Performance Study of a Cylindrical Parabolic Concentrating Solar Water Heater with Nail Type Twisted Tape inserts in the Copper Absorber Tube

This paper reports the overall thermal performance of a cylindrical parabolic concentrating solar water heater (CPCSWH) with inserting nail type twisted tape (NTT) in the copper absorber tube for the nail twist pitch ratios 4.787, 6.914 and 9.042 respectively. The experiments are conducted for a constant volumetric water flow rate and during the time period 9:00 h to 15:00 h. The useful heat gain, hourly solar energy collected and hourly solar energy stored of this solar water heater are found higher for nail twist pitch ratio 4.787. The above said parameters are found to be a peak at noon and observed to follow the path of variation of solar intensity. At the starting of the experiment, the value of charging efficiency is observed to be maximum. Whereas the maximum value of instantaneous efficiency and overall thermal efficiency are observed at noon. The key finding is that the nail twist pitch ratio enhances the overall thermal performance of the CPCSWH.