ABSTRACT
An air conditioning plant is designed to maintain specified internal air temperature and humidity when the expected design heat gains and losses occur. The Chartered Institution of Building Services Engineers (CIBSE) method of calculation of these plant heat loads is explained with the minimum of background theory. Trigonometry is used to find the components of the solar irradiance that is at a right angle to the irradiated surface as this is used to calculate the heat gain. Heat transmission through glazing and the effect of different types of glass are explained. Sol-air temperature is introduced for the calculation of heat gains through opaque structures. The ideas of transient heat flow into and out of the thermal storage capacity of the walls; roof and floor lead to the use of a 24 hour mean heat flow and a swing, or cyclic variation. The plant cooling load can be found from these methods. It relates the sun position to a building.
