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Vocabulary

HVAC/R: Heating, ventilation, and air conditioning/Refrigeration.

Chiller: A device that is used to prepare cool water in the air conditioning industry.

Air conditioner: A device that delivers hot air in winter and cool air in summer to the environment through a channel.

Heat pump: Refrigeration cycle that works in reverse and uses the heat exchanger inside the room as a heater (condenser) in winter.

Cooling tower: A device that is responsible for cooling the return water from the condenser when using a water-cooled chiller.

Refrigerant: The gas used in the refrigeration cycle.

Superheat: The difference between the measured temperature of the suction line and the equivalent temperature of the gas pressure at the evaporator.

Subcool: The temperature difference of the liquid leaving the condenser with the Saturated temperature of the condenser.

Set point: The set point is the desired value in the control process of a parameter. The purpose of the controller is to bring the desired parameter to the set point.

Compressor: A device used to make a gas) denser or increase the pressure of a gas.

COP: The performance coefficient of the refrigeration cycle, which is equal to the ratio of the cooling produced by the cycle (for example, in kilowatts) to the work used to produce this cooling (in kilowatts).

Condenser: a heat exchanger that can be a shell-tube, plate, or fin-tube exchanger and is responsible for transferring cycle heat to the outside environment.

Evaporator: a heat exchanger that can be a shell-tube, Flodded, plate exchanger, or DX coil and is responsible for transferring cold to water or air.

Expansion valve: A device that is used to reduce pressure in an enthalpy-constant manner.

Adiabatic humidifier: A humidifier in which water evaporation is used in a constant enthalpy process to increase humidity.

Isothermal: A humidifier that heats water to its boiling point to increase humidity.

Superheat: of the suction line: the difference between the temperature of the suction line and the equivalent temperature of the gas pressure in the evaporator.

Discharge line superheat: the difference between the temperature of the discharge line and the equivalent temperature of the gas pressure in the condenser.

Defrost: The act of melting the evaporator ice in order to restore its efficiency.

Defrost is required in cold stores or subzero refrigerators and in the condenser of heat pump systems.

This process is done in different ways such as hot gas bypass or electric heater.

Hot gas: A type of defrost in which hot gas from the discharge line is bypassed and used to melt evaporator ice.

Damper: A device to control the flow rate and adjust the air pressure at different points of the channel.

Dry temperature: Air temperature measured with a regular thermometer.

wet temperature: The temperature of the air is measured by a thermometer whose bubble is covered by a wet wick that is exposed to a rapid flow of air.

Relative humidity: The ratio of the mass of water vapor in the air to the mass of saturated water vapor at the same temperature.

Absolute humidity (humidity ratio): the ratio of the weight of water vapor in the air to the weight of dry air.

Dew point temperature: The temperature at which the condensation of moisture begins when cooling the air.

enthalpy: It is the total energy content of a system at constant pressure and temperature.

Chart of air characteristics (psychrometric): a chart that is used to speed up calculations related to changes in temperature, humidity and air enthalpy.

EXV: Electronic expansion valve

EEV: Electronic expansion valve

TXV: Thermostatic expansion valve

TXV: Thermostatic expansion valve

LT: sub-zero freezers

MT: up-zero refrigerators

pump down: Pump down is a function to protect the compressor during start. This function turns on the compressor by closing the EXV or the liquid line solenoid valve or both, so that the liquid in the evaporator is completely drained. In this way, there will be no risk of the evaporator liquid being sucked into the compressor at the next start.

Cross-flow heat recovery exchanger:  heat exchangers that provide the possibility of heat transfer between two air streams under the influence of temperature difference.

A rotary heat recovery exchanger:  heat exchangers that consist of a rotating rotor with thousands of holes. they are installed vertically in the air duct, so that half of it is in the outgoing air path and the other half is in the return air path.

liquid receiver: It is a tank that is installed at the outlet of the condenser, usually before the expansion device and is designed to store the refrigerant.

sight-glass: A sight-glass is used to visually check if the expansion device is being fed properly.

filter drier: The purpose of the filter in an air conditioning or refrigeration unit is to remove moisture from the refrigerant as well as to remove solid particles that may be in the line and could clog the expansion device or damage the compressor.

distributor: Generally, they are capillary tube systems that evenly distribute the refrigerant that exits the expansion valve to separate parallel circuits that make up the evaporator coil.

four-way valve: Four-way valves are used to completely reverse the heat pump cycle. This turns the evaporator into a condenser and the condenser into an evaporator. Such valves may be used to facilitate the use of the system for heating and cooling or to provide an efficient and energy-optimized defrost method.

Oil separator: It is usually installed at the outlet of the compressor and its purpose is to separate the oil introduced by the refrigerant gas discharged by the compressor, recover it and transport it directly to the compressor.

Accumulator: The liquid separator is a hermetic tank like the liquid receiver, which is installed in the opposite part of the refrigerant circuit, i.e. the compressor suction line. The purpose of using it is to store the refrigerant in the low-pressure section and separate the refrigerant in the liquid phase from the vapor.