Valeooscope - Air Conditioning System Thermal comfort loop

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Introduction to air conditioning systems

8.1 The role of air conditioning

Cold production system : The air conditioning or A/C loop

We have all felt the discomfort of being too hot in a car, even in temperate climates. The only solution until relatively recently consisted in turning up the ventilation in order to speed up the circulation of air inside the cabin. Surveys have shown that, from the physiological perspective, increasing the ventilation can, to a cer- tain extent, compensate for a rise in temperature. For example, a temperature of 24°C in still air is equivalent to a temperature of 30°C in air that is moving at 1.5 m/s, with a relative humidity of 50% in both cases. But this remedy is no more than an interim measure that quickly becomes insufficient, as soon as certain temperature and humidity limits are exceeded. In reality, even the very best ventilation systems make no difference above 30°C and 70% relative humidity. And the higher speed of the air flow often results in intolerable sensations on long journeys. The required level of comfort under any climatic condi- tions can only be achieved with an air cooling system. The main role of air conditioning can be defined as follows: «To guarantee the climatic comfort of the occupants by treating the air and providing controls that are easy to use.» Climate control also fulfills another function: «To make sure that the visibility through the cabin’s windows is quite clear.»

8.2 Overview of the air conditioning system

Vehicles are fitted with air conditioning systems for purposes of thermal comfort and safety. The basic principle consists of circulating a flow of thermally treated air inside the cabin. The air conditioning system fulfills the following functions: g Treatment and distribution of air: the air circuit and the air conditioning g Production of cold: the air conditioning or A/C loop g Control of the system : the control panel and the air conditioning Electronic Control Unit (ECU)

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