Quality, Volume, Specific volume
Quality: means the weight of air. The unit is always “mg, g, kg, ton”.
Volume: means the capacity of vessels which air exits. The unit is normally “mm3, cm3”.
Specific volume: means the volume which per unit substance has. The unit is normally “ m3/kg, the liquid specific volume is “1/kg”
Pressure, intensity of pressure, atmosphere, absolute pressure, relative pressure.
Pressure: The strength which is from air molecular striking with the wall of vessels.
Intensity of pressure: The pressure to the unit area of vessels. The unit is normally “mmHg/cm2, the international common unit is “Pa, KPa, MPa”. The formula: 1mmHg=133.3Pa=0.1333KPa, 1MPa=1000KPa=1000000Pao1ATA=0.1MPao.
Atmosphere: The pressure which is atmosphere to the earth surface, the symbol is “B”.
Absolute pressure: Directly force to the vessels or objects. The absolute pressure needs the area to be vacuum, the symbol is “PABS”.
Relative pressure: It also means gauge pressure, the pressure is from the pressure meter, vacuum gauge, U type pipeline and etc. The pressure test depends on the atmosphere, the symbol is “Pg”. The formula is PABS=B+Pg
Temperature, absolute temperature, relative temperature, critical temperature, critical pressure.
Temperature: It is the average value of thermal motion of matter. Air temperature is from the air molecular thermal motion. The unit of air temperature is “℃”, the ice temperature of water is 0 ℃. Absolute temperature: at the physics , the unit is “K”, it regard －273℃ as 0 degree. The relation between Celsius and absolute temperature is T=t＋273. But the British scientist usually use “ Fahrenheit”, the symbol is “oF”.
Critical temperature: Because the air can be liquefied just a little pressure and temperature, so as the higher temperature, the pressure of liquefaction should be higher, but when the temperature is over the certain value , the air can’t be liquefied any more, even huge temperature inside. So the certain value of the temperature is critical temperature and the pressure at this certain value is critical pressure.
Dew point, vaporization,condense
Dew point: the temperature of the moisture content from the unsaturated to saturated in the air. When the unsaturated steam become saturated steam, very little dewdrop will appear, the temperature when the dewdrop appeared is called “ dew point”.The dew point depends on the pressure,so the dew point can be distinguished atmosphere dew point and pressure dew point. Atmosphere dew point means under the atmosphere pressure the condense temperature, the pressure dew point, it means the condense temperature under this kind of pressure. Both can be conversed ( please check the conversion table), such as when the temperature is 0.7Mpa, the pressure dew point is 5℃, so the relative atmosphere dew point is －20℃. If no specification, the dew point is atmosphere dew point for the air industry.
Vaporization: It means the process of substance from liquid to be air, it includes evaporation and boiling.
Condense: it is the process of air from air to be liquid.
Purity is the key element of the technical parameter in air industry. For example, in China the nitrogen purity can be divided into industrial nitrogen, purified nitrogen and high purified nitrogen. The purity for the three kinds of purity is 99.5% (O2 content is below 0.5%), 99.99% ( O2 content is below 0.01%) and 99.999%( O2 content is below 0.001%).
Flow, volume flow, quality flow
Flow: it means air volume which flows through the section area in unit time during the process of the air motion. There two kinds of flow, the volume follow and quality flow.
Volume flow: it is the air volume which flows through the section area of pipeline.
Quality flow: it is the quality of air which flows through the section area of pipeline.
In air industry the unit of volume flow is m3/hr (or L/H). Because of the relationship between volume and temperature, pressure and moisture., in order to distinguish, normally the volume flow is at the standard ( the temperature is 20℃, the pressure is 0.101 Mpa, the relative moisture is 65%), so the flow unit is Nm3/hr , and the “N” means standard situation.
Air can be compressed, when the air goes through the air compressor, the volume of the air will be compressed, as the air which is compressed called compressed air. The compressed air has a lot of impurity such as: 1. Water, include spray, steam, condense water. 2. Oil: include greasy dirt, oil steam 3. All kinds of object substance: metal powder, rubber powder, sealed material, tar particle and etc. Compressed air can be pressurization, cooling, adsorption to remove the steam. The liquid water can be removed through heating, flite, and mechanical separation.
Adsorption, membrane penetration
Adsorption: the air is optionally concentrated by the holes of surface of the substance. The adsorption material called adsorption medium, and the material which is full of holes on the surface called adsorbent. The connection between adsorption medium and the adsorbent is the chemical bond, but adsorption medium’s resolution depends on the temperature rising and low down the pressure in the air. The other situation is the chemical reaction between the adsorption medium and substance adsorbent called chemical adsorption, this kind of adsorption can’t regenerate.
Membrane penetration: It is the optional choosing for the air element by the polymer during the air purging. The gas composition is dissolving into the surface of the polymer membrane, the density of the polymer is different depends on the membrane’s delivering, so it is differential concentration, in order to keep the concentration one side pressure is higher than the other side is necessary.