How can I verify calculated heat loss?

[tcdouglas]

Hi all,

I have calculated the expected heat loss (fabric not ventilation) of a room in a house using Q=Ʃ(UAΔT) for each building element (window, door, wall, ceiling etc) making the room. The units are Watts.

How can I measure the actual observed heat loss of the room? I am currently monitoring the internal room air temerature and the external air temerature. Shouldn't I be able to calculate the heat loss after switching the heating off and observing the rate of temerature decrease? Obviously I need the figure in Watts to compare against the calculated heat loss.

Thanks in advance...

 

[Simon Bridge]

Yep - Pretty much how you'd do any heat loss experiment.

 

[tcdouglas]

Thanks for the reply but I was hoping for an equation to plug my temperature readings into...

 

[Simon Bridge]

You don't have a model for heat loss?

The rate of heat loss depends on the current temperature, so it's actually an exponential.
You heat loss calculations assume a constant internal temperature - so they would correspond to the initial heat loss ... which involve curve-fitting.

You can relate a change in temperature to a change in energy right?
Ideally you want to determine this experimentally ... use a heating element of known power to heat air in a well insulated box and measure the temperature - plot Temp vs time. OR you can use one of the many theoretical models for air ... PV=(5/2)NkT (diatomic ideal gas) to get an approximate figure (you should apply such models to your theoretical heat-loss to turn it into a change in temperature).

Of course you could verify directly - since the calculation you did was for equilibrium at a particular operating temp, you can directly measure the energy pumped into the air from the heaters. This should match the heat loss.

 

[sardar]

To verify calculated heat loss, you can use a heat flow meter or thermal imaging camera to measure the actual heat loss in the room. These tools can provide more accurate and precise measurements compared to monitoring temperature changes. Additionally, you can also use a data logger to record the temperature of the room and the external environment over a period of time, and then use this data to calculate the heat loss using the same formula you used for your initial calculation. This will allow you to compare your calculated heat loss with the actual observed heat loss. It is important to make sure that the room is properly sealed and insulated to ensure accurate measurements.