Heat Pump Operating Principle

In our this essay we are going to deal with the operating principle of heat pumps. To set up a heat pump for your house, workplace or vacation home  can provide a great relief from your energy bill by reducing the cost of heating and cooling. The heat pumps which  are new tecnology will replace with air conditioning and central heating systems in the future.

Heat pumps costs can change between 4000 $ and 20000 $ according to  size of your house,workplace or the heat pumps which you choosed.In general, geothermal heat pumps need to setup to underground so their setup costs will be more expensive than air source  heat pump setup costs. The cost of the heat pump and the labor can thought as expense outgoings but your energy consumption can be significantly reduced after setup. The content of this article is like this.


What’s in this article?

  1. What is the heat pump?
  2. How does the heat pump work?
  3. Heat pump types
  4. Cooling cycle
  5. Steam compression heat pump cycle
  6. Compressor
  7. Heat pump setup cost
  8. Heat pump comments
  9. Heat pump application areas
  10. Heat pump applications

We hope that this article is the most comprehensive article about heat pumps. Over time, we can add new sections to your writing and make corrections. Now let’s start with our first question.

1. What is Heat Pump ?

In 1824 Nicolas Léonard Sadi Carnot introduced the basic principle of the heat pump cycle, which is actually a cooling cycle. 26 years later in 1850 Lord Kelvin suggests that cooling devices can be used with heating purposes and people starts to apply heating systeam. Before the Second World War, many engineers and scientists worked on the field to develop and use the heat pump. During the war years, In the war years, the work was resumed after the war, as the industry was shifting its opportunities to more urgent problems.

The   confidence has decreased in the heat pump. Because  the potential of the heat pump industry, the high cost of setup,the cheapness of energy based on natural gas and oil in the 1960s. Heat pumps gained importance after the energy crisis of 1973, and many studies have been done since that date. The heat pumps are systems that make low-temperature heat available from nature. The operating logic of heat pumps is the same as the refrigerators we use in our homes. Heat pumps can be used alone or in combination with an additional system. The low-temperature heat from natural sources such as air, water, and soil is converted into vapor by the refrigerant fluid. Then, the steam sent to the compressor is compressed and the high temperature is obtained and transmitted to the dispersion system. The heat pump used with winter heating purpose can be used for summer cooling. Heat pumps save money between 50% and 75% compared to fossil fuels.

2. Working Principle of Heat Pump

In this section, we want to give some information about the principle of heat pump operation.
A heat pump is a machine that delivers heat from a low temperature environment with energy from the outside to a high temperature environment. The heat pump used with heating purpose in winter can be used for cooling in summer.

The most important characteristic of a heat pump is the performance coefficient (COP). The COP values of an efficient system are normally equal to 4. Each unit entered into the system generates 4 units of energy. COP values in Japan are above 5. The best heat pumps reach COP value of 6.8.
Cooling machines and heat pumps perform the same cycle but have different uses.The purpose of cooling machines are  pulling heat from the low temperature environment and keeping it below the ambient temperature. It is a mandatory operation to heat conduction to the environment or a high temperature averaging but it ‘s not an aim. The purpose of the heat pump is to keep an environment warm. To fulfill this function the  heat from a low-temperature thermal energy storage is given to the place where wanted to heat. The low-temperature thermal energy store is usually a cold ambient air, well water or soil, and the place to be heated is inside a house.

In heat pump systems, the heat sources of the evaporators are called “heat sources”. The availability of these sources, which are very important for the heat pump, depends on the following conditions:

  • The welding temperature does not change much,
  • As the welding temperature is as large as possible,
  • The source can be found abundantly and affected as little as possible from the geographical conditions,
  • If the source is not dirty,
  • No corrosion

The technical and economic performance of a heat pump depends on the characteristics of the heat source. The ideal heat source for the heat pumps used in buildings must have high temperature and high temperature throughout the heating period, abundant availability, abrasive and non-contaminating factors, suitable thermophysical properties, low investment and operating cost. In most cases the availability of heat source is the most important factor. As a source in heat pumps are

  • Ambient air
  • Soil
  • Sea, river, lake water
  • Underground waters
  • Waste liquids
  • Residual gases
  • Sun
  • Stone

They all have different characteristics.

Ambient air: It is found in abundance and is the most used heat source for heat pumps.
The seasonal performance factor (SPF) of air-source heat pumps is 10-30% lower than that of soil-based heat pumps. The reason for this are high temperature difference in the evaporator due to decrease in outside air temperature,  in this case the evaporation  can freeze so rapid reduction of energy, capacity and performance required for fan operation.

Soil: It is a good source, but it is necessary to use good materials to bury the heat exchanger in the soil and to prevent corrosion. This increases the initial investment cost.

Sea, river, lake waters: They are a good source of heat pumps. River and lake waters are freezing in winter. This problem is not very important for the sea. There is pollution problem in this water. They are also quickly affected by geographical conditions.

Underground waters: The temperature change during the year is low. If the pump is being used for transport, it means that additional energy is being used. It’s dangerous to mix dirty water into it. Burying heat exchangers underground can cause corrosion and increase cost.

Residual gases: Important heat source for heat pumps in domestic and commercial buildings. The heat pump uses heat from the ventilation to heat the volume and water.

Sun: It’s a good resource. The initial investment cost is very high, but the maintenance cost is low and clean. Heat pumps can also be used alone or in combination with an additional system. It is called “monovalent heat pumps” which solves the heating requirement by itself and the heat pumps which solve the heating need with additional welding are called “bivalent heat pumps”. Bivalent Heat pumps resolve 50-95% of the need for heating. Examples of alent systems include solar collectors and boilers. The operation of these binary systems is either sequential or concurrent. Sequential operation is when a system is deactivated and the other is switched on. The heat pump boiler system can be operated in this way. When the heat pump is not economically feasible, the heat pump is deactivated and the boiler is switched on. An example of working together is the heat pump – solar collectors system. The temperature range required for the operation of the heat pump used to heat the building can be provided by solar energy.

3. Types of Heat Pumps


We can consider the heat pump as a reverse cycle of simply a heat machine. The heat machine is a machine that transfers heat from the high temperature environment to the low temperature environment and performs the outgoing operation. The heat pump is a high-temperature averaging machine that receives heat from an external heat source and low-temperature heat source. heat pump used with heating purpose in winter, can be used for cooling in summer. The transfer of heat from the cold heat source to the hot heat source can be accomplished in various ways. Accordingly, the heat pump types are as follows:
Generally, “Vapor Compressed Cycle” and “Absorption” heat pumps are used.

In general meaning , when considering heatpump operating principle, the vast majority of heat pumps operate according to the steam compression cycle principle. The basic components of a simple heat pump are the compressor, the expansion valve, the evaporator and the two heat exchangers called the condenser. Saturated steam coming from the evaporator is compressed into isentropically higher pressure and temperature in the compressor and turned into hot steam (1 – 2 ‘state) The superheated steam entering the condenser condenses at constant pressure, releasing the available heat. (2 ‘- 3 state) The pressure of the high pressure fluid in the saturated liquid state and the temperature are brought to the evaporator conditions in the expansion valve. (3 – 4 state).The heat is transferred from the heat source to the fluid at constant pressure and the fluid evaporates. (4 – 1 state). After this, the cycle starts again and continues this way.

Hybrid heat pump: A hybrid heat pump is a combination of a mechanical and an absorbing heat pump. The working principle is based on the fact that the absorption of ammonia in water takes place at much higher temperatures than that of ammonia condensation at constant pressure.

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