Numerical simulation of water circulation inside a vacuum tube solar water heater

Numerical simulation for water circulation inside vacuum tube solar water heater is presented. Only one tube with it’s proportional section of storage tank is considered for this simulation using Fluent. Experimental test was used in order to validate the numerical results and they’re found out to be in a good agreement. This numerical model can be used to study the effect of different geometric parameters such as tube’s aspect ratio, tube’s inclination, tank’s volume, distance between two adjacent tubes, use of diffuse flat reflector (DFR, in short), distance between solar tubes and the DFR and climatic conditions on the thermal performance of these kind of solar water heaters. Temperature and velocity distribution inside the tube and storage tan are the results of this study. These diagrams show that there is an inactive and hot region near the tube’s end and there is also an inactive and cold region in the bottom of the storage tank which do not participate in the overall water circulation. The effect of average solar heat flux per each tube on the thermal performance of these solar water heaters is studied. Results show that thermal performance of these solar water heaters increases almost linearly as the average solar heat flux per each tube increases.