CFD modeling of air flow, humidity, CO2 and NH3 distributions in a caged laying hen house with tunnel ventilation system

Abstract

In poultry houses, the ventilation system should provide a favorable standard living environment for hens. In addition to uniform distribution of velocity and temperature, concentration of gaseous CO2 and NH3 pollutants and the humidity distribution, which affect the air quality in the poultry house, are of prime importance. In previous numerical studies on caged laying hen houses with tunnel ventilation system, these five concerns have not been examined concurrently. To address all of these issues, in this numerical study a previously studied laying hen house with 4 rows of cages equipped with tunnel ventilation system using evaporative cooling pads has been considered in summer. 3D numerical simulations indicated the deficiency of previous models for provision of proper temperature and velocity distributions also ignoring investigation of humidity and concentration of gaseous pollutants. Thus three new models were proposed, in which the position and number of evaporative cooling pads and exhaust fans and their capacity were altered. Evaluation showed that the second new model, in which 15 fans are on the east wall and three evaporative cooling pads are on the west wall, provides the best performance. In this model, the speed at the levels of the birds is 2.5 m.s− 1 and the maximum temperature is 308 K. Also, the relative humidity is between 60 and 75%, which is 10% lower than that of the original model of previous study and CO2 and NH3 concentrations are within the tolerable range everywhere. The CFD techniques utilized in this study may be extended to simulate other poultry houses with any ventilation system such as tunnel, mixed or any other inlet/outlet arrangements, however for the results to be reliable simulation should involve air flow, thermal and humidity fields as well as CO2 and NH3 concentrations.