The response of the cooling and dehumidifying coil is an important part of the system analysis of an air conditioning plant, and it is, therefore, necessary to obtain a model which describes its dynamic behaviour realistically.

K. R. McCullagh (1) in the paper entitled "An Analysis of Chill Water Cooling and Dehumidifying Coils Using Dynamic Relationships" has set up a mathematical model of the cooling and dehumidifying heat exchanger. This was an investigation of steady state performance only, for varying load conditions of cooling and dehumidifying coils.

In this paper the same equations are used to find the frequency response in two ways:

(a) Using a step change in inlet water temperature for different water and air velocities and then finding the frequency response by graphical analysis of a group of vectors, or by a numerical method.

(b) Using sinusoidal input signals of varying frequencies in the operational analog and recording the output signals.