Studies on the Thermal Radiation Environment within Livestock Barns (III)

The Factorial Effects for Short-wave Radiant Heat in Gable Roofed Open-type Livestock Barns

Abstract

According to procedures that were described in the previous paper, the authors carried out an analysis of factorial effects on the shortwave thermal radiant environment within gable roofed open-type barns. The results from the simulation which were subjected to analysis of variance were the diurnal average and the maximum, between 9:00 and 17:00, of downward short-wave radiant heat on an infinitesimal horizontal element located in the center of the barn one meter above the ground. The summary of the results is shown below.
1) Factors that had significant effects on the diurnal average were (1) the width, (2) the height of the eaves, (3) the orientation of the barn, (4) the inclination of the roof, (5) the absorptivity of the inside roof surface for short-wave radiation, (6) the length of the barn, and (7) the kinds of ground surfaces, in order of the magnitude of contribution ratios (Table 2). Sixty-seven point six percent of the total variation for the diurnal average was caused by above factors, with 53.7 percent caused by the width of the barn and height of the eaves.
2) Significant factors for the maximum were (1) the height of the eaves, (2) the width, (3) the length of the barn, (4) the inclination of the roof, (5) the orientation of the barn, and (6) the kinds of ground surfaces, in order of the magnitude of contribution ratios (Table 4). Sixty-seven point four percent of the total variation for the maximum was due to these factors, with 45.9 percent due to the width of the barn and height of the eaves.
3) The equations that are best able to predict the diurnal average (eq. (1)) and the maximum (eq. (2)) were obtained from the present analysis. The predicted values of differnt gable roofed open-type barns are calculated by the sums of the estimated values of the effects of several factors as indicated in Table 3 and 5.
4) The levels of the factors that make the short-wave radiant environment most suitable are as follows:
(a) The height of the eaves is less than 1.5 meters. If so, the width of the barn scarcely affects the short-wave radiant heat. If the height of the eaves is 3.0 and 4.5 meters, then the width of the barn should be more than 10.0 and 17.0 meters, respectively.
(b) The orientation of the barn is east-west.
(c) The inclination angle of the roof is less than 20.0 degrees.
(d) The absorptivity of the inside roof surface for short-wave radiation is above 0.9.
(e) The length of the barn is over 45.0 meters.
(f) The ground surface is a bare ground.
In these conditions the diurnal average and the maximum were predicted to be less than 15.2 and 179kcal/m²·h respectively, at a confidence level of 95%.