LOCAL BEHAVIOR STUDY OF WATER AT THE OUTLET OF RECTANGULAR CHANNEL OF FLAT SOLAR COLLECTOR FOR THERMOSIPHON SOLAR WATER HEATER

This study deals with the water flow in a flat solar thermal collector with a rectangular channel for a thermosiphon water heater. It consists of determining the influence of the height of the water channel on parameters such as the water temperature at the outlet of the channel, the water outlet velocity of the channel and the generated entropy. To do this, the different equations of the local behavior of the water flow in the channel were estimated. These different equations were numerically solved by the finite element method through the Comsol Multiphysics software version 5.2a by considering three rectangular channels of width 1m and different heights (0.005 m, 0.01 m, 0.02 m). These different channels are exposed to two different fluxes namely 94 W/m2 and 972 W/m2 corresponding respectively to the lowest and highest solar flux of the study area. The results showed that the height of 0.01 m has an optimal speed and temperature. At this height, the generated entropy is lower than in the cases of heights of 0.005 m and 0.02 m.