Radiant and convective heat loss from the new‐born pig

The exchange of heat between animal and environment takes place principally through the channels of radiation, convection and evaporation. Of these, the evaporative heat loss is clearly separate; the difficulty in analysing heat exchange lies in distinguishing between radiation and convection. One way of overcoming the difficulty is to calculate the radiant heat loss from the wall and mean skin temperatures, using an estimate of the animal's effective radiating surface, and then to obtain the convective loss by difference (Hardy & Dubois, 1938a; Blaxter, Graham, Wainman & Armstrong, 1959). Winslow, Herrington & Gagge (1936a, b) solved the problem ingeniously by their method of partitional calorimetry. They enclosed their subject in a booth made of reflecting copper walls. In this apparatus they were able to vary the integrated mean radiant temperature independently of the air temperature, and so to change the radiant heat loss to a different extent from any change in convective heat loss (Gagge, Herrington & Winslow, 1937; Winslow, Herrington & Gagge, 1938). Although this method gave satisfactory results it raises formidable construction problems and presents a lack of flexibility for animal experiments. Another approach to the problem of separating radiation and convection exchanges is made in this paper, and the method is applied to the analysis of the non-evaporative heat loss of the new-born pig.