A Parametric Study on a Subcritical CO2/NH3 Cascade Refrigeration System for Low Temperature Applications

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Baris Yilmaz ◽  
Ebru Mancuhan ◽  
Nasuh Erdonmez
Keyword(s):  
Performance Analysis ◽  
Large Scale ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Optimum Operating ◽  
Second Law Analysis ◽  
The Common ◽  
Cascade Refrigeration System ◽  
Cascade Refrigeration ◽  
Thermo Physical Properties

Adverse effects of synthetic refrigerants on the environment have led to replacing them with natural refrigerants. The common candidates are ammonia, carbon dioxide, and several hydrocarbon compounds and their mixtures. Ammonia has been used mainly in large-scale cooling purposes such as large-scale supermarkets and climatic rooms. However, in such systems, leakage of ammonia may arise severe results on human health and may damage products in the cooled space. Recently, in last decade, a well-known refrigerant, CO2, has gained more attention to be applied in refrigeration systems due to having prominent thermo-physical properties. The performance analysis of a CO2/NH3 cascade (CAS) system has been theoretically examined in the current study. The detailed performance analysis of the system and optimization of the operating parameters have been studied extensively. In addition, the second-law analysis of the system with both cycles has been performed. Optimum operating conditions of the system are also determined and correlations are developed. Finally, the coefficient of performance (COP) correlations developed by several researchers in literature and those of current study are compared against available experimental COP results. The comparisons showed that the proposed correlations can be utilized for the accurate prediction of the COP of a cascade CO2/NH3 system within the studied range of operating conditions.

scholarly journals Heat Exchanger Network Synthesis Integrated with Compression–Absorption Cascade Refrigeration System

Processes ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 210 ◽  
Author(s):  
Xiaojing Sun ◽  
Linlin Liu ◽  
Yu Zhuang ◽  
Lei Zhang ◽  
Jian Du
Keyword(s):  
Heat Exchanger ◽  
Waste Heat ◽  
Coefficient Of Performance ◽  
Mixed Integer ◽  
Total Annual Cost ◽  
Network Synthesis ◽  
Refrigeration System ◽  
Operating Condition ◽  
Cascade Refrigeration System ◽  
Cascade Refrigeration

Compression–absorption cascade refrigeration system (CACRS) is the extension of absorption refrigeration system, which can be utilized to recover excess heat of heat exchanger networks (HENs) and compensate refrigeration demand. In this work, a stage-wise superstructure is presented to integrate the generation and evaporation processes of CACRS within HEN, where the generator is driven by hot process streams, and the evaporation processes provide cooling energy to HEN. Considering that the operating condition of CACRS has significant effect on the coefficient of performance (COP) of CACRS and so do the structure of HEN, CACRS and HEN are considered as a whole system in this study, where the operating condition and performance of CACRS and the structure of HEN are optimized simultaneously. The quantitative relationship between COP and operating variables of CACRS is determined by process simulation and data fitting. To accomplish the optimal design purpose, a mixed integer non-linear programming (MINLP) model is formulated according to the proposed superstructure, with the objective of minimizing total annual cost (TAC). At last, two case studies are presented to demonstrate that desired HEN can be achieved by applying the proposed method, and the results show that the integrated HEN-CACRS system is capable to utilize energy reasonably and reduce the total annualized cost by 38.6% and 37.9% respectively since it could recover waste heat from hot process stream to produce the cooling energy required by the system.

Optimization Process of a Visi-Cooler Using Ternary Mixtures of R134a and Hydrocarbons

2017 ◽  
Vol 25 (02) ◽  
pp. 1750019 ◽  
Author(s):  
Srinivas Pendyala ◽  
Ravi Prattipati ◽  
A V Sita Rama Raju
Keyword(s):  
Ozone Depletion ◽  
Operating Conditions ◽  
Ternary Mixtures ◽  
Coefficient Of Performance ◽  
Optimum Operating ◽  
Taguchi Technique ◽  
Capillary Length ◽  
Evaporator Temperature ◽  
Safe Limit ◽  
Air Conditioning Systems

Ozone depletion and global warming phenomenon necessitates the replacement of widely used refrigerants which consist of chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) in refrigeration and air-conditioning systems. In this paper, experimental analysis on the performance of hydrofluorocarbon/hydrocarbon (HFC/HC) mixture as a possible drop-in replacement for R134a refrigerant is presented. The influence of capillary length, composition of the mixture and refrigerant charge at various evaporator temperatures on coefficient of performance (COP) are investigated. The optimum operating conditions are obtained by applying Taguchi technique for the acquired experimental results. The results of analysis of variance indicated that for a given evaporator temperature, HFC/HC mixture charge amount is the most influencing parameter. At the optimum condition, the simulation showed that the amount of charge required for HFC/HC mixture in visi-cooler is 120[Formula: see text]g which is 50% lower than required quantity of R134a for the same system. The HC mixture quantity amounted to 90[Formula: see text]g in the HFC/HC mixture which is lower than the safe limit of 150[Formula: see text]g. This eliminates the risk of flammability of HC in the proposed mixture while reducing the quantity of R134a by 87.5%.

Energetic, Exergetic, Environmental, and Economic Assessment of a Cascade Refrigeration System Operating with Four Different Ecological Refrigerant Pairs

2021 ◽  
pp. 2150025
Author(s):  
Cleison Henrique de Paula ◽  
Willian Moreira Duarte ◽  
Thiago Torres Martins Rocha ◽  
Raphael Nunes de Oliveira ◽  
Antônio Augusto Torres Maia
Keyword(s):  
Coefficient Of Performance ◽  
Maintenance Cost ◽  
Temperature Cycle ◽  
Refrigeration System ◽  
Cascade System ◽  
Cost Rate ◽  
Total Plant ◽  
Cascade Refrigeration System ◽  
Cascade Refrigeration ◽  
System Operating

In this work, a cascade refrigeration system operating with four different ecological refrigerant pairs was modeled. This system uses R744 (Carbon dioxide) in the low-temperature cycle and operates with R290 (propane), R1234yf (2,3,3,3-tetrafluoropropene), R152a (1,1-difluorethane), and R717 (ammonia) in the high-temperature cycle. Energetic, exergetic, environmental, and economic performance of the cascade system was investigated to determine the most appropriate ecological refrigerant couple. The parameters used in each mentioned performance were COP (Coefficient of Performance), [Formula: see text] (Exergy Efficiency), TEWI (Total Equivalent Warming Impact), ECOP (Ecological coefficient of performance), and [Formula: see text] (Total plant cost rate), respectively. The results showed that the cascade refrigeration system operating with R744/R717 provided the best performance for the thermodynamic conditions analyzed, presenting a COP of 2.10, [Formula: see text] of 56.9%, [Formula: see text] of 24 334 USD/year, ECOP of 4.86, and TEWI of 25.67 tons of CO2. Finally, evaluating the total plant cost rate of this cascade system, it was noted that the capital and maintenance cost rate [Formula: see text] corresponds to 89.1% of the [Formula: see text] value, the operational cost rate [Formula: see text] corresponds to 10.27% of the [Formula: see text] value and the environmental cost rate [Formula: see text] corresponds to 0.63% of [Formula: see text].

scholarly journals COP enhancement of vapour compression refrigeration system using dedicated mechanical subcooling cycle

2020 ◽  
Vol 39 (3) ◽  
pp. 776-784
Author(s):  
T.S. Mogaji ◽  
A. Awolala ◽  
O.Z. Ayodeji ◽  
P.B. Mogaji ◽  
D.E. Philip
Keyword(s):  
System Performance ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Condensation Temperature ◽  
Refrigeration System ◽  
Wide Range ◽  
Cascade Refrigeration System ◽  
Cascade Refrigeration ◽  
Vapour Compression ◽  
Better Than

This study focused on development of an improved vapour compression refrigeration system (IVCR system). Dedicated mechanical subcooling cycle is employed in attaining the developed IVCR system. The system is composed of two cycles cascade refrigeration system working with R134a. It consists of a rectangular shape with total storage space of 0.582 m3, made of galvanized mild steel and internally insulated with 0.05 m polystyrene foam. Tests under a wide range operating temperature conditions were carried out on the developed IVCR system. Performance evaluation of the system was characterized in terms of cooling capacity and coefficient of performance (COP). Experimental results showed that the COP of the subcooled system improved better than that of the main system from 18.0% to about 33.5% over an evaporating temperature range of -10 to 30oC. It can be concluded that the use of dedicated sub cooling cycle in VCR system is more efficient and suitable for the betterment of thermal system performance. Keywords: Vapour compression Refrigeration system, Coefficient of performance, dedicated subcooled system, Condensation temperature, Evaporation temperature.

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