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.

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 Verification of WRF modelled fire weather in the 2009–10 New Zealand fire season

2014 ◽  
Vol 23 (1) ◽  
pp. 34 ◽  
Author(s):  
C. C. Simpson ◽  
H. G. Pearce ◽  
A. P. Sturman ◽  
P. Zawar-Reza
Keyword(s):  
New Zealand ◽  
Weather Conditions ◽  
Model Error ◽  
Dew Point ◽  
Fire Season ◽  
Fire Weather ◽  
Fire Weather Index ◽  
Wind Speeds ◽  
Air Temperatures ◽  
Weather Stations

The Weather Research and Forecasting (WRF) mesoscale model was used to simulate the fire weather conditions for the 2009–10 wildland fire season in New Zealand. The suitability of WRF to simulate the high-end fire weather conditions for this period was assessed through direct comparison with observational data taken from 23 surface and two upper-air stations located across New Zealand. The weather variables and fire weather indices considered in the verification were the 1200 hours NZST air temperature, relative humidity, wind speed and direction, 24-h rainfall, New Zealand Fire Weather Index (FWI) and Continuous Haines Index (CHI). On observed high-end fire weather days, the model under-predicted the air temperatures and relative humidities, and over-predicted the wind speeds and 24-h rainfall at most weather stations. The results demonstrated that although WRF is suitable for modelling the air temperatures, there are issues with modelling the wind speeds and rainfall quantities. The model error in the wind speeds and 24-h rainfall contributed significantly towards the model under-prediction of the FWI on observed high-end fire weather days. In addition, the model was not suitable for predicting the number of high-end fire weather days at most weather stations, which represents a serious operational limitation of the WRF model for fire management applications. Finally, the modelled CHI values were only in moderate agreement with the observed values, principally due to the model error in the dew point depression at 850hPa.

scholarly journals Exergetic performance analysis of low GWP alternative refrigerants for R404A in a refrigeration system

2021 ◽  
Author(s):  
Mehmet Altinkaynak
Keyword(s):  
Cooling System ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Refrigeration System ◽  
Alternative Refrigerants ◽  
Condenser Temperature ◽  
Parametric Analyses ◽  
Low Global Warming Potential ◽  
Very High

Abstract According to the regulation of European Union laws in 2014, it was inevitable to switch to low global warming potential (GWP) fluids in the refrigeration systems where the R404A working fluid is currently used. The GWP of R404A is very high, and the potential for ozone depletion is zero. In this study, energetic and exergetic performance assessment of a theoretical refrigeration system was carried out for R404 refrigerant and its alternatives, comparatively. The analyses were made for R448A, R449A, R452A and R404A. The results of the analysis were presented separately in the tables and graphs. According to the results, the cooling system working with R448A exhibited the best performance with a coefficient of performance (COP) value of 2.467 within the alternatives of R404A followed by R449A and R452A, where the COP values were calculated as 2.419 and 2.313, respectively. In addition, the exergy efficiencies of the system were calculated as 20.62%, 20.22% and 19.33% for R448A, R449A and R452A, respectively. For the base calculations made for R404A, the COP of the system was estimated as 2.477, where the exergy efficiency was 20.71%. Under the same operating conditions, the total exergy destruction rates for R404A, R448A, R449A and R452A working fluids were found to be 3.201 kW, 3.217 kW, 3.298 kW and 3.488 kW, respectively. Furthermore, parametric analyses were carried out in order to investigate the effects of different system parameters such as evaporator and condenser temperature.

scholarly journals Performance of Commercially Open Refrigerated Showcases with and without Ice Storage—A Case Study

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 683
Author(s):  
Kai-Shing Yang ◽  
Yun-Sheng Chao ◽  
Chia-Hsing Hsieh ◽  
Min-Lun Chai ◽  
Chi-Chuan Wang
Keyword(s):  
Peak Power ◽  
Storage System ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Ice Storage ◽  
Air Cooling ◽  
Refrigeration System ◽  
Temperature And Pressure ◽  
Immersion Type

This study examines the applicability of the ice storage systems in the small commercial refrigerated showcases through experimental analysis. R-404A is used as the working fluid and various influence of parameter settings and improvements, are discussed in details. In the ice storage system, the condenser is changed from air-cooling (refrigeration mode) to an immersion type that is placed in an ice storage tank, the corresponding condensing temperature and pressure are reduced appreciably. This increased the efficiency and can effectively reduce the peak power consumption. The reduction of the condensing temperature and pressure increased the coefficient of performance (COP) from 3.6 (refrigeration mode) to 6.35 (melting mode), effectively enhancing the refrigeration efficiency. The results indicated that the ice storage system could effectively increase the coefficient of performance from 3.6 to 6.35 during ice melting when compared to the conventional refrigeration system. It also can shift approximately 35% of the power during peak hours and lower the energy cost by USD$ 17.13 per month.

Study on the Hybrid Liquid Desiccant Evaporative Cooling Air-Conditioning Refrigeration Circulation System

2012 ◽  
Vol 516-517 ◽  
pp. 1250-1256 ◽  
Author(s):  
Liu Xiong
Keyword(s):  
Air Conditioning ◽  
Evaporative Cooling ◽  
Coefficient Of Performance ◽  
Circulation System ◽  
Refrigeration System ◽  
Conventional System ◽  
Liquid Desiccant ◽  
Two Stage ◽  
Cooling Air ◽  
New System

This article presents a new hybrid evaporative cooling air-conditioning refrigeration system using two-stage liquid desiccant, and carries off the theoretical study on it. Compared with the conventional liquid desiccant air-conditioning refrigeration system, the new system adopts direct mixing heat transfer technology and evaporative cooling technology instead of water-cooled or air-cooled technology. Thus the cooling water usage is reduced. Using the two-stage adiabatic absorber and using refrigerant rather than water as the cooling medium of desiccant solution, the pressure difference of mass transfer is increased. Compared with the conventional system, the heat of regenerating solution is decreased because the mass ratio of air to desiccant solution is increased which gives rise to the decline of solution's mass rate. The results of theoretical calculation show that the new system has the better performance in power consumption, usage of water and equivalent coefficient of performance than the conventional system.

Thermodynamic, Economic, and Environmental Comparison Between the Direct and Indirect CO2 Refrigeration Cycle With Conventional Indirect NH3 Cycle With Considering a Heat Recovery System in an Ice Rink: A Case Study

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Hossien Momeni ◽  
Mohammad Mehdi Keshtkar
Keyword(s):  
Heat Recovery ◽  
Second Law Of Thermodynamics ◽  
Recovery Process ◽  
Coefficient Of Performance ◽  
Refrigeration System ◽  
Recovery System ◽  
Heat Recovery System ◽  
Industrial Refrigeration ◽  
Selection Of

In industrial refrigeration systems, such as ice rinks, because of consumption of a lot of energy, the selection of a refrigeration system is very important. At this work, environmental considerations are combined with thermodynamics and economics for the comparison of three different refrigeration systems in an ice rink, including the NH3/brine, CO2/brine, and full CO2. The first law of thermodynamics is used to calculate the system's coefficient of performance (COP) and the second law of thermodynamics is applied to quantify the exergy destructions in each component of a refrigeration system. With regard to the above, the exergy efficiency and energy consumption of the systems are determined by taking into account the heat recovery process that has been performed in the above-mentioned cycles. The results indicate that if a heat recovery system has been used in the refrigeration system, coefficient of performance of full CO2 refrigeration system is 33% higher than the CO2/brine and 66% greater than the NH3/brine system. The results also show that, whatever the refrigeration evaporating temperature in the NH3/brine system reaches lower than −12.4 °C, the total cost of this system will be greater than the full CO2 system.

scholarly journals Case study of liquid suction heat exchanger in a mechanical refrigeration system using alternative refrigerants

2020 ◽  
Vol 9 (3) ◽  
pp. 644
Author(s):  
Raid Ahmed Mahmood
Keyword(s):  
Heat Exchanger ◽  
System Performance ◽  
Good Alternative ◽  
High Response ◽  
Coefficient Of Performance ◽  
Alternative Refrigerant ◽  
Refrigeration System ◽  
Alternative Refrigerants

This paper investigates the effect of adding a liquid-suction heat exchanger on the performance of a mechanical refrigeration system using alternative refrigerants. Engineering Equation Solver (EES) was used to simulate a mechanical refrigeration system in two configurations: modified system with liquid-suction heat exchanger and system without liquid-suction heat exchanger. The results revealed that the liquid-suction heat exchanger has a significant effect on the system performance as it influences the subcooling and superheating temperatures. The results also showed that the highest value of the coefficient of performance (COP) was achieved by the modified system with refrigerant type R134a, COP was about 7% and 12% higher than that of refrigerants R600a and R22 respectively. It also presented that R600a has high response to increase the refrigerant effect when the liquid-suction heat exchanger is used. R600a is good alternative refrigerant and it can be used in the mechanical refrigeration system, but its COP is lower than that of R134a.  

Vulnerability of sweet cherry cultivars to continuous periods of spring frosts in Plovdiv, Bulgaria

2020 ◽  
Vol 12 (4) ◽  
pp. 348-352
Author(s):  
S. Malchev ◽  
S. Savchovska
Keyword(s):  
Sweet Cherry ◽  
Weather Conditions ◽  
Frost Damage ◽  
Cold Weather ◽  
Bud Burst ◽  
Intermediate Group ◽  
Air Temperatures ◽  
Wide Range ◽  
Group Form ◽  
Sweet Cherry Cultivars

Abstract. The periods with continuous freezing air temperatures reported during the spring of 2020 (13 incidents) affected a wide range of local and introduced sweet cherry cultivars in the region of Plovdiv. They vary from -0.6°C on March 02 to -4.9°C on March 16-17. The duration of influence of the lowest temperatures is 6 and 12 hours between March 16 and 17. The inspection of fruit buds and flowers was conducted twice (on March 26 and April 08) at different phenological stages after continuous waves of cold weather conditions alternated with high temperatures. During the phenological phase ‘bud burst’ (tight cluster or BBCH 55) some of the flowers in the buds did not develop further making the damage hardly detectable. The most damaged are hybrid El.28-21 (95.00%), ‘Van’ (91.89%) and ‘Bing’ (89.41%) and from the next group ‘Lapins’ (85.98%) and ‘Rosita’ (83.33%). A larger intermediate group form ‘Kossara’ (81.67%), ‘Rozalina’ (76.00%), ‘Sunburst’ (75.00%), ‘Bigarreau Burlat’ (69.11%) and ‘Kuklenska belitza’ (66.67%). Candidate-cultivar El.17-90 ‘Asparuh’ has the lowest frost damage values of 55.00% and El.17-37 ‘Tzvetina’ with damage of 50.60%.

Sediment transport under dry weather conditions in a small sewer system

1998 ◽  
Vol 37 (1) ◽  
pp. 155-162
Author(s):  
Flemming Schlütter ◽  
Kjeld Schaarup-Jensen
Keyword(s):  
Sediment Transport ◽  
Field Data ◽  
Field Measurements ◽  
Weather Conditions ◽  
Sewer System ◽  
Transport Models ◽  
Sewer Systems ◽  
Combined Sewer ◽  
Initial Results

Increased knowledge of the processes which govern the transport of solids in sewers is necessary in order to develop more reliable and applicable sediment transport models for sewer systems. Proper validation of these are essential. For that purpose thorough field measurements are imperative. This paper renders initial results obtained in an ongoing case study of a Danish combined sewer system in Frejlev, a small town southwest of Aalborg, Denmark. Field data are presented concerning estimation of the sediment transport during dry weather. Finally, considerations on how to approach numerical modelling is made based on numerical simulations using MOUSE TRAP (DHI 1993).

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