What Are The Four Major Components Of An Air Source Heat Pump? What Are They All For?

The air source heat pump is mainly composed of four components: compressor, expansion valve, finned heat exchanger, and sleeve heat exchanger. It drives the compressor and motor to work through the input of electrical energy, allowing the finned heat exchanger to absorb heat. The process of heat release by the sleeve heat exchanger has a heating effect of up to 380%, making it one of the most energy-saving heat source equipment at present. During use, safety, environmental protection, and efficiency are its main characteristics.

Cardiac components - compressors

As the heart component of an air source heat pump, a compressor is equivalent to the CPU of a computer and the heart of the human body. Through it, it can drive the circulation of refrigerant, achieve the process of heat expansion and contraction, and enable the refrigerant to achieve physical changes such as evaporation, heat absorption, and condensation.

Throttling devices - capillary tubes, electronic expansion valves, and thermal expansion valves

Throttling valves can usually be divided into capillary throttling, thermal expansion valve throttling (internal balance, external balance), and electronic expansion valve throttling. By changing the pressure change of the refrigerant, the refrigerant realizes the process of liquefaction and gasification, and detects and collects multiple parameters such as superheat or temperature difference between inlet and outlet air, return air temperature and its set value. After being processed by a microprocessor, the opening of the expansion valve is controlled, To meet the requirements of system load. The advantage of electronic expansion valves is that they can accurately control the refrigerant flow rate, thereby achieving precise control of evaporation temperature. Usually used in places with high requirements for temperature control accuracy.

The electronic expansion valve can operate normally above -70 ℃, but the thermal expansion valve can only reach a minimum of -60 ℃. Capillary tubes are used in small refrigeration systems (with a simple structure and cannot be adjusted, after all, the capillary tube is just a small copper tube);

Expansion valves are used in large and medium-sized refrigeration systems (with relatively complex and adjustable structures) to regulate refrigerant flow. In addition to controlling the evaporator, they can also be used to regulate the condenser. When the evaporation condition allows, if the condensation pressure is too high, the expansion valve can be closed appropriately to reduce the flow of refrigerant in the system, reduce the load on the condenser, and thereby reduce the condensation pressure, achieving efficient and reliable operation of the air energy water heater unit.

Heat release component - tube sleeve heat exchanger

A sleeve heat exchanger is a carrier that transfers part of the heat of the hot fluid to the water supply. It uses high-efficiency threaded copper pipes and is wrapped with treated galvanized steel pipes to achieve the process of refrigerant wrapping, allowing the high-temperature refrigerant gas to fully contact the water and achieve better heat transfer effect.

Advantages of sleeve heat exchangers

The structure is simple, and the heat transfer area can increase or decrease freely. Because it is composed of standard components, there is no need for additional processing during installation.

High heat transfer efficiency. It is a pure countercurrent heat exchanger, and suitable cross-sectional dimensions can be selected to improve fluid velocity and increase the heat transfer coefficient of the fluid on both sides. Therefore, its heat transfer effect is good. When conducting liquid-liquid heat transfer, the heat transfer coefficient is between 870 and 1750W/(m2 • ℃). This is particularly suitable for heat transfer of fluids with high pressure, low flow rate, and low heat transfer coefficient. The disadvantage of a tubular heat exchanger is its large footprint; The metal consumption per unit heat transfer area is high, about 5 times that of shell and tube heat exchangers; Multiple pipe joints are prone to leakage; High flow resistance.

The structure is simple, the work adaptability is large, and the heat transfer area is easy to increase or decrease. Both sides of the fluid can increase the flow rate, so that both sides of the heat transfer surface can have a high heat transfer coefficient. The disadvantage is that the metal consumption per unit heat transfer surface is large. In order to increase the heat transfer area and improve the heat transfer effect, various forms of fins can be added to the outer wall of the inner tube, and a scraping film disturbance device can be added to the inner tube to adapt to the heat transfer of high viscosity fluids.

Disadvantages of sleeve heat exchangers

Overhaul, cleaning, and disassembly are all quite troublesome, and can easily cause leakage at detachable connections.

In production, there are many material choices that are limited. Due to the fact that welding is not allowed in the inner tube of sleeve type heat exchangers, as welding can cause thermal expansion and cracking. However, most sleeve type heat exchangers are chosen to save space, bent, and coiled in a serpentine shape, so there are many special corrosion-resistant materials that cannot be produced normally.

There is no unified welding standard for sleeve heat exchangers in China, and various enterprises choose welding methods based on the experience of other heat exchange products. Therefore, various problems are common at the welding joints of sleeve heat exchangers, and regular inspection and maintenance are necessary.

Air absorption components - finned heat exchangers

The finned heat exchanger mainly uses aluminum foil with clean water film and a bridge mounted ventilation system, which allows the air to fully contact the heat transfer area and more efficiently absorb the heat in the air.

Characteristics of finned heat exchangers

High heat transfer efficiency, due to the disturbance of the fluid by the fins, the boundary layer continuously ruptures, resulting in a large heat transfer coefficient; Meanwhile, due to the thin partition and fins, which have high thermal conductivity, the plate fin heat exchanger can achieve high efficiency.

Compact, due to the extended secondary surface of the plate fin heat exchanger, its surface area can reach 1000 ㎡/m³.

Lightweight, due to its compact and mostly aluminum alloy manufacturing, steel, copper, composite materials, etc. have also been mass-produced.

The arrangement and combination of flow channels can adapt to different heat transfer conditions such as countercurrent, cross flow tide, multi stream flow, and multi pass flow. The combination of series, parallel, and series parallel between units can meet the heat exchange needs of large equipment. In industry, it can be standardized and mass-produced to reduce costs, and interchangeability can be expanded through modular combinations.