Cooling Time for Air Conditioning

[Annindita94]

TL;DR Summary

How to calculate cooling time

Please advise for cooling time on air conditioning.
I have a project and customer asked me to make a comparison between their requirement and my proposal. And here's the result.

Let's say that we provide a room with same capacity as above, function, delta T, load on that room, but ONLY air flow that is different, how can I know or calculate cooling time for both rooms?

Is it correct that higher air flow will be reduce heat load more faster that lower air flow? If that so, how about the time?
Maybe higher air flow can reduce and reach temp on 1 hour, and lower air flow will reduce temp on 1.5 hours.

Thank you so much for your help before.

 

[hutchphd]

At the lower flow rate, in order to deliver the same BTU/hr, the cooled air must be delivered at a lower temperature. This will affect the mixing or homogeneity of the air in the conditioned space not the delivery of "cool". There may be slight variations from this ideal behavior because on dehumidification, but that will be small I believe.
So the issue is how well the air is mixed after delivery to the conditioned space. The rate of delivery of "cool" should be the same regardless, and the times should be the same.

 

[Dullard]

I agree with hutchpd. Additionally:

'Cooling' (for human comfort) is a combination of temperature reduction and de-humidification. 'Faster' isn't necessarily 'better' in that situation. An ideally sized system will run 100% of the time on the hottest day of the year (maybe 95% to account for future global warming?). If this system is to be used intermittently, humidity removal will likely dominate the cooling time - the 2 systems aren't significantly different in that regard - the proposed unit will (theoretically) produce a lower humidity result. The differences between 'proposed' and 'required' are very small after allowing for variations due to actual duct/return performance.

 

[russ_watters]

"Cooling time" is not generally a useful consideration for sizing HVAC systems, and substantially oversizing can cause problems, depending on the system type. Oversizing can cause humidity problems, may reduce efficiency, and of course costs more.

 

[Lnewqban]

Bad: Higher airflow means more noise, less contact time in coil for dehumidification and additional heat transferring into supplied air from the blower motor.

Good: Higher airflow means longer throw of diffusers, less air stratification and hot pockets formation (if any) and more evaporative effect on human skin (which induces the perception of cooler environment).

 

[sophiecentaur]

"Cooling time" is not generally a useful consideration for sizing HVAC systems, and substantially oversizing can cause problems, depending on the system type. Oversizing can cause humidity problems, may reduce efficiency, and of course costs more.

That all makes sense but doesn't the optimal solution depend on the application. If AC is not used continuously and, as with heating systems, they are often used when no one needs them, then reaching a desired temperature quickly can be a good thing.

From what I have seen, the philosophy of AC seems to lag behind that of Heating. People are only too aware of the need for insulation in cold climates but not so much in hot. I think that point should be made in a thread like this.