A dimensionless parameter coupling the south and north roofs on the thermal environment of Chinese solar greenhouse: Ridge position ratio

This paper clarified the mechanism of the south and north roofs on the
thermal environment of the Chinese solar greenhouse (CSG), using a new
parameter: ridge position ratio (RPR), which can describe the dynamic
dependency relationship between the south and north roofs. A mathematical
model was established by using the method of combining computational fluid
dynamics (CFD) with experiments, which then was used to analyze the effect
of RPR on the thermal environment of the CSG. Based on this model, we
compared the temperature distributions of the greenhouse with different
RPR. Furthermore, the effects of different RPR on the amount of solar
energy that entered the greenhouse were studied. Finally, the effects of
different RPR on heat released capacity of the greenhouse envelopes at
different moments were analyzed. The results showed the decline rate of
the maximum temperature of each part in different RPR intervals increased
as the increase of RPR during the daytime. The occurrence time of the
maximum air temperature will be delayed when RPR increases to 0.3. As RPR
increases, the heat storage layer of the soil gradually becomes thinner,
but that of the north wall remains unchanged. RPR has a relatively small
effect on the minimum temperature in each part of the greenhouse during
the nighttime. Mathematical models of the relationships between RPR and
the solar energy that entered the greenhouse, the released heat energy of
the enclosure structures were established, respectively. The results can
provide theoretical guidance for the structural design of the CSG.