Proceedings of the International Conference on Mechanical Engineering and Renewable Energy 2015 (ICMERE2015) 26 – 29 November, 2015, Chittagong, Bangladesh ICMERE2015-PI-224 © ICMERE2015 1. INTRODUCTION Heat exchangers are devices that facilitate heat transfer between two or more fluids at different temperature. Many types of heat exchanger have been developed for using at varied levels of technological sophistication and water to water heat exchanger is one of them. A heat exchanger can be defined as any device that transfers heat from one fluid to another or from or to a fluid and the environment. Whereas in direct contact heat exchangers, there is no intervening surface between fluids, in indirect contact heat exchangers, the customary definition pertains to a device that is employed in the transfer of heat between two fluids or between a surface and a fluid [1]. Various heat exchanger applications are available such as boiler, condenser, water heater, automobile radiator or cooling coil, refrigeration, air conditioning etc. Hence, analysis of different heat exchangers has become a prime concern in heat transfer science. Different types of classification of heat exchangers available in engineering practice are widely discussed on Froas and Ozisik [2] Walker [3] and Kakac, Shah, and Bergles [4]. Heat exchangers can be classified based on the transfer process, compactness, construction type, flow arrangement and heat transfer mechanism [5], [6]. Heat exchanger performance is one of the most vital term in heat research field because of its vast range of applications. Numerous researches have been done already about the performance of heat exchanger. Dubey et al. [7] investigated the performance of a shell and tube type heat exchanger under the effect of varied operation condition was analyzed and it was seen that the computational results were almost same compared with the experimental results. Kara et al. [8] made a computer based design model for a shell-tube heat exchanger. In that exchanger single phase fluid flows on both shell and tube side. According to the conclusion of that paper, circulating cold fluid in shell side and hot fluid in tube side is advantageous. The heat transfer characteristics of a tube-tube heat exchanger (TTHE) was conducted by Rane et al. [9]. Work of Lunsford [10] is very informative in increasing the heat exchanger efficiency. Yao et al. [11] conducted an experiment on heat transfer enhancement of water to water shell and tube heat exchanger assisted by power ultrasonic. Alam et al. [12] investigated the heat transfer characteristics of an air to water heat exchanger both numerically and experimentally. Nevertheless, there were a few researches done on water to water heat exchanger and as a matter of fact numerous researches are being conducted on the heat transfer characteristics of the heat exchangers. In this experimental study the heat transfer characteristics of a water to water heat exchanger were determined experimentally. Increasing the heat transfer efficiency and plotting the temperature profiles for the parallel and counter flow heat exchanger is one of the most important concern regarding the enhancement of heat transfer auxiliaries in heat transfer science. Abstract- Heat exchanger is a device that transfers heat from one fluid to another or from or to a fluid and the environment. The heat transfer characteristics, logarithmic mean temperature difference (LMTD), heat exchanger efficiency were determined experimentally of a water to water tube heat exchanger in this investigation. In this case, heat transfer took place between water to water at different temperatures and the respective features were determined for parallel and counter flow arrangement. Readings of different temperatures at different sections of the tube heat exchanger were taken and temperature profiles of the parallel and counter flow were plotted using the experimental data. It was observed that, the overall heat transfer coefficient and heat exchanger efficiency for counter flow was almost 10% and 20% greater than that of the parallel flow heat exchanger. Hence, counter flow heat exchanger arrangement proved to be more advantageous for greater heat recovery. Keywords: Water to water heat exchanger, Parallel flow, Counter flow, Heat transfer characteristics, Temperature profiles Investigation of Heat Transfer Characteristics of a Water to Water Heat Exchanger: An Experimental Approach S. M. Mahbobur Rahman 1 , Kazi Ehsanul Karim 2 and MD. Hasan Shahriar Simanto 3 1-3 Department of Mechanical Engineering, Khulna University of Engineering & Technology, Khulna-9203, Bangladesh 1 mahboburr6@gmail.com * , 2 kaziehsanul45@gmail.com, 3 hs.simanto@gmail.com