Numerical Analysis of Extra Inlet Integration in Close House Cages under Single and Multiple Exhaust Fan Operations

This study investigates the impact of additional air inlets—specifically slot and ceiling inlets—on airflow distribution, microclimate conditions, and waste gas accumulation in a negative pressure close house cage. Poor ventilation in such systems often leads to heat stress, increased mortality, and the buildup of CO 2 and NH 3 . Increasing the supply of fresh air is essential to enhance thermal comfort and maintain a healthy indoor environment. A three-dimensional CFD model was developed using the k-ω SST turbulence model, incorporating heat transfer, buoyancy effects, and porous media for both the evaporative cooling pad (ECP) and poultry. Simulations were conducted under single and multiple exhaust fan operations, using four variations of extra-inlet placements. The effects of each configuration were evaluated in terms of airflow velocity, temperature, relative humidity (RH), and gas concentration across 42 iso-surfaces along the cage’s longitudinal axis. The results showed that additional inlets reduced CO₂ and NH₃ accumulation, especially under multiple exhaust fan operation. However, these setups also introduced warmer and drier air due to unconditioned inflow, reducing airflow uniformity. Slot positions near sidewalls lowered RH and increased thermal discomfort. Despite improved gas removal, the configuration without extra inlets offered better environmental stability and thermal uniformity.