Control and modelling of vertical temperature distribution in greenhouse crops

Based on physical transport processes (radiation, convection and latent heat transfer) a model has been developed to describe the vertical temperature distribution of a greenhouse crop. The radiation exchange factors between heating pipes, crop layers, soil and roof were determined as a function of the vertical distribution of the leaf area of the crop. To validate the model a series of experiments was performed with a tomato crop under a range of ambient night-time conditions, including differences in LAI and position and temperature of two pipe heating systems. The local effects of increased pipe temperatures on leaf temperature appear to be rather limited as well as on the distance over which significant effects occur. The model can be used to predict crop temperature distribution as a function of the position and temperature of the heating pipe. This can lead to a better control of crop development and a more efficient use of energy.