The difference between Nm3 and m3

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Basic definition: Standard cubic meter (Nm3): A standard cubic meter is the volume of a gas measured under specific standard conditions. Generally, standard conditions refer to a state where the temperature is 0 degrees Celsius (273.15 K) and the atmospheric pressure is 101.325 kPa (1 atmosphere). The standard cubic volume represents the volume of a gas under standard conditions. In gas flow meters, standard cubic units are used to represent the gas flow rate measured under standard conditions; this allows the effects of temperature and pressure changes on the measurements to be eliminated, thereby enabling comparison of flow rates under different conditions. Cubic meter (m3): A cubic meter is a universal unit of volume that represents the volume of a cube under any conditions. It does not take into account the temperature and pressure of the gas; it merely indicates the space occupied by the object. The unit of cubic flow rate is usually cubic meters per second (m3/s) or cubic meters per hour (m3/h). To illustrate the difference, consider a gas compressor or fan: when used in Tibet versus Shanghai, if the flow rate is expressed in cubic meters, there will be a significant difference, and as a result the energy consumption, as well as the costs associated with purchasing and maintaining such equipment, will also differ greatly. However, when the value is converted to standard cubic meters, the differences disappear. The unit for measuring gas flow rate is the standard cubic meter; it is often referred to as a mass-like unit, as it appears to be a volume unit but is actually a mass unit. It has no relation to the pressure or temperature at the location where it is used. The standard cubic meter is a unit of gas volume under conditions of a pressure of 101325 Pa and a temperature of 20°C. The standard gas conditions specified in the product descriptions of some domestic manufacturers of gas compressors, fans, etc., refer to the state of air at a temperature of t=20°C, an absolute pressure of P=0.1 MPa, and a relative humidity of ф=65%. Under these standard conditions, the density of air is 1.185 kg/m3. In the early samples, the pressure was P=1 atm; these differences are actually caused by the SI system. In other words, the air standard conditions in some domestic manufacturing enterprises differ from these nominal operating conditions. Nm3 is a standard cubic meter, with measurement conditions of a pressure of 101325 Pa and a temperature of 0°C. The full definition of Nm3/h is: cubic meters per hour under nominal conditions; “N” stands for nominal conditions, which refer to the conditions under which the testing is carried out. The air conditions referred to as nominal operating conditions are: 1 standard atmosphere, a temperature of 0°C, and a relative humidity of 0%, which means a gas on a dry basis. Calculation of the standard state under operating conditions: 1. Flow rate under actual operating conditions: Qf = QN × ÷ m3/h. 2. Flow rate under standard conditions: QN = Qf × ÷ m, where m is the mass in kg, p is the gas pressure in Pa, V is the gas volume in m3, M is the molar mass of the gas, and t is the gas temperature in °C. The standard density of the gas is in units of kilograms per cubic meter