Highlights of HVAC newcomers: summary of basic knowledge points of air conditioning?

1 cooling load: refers to the cooling capacity (or heat discharged from the room) that needs to be supplied to the room at a certain moment in order to keep the room temperature constant.

2 heat gain: the sum of the heat entering the air-conditioned room at a certain moment.

Outdoor comprehensive temperature: it is equivalent to increasing the outdoor temperature tw by an additional value caused by solar radiation, rather than the actual temperature.

4 Central air conditioning system: This system concentrates all air conditioning equipment and ventilators in the air conditioning room.

5. Primary return air system: In the all-air system, only one return air is used for energy recovery.

6 Secondary return air system: In the all-air system, the energy is recovered by secondary return air.

Minimum fresh air ratio: the ratio of fresh air volume to air supply volume under the design condition of air conditioning system, expressed by m% = GW/g.

Double air duct system: The system has a cold air duct and a hot air duct, and the air in two states enters the room after being mixed in the double air duct mixing box in each air-conditioned room or area.

VAV system: A centralized air-conditioning system that maintains the parameters of air-conditioned rooms by changing the air supply volume.

10 water content: the ratio of water vapor mass in wet air to dry air mass.

1 1 Return air: the air that is completely or partially returned to the air conditioner after being extracted from the air-conditioned space.

12 fresh air: air conditioned from the outside enters the air-conditioned room.

13 heat and humidity ratio: the ratio of enthalpy change to moisture content change of air.

14 air exchange times: the ratio of the air supply volume (by volume) flowing through the room per unit time to the room volume.

15 comfort air conditioning: an air conditioning system that determines air conditioning parameters according to human requirements for temperature and humidity, also known as civil air conditioning.

16 process air conditioning: an air conditioning system that determines air parameters according to different requirements of process and production and taking into account the requirements of human health.

17 machine dew point: the saturated air state corresponding to the average temperature of the outer surface of cooling coils in the air conditioner, and also refers to the air temperature close to saturation state after being cooled by the water spray chamber.

18 air conditioning base: refers to the base index of temperature and relative humidity in air-conditioned rooms.

19 air conditioning accuracy: refers to the index that the temperature and humidity of an air-conditioned room are allowed to deviate from the air conditioning base.

All-air system: an air-conditioning system in which all heat and humidity loads in an air-conditioned room are borne by the air after centralized treatment.

2 1 air-water system: refers to an air-conditioning system in which the cold (hot) load and wet load of an air-conditioned room are handled by air and water respectively.

Semi-centralized air conditioning system: It means that in addition to the centralized central air conditioning unit, each room is also equipped with a terminal device (fan coil system) for handling air.

23 solar altitude angle: refers to the angle formed by solar rays and the ground they radiate.

Non-isothermal jet: In air conditioning system, when the outlet temperature of air supply jet is different from room temperature, it is called non-isothermal jet.

25 air supply temperature difference: the difference between the air supply temperature entering the room and the room temperature.

26 Cold Jet: In the air conditioning system, when the outlet temperature of the air supply jet is lower than the indoor temperature, its jet is called cold jet.

27 Hot Jet: In the air conditioning system, when the outlet temperature of the air supply jet is higher than the indoor temperature, its jet is called hot jet.

28 Velocity Equivalent Diameter: If the air velocity in a circular pipe is equal to that in a rectangular pipe, and the frictional resistance per unit length is equal, then the diameter of the circular pipe is called the velocity equivalent diameter of a rectangular pipe.

29 Flow Equivalent Diameter: If the air flow in a circular pipe is equal to that in a rectangular pipe and the friction resistance per unit length is equal, then the diameter of the circular pipe is called the flow equivalent diameter of a rectangular pipe.

30 Hydraulic radius: the ratio of the flow section to the wet perimeter when the fluid passes through the pipeline (or air duct).

3 1 moisture evolution coefficient: the ratio of total heat to sensible heat in the process of heat and moisture exchange of air through surface cooler.

Water spraying coefficient: the ratio of the air quantity passing through the water spraying chamber to the total water spraying quantity.

Contact coefficient: in the heat exchange process of water spray chamber or surface heat exchanger, the coefficient indicating the closeness between the actual process and the ideal process.

Dry cooling: the cooling process in which the average temperature of the cooling medium is higher than the initial dew point temperature of the cooled air. Also known as isothermal cooling.

Wet cooling: the cooling process in which the average temperature of the cooling medium is lower than the initial dew point temperature of the cooled air.

Air distribution: measures to make the air entering an air-conditioned room flow indoors and distribute it reasonably.

37. Resistive muffler: muffler equipment made of sound-absorbing materials or structures.

38. Resistant muffler: Noise elimination equipment made by changing the cross section of pipes or connecting vibration chambers side by side.

1. According to the concentration of air handling equipment, air conditioning systems can be divided into: (centralized air conditioning system), (semi-centralized air conditioning system) and (decentralized air conditioning system).

2. Under the same atmospheric pressure and temperature, the same volume of wet air is lighter than dry air.

3. When air is in direct contact with water for heat and moisture exchange, the driving force of sensible heat exchange is (temperature difference), the driving force of mass exchange pair is (water vapor partial pressure difference), and the driving force of total heat exchange is (enthalpy difference).

4. The main factors affecting human thermal comfort are (temperature, humidity, airflow speed, surface radiation temperature, human activities, clothing), etc.

When the weather turns from sunny to cloudy, the atmospheric pressure will be (decreased), and the atmospheric pressure in winter in the same area will be (higher) in summer.

6. Two state parameters (outdoor dry bulb temperature in summer) and (outdoor wet bulb temperature in summer) should be adopted to determine the outdoor design parameters of air conditioners in summer; Two state parameters (outdoor dry bulb temperature in winter) and (outdoor relative humidity in winter) should be adopted to determine the outdoor design parameters of air conditioning in winter.

7. The surface heat exchanger can only realize three air treatment processes: (equal humidity cooling process), (equal humidity heating process) and (cooling dehumidification process).

8. On the i-d diagram, treating air with circulating water spray can be regarded as (isenthalpic humidification), treating air with steam spray can be regarded as (isothermal humidification), and treating air with heater can be regarded as (isothermal heating).

9. Air supply outlets commonly used in air conditioning systems are (diffuser, shutter, orifice plate, nozzle, swirl air supply outlet) and other types.

10. Among various angles between the sun and the earth, the solar altitude angle has the greatest influence on the intensity of solar radiation reaching the ground.

1 1. The task of air conditioning is to keep certain technical indicators (temperature), (humidity), (airflow speed) and (cleanliness) in a specific space or room under any natural circumstances.

12. The indoor temperature and humidity of an air-conditioned room are usually specified by two sets of technical indicators, which are called (air conditioning base) and (air conditioning accuracy) respectively.

13. According to the type of medium used for indoor load, air conditioning systems can be divided into (all-air system, all-water system, air-water system and refrigerant system).

14, when the indoor heat and humidity load changes, in order to keep the indoor temperature and humidity parameters unchanged, the method of adjustment (reheating) is often adopted.

15, the primary return air constant air volume regulation system, compared with no dew point air supply, the main difference of its summer cooling load is (reheat). When the indoor load is the same, the dew point air supply needs less air.

16, air conditioning engineering according to the size of filtered dust particles, commonly used filters are (coarse filter) (medium filter) (high efficiency filter).

17, the secondary return air system works in summer, and the load of surface cooler or spray room consists of (indoor cooling load) and (fresh air cooling load).

18, air conditioning system is generally mainly composed of (air filtration part, air heat and humidity treatment part, air transportation part, air distribution part, cold and heat source part) and other parts.

19, air conditioning water system, according to the characteristics of water quantity. It can be divided into (constant water system) and (variable water system).

20. In air conditioning engineering, the thermal expansion coefficient of surface cooler is also called (moisture separation coefficient), and the moisture separation coefficient reflects (condensed water precipitation).

2 1, (input energy utilization coefficient) is usually used as an economic index to evaluate air distribution.

22, air conditioning water system, according to the characteristics of water pressure classification, divided into (open system) and (close system).

23, air conditioning water system, according to the classification of supply and return pipeline, and divided into (double pipe system), (three pipe system) and (four pipe system).

24. The place where the water system bears the greatest pressure is (the suction port of the water pump).

25, air conditioning water system, according to the classification of water supply resistance balance along the way, and divided into (water supply in the same direction) and (water supply in different directions), (water supply in the same direction) basically do not need to do resistance balance.

26. For each fire zone, the order of maintaining positive pressure in each zone is air-conditioned room (less than) evacuation staircase front room (less than) stairwell or elevator room.

27. In the air volume design of VAV system, the minimum air volume is generally determined by the maximum air volume (40%-50%).

28, air conditioning system smoke control usually adopts (natural exhaust), (mechanical exhaust) and (pressurized exhaust) three ways.

29, VAV system has the advantage of energy saving, the main reason is that it can (reduce the air supply) and (reduce the energy consumption of fan motor).

30, in the unrestricted jet, when Archimedes number ar >; 0, airflow direction (upward bending); When Archimedes number ar

I believe that after the above introduction, everyone has a certain understanding of HVAC newcomers' highlights: summary of basic knowledge of air conditioning. Welcome to Zhong Da for more information.

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