Domestic and semi-industrial air conditioners are of two types, depending on the design and principle of operation: monoblock and split systems. Monoblocks, in turn, are divided into mobile, window and evaporative devices, and split systems are divided into wall, cassette, duct, column and floor-to-ceiling (universal) ones.
The basis of the principles of operation of various climate systems
Split systems and mobile as well as window air conditioners have a different operating principle, but are based on the property of any liquids to take heat during evaporation and to release it during condensation. In these cooling devices, the working fluid is freon gas. It circulates in a closed circuit in two-component blocks and monoblocks.
The temperature of the phase transition, when the gas becomes liquid, and then again returns to its normal state, depends on the working pressure — the higher it is, the higher the temperature of the phase transition.
In order for the liquid freon to boil and take heat from the air, the compressor creates a pressure in the evaporator at which the phase transition temperature is lower than the ambient temperature. When the compressor creates a pressure at which the phase transition temperature is higher than the air indicators, the freon again takes on a gaseous state and transfers the collected heat to the outside, that is, to the street, through the external unit.
If we consider the principle of operation of a floor air conditioner without an air duct, then the same property of the liquid is used here, but the working substance is water, not freon. There is no closed loop inside the device. The liquid is pumped up by the drainage pump and evaporates under the influence of warm air, giving a cool out. In fact, it is more of an evaporator than an air conditioner, since it moistens the air well and cools it mediocre.
How split systems and their varieties work
The split system consists of outdoor and indoor units. In the outside is a compressor, control board, fan and condenser. The main elements of the indoor unit: evaporator, fan, filters, temperature sensors and condensate pan.
Freon circulates in a closed circuit. It consists of:
- internal coil - evaporative heat exchanger;
- external coil - condenser heat exchanger;
- connecting copper tubes - freon highway;
- pressure boosting compressor;
- capillary tube in household systems;
- thermostatic valve (TRV) for semi-industrial units.
Capillary tube and expansion valve have a common synonym - throttling device. They provide the difference between the condensing pressure and the boiling point of the refrigerant due to the hydraulic resistance along the entire length.
Air conditioners that can carry out air heating have a 4-way valve that interchanges functionally two heat exchangers in some places - the external one is responsible for the evaporation of the refrigerant, and the internal one is responsible for its condensation.
Cooling work
Freon enters the compressor, where its pressure increases 3 times, and the temperature rises by 50-60 ° C, that is, compression occurs. Then it goes into the condenser and is blown with colder air, after which it goes into a liquid state. Air passes through a condenser heat exchanger and is heated by the heat released by freon.
Then the refrigerant moves into a spiral-shaped capillary tube or expansion valve, where its pressure decreases, the temperature decreases and a slight evaporation occurs.The evaporative heat exchanger is purged with room air, but is cooled when a cooler freon enters. In this case, the refrigerant takes its heat and returns to its original state. Next, the cycle repeats.
When working in the cold, the air conditioning system of the split system consists of 4 main stages: compression, condensation, rarefaction and evaporation.
Heating work
The essence of the principle of operation of an air conditioner of a split system for heating does not change. When the 4-way valve switches the functions of the units, when the direction of flow of the refrigerant changes, air is taken from the street by the outdoor unit, where freon evaporates, and the indoor unit delivers it into the room, in which the refrigerant again goes into the gaseous phase.
The lower the outside air temperature, the more difficult it is to extract heat from it, since the difference between the air temperature and the freon evaporation temperature decreases, therefore, the heating ability decreases due to the equalization of their values.
Precision Air Conditioners
Precision climatic technology by the principle of operation does not differ from a split system, but has a number of features:
- Able to work 24/7/365 for 10 years, while a household split-system will last no more than 2 years.
- It has a powerful fan, due to which the cooling quality is higher than that of split. Air flows of a given temperature are evenly distributed throughout the room.
- Freon, water or glycol can act as a working substance.
- Humidification is carried out using an electrode-type steam generator.
Precision air conditioners are used in server rooms, where it is necessary to uninterruptedly maintain a certain temperature and humidity.
Inverter air conditioners
The principle of operation of the inverter air conditioner is the same as that of a conventional one. The difference between the inverter-type climatic equipment is the management of the operating mode. In a conventional split system, when the set temperature is reached, the compressor turns off. When the temperature changes up, the supercharger starts to fire. Thus, the system operates at full power, but intermittently.
In inverter motors have a frequency converter board, which changes the standard frequency of the electrical network. The fan does not stop working when the temperature norm is reached: it gradually slows down the rotation, and when the air is heated by 1 degree, it increases the number of revolutions per unit time.
The advantages of such control are in the durability of the equipment and in saving electricity up to 30% compared to non-inverter split systems.
Canal climate system
A system of inlet and outlet ducts departs from the indoor unit of the channel air conditioner, through which warm air is taken in and cold is supplied to one or more rooms.
Equipment of this type has the function of mixing fresh air from the street up to 30%.
Installation of a duct type air conditioner is best done at the stage of building construction - the unit is installed under the ceiling together with a ventilation system.
The principle of operation of mobile air conditioners
Cooling
With the first stream, the condenser is cooled due to the passage of already cooled air. The warm stream is vented out through the corrugated discharge hose. A second stream of air is needed to cool the room. Passing through the evaporator, warm air gives off heat to freon and lowers its temperature, after which it returns to the room through distribution grids on the housing. The compressor creates the necessary pressure, and a centrifugal fan provides air intake and blowing heat exchangers. So the principle of mobile air conditioning for cooling is built.
If we talk about the principle of operation of a mobile air conditioner with an air duct, the difference is that in the case there are two sealed compartments with two different coils. In the lower is a condenser heat exchanger, and in the upper is an evaporative heat exchanger.
Heating
When heated, the monoblock usually works in the fan heater mode, and the duct is closed with a plug on the outside so that cold air from the street does not get into the device. The conditioner isolated from external environment can function at any frosts.
The principle of operation of the air conditioner for heating in this case is based not on redirecting the refrigerant to the other side, but on electric heating due to ceramic heating elements, which turn the mobile device into a typical heater.
Window air conditioning cooling and heating
The operation of a window unit is practically no different from the principle of operation of an outdoor air conditioner. It also has two compartments: in one there is an evaporative heat exchanger, and in the outgoing one there is a condenser one.
Cooling
When cooled, freon circulates between two coils. A centrifugal fan draws air from the room, passing it through a coarse filter, and blows it through the evaporative heat exchanger. Due to the temperature difference and the injected pressure, the air gives off heat to freon and cools, heading back to the room. The refrigerant at this time moves to the heat exchanger on the outside of the window unit, where heat is transferred to the air pumped by the axial fan through the side grilles.
Heating
If we talk about the principle of operation of a window-type air conditioner for heating, then built-in heating elements are also used here, which make it possible to turn the cooling device into a full-fledged heater. Up to -15 ° C such a candy bar will warm the room air properly.
How evaporative air conditioners work
In evaporative air conditioners there are no freon circuits with heat exchangers and compressors. The structure of the airless floor unit includes the following elements:
- fan;
- drainage pump;
- porous hydro-filter;
- coarse air filter;
- capacity for cold water.
The working fluid is cold water, in which ice is additionally placed for more efficient cooling.
Cooling
There is no need to remove moisture, since it is released into the room along with chilled air, therefore such monoblock devices are also called humidifiers or evaporative air conditioners.
The cooling cycle consists of several stages:
- the hydro-filter is impregnated with water coming from a special container under the influence of a drainage pump;
- air flow passes through a mechanical filter and enters the hydro-filter;
- here he gives his heat to water, and it begins to evaporate, while cooling and humidification of the air flow occur.
The operation of the air conditioner without an air duct consists in the fact that water passes from a liquid state to a gaseous one and absorbs heat from air.
Heating
If we consider the principle of operation of the air conditioner-evaporator for heating, then it is no different from window units and mobile ones with an air duct. A heating element is built into the body of the floor evaporator unit, which allows the device to be operated in the mode of an electric fan heater. There are no restrictions on the outside temperature.
The principle of operation of all air conditioners: floor, window and split systems, is based on the ability of the liquid to collect and give off heat during evaporation and condensation, but the cooling or heating cycle can vary greatly due to the design features of the device.
