On the reliability of ASHRAE conduction transfer function coefficients of walls

The transfer function method recommended by the ASHRAE can be considered th e most modern tool currently available for the thermal analysis of a buildi ng. It is particularly well suited for use with a computer as it makes it p ossible to describe with great accuracy the internal heat gain of walls usi ng a small set of coefficients. The present paper shows how to calculate se ts of coefficients diverse from that proposed by Mitalas who first develope d the method and on the basis of an unequivocal criterion, to prove the adv antages in using them. The authors also investigated some of the paramount mathematical and physical aspects which affect the approximation degree of the ASHRAE method and, with reference to the optimal number of poles and co efficients, they tried to offer some certainties for a more conscious use o f it. (C) 1999 Elsevier Science Ltd. All rights reserved.