Can anyone explain how a heat pump works and give the names of all the componants?

Question

Im doing revision for the next academic year and have lost this particular worksheet.

A heat pump is on the back of a fridge and it is what keeps the fridge cold.

Answer 1

To understand a heat pump -- first developed by Lord Kelvin (1824-1907) -- it's good to first remember how a refrigerator works.

A refrigerator doesn't actually ''make coldness," and in fact a working refrigerator, overall, acts as a heater, even if the door is open.

In a refrigerator you take some liquid that evaporates easily (usually a gas compressed into liquid form) and let it evaporate next to the thing that you want to have cooled. Evaporating means that molecules of the liquid take heat from the thing to be cooled in order to boil away and escape. So far this is just like the cooling from sweating, or the cool feeling of alcohol evaporating from your skin.

A refrigerator catches the gas and compresses it back into a liquid. This compression produces heat which is carried away by the coils on the back of the refrigerator, and that is why they are warm. The liquid is carried to the place to be cooled and the cycle repeats.

Now imagine a refrigerator with the door off and the cold side facing indoors, and the hot side outdoors. This is a simple heat pump which will cool your house in the summer.

If you set it up to also run in reverse, and cool the outside by evaporating liquid on that side and releasing the heat on the inside, you have a device which will also be a heater. This is the heat pump running the other way.

In winter, because a heat pump basically takes some heat out of the cold air outside (refrigerating the great outdoors), you can get more heating than you would if you just took the same amount of electricity to run a radiant heater, so these things are good to help minimize energy use!

Parts well......

Heat pumps all have the same basic components. These components consist of a pump, a condenser, an evaporator, and an expansion valve. Despite the relative similarities of these components, heat pump designs vary greatly depending on the specific application of the pump. The two major designs, vapor compression and absorption, utilize different thermodynamic principles, yet both include similar components and provide similar system efficiencies.

Answer 2

A heat pump is essentially a heat engine in reverse. Working in a reversed Carnot cycle it uses an energy input to move or pump heat from a cold source (e.g. the inside of a refrigerator) to a hot sink (the radiator on the back of a refrigerator).

A vapour compression heat pump uses a compressor to raise the pressure and temperature of a refrigerant vapour (compression phase). It then condenses the vapour to a liquid in the hot sink heat exchanger exchanger (cooling phase), drops its pressure and temperature by expanding it through a restrictor or an expansion valve (expansion phase), finally evaporating the cold liquid to a gas in the cold source heat exchanger (heating phase) which in the case of a refrigerator is the cold space inside.