scholarly journals Steady-State Performance Prediction for a Variable Speed Direct Expansion Air Conditioning System Using a White-Box Based Modeling Approach

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4757
Author(s):  
Yudong Xia ◽  
Shu Jiangzhou ◽  
Xuejun Zhang ◽  
Zhao Zhang
Keyword(s):  
Steady State ◽  
Air Conditioning ◽  
Thermal Environment ◽  
Operating Performance ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Variable Speed ◽  
Direct Expansion ◽  
Expansion Valve ◽  
Fan Speed

When using a certain type of Heating, Ventilation & Air Conditioning (HVAC) systems, it is primary to obtain their steady-state operating behaviors for achieving a better indoor thermal environment. This paper reports a development of a white-box-based dynamic model for a direct expansion (DX) air conditioning (A/C) system to predict its steady-state operating performance under variable speed operation. The established model consists of five sub-models, i.e., a compressor, an electronic expansion valve, an evaporator, a condenser and a conditioned space. Each sub-model was developed based on partial lumped parameter approach. Using the available data generated from an experimental DX A/C system, both transient and steady-state behaviors predictions agreed well with the experimental ones. With the help of the validated white-box model, the inherent steady-state operating performance expressed in terms of the relationship among total cooling capacity (TCC), equipment sensible heat ratio (E SHR) and coefficient of performance (COP) under various speed combinations of compressor and supply fan were further examined. The results show that a higher COP could be achieved when the DX A/C system was operated at a higher fan speed or a lower compressor speed for dealing with a larger required E SHR. This model could be helpful for A/C system design and controller development.

Experimental analysis of the low-GWP refrigerant R1234yf as a drop-in replacement for R134a in a typical mobile air conditioning system

2012 ◽  
Vol 226 (11) ◽  
pp. 2713-2725 ◽  
Author(s):  
Yu Zhao ◽  
Zhaogang Qi ◽  
Jiangping Chen ◽  
Baixing Xu ◽  
Bin He
Keyword(s):  
Working Conditions ◽  
Air Conditioning ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Laminated Plate ◽  
Improve Performance ◽  
Air Conditioning System ◽  
Expansion Valve ◽  
Variable Displacement ◽  
Valve Opening

This study investigated the performance of a typical mobile air conditioning system using R134a and R1234yf as the working fluids under different working conditions. The system is composed of a microchannel parallel flow condenser, a laminated plate evaporator, a variable displacement compressor, and a thermal expansion valve. The different working cycles of each refrigerant were comprehensively compared. The optimum refrigerant charge amount of the R1234yf system was approximately 95% of the R134a system during drop-in tests. The performance of the R134a system was a little higher than that of the R1234yf system. The cooling capacity and system coefficient of performance of the R134a system were 12.4% and 9% larger, respectively. This result is mainly because of the thermophysical property differences between the two refrigerants and the improper expansion valve opening of R1234yf. Analysis on the whole cycle revealed that the R1234yf system could obtain a higher evaporating pressure and a larger superheat and subcooling. Redesigning the expansion valve for R1234yf could improve performance of the system.

Experimental Verification of a Universal Accumulator Heat Exchanger Design Procedure Used to Achieve Liquid Overfeeding Effects in Small Air Conditioning Systems

1999 ◽  
Author(s):  
Craig W. Wood ◽  
Josua P. Meyer
Keyword(s):  
Heat Exchanger ◽  
Experimental Verification ◽  
Air Conditioning ◽  
Pressure Ratio ◽  
Design Procedure ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Direct Expansion ◽  
Air Conditioning System ◽  
Heat Exchanger Design

Abstract This study involves the experimental verification of a universal heat exchanger accumulator design procedure. A heat exchange accumulator was manufactured according to a mathematical model developed by the authors and installed into a small air conditioning system. Experimental results show that the addition of the heat exchanger accumulator results in a liquid overfeeding operation that replaces the previously utilized direct expansion operation. It provides an improved air conditioning system that has a 7.5% increase in coefficient of performance and a 4.4% increase in refrigerant mass flow rate. A pressure ratio reduction has a positive effect on the compressor performance and life span. Liquid overfeeding increases the cooling capacity of the system by 6.5%. When compared to direct expansion systems, this basic heat exchanger accumulator provides a reduction in cycling losses and power consumption, an increase in suction pressure and an improvement in isentropic compressor efficiency.

scholarly journals Effects of compressor speed and electronic expansion valve opening on the performance of R410a water chiller system

2020 ◽  
Vol 8 (1) ◽  
pp. 12-20
Author(s):  
Ahmed H. Al-Hassani ◽  
Alaa R. Al-Badri
Keyword(s):  
Electrical Energy ◽  
Cooling Capacity ◽  
System Stability ◽  
Coefficient Of Performance ◽  
Rotary Compressor ◽  
Variable Speed ◽  
Global Power ◽  
Expansion Valve ◽  
Valve Opening ◽  
Air Conditioning Systems

Refrigeration and air conditioning systems consume high rates of electrical energy of the total global power consumption. The major part of this energy is used by compressor which is the main equipment in vapor compression refrigeration systems. In this study, the performance of a variable speed chilled water refrigeration system with electronic expansion valve (EEV) is experimentally investigated. The system is composed of variable speed rotary compressor, water cooled condenser, electronic expansion valve, and evaporator with refrigerant R410a for one tone cooling capacity. The results showed that the EEV opening was related to the compressor speed at limits of refrigerant subcool and system stability to achieve better performance. Refrigerant superheats increased with closing the EEV at constant compressor speed. Moreover, the degree of superheat was inversely proportional to the compressor speed at constant EEV opening. The coefficient of performance (COP) was improved by about 2.2 to 4.0% by controlling the EEV at constant compressor speed. Increasing compressor speed from 1200 to 3600 rpm resulted in decreasing system COP from 5.2 to 2.35 due to the increase of the power consumed by compressor.

scholarly journals KAJI PERFORMANSI REFRIGERAN R-290, R-32, DAN R-410A SEBAGAI ALTERNATIF PENGGANTI R-22

2021 ◽  
Vol 4 ◽  
pp. 133-139
Author(s):  
Rikhard Ufie ◽  
Cendy S. Tupamahu ◽  
Sefnath J. E. Sarwuna ◽  
Jufraet Frans
Keyword(s):  
Air Conditioning ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Condensation Temperature ◽  
Vapor Compression ◽  
Know How ◽  
Evaporation Temperature ◽  
Vapor Compression Cycle ◽  
Compression Cycle ◽  
Refrigeration Capacity

Refrigerant R-22 is a substance that destroys the ozone layer, so that in the field of air conditioning it has begun to be replaced, among others with refrigerants R-32 and R-410a, and also R-290. Through this research, we want to know how much Coefficient of Performance (COP) and Refrigeration Capacity (Qe) can be produced for the four types of refrigerants. The study was carried out theoretically for the working conditions of the vapor compression cycle with an evaporation temperature (Tevap) of 0, -5, and -10oC, a further heated refrigerant temperature (ΔTSH) of 5 oC, a condensation temperature (Tkond) of 45 oC and a low-cold refrigerant temperature. (ΔTSC) 10 oC and compression power of 1 PK . The results of the study show that the Coefficient of Performance (COP) in the use of R-22 and R-290 is higher than the use of R-32 and R-410a, which are 4,920 respectively; 4,891; 4.690 and 4.409 when working at an evaporation temperature of 0 oC; 4.260; 4,234; 4.060 and 3.812 when working at an evaporation temperature of -5 oC; and amounted to 3,730; 3,685; 3,550 and 3,324 if working at an evaporation temperature of -10 oC. Based on the size of the COP, if this installation works with a compression power of 1 PK, then the cooling capacity of the R-22 and R-290 is higher than the R-32 and R-410a, which are 3,617 respectively. kW; 3,597 kW; 3,449 kW and 3,243 kW. If working at an evaporation temperature of 0 oC; 3.133 kW; 3.114 kW; 2,986 kW and 2,804 kW if working at an evaporation temperature of -5 oC; and 2,741 kW; 2,710 kW; 2,611 kW and 2,445 kW if working at an evaporation temperature of -10oC.

scholarly journals Experimental and Theoretical Study on the Cooling Performance of a CO2 Mobile Air Conditioning System

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1927 ◽  
Author(s):  
Dandong Wang ◽  
Binbin Yu ◽  
Junye Shi ◽  
Jiangping Chen
Keyword(s):  
Air Conditioning ◽  
Theoretical Study ◽  
Cooling Capacity ◽  
Air Conditioning System ◽  
Cooling Performance ◽  
System A ◽  
Hfc 134A ◽  
Expansion Valve ◽  
The Impact ◽  
Compressor Efficiency

CO2 (GWP = 1) is considered as a promising natural alternative refrigerant to HFC-134a in mobile air conditioning (MAC) applications. The objective of this study is to investigate the cooling performance characteristics of a CO2 MAC system. A prototype CO2 MAC system, consisting of a CO2 electrical compressor, CO2 parallel flow microchannel heat exchangers, and an electrical expansion valve, was developed and tested. Factor analysis experiments were conducted to reveal the effect of outdoor temperature on the cooling performance of this CO2 MAC system. Compared with a conventional R134a MAC system, the prototype CO2 MAC system achieved comparable cooling capacity, but had COP reductions of 26% and 10% at 27 °C and 45 °C outdoor conditions, respectively. In addition, based on refrigerant properties, theoretical cycle analysis was done to reveal the impact of evaporator, gas cooler and compressor, on the system cooling performance. It is concluded that the increase of overall compressor efficiency or the decrease of gas cooler approaching temperature could greatly improve the COP of this CO2 MAC system.

scholarly journals Thermal Performance Analysis of Low-GWP Refrigerants in Automotive Air-Conditioning System

2020 ◽  
Vol 2020 ◽  
pp. 1-14 ◽  
Author(s):  
Yousuf Alhendal ◽  
Abdalla Gomaa ◽  
Gamal Bedair ◽  
Abdulrahim Kalendar
Keyword(s):  
Air Conditioning ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Exergy Destruction ◽  
Air Conditioning System ◽  
Capacity Coefficient ◽  
Automotive Air Conditioning ◽  
Automotive Air Conditioning System ◽  
Compressor Power ◽  
Low Global Warming Potential

The energy and exergy of low-global warming potential (GWP) refrigerants were investigated experimentally and theoretically. Refrigerants with a modest GWP100 of  ≤ 150 can be sufficient for bringing down emissions which were concerned for the automotive air-conditioning system. Three types of low-GWP refrigerants, R152a, R1234yf, and R1234ze(E), were examined with particular reference to the current high-GWP of R134a. The effect of different evaporating and condensing temperatures in addition to compressor speed was considered. The purpose was to bring a clear view of the performance characteristics of possible environment friendly alternatives of R134a. The analysis was carried out with compressor power, cooling capacity, coefficient of performance, exergy destruction, and exergy efficiency. It was noted that the total exergy destruction of R1234yf was reduced by 15% compared to that of R134a. The refrigerant R1234ze(E) has the highest energetic and exergetic performance compared with the other investigated refrigerants.

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