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Commonly Used HVAC Terms and Explanations Part 4 

Commonly Used HVAC Terms and Explanations Part 4 


Commonly Used HVAC Terms and Explanations Part 4 

HVAC System

19. Economic heat transfer resistance: It is the heat transfer resistance when the sum of the building envelope and unit area construction cost (depreciation cost of initial investment) and use cost (heating operation cost and equipment depreciation cost apportioned by the unit area of the envelope structure) reaches the minimum value. thermal resistance

20. Comprehensive ventilation: comprehensive ventilation is to ventilate the entire room, and use the fresh air sent into the room to dilute the concentration of harmful gases in the room to below the allowable range of the hygienic standard. At the same time, the indoor polluted air is discharged into the outdoor atmosphere directly or after purification.

21. Accident ventilation: Accident ventilation is an exhaust system set up to prevent a large amount of harmful gas or explosive gas that may be suddenly released when accidental accidents or failures occur in production equipment in the production workshop, causing greater loss of personnel or property. It is to ensure safe production and a necessary measure to protect workers' lives.

22. Number of air changes: The number of air changes n refers to the ratio of the ventilation volume L (m3/h) to the room volume V (m), that is, n=L/V.

23. Air quality balance: In a ventilated room, no matter which ventilation method is used, the quality of air entering the room per unit time should be equal to the quality of air discharged at the same time. That is, the air quality in the ventilated room should be balanced.

24. Heat balance: Heat balance means that the total heat gain and total heat loss in the room are equal to keep the temperature in the room stable.

25. Fan air volume: refers to the volume of gas delivered by the fan in unit time when the fan works under standard conditions. Represented by the symbol L, the unit is m3/h.

26. Fan pressure: refers to the sum of the dynamic pressure and static pressure that should be obtained per cubic meter of air passing through the fan, represented by the symbol P, and the unit is Pa.

27. Partial pressure of water vapor Pq: The water vapor in the humid air occupies the volume of the humid air alone, and the pressure generated when it has the same temperature as the humid air is called the partial pressure of water vapor in the humid air. The water vapor partial pressure reflects the amount of water vapor in the air. The more water vapor in the air, the greater the water vapor partial pressure.

28. Saturated water vapor partial pressure Pq.b: At a certain temperature, when the water vapor content in the humid air reaches the maximum, the humid air is said to be in a saturated state, and the corresponding water vapor partial pressure at this time is called the saturated water vapor partial pressure.

29. Moisture content: Moisture content (d) is defined as the amount of water vapor contained in moist air corresponding to one kilogram of dry air. Its unit is expressed in g/kg. The moisture content changes with the amount of water vapor in the air, and it can exactly reflect the amount of water vapor in the air.

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