them steady-state procedure is the most common, where transient
effects due to collector heat capacity can be minimized by performing
tests only during periods when I and Tamb are steady.
The procedure involves simultaneous and accurate measurements
of m_ , the inlet and outlet temperatures of the collector fluid, and
the ambient conditions. Here, after a change of flow rate, both
the solar heaters ‘‘s1’’ and ‘‘s2’’, was allowed to attain a steady state
before experimentation. Following equations (Eq. (1)–(7)) have
used to obtain the values of necessary parameters which are mass
flow rate, equivalent hydraulic diameter, Reynolds number, friction
factor, pressure drop, overall heat transfer coefficient, and
overall heat loss coefficient respectively, to evaluate the thermal
performance of both solar heaters ‘‘s1’’ and ‘‘s2’’ and enhancement
by using