Solar collector efficiency was greatest at the beginning of
the day, when in ambient air temperature and outlet air
temperature was smallest (Fig. 5). The efficiency equationfor this particular system is given by the slope-interception
form of the equation of straight line, in which the slope
value represents global heat lost (FRUL), and its intersection
with the y-axis represents heat gained FR(as). As can
be seen in Fig. 5, efficiency has a negative slope; in the first
hours of measurement, thermal efficiency was greater due
to the fact that there was a smaller difference between
ambient temperature and the air temperature in the interior
of the solar collector (hi ha) ; consequently, radiative and
convective losses are also smaller. Thermal efficiency is
affected by the difference in these temperatures (hi ha) ;
this difference is greatest at solar noon (Fig. 4), at which
point a greater air mass flow rate is required to remove heat
and increase efficiency, and to avoid radiative and convective
losses.
Solar collector efficiency was greatest at the beginning ofthe day, when in ambient air temperature and outlet airtemperature was smallest (Fig. 5). The efficiency equationfor this particular system is given by the slope-interceptionform of the equation of straight line, in which the slopevalue represents global heat lost (FRUL), and its intersectionwith the y-axis represents heat gained FR(as). As canbe seen in Fig. 5, efficiency has a negative slope; in the firsthours of measurement, thermal efficiency was greater dueto the fact that there was a smaller difference betweenambient temperature and the air temperature in the interiorof the solar collector (hi ha) ; consequently, radiative andconvective losses are also smaller. Thermal efficiency isaffected by the difference in these temperatures (hi ha) ;this difference is greatest at solar noon (Fig. 4), at whichpoint a greater air mass flow rate is required to remove heatand increase efficiency, and to avoid radiative and convectivelosses.
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