Investigating the performance of a Novel Deep feeding technique in All-Water Evacuated tube Collectors for Solar Desalination Systems

Abstract

Water desalination is one of the most branches investigated due to freshwater scarcity. One of the most effective water desalination techniques is solar desalination. Solar desalination works better under higher temperatures of water as it increases the evaporation and desalination rates. Evacuated tube solar collector (ETSC) presents an advantage as a solar water heater in medium temperature ranges and is suitable for solar desalination. The enhancement of its performance has been a hot topic in the last years due to its high efficiency at high temperatures. However, the techniques with which the ETSC implemented, differs in storage availability as in the all-water systems, good heat transfer as in the direct flow system. In the present research a novel technique combining the benefits of both all-water and direct flow systems is presented to increase the temperature of the heated water. The combined system considers the injection of the feed water inside the ETSC directly to make use of forced convection heat transfer and destruct the stagnation zone in the bottom of the tubes. Three water flow rates of 2, 4, 8 LPH were tested. The combined system achieved an enhancement in the thermal efficiency and the maximum temperature getting out from the ETSC by 27% and 14.7%, respectively, at a flow rate of 8 LPH. Moreover, the overall efficiency was enhanced by up to 27.3%, compared to all-water system. The economic study showed that the cost of heated water with the proposed system over the traditional system reaches 0.00195 $/kw.hr for 8 LPH extraction rate. Due to this increase in the system temperature, the proposed techniques can be applied for solar desalination. The numerical simulation results found to agree with the experimental results by 5.4% relative error.