Transmission and storage characteristics of walls experiencing sinusoidal excitation

Abstract

The design procedure used in the UK to estimate the thermal response of a building for design purposes refers internal temperatures to environmental temperature t ei , which is a linear combination of space averaged air and radiant temperatures. All internal heat inputs can be taken to be input at t ei . The fluctuating component of heat gain due to solar radiation on the outside of a wall and transmitted to the interior can be expressed as q ei = ut sa where u is the alternating transmittance and t sa is the sol-air temperature. The fluctuating component of heat absorbed by the solid surfaces present in the room can be expressed as q ei = yt ei , where y is the admittance. This article is concerned with the behaviour of u and y. For an infinitely thick slab, the surface admittance(q si /t si ) = a = (2πkϱc/P) 1/2. For an infinitely thick slab, the thickness τ = ( πϱ cX 2 Pk ) 1 2 can be defined: a and τ then completely determine the conduction properties of the slab. The effects of inner and outer films to link the slab with t ei and t sa are discussed and non-dimensional values are tabulated. An example of finding u and y for a multilayer slab is presented. Any multilayer slab can be described exactly by three complex elements in T or π formation, and approximately by a three-section ladder formation. The response of an enclosure is discussed in matrix and circuit terms and the relations between heat flows and temperatures are described by vector diagrams.