Influencing factors of air conditioning

In the freezing cycle, the heat pump transfers heat from one low-temperature heat source to another high-temperature heat sink, and the heat naturally flows in the opposite direction. This is the most common way of air conditioning. The operation principle of the refrigerator is quite similar, transferring heat from the inside of the refrigerator to the air outside the refrigerator.

This cycle uses the universal gas law) PV = nRT, where P stands for air pressure, V stands for volume, R stands for universal gas constant, T stands for temperature, and N is the number of moles of gas (1 mol = 6.022× 1023 particles).

The most common refrigeration cycle uses a motor-driven compressor. In an automobile, the compressor is driven by the crankshaft of the engine through a pulley, and both of them use electric motors for air circulation. Because heat will evaporate when it is absorbed and condense when it is released, the air conditioner uses a compressor to change the pressure in two sections and a pump to make the refrigerant flow. The refrigerant will be pumped into the cooling chamber (evaporation coil), and the low pressure and low temperature will evaporate the refrigerant into steam to absorb heat. In the other section (condenser), the vapor of the refrigerant is compressed and passes through another heat exchange coil, which condenses into liquid and releases the heat previously absorbed in the cold section. Refrigeration air conditioning equipment usually reduces the humidity of the air being treated. The relatively cold (below dew point) evaporation coil will condense the water vapor in the air to be treated, just like cold drinks will condense the water vapor in the air outside the container, so the water will flow away through the sewage pipe, which will take away the water vapor in the freezing space and reduce the relative humidity. Because the human body naturally lowers its body temperature by evaporating sweat, drier air will improve the comfort of the human body. Comfortable air conditioning systems are usually designed to exhaust air with a relative humidity of 40% to 60%. In the property of food retailers, large open freezers can be used as effective air dehumidification equipment.

Some air-conditioning equipment only dries the air without lowering the temperature of the air, and its operation mode is similar to that of ordinary air-conditioning equipment, except that a heat exchanger and a convection fan are added between the air inlet and the air outlet, which can reach the comfort level similar to that of air-conditioning in tropical humid climate, but only consumes about 1/3 of electric energy. This kind of air conditioner is also suitable for some people who are not used to colder air. Freon (chlorofluoromethane) is the trademark name of a series of chlorofluorocarbon chemicals produced by DuPont Chemical Company and other companies. These refrigerants are widely used because of their high stability and safety. However, there is evidence that these chlorine-containing refrigerants will rise to the upper atmosphere when they are released into the atmosphere, and their chemical functions are still unclear. However, it is believed that CFC is decomposed by ultraviolet radiation in the stratosphere and chlorine particles are released. Chlorine particles become the catalyst of ozone decomposition, which seriously destroys the ozone layer that protects the earth from ultraviolet radiation. Chlorine will continue to act as a catalyst until it is stable with other particles. Rare CFC refrigerants whose production has been banned include R- 1 1 and R- 12. HCFC (R-22, commonly used in households) and HFC (R- 134a, used in automobiles) have been gradually banned, which have completely replaced CFC. According to the Montreal Protocol, HCFCs have been phased out and replaced by hydrofluorocarbons (HFCs), such as R-4 10a and R404, which contain no chloride.

In addition to using chemical refrigerants or chemical mixed refrigerants, natural refrigerants (refrigerants) ammonia gas are traditionally used to make ice cubes, but due to the influence of the physical characteristics of ammonia gas (such as flammability, toxicity, odor and corrosiveness), it is not suitable for the traditional home air conditioning environment. It is mostly used for fishing boats or industrial ice making. Another developing natural refrigerant (refrigerant) is carbon dioxide. Because of its supercritical compression characteristics, it has excellent advantages in hot water heat pump. The power of air conditioning equipment is usually expressed by a technical term "cold ton" in the United States. A definition of "cold ton" is that it takes 24 hours to cool a "short ton" (equal to 2000 pounds or 907 kilograms) of ice to dissolve the required refrigeration power. Equal to 12000 British thermal units/hour or 35 10 watt. The central air conditioning system of residential buildings (detached villa buildings) usually has a capacity of 1 to 5 cold tons.

In the car, the air conditioner needs to consume about 5 horsepower (4 kilowatts) in the conversion of AC and DC systems. Some buildings use gas boilers to generate electricity. The hot waste gas produced by the boiler can be used to drive a device called absorption refrigeration unit to make cold water. The prepared cold water can be used to cool the air through the terminal cooling equipment to achieve the purpose of air conditioning. This dual-purpose technology of power generation and refrigeration is very attractive, especially in areas where fuel prices are suitable and there are various use needs. This system that generates heat, electricity and cold at the same time is called "triple supply" system.