A Comprehensive Guide to Core Professional Terms in the HVAC Industry
HVAC is an abbreviation for Heating, Ventilation, and Air Conditioning, widely used in building electromechanical systems, industrial temperature control, and building intelligence. The following is a compilation of frequently used industry terms and standard definitions, categorized into eight main areas : general fundamentals, heating systems, ventilation systems, air conditioning and refrigeration systems, air quality, automatic control systems, equipment components, and engineering parameters .
I. General Basic Terminology
1. HVAC : A general term for heating, ventilation and air conditioning systems. Its core function is to achieve controllable adjustment of indoor temperature, humidity, air cleanliness and airflow speed in buildings.
2. Heating, Ventilation and Air Conditioning : HVAC is the full Chinese name for building electromechanical engineering, which is one of the core specialties of building electromechanical engineering. It covers engineering contents such as indoor environmental temperature control, air replacement, and energy consumption control.
3. Indoor design parameters : The standard values for indoor temperature, relative humidity, fresh air volume, noise, etc., set to meet human comfort or process production requirements are the core basis for system design.
4. Outdoor meteorological parameters : extreme maximum/minimum temperature at the project site, outdoor calculation temperature and humidity for air conditioning in summer, and calculation temperature for heating in winter, etc., are used for equipment selection and load calculation.
5. Heating and cooling load : The amount of heat that needs to be added (heat load) or removed (cooling load) in the building interior, measured in W or kW, is a core indicator for selecting air conditioning and heating equipment.
6. Energy efficiency factor : The core parameter for measuring the energy utilization efficiency of an HVAC system, reflecting the ratio of equipment output energy to input energy consumption.
II. Heating System Terminology
1. Central heating : This is a heating method in civil buildings where heat is generated centrally from a unified heat source (boiler room, heat exchange station) and supplied to multiple buildings or rooms through a pipeline network.
2. Decentralized heating : There is no centralized heat source. Heating is provided to individual spaces through equipment such as wall-mounted boilers, electric heaters, and air conditioning heat pumps.
3. Low-temperature hot water heating : Hot water heating systems with a supply water temperature ≤60℃ and a return water temperature ≤50℃ are mostly used for underfloor heating and fan coil heating, offering high comfort and low energy consumption.
4. Underfloor heating (low-temperature radiant heating) : Heating is provided by heating pipes laid on the ground, mainly through heat radiation and supplemented by convection. The indoor temperature is uniform and there is no draft.
5. Radiator heating : Commonly known as radiator heating, it is a traditional heating method that uses hot water/steam to flow through radiators to heat indoor air via convection.
6. Heat exchange station : The intermediate heat exchange equipment room of the centralized heating system, which converts municipal high-temperature hot water/steam into low-temperature hot water for indoor heating through heat exchangers.
7. Constant pressure water replenishment : The core operation and maintenance process of the heating water system, which maintains stable water pressure in the system through a constant pressure device, automatically replenishes lost water, and prevents air blockage and water shortage in the system.
III. Ventilation System Terminology
1. Natural ventilation : A ventilation method that relies on the air pressure difference formed by the temperature difference and wind pressure between indoors and outdoors to achieve natural air replacement. It consumes no energy and is suitable for conventional civil buildings.
2. Mechanical ventilation : A ventilation method that uses fans to force airflow and achieve indoor and outdoor air exchange. The air volume is controllable and is not affected by the environment or climate.
3. Fresh air system : A ventilation system that specifically supplies fresh outdoor air into the room and filters and purifies it, which can replenish indoor oxygen and dilute harmful gases.
4. Exhaust system : A ventilation system that forces indoor polluted air, odors, exhaust gases and moisture to be expelled outdoors. It is widely used in kitchens, bathrooms and computer rooms.
5. Positive pressure ventilation : The system's fresh air intake is greater than its exhaust volume, making the indoor air pressure higher than the outdoor air pressure, thus blocking the intrusion of polluted outdoor air. It is often used in clean workshops and hospital wards.
6. Negative pressure ventilation : The system exhausts more air than it supplies fresh air, making the indoor air pressure lower than the outdoor air pressure, preventing the spread of harmful gases indoors. It is often used in bathrooms, laboratories, and kitchens.
7. Air exchange rate : The number of times indoor air is replaced per unit time (times/hour) is a core parameter in ventilation system design, and different functional spaces have corresponding specifications and standards.
8. Air valve : A control component installed on the air duct, used to adjust, cut off, and switch the air volume in the air duct. It is divided into manual air valve, electric air valve, fire damper, etc.
9. Fire damper : A special component for fire ventilation. It automatically closes the air duct in case of fire, preventing the spread of fire and smoke along the air duct. It is a mandatory fire safety inspection component.
IV. Terminology for Air Conditioning and Refrigeration Systems
1. Central air conditioning system : A large-scale air conditioning system that centrally generates cooling/heating and delivers it to each room through air ducts and water pipes. It is suitable for large buildings such as office buildings, shopping malls, and hotels.
2. VRF/Multi-Split System : Variable refrigerant flow air conditioning system, one outdoor unit connects to multiple indoor units, can independently control the temperature of each room, is energy-saving and flexible, and is suitable for both residential and commercial applications.
3. Air-cooled units : Refrigeration units that use outdoor air as the heat dissipation medium, do not require cooling water towers, are easy to install, and are suitable for small and medium-sized buildings.
4. Water-cooled units : Large-scale refrigeration units that use cooling water as the heat dissipation medium, used in conjunction with cooling towers, have high cooling efficiency and are suitable for large commercial buildings.
5. Heat pump unit : An energy-saving air conditioning device that can operate in both directions, providing cooling in summer and heating in winter. It achieves temperature control by transferring heat from the air and is divided into air source, ground source, and water source heat pumps.
6. Fan coil unit : A terminal device of central air conditioning. It uses a fan to drive air through the cooling and heating coils to achieve indoor cooling and heating. It is widely used in offices and hotel rooms.
7. Modular air conditioning unit : Large-scale centralized air conditioning terminal equipment that integrates functions such as filtration, humidification, cooling, heating, and air supply. It is suitable for large shopping malls and cleanrooms.
8. Refrigerant : Commonly known as coolant or refrigerant, it is the heat exchange medium in the air conditioning refrigeration cycle. It achieves refrigeration by absorbing and releasing heat through phase change. Commonly used models are R410A, R32, and R134a.
9. Chilled water : The heat exchange medium in the central air conditioning water system, low-temperature chilled water (7℃/12℃), used to deliver cooling capacity to indoor terminal equipment.
10. Cooling water : The water-cooled unit is equipped with heat exchange water, which is used to remove the heat generated by the compressor of the unit and circulate it through the cooling tower.
11. Condensation temperature/evaporation temperature : Core parameters of the refrigeration cycle, the critical temperatures at which the refrigerant releases heat during condensation and absorbs heat during evaporation, directly affecting the unit's refrigeration efficiency.
V. Air Quality and Humidification/Dehumidification Terminology
1. Relative humidity : The ratio of the actual water vapor content in the air to the saturated water vapor content at the same temperature (%RH). The comfortable humidity range for the human body is 40%~60%RH.
2. Humidification : The device replenishes water vapor into the air, increasing indoor humidity. It is suitable for dry winter environments and precision workshops.
3. Dehumidification : Removes excess moisture from the air, reduces indoor humidity, prevents condensation, mold, and dampness in equipment, and is suitable for the rainy season and humid areas.
4. Air filtration : The filter intercepts dust, particulate matter, catkins and other impurities in the air. It is divided into pre-filter, medium-efficiency filter and high-efficiency filter to meet different cleanliness needs.
5. Cleanliness : An indicator for measuring the cleanliness of indoor air. It is graded by the number of suspended particulate matter per unit volume of air and is often used in hospital operating rooms and electronics factories.
6. PMV/PPD Index : Human thermal comfort evaluation index, representing the predicted average thermal sensation and the predicted percentage of dissatisfaction, respectively, used to assess the comfort level of air-conditioned environments.
7. Condensation : When the air temperature is lower than the dew point temperature, water vapor condenses into water droplets. This phenomenon is likely to occur on low-temperature air ducts, walls, and equipment surfaces.
8. Dew point temperature : The critical temperature at which water vapor in the air reaches saturation and begins to condense. It is the core parameter for dehumidification and anti-condensation design.
VI. Terminology for Automatic Control and Energy Saving
1. BA System (Building Automation System) : Through intelligent controllers and sensors, it automatically monitors and adjusts the operating status of HVAC equipment to achieve automated and energy-saving operation of the system.
2. Sensors : HVAC automatic control and data acquisition components used to detect indoor and outdoor temperature, humidity, wind speed, water pressure, air quality and other data in real time.
3. Frequency converter : It controls the operating power of fans, water pumps and units by adjusting the motor speed, thereby reducing the no-load energy consumption of the equipment. It is a core energy-saving component.
4. Energy Efficiency Ratio (EER) : The energy efficiency index of refrigeration equipment, which is the ratio of cooling capacity to input electrical power. The higher the value, the better the energy-saving effect of refrigeration.
5. Coefficient of Performance (COP) : The energy efficiency index of heating/heat pump equipment, which is the ratio of heating capacity to input electrical power. It is the core standard for measuring the performance of heat pump equipment.
6. SEER (Seasonal Energy Efficiency Ratio) : A comprehensive energy efficiency index for air conditioning equipment throughout the year, taking into account the energy consumption performance under different seasonal operating conditions, and serving as the basis for energy-saving rating of the equipment.
7. Variable frequency control : The operating frequency of the equipment is automatically adjusted according to changes in indoor load to achieve on-demand cooling and heating, avoiding energy waste from constant power operation.
VII. Terminology for Core Equipment and Components
1. Compressor : The core power component of the air conditioning refrigeration system, which compresses refrigerant vapor, increases pressure and temperature, and drives the refrigeration cycle.
2. Condenser : A refrigeration and heat exchange component responsible for condensing high-temperature, high-pressure refrigerant vapor into a liquid state. It is divided into air-cooled and water-cooled types.
3. Evaporator : The core component for indoor heat exchange. Liquid refrigerant absorbs heat and evaporates into a gaseous state, absorbing heat from the indoor air to achieve a cooling effect.
4. Expansion valve : A refrigeration throttling component that reduces refrigerant pressure, regulates refrigerant flow, and controls the heat exchange efficiency of the evaporator.
5. Cooling tower : A special equipment for water cooling systems. It achieves heat dissipation by using air convection evaporation and circulating cooling water from the cooling unit.
6. Water pumps : Power equipment for water systems, including chilled water pumps, cooling water pumps, and heating circulation pumps, responsible for water circulation and transportation.
7. Air ducts : Air supply ducts for ventilation and air conditioning, made of materials including galvanized steel sheet, phenolic composite board, stainless steel, etc.
8. Air vents : Air outlets and return air components at the end of air ducts, including louvered air vents, diffusers, and swirl air vents, which are responsible for evenly distributing indoor airflow.
9. Flexible joint : A flexible connection component for the inlet and outlet of fans and water pumps, which reduces vibration and noise and prevents equipment vibration from being transmitted to pipelines.
VIII. Engineering Technology and Parameter Terminology
1. System commissioning : After the HVAC project is completed, the air volume, water pressure, temperature and operating parameters of the equipment are comprehensively tested and calibrated to ensure that the system operates in compliance with standards.
2. Hydraulic balance : Adjust the opening of valves in each branch of the water system to ensure that the water flow of each terminal device reaches the design standard, and avoid uneven heating and cooling and energy consumption imbalance.
3. Air volume balance : Adjust the opening of the air duct dampers to ensure that the fresh air volume, supply air volume, and exhaust air volume of each room meet the design requirements.
4. Thermal insulation and anti-condensation : Low-temperature air ducts and chilled water pipes are wrapped with thermal insulation material to reduce cold loss and prevent condensation and dripping on the pipe surface.
5. System flushing : After the construction of the heating and air conditioning water system, flush out impurities and silt from the pipes to prevent blockage of equipment and pipes.
6. Static pressure : The air pressure inside the duct and air passage, divided into external static pressure and internal static pressure, which determines the air supply distance and the appropriate duct length.
7. Air resistance : The resistance generated by air flowing in ducts and equipment. Excessive air resistance will lead to insufficient air volume and increased equipment energy consumption.
8. Water resistance : The resistance to water flow in pipes and equipment is a core parameter for pump selection and system hydraulic design.
