IPVMU Certified | 03/26/15 10:06pm
I think the trick here is to convert your values into usable terms. BTU/hr per square foot/meter is not going to help find you the right housing.
Most environmental housings are specified by operating range. Take this example from Moog (Thermiq):
They do figure EPA, but it is not expressed in terms of heat transfer. Instead, you are left with an "Operating Temperature" of -50F up to 140F, with 'spikes' up to 165F.
Granted that is a rather imprecise value and range, but that's the metric used by housing manufacturers. No RH or entropy is part of that figure. :)
So, with that out of the way - can you restate the application as a min/max operating tempature value?
The problem is that we are not talking about ambient heat. We are talking about radiated heat, like the sun or a flame or a heat lamp.
For example the enclosure that you show is speaking about a ambient temperature of 140F. That means the air temperature around it is 140F. But what if the Sun is directly shining on it overhead? Does it matter? Sure does.
Direct Sunlight irradiates 97 W power per square foot. How much of a temperature rise that will cause depends on the size, shape and heat dissipation of the enclosure itself. So the OP is correct in specifying the radiated energy that must be dissipated. Note the the radiation values given in the OP are orders of magnitude higher than Sunlight. So high in fact that the ambient temperature may not even be a significant factor.
Think microwave oven, does it make much of a difference how hot the air is inside the oven to how fast your food heats up?
An active cooling system possibly including freon/puron is likely necessary.
@Sripad, to spec the enclosure it would be helpful to know the camera dimensions and if there are any restrictions on the size or shape of the enclosure.