An air coliditioning system must meet a number of requirements. Firstly, it must remove or supply heat in order to maintain a convenient temperature level and to supply the room with a given amount of fresh air. However, it is not sufficient that the air is supplied in the correct amount with the correct temperature; it must also be distributed with regard to the heat sources in order to obtain a uniform thermal condition in the occupied zone of the space. Fig. 1 shows a sectional elevation of a room. The air is supplied from a diffuser at the ceiling and develops into a wall jet running under the ceiling. In this jet it is easy to predict entrainment, temperature and 'Velocity profiles, and the diffuser is often so designed that the velocity falls to a given low value (i.e., 25 cm/s) when the jet has reached 3/4 of the length of the room. Away from the ceiling region, however, the simple relation between, say velocity .and distance from diffuser will disappear - the jet is said to disperseand other parameters such as the dimensions and geometry of the room, the distribution of load,and the temperature difference between supply and return will have a strong influence on the flow. If a calculation of entrainment, temperature and velocity profiles in the occupied zone is wanted, all of these parameters must be taken into consideration.

This paper will describe a new method which can predict the flow in all regions of the room, including the occupied zone, taking all the mentioned parameters into consideration. The procedure is based on the solution of the flow equations - five nonlinear partial differential equations - by means of a numerical method.

This paper also shows how the predicted velocity and temperature distribution can form ~he basis for determining the level of comfort attainable in the room with a given diffuser at varying loads and air flow rates.