Heat pump is a refrigerator?

The principal difference between a heat pump and a refrigerator is a matter of perspective. A heat pump is simply a refrigerator where the inside of the refrigerator is outside the house. In other words, a heat pump attempts to cool down the air outside the building, and in the process heats up the air inside the building.

Put differently, a refrigerator is simply a heat pump which takes heat from inside the refrigerator and transfers it outside the refrigerator.

Before answering the question let's talk about the word "efficiency".

In the meaning we care about here the word is used to described the effectiveness with which some consumed resource is converted into some desired effect. In the context of thermodynmanic engines, refrigerators and heat pumps the desired outcome and the available resource are one of

• heat moved between the warm source and the mechanism
• heat moved between the cold source and the mechanism
• work (done by or on the mechanism)

all three of which are denominated in terms of energy, so we use a ratio $$ \text{efficiency} = \frac{\text{desired outcome (in energy)}}{\text{resource used(in energy)}} \;.$$

In an engine we feed energy in (heat from the hot reservoir to the engine, and get work out, so $$ \text{efficiency}_\text{engine} = \frac{\text{work done}}{\text{heat supplied}} \;.$$

In the case of a either refrigerator or a heat pump supplied work is the resource used up, but the desired outcome varies: for refrigeration you care about heat removed from the cold source, while in a heat pump you care about the heat added to the hot source. (For historical reasons we also use the phrase "coefficient of performance" instead of "efficiency", here.) \begin{align*} \text{CoP}_\text{refrigerator} &= \frac{\text{heat removed}}{\text{work supplied}} \\ \\ \text{CoP}_\text{heat pump} &= \frac{\text{heat supplied}}{\text{work supplied}} \;. \end{align*}

So, to finally put the answer in words, the only difference is what you are trying to accomplish.

I think that part of your confusion stems from the fact that the statement you highlighted is rather poorly phrased. A couple of fact that might clarify things:

1.) a heat pump is a fancy science word for any refrigeration device or unit, be it a kitchen refrigerator, air conditioner, "swamp box" or anything else. I'm not sure why the author of the quote is drawing some kind of difference between a refrigerator and a heat pump. (Somebody correct me if I'm wrong on this point).

2.) Somewhere in your quote, the author seems confused about how "heat pumps" are normally configured. Every "heat pump" I've ever seen in the real world was used to cool off a room or the inside of a freezer, etc.

3.) Lastly, every device whose authentic purpose was to heat a room was called a heater. (My sarcasm is aimed at the author of the quote, not you SEQUENCE). Granted, a traditional food refrigerator may incidentally heat a room up by cooling off the inside of the "cabin", but this is incidental, and should be presented as such.

I agree that the author couldn't be less clear. The author seems to need to re-write this section of the book.