Analysis of the thermal environment in a mushroom house using sensible heat balance and 3-D computational fluid dynamics

An environmental prediction model was developed for optimal ventilation in a mushroom house utilising a sensible heat balance and a three-dimensional (3-D) computational fluid dynamics (CFD) model. The respiration of the mushrooms and the use of a low-capacity cooler were considered. A mushroom-house-specific ventilation equation was developed to calculate the ventilation rate for a given environmental condition. Calculated ventilation rates were compared with the experimentally measured data for the indoor temperature set to the optimum for growing mushrooms (16.2 °C) with varying outdoor temperature. There was good agreement between the measured and predicted rates (0.2-5.1% error). Calculated ventilation rates (from the sensible heat balance) were used as an input parameter for 3-D CFD model, eliminating the need for experimental measurement of ventilation rate. 3-D CFD simulations were conducted using the same environmental condition to establish the local heat distribution in a mushroom house. The simulation results for temperature were compared with the experimental data at several different locations in a mushroom house and showed negligible errors. The CFD model was also used to improve heat distribution of a mushroom house. It was predicted that enhanced cooling and more uniform temperature distribution could be achieved just by changing the direction of airflow from air inlet ducts and/or installing small fans onto them, but not by changing the directions of airflow from a cooler. This would be a more economical than replacing a cooler or redesigning the entire structure. The model could be used to predict the environmental conditions over different locations in a mushroom house without the need for experimentally determining the ventilation rate.