Why Are Compressors Important in Heat Pumps?

Ever wonder how heat pumps work? And what role do compressors play in heat pumps? – then you have landed at the right place.

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Heat pumps have been a popular source of energy in the European market even before they became known to the rest of the world.

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Thanks to the EU Green Deal, the popularity of heat pumps is at an all-time high in Europe. European Green Deal is a package of ambitious policy initiatives that plans to set the EU on the path to zero net neutrality, indicating the EU’s plans for no-net greenhouse gas emissions by 2050.

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Heat pumps occupy a major share in the European HVAC market, with a total value of whooping USD 14.2 billion as of 2022[1]. The heat pump market is set to grow at a CAGR of 18.4% between 2023 to 2032[2]. This can be attributed to a heat pump’s eco-conscious operation, which will be discussed in the later part of this article.

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Before jumping into the significance of compressors in heat pumps, let's hit on some basic information about heat pumps.

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Q. What are heat pumps?

A heat pump is a device that transfers heat from one place to another. Heat pumps run on electricity and contrary to what their name suggests, they are also widely used for cooling applications.

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Were you aware of the fact that heat pumps do not produce any heat on their own? Although heat pumps require energy to run, they do not have to generate any heat to run at all. It is no wonder heat pumps are emerging as a popular alternative to conventional heating and cooling solutions.

Heat pumps consume significantly less energy than traditional heating systems making them a cost-effective alternative, putting less strain on your pocket.

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Q. How does a heat pump work?

A heat pump absorbs the heat from the outdoor environment, processes it, and then transfers it indoors. Four processes are essential to a heat pump’s operation: evaporation, compression, condensation and decompression. The following processes are performed by an evaporator, condenser, compressor and expansion valve respectively.

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In an AWHP (air-to-water heat pump), the heat is first absorbed by the liquid refrigerant from the heat source (air, water, or ground) and evaporated by the evaporator to a low-temperature, low-pressure gaseous state. Then the refrigerant gas passes through a compressor, which compresses it to a high-temperature, high-pressure refrigerant gas.

Subsequently, the hot refrigerant gas is transferred to a condenser, a high-temperature heat exchanger where the high-temperature refrigerant gas is condensed to a high-temperature liquid and dispatches the heat for water heating or room heating. As the final step in the heat pump cycle, the refrigerant is decompressed back into a low-temperature, low-pressure refrigerant liquid by an expansion valve.

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This is how a heat pump works for heating applications. However, a heat pump is not only capable of heating but equally efficient at cooling. For cooling the process is just reversed; the heat is absorbed from indoors and transferred outdoors, discarding the heat from the living space and cooling the room temperature.

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Q. What compressors are commonly used in heat pumps?

A compressor is unarguably the most important part of a heat pump. Since compressors generally have a great impact on a heat pump’s performance, it is important to select a compressor that matches your system’s requirements.

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A compressor single-handedly determines a heat pump’s heating or cooling capacity, noise and vibration problems. It is important to consider all these aspects before selecting a compressor for any heat pump.

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Scroll and rotary compressors are by far the most popular choice for heat pumps. Scroll compressors usually have 50% less load than rotary compressors curtailing noise and vibration issues; lesser vibration means more capacity for a scroll compressor.

However, in a rotary compressor, the number of parts is fewer and the working mechanism is simpler compared to scroll compressors. For this very reason, rotary compressors are more competitively priced than scroll compressors.

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Q. How to improve the efficiency of an air-to-water heat pump?

As we learned above, a heat pump’s quality is synonymous with a compressor’s performance.

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A high-quality compressor can increase the efficiency of a heat pump whereas, a poor-quality compressor can do the opposite. Especially, in winter when the temperature is low, a heat pump's efficiency can hit an all-time low. Low temperature means low evaporation temperature and low circulation in the cycle reducing the system’s performance. Therefore, it is necessary to select a compressor and design a cycle that can produce a sufficient heating performance at a low outdoor temperature.

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In order to enhance heating performance at low temperatures, you can either increase discharge pressure or increase the circulation flow rate in the cycle. In order to increase the heating capacity, a compressor with a high compression ratio must be used as a method of increasing the discharge pressure. This will enhance the heating capacity of a heat pump,

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Closing remarks

Heat pumps have become a hot commodity in the European market and are catching up in the global market too. Heat pump manufacturers are actively eyeing the heat pump market in Europe, looking for ways to give their heat pumps a competitive edge. At LG Compressor & Motor, we believe that a carefully designed compressor is the answer to that.