Design and Testing of a Heat Transfer Model of a Raccon (Procyon Lotor) in a Closed Tree Den

Abstract

A heat transfer model of a raccoon (Procyon lotor) in a hollow tree was designed and tested by simulating an overwintering raccoon with a fur—covered, electrically—heated cylinder in a closed den. A comparison was made between predicted and observed fur surface temperatures, and heat losses from the top, side, and bottom. Under these conditions, transfer coefficients derived from engineering relationships can be dependably used in the field; the average difference between predicted and observed fur surface temperatures was 1.6°C, and the sum of the predicted fluxes through the surfaces of the model was within 5% of the measured total. Total heat loss increased approximately linearly as inside wall temperature decreased, but the contribution by convection and radiation to the total changed substantially. As inside wall temperature decreased, convective flux was an increasing percentage of the total, whereas radiation loss decreased to a minimum value of 56% of the total flux at the minimum wall temperature. Twenty—five percent of the total flux was lost from the top, 62% from the side, and 13% from the bottom. More than 65% of the total resistance to heat loss through the model side was in the fur. The air space presented 17%, with the rest in the den wall With respect to heat loss through the base of the den, only 6% of the total resistance was in the compressed fur. But because of the high resistance of the den base, the loss was half that of the top. Small variations in den wall thickness are not a major factor in reducing heat loss since the wall accounts for only about 18% of total heat flow resistance. Energy loss and average monthly weather screen air temperature are correlated.