Improvement of the ventilation system of a naturally ventilated broiler house in the cold season using computational simulations

Limited measurement points and unpredictable airflows, as well as uncontrollable weather conditions, make conducting field experiments to study ventilation in broiler houses very difficult. Simulations using computational fluid dynamics (CFD) are often used to overcome the above mentioned limitation. In this study, airflow, internal air temperature distribution and ventilation efficiency of a conventional ventilation system and several modified ventilation systems were analysed both quantitatively and qualitatively using a previously developed CFD model. These analyses were conducted in order to enhance the rearing condition of the conventional, natural ventilated broiler houses. A tracer gas decay method was adapted to the CFD main solver utilising a user-defined function to calculate the ventilation efficiency and building energy simulation (BES) method was used to compute the heating load. In order to replicate the ventilation problems encountered during the field experiment, the various ventilation systems were studied in the cold season with four different types of vent openings: a chimney, a side vent, a pipe under the roof and a side-up vent at the eaves. From the CFD results, the optimum results were obtained with a model that used a diffuser beneath the chimney inlet which mixed the incoming cold air with the warm air that had accumulated in the upper portion of the broiler house. An additional curtain installed close to the internal side wall effectively guided exhaust gas to the outlet vents and introduced the incoming fresh air to the broiler zone. The curtain also enhanced the thermal insulation at the side wall. Because of its high ventilation efficiency in the broiler zone, compared with a conventional broiler house there was a 32% increase in the thermal uniformity and a 14% increase in the thermal suitability. The BES results indicated that the model could save 47% of the energy input at the broiler zone compared to the conventional ventilation system. An additional field experiment demonstrated that an upgraded broiler house adapted to the model saved 30% of energy costs.