ENERGETICAL MODEL FOR GREENHOUSES

The authors present a complete thermal model of a greenhouse. This model takes into account the various physical processes (conduction, convection, evaporation, condensation, solar and long-wave radiations) which are involved in the dynamic energy balance of the whole system (cover, inside air, plant canopy, heat exchanger, screen and soil layers). The main features of this model are the followings: 1) A detailed study of the long-wave radiative exchanges by the use of shape-factors calculations. An example shows that the geometrical configuration of the heat exchanger has a great effect on its efficiency. 2) The use of an analytic periodic solution to set convenient initial values for the temperatures of the ground layers, in order to accelerate the convergence. This method optimizes the dynamic response of the model on a standard microcomputer. This model is a basic ingredient of a friendly user software developed for greenhouses heating systems design: Thermi-Serre < R >.