Simplified Thermal Parameters: A Model of the Dynamic Performance of Walls

摘要

In-situ measurement of wall thermal performance entails two problems: (1) selecting a technique for measuring time-varying surface temperatures and heat fluxes on both sides of the test wall and (2) reducing this data set into a small number of parameters that characterize the wall. The first problem is addressed by the Envelope Thermal Test Unit (ETTU), consisting of two four-foot by four-foot blankets placed on either side of the test wall that are used to both measure and control the surface heat fluxes and temperatures of the wall. Dynamic measurements always require specifying a driving cycle to get the dynamic characteristics from the test wall. The choice of a preferred dynamic cycle is addressed, and a pink-noise driving cycle is chosen to maximize the amount of information from a given test. To analyze the data gathered by ETTU a simplified dynamic model was developed that describes the thermal performance of a wall by a small number of parameters: a steady-state conductance, a time constant, and some storage terms; these parameters are called Simplified Thermal Parameters (STPs). The ability of this model to simulate actual wall performance is demonstrated by comparison to results generated with conventional response-factor methods. The model is used to analyze the behavior of a theoretical multi-layer wall whose properties have been specified by a response-factor calculation. (ERA citation 07:043983)