Compact fans for AC and DC

Selecting the correct fanInformationDC axial fans1. Dissipated energyA large amount of the energy consumed by electrical and electronicdevices is converted into heat. In selecting the correct fan, therefore,it is important to determine the dissipated energy that must be removed.The electrical power consumption of the unit to be cooled, oftenrepresents a suitable value for this purpose.2. Permissible temperature riseThe air flow which the selected fan is required to generate, is determinedby the dissipated energy and the permissible rise (∆T) of thecooling air flow (from entry to exit of the device to be cooled). Themax. allowable ∆T depends greatly on the temperature sensitivity ofthe individual device components. ∆T = 5K means e.g. that the averageair flow leaving the device to be cooled may only be 5°C warmerthan the ambient temperature (a large volume of air is required for thispurpose). A lower air flow rate is sufficient if a higher temperature difference(e.g. ∆T = 20K), can be tolerated.3. Required cooling air flow• In the below diagram a horizontal line is drawn from the dissipatedenery to intersect with the selected ∆T line.5000100050030020015010050302010Waste Heat Pv WattExample : P v = 300 W att∆ t = 10 K90 m³/hAir Flowm³/h5 10 20 30 40 50 100 200 300 500∆ t 20 K∆ t 15 K∆ t 10 K∆ t 5 KPa35302520151050,02 0,04 0,06 0,08 0,10 0,12 [in H 2 O]0• Read down from this point to obtain therequired value for the cooling air flow.The diagram is based onthe following formula:V· [m 3 /h] ≈ 3 ·0,4 0,8 1,2 1,6 2,0CFM1 2 3 4 m³/hPv [w]∆T [K]Optimum OperatingRange4. Optimum operating rangeThe required fan, however, must also be ableto deliver a suitable static pressure increase∆pf, in order to force the cooling air throughthe device. A fan must therefore be selectedthat provides the required air flow performancewithin its optimum operating range (see alsothe air performance curves under technicaldata).5. Fan selectionIf the requirements of an application are fulfilledby more than one fan, the noise level,space requirements, economy and ambientconditions will assist in making the final choice.13Representatives Accessories AC centrifugal fans AC axial fans ACmaxx / i-maxx DC fans - specials DC centrifugal fans