Modelling air change rate of naturally ventilated dairy buildings using response surface methodology and numerical simulation

The air change rate (ACR) of naturally ventilated dairy buildings (NVDBs) plays an important part in the design and control of the ventilation system, as well as in the estimation of the gaseous emission rate. The objectives of this research were to model theACRbased on a quantitative investigation of the relationship between theACRand its potential influencing factors, including the opening ratio (r), the building length to width ratio (alpha), the wind speed (U), and the wind direction (theta). The investigations were performed using the response surface methodology integrated with the Box-Behnken design and Computational Fluid Dynamics (CFD) simulations. Three response surface models of theACRof NVDBs were established for three opening ratio ranges of 5%-42.5%, 42.5%-80%, and 5%-80%, respectively. It was found that the selection of the opening ratio range had almost no effect on the developed response surface models. The results showed that theACRof NVDBs was not influenced by alpha, but was significantly affected byr, U, theta, and interaction effects between every two of the three factors. The highestACRwas 6.7 s(-1), 6.0 s(-1), and 4.0 s(-1)when theta, U, andrwas at their respective medium value while the rest parameters were at the highest values, indicating that therplayed an important role in the value ofACR. It was concluded that in the prediction of theACRof a building, the influences of both individual and interactional effects of theta, U, andrshould be considered.

Automated summary

The study established models for the air change rate (ACR) of naturally ventilated dairy buildings based on a quantitative investigation, with findings showing that the opening ratio had minor impact on the developed response surface models. Results indicated that the wind speed, wind direction, and opening ratio significantly affected ACR, with interaction effects also playing an important role in influencing the ventilation rate.