# Thermodynamics - Problem in calculating a values

1. Apr 11, 2013

### pottersj

Hello, I am having difficulty in calculating F and was wondering if anyone could help.

F is the heat flux in W/m2 between the Heat Pump-House system from the Atmosphere.

Now I have the Energy 'lost' from the house walls into the atmosphere.
If we don't consider any other parameters, this energy would be the same
exact amount of energy that I need to add into the House to maintain a
constant temperature.

By looking at some of the Heat Pump specs and by knowing that the
Coefficient of performance is 2.5 I should be able to calculate the
energy heat has to transfer from the outside into the inside.

The difference between the heat flux lost from the House into the
atmosphere and what the heat pump extract from the atmosphere would give
me the NETT COOLING of the atmosphere due to the Heat Pump. Which is my
F in W/m2.

Now I'm a bit confused on how I go and do that really... Im fine with
the sentence before the bold text but then I just get lost...

Thanks

John

2. Apr 12, 2013

### Simon Bridge

If you know the rate that heat is leaving the house, then you divide that by the surface area of the house to get $F_{out}$.

$F_{in}$ will be a rating written on the heat pump or in it's documentation.

$F=F_{in}-F_{out}$
... would be the net heat flow into the house.
If this is a negative number, then heat flows to the outside and the atmosphere would warm up.

You problem is that the heat from the atmosphere may not all end up in the house right?
You also use energy in the heat pump which produces heat of it's own.

Of course the effect on the atmosphere depends on a lot more than just the heat flow through your house.