Hot water reset controls

[DuctHunter]

I am trying to do some calculations on a spreadsheet on how much energy savings can be incurred by a building if they add Hot Water Reset controls to the boiler. During my internet searches for knowledge on the subject and hints on the calculations I came across an article that said there is an equation that states "the rate of heat output is proportional to the difference between the building's inside air temperature and the water temperature supplied"

In other words Q = k x (Twater - Tinside air) Where K is a constant that depends on the type of heat emitter used (in this case it is water), and Q is the heat output, Twater is the supply water temp and Tinside air is the room temp. I personally have never seen an equation that relates the temp difference between supply water and room temperature.

So my question is. Does anybody know where this equation comes from or how to derive it ?

I have posted the link to the article if it helps. I don't want to re-invent the wheel, but I also don't want to blindly use an equation without knowledge of where it comes from.

Thanks for your help.

 

[Drazen]

you have that equation applied to each and every heating body, that is simply equation of heat transfer between heating body and indoor air.

of course, that means finding k falls into all that complexity of heat transfer theory.

for heating bodies, manufacturers conduct testing according to some of standard, than they declare capacity and derive k from their measurements.

for the whole building, i think it is not the point. the equation you find out just points at core characteristics of process.

if you want to make comparison between different temperature regimes, you can assume that k will be constant over some temperature range, so you establish similarity formulas.

to find k for some particular heating body, you can google some manufacturers like radson , vogel & noot or whoever you have in your area.