Heat Build Up-Enclosed Space 1

[TECMSC]

I have a room with transformers producing 126mbtu. The room is 885 sqft with 10 ft ceilings and no envelope loads. The room is presently cooled with a CHW AHU. If the AHU fails: How much time will it take for the room to heat up 15degrees? I'm trying to figure it out on paper with no luck other then...quickly!
Thanks

 

[sailoday28]

The following questions should be considered.
1. Is there a possibility of ventilation do to naturual convection during the heat up.
2. What other mass (heat sinks) is (are) in room.
3. Other surface areas for convection and radiation.
4. Actual free volume of air in room.
5. What if any heat trans coefficients are used for cooling of transformers with CHW AHU. With the loss of these units if coefficients are lower, then what is impact on transformers.

 

[quark]

If this is an existing system, then the calculation is not very difficult. First of all, calculate total heat load by taking DBT and WBT at air entry and exit of the room. You can find out the enthalpies from the psychrometric chart and use the formula Q = 4.5 x cfm x dH, Q is heat load in btu/hr, dH is difference in enthalpies in btu/lb.

Once you derive the total heat load, go to thread403-135514 for further procedure.