PERFORMANCE RATING METHOD OF THERMOSIPHON SOLAR WATER-HEATERS

A rating method for the thermal performance of thermosyphon solar water heaters was developed. Except that the outdoor test procedure still follows the Taiwan Standard CNS B7277, a system characteristic efficiency eta(s)* which is defined as the alpha0 value. corrected at M/A(c) = 75 kg/m2, was derived so that eta(s)* is independent of the M/A(c) ratio. Here, eta(s)* can be evaluated by linear regression analysis of the test data. It is found from a series of tests for 31 systems that eta(s)* is independent of M/A(c) indeed, and thus can be used to rate the thermal performance of different thermosyphon solar water heaters during the energy-collecting period. The cooling loss during the no-radiation period is rated by the system cooling time constant tau(c). The present rating method associated with the Taiwan Standard CNS B7277 has been implemented for more than three years and is accepted by the Taiwan solar industry.