Document Type : Research Article
Authors
1 Department of Biosystem Engineering, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran
2 Department of Biosystem Engineering, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran.
3 Department of Biosystems Engineering, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran
Abstract
Introduction
With increasing the world's population, the need to supply water resources is increasing, as well. However, fresh water resources are out of reach due to climate changes, and production of drinkable water from seas and oceans has always been the focus of researchers. Iran with considerable levels of solar radiation and the access to open water from the north and south is a suitable country to produce fresh water. Using solar water desalination systems is a proper and economical solution to produce drinking water from salt water sources. The purpose of this research is to increase the performance of the solar water desalination system by using the latent heat storage system and the solar tracking system. Water as working fluid and parabolic collector as a source of thermal energy were used experimentally to produce fresh water.
Materials and Methods
The solar water desalination system was designed and built on a laboratory scale in the University of Kurdistan and the desired experiments were performed on it. The flowing fluid (water) inside the spiral tube in the tank is entered into the absorber tube of the parabolic collector by means of a pump. As mentioned, inside the receiver tube, there is a spiral copper tube with a pitch of 7 cm, which contains paraffin. The parabolic mirror, reflects the sunlight on the receiver tube and causes the water (as working fluid) to heat up. The cooling process is done using a specific source placed in the upper part of the distillation tank. In this case, the steam droplets in the tank hit the bottom surface of this cooling tank (which is in the form of an inverted funnel) and condensation takes place. This research was carried out during four separate tests on 4 consecutive days of 24th, 25th, 26th, and 27th of August, 2022 for three volume flow rates of fluid 1.9, 3.1 and 4.2 l/min and without phase change materials in Renewable Energy Laboratory, university of Kurdistan, Sanandaj. The experiments were conducted under similar conditions and started at 10:00 and ended at 14:00. It should be noted that in the case without phase changing materials, the volume flow rate of the fluid was considered to be 4.2 l/min. In this case, the pump was transferring the fluid at its maximum flow rate. Variations of outlet temperature, thermal efficiency, desalination efficiency and produced water was investigated at different conditions.
Results and Discussion
The results showed that by reducing the pitch of the spiral tube, the amount of heat obtained increases due to the increase in the Nusselt number. At the beginning of data collection, a significant part of the energy entered into the receiver tube is used to heat the phase change material and the spiral tube inside the receiver and this reduces the initial air temperature. The highest salt water temperature occurs for the fluid flow rate with a flow rate of 4.2 l.min-1 and the lowest temperature occurs for a flow rate of 1.9 l.min-1. With a flow rate of 4.2 l.min-1, the heat absorbed by the absorbent tube is quickly transferred to the salt water chamber by the fluid. The input energy to the tank changes from 1.53 to 2.83, 1.14 to 2.18, and 0.73 to 1.48 MJ for fluid flow rates of 4.2, 3.1, and 1.9 l.min-1. For the system without phase change materials with a flow rate of 4.2 l.min-1, the thermal efficiency is lower than the cases with phase change materials (5.02 and 3.51 %). Moreover, using solar tracking mechanism, the thermal efficiency of the collector increased about 9.86% related to the system with photocell sensor. According to the values for water quality it can be stated that obtained sample water can be used for drinking by reducing the dissolved solids.
Conclusion
In this research, the process of thermal changes in the solar water desalination system using PCM has been investigated. The obtained results illustrated that using PCM improved the thermal efficiency of the collector. Moreover, the quality of obtained water from the present system was in acceptable range to drink. Using a solar panel tracking system improve the efficiency of the solar collector.
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