As an order of the "Bundesanstalt für Arbeitsschutz und Arbeitsmedizin" different types of mobile air-conditioners were investigated to get information how to correctly select and handle them. The cooling capacity, consumption of electrical energy, coefficient of performance, noise production, concentration of micro organism, temperatures and velocities in the supply jet were measured under summer conditions. Typical tube and split units in the middle range of capacities were chosen.

Only the sensible cooling capacity is relevant. It is by a factor of 1,5 to 2,5 smaller than the maximum capacity given by the manufacturers. The sensible cooling capacity of the investigated tube units was in the range of 1,0 to 1,2 kW and 1,4 to 2,0 kW for the split units with the same dimensions of the units. The coefficients of performance (COP) showing the relation of the sensible cooling capacity to the consumed electrical power are in the range of 1,1 to 1,4 for all units for a high number of revolution. For lower number of revolution the COP reaches 1,7 for tube units and 2,2 for split units. A one tube unit with a wet condenser reached the best COP of 2,3.

The A weighted noise power was assessed as a measure of the produced noise. The results for the high number of revolution are: tube units 61 to 65 dB(A), split units 51 to 55 dB(A). There are uncomfortable draught and temperature in the air jet in front of the unit. Outside the jet in a lager distance temperature and velocity are comfortable. The emission of micro organism is not problematic if good maintenance can be presumed. Two methods to estimate the required sensible cooling capacity are suggested.

The required mobility is another aspect for the choice of the unit. Tube units have the best mobility but the smallest capacity and COP, except a one tube unit with a wet condenser. Highest capacities can be realized when the tubes are connected to fitting wall openings and the windows remain closed. The ventilation is then performed by air from inside the building, which is seldom possible. Positioning the tubes of a two tube unit in a slot of the window by using the delivered special nozzles enable agreeable capacities as long as the slot is small.

The name "mobile air conditioning unit" is not correct from the view point of air-conditioning definitions. The unit is only a chilling unit, because it is only able to cool and to dehumidify the air.

Please download the complete report "Performance of mobile air-conditioners" (in German only).