ISSN: 2319-8753 International Journal of Innovative Research in Science, Engineering and Technology Vol. 2, Issue 5, May 2013 Copyright to IJIRSET www.ijirset.com 1570 PERFORMANCE ANALYSIS OF PARALLEL FLOW SINGLE AND DOUBLE EFFECT ABSORPTION CYCLES Mohammad Seraj 1 , M. Altamush Siddiqui 2 Assistant Professor, Department of Mechanical Engineering, Mangalayatan University, Aligarh, India 1 Professor, Department of Mechanical Engineering, Aligarh Muslim University, Aligarh, India 2 Abstract: Thermodynamic analysis of parallel flow single and double effect LiBr-H 2 O absorption system has been carried out. In the single effect cycle, the refrigerant leaving the evaporator is divided to flow in parallel and get absorbed partly in a heat recovery absorber and the remaining in a heat rejecting absorber. This reduces heat load of the generator to a great extent and hence, improves COP of the cycle. Similarly in the double effect parallel flow cycle, the solution leaving the absorber is divided into two parts, one being sent to the main generator and the other to the secondary generator. Such type of arrangement in the double effect system increases COP of the cycle as compared to the series flow cycle. The refrigerant distribution ratio (RDR) in the single effect refrigerant-parallel flow cycle and the solution distribution ratio (SDR) in the double effect solution-parallel flow cycle have been optimized. The optimization results, corresponding to the maximum COP, yield: RDR=0.30 and SDR=0.45. A comparative study between the single effect simple cycle, single effect cycle using heat recovery absorber, double effect parallel flow cycle and double effect series flow cycle has been presented. The analysis has been done by varying evaporator temperature (T e ) from 5 o C to 12.5 o C and condenser/absorber temperature (T c ) from 30 o C to 40 o C. Keywords: Parallel Flow, Double Effect, LiBr-H 2 O, Absorption Cycles I. INTRODUCTION The absorption refrigeration system utilizes non CFC’s natural refrigerant and is therefore, more environment-friendly. Also, it consumes less electricity and uses waste heat/low grade energy for its operation. Most of the absorption cooling system use either LiBr-H 2 O or NH 3 -H 2 O solutions. The LiBr-H 2 O system can operate at a low generator temperature with better coefficient of performance than NH 3 -H 2 O system. However, COP of absorption system is relatively less as compared to the compression system. Therefore, research is in progress and several modifications have been made in the cycle to improve its performance. Asdrubali and Grignaffini [1] experimentally verified the performance of single-stage LiBr-H 2 O absorption machine. Optimization of the generator temperature in H 2 O-NH 3 , LiNO 3 -NH 3 , NaSCN-NH 3 and LiBr-H 2 O absorption cycles have been carried out by Siddiqui [2] for minimum cost of the energy sources: (biogas, LPG and solar collector). Gommed and Grossman [3] investigated the performance of single effect cycle and various configuration of double- effect absorption refrigeration cycle using LiBr-H 2 O pair, under varying operating conditions. Lee and Sheriff [4] presented the second law analysis of various double effect LiBr-H 2 O absorption chillers for a chilled water temperature of 7.22°C and cooling water temperatures at 29.4 and 35°C. Khaliq and Kumar [5] examined a double-effect vapour absorption refrigeration system. Arun et al. [6] compared the performance of double-effect LiBr-H 2 O absorption system and found that the maximum attainable COP for parallel flow cycle is greater than for the series flow cycle. Oh et al. [7] have carried analysis on air-cooled LiBr-H 2 O absorption heat pump of parallel flow double effect system. They have suggested the possible optimum range of Solution Distribution Ratio (SDR) as 0.35-0.4 for Δx=4% (Δx= difference of LiBr salt concentration in the solution entering and leaving the absorber). Xu and Dai [8] have conducted analysis and optimization of double effect parallel flow type absorption chiller and suggested that the system operation is safe when the SDR is close to 0.5. Wang et al. [9] have presented analysis of gas-fired air-cooled parallel flow double effect LiBr-H 2 O system. They have simulated the system for some specific parameters and suggested the value of SDR=0.418. Kaushik and Kumar [10] and Kandlikar[11] have carried thermodynamic study on an absorber heat recovery cycle. Saghiruddin and Siddiqui [12,13] performed economic analyses of some sources of energy for operating single effect absorption cycles with and without heat recovery absorber. Use of a heat recovery absorber improves the system performance and reduces the energy cost. In the analysis carried out by Saghiruddin and Siddiqui [12,13], the Refrigerant Distribution Ratio (RDR) in the heat recovery absorber has been simply considered as 0.5; although the COP varies with change in the value of the RDR.