The Natural Philosopher wrote:
terry wrote:

It's quite obvious that one heats the areas necessary to the degree
needed and anything more costs more to heat. At any temperature the
heat loss from wind IS a significant factor; not so much because wood
frame houses here are leaky, they are not. If anything are often too
well sealed and must use air/heat exchangers; but because wind carries
away heat from the structure.



It is NOT obvious that 'heating fast' is as boiler efficient as 'keeping
warm'.
It is NOT obvious that 'heating fast' will not in many cases overshoot
the 'needed temperature' by quite a margin. If parts of the structure
take longer to warm up.

This is a case where simplistic analysis fails, because the devils are
in the details.

The other case we discussed here recently and was very hard to pin down,
was 'what is the most fuel efficient way to accelerate a car to its
cruising speed'.

Popular myth has it 'as gently as possible'
simplistic analysis says that since the energy gained is constant, it
doesn't matter whether its a short sharp burst or a prolonged gentle shove.
Detailed analysis implies its about operating the car engine in its most
efficient part of the power band.

Which in the case of a petrol engine is assuredly NOT low throttle
setting at low RPM. Although possibly it is for a Diesel.


Nor yet full revs and wide open ;-)


It also appears to me that the room (well, our lounge) feels warmer when
the radiator is hot (rather than warm). Letting the room cool down, then
heating up relatively fiercely can *feel* warmer than keeping it at a
steady state.

Very difficult to factor in things like that with any degree of accuracy.

Many years ago, Porsche were reported as having done fuel economy tests
in town. Result: Best economy achieved by accelerating fairly briskly to
around 30, then keeping steady speed.

As TNP wrote, nothing is obvious in the real world.

--
Rod

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