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Introduction to Heat Pumps

Win

C10.

Outside Cold Air

The primary difference between a

and a

is that the objective is not to remove heat from the cold reservoir. The objective of a

is to deliver heat to the hot reservoir: QH.

The range of operating temperatures for a household

is very similar to the temperature range for a household refrigerator.

The hot reservoir (the air in your home) is typically at about 25°C and the cold reservoir (the outdoor air on a winter day) might be at -5°C.

It is not surprising that many of the same

are used for

and refrigerators, including

also operate on the same cycle as the

Lesson 10D: page 1 of 6

A heat pump is a vapor compression cycle whose purpose is to transfer heat into the hot reservoir.
Other than the purpose, this cycle is virtually identical to the vapor compression refrigeration cycle.
The reservoir temperatures in a home refrigerator are very similar to the reservoir temperatures in a home heat pump system.
In fact, in the United States, many home refrigerators and home heat pump systems even use the same refrigerant, R-134a.
Heat pumps are a relatively efficient way to heat a home as long as the outdoor temperature does not drop too low.
In colder climates, heat pumps are usually backed up by a traditional gas or electric heating system that takes over when the temperature falls to low.
There is one interesting thing that heat pump systems are designed to do that refrigeration systems are not.
If you own a heat pump, then you already know what I’m talking about.