Perforated Pipes forced air ventilation under slab of warehouse

[aghorabah]

I have warehouse working at -20c
with heave frost protection system
consist of perforated pipes 4 inch diameter and 34 meter lenght 9 holes around the diameter
the number of pipes is 50
I need to calculate the required air flow for this system

[Magoo]

Why have holes in sub structure ventilation pipes ? I think the holes will allow moisture ingrees to sub structure where you do not want it.

[airtrackinc]

it’s around always good to go with complete heat load and heat gain calculation to find the actual Air flow