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An experimental investigation of the performance of a commercially available vapor absorption refrigeration (VAR) system is described. The natural gas-fired VAR system uses aqua-ammonia solution with ammonia as the refrigerant and water as the absorbent and has a rated cooling capacity of 10 kW. The unit was extensively modified to allow fluid pressures and temperatures to be measured at strategic points in the system. The mass flow rates of refrigerant, weak solution, and strong solution were also measured. The system as supplied incorporates air-cooled condenser and absorber units. Water-cooled absorber and condenser units were fitted to extend the VAR unit's range of operating conditions by varying the cooling water inlet temperature and/or flow rates to these units. The response of the refrigeration system to variations in chilled water inlet temperature, chilled water level in the evaporator drum, chilled water flow rate, and variable heat input are presented. (C) 2003 Elsevier Ltd and IIR. All rights reserved.

The determination of the cooling capacity and overall heat transfer coefficient of an evaporator is of great importance in refrigeration industry, so that, an investigation of the theoretical and experimental performance analysis of evaporators was carried out in this study. The experimental evaporator was analyzed in account with the most common and widely used correlations together with the parameters of air velocity, fin spacing, tube diameter, evaporator temperature, refrigerant type and frost height. After a good agreement between the experimental and theoretical results was obtained, the parameters which had not been able to investigated experimentally were analyzed theoretically. It is concluded that when the experimental and theoretical overall heat transfer coefficients were compared with those from the manufacturing catalogues (for the same working conditions), the latter was found to be 15-30% higher than the former one. (C) 1998 Elsevier Science Ltd.

Absorption Heat Transformer (AHT) systems are devices with the unique capability of raising the temperature of low or moderately warm waste heat sources to more useful levels. The study includes an investigation to analyze the AHT systems using water-lithium bromide solutions with water as the refrigerant. First, a basic AHT system was described, the operating sequence was explained and thermodynamic system analysis was presented. Next, an application of the AHT system to an industrial company was analyzed. A computer code was prepared to determine the effect of different parameters on the AHT system performance and the results were presented in graphical form. Additionally, it was shown that how the basic AHT system could be modified to increase the COP and the heat transfer at the absorber, in other words, the hot process water produced. The system performance data were presented in a tabular form for different system modifications from the base system for comparison. It was proven that, by applying different modifications, the COP could be increased by 14.1%, the heat transfer at the absorber by 158.5% and the hot process water produced by 3.59% compared to the basic ANT system. (c) 2010 Elsevier Ltd. All rights reserved.

An industrial application of the single stage and double absorption heat transformer (AHT) systems using water-lithium bromide solutions with water as the refrigerant was analyzed. First, a basic single stage AHT system was described, the operating sequence was explained and thermodynamic system analysis was presented. Next, an application of the single stage AHT system to an industrial company was analyzed. A computer code was prepared to determine the effect of different parameters on the AHT system performance and the results were presented in graphical form. Additionally, the series and parallel double absorption AHT systems were introduced, the operating sequences were explained and thermodynamic system analysis was included. All results were presented in tabular form for comparison. It is concluded that about 50% of the waste heat can be utilized and the hot process water and vapor could be produced by applying single stage and double AHT systems, respectively. The parallel double AHT system could generate more vapor than the series double AHT system. Copyright (C) 2009 John Wiley & Sons, Ltd.

This study concentrates on the absorber used in the vapor absorption systems using water-lithium bromide solution with water as the refrigerant and investigates the simultaneously occurred heat and mass transfer during the absorption process. The heat and mass transfer equations were applied to simulate this process and solved using a computer program written in Delphi 7 for the parallel and counter flow absorbers. The simulation results were compared with the results of the past studies. The solution and cooling water temperatures, the overall heat transfer coefficient, the heat transferred and the mass absorbed were calculated for the parallel and counter flow absorbers. It is concluded that the counter flow absorber presents better performance for all conditions. For smaller number of coils, the difference is smaller, however if the number of coils is bigger, the counter flow absorber presents much better performance than the parallel flow absorber. When the number of coils is 20 and 120, the counter (low absorber provides 1.7% and 26% higher heat and mass transfer than the parallel flow absorber respectively. 2005 Elsevier Ltd. All rights reserved.

The study included an investigation to analyze the Vapor Absorption Refrigeration (VAR) systems using ammonia-water and water-lithium bromide solutions. A fundamental VAR system is described and the operating sequence is explained. Since the most common VAR systems use ammonia-water solution with ammonia as the refrigerant and water-lithium bromide solution with water as the refrigerant, the comparison of the two is presented in respect of the coefficient of performance (COP), the cooling capacity and the maximum and minimum system pressures. It is concluded that the VAR system using water-lithium bromide solution provided better performance than the system using ammonia-water solution. However, there are some points to be considered such as; the danger of crystallization and impossibility of operating in very low temperatures because of the use of water as the refrigerant. (C) 1998 Elsevier Science Ltd.