Detailed Explanation of Core Components in Refrigeration Systems: Compressor, Condenser, Evaporator, and Throttling Device

Refrigeration systems typically consist of four core components: the compressor, condenser, throttling device, and evaporator. These components are interconnected via copper tubing to form a closed-loop system filled with a specific quantity of refrigerant. Next, we will delve into the functions and roles of each of these four components.

01. Core Components of the Refrigeration System

Compressor
The compressor serves as the heart of the refrigeration system. Its primary function is to compress the low-pressure refrigerant vapor discharged from the evaporator, elevating its pressure to the level required for condensation at ambient temperatures. Simultaneously, the compressor provides the driving force for the refrigerant's circulation throughout the system. In small-to-medium capacity air conditioning and heat pump systems, common compressor types include piston compressors, rotary vane compressors, scroll compressors, and screw compressors. Scroll compressors are widely adopted in low-temperature air-source heat pumps due to their high efficiency, minimal vibration, low noise, and outstanding reliability.

Piston Compressors

Piston compressors boast a long history and relatively mature technology. However, due to their complex structure and numerous components, they are prone to damage and present challenges in maintenance and repair.

Rotary Compressors

Rotary compressors are renowned for their simple structure and minimal number of components. Their moving parts share the same centerline as the motor shaft, resulting in a compact overall design. Additionally, they feature continuous suction and discharge, minimal clearance volume, and high efficiency. Key structural components include the cylinder, eccentric shaft, rolling piston, discharge valve, discharge port, sliding vane, sliding vane spring, and suction port.

Scroll Compressor

The scroll compressor achieves compact dimensions through the alignment of its moving parts' center with the motor shaft. It eliminates intake and exhaust valves, ensuring stable operation and extended service life. Compared to rotary compressors, efficiency is improved by 5% to 10%. Additionally, it exhibits low sensitivity to liquid slugging, with continuous intake and exhaust processes free from airflow pulsation, ensuring smooth and balanced operation. Due to fewer components, lighter weight, and smaller size, it is 15% lighter and 40% smaller than piston compressors of equivalent specifications.

02. Condenser

As a critical component in refrigeration systems, condensers utilize either air or water as their cooling medium. Accordingly, they are primarily categorized into two types: air-cooled and water-cooled.

Air-Cooled Condenser: Its core component consists of serpentine coils covered with fins and equipped with condenser fans. The coils employ small-diameter copper tubes arranged in staggered rows, while the fins utilize hydrophilic aluminum foil in continuous, integral sheets. Both the fin thickness and inter-fin spacing are meticulously engineered.

Water-Cooled Condenser: This type utilizes water to cool high-pressure gaseous refrigerant, thereby achieving condensation. Common variants include shell-and-tube condensers, jacketed condensers, and welded plate condensers.

03. Evaporator and Throttling Device

Evaporator

Evaporators are categorized into two main types: liquid cooling and air cooling. In air cooling applications, the refrigerant vaporizes inside the tubes while air flows outside the tubes to be cooled. Its structure resembles that of an air-cooled condenser, utilizing copper tubes with diameters ranging from 10 to 18 mm and hydrophilic aluminum fin sheets. The fin spacing design is influenced by the evaporation temperature to optimize airflow and heat transfer efficiency.

Throttling Devices

Throttling devices play a critical role in refrigeration systems, employing various throttling methods including:
- Electronic expansion valve throttling
- Manual expansion valve throttling
- Float-type expansion valve throttling
- Thermostatic expansion valve throttling
- Capillary tube throttling
- Orifice plate throttling
Their primary function is to regulate and control refrigerant flow within the system, ensuring smooth refrigeration operation.

Capillary Tube

The capillary tube, a tube with an extremely small diameter, plays a vital role between the condenser and evaporator. It not only handles throttling and pressure reduction but also effectively controls refrigerant flow. In refrigeration systems, capillary tubes typically use copper tubing with diameters ranging from approximately 0.5 to 2.5 millimeters and lengths from about 0.6 to 6 millimeters to achieve their throttling function. Capillary tubes are renowned for their simple structure, lacking moving parts, which results in an extremely low failure rate and highly reliable operation. However, their adjustment capability is relatively weak, as the liquid supply cannot be automatically or manually adjusted according to changes in operating conditions. Therefore, capillary tubes are most suitable for refrigeration equipment with a small range of evaporation temperature changes and relatively stable loads.

Thermostatic Expansion Valve

Thermostatic expansion valves, also known as temperature-sensitive control valves or automatic expansion valves, serve as throttling mechanisms in Freon refrigeration systems. They detect temperature or pressure signals from the refrigerant exiting the evaporator, automatically regulating the refrigerant flow into the evaporator to ensure stable system operation. Integrating transmitter, regulator, and actuator functions, expansion valves constitute highly efficient automatic control devices.

Electronic Expansion Valve

The core components of an electronic expansion valve include the valve body and coil. It utilizes a thermistor to sense evaporator temperature and outlet temperature, thereby obtaining superheat signals. These signals interact with preset programs and electronic circuits, functioning as comparators and regulators. By adjusting the needle valve position, it precisely controls flow rate. Electronic expansion valves are typically categorized into electromagnetic and electric types.

Electromagnetic Electronic Expansion Valve

The electromagnetic electronic expansion valve, a common type, operates by using electromagnetic force to control valve opening and closing. When current flows through the coil, it generates a magnetic field that attracts the valve body, opening the valve. When the current ceases, the magnetic field dissipates, and the valve body returns to its closed position under spring force. This type of valve offers advantages such as rapid response and high control precision, playing a vital role in refrigeration systems.