Abstract
Thermal radiation falling on a pig housed in a building has a considerable heating effect on it and is one of significant factors affecting its comfortable conditions. The first step in most radiant heat transfer calculations is the determination of radiation configuration factors, which are also called angle, shape or view factors, between the pig and the surfaces of its surroundings. The configuration factors vary with the size or weight, posture and orientation of the pig, the distance from the pig to the surface, and the dimensions and direction of the surface.
The purpose of this investigation was to present configuration factors of growing-finishing pigs in a standing posture to vertical or horizontal rectangular planes on walls, ceilings and floors on the basis of their complex body shapes, when they can orient themselves to the planes at random. The configuration factor in this paper was the mean value of local configuration factors when the pig rotated from 0 to 360° at 15° intervals around a vertical axis through its center (that was the midpoints of the body width, body height and body length) for a given normal distance from the center to the plane and a given size of the plane, and therefore was not dependent on its orientation toward the plane. The local factor of the pig to the plane was numerically calculated by using the same procedure as author's previous studies; namely, three surface-models of standing pigs with live weights of 27, 65 and 88kg as subjects, and numerical analyses involving computer graphics such as the unit-sphere projection method were also used herein.
The percentage errors of the calculated configuration factors were estimated to be not larger than one percent by the theorem of summation for configuration factors and the law of propagation of errors. This led to the conclusion that the accuracy of the calculated factors was three significant digits or more.
The configuration factors of the pigs to rectangular planes on the wall located at a normal distance of 1.5m or larger and on the ceiling with a normal distance of not less than 0.5m were found to be evaluated with a sufficient degree of accuracy by the following well-known equation for the configuration factor φ of an infinitesimally small sphere to a rectangular plane:
φ=1/4πtan-1(A/D)(B/D)/√(A/D)2+(B/D)2+1
where A and B are the side lengths in the rectangle, and D is the normal distance between the sphere and the plane. This equation was also available for determining the configuration factors of the pigs to rectangles on the wall with a normal distance of 1m or larger in the space between their centers and hooves. On the other hand, the equation was not available for evaluating the configuration factors to rectangular planes on the wall at normal distances of 0.5 and 1m, on the floor in direct contact with the bases of their hooves and on the floor below their hooves at normal distances of 0.5, 1 and 1.5m. Consequently, these factors were presented in graphical form as a function of one side length in the plane with the other side length and the normal distance as parameters.
