Abstract
Numerical study has been done for comparing radiant heating system with warm air heating system which mainly focuses on the effectivity of radiation heat. First, authors could achieve some empirical index (i.e., so far called critical convective heat transfer coefficient, c.c.h.t.c.) by which the energy savings characteristics of the applied heating system may be evaluated for the space. However, in the first paper of this series, a theoretical formula has been presented for estimation of the c.c.h.t.c.. The conception used in the development of theoretical formula is that, when the thermal environmental conditions are considered constant and the changes of temperature in one of the surfaces (underchange surface) of space happens without causing any change in the heat loss of another exterior surface (object-surface), the convective heat transfer coefficient of that object-surface takes a particular value and has been called critical value. This c.c.h.t.c. as an index determines which heating system brings about less thermal load when used in a space under equivalent thermal environmental level. In the second paper of this series, effects of various physical and or environmental parameters have been numerically experienced upon the c.c.h.t.c. through Experimental Design Method, based on which the theoretical formula obtained for c.c.h.t.c. in the first paper has been affirmed. In this paper, energy savings border (i.e., line or plane) as a new term has been proposed, by which the space can be divided into two zones. Each zone implies either conventional warm air heating system or radiant heating system may produce more thermal load depending on the location of thermal environment conditions indicator (i.e., it may be body temperature of man, etc.). An approximate formula-by means of c.c.h.t.c.-has been developed for evaluating the energy savings border, besides, the validity of this approximate formula has been affirmed by collating it with that obtained from the concise method.
