Is there a maximum 15 mm pipe length from the 22 mm ring?

[Dan Robinson]

4.1813 actually

 

[Steelmasons]

I beg to differ.
....and don't start with the LLH sizing..
Maybe some homework for D-Hailsham?...

 

[ianniann]

I understand the formula, but where do you get the flow rate of 0.14 litres/sec from?

Probably an arbitrary maximum acceptable flow speed was multiplied up (or down) by the cross-section of the pipe. Looks like 1 m/s was chosen for this example.

 

[Dan Robinson]

I understand the formula, ?

Apparently not.

 

[Roger928]

15mm tube will carry a 6kw load @ 10c dt. (0.14 x 4.2 x 10c = 5.8 kW)
15 mm tube @ 20 dt (0.14 x 4.2 x 20c = 11.6 kW)

A load of cock and bull.
The same flow rate can't deliver double the energy.

Doubling the temperature drop will have a relatively small effect on the heating surface required but will reduce the flow rate by half.
CIBSE

 

[Dan Robinson]

How does that relate to the equation?

 

[D_Hailsham]

Probably an arbitrary maximum acceptable flow speed was multiplied up (or down) by the cross-section of the pipe. Looks like 1 m/s was chosen for this example.

That was obvious.

But, unless you know that 0.14 is the flow rate (litres/sec) which gives a velocity of 1 m/s in a 15mm pipe , it is just a number plucked out of the air. Pity the pro's were unwilling/unable to explain that it was an empirical formula.

 

[Agile]

A load of cock and bull.

The same flow rate can't deliver double the energy.

I have to disagree with that.

With double the temperature drop then double the power can be achieved.

Your brain is assuming the same rad.

To get double the energy at the same flow rate you need double the rad size!

Tony

 

[Roger928]

He used the same flow rate in each example.
And increased the last number in the second example.

I think he has just solved the worlds energy crisis. Keep increasing the last number and more energy flows out the end of the pipe for the same flow rate.

 

[Roger928]

With double the temperature drop then double the power can be achieved

This is a 15mm pipe he is relating too. You can't double anything and achieve a greater output when the flow rate remains the same.

Doubling the temperature drop will have a relatively small effect on the heating surface required but will reduce the flow rate by half.
CIBSE

 

[Roger928]

The pressure drop is also 820 pascals per meter in both cases. Double the maximum recommended.

 

[D_Hailsham]

The same flow rate can't deliver double the energy.

It can, if you double the temperature differential.

Doubling the temperature drop will have a relatively small effect on the heating surface required but will reduce the flow rate by half.

That assumes you are delivering the same amount of heat.

 

[Roger928]

It can, if you double the temperature differential.

Which doesn't apply to a pipe.
Kw from the end of the pipe remains the same when the flow rate remains the same.

Are you saying that the end number changed to 30 will deliver 17 kilowatts to the room with the exact same flow rate?

 

[Dan Robinson]

You're still assuming you are using the correct input in the formula.

 

[Steelmasons]

A load of cock and bull.
The same flow rate can't deliver double the energy.

Doubling the temperature drop will have a relatively small effect on the heating surface required but will reduce the flow rate by half.
CIBSE

I suggest you further educate yourself , I'm not handing it to you on a plate...