Performance Investigation of Flat Plate and Evacuated Tube Collectors under Jordan Climate Conditions Using TRNSYS Software Mohammed Al-Odat 1* , Khalida Rawashedsh 1 , Mohammed Al-Hasan 2 1 Department of Mechanical Engineering, Al-Huson University College, Al-Balqa Applied University, P.O. Box: 50 Al-Huson 21510, Jordan 2 Department of Mechanical Engineering, Faculty of Engineering Technology, Al-Balqa Applied University, P.O. Box: 15008 Amman 11134, Jordan Corresponding Author Email: m.odat@bau.edu.jo https://doi.org/10.18280/mmep.080118 ABSTRACT Received: 15 October 2020 Accepted: 23 December 2020 The performance of the Flat Plate Collector (FPC) and Evacuated Tube Collector (ETC) for domestic hot water applications under Jordan climate conditions was theoretically investigated using TRNSYS software. The presented simulation model can provide a long-term evaluation of system performance at different weather conditions. This simulation was carried out during 24 hours in 21 June, is considered as a hot climate and 21 January is considered as a cold climate; under the meteorological conditions of both Irbid and Aqaba cities in Jordan. The inlet water temperature of the first collector, collector area, water flow rate and tilt angle were considered 15℃, 2.04 m 2 , 0.0139 kg/s and 45 degrees respectively. The outlet temperature of each collector was considered as the inlet of the previous collector. Three collectors in series were applied to increase the output temperature up to 90-100℃. The results showed that TE increased with the decrease in the inlet temperature, which means the useful energy gain (Qu) of the first collector is greater than the 2 nd and the 3 rd collector. The useful energy gain (Qu) of ETC is greater than of FPC, and the useful energy gain (Qu) of cold climate is less than hot climate. The output temperature of ETCs is greater than that of FPCs for Irbid city in cold and hot climate. Furthermore, for Aqaba in cold climate and in hot climate the outlet temperature of ETCs is higher than FPCs. Additionally, the daily thermal performance of the ETCs is significantly better than the FPCs in cold climate. Meanwhile, thermal performance of both collectors are close in a hot climate. Keywords: flat plate collectors, evacuated tube collectors, TRNSYS-16 software, thermal efficiency, useful energy gain 1. INTRODUCTION Thermal solar energy is produced by converting sunlight into heat. Thermal collectors implement to collect solar energy to heat water; their main types are the flat plate collectors (FPC) and evacuated tube collectors (ETC). The act of both types is based on climate conditions and absorber characteristics. The absorber is flat and incorporates tubes, receives the solar radiation and transfer the heat to water which circulates within the tubes [1]. The ETC designed as a single- phase open thermosyphon (SPOT) or two-phase closed thermosyphon (TPCT), their pipes are insulated. Both are worked with the natural [2, 3] or enforced flow by using the pump [4] in domestic - scale applications [5-9]. The thermosyphon flow designed for SPOT consists of two concentric tubes (borosilicate glass) with a small space [5, 8]. The inner space between the two pipes is evacuated that which leads to decrease convection heat losses and improves efficiency. The outside of the inner tube is carried out with a special black coating to increase the rate of absorption and decreases the heat losses [10]. Evacuated tubes provide greater daily heat output as a result of the shape of cylindrical absorber which is perpendicular to the radiation of solar. The cold water passes within the inner tube and absorbs the heat then becomes hot and flows up subsequently this is displaced by cold water inflow from a storage tank. The TPCT consists of a tube of borosilicate glass and another metallic tube (typically copper), both are sealed. The working fluid flows within the metallic tube. The metallic tube consists of two sections; the lower section is an evaporator and the upper section is a condenser. the working fluid vaporizes and rises to the upper section and replaced the cold fluid, the vapor in the upper section, after a very short resident time, condenses then falls in the liquid pool at the lower section due to gravity. The water in the storage tank absorbs released the latent heat which is released during the condensing process. Perers [11] carried out a comparison of performance for FPCs and ETC, he concluded that the best performance has produced near 400 kWh/ (m 2 year) by ETC and 300 kWh/m 2 by FPC at a temperature of 60C. Morrison et al. [12] investigated the performance of both collectors and found that ETC has higher efficiency than FPC at temperatures above 100℃. The FPCs depended on two essentials: A black absorbing, transport medium (fluid tubes) that welded or integrated to the absorbing plate and a glass cover uses to prevent heat losses [13]. The FPC can either glazed or unglazed, the glazed type has a glass cover above the absorber that suitable for applications up to 70℃. While the unglazed collector has an absorber without cover that suitable for the low-temperature applications. The black plat absorbs the solar radiation and transports the heat to a fluid that passes in tubes; the fluid carried the heat to a storage tank. The underside of Mathematical Modelling of Engineering Problems Vol. 8, No. 1, February, 2021, pp. 142-148 Journal homepage: http://iieta.org/journals/mmep 142