low-temperature working pair LiBr- 1-Butyl-3-methylimidazolium Bromide ([BMIM]Br) /C2H5OH is proposed for cooling in the refrigerated vehicle. The thermodynamic performance of the ARS using LiBr-[BMIM]Br/C2H5OH is investigated under various operating conditions and compared with that using the conventional working pair LiBr/H2O. The efficiency performance of the PEMFC refrigerated vehicle using ARS and vapor compression refrigeration system (VCRS) are also studied and compared under different operating conditions. The results show that the ARS achieves the maximum coefficient of performance (COP) of 0.86 and the generation temperature is reduced to 65.45 °C with LiBr-[BMIM]Br/C2H5OH a decrease around 15% in comparison to LiBr/H2O. Comprehensive efficiency of the stack coupled with ARS is up to 85% due to recovery its waste heat. Under identical output power and cooling capacity of the refrigerator vehicle, the stack coupled with a VCRS has a comprehensive efficiency of 70% and requires a larger power scale. Thus, the stack coupled with ARS using LiBr-[BMIM]Br/C2H5OH has a great significance for enhancing the performance, enlarging the mileage, and reducing the cost of the refrigerator vehicle.

Assessing Energy Performance and Environmental Impact of Low GWP Vapor Compression Chilled Water Systems

The global concern regarding the environmental repercussions of refrigerants has escalated due to their adverse effects. These substances deplete the ozone layer and intensify the greenhouse effect. International agreements such as the Montreal and Kyoto Protocols and COP21 have imposed restrictions on refrigerants with high global warming potential (GWP) to address these issues. This study aims to explore the feasibility, energy efficiency, and environmental impact of utilizing the HFO (hydrofluoric-olefin) refrigerant R1234ze as a substitute for HFCs (hydrofluoric-carbon) (R134a, R407C, and R410A) and HCFCs (R22) in air-cooled vapor compression refrigeration and air conditioning systems. To determine their effectiveness, we evaluate the energy performance of various refrigerant operating cycles across a wide range of ambient and evaporating temperatures. Additionally, we conduct environmental impact analyses based on the total equivalent warming impact (TEWI) parameter calculated for commercially available chillers that utilize the fluids mentioned above. Our findings indicate that vapor compression chilled water systems employing R1234ze exhibit the highest performance coefficient and the lowest annual TEWI.

Advance exergy and coefficient of structural bond analysis of dedicated mechanical subcooled vapor compression refrigeration system

The dedicated mechanical subcooled (DMS) refrigeration system is examined in the current study, based on the configuration of energy and exergy. The performance of a simple vapor compression refrigeration system (VCRS) and dedicated mechanical subcooled system are evaluated while maintaining the same cooling capacity (i.e. 100 kW). The results of comparative study showed an improvement of 8.2% in the coefficient of performance (COP) of the DMS system. Additionally, it has been discovered that the exergetic efficacy of the VCRS and DMS systems is 32.8% and 35.2%, respectively. The above results proved that, the suggested system perform better with more efficient cooling technology, which proves it to be a better option for design engineers in water chilling application in the foreseeable future.The coefficient of structural bond (CSB) and advanced exergy analysis (AEA) methodologies along with environmental benefits of the DMS system are also looked into in light. The value of CSB for conderser-1 is observed to be highest (2.08), with total irreversibility rate of 22.7%. However, in case of compressor-1 the highest irreversibility rate of 34.8% is observed but its CSB value is only 1.09. Therefore, by enhancing the performance of system components, it is possible to avoid 42.9% of the overall irreversibility rate of the dedicated mechanical subcooled system using enhanced exergy analysis.

Assessment of the Impact of using Zeotropic Mixture on the Thermodynamic Performance of Organic Rankine Cycle Integrated Vapor Compression Refrigeration System

Assessment of the Impact of using Zeotropic Mixture on the Thermodynamic Performance of Organic Rankine Cycle Integrated Vapor Compression Refrigeration System

Evaluation of new dew point evaporative cooler heat and mass exchanger designs with different geometries

In this study four new geometries of heat and mass exchanger for dew point evaporative cooling are investigated and their performance is compared to that of the commonly used flat plate and corrugated plate exchangers. In the proposed exchangers, each dry channel is completely enclosed by its adjacent wet channels, and each wet channel is completely enclosed by its adjacent dry channels (related detailed information is presented graphically in this paper). In addition, a robust numerical model was developed and is examined under various operational and geometrical conditions. The analysis showed that the proposed dew point evaporative coolers improve the chilled air temperature, water consumption, cooling capacity, and energy efficiency. In particular, the circular concentric tube exchanger, under certain operating conditions (inlet air temperature, humidity ratio, and velocity of 40°C, 6 g/kg, and 3 m/s, respectively), could produce the lowest chilled air temperature of 9.6°C and the highest wet bulb and dew point effectiveness of 148% and 99%, respectively. Additionally, water consumption is reduced to 1.34 L/hr for an inlet air velocity of 1 m/s. A triangular tube exchanger achieved the highest cooling capacity and coefficient of performance, but consumed the largest amount of water. Our geometrical analysis demonstrates that the overall performance of dew point evaporative cooling systems can be improved by employing new geometries for heat and mass exchanger channels. Practical application: The dew point evaporative cooler is an environmentally friendly air conditioning system used in buildings. It is considered the strongest candidate to replace vapour-compression refrigeration systems because it consumes considerably less electricity while achieving high performance. Our research demonstrates that through revised geometry it is possible to further improve the performance of the system leading to improved energy and water efficiency.

Evaluating Eco-Friendly Refrigerant Alternatives for Cascade Refrigeration Systems: A Thermoeconomic Analysis

A simple vapor-compression refrigeration system becomes ineffective and inefficient as it consumes a huge energy supply when operating between large temperature differences. Moreover, the recent Kigali amendment has raised a concern about phasing out some hydrofluorocarbon refrigerants due to their impact on the environment. In this paper, a numerical investigation is carried out to compare the performance of a cascade refrigeration system with two environmentally friendly refrigerant combinations, namely, R170–R404A and R41–R404A. Refrigerant R170, from the hydrocarbon category, and refrigerant R41, from the hydrofluorocarbon category, are separately chosen for the low-temperature circuit due to their similar thermophysical properties. On the other hand, refrigerant R404A is selected for the high-temperature circuit. An attempt is made to replace refrigerant R41 with refrigerant R170 as a possible alternative. The condenser temperature is kept constant at 40 °C, and the evaporator temperature is varied from −60 °C to −30 °C. The mathematical model developed for the cascade refrigeration system is solved using Engineering Equation Solver (EES). The effect of evaporator temperature on different performance parameters such as the COP, exergetic efficiency, and total plant cost rate is evaluated. The predicted results show that the thermoeconomic performance of the R170–R404A-based system is marginally lower compared to that of the R41–R404A-based system. The system using refrigerant pair R170–R404A has achieved only a 2.4% lower exergetic efficiency compared to the system using R41–R404A, with an increase in the annual plant cost rate of only USD 200. As the global warming potential (GWP) of R170 is less than that of R41, and R170 belongs to the hydrocarbon category, the use of the R170–R404A combination in a cascade refrigeration system can be recommended as an alternative to R41–R404A.

Parametric study of a vapor compression refrigeration system integrated with a PCM storage tank for increasing condenser sub-cooled temperature

In this work, the parametric study of a vapor compression refrigeration system integrated with a PCM storage tank for increasing the condenser sub-cooled temperature has been conducted based on the hottest day in Tehran city. The effects of various parameters such as comfort zone temperature, condenser and evaporator temperatures, and changes in heat transfer coefficient relative to the thickness of the ice formation in the PCM tank have been considered for simulating the desired system in the EES software. The focus of this study is to figure out the system's performance according to the changes in the effective parameters of the PCM storage tank. The results indicate that adding the PCM storage tank to the conventional vapor compression unit raises total daily electric energy consumption from 20.86% to 30.63% compared to the conventional one. However, it boosts the accessible cooling energy during the cold energy discharging process compared to the conventional one from 39.67% to 54.60%. The accessible cooling energy increases from 3.11% to 3.59% during the whole day. Furthermore, adding the PCM tank diminishes the total daily COP from 14.68% to 20.7% compared to the conventional unit.

Komparasi Kinerja AC Kendaraan dengan Menggunakan Refrigeran R-134a, dan R-290

The development of vapor compression refrigeration systems currently depends on the issue of environmental problems related to ozone layer depletion (ODP) and global warming potential (GWP). In addition to environmental issues, low energy use is also in the spotlight of researchers. To solve the problem of refrigeration development, natural refrigeration, especially hydrocarbons, is the focus of attention. Hydrocarbons are refrigerants that have excellent properties to be natural refrigerants. This study aims to compare the performance of refrigerant R-134a with R-290. The research used a standard vapor compression refrigeration system with a TEV-type expansion valve. The system performance is seen through compression, refrigeration effect, and COP with variations in compressor rotational speed of 1000 rpm, 1500 rpm, and 2000 rpm. The results showed that the compression work, refrigeration effect, and coefficient of performance (COP) of R-290 had a more excellent value. R-290 produces the highest compression work at a 2000 rpm compressor speed of 33.34 kJ/kg for the refrigeration effect at 1000 rpm of 353.33 kJ/kg and COP at 1500 rpm 12.32.

Optimization of exergetic performance and payback period of organic rankine cycle integrated vapor compression refrigeration system based on exergy, economic, and environmental criteria

In this paper, a multi-objective optimization study is carried out to determine the optimal exergetic performance (𝜂𝑒𝑥) and the payback period (PB) of the organic Rankine cycle (ORC) integrated vapor compression refrigeration (VCR) system based on exergy, economic, and environmental criteria using non-dominated sort genetic algorithm-II (NSGA-II). Moreover, a sensitivity analysis is carried out to improve the exergetic performance of the system. The working fluid, the pinch-point temperature difference of the ORC evaporator (ΔToep ), con-denser (ΔTpcond), and the VCR evaporator (ΔTpve), cooling water inlet temperature (Tcw1), chilled fluid temperature (Tcf2), and heat-source inlet temperature (Th1) are taken as the decision vari-ables. The results of this study indicate that butane is the most suitable working fluid for op-timal exergetic efficiency, 𝜂𝑒𝑥 (33.7%) and payback period, PB (4.9 years) of the system. The optimal values of other decision variables such as Th1, Tcw1, Tcf2, ΔToep , ΔTpve , and ΔTpcondare 378 K, 313 K, 276 K, 10 K, 5 K, and 5 K respectively.

Sustainability framework of intelligent social houses with a synergy of double-façade architecture and active air conditioning systems

Social houses are built around the world to fulfill the basic needs of the growing population, especially middle-income families. Owing to the low budget available for such houses around the globe, necessary energy codes are often compromised. This research, through a methodological sustainability framework, presents the case study of Mexico with the objective to address this worldwide issue. More than 100,000 social houses were built in Mexico just in the year 2021 without strictly following any definitive building energy codes. Eventually, this is a ticking bomb, if left unaddressed, that can bring serious energy and environmental consequences connected with various social issues. Thus, as a research gap, the conventional 4E (energy, exergy, economic, and environmental) analysis cannot fully address such a complex energy-environmental-economic-social nexus. This work proposes an integrated sustainability framework of the practicability of the bioclimatic architecture of such a social house including energy, economic, environmental, and social assessment (novel addition to the analysis). The novel methodology is implemented on a novel technological advancement where double-façade architecture (i.e., solar chimney) is installed through a synergy and intelligent operation with an active air conditioning system including a desiccant enhanced air cooler and novel dew-point evaporative cooler. The article makes use of conventional physics-based modeling of thermal machines combined with an artificial neural network digital twin-based data-driven non-sorting genetic optimization of solar chimneys for various climatic conditions of Mexico. The optimal points are evaluated using annual climatic data to maintain the thermal comfort conditions and the results have suggested an increase of ∼48% through intelligent integration of double-façade architecture with the Maisotsenko cycle air cooler. Life-cycle economic assessment has suggested the Levelized cost of air conditioning be between 0.0096 and 0.0390 USD/kWh and can save up to ∼273 MXN per month with a real payback period of ∼8 years. Environment assessment has reported mitigation of up to ∼5668.59 kgCO2/year as compared to conventional vapor compression refrigeration systems. The social assessment is conducted on a pilot scale to directly ask the people of Mexico about their perception of the installation of the solar chimney while giving the fact that the initial price of the social houses can increase between 2.5 and 4%. It is reported that ∼62% of the sample is willing to install it even with a high price tag with a motive to initiate the climate change mitigation phenomena. The importance of the work has concluded that the government needs to take drastic and tough decisions to further regulate the energy efficiency in the social houses and limit the constructors to offer sustainable building construction.

Performance improvement of vapour compression refrigeration system using phase change material and thermoelectric generator

Performance improvement of vapour compression refrigeration system using phase change material and thermoelectric generator

A new approach for environmental analysis of vapor compression refrigeration systems: Environmental impact index

Vapor-compression refrigeration (VCR) cycles are used to transfer heat from a low-temperature environment to a high-temperature environment. To reduce harmful emissions, environmentally friendly refrigerants should be selected. Metrics like global warming potential and life cycle climate performance are used for environmentally friendly refrigerants. These metrics are independent of each other and are analyzed and evaluated separately. In this study, a new metric was proposed for the environmental analysis of VCR systems and named as environmental impact index (EII). EII defined for the first time in this research, includes the use of both energy, exergy, and low-emission renewable energy at the same time. Also, EII analysis of a cooling system using various refrigerants was performed for all cities of Türkiye. In the case of using R134a, R1234yf, and R1234ze refrigerants in the cooling system the cities with the highest and lowest EII values of the cooling system are Ardahan and Şanlıurfa, respectively. The EII of R134a, R1234yf, and R1234ze (E) for Şanlıurfa are 49.79, 51.81, and 49.75, respectively. The EII of R134a, R1234yf, and R1234ze (E) for Ardahan are 73.75, 75.13, and 73.13, respectively. It was concluded that when choosing refrigerants for VCR systems, attention should be paid not only to the GWP ratios of refrigerants, but also to energy and exergy performance, and energy options with lower emissions.

Performance of vapour compression based atmospheric water generation systems in arid conditions – Experimentations and perspectives in the Gulf region

The scarcity of fresh surface water resources combined with the over-exploitation of groundwater reserves across the Gulf Cooperation Countries (GCC) has increased the dependence on seawater desalination to satisfy drinking water requirements. However, the predominance of high relative humidity and temperatures within this region, offers an unrivalled potential for atmospheric water generation (AWG). Most AWG techniques are currently limited to emergency response or remote locations where conventional water production/distribution strategies are ineffective or prohibitive. This study presents an analysis of various scalable AWG techniques including direct cooling of air using Vapour Compression Refrigeration Systems (VCRS) and Air Conditioner Condensate Recovery (ACCR). Three commercial VCRS-type AWG units were evaluated at the same time during a 4-month field test in summer 2022 in Masdar City, Abu Dhabi, UAE and their performances were correlated to the relative humidity and temperature of the inlet air in both indoor and outdoor conditions. In addition, up to 30.8 L·day−1·TR−1 of AC condensates were collected from a 7.87 m3·s−1 Fresh Air Handling Unit that was installed on the roof of a University building. This study demonstrates the potential of AWG as a promising solution to increase water security across arid countries by offering a complementary option to desalination without brine generation.

Thermodynamic investigation of a centrifugal reverse Brayton cycle for refrigeration in air conditioning filed

The reverse Brayton cycle (RBC) is known to exhibit a lower coefficient of performance (COP) when compared to conventional vapor-compression refrigeration systems. To tackle this issue, this study proposes a centrifugal reverse Brayton cycle (CRBC) that features a rotating heat exchanger, which utilizes the conversion mechanism between equal potential energy and pressure energy to enhance system performance. The findings indicate that the COP of the CRBC is roughly inversely proportional to the working fluid density, making CO2 a more suitable option for CRBC systems than conventional working fluids. We propose three different cycles for the CRBC system: the diamond cycle, trapezoid cycle, and rectangle cycle. From both technical and operational perspectives, the trapezoid cycle appears to be the preferred choice for CRBC. When the isentropic efficiency of the CRBC system exceeds 95%, its coefficient of performance (COP) ranges from 5.31 to 5.7, whereas the COP of transcritical carbon dioxide refrigeration cycle (tCO2), air RBC, and CO2 RBC are around 4.3, 1.9, and 0.79, respectively. This suggests that the performance of the CRBC system surpasses that of RBC by a significant margin, while achieving comparable performance to conventional vapor compression refrigeration systems. Moreover, the dimensionless power reflecting the installation capacity requirements for CRBC, tCO2, air RBC and CO2 RBC are around 0.2, 0.35, 5.3 and 1.9, respectively. This indicates that the compressor/expander capacity demand for system CRBC approaches the thermodynamic minimum.

Estimation of thermodynamic properties of environmentally friendly new-generation R515B and R450A as an alternative to R134a

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.

Thermodynamic optimisation of a booster-ejector vapour compression refrigeration system using solar energy and R152a/Cu nano-refrigerant

Conventional vapour compression refrigeration systems require high electrical energy for low temperature applications. For the first time in the literature to reduce this required energy, comprehensive thermodynamic analysis and optimization of booster-assisted ejector expansion vapour compression refrigeration system with R152a/Cu nano-refrigerant are presented for low-temperature applications. Solar panels are used to cover the total compressor work, using the climate data of Izmir, Turkey. According to the thermodynamic optimization findings, the use of nanoparticles in the refrigeration system led to several improvements when compared to the R152a refrigeration system. These enhancements include a reduction of 6.52-11.71% in the main compressor discharge temperature, a decrease of 18.46-34.48% in the total exergy destruction rate, an increase of 3.08-4.04% in the entrainment ratio, a reduction of 0.089-3.25% in the ejector area ratio, a decrease of 8.34-14.27% in the panel area, and an increase of 8.09-14.05% in both the coefficient of performance and exergy efficiency. Another thing worth mentioning is that coefficient of performance and exergy efficiency improved by 2.06% and 1.96%, respectively, while total exergy destruction reduced by 4.83% compared to our previous study. The results obtained from the thermodynamic optimisation provide a useful reference for the design of an experimental system, as they provide evidence of model validity and can guide the implementation of the system.

Influence of Refrigerant Type, Nanoparticle’s Concentration and Size on the Performance and Exergy Efficiency of the Vapour Compression Refrigeration System Using Al2O3 Based Nanolubricant

Vapour compression refrigeration systems (VCRS) are commonly used in the tropic region for the cooling and preservation of household and industrial items. The performance, power consumption and exergy efficiency of the vapour compression refrigeration system (VCRS) can be improved by replacing the lubricant with nanolubricants. In this study, nanolubricants were prepared at different mass concentrations of 1%, 3%, 5%, 10%, and 20% using aluminium oxide (Al2O3) nanoparticles of nominal diameter 10 nm, 20–30 nm and 80 nm. Scanning electron microscopy (SEM) and X-ray diffraction analyses were carried out on the aluminium oxide (Al2O3) nanoparticles. Using R600a and R134a refrigerants to investigate heat transfer behaviour of nanorefrigerant, the addition of nanoparticles into the VCRS enhanced the performance and exergy efficiency of the system. This was achieved by reducing the energy consumed and destroyed within the compressor of VCRS. Smaller nominal diameter nanoparticles of 10 nm performed better and possess better exergy efficiency for nanoR600a while the 20–30 nm had the best performance for nanoR134a refrigerant. The average value of coefficient of performance (COP) obtained was observed to be higher for R600a using 10 nm sized nanoparticles compared with R134a.