How to identify load and efficiency of the air-conditioning system

This chapter refers to the owners of automobiles where they want to set up air-conditioner. On the ground of below information you can choose correctly the required type of the air-conditioner to set up in the automobile.

Load of the air-conditioning system

Though during the automobile parking at hot weather one can feel extremely high temperature above the automobile and inside of it, the reason for it is the influence of the sun heat radiation, and the automobile temperature is increasing up to balancing of radiation and scattering heat from the automobile surface.

Temperature load of actually operated automobiles, beside the sun heat, includes the heat transmitted by the engine through the floor, division between the engine and automobile cabin, heat loss from the saloon ventilation (natural and deliberate ventilation), heat from passengers’ bodies. They are defined depending on external conditions (outside air temperature, humidity, automobile speed):

• from the radiated sun heat, the heat passing through side walls.
• from the transfer of the radiated heat, the heat passing through the ceiling.
• from the transfer of the heat, the heat penetrating from the glass surface.
• the heat penetrating from the floor and partition.
• from natural and deliberate ventilation.

Example of calculation of the refrigerating system load.

(Under the condition): outside temperature 35°С, relative humidity 60%, saloon temperature 25°С, automobile speed 40 km/hour, sunshine.

Efficiency of the air-conditioning system

Installation of the air-conditioning system serves for the heat transfer from the low temperature zone to the high temperature zone. When evaluating its efficiency, it is enough to designate quantity of heat per unit time which is able to move from the low-temperature zone to the high-temperature zone, and "Btu/h"units are used. That is efficiency of the air-conditioning system, that is, refrigerating system.

Only, even if the system is similar, when changing of temperature from the low pressure side (evaporator temperature) and temperature from the high pressure side (condenser temperature), that is vaporization temperature and condensation point, efficiency of the air-conditioning system is also changed. Therefore, efficiency calculation is made for the standard cycle with vaporization temperature 0°С C and condensation point 30°С.

If in the real automobile, after defining traffic road provided creation of a certain value of circulation and vaporization temperature of the refrigerant, one will estimate efficiency, it will be determined depending on the volume of the blower ventilated air (volume of the circulation air in the automobile sallon), temperature of suction inlet, humidity (average temperature, humidity in the automobile saloon).