An analytical model for combined air conditioning unit

The design of evaporative cooling units is an importation area in the development of air conditioning systems. However, the current literature lacks the methods that describe engineering calculations for indirect evaporative cooling units. The paper describes a combined two-stage air conditioning unit (first stage – evaporative cooling, second stage – vapor compression); and its scheme is shown. An analytical model of the unit is proposed, and basic relationships and allowances used in the calculations are given. The calculation sequence is described. It is shown that the unit efficiency depends on the temperature efficiency of the indirect evaporation heatexchanger. The proposed model facilitates engineering calculations for the combined unit and determination of external integral parameters such as cooling capacity of the whole unit and each of its stages, power and water consumption as well as air and cooling contour parameters that are required for the selection and design of the main components of the scheme. The described analytical model is created using a Visual Basics for Application program.

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