Heat transfer calculations

[taxes]

I am probably trying to be too clever but is there a quick way of calculating the heat transfer of underfloor heating from a alupert 16 mm pipe through a screed 65mm thick and ceramic tiles into the air in a room?

I realise this involves the following

1) Pipe to Screed Conduction
2) Screed to tiles Conduction
3) tiles to air Radiation
4) Air circulation Convection.

I know the formulae for each stage but is there a calculator or spreadsheet application available?

What I am trying to do is calculate the warmup time

Thank you

 

[kay-jay]

Take your socks off. Fire up the heating start your stopwatch and stop it when your feet get warm [emoji38]

 

[townfanjon]

The idea of Under floor heating in a screed, is the screed becomes the thermal mass and keeps the heat in the screed, so in other words when you turn it on ....... You leave it on, don't do the on , off on ,off on off thing, so you shouldn't need to calculate a heat up time.
I did one in my pals a few years ago and on its first warm up it was 2/3 hours before you felt anything, but I warmed it up very slowly so's not to crack the screed.

 

[Rybo_1]

I Hope you left a day a mm to let the screed go off

 

[Ermintrude]

Well you should assess the macroscopic thermal currents in the screed and the boundary layer dynamics also account for the reduction in density and the effects that has at boundary layer. The adhesive may not be solid so look at convection between surfaces. The emissivity of the floor will vary with colour and even the grout. Having lights on will alter it too. Or just calculate room losses and the time it takes to heat room by 5c.

 

[Ermintrude]

Well you should assess the macroscopic thermal currents in the screed and the boundary layer dynamics also account for the reduction in density and the effects that has at boundary layer. The adhesive may not be solid so look at convection between surfaces. The emissivity of the floor will vary with colour and even the grout. Having lights on will alter it too. Or just calculate room losses and the time it takes to heat room by 5c.

Warmup time is more to do with thermal inertia and loss from surface

 

[townfanjon]

Well you should assess the macroscopic thermal currents in the screed and the boundary layer dynamics also account for the reduction in density and the effects that has at boundary layer. The adhesive may not be solid so look at convection between surfaces. The emissivity of the floor will vary with colour and even the grout. Having lights on will alter it too. Or just calculate room losses and the time it takes to heat room by 5c.

Like I said, just leave it on lol

 

[taxes]

Well you should assess the macroscopic thermal currents in the screed and the boundary layer dynamics also account for the reduction in density and the effects that has at boundary layer. The adhesive may not be solid so look at convection between surfaces. The emissivity of the floor will vary with colour and even the grout. Having lights on will alter it too. Or just calculate room losses and the time it takes to heat room by 5c.

You forgot to mention the Stephan-Boltzman constant!! Of course I Know the room heat losses. I want to know how to calculate the warmup time. How do you do that simply?

 

[taxes]

I don't intend to turn the heat on and off many times as in other types of central heating, but I don't intend to leave it on full heat when the room is not being used. i.e. there will be a main temperature and then a night-set-back type of setting.

 

[taxes]

I left it a lot more than that, using no heat.

 

[Ermintrude]

From cold time it till it's warm. Your setback temp should only be about 3c

 

[Dotty]

As above. Turn it on, leave it on and don't worry about it.

As for the warm up time, no point in trying to calculate that as there are factors that will be constantly changing from day to day. It is what it is. Don't worry about it.

 

[taxes]

Sorry guys but I treat this as a serious subject. I had hoped there was a short cut approximation so I am setting up a spreadsheet to deal with it and will post the results, but don't hold your breath.

 

[Dotty]

Don't worry. We won't.

Thread closed as it's getting boring trying to reinvent the wheel and explain why it's pointless.