Version Nr. 1-1 - 18.03.2020
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4. Technical functions
Air-air heat exchangers are intended as complementary accessories to large industrial equipment which include
a motor-operated fan or blower together with a heat exchanger module. These may also include an electric
heater. The fan or blower is intended to recirculate air and allow heat exchange. The heat exchanger is
designed for air heat transfer only.
Cooling function may be controlled by an on-board or remote controller or thermostat. Heating function, when
installed is provided by an electrical heating element. The unit seals the cabinet which ensures that the clean air
inside does not come into contact with the ambient air which may well be dirty or polluted. The unit is fit for
purpose within the rated/declared ambient conditions (e.g. dusty and oily air or high air temperatures between
-5°C and 55°C), also indicating the rated allowable ingress and environment.
Heat exchangers are used where the heat generated by energy losses in control cabinets must be conducted
away to protect temperature-sensitive components. The characteristic graph shown in the section “Performance
graph” applies to external (ambient) air as the coolant.
In air-to-air heat exchangers, the internal temperature of the control cabinet cannot be cooler than the ambient
temperature. There are natural limits to the cooling performance, dependent on the air supply temperature and
the requirement for a temperature difference of at least 5K. Unlike systems in which the heat generated is
allowed to escape by air convection through ventilation slots, with the heat exchanger, the clean air inside the
control cabinet is prevented from mixing with the air outside, which may well be unclean.
5. Functional principle
Functional principle
The heat exchanger is a cooling device that creates a heat-transfer through a large area of thin aluminium sheet
metal folded up in the heat exchanger core by means of forced convection. Used within an enclosure, it uses the
ambient air as cooling medium, thus avoiding the utilisation of refrigerant.
The cooling performance of the heat exchanger is dependant on the ambient (external) air temperature. The
internal fan is set to be always on. The external fan is controlled via a thermostat. When the cabinet
temperature increases beyond the pre-set thermostat temperature, the external fan is switched on and the heat
exchanger starts cooling. Cooling stops when the cabinet temperature cools below the pre-set temperature.
Switching difference is of 7K (+/-4K).