In order to secure higher productivity and quality of crops in a greenhouse, the major environment
control variables such as temperature, humidity and CO2 concentration etc should be handled with
appropriately not to make the corps be stressed too much due to disturbances of the variables.
Considering intrinsic function of a greenhouse providing warm and comfortable conditions using solar
energy, the additional auxiliary heating systems is beyond question to play the crucial role to securing
adequate operating environments for cultivation in case of insufficient solar radiation. However, the
degree of ununiformity inside the greenhouse according to the types of heating system often give rise
to the decline of productivity seriously. It is evident that hot water based heating system is superior to
hot air based one in many ways by providing more favorable operating conditions with less
disturbance and shortened reaction time to reach set points of control variables.
In this study, a new concept of radiation unit is proposed adaptable to hot water heating systems, in
which the heat flux from the pipe is to be controlled by changing the convective heat transfer
mechanism around the heating pipe. The optimal design for several different types of fin structure
inside the radiation unit is carried out using the CFD simulation and the elliptical type of fin structure
is suggested to be a strong candidate of application in terms of exit air temperature from the unit.
However, different factors such as an manufacturing cost, ease of fabrication etc is desired to be
considered for final determination of it.