Re: OT: Anybody got a heat pump

["mark_harrison_uk2" <mph@xxxxxxxxxxxxxxx>]

--- In ukha_d@xxxxxxx, "John Andrews" <groups@j...> wrote:
> Being ignorant - what is a heat pump?


A device that "pumps heat", literally.

As you may recall, heat can only be (net) transferred from a "hot
thing" to a "cold thing".

So, if you stick your baking disk fresh from the oven in a bowl of
cold water, heat will transfer one way, making the disk cooler, and
the water warmer.

As you may also remember, if you compress a fluid, it becomes denser,
and therefore hotter.

A heat pump basically pumps a fluid round in a loop. The loop
typically has two "junctions", one in a place you want to make
hotter,
one in a place you want to make colder.

When the fluid gets into the "one in a place you want to make
colder",
it gets suddenly expanded, so it drops in temperature. Thus, all the
heat transfers from the air around to the suddenly cold fluid. The
fluid carries on being pumped round the loop, having been warmed en
route, until it gets to the "place you want to make warmer", at
which
point it is suddenly compressed, so heats up. Heat then flows OUT of
the fluid into the surrounding areas.

There are two places you use heat pumps:

- Aircon / fridges, where the "place you want to make cooler" is
inside (the house, or the fridge), and the "place you want to make
warmer" is outside. In this case it's used to get over the problem
that, without some heat pumping, you can't transfer heat from the cold
interior to the warm exterior.

- Heaters, where the "place you want to make warmer" is INSIDE
your
house, and the place you want to make cooler is, say, a local lake.
(You need it to be fluid, so that the heat you are sucking out of the
water gets spead across a huge area.)

The reason you use it as a heater is that, while expensive to install,
it is relatively efficient - typically you might get 3 times the
amount of heat pumped in from your lake for a given amount of
electricity as you would simply by using the electricity to power a
heating element. The "free energy" is, obviously, coming at the
expense of cooling down somewhere else.

Hope this helps.

Regards,

Mark