Pakarab fertilizers limited multan
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| 3.7 Mass Flow Real gases roughly follow the ideal gas law, which states that pressure, temperature, and volume of a gas are interrelated. The gas law is PV = nRT Where, P pressure of the gas V volume of the gas n = amount of gas R = ideal gas constant T = temperature of the gas. If the pressure is increased, with the temperature held constant, the volume decreases. If the temperature is increased, with the volume held constant, the pressure increases. The only constant is the mass of the gas, which therefore does not change. Mass flow is the molecular measurement of the gas flow rate. Mass flow is usually expressed in units of mass per unit time kilograms/hour (kg/hr), for example. However, gas flow is usually measured by volume—for example, liters/hour (L/hr). Because volume depends on temperature and pressure. Mass Flow meters Coriolis meter is most commonly used for liquids. Its operation is based on the natural phenomenon referred to as the Coriolis force. 75 Field Instrumentation GEN Rev) Coriolis unit consists of a U-shaped flow tube enclosed in a sensor housing connected to an electronics unit. The U shaped tube is vibrated by a magnetic device located at the bend of the tube. As the liquid flows through the tube, it takes on the vertical movement of the tube. The force of the flowing liquid resists the force of the tube movement, causing the tube to twist. The amount of twist is directly proportional to the mass flow rate of the liquid flowing through the tube. Magnetic sensors on the sides of the tube measure the tube velocity, which changes as the tube twists. The electronics unit converts the sensor readings to a voltage that is proportional to mass flow rate. These meters are useful for measuring liquids whose viscosity varies with the velocity (adhesives, for example, but because of the relatively small U-tube, the Coriolis meter causes a substantial pressure drop. |