Analysis of annual energy savings in air conditioning using different heat pipe heat exchanger configurations integrated with and without evaporative cooling T.S. Jadhav a, * , M.M. Lele b a Research Centre, Sinhgad COE, Pune and SOPRIM, National Institute of Construction, Management and Research, Pune, 411045, Maharashtra, India b Department of Mechanical Engineering, MAEER's MIT College of Engineering, Pune, 411038, Maharashtra, India article info Article history: Received 29 January 2016 Received in revised form 28 March 2016 Accepted 4 May 2016 Keywords: Heat pipe heat exchanger Water Air conditioning Evaporative cooling Energy savings abstract The three HPHX (heat pipe heat exchanger) configurations in the present investigation include HPHX with single wick structure (HPHX 1), HPHX with composite wick structure (HPHX 2) and hybrid HPHX (HPHX 3) which is the combination of HPHX 1 and HPHX 2. The experimental correlations obtained are used for investigating annual energy savings in air conditioning using HPHX integrated with and without evaporative cooling, for Indian climatic zones. A representative city for each Indian climatic zone is selected for the analysis involving sensible heat recovery between outdoor air and conditioned return air. The investigation reveals that for HPHX without evaporative cooling, HPHX 1 becomes favourable choice for cities such as Bengaluru (representing temperate Indian climatic zone), Chennai (warm and humid Indian climatic zone) and Guwahati (cold Indian climatic zone). For cities such as Ahmedabad (hot and dry Indian climatic zone), Gwalior (composite Indian climatic zone) and Chennai, the use of HPHX in- tegrated with evaporative cooling is found more promising for HPHX 3 followed by HPHX 2, whereas for cities such as Bengaluru and Guwahati, HPHX 1 becomes the popular choice. The present research gives an insight towards the performance and selection of HPHX with different configurations, for Indian climatic zone. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction With increasing demand in air conditioning, the use of heat recovery devices such as HPHX (heat pipe heat exchanger) becomes significant for achieving better energy savings. Among the many outstanding advantages of using the heat pipe as a heat trans- mission device are constructional simplicity, exceptional flexibility, accessibility to control and ability to transport heat at high rate over considerable distance with extremely small temperature drop [1].A literature review is conducted to investigate the work done by the past researchers in energy saving analysis using heat pipe for air conditioning applications. In the earlier investigations the authors [2] have studied the theoretical energy saving analysis of air con- ditioning system using HPHX for Indian climatic zones. The analysis was carried out for total 25 Indian cities representing different Indian climatic zones. The maximum energy saving potential was revealed for hot and dry, warm and humid and composite Indian climatic zones. In the present study, the experimental correlation for each HPHX configuration is used to estimate the actual energy saving analysis in air conditioning system using HPHX integrated with and without evaporative cooling. A representative city for each Indian climatic zone is considered for the analysis involving only sensible heat recovery between outdoor air and conditioned return air. G.D. Mathur [3] investigated the impact of HPHX on the energy consumption and the peak demand of an existing air con- ditioning system. A detailed performance investigation was carried out by using the climate conditions for St. Louis, Missouri for year round operation of the HVAC system with HPHX. J.W. Wan et al. [4] investigated the effect of heat pipe on energy consumption in a central air-conditioning system. The study indicated that a central air conditioning system can significantly reduce its energy con- sumption and improve both the indoor thermal comfort and air quality when HPHX is employed in the air conditioning process. Y.H. Yau and M. Ahmadzadehtalatapeh [5] studied the effect of an air-to-air heat pipe heat exchanger on the energy recovery and * Corresponding author. Tel.: þ91 20 66859307; fax: þ91 20 27390057. E-mail addresses: tushar01031978@gmail.com (T.S. Jadhav), anuman7@gmail. com (M.M. Lele). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy http://dx.doi.org/10.1016/j.energy.2016.05.017 0360-5442/© 2016 Elsevier Ltd. All rights reserved. Energy 109 (2016) 876e885