Performance Evaluation of All-glass Evacuated Tube Solar Water Heater with Twist Tape Inserts Using CFD

The flow and heat transfer performances of solar water heaters for different initial temperatures (ranging from 273K to 313K) with twist tape inserts are evaluated using numerical simulation. A numerical model of the heat transfer and fluid flow inside a single collector tube has been developed. The predicted results match fairly well with experimental data. Results indicate that, the twist tape inserts reduces velocity magnitude and makes the temperature field more uniform. The twist tape inserts helps heat transfer at relatively high temperature and is not conducive to heat transfer at relatively low temperature. Over the range investigated, the mean Nuseelt number of the solar water heaters with y=2.5 and 4 are respectively 1.07% smaller and 9.29% larger than the normal solar water heater.