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%.

scholarly journals Experimental Analysis of Refrigeration Ejector System by using Different Organic Refrigerants

2021 ◽  
Vol 9 (VII) ◽  
pp. 281-288
Author(s):  
P. V. Wakchaure
Keyword(s):  
Experimental Analysis ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Optimum Operating ◽  
Working Fluid ◽  
Cfd Simulations ◽  
Evaporator Temperature ◽  
Optimum Operating Condition ◽  
Condenser Temperature ◽  
Ejector System

This paper presents the experimental analysis performed on ejectors to optimize operating conditions like evaporator temperature, condenser temperature and generator temperature. Using the environmentally friendly working fluid R134a, R152a, R600a, R717 (Ammonia). Parametric analysis was performed to review the effect of blending chamber geometry on ejector performance which has direct impact on coefficient of performance of ejector refrigeration cycles. Results show that operating conditions and thus the effect of the deflection of the primary flow on the secondary flow is set. CFD simulations was performed to identify optimum geometry and optimum operating condition

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.

Environment Friendly Mixed Refrigerant to Replace R-134a in a VCR System with Exergy Analysis

2014 ◽  
Vol 984-985 ◽  
pp. 1174-1179
Author(s):  
N. Austin ◽  
P.M. Diaz ◽  
D.S. Manoj Abraham ◽  
N. Kanthavelkumaran
Keyword(s):  
Global Warming ◽  
Global Warming Potential ◽  
Ozone Depletion ◽  
Exergy Analysis ◽  
Coefficient Of Performance ◽  
Refrigeration System ◽  
Evaporator Temperature ◽  
Environment Friendly ◽  
A Charge ◽  
Vapour Compression

Study on environment friendly mixed refrigerant to replace R134a in vapour compression refrigeration (VCR) System. The mixed refrigerants investigated are propane (R290), butane (R600), isobutene (R600a) and R134a. Even though the ozone depletion potentials of R134a relative to CFC-11 are very low; the global warming potentials are extremely high and also expensive. For this reason, the production and use of R134a will be terminated in the near future. Hydrocarbons are free from ozone depletion potential and have negligible global warming potential. The results showed that, mixed refrigerant with charge of 80 g satisfy the required freezer air temperature when R134a with a charge of 110 g is used as refrigerant. The actual COP of refrigerator using mixed refrigerant was almost nearer that of the system using R134a as refrigerant. The coefficient of performance of the vapour compression refrigeration system using mixed refrigerant MR-3 [R134a/R290/ R600a/ R600 (20/35/40/5)] is having very close value with R134a and the Global warming potential of MR-3 is negligible when compared with R134a. Hence the mixed refrigerant MR-3 is chosen as an environmental friendly alternate refrigerant to R134a. The exergy analysis of the vapour compression refrigeration system using R134a and all the above mixtures are investigated. The effect of evaporator temperature on exergy efficiency and exergy destruction ratio of the system are experimentally studied. The exergy defect in the compressor, condenser, expansion device and evaporator are also obtained. Key words: R134a, Mixed refrigerant, Chlorofluorocarbons, Propane, Butane, Isobutene, REFPROP, COP, ODP, GWP, Exergy, VCR System.

scholarly journals Thermodynamic Analysis of a CO2 Refrigeration Cycle with Integrated Mechanical Subcooling

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 4 ◽  
Author(s):  
Laura Nebot-Andrés ◽  
Daniel Calleja-Anta ◽  
Daniel Sánchez ◽  
Ramón Cabello ◽  
Rodrigo Llopis
Keyword(s):  
Thermodynamic Analysis ◽  
Internal Heat ◽  
Cooling Capacity ◽  
Point Of View ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Optimum Operating ◽  
Refrigeration Cycle ◽  
Internal Heat Exchanger ◽  
Promising Solution

Different alternatives are being studied nowadays in order to enhance the behavior of transcritical CO2 refrigeration plants. Among the most studied options, subcooling is one of the most analyzed methods in the last years, increasing cooling capacity and Coefficient Of Performance (COP), especially at high hot sink temperatures. A new cycle, called integrated mechanical subcooling cycle, has been developed, as a total-CO2 solution, to provide the subcooling in CO2 transcritical refrigeration cycles. It corresponds to a promising solution from the point of view of energy efficiency. The purpose of this work is to present, for the first time, thermodynamic analysis of a CO2 refrigeration cycle with integrated mechanical subcooling cycle from first and second law approaches. Using simplified models of the components, the optimum operating conditions, optimum gas-cooler pressure, and subcooling degree are determined in order to obtain the maximum COP. The main energy parameters of the system were analyzed for different evaporation levels and heat rejection temperatures. The exergy destruction was analyzed for each component, identifying the elements of the system that introduce more irreversibilities. It has been concluded that the new cycle could offer COP improvements from 11.7% to 15.9% in relation to single-stage cycles with internal heat exchanger (IHX) at 35 °C ambient temperature.

Dynamic Performance Investigation of Single-Effect NH3 + LiNO3 and NH3 + NaSCN Solar Cooling Cycles: A Case Study for Western Indian Climate

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Nishant Modi ◽  
Bhargav Pandya ◽  
Vinay Kumar ◽  
Jatin Patel
Keyword(s):  
Dynamic Performance ◽  
Operating Conditions ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Sodium Thiocyanate ◽  
Lithium Nitrate ◽  
Ambient Conditions ◽  
Evaporator Temperature ◽  
Water Storage Tank ◽  
Single Effect

Abstract This article compares the dynamic behavior of solar-assisted novel salt-based ammonia/sodium thiocyanate (NH3 + NaSCN) and ammonia/lithium nitrate (NH3 + LiNO3) single-effect absorption refrigeration cycles. An evacuated tube collector (ETC) is attached with fully mixed hot water storage tank to power the absorption system. Variations in ambient conditions are determined for Gujarat Region of India and their effects on absorption cycles are quantified throughout the days for the months of April to September. System performance is investigated and compared on terms of coefficient of performance (COP), refrigeration capacity, efficiency and solar COP (SCOP). At same operating conditions, it is found that the NH3 + LiNO3 cycle can achieve much lower evaporator temperature (−13.1 °C) then NH3 + NaSCN cycle (−7.5 °C) and maximum possible COP for NH3 + NaSCN cycle is 0.73 and 0.68 for NH3 + LiNO3 cycle. The working limit of NH3 + LiNO3 cycle is wide ranging and narrow for NH3 + NaSCN cycle due to high crystallization possibility. SCOP varies from 0.18 to 0.43 for NH3 + NaSCN cycle and 0.17 to 0.39 for NH3 + LiNO3 cycle over the period of 6 months. Based on these findings, the suitable working cycle is justified.

First and Second Law Analyses of Double Effect Parallel and Series Flow Direct Fired Absorption Cycles for Optimum Operating Parameters

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Md. Azhar ◽  
M. Altamush Siddiqui
Keyword(s):  
Volume Flow Rate ◽  
Minimum Energy ◽  
Lithium Bromide ◽  
Double Effect ◽  
Parallel Flow ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Optimum Operating ◽  
Liquefied Petroleum Gas ◽  
Flow Cycle

Thermodynamic analysis of double effect parallel and series flow direct fired absorption systems with lithium bromide–water has been carried out for different operating conditions. Temperatures in primary generator (Tg) and secondary generator (Tgs)/secondary condenser (Tcs) are optimized analytically using an iterative technique for maximum coefficient of performance (COP) and minimum energy required. A solution distribution ratio for a parallel flow cycle is also optimized. Source of energy used to drive the cycles is considered as compressed natural gas (CNG) and liquefied petroleum gas (LPG). Exergy destruction rate (EDR) in individual components as well as in the whole cycle along with volume flow rate of LPG and CNG is presented and compared. Results show that maximum COP for the parallel flow cycle is 3–6% higher than the series flow cycle. Also, minimum EDR of the parallel flow cycle is around 4% less while energy consumption is 2–3% low as compared to the series flow cycle.

Thermodynamic analysis of triple effect ammonia–water absorption compression (hybrid) cycle

2021 ◽  
pp. 095440892199568
Author(s):  
CP Jawahar
Keyword(s):  
Water Absorption ◽  
Energy Analysis ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Performance Parameters ◽  
Evaporator Temperature ◽  
Ammonia Water ◽  
Absorption Cycle ◽  
Hybrid Cycle

This paper presents the energy analysis of a triple effect absorption compression (hybrid) cycle employing ammonia water as working fluid. The performance parameters such as cooling capacity and coefficient of performance of the hybrid cycle is analyzed by varying the temperature of evaporator from −10 °C to 10 °C, absorber and condenser temperatures in first stage from 25 °C to 45 °C, degassing width in both the stages from 0.02 to 0.12 and is compared with the conventional triple effect absorption cycle. The results of the analysis show that the maximum cooling capacity attained in the hybrid cycle is 472.3 kW, at 10 °C evaporator temperature and first stage degassing width of 0.12. The coefficient of performance of the hybrid cycle is about 30 to 65% more than the coefficient of performance of conventional triple effect cycle.

scholarly journals Enzymatic Transesterification of Waste Frying Oil from Local Restaurants in East Colombia Using a Combined Lipase System

2020 ◽  
Vol 10 (10) ◽  
pp. 3566
Author(s):  
Mary Angélica Ferreira Vela ◽  
Juan C. Acevedo-Páez ◽  
Nestor Urbina-Suárez ◽  
Yeily Adriana Rangel Basto ◽  
Ángel Darío González-Delgado
Keyword(s):  
Reaction Time ◽  
Methyl Esters ◽  
Enzyme Concentration ◽  
Operating Conditions ◽  
Frying Oil ◽  
Biodiesel Production ◽  
Optimum Operating ◽  
Waste Frying Oil ◽  
Production Chain ◽  
Enzymatic Transesterification

The search for innovation and biotechnological strategies in the biodiesel production chain have become a topic of interest for scientific community owing the importance of renewable energy sources. This work aimed to implement an enzymatic transesterification process to obtain biodiesel from waste frying oil (WFO). The transesterification was performed by varying reaction times (8 h, 12 h and 16 h), enzyme concentrations of lipase XX 25 split (14%, 16% and 18%), pH of reaction media (6, 7 and 8) and reaction temperature (35, 38 and 40 °C) with a fixed alcohol–oil molar ratio of 3:1. The optimum operating conditions were selected to quantify the amount of fatty acid methyl esters (FAMEs) generated. The highest biodiesel production was reached with an enzyme concentration of 14%, reaction time of 8 h, pH of 7 and temperature of 38 °C. It was estimated a FAMEs production of 42.86% for the selected experiment; however, best physicochemical characteristics of biodiesel were achieved with an enzyme concentration of 16% and reaction time of 8 h. Results suggested that enzymatic transesterification process was favorable because the amount of methyl esters obtained was similar to the content of fatty acids in the WFO.

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