Heat pump - what is it and how does it work?

Chiller is a refrigeration machine for cooling liquids, which is widely used in all industries where there is a need to remove excess heat. Despite this, the variability of chiller options is quite wide. They can be equipped with a hydraulic module, a freecooling option, and can have increased efficiency or reduced noise. But today we will look at one of the most popular options for chillers – a heat pump. So what is this equipment and how does it work?

A heat pump is a device for obtaining thermal energy from the environment and using it for heating and water heating. Such pumps successfully heat and provide hot water to entire cities. The popularity of the equipment and the growth in demand for it are associated with the cost-effectiveness of the device: spending 1 kW of electricity, the heat pump produces 3-5 kW of thermal energy and.

The operating principle of a heat pump, like a chiller, is based on heat transfer. If the chiller transfers heat from the consumer to the street, the heat pump, on the contrary, transfers heat from the street to the consumer, thus changing places of the condenser and evaporator.

In order to change the “heating” to “cooling” mode, a 4-way valve is used, switching the direction of freon flow.

The efficiency of a heat pump confuses many people, because if you calculate it, it is fundamentally more than 1 00%. However, such calculations are simply incorrect and do not take into account the energy source other than the electricity consumed. This source is usually air. Electricity in the device is not spent directly on heating, but only on “concentrating” the energy of a low-grade heat source, as a rule, providing energy for the operation of the compressor. That is, the heat pump has two energy sources – electricity and a source of low-grade heat, and the calculations do not take into account the second source, and values greater than one are erroneously obtained.

A more correct coefficient for characterizing the productivity of a heat pump was taken to be the coefficient COP – transformation coefficient (or productivity coefficient) . The higher the number, the more efficient the heat pump is. So, if the technical documentation says that the efficiency is 400%, then this should be interpreted as: COP of this equipment is equal to 4. COP is calculated using the formula:

COP=T2/(T2-T1)

where:
T1—- temperature of the natural source (air)
T2—- temperature of the coolant

The idea of a heat pump was developed back in 1852 by the eminent British physicist Lord Kelvin. However, practical application of the heat pump came about in the 1940s when inventor Robert Weber was experimenting with refrigeration equipment. Weber accidentally touched a hot pipe of the condenser and realized that heat was simply being expelled outside. The inventor pondered how to utilize this heat and decided to place the pipe in a boiler to heat water. As a result, Weber provided his family with a huge amount of hot water. Moreover, part of the heat from the heated water was released into the air. This prompted the scientist to think that one heat source could simultaneously heat water and air, so Weber improved his invention and began to run hot water through a spiral heat exchanger, and with the help of a small fan, distribute heat throughout the house for heating purposes.

Currently, more and more attention is being given to the chiller-heat pump, the so-called four-pipe system with air-cooled condenser. Such a chiller is a device designed for simultaneous cooling and heating of the heat transfer medium. This unit can provide chilled and hot water year-round, as well as supply warm water for sanitary needs. Thanks to this, the facility can operate without additional costs, ensuring significant electricity savings.

The four-pipe chiller-heat pump is well suited to meet the needs of manufacturing plants, medical institutions, logistics companies, museums, vegetable stores, and other facilities where strictly defined temperature conditions need to be maintained in various premises.

The four-pipe chiller-heat pump can be operated in one of three modes:
1. Cooling only;
2. Heating only;
3. Cooling and heating.
It can also automatically adjust the cooling and heating power of water depending on environmental conditions and user settings, and quickly switch from one operating mode to another.

The operating temperature range of modern heat pumps is within the following limits:

• In cooling mode – at outdoor temperatures from 0°C to 45°C they can provide a coolant temperature from 3 °C to 20°C. However, many manufacturers produce models that allow the operation of equipment to produce coolant at sub-zero temperatures down to -10 °C, as well as operation at ambient temperatures down to -15 °C or even lower. In this case, it is necessary to use non-freezing mixtures as a coolant, such as propylene glycol, ethylene glycol, etc.
• In heating mode – at outside temperatures down to -15°C, they provide hot water with temperatures up to 60 °C, however, there are also models that can operate at air temperatures down to -25°C.

To summarize, the chiller heat pump can operate at outdoor temperatures in winter up to -25 °C, in summer up to 48 °C. The water temperature can be up to 60 °C in heating mode and up to 10 °C in cooling mode. However, it must be said that already at an ambient temperature of -15 ° C , an increase in energy consumption and a decrease in the performance of the heat pump begins.

Modern chiller-heat pumps are manufactured with both plate and shell-and-tube heat exchangers. For high-power equipment, screw compressors are used, because the performance of the latter can be smoothly adjusted in the range from 100% to 25%, which ensures more accurate and smooth maintenance of the required temperature. At the same time, for equipment of medium and low power, scroll compressors are used, and to regulate their performance, so-called inverters or frequency converters are used. Also, for both types of compressors, in order to ensure stable operation of the system, at negative ambient temperatures, the technology of vapor-liquid injection (injection) of freon into the compressor is used.

If it is not yet very cold outside, the evaporator produces a sufficient amount of steam. It enters the compressor mainly through the low pressure line, and the injection line is almost not involved. In this mode, the heat pump operates at maximum efficiency, absorbing heat from the outside air. As the outside temperature decreases, the amount of steam in this line decreases and the control system increases the refrigerant flow in the injection circuit, maintaining the required gas flow through the compressor.

Evroprom has a wide range of heat pump chillers, such as SYSTEMAIR SYSAQUA 90 with a power of 91.4/88 kW, PANASONIC ECOI-W AQUA-Z 2C 170CH with 170/187 kW power and hydronic module, or AERMEC NRB 3600 XHA with 969/1002 kW power, hydronic module and increased efficiency function. In addition, we have many used chillers, which you can see on our website!

❗️ Evroprom – your trusted friend in matters of refrigeration equipment. We will choose the best cooling solution for your needs.

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