COOLING AIRCOOLING AIR

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Hello, I would like to show you the three Hello, I would like to show you the three most common methods of cooling air.most common methods of cooling air.

Usually, the main function of an air Usually, the main function of an air conditioning system is to cool the air in conditioning system is to cool the air in the zone to a desirable temperature. In the zone to a desirable temperature. In most cases this will mean a room most cases this will mean a room temperature in the range of 23.5 temperature in the range of 23.5 °°C to C to 24.5 24.5 °°C.C.

The three most common methods of The three most common methods of cooling air are:cooling air are: direct air cooling with refrigerated direct air cooling with refrigerated

cooling coilscooling coils indirect air cooling with chilled water indirect air cooling with chilled water

coilscoils evaporative cooling.evaporative cooling.

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Let’s look at a Let’s look at a direct air cooling direct air cooling system with system with refrigerated cooling refrigerated cooling coils.coils.

Direct air cooling Direct air cooling systems with systems with refrigerated cooling refrigerated cooling coils are air coils are air conditioners which conditioners which use a refrigeration use a refrigeration system to directly system to directly cool the air being cool the air being supplied to the supplied to the zone.zone.

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In these systems the In these systems the evaporator would be a finned evaporator would be a finned evaporator with 2–3mm fin evaporator with 2–3mm fin spacings.spacings.

The evaporator temperature The evaporator temperature would be expected to have a would be expected to have a saturation temperature of saturation temperature of approximately 2 approximately 2 °°C to 5 C to 5 °°C but C but this could be slightly higher on this could be slightly higher on units which have special units which have special applications.applications.

Generally, the lower the Generally, the lower the evaporator temperature, the evaporator temperature, the more moisture will be removed more moisture will be removed from the air. Therefore, those from the air. Therefore, those systems which have a high systems which have a high latent heat load could have a latent heat load could have a lower saturation temperature lower saturation temperature than others to assist in the than others to assist in the removal of the moisture from removal of the moisture from the air.the air.

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This water is then pumped to cooling coils which are very similar to an This water is then pumped to cooling coils which are very similar to an evaporator coil.evaporator coil.

Air passes through these coils which, at 5 Air passes through these coils which, at 5 °°C, are at a similar C, are at a similar temperature to what an evaporator would be, and therefore the air temperature to what an evaporator would be, and therefore the air gets a similar amount of cooling as it would in a directly refrigerated gets a similar amount of cooling as it would in a directly refrigerated system.system.

Indirect air cooling Indirect air cooling with chilled water with chilled water coils is an alternative coils is an alternative system to the direct system to the direct cooling by cooling by refrigerated coils.refrigerated coils.

This system has a This system has a refrigeration unit to refrigeration unit to chill an amount of chill an amount of water to a water to a temperature of temperature of approximately 5 °C. approximately 5 °C.

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As the air passes through the water some of the As the air passes through the water some of the water evaporates thus absorbing latent heat of water evaporates thus absorbing latent heat of evaporation, most of which comes from the air. This evaporation, most of which comes from the air. This has the effect of dropping the temperature of the has the effect of dropping the temperature of the air.air.

These systems are not suitable for all applications These systems are not suitable for all applications and do not work as efficiently as refrigerated and do not work as efficiently as refrigerated systems. systems.

Evaporative Evaporative cooling systems are cooling systems are very different to very different to those already those already discussed. These discussed. These systems pass air systems pass air through a screen through a screen which is wetted with which is wetted with water.water.

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