A thermodynamic evaluation on high pressure condenser of double effect absorption refrigeration system _ Ibrahim Halil Yılmaz a , Kenan Saka b , Omer Kaynakli c, * a Department of Automotive Engineering, Adana Science and Technology University, Adana, Turkey b Department of Air Conditioning and Refrigeration, Vocational School of Yenis ¸ ehir _ Ibrahim Orhan, University of Uluda g, Bursa, Turkey c Department of Mechanical Engineering, University of Uluda g, Bursa, Turkey article info Article history: Received 19 March 2016 Received in revised form 1 June 2016 Accepted 25 July 2016 Keywords: Double effect absorption Water/lithium bromide High pressure condenser Low pressure generator Performance evaluation Irreversibility abstract One of the parameters affecting the COP of the absorption system can be considered as the thermal balance between the high pressure condenser (HPC) and the low pressure generator (LPG) since heat rejected from the HPC is utilized as an energy source by the LPG. Condensation of the water vapor in the HPC depends on the heat removal via the LPG. This circumstance is significant for making an appropriate design and a controllable system with high performance in practical applications. For this reason, a thermodynamic analysis for the HPC of a double effect series flow water/lithium bromide absorption refrigeration system was emphasized in this study. A simulation was developed to investigate the energy transfer between the HPC and LPG. The results show that the proper designation of the HPC temperature improves the COP and ECOP due its significant impact, and its value necessarily has to be higher than the outlet temperature of the LPG based on the operating scheme. Furthermore, the COP and ECOP of the absorption system can be raised in the range of 9.72e35.09% in case of 2  C-temperature increment in the HPC under the described conditions to be applied. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction In recent years, energy security and related issues have oriented us to heed the energy recovery and efficiency for thermal systems. Renewable source and waste heat utilization impress the science communities for the sake of insuring energy sustainability and curbing carbon emissions. Absorption refrigeration systems pro- vide many distinctions from those points in cooling operations but have lower coefficient of performance (COP) relative to its coun- terparts. In order to improve the COP of these systems or adapt them to any source of energy, various modifications to the cycle configurations have been proposed [1e3]. Multi-effect cycles have higher COP values relative to the basic configurations however they require higher source temperature with increasing the effect number [4] and increased number of heat exchanger. On the other hand, raising the effect number is not energy effective alone when the system components are not operated in a suitable operational domain. It has been a primary challenge for the researchers to increase the COP of the absorption refrigeration systems to a sig- nificant degree. At this point, a theoretical analysis provides a wealth of information on the expected operational characteristic of the system and its performance. Yet, it fundamentally includes some assumptions or approximations to simplify the analysis which in turn can yield some pitfalls while not holding the physical nature of the system. Thus a realistic system analysis helps to deliver admissible outputs which serve to predict the system behavior and performance under different scenarios. Double effect absorption system, as its name implies, utilizes double-generator; high, and low pressure which in turn provide heat recovery and improvement of the COP. In double effect series flow absorption systems, it is required the entire vapor generated at the high pressure generator (HPG) to be fully condensed via the low pressure generator (LPG). This is achieved in the practical systems by installing a throttling device which allows forming the condensate in high pressure condenser (HPC) of the absorption system, and thus the noncondensate is restricted there not to be escaped to the condenser as in the vapor form [5]. At this stage, the LPG adjusts itself somehow to come to an equilibrium temperature while furnishing the complete condensation at the HPC. The eval- uation of this circumstance at the design stage of the multi-effect absorption systems is crucial to sustain maximum possible heat * Corresponding author. E-mail addresses: iyilmaz@adanabtu.edu.tr (H. Yılmaz), kenansaka@uludag.edu. tr (K. Saka), kaynakli@uludag.edu.tr (O. Kaynakli). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy http://dx.doi.org/10.1016/j.energy.2016.07.133 0360-5442/© 2016 Elsevier Ltd. All rights reserved. Energy 113 (2016) 1031e1041