Heat in kW= flow rate(is/s) x specific heat capacity of water( constant 4.2) x temperature difference of flow and return( usually 10 degrees c) unless using lower temps for say underfloor heating or heat pumps .
So think what they are looking for is the difference between flow and return temps
thanks for the answer but that still confuses me as I am a total novice to all of this in plumbing. I keep reading the question and I think, I could be totally wrong here but could the information that I need to work out the flow rate need to be, size of pipes, size of pump and boiler number of radiators, would any of this effect the flow rate? could there be anything else?
Been 20 years since I looked at this stuff , bear with me as I look this up,
Sorry it would take forever to go through all this. You need to find thge heat loss . the temp diff between flow and return. Then find the heat losses through pipe work ( length of run from boiler to rad)plus fittings.
plusim assuming you have all the tables