# [Bldg-sim] Heat Recovery - Effectiveness Calculation

Mark Prince mprince at aeieng.com
Wed Jul 9 15:05:20 PDT 2008

```Good afternoon,

I'm currently modeling a laboratory building HVAC system that has a sensible heat recovery system.  The heat recovery system is a water/glycol run-around loop type system.  In eQuest there is an input, under the airside system tab, that allows you to fill in the effectiveness of your heat recovery system.

My question is this, how should I calculate this effectiveness?

Currently, I've calculated the effectiveness based on the design documents.  According to the equipment schedules the exhaust air is at 72 F, and the outside air heat recovery coil has a scheduled performance of 6 F entering and 35.5 F leaving.  Based on these numbers I've calculated a design effectiveness of 44.6%.  Please see the below equation:

35.5 - 6     =   0.446
72  -   6

However, a colleague of mine is wondering if this is the correct way to determine effectiveness for the eQuest program.  He is wondering if the effectiveness might be calculated based on the design air temperature (DAT) that is always leaving the air handler (55 F), or some other way.

Does anyone know?

Sincerely,

Mark Prince
Affiliated Engineers
5802 Research Park Blvd.