scholarly journals INVESTIGATING THE PERFORMANCE OF A TRANSCRITICAL BOOSTER REFRIGERATION SYSTEM WITHCARBON DIOXIDE IN TROPICAL CLIMATES: THE CASE OF BENIN

2021 ◽  
Vol 9 (02) ◽  
pp. 226-238
Author(s):  
Chegnimonhan K. Victorin ◽  
◽  
Aredokou Olorounto Louis ◽  
Guidi Tognon Clotilde ◽  
Adomou Alain ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Ambient Temperature ◽  
Weather Conditions ◽  
Coefficient Of Performance ◽  
Low Carbon ◽  
Refrigeration System ◽  
Ambient Temperatures ◽  
Transcritical Carbon Dioxide ◽  
A Prospective Study ◽  
Tropical Climates

This article presents a prospective study of low carbon footprint refrigeration systems in tropical climates. A transcritical carbon dioxide booster refrigeration system is simulated within the Engineering Equation Solver (EES) environment. The results are discussed under the weather conditions Cotonou, Benin. The performance of the transcritical booster cycle increases with low ambient temperatures the Coefficient of Performance (COP) increased by 94.2% when the ambient temperature went from 40°C to 25°C). The gas cooler pressure and the medium pressure were ctoptimised and two correlations were developed to predict the optimal gas cooler pressure and intermediate pressure for which the COP value is maximum. It should be noted that these pressures are very sensitive to changes in ambient temperature and they vary proportionally with the temperature at the end of cooling and in a linear fashion.

scholarly journals Performance Evaluation of a CO2 Refrigeration System Enhanced with a Dew Point Cooler

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1079 ◽  
Author(s):  
Martin Belusko ◽  
Raymond Liddle ◽  
Alemu Alemu ◽  
Edward Halawa ◽  
Frank Bruno
Keyword(s):  
Weather Conditions ◽  
Dew Point ◽  
Coefficient Of Performance ◽  
Experimental Program ◽  
Refrigeration System ◽  
Conventional System ◽  
Ambient Temperatures ◽  
Air Temperatures ◽  
Condenser Temperature

Dew point cooling (DPC) is a novel indirect evaporative cooling concept capable of delivering air temperatures approaching the dew point. Coupling this technology with CO2 refrigeration is well suited to minimising transcritical operation when the coefficient of performance (COP) is dramatically reduced in hot climates. A substantial experimental program was conducted to characterise this combination by testing a 20 kW CO2 refrigeration system subject to ambient temperatures above 40 °C. It was demonstrated that DPC operation not only avoided transcritical operation during such weather conditions, but also increased the COP by up to 140% compared to the conventional system. The combination of these technologies was successfully mathematically modelled, from which the optimum condenser inlet air temperature was identified for each condenser temperature. Using this optimum condition, it was possible to maximise the COP for a range of conditions applicable to the psychometric chart. An annual case study for Adelaide, Australia was conducted which demonstrated that optimally coupling DPC with CO2 refrigeration can reduce the annual energy consumption and peak demand by 16% and 47%, respectively, compared to a conventional CO2 booster system. Furthermore, the number of hours of transcritical operation was reduced from 3278 to 27.

Theoretical performance of transcritical carbon dioxide cycle with two-stage compression and intercooling

2005 ◽  
Vol 219 (2) ◽  
pp. 187-195 ◽  
Author(s):  
J. S. Baek ◽  
E. A. Groll ◽  
P. B. Lawless
Keyword(s):  
Carbon Dioxide ◽  
System Analysis ◽  
Coefficient Of Performance ◽  
System Efficiency ◽  
Compression Process ◽  
Two Stage ◽  
Bell Curve ◽  
Second Stage ◽  
Transcritical Carbon Dioxide ◽  
Theoretical Performance

A computer model was developed to perform a thermodynamic analysis of the transcritical carbon dioxide cycle with two-stage compression and intercooling. In typical two-stage compression with intercooling applications, the intercooler serves the purpose of cooling the fluid to the lowest possible temperature before it enters the second-stage compressor. This paper presents the results of the system analysis of the transcritical carbon dioxide cycle with two-stage compression and intercooling (intercooler cycle) and identifies the pressure ratios that provide maximum system efficiency. The results show that the coefficient of performance (COP), curves of the intercooler cycle are different from the ‘typical bell curve behaviours’ that are observed when plotting the COP versus the intermediate pressure with assumptions of isentropic and real compression process.

The Experimental Investigation and Theoretical Analysis on Transcritical Carbon Dioxide Heat Pump Cycle

2012 ◽  
Vol 455-456 ◽  
pp. 240-245
Author(s):  
Lu Xiang Zong ◽  
Jian Lin Liu ◽  
Xue Shi ◽  
Ying Bai Xie
Keyword(s):  
Carbon Dioxide ◽  
Experimental Investigation ◽  
Theoretical Analysis ◽  
Heat Pump ◽  
Coefficient Of Performance ◽  
Pump System ◽  
Working Fluids ◽  
Heat Pump System ◽  
Exit Temperature ◽  
Transcritical Carbon Dioxide

The (H)CFC-phase out and the fear for future problems for other synthetic working fluids, because of their known and unknown impact on the environment, have introduced a rising interest in environmentally safe natural working fluids. CO2is one of the few non-toxic and non-flammable working fluids that do not contribute to ozone depletion or global warming, if leaked to the atmosphere. Because the critical temperature of CO2is only 31.1°C, the transcritical cycle can be used to improve the coefficient of performance of the system. The experimental investigation and theoretical analysis on transcritical carbon dioxide heat pump system are carried out in this paper. It points out that there is an optimum operational pressure on transcritical carbon dioxide heat pump cycle, when the outlet temperature of gas cooler is constant, the coefficient of performance increases with increasing evaporating temperature at the same conditions, and the operational efficiency increased with decrease of gas cooler exit temperature. So in order to obtain the optimum performance, the influence of evaporating temperature, gas cooler exit temperature, and the operational pressure should be considered during the designing and operating transcritical carbon dioxide heat pump system.

scholarly journals An Optimal Air-Conditioner On-Off Control Scheme under Extremely Hot Weather Conditions

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1021 ◽  
Author(s):  
Mohammed Al-Azba ◽  
Zhaohui Cen ◽  
Yves Remond ◽  
Said Ahzi
Keyword(s):  
Ambient Temperature ◽  
Weather Conditions ◽  
Online Optimization ◽  
Coefficient Of Performance ◽  
Control Technique ◽  
Air Conditioner ◽  
Outdoor Temperature ◽  
Temperature Variations ◽  
Wide Range ◽  
Hot Weather

Being reliant on Air Conditioning (AC) throughout the majority of the year, desert countries with extremely hot weather conditions such as Qatar are facing challenges in lowering weariness cost due to AC On-Off switching while maintaining an adequate level of comfort under a wide-range of ambient temperature variations. To address these challenges, this paper investigates an optimal On-Off control strategy to improve the AC utilization process. To overcome complexities of online optimization, a Elman Neural Networks (NN)-based estimator is proposed to estimate real values of the outdoor temperature, and make off-line optimization available. By looking up the optimum values solved from an off-line optimization scheme, the proposed control solutions can adaptively regulate the indoor temperature regardless of outdoor temperature variations. In addition, a cost function of multiple objectives, which consider both Coefficient of Performance (COP), and AC compressor weariness due to On-Off switching, is designed for the optimization target of minimum cost. Unlike conventional On-Off control methodologies, the proposed On-Off control technique can respond adaptively to match large-range (up to 20 ∘ C) ambient temperature variations while overcoming the drawbacks of long-time online optimization due to heavy computational load. Finally, the Elman NN based outdoor temperature estimator is validated with an acceptable accuracy and various validations for AC control optimization under Qatar’s real outdoor temperature conditions, which include three hot seasons, are conducted and analyzed. The results demonstrate the effectiveness and robustness of the proposed optimal On-Off control solution.

scholarly journals Numerical analysis of transcritical carbon dioxide compression cycle: a case study

2018 ◽  
Vol 7 (1) ◽  
pp. 1 ◽  
Author(s):  
Mohammad Mehdi Keshtkar
Keyword(s):  
Carbon Dioxide ◽  
Coefficient Of Performance ◽  
Outlet Temperature ◽  
Two Stage ◽  
Change Of Variables ◽  
Compression Cycle ◽  
Transcritical Carbon Dioxide ◽  
Two Stages ◽  
Isentropic Efficiency

This study deals with thermodynamic investigation of a refrigeration compression cycle with carbon dioxide refrigerant and two stage compression. In this paper, the effect of intercooler in the two-stage compression system at different pressures of gas cooler is investigated. In addition, the performance of one stage compression cycle and two-stage compression cycle are compared and eventually, the performance of system is investigated under the influence of the change of variables such as gas cooler  pressure, isentropic efficiency of the compressors, the intercooling rate between the two stages of compression, the refrigerant gas cooler outlet temperature is examined. Due to evaporation temperature in the evaporator  and refrigeration capacity (kW) results show that the coefficient of performance in the two-stage compression with intercooler is increased compared to the single-stage compression cycle.

Thermodynamic Analysis of Transcritical Carbon Dioxide Cycles

2005 ◽  
Author(s):  
Mark Brown ◽  
Luis Rosario ◽  
Muhammad M. Rahman
Keyword(s):  
Carbon Dioxide ◽  
Thermodynamic Analysis ◽  
System Capacity ◽  
Coefficient Of Performance ◽  
Cycle Performance ◽  
Vapor Compression ◽  
Transcritical Carbon Dioxide ◽  
Compressor Power ◽  
Natural Refrigerant ◽  
Two Stages

Research on natural environmentally friendly refrigerants is very important especially because the world-wide agreement about restriction in the use of ozone depleting refrigerants. Carbon dioxide is a natural refrigerant that has been considered for certain refrigeration and air conditioning applications. The aim of this paper is to present a thermodynamic analysis of carbon dioxide cycles in order to evaluate the potential performance of a refrigeration cycle using carbon dioxide. A thermodynamic model for the cycle is developed which can simulate the operation of a carbon dioxide refrigeration/AC cycle. This model takes into account the practical effects of the thermo-physical properties of carbon dioxide as refrigerant in a trans-critical cycle. A sensitivity analysis has been conducted so that cycle performance is estimated. The cooling load, compressor power, and coefficient of performance (C.O.P.) were evaluated. One and two stages of compression were also considered for comparison purposes. Cycle performance was evaluated based on variation of important parameters such as evaporator, intermediate, and discharge pressures. The effects of cycle components on system capacity and cycle performance are also investigated. Comparison between performances of the CO2 cycle and the standard vapor compression cycle is performed. Thermodynamic calculations showed reasonable agreement with available experimental data based on the general assumptions made.

The Thermodynamic Analysis and Experimental Investigation on Transcritical Carbon Dioxide Heat Pump System

2010 ◽  
Author(s):  
Yingbai Xie ◽  
Yingfu Liu ◽  
Yingcheng Mai ◽  
Luxiang Zong
Keyword(s):  
Carbon Dioxide ◽  
Experimental Investigation ◽  
Heat Pump ◽  
Thermodynamic Analysis ◽  
Coefficient Of Performance ◽  
Pump System ◽  
Heat Pump System ◽  
Exit Temperature ◽  
Transcritical Carbon Dioxide ◽  
Critical Carbon Dioxide

Synthetic refrigerants such as CFCs and HCFCs deplete ozone and cause greenhouse effect. CO2 as a natural working fluid has zero Ozone Depletion Potential and its Global Warming Potential is equal to 1, is receiving more and more attention in the refrigeration field. Because the critical temperature of CO2 is only 31.1°c, the trans-critical cycle can be used to improve the coefficient of performance of the system. The thermodynamic analysis and experimental investigation on trans-critical carbon dioxide heat pump system are carried out in this paper. It points out that there is an optimum operational pressure on trans-critical carbon dioxide heat pump cycle, when the outlet temperature of gas cooler is constant, the coefficient of performance increases with increasing evaporating temperature at the same conditions, and the operational efficiency increased with decrease of gas cooler exit temperature. So in order to obtain the optimum performance, the influence of evaporating temperature, gas cooler exit temperature, and the operational pressure should be considered during the designing and operating transcritical carbon dioxide heat pump system.

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