BUOYANT FLOW GENERATED BY THERMAL CONVECTION OF A SIMULATED PIG

Abstract

The effects of internal occupants and supplement heating make up an essential issue for the prediction andcontrol of fresh ventilating air distribution in an enclosure. The influence from livestock is complex, since they are mobileobstacles, producing heat and contaminants in irregular geometry. As a part of the basic studies of these influences, theinvestigations of air motion in a thermal buoyant flow caused by free convection around a livestock body are reported inthis article. A simulated pig, made of a painted metal tube (1 m long and 0.5 m in diameter) with covered ends and heatelements inside, was used as the heat source in the experiments. The experiments were carried out in a full-scale room, 5m 11 m in floor area, with a 2.4 m side wall height, and sloped ceiling to center (height: 4.8 m). The simulated pig wasplaced near the center of the floor. The vertical temperature difference in the room space was less than 0.3C. Thevelocity and temperature in the thermal plume were measured with six sensors (each has both temperature and velocityelements) placed at 0.2 m horizontal intervals. Data were acquired at 14 levels from 0.2 to 2.4 m above the top surface ofthe simulated pig. The data-sampling period was 30 min in steady state for each measurement.The results show that the plume was quite thin at the beginning (yd 0.6 m) in the central radial plane of the model.Observations showed that the laminar flow at the beginning remained for some distance before it became turbulent andspread. When the distance from the top of the model increased (yd 0.8 m), the temperature and velocity profile of the jetfit Gaussian distributions. The temperature profiles were slightly wider than the velocity profiles. Numerical simulations(Computational Fluid Dynamics) were applied for the same experimental set-up in computing the airflow over the pigsimulator. Transient simulation with fixed time stepping provided similar results to the measurements, indicating the CFDsimulation method used in the study has potential for prediction of buoyant flow generated by this type heat source.