I'm a student currently working on a market research project on the HVACR industry, and I'm having trouble nailing down a simple answer to these questions (it may be there are no simple answers, as so far it seems like it varies on many factors of the data center).
Thanks in advance!
It depends on how the system is designed. Depending on the climate, they might be blowing a constant stream of outside air through the data center or they might be using an air handling unit (in which case there might be little mass exchange with outside air but a lot of temperature exchange). The level of energy costs from HVAC in a data center is typically measured by power use effectiveness (PUE), defined as (total data center energy use)/(energy used by the computers). Whether it's "stressful" on the HVAC system depends on your definition. Certainly many data centers have to throttle their processing in hot weather.
Humidity control is important in preventing damage to equipment. See this ASHRAE spec: https://www.ashrae.org/file%20library/technical%20resources/bookstore/supplemental%20files/referencecard_2021thermalguidelines.pdf
So many factors:
How much heat does the equipment give out?
What is the required ambient temperature?
Does the humidity need to be controlled?
Does the environment need fresh air - do people work in there?
What is the volume? How much air needs to be moved? And how many times per hour?
Once you can start to give values for these you can start to work out the cooling capacity required, the volume flow rate and the pumping capabilty needed.
Once you have those then you can work out the energy input needed and that will lead you to the costs.
Also consider all sources of heat ie does it have windows - does that allow solar heating? Are there cooler areas that need to be considered as well...
Not an easy problem, needs careful analysis of many factors.
