Prediction of cab climate

Abstract

A simple model of the heat fluxes around a cab enables the temperatures inside the cab to be predicted. These may then provide an indication of the heat load a driver would experience. The model assumes the cab is in thermal equilibrium under the influence of steady heat fluxes. The cab captures short-wave (solar) radiation and this gain is balanced by long-wave radiative and convective losses. The external surface temperatures at which this balance occurs are estimated and then used to predict the internal temperatures. The cab is regarded as an enclosure comprising a number of panels (10 or 19) each of which participates in these heat exchanges. The model exists as a computer program which has been written to assist a cab designer who is concerned with the thermal environment around the driver. A designer may use the model (1) to evaluate the effects of changing cab shape or solar-optical properties of the panels or (2) to estimate the ventilation or air-conditioning required to make the environment in a particular design of cab acceptable to the driver. The weather conditions applicable to the model are not restricted, but comparisons with field measurements have used data typical of a British summer. Three cab designs were used for these comparisons.