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Keywords = compressor-discharge cooler

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16 pages, 6468 KiB  
Article
Enhancing Semiconductor Chiller Performance: Investigating the Performance Characteristics of Ultra-Low-Temperature Chillers Applying a Liquid Receiver
by Joon-Hyuk Lee, Hye-In Jung, Su-Been Lee and Chang-Hyo Son
Energies 2024, 17(20), 5144; https://doi.org/10.3390/en17205144 - 16 Oct 2024
Viewed by 675
Abstract
This study investigates the implementation of a cryogenic chiller utilizing a mixed-refrigerant cascade refrigeration cycle (MRCRC). In this setup, R-404A is employed in the high-temperature circuit (HTC), while a mixture of refrigerants is utilized in the low-temperature circuit (LTC). Unlike a conventional MRCRC [...] Read more.
This study investigates the implementation of a cryogenic chiller utilizing a mixed-refrigerant cascade refrigeration cycle (MRCRC). In this setup, R-404A is employed in the high-temperature circuit (HTC), while a mixture of refrigerants is utilized in the low-temperature circuit (LTC). Unlike a conventional MRCRC that operates without a receiver to maintain the composition ratio, this research explores the impact of receiver installation on system performance. Experiments were conducted with and without a receiver to assess performance improvements and device behavior. With a fixed refrigerant charge of 4 kg, the suction and discharge pressures of the LTC compressor remained low and stable after the receiver’s installation. The addition of a receiver significantly reduced the cooling time, with further reductions observed as the refrigerant charge increased. The system achieved evaporative heat capacities of 0.59, 1.76, and 2 kW for refrigerant charges of 4, 7, and 9 kg, respectively. Notably, at the maximum refrigerant charge of 11 kg, the evaporative heat capacity peaked at 3.3 kW. These findings indicate that incorporating a receiver is crucial for enhancing the cooling performance of cryogenic coolers using mixed refrigerants and stabilizing device operation. This contrasts with previous studies that omitted receivers due to concerns over potential alterations in the composition ratio of the mixed refrigerant. Full article
(This article belongs to the Section J: Thermal Management)
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13 pages, 1524 KiB  
Article
Performance Comparison of High-Temperature Heat Pumps with Different Vapor Refrigerant Injection Techniques
by Yuqiang Yang, Yu Wang, Zhaoyang Xu, Baojiang Xie, Yong Hu, Jiatao Yu, Yehong Chen, Ting Zhang, Zhenneng Lu and Yulie Gong
Processes 2024, 12(3), 566; https://doi.org/10.3390/pr12030566 - 13 Mar 2024
Cited by 2 | Viewed by 1635
Abstract
In order to develop a highly efficient and stable high-temperature heat pump to realize high-efficient electrification in the industrial sector, performance of high-temperature heat pumps with a flash tank vapor injection and sub-cooler vapor injection are compared under different evaporation temperatures, condensation temperatures, [...] Read more.
In order to develop a highly efficient and stable high-temperature heat pump to realize high-efficient electrification in the industrial sector, performance of high-temperature heat pumps with a flash tank vapor injection and sub-cooler vapor injection are compared under different evaporation temperatures, condensation temperatures, compressor suction superheat degrees, subcooling degrees and compressor isentropic efficiencies. The results show that the COP, injection mass flow ratio and VHC of the FTVC are higher than those of the SVIC-0, SVIC-5, SVIC-10 and SVIC-20 under the same working conditions, while the discharge temperature of the FTVC is approximately equal to that of the SVIC-0 and lower than those of the SVIC-5, SVIC-10 and SVIC-20. When the evaporation temperature, the condensation temperature and injection pressure are 55 °C, 125 °C and 921.4 kPa, respectively, the system COP of the FTVC is 4.49, which is approximately 6.7%, 7.3%, 7.8% and 8.9% higher than those of the SVIC-0, SVIC-5, SVIC-10, and SVIC-20, respectively. Full article
(This article belongs to the Special Issue Smart Wearable Technology: Thermal Management and Energy Applications)
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21 pages, 9521 KiB  
Article
A New Multi-Objective Optimization Strategy for Improved C3MR Liquefaction Process
by Fenghe Cui, Lei Pan, Yi Pang, Jianwei Chen, Fan Shi and Yin Liang
Processes 2024, 12(3), 542; https://doi.org/10.3390/pr12030542 - 10 Mar 2024
Viewed by 1326
Abstract
In the traditional C3MR process (T-C3MR), the boiling gas (BOG) output from the last stage of the gas–liquid separator is directly discharged, in which the excellent low-temperature capability is not utilized, and the system efficiency is decreased. In liquefied natural gas (LNG), single-objective [...] Read more.
In the traditional C3MR process (T-C3MR), the boiling gas (BOG) output from the last stage of the gas–liquid separator is directly discharged, in which the excellent low-temperature capability is not utilized, and the system efficiency is decreased. In liquefied natural gas (LNG), single-objective optimization methods are commonly used to optimize system parameters, which may result in incomplete system analysis. To solve the above problems, this paper proposes a multi-objective optimization strategy for the improved C3MR process(I-C3MR) based on a new multi-objective optimization algorithm called EHR-GWO-GA. Firstly, the main work proposes an I-C3MR structure. Secondly, an optimization strategy of the I-C3MR with the maximization of liquefaction amount, minimization of unit energy consumption and minimization of exergy loss as objective functions are proposed. Based on the optimization results, the influence of decision variables on liquefaction amount, unit energy consumption and exergy loss are analyzed, and the results show that the decision variables have good adaptability. Finally, a detailed exergy analysis of the equipment used is made, and the results show that the main exergy losses come from the water coolers and compressors, accounting for 32% and 34%, respectively. Compared to the T-C3MR, the improved C3MR based on EHR-GWO-GA(E-C3MR) has an approximate 8% increase in liquefaction amount—a roughly 23% decrease in unit energy consumption and a decrease of nearly 24% in exergy loss. Full article
(This article belongs to the Section Chemical Processes and Systems)
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17 pages, 4419 KiB  
Article
Energy and Exergy Analysis of a Combined Cooling Heating and Power System with Regeneration
by Jobel Jose, Rajesh Kanna Parthasarathy and Senthil Kumar Arumugam
Sustainability 2023, 15(18), 13523; https://doi.org/10.3390/su151813523 - 10 Sep 2023
Cited by 2 | Viewed by 1454
Abstract
Solar assisted trigeneration system has proved to be a potential method in generating power with net zero carbon emissions. The present work aims to address the potential ways to improve the efficiency of the solar energy-integrated carbon dioxide trigeneration system. A regeneration integrated [...] Read more.
Solar assisted trigeneration system has proved to be a potential method in generating power with net zero carbon emissions. The present work aims to address the potential ways to improve the efficiency of the solar energy-integrated carbon dioxide trigeneration system. A regeneration integrated combined cooling, heating, and power system is proposed. With a comprehensive thermodynamic model, the proposed system is simulated for various operating conditions. A component-level exergy analysis is also conducted to estimate the total irreversibility of the system. As the gas cooler exit temperature increases, the overall system irreversibility also increases. When the bleed mass is 20% of the total mass, the system has the lowest energy destruction rate. The potential component that contributes most to system irreversibility is the gas cooler, followed by the regenerator and expansion valve. The proposed system with regeneration yields 29% more COP than the conventional system when operating at lower compressor discharge pressure and a gas cooler exit temperature of 34 °C. It is inferred from the obtained results that to reduce the total irreversibility of the system, it is advised to operate the system at a lower compressor discharge pressure and gas cooler exit temperature. Full article
(This article belongs to the Section Energy Sustainability)
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15 pages, 4171 KiB  
Article
Using a Mine Dewatering System to Increase Cooling Capacity and Energy Recovery of Underground Refrigeration Plant: A Case Study
by Dariusz Obracaj, Nikodem Szlązak and Marek Korzec
Energies 2022, 15(24), 9481; https://doi.org/10.3390/en15249481 - 14 Dec 2022
Cited by 2 | Viewed by 2997
Abstract
Heat stress in deep hot mines is a factor that often determines the possibility of technical mining of natural resources. One of the solutions enabling miners to work in such mines is air cooling. Cooling systems vary, and their selection depends on the [...] Read more.
Heat stress in deep hot mines is a factor that often determines the possibility of technical mining of natural resources. One of the solutions enabling miners to work in such mines is air cooling. Cooling systems vary, and their selection depends on the type of mine and the mining methods used. Limited air cooling capabilities exist in electric-powered coal mines. The main solution for air cooling is based on movable spot air coolers. Such systems commonly use surface or underground refrigeration plants. An underground refrigeration plant (URP) equipped with compressor chillers does not achieve more than 2.5–3.0 MW of cooling capacity due to the limited heat rejection capacity of return air streams in a typical coal mine. The method discussed in this paper, using mine water to discharge waste heat from the underground refrigeration plant, provides a measurable benefit for optimizing the mine air cooling system. The main purpose of this research is to study the feasibility and effect of water diversion from the actual mine drainage system to the underground refrigeration plant. The water drainage system in an underground mine is called the dewatering system of the mine. The heated water in the condensers of the chillers is directed back to the mine’s central dewatering system. The recovery from water discharged to the surface contributes to optimising energy consumption for a mine air cooling and the sustainable discharge of wastewater. In addition, using the total water flow from the mine dewatering system to reject heat in compressor chillers, compared with the traditional solution, can improve the cooling capacity of URP. These findings may provide beneficial guidance for practical applications in deep hot mines with small natural water inflow. Full article
(This article belongs to the Special Issue Smart Materials and Devices for Energy Saving and Harvesting)
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16 pages, 3877 KiB  
Article
Effect of Compressor-Discharge-Cooler Heat-Exchanger Length Using Condensate Water on the Performance of a Split-Type Air Conditioner Using R32 as Working Fluid
by Kasni Sumeru, Triaji Pangripto Pramudantoro, Andriyanto Setyawan, Rizki Muliawan, Toto Tohir and Mohamad Firdaus bin Sukri
Energies 2022, 15(21), 8024; https://doi.org/10.3390/en15218024 - 28 Oct 2022
Cited by 3 | Viewed by 1804
Abstract
The utilization of condensate water as a compressor-discharge cooler results in subcooling on the condenser outlet. On the other hand, a split-type air conditioner (A/C) with R32 as working fluid can provide higher compressor-discharge temperatures than other refrigerants used in the same A/C. [...] Read more.
The utilization of condensate water as a compressor-discharge cooler results in subcooling on the condenser outlet. On the other hand, a split-type air conditioner (A/C) with R32 as working fluid can provide higher compressor-discharge temperatures than other refrigerants used in the same A/C. Therefore, A/C working with R32, equipped with a heat exchanger by utilizing waste-condensate water as the compressor-discharge cooler, has promising potential to produce the largest subcooling effect in air-conditioning systems. The aim of this study is to investigate the effect of condensate water as the compressor-discharge cooler on the performance of an A/C using R32 as the working fluid with different sizes of heat exchanger. The experimental study was carried out on the A/C with a compressor capacity of 1.1 kW, using three different heat-exchanger lengths, i.e., 18, 20 and 22 cm. The results indicated that longer heat exchangers produced higher degrees of subcooling; the heat exchangers with lengths of 18, 20 and 22 cm produced average degrees of subcooling of 0.9, 1.5 and 4.5 K, respectively. Therefore, increments in the degree of subcooling generate improvements in cooling capacity, lowering the compressor-input power, and enhance the COP of the A/C. The average COP improvement of the A/C with heat-exchanger lengths of 18, 20 and 22 cm were 9.1, 14.4 and 27.3%, respectively. Full article
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9 pages, 2297 KiB  
Article
The Role of the Compressor Isentropic Efficiency in Non-Intrusive Refrigerant Side Characterization of Transcritical CO2 Heat Pump Water Heaters
by Francisco B. Lamas and Vítor A. F. Costa
Clean Technol. 2022, 4(3), 815-823; https://doi.org/10.3390/cleantechnol4030050 - 17 Aug 2022
Viewed by 2643
Abstract
Characterizing the refrigerant side of heat pump water heaters (HPWHs) can be intrusive and expensive. On the other hand, direct external measurement techniques can be unfeasible, particularly in commercial HPWHs for residential applications. Non-intrusive in situ characterization methods have already been successfully implemented [...] Read more.
Characterizing the refrigerant side of heat pump water heaters (HPWHs) can be intrusive and expensive. On the other hand, direct external measurement techniques can be unfeasible, particularly in commercial HPWHs for residential applications. Non-intrusive in situ characterization methods have already been successfully implemented in subcritical heat pumps. They provide the refrigerant mass flowrate and the equipment energy performance, by using contact temperature sensors and electric power meters. Subcritical suction and discharge-specific enthalpies necessary to apply the method can be obtained from the measured temperatures and their corresponding saturation pressures. Nevertheless, this approach does not apply to the transcritical CO2 HPWHs. In the supercritical region, temperature and pressure are independent variables, and an iterative process regarding the compressor isentropic efficiency has to be considered. However, when isentropic efficiency data are not available, an additional procedure is required, using a validated gas cooler model to verify the physical reliability of the numerical solutions. This work aims at presenting base thermodynamic analysis of a novel methodology for non-intrusive refrigerant side characterization of transcritical CO2 HPWHs, exploring the influence of the compressor isentropic efficiency condition. Full article
(This article belongs to the Special Issue Synergistic Technologies to Advance in Sustainable Refrigeration)
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17 pages, 4606 KiB  
Article
Performance Optimizations of the Transcritical CO2 Two-Stage Compression Refrigeration System and Influences of the Auxiliary Gas Cooler
by Yuyao Sun, Jinfeng Wang and Jing Xie
Energies 2021, 14(17), 5578; https://doi.org/10.3390/en14175578 - 6 Sep 2021
Cited by 6 | Viewed by 3037
Abstract
To optimize the performance of the transcritical CO2 two-stage compression refrigeration system, the energy analysis and the exergy analysis are conducted. It is found that higher COP, lower compression power, and less exergy destruction can be achieved when the auxiliary gas cooler [...] Read more.
To optimize the performance of the transcritical CO2 two-stage compression refrigeration system, the energy analysis and the exergy analysis are conducted. It is found that higher COP, lower compression power, and less exergy destruction can be achieved when the auxiliary gas cooler is applied. Moreover, the discharge temperature of the compound compressor (HPS) can be reduced by decreasing the temperature at the outlet of the auxiliary gas cooler (Tagc,out). When the Tagc,out is reduced from 30 to 12 °C, the discharge temperature of the compound compressor (HPS) can be decreased by 13.83 °C. Furthermore, the COP and the exergy efficiency can be raised by enhancing the intermediate pressure. Based on these results, the optimizations of system design and system operation are put forward. The application of the auxiliary gas cooler can improve the performance of the transcritical CO2 two-stage compression refrigeration system. Operators can decrease the discharge temperature of the compound compressor (HPS) by reducing the Tagc,out, and increase the COP and the exergy efficiency by enhancing the intermediate pressure. Full article
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13 pages, 3639 KiB  
Article
Coupling Effect of Air Flow Rate and Operating Conditions on the Performance of Electric Vehicle R744 Air Conditioning System
by Anci Wang, Jianmin Fang, Xiang Yin, Yulong Song, Feng Cao and Paride Gullo
Appl. Sci. 2021, 11(11), 4855; https://doi.org/10.3390/app11114855 - 25 May 2021
Cited by 2 | Viewed by 2233
Abstract
The air flow rate on the gas cooler side is one of the key parameters affecting the performance and running safety of transcritical CO2 electric vehicle air conditioning systems. After experimentally analyzing the effects of the air volume flow rate in the [...] Read more.
The air flow rate on the gas cooler side is one of the key parameters affecting the performance and running safety of transcritical CO2 electric vehicle air conditioning systems. After experimentally analyzing the effects of the air volume flow rate in the gas cooler on the cycle parameters and system performance, a novel method to evaluate the optimal air flow rate was proposed. In addition, the effect of the gas cooler air volume flow rate on the key performance parameters of the system (e.g., optimal discharge pressure) was explored. Finally, the coupling effects of the compressor speed, ambient temperature and optimal air flow rate on the system performance was also exhaustively assessed. It was found that as the discharge temperature, the CO2 temperature at the gas cooler outlet and the discharge pressure did not vary more than ±2%, the corresponding gas cooler air volume flow rate was optimal. For the single-row and dual-process microchannel evaporator used in this work, the recommended value of the optimal gas cooler air volume flow rate was 2500 m3·h−1. The results could provide reference for the fan speed design of electric vehicle CO2 air conditioning systems, especially for the performance under idling model. Full article
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13 pages, 2725 KiB  
Article
Energetic and Exergetic Analysis of a Transcritical N2O Refrigeration Cycle with an Expander
by Ze Zhang, Yu Hou and Francis A. Kulacki
Entropy 2018, 20(1), 31; https://doi.org/10.3390/e20010031 - 18 Jan 2018
Cited by 6 | Viewed by 5057
Abstract
Comparative energy and exergy investigations are reported for a transcritical N2O refrigeration cycle with a throttling valve or with an expander when the gas cooler exit temperature varies from 30 to 55 °C and the evaporating temperature varies from −40 to [...] Read more.
Comparative energy and exergy investigations are reported for a transcritical N2O refrigeration cycle with a throttling valve or with an expander when the gas cooler exit temperature varies from 30 to 55 °C and the evaporating temperature varies from −40 to 10 °C. The system performance is also compared with that of similar cycles using CO2. Results show that the N2O expander cycle exhibits a larger maximum cooling coefficient of performance (COP) and lower optimum discharge pressure than that of the CO2 expander cycle and N2O throttling valve cycle. It is found that in the N2O throttling valve cycle, the irreversibility of the throttling valve is maximum and the exergy losses of the gas cooler and compressor are ordered second and third, respectively. In the N2O expander cycle, the largest exergy loss occurs in the gas cooler, followed by the compressor and the expander. Compared with the CO2 expander cycle and N2O throttling valve cycle, the N2O expander cycle has the smallest component-specific exergy loss and the highest exergy efficiency at the same operating conditions and at the optimum discharge pressure. It is also proven that the maximum COP and the maximum exergy efficiency cannot be obtained at the same time for the investigated cycles. Full article
(This article belongs to the Special Issue Phenomenological Thermodynamics of Irreversible Processes)
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