DOI 10.1515/jnet-2015-0001 | J. Non-Equilib. Thermodyn. 2015; aop Research Article Vahid Madadi*, Hamid Beheshti, Touraj Tavakoli and Amir Rahimi Experimental study and first thermodynamic law analysis of a solar water heater system Abstract: The performance of a pilot scale flat plate solar water heater system is investigated theoretically and experimentally. The effect of the operating conditions and characteristic factors of the collector on the system efficiency is studied. A conceptual mathematical model is developed in order to analyze the system behavior in different operating conditions by considering the physical and constructive aspects of the system. The accuracy of the model result is estimated by comparing the model results with the existing experimental data. The highest obtained system thermal efficiency is 45%, and the optimum local values for surface azimuth and tilt angles are obtained at 180 degrees from north and 33 degrees, respectively, for the constructed solar water heater in Isfahan, Iran, with the local latitude of 32.6333 ∘ N. Keywords: Solar water heater, flat plate collector, tilt angle, azimuth angle, mathematical modeling || *Corresponding author: Vahid Madadi: Department of Chemical Engineering, Faculty of Engineering, Yasouj University, P.O. Box 75914-353, Yasouj, Iran, e-mail: vmadadi64@yu.ac.ir Hamid Beheshti: Department of Mechanical Engineering, Faculty of Engineering, University of Isfahan, P.O. Box 81746-73441, Isfahan, Iran, e-mail: hamid.beheshti@eng.ui.ac.ir Touraj Tavakoli, Amir Rahimi: Department of Chemical Engineering, Faculty of Engineering, University of Isfahan, P.O. Box 81746-73441, Isfahan, Iran, e-mail: ttavakoli@eng.ui.ac.ir, rahimi@eng.ui.ac.ir 1 Introduction Nowadays, due to the presumable depletion of the fossil fuel resources that contribute to air pollution, more research is conducted on solar energy utility as a more environment-friendly source. Up to now, solar water heaters have been studied by many researchers. In many types of solar water heaters the tubes carrying the water are installed at the back of the absorber plate. In the solar water heaters in which the tubes are improvised to the back of the absorber plate, the solar energy is transmitted from the glass cover into the collector space and then into the involved air at front of the absorber plate and the tem- perature of absorber plate and air is rising simultaneously. In this case the inlet water warms by conductive heat transfer mechanism between the absorber plate and surface of the tubes at the binding sites. The rate of heat transfer by conduction is weak and the total gain of solar energy is low. In the present study, the tubes are located in front of the absorber plate into the pent space and solar irradiance is trans- ferred to the tubes by three mechanisms. The convective heat transfer occurs between the warmed air in the collector space and surface of the tubes. Also, the solar irradiance is absorbed directly by the tube’s surface. Furthermore, the heat exchange between the absorbing plate and the tubes occurs by conduction and radia- tion mechanisms. Souliotis et al. [1] studied the performance of a prototype Integrated Collector Storage (ICS) by applying a combination of suitable Artificial Neural Network (ANN) and TRNSYS. They collected experimental data from outdoor tests of an ICS solar water heater with cylindrical water storage tank inside a CPC reflector. They used their developed ANN incorporated in TRNSYS to model the annual performance of the system for the values of a typical meteorological year for Athens. The effectiveness of this approach was proved for such predictions. A test setup was made and experiments were performed to investigate these aspects under laboratory conditions by Sekhar et al. [2]. There were certain parameters that affected the temperature of the plate such as: type of flow inside the tube, solar insulation, ambient temperature, top heat loss coefficient, the emissivity of the plate and glass cover, slope, etc. Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 7/22/15 2:56 PM