"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Doctor Drivel wrote:


11C Temperature Difference Between Flow and Return
(81C flow - 70C return)

Pipe Size (mm) - approx kW/hour

15 - 6.0
22 - 13.4
28 - 22.5

What the hell's a kilowatt per hour? [Bearing in mind that a kilowatt in
its
own right is a measure of energy consumed/delivered per unit time]

BTU/hr & kW = power
kW/hr & BTU = energy

Firstly, separate power and energy; this confuses many people.
Energy is Power x Time. A BTU is energy. Put it over one hour (energy x 1)
and we have "power"..... BTU/hr.

- The watt (W) - Is a unit of "power".
- kilowatt-hour (kWh) - This is a 'unit' of chargeable electricity and is a
unit of "energy". Yiou buy energy. Power results from the energy.

The kilowatt (kW) is simply 1,000 watts. A traditional electric heater rated
at 1,000 watts, or ten 100 watt light bulbs will consume one kilowatt
(power).

In your electricity bill, what you pay for is the product of power and time.
This is obvious - the one kilowatt electric heater on for three hours is
going to cost three times as much as for one hour. Therefore the chargeable
electricity 'unit', on your bill, is the kilowatt-hour (kWh). This is by
tradition in the world of electricity metering called a 'unit'. What you
are paying for is energy, rather than power

One unit of electricity (one kWh) buys you a:

- 1 kilowatt electric heater burning for one hour.
- 100 watt light bulbs burning for ten hours.
- 8 kW shower for seven-and-a-half minutes.

The one 1 kilowatt electric heater running for six hours would use six
units, but if you left the 8 kW shower running for half an hour it would use
four units.

Electricity meters give readings in 'units' (kWhs) directly. This simplifies
bill calculations.

Gas is now charged for by the kWh too. 3412 BTU/hr = 1 kW

In relation to what a pipe can deliver in heat. The boiler took energy (gas
or electricity) and turned it to power - or did it? This heat is fed to
radiators. The heat travelling to the rads in the pipes is now energy as
far as the rads or fan convector heaters are concerned.

A powers station takes energy, water, oil, or coal, burns the energy to make
power, which turns the generator which produces energy, which goes down a
cable to your house and turns an electric motor and produces power.


I think that is. It's late.