# Thermal power of the air extracted from a building

1. Jan 19, 2016

### ricardo46

Good afternoon.
I need to know if the thermal power of the air extracted from a building is greater than 80kW.
I know the flows entering and leaving the building. Also, I know the temperature of the air inside and outside the building.
How do I calculate the power of the air extracted?
thank you

2. Jan 19, 2016

### SteamKing

Staff Emeritus
You'll need to know either the specific heat of the air at the temperatures encountered or know the enthalpy of the air. The latter will depend on temperature and humidity.

3. Jan 20, 2016

### ricardo46

Ok. I know the specific heat. I have solved problems like this in the past. Im just a bit rusty.

I think I have found the solution:
P = Cp·flow·DeltaT

I am just not sure about the units:
P- power (W)
flow- m3/sec
DeltaT- temperature diference between the inside and the outside of the building
Cp- specific heat (J / (kg . ºK))

Is this correct?

4. Jan 20, 2016

### SteamKing

Staff Emeritus
Seems to be.

5. Jan 20, 2016

### ricardo46

I think I cant use the flow like this. If i use it like this i wont get the power in watts but this W.m3/kg.
What should i do to get watts?

6. Jan 20, 2016

### SteamKing

Staff Emeritus
You can convert the volumetric flow to a mass flow, using the temperature of the air to find its density.