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MURTUZA ZAVERI
MURTUZA ZAVERI • Jul 20, 2017

DESIGNING A FAN FOR HEAT EXCHANGER

I Have got to design a cooling fan, to cool the network of pipes of a heat exchanger.

the only data that i have in hand is, the initial temperature of the hot fluid flowing in the pipe, and the final low temperature to which it has to be cooled. the sweep diameter of the fan has to be not more than 500 mm. the fan has to be directly powered by an electric motor running on alternate current.

i have to design this fan from the scratch. does anyone know the required design procedures and formulae. ? also tell me what effect the number of blades of a fan has on the airflow .

please also tell me the motor selection process (even though this has to be done only after the fan has been designed)
Is this finned tube exchanger?
See these sites:
1. SHORTCUT SIZING FOR AIR COOLED HEAT EXCHANGER
Shortcut Sizing for Air Cooled Heat Exchanger – ChE Guide
2. Fin Fan Air Cooler Selection and Sizing
https://kolmetz.com/pdf/EGD2/ENGINEERING_DESIGN_GUIDELINES_fin_fan_air_cooler_rev_web.pdf
3. Air Cooled Heat Exchangers
https://thermopedia.com/content/551/

If you know the total heat load and the tube side area, the overall HTC can be calculated. For a preliminary design ignore the conduction coefficient of the tube. From the tube side flow parameters evaluate the tube side HTC. From these two get the airside HTC. From published data get the velocity of air to give the required HTC. From the geometry of the exchanger the pressure drop can be evaluated. Choose a fan with require flow rate at the estimated pressure drop from data supplied by fan manufacturers.

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