Prediction of the dynamic thermal behaviour of walls for refrigerated rooms using lumped and distributed parameter models

Physically realistic lumped and distributed parameter models were used to represent one-dimensional heat conduction through the layers of solid conducting walls in low temperature applications. A range of feasible models with differing complexity for representing the thermal resistance of thermal capacitance each of concrete, concrete–insulation–concrete and concrete–insulation–metal type walls was investigated by comparison of simulated dynamic behaviour to predictions by a finite element model programme, which was itself validated by comparison to experimental data for wall systems. Model evaluation measures to aid engineering judgement in selecting appropriate wall models for particular applications are presented. Only resistance needs to be considered for accurate prediction of mean heat flux entering a room, regardless of the wall modelled. It is recommended that metal layers be represented by capacity only models, thin insulation layers by resistance only models, thicker insulation layers by lumped or fully distributed models, and concrete layers by lumped or fully distributed models. The recommended number of zones for a lumped model is twice the number used in a distributed model. An eyen distribution, of thermal resistance and capacity between zones in lumped parameter models is recommended.