Studies on effective radiation area and radiation configuration factors of a pig (part 5): configuration factors of an 88 kg pig to surrounding rectangular planes and configuration factor characteristics of fattening pigs

摘要

Radiant heat incident on a pig aggravates is body heat during hot summer days and alleviates its body cooling during cold winter days. The radiation connfiguration factors of the pig are essential for evaluating the amount of the incident radiation heat from surrounding objects. In this study, a surface-model was used in order to obtain the configuration factors based on the shape of the pig body. The surface-model was a three-dimensional graphic pig with 9304 surface-mounted triangular patches. This polyhedric surface-model was generated from data obtained by three-dimensional shape measurement of a standing stuffed pig with a live weight of 88 kg. The configuration factors of the surface-model pig to the surrounding rectangular planes were numerically calculated by using computer graphics, the law of solid-angle projection and the method of numerical integration.The percentage errors of the calculated configuration factors were estimated to be not larger than 2 percent by the theorem of summation for configuration factors and the theorem of propagation of errors. This led to the conclusion that the accuracy of the calculated configuration factors was three significant digits or more.The figures for determining the configuration factors of the 88 kg pig to rectangular planes on the side wall, in front of or behind the pig, or on the ceiling were presented as a function of one side length in the plane with the other side length and the normal distance between the plane and the center of the pig (that was the midpoints of the body width, body height and body length) as parameters. The diagrams for the configuration factors to rectangular planes on the floor in direct contact with or below the bases of the pig's hooves were also presented in the same way. The properties of these configuration factors fully reflected the three-dimensional shape of the unsymmetrical pig body.From the comparisons between the configuration factors of the 27 and 65 kg pigs in previous papers and the 88 kg pig, the following conclusions were drawn: (1) The configuration factors of the 27, 65 and 88 kg pigs were not alwasys the smallest, medium and the largest, respectively; (2) The configuration factors of these three pigs to a rectangular plane on the side wall located at a normal distance of 2 m or larger were nearly the same, and independent of the weight, that is, the size of the pig body; (3) The configuration factors of the pigs to a rectangular plane on the side wall at a normal distance of less than 2 m, in front of or behind the pig, on the ceiling or on the floor were different, depending on the weight.