Numerical Predictions of Air Temperature and Velocity Distribution to Assist in the Design of Natural Ventilation Piggery Buildings

Abstract

Pigs are subjected to intensive environment control and management for higher productivity due to their sensitivity to climatic variation, which affects their growth and impacts greatly on the profitability of this industry. The appropriate temperature and air speed inside a piggery that meets the thermal comfort of the pigs depends on the age of the pigs; in this study grower pigs (32-52 kg) are considered. The aim of the current work is to model the air flow in a natural ventilation piggery numerically and hence predict the velocity and temperature of the air inside the piggery. The effect of some variation in the design of the piggery on the environment inside the piggery, and more specifically at the pigs’ level, has been also investigated. A steady two-dimensional numerical model including the effect of buoyancy, turbulence and heat generated by the pigs was solved using the computational fluid dynamics software Fluent, which is based on the integral volume method. Temperature and air speed inside the piggery and at the pigs’ level were predicted for a particular wind velocity and temperature to facilitate the comparison of the effect of the different variations in the design proposed in this study. These variations were reducing the height of the outer wall of the piggery to the same level as the pens and changing the type of fence used in the pens as well as adding louvers in the air opening, changing the shape of the roof and adding insulation to the roof. Air was assumed to enter the piggery at speed of 0.92 m/s to the southwest and at temperature of 34 °C. The results suggest that varying the type offence from a solid internal fence to ones made of separated bars (new fence) only did not have much impact on the environment inside the piggery. When this change was combined with the other variation such as lowering the outer walls it made some improvements. Combining the new fence, lowering the outer walls and changing the shape of the roof resulted in the highest increase in the air speed of about 0.2-0.4 m/s at the pigs’ level in comparison to the original design. Unfortunately this reduction was not large enough to bring temperature and air speed to the thermal comfort of these pigs at that climate; however this improvement would be sufficient in a milder climate. It was concluded that water sprayers are needed in this hot climate to meet the pigs’ thermal comfort limit. The addition of sprayers has been investigated and results show that a large portion of the piggery with the sprayers meets the thermal comfort of the pigs at this age. However, optimisation of the location of the sprayers and the amount of water to be used in the sprayers is recommended for future study so an economical watering system is obtained.