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The most common method for calculating transient (time-varying) heat gains and losses. through walls and roofs is the transfer function method. The transfer function method, developed by Mitalas and Arseneault(1, 2) is clearly presented in detail in Chapter 22 of the 1972 ASHRAE HANDBOOK OF FUNDAMENTALS(3). Sufficient data are tabulated in the presentation to calculate the transient heat gains or losses for a total of 96 types of wall constructions and 36 types of roof constructions. Further, it is possible to calculate the transient heat gains or losses on a type of construction not listed in the HANDBOOK by working directly with the Fortran IV computer program that has been developed by Mitalas and Arseneault(2), The transfer function method has the ·inherent· capability to calculate heat gains and losses through building sections when both outside and inside air temperatures vary. However, when applying the transfer function method to solve a heat flow problem using the method and data in the HANDBOOK, one limitation is that the indoor air temperature must be assumed constant over a 24-hr period(3). This limitation is imposed, presumably, to greatly simplify the calculation. Consequently, the procedure for applying the transfer function method for many different types of wall and roof construction cannot be used to investigate the reductions in heat gains or losses that can be realized by changing the inside temperature. The practice of changing thermostatic settings to reduce energy requirements in buildings during the hours when the buildings are not occupied holds significant potential for reducing the overall energy requirements for heating and cooling.The transfer function method is a special case of the calculation of heat flow through building components by the thermal response.factor method(3 also developed by Mitalas and Arseneault(4). The thermal response factor method has been generalized by Kusuda(S) to multilayer structures with various curvatures of finite thickness and to semi.:.infinite systems. To solve heat flow problems when both outside and inside air temperatures are transient, one must use the more general thermal response factor method, To apply this method, one. must deal with Bessel functions, Laplace and inverse Laplace transforms, and power series analysis(S). This paper presents the development of a computer simulation model for calculating transient hea; gain by conduction through walls and roofs that has all the capabilities of the transfer function method. The model has the advantage of being easily applied to simulating the heat gain by conduction through walls and roofs when both the outside and inside air temperatures are transient. Advanced mathematical techniques such as are required for the thermal response factor method are not necessary; ·to understand and apply the method presented in this paper.

Citation: ASHRAE Transactions, Volume 81, Part 2, Boston, MA

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Published: 1975 Number of Pages: 13 File Size: 1 file , 870 KB Product Code(s): D-BO-2364