Thermal power of the air extracted from a building

AI Thread Summary
To calculate the thermal power of the air extracted from a building, the formula P = Cp·flow·DeltaT is suggested, where P is power in watts, flow is in m³/sec, DeltaT is the temperature difference, and Cp is the specific heat. It's important to convert volumetric flow to mass flow using the air's density to ensure the units are consistent and yield power in watts. The specific heat of air is necessary, and the enthalpy may also be considered depending on temperature and humidity. The discussion emphasizes the need for accurate unit conversions to achieve correct calculations. Understanding these principles will help determine if the thermal power exceeds 80kW.
ricardo46
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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
 
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ricardo46 said:
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
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.
 
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SteamKing said:
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.
Ok. I know the specific heat. I have solved problems like this in the past. I am 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?
 
ricardo46 said:
Ok. I know the specific heat. I have solved problems like this in the past. I am 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?
Seems to be.
 
SteamKing said:
Seems to be.
I think I can't use the flow like this. If i use it like this i won't get the power in watts but this W.m3/kg.
What should i do to get watts?
 
ricardo46 said:
I think I can't use the flow like this. If i use it like this i won't get the power in watts but this W.m3/kg.
What should i do to get watts?
You can convert the volumetric flow to a mass flow, using the temperature of the air to find its density.
 
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