Describes a simultaneous model which permits the determination of the time-dependent variation in temperature and humidity and the corresponding heat fluxes of the different components in the interior air of a bus or similar vehicle. States model is mainly for simulating solar heat gain and to optimise the HVAC system. It is also possible to study the effects of modifications to the vehicle structure and the components of the air conditioning system on the on the interior climate. States the model takes account of changing solar radiation with reference to place, date, time of day and cloud cover. The HVAC system of the vehicle is integrated into the model. States model predictions and measurements are in good agreement.

KEYWORDS: Calculating, air conditioning, temperature, heat flow, buses, humidity, solar heat gain.