Effect of Heating System Position on Vertical Distribution of Crop Temperature and Transpiration in Greenhouse Tomatoes

The presence of independently controllable heating systems enables local crop heating to influence the crop development. The position of the heating system also influences energy consumption. A simulation model was developed to predict the effects of the heating system on the vertical distribution of crop temperature and transpiration in a greenhouse tomato crop. The model is based on physical transport processes (radiation, convection and latent heat transfer). The radiation exchange factors between heating pipes, crop layers, soil and roof were determined as a function of the vertical distribution of leaf area and position of the heating systems. Experiments were performed to evaluate the model under a range of ambient nighttime conditions, including differences in leaf area index and position of the heating system and its temperature. Nighttime temperature differences in the tomato crop appeared to be small and the local effects on leaf temperature of the heating pipes, is rather limited. The energy requirement increases by 5-10% with overhead heating pipes. The simulation model is well suited to predict crop temperature distribution as a function of the position and temperature, of the heating pipes, as well as the vertical distribution of crop evaporation.