Cooling & Heating 制冷和加热


Air conditioning (often referred to as AC, A/C, or air con) is the process of removing heat and moisture from the interior of an occupied space to improve the comfort of occupants. Air conditioning can be used in both domestic and commercial environments. This process is most commonly used to achieve a more comfortable interior environment, typically for humans and other animals; however, air conditioning is also used to cool and dehumidify rooms filled with heat-producing electronic devices, such as computer servers, power amplifiers, and to display and store some delicate products, such as artwork.

A simple stylized diagram of the refrigeration cycle:

  • 1) condensing coil
  • 2) expansion valve
  • 3) evaporator coil
  • 4) compressor

refrigeration cycle

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There are eight main components that play a pivotal role in cooling your home: A Thermostat, Condenser, Compressor, Fan, Metering Device, Evaporator, Blower and a Filter.

The first step begins with setting your thermostat to the desired temperature. This triggers the condenser fan and compressor to turn on. The compressor begins pumping a fluid called a ‘refrigerant’ throughout the system. This is used because of its low boiling point. Refrigerant constantly changes from a vapor to a liquid in order to move heat from inside your home to the outdoors. It enters the compressor as a low-temperature, low-pressure vapor. After it’s compressed, it leaves as a high-temperature, high-pressure vapor. It then travels through the condenser coil, where the vapor condenses into a liquid. The heat it has collected indoors and after compression, is released outside.

The fan inside the unit helps with this process. The refrigerant leaves the condenser as a medium-temperature, high-pressure liquid. Then, flows to the metering device. In this case, a thermal expansion valve is used. A pin inside the valve adjusts the flow rate of refrigerant depending on the temperature at the evaporator end, using a ‘sensing bulb’. As it flows through the valve, its pressure drops significantly, releasing a low-temperature, low-pressure liquid/vapor mix. The lower pressure allows room temperature air to boil the refrigerant. The chilled refrigerant then flows through the evaporator coil.

The blower begins circulating air throughout the house. Room-temperature air is pulled in through the return duct and passes through the filter to remove particulates. The heat from the air is absorbed into the refrigerant inside the evaporator coil, dispersing chilled air through the supply duct. As the air passes over the coil, the refrigerant is boiled and evaporates back into vapor form. During this process, condensation forms on the outside of the coil and exits through a condensate drain line. The refrigerant returns to the condenser to disperse the collected heat outdoors, and the cycle starts again. Your home is slowly cooled, and the thermostat shuts off the equipment once it senses the desired temperature.