Estimating cooling load of an AHU, best methods, degree days??

[Domos]

Can anyone advise on the best way to simulate the cooling and heating loads associated with AHU's when you know the airflow, and desired conditions in the room.

In the past I've used heating and cooling degree days (adjusting the degree day base temperature depending on the room funcitonality but typically allowing for a 2 or 3 degree delta T due to internal heat gain for a room with say 6 Air Changes Per Hour).

However I am becoming increasingly concerned that the results from these approximations are on the low side. I know that for instance using cooling degree days will not take into account auxilary loads on chillers (pumps etc.) and heat transfer efficiencies of cooling coils etc. but none the less the values I am getting still seem extremely low.

Is it necessary to go to more advanced simulation software to get reasonably accurate heating and cooling load estimates?

Can anyone please advise?

 

[MintJulep]

To estimate the magnitude of the loads your kind of have to know what the nature of the loads are.

Using degree days, or design temps only gives you a factor to estimate building envelope loads. They will tell you little or nothing about internal loads that are essentially independant from outdoor temperature, like lighting, office equipment, and people.

An office will be very different from an industrial space will be different from a retail space.

You could SWAG some per square foot numbers for various types of occupancy.