PERFORMANCE RATING METHOD OF THERMOSIPHON SOLAR WATER-HEATERS

A rating method for the thermal performance of thermosyphon solar wate r heaters was developed. Except that the outdoor test procedure still follows the Taiwan Standard CNS B7277, a system characteristic efficie ncy 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) r atio. 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-ra diation period is rated by the system cooling time constant tau(c). Th e 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.