Brief on solar concentrators: differences and applications International Journal of Energetica (IJECA) https://www.ijeca.info ISSN: 2543-3717 Volume 5. Issue 2. 2020 Page 01-06 IJECA-ISSN: 2543-3717. December 2020 Page 1 A small parabolic trough collector as a solar water heater: an experimental study in Ouargla region, Algeria Djamel Benmenine 1 , Mokhtar Ghodbane 2* , Mohammed Elbar Soudani 1 , Haffar Abdelouahed 1 , Amghar Massiv 1 , Nabil Elsharif 3 1 Laboratory for the Development of New and Renewable Energies in Arid Zones (LENREZA), University of Ouargla, ALGERIA 2 Mechanical Engineering Department, Faculty of Technology, University of Blida 1, ALGERIA 3 Mechanical Engineering Department, University of Benghazi, LIBYA * Email: ghodbannemokhtar39@yahoo.com Abstract – This study aims to conduct an experimental thermal examination of a parabolic trough collector in Ouargla region at Algeria, which will be used as a solar water heater. The solar collector was manufactured and then experimentally tested, as its theoretical optical performance was estimated at 75.06%, while the values of its true thermal performance are 10.61, 10.68 and 8.85 % for 13 May, 14 May and 15 May. Although its thermal performance is somewhat low, the studied PTC is effective in heating the water, whereas, using a volumetric flow of 0.011 l/s, about 317 liters of water can be heated daily at 42°C, knowing that the daily average consumption of hot water in a typical house is 250 liters because the Ouargla region is strategically located that receives huge amounts of solar irradiance. Keywords: thermal solar energy, PTC solar collector, solar water heater, solar energy. Received: 10/10/2020 – Accepted: 20/11/2020 I. Introduction Currently, the world is experiencing an important shift in energy production from fossil fuels to the exploitation of renewable energies, and precisely the solar energy that is expanding its use through the use of various solar collectors (photoelectric [1] and thermal collectors “flat [2], linear [3-6] and point collectors [7, 8]”), whereas, the efficiency of these solar collectors can be improved by dispersing nanoparticles in the working fluid [9-11], this will allow to improve its thermophysical properties [12-14]. Moreover, solar collectors have several important uses, including electricity production [15], water desalination [16-18], drying [19], cooking [20], air conditioning [21-24], heating [25-27], and industrial processes [7, 28]. Therefore, the use of solar collectors of all kinds can be an ideal solution to provide the energy needs of regions with abundant solar energy [29, 30].One of the most important uses of solar energy now is the heating of water, as solar heaters are a way to exploit the thermal energy generated from the sun's rays in heating water for home, industrial and commercial purposes, and these systems achieve a higher economic feasibility than solar photovoltaic energy, where the household electricity bill can be saved especially If the solar heater is connected to a hot water tank. Since the solar heater heats the water and stores it during the day for use throughout the day (24 hours), unlike the traditional (electric or gas) heater, which can heat at any time of day and night, the size of the solar heater tank is much larger than the traditional water heater tank [31- 32]. Through this paper, an experimental thermal examination of a solar water heater by adopting a parabolic trough collector (PTC) will be carried out in Ouargla region, Algeria, in order to provide hot water that can be used in many household uses, where in this study, the effect of the mass flow of water inside the receiver tube on the solar heater performance will be discussed. mailto:ghodbannemokhtar39@yahoo.com M. Ghodbane et al. IJECA-ISSN: 2543-3717. December 2020 Page 2 II. Materials and Methods The region of Ouargla (Algeria) with latitude 31 ° 58 'N, longitude 5 ° 20' E, altitude 150 m is known for its agricultural and industrial activity. The need for domestic hot water is generally provided by conventional energy. In our study, we propose a solar, environmental and economical method to obtain hot water for domestic use. II.1. PTC collector design Water PTC was manufactured by the research group on energy conversion of the LENREZA laboratory at Ouargla University (Algeria). Figure 1. The experimental prototype The engineering and optical properties of the experimental device are shown in Tables 1 and 2, respectively. Table 1 . PTC engineering properties Dimension Value Absorber tube diameter (inner) 0.0142 m Absorber tube diameter (outer) 0.016 m Focal length 0.2 m Glass diameter (inside) 0.0175 m Glass diameter (outer) 0.02 m Mirror length 2 m Mirror opening width 1.6 m Reflector opening area 2.88 m² The PTC was placed on two identical steel supports 1.25 m long oriented north-south so that the PTC can follow the movement of the sun from east to west. Table 2 . PTC optical properties Parameter Value Absorptivity of absorber tube 0.94 Emissivity of absorber tube 0.14 Emissivity of glass tube 0.935 Reflectivity of mirror 0.935 Transmittivity of glass tube 0.92 II.2. Measuring instruments For the determination of the instantaneous thermal behavior of the PTC, there are parameters must be measured. The various parameters measured and the measuring instruments used are: Temperatures: three calibrated K-type thermocouples were installed for temperature measurement on different parts of the PTC system, where the thermocouple locations are shown in Figure 2. Solar irradiance: as shown in Figure 2, a solarimeter with an accuracy of (±5%) was used to measure solar irradiation during the experiments. Figure 2. K-type thermocouples and solarimeter III. Results and Discussion III.1. Experimental set up As shown in Figure 3, the solar water heater is composed of a cold-water source, pump, small PTC solar collector and heated water tank, where the system is equipped with the following measuring devices: a solarimeter and three k-type thermocouples. Regarding thermocouples, they are placed as follow:  Tin: at the entrance to the PTC absorber tube to measure the cold-water temperature coming from the cold source;  Tout: at the outlet of the PTC absorber tube to measure the hot water temperature coming out of the PTC collector;  TAbs: to measure the absorber tube temperature. Figure 3. The experimental installation M. Ghodbane et al. IJECA-ISSN: 2543-3717. December 2020 Page 3 Several experiments were carried out in the open air behind the physics laboratories at Ouargla University for three days from 06/05/2019 until 09/05/2019. The PTC solar heater has been tested on the basis of three scenarios, and they are: First scenario The main axis of the PTC was directed from north to south in order to follow the solar movement from east to west with a manual tracking system, where the temperature of the water is measured when entering and leaving the PTC solar collector, as the water volumetric flow inside the receiver tube is constant ̇ and the effect of weather data for May 13, 2019 on the thermal behavior of the system. Second scenario In this scenario, which was completed on May 14, 2019, the PTC was set to the south at an angle of 30 degrees to the horizon, then the solar irradiance and temperatures were measured as was done in the first scenario, as the volumetric flow did not change ̇ ̇ . Third scenario The third scenario was completed on May 15, 2019. The settings for this scenario are the same as those for the second scenario, but the volumetric flow value is less, i.e., the PTC was set to the south at an angle of 30 degrees to the horizon, then the solar irradiance and temperatures were measured as was done in the first scenario, as the volumetric flow did not change ̇ . III.2. Results analysis The daily variation in solar irradiance measured using the solarimeter on the PTC plane during the test days is given in Figure 5, where it can be deduced from the change of the curves of Figure 4 that the average solar irradiance for days 13 May, 14 May and 15 May is as follows 680, 540 and 494 W/m², respectively. Regarding the change of water inlet temperature “Tin, (°C)”, it is shown in Figure 5, as the field of its change is between 28.2°C