Parameters of the compressor

Thread Content

This post was last edited by sunjl1981 on 2013-1-6 at 19:58. I. Temperature Temperature is a way of measuring the energy level of a substance at a given time. (Or, more simply, how much heat or cold something has.) The temperature range is based on the freezing and boiling points of water. On a Celsius thermometer, the freezing point of water is 0 degrees, and its boiling point is 100 degrees. On a Fahrenheit scale, the freezing point of water is 32 degrees, and its boiling point is 212 degrees. Converting from Fahrenheit to Celsius: Fahrenheit = 1.8 × Celsius + 32, Celsius = 5/9 (Fahrenheit – 32). 1) Absolute temperature. This is the temperature explained using absolute zero as a reference point. The zero point is minus 459.67 degrees Fahrenheit or minus 273.15 degrees Celsius. Absolute zero refers to the temperature at which all heat has been removed from a substance, or theoretically, the temperature reached when a gas occupies zero volume. 2) Cooling temperature difference The cooling temperature difference is a term used to determine the efficiency of a cooler. Since a cooler cannot achieve 100% efficiency, we can only measure its efficiency using the cooling temperature difference. The cooling temperature difference is the difference between the temperature of the cold water or air entering the cooler and the temperature of the compressed air after it has been cooled. 3) Intercooler: An intercooler is a device used to cool the compressed air or gas between the various stages of a multi-stage compressor, thereby reducing its temperature. The intercooler reduces the compression power by lowering the temperature of the compressed air entering the next stage, thereby helping to improve efficiency. II. Dew Point and Relative Humidity 1. Dew Point and Relative Humidity Just as dew forms when the temperature drops at night, a drop in temperature within a compressed air system also results in the formation of water vapor. The dew point is the temperature at which moist air cools down to saturation while keeping its water vapor partial pressure constant. Why is this? Air containing moisture can only hold a certain amount of water. If the volume is reduced by pressure or cooling, there isn’t enough air to accommodate all the moisture, so the excess water precipitates as condensation. The air leaving the cooler is usually completely saturated. The condensate water inside the separator illustrates this point; therefore, any decrease in air temperature results in the formation of condensate water. The set humidity can be considered as the weight of water vapor contained in moist air, that is, the ratio of the weight of water vapor to the weight of dry air. Relative humidity ψ = χ × Humidity Ps / χ0 – Saturated absolute humidity Pb. When Ps=0 and ψ=0, it is referred to as dry air ； When Ps=Pb and ψ=1, it is called saturated air. Absolute humidity – the weight of water vapor contained in 1 cubic meter of moist air. Gs—weight of water vapor; χ=----------------------; V—volume of moist air. Weight of water vapor / Humidity =--------------------- / Weight of dry air. 2. Saturated air: Saturation occurs when no more water vapor can be contained in the air; any increase in pressure or decrease in temperature will result in the formation of condensed water. 3. Water-gas separator: A water-gas separator is a device used to collect and remove the water that condenses from air or gases during the cooling process. A gas storage tank is a container used to store the compressed air and gases discharged by a compressor. The air storage tank helps to eliminate pulses in the exhaust pipeline, and it can store and supply compressed air when the demand exceeds the compressor’s capacity. 4. Drier A drier is a device used to dry air. In our terms, that is using its dry compressed air. The air leaving the cooler is usually completely saturated, which means that any cooling will result in condensation. A freeze-dryer removes moisture by lowering the temperature of compressed air, and then reheats the air to a temperature close to its original level. A regenerative dryer is a device that passes air through a filter containing chemicals to remove moisture. This device can absorb water vapor more effectively than a refrigeration-type device. 1) Standard condition: The standard condition is defined as the volume of air supplied to the user’s system under conditions where the intake pressure of the air is 0.1 MPa and the temperature is 15.6°C (while the industry standard in China is 0°C). If standard conditions are required to reflect actual operating conditions such as altitude, temperature, and relative humidity, the actual intake conditions must be converted to standard conditions. 2) Normal air: Air under conditions of a specified pressure of 0.1 MPa, a temperature of 20°C, and a relative humidity of 36% is considered normal air. Normal air differs from standard air in terms of temperature and contains moisture. When there is moisture in the air, removing that moisture will result in a decrease in the volume of air. 3) Inlet condition: The air at the compressor inlet. 4) Elevation is measured vertically upward from sea level; it simply refers to the height above sea level. Elevation is an important factor in compressor engineering, as the higher the elevation, the thinner the air becomes and the lower the absolute pressure. Since the air is thinner at higher altitudes, the cooling effect of motors is reduced, which limits standard motors to operating only at certain altitude levels. The maximum allowable operating altitude for EP200 standard units is 2286 meters. 5) Factors affecting displacement: Pj, Tj, altitude, n, V_excess, leakage, etc. 6) Effect of altitude on compressors: 1. The higher the altitude, the thinner the air, the lower the absolute pressure, the higher the pressure ratio, and the greater the Nd value ； 2. The higher the altitude, the worse the cooling effect, and the greater the temperature rise of the motor ； 3. The higher the altitude, the thinner the air; thus, the fuel-air ratio in diesel engines increases, and N decreases. 7) Volumetric flow rate: The volumetric flow rate refers to the amount of air drawn in by the compressor per unit of time under standard conditions. Unit: M3/min (cubic meters per minute). The flow rate is expressed in N M3/min. 1 CFM = 0.02832 m3/min, or 1 m3/min = 35.311 CFM. S–standard conditions; A–actual conditions. 8) Clearance volume: The clearance volume refers to the volume remaining at the end of a stroke in positive-displacement volumetric (reciprocating or screw) compressors. The compressed air in this volume returns to the inlet after expansion, and it has a significant impact on the volume coefficient. 9) Load factor: The load factor refers to the ratio of the compressor’s average output over a certain period of time to the compressor’s maximum rated output. It would be unwise to sell compressors to users that meet exactly their greatest needs, as adding one or several additional components could cause a drop in pressure in the factory. To avoid this situation, Ingersoll Rand has for many years recommended the use of a load factor: take the maximum value of the air volume required by the user’s system and divide it by a load factor of 0.9 or 0.8. (Or any factor that a user considers to be a safety margin) This comprehensive air volume selection takes into account unexpected increases in air demand. Some minor expansions can be carried out without the need for additional capital investment. 10) Air volume testing 1. Reciprocating compressor cylinder volume The volume of a compressor cylinder refers to the volume occupied by the piston’s movement minus the volume occupied by the piston rod. It is usually expressed in cubic meters per minute. The volume of a multi-stage compressor is only that of the first compression stage, as the gas that passes through all stages comes from the first stage. 2. Testing: The low-pressure nozzle test is a method for accurately measuring the air supplied by a compressor. This method has been recognized by the Compressed Air and Gas Society and is also accepted by the ASME Energy Test Code Committee. Descriptions in ASME PTC-9 regarding the use of low-pressure nozzles to test reciprocating compressors. ASME PTC-10 contains descriptions regarding the use of low-pressure nozzles to test dynamic compressors. . Note ← ) # ← , .