Calculation of the steam flow rate through a control valve
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There is an existing control valve, an old model (ZMXBM-40K), DN100, 4.0MPa, CV‑125. Please provide the calculation formula for the maximum flow rate when this valve is used at 1.2 MPa upstream and 0.65 MPa downstream, along with detailed information on the model.
It is known that any gas flow rate = density * velocity * area. The area is known; the density can be calculated using pressure and temperature (via the ideal gas equation or by consulting tables), while the velocity is determined by solving equations using two formulas. Based on the continuity of flow (that is, the flow rate calculated at the section before the valve should be equal to the flow rate calculated at the section after the valve), two unknowns—the velocity before the valve and the velocity after the valve—are introduced, resulting in an equation. According to the principle of energy conservation, the pressure potential energy before the valve plus the pressure energy after it is equal to the valve’s potential energy plus the kinetic energy behind the valve. With two equations and two unknowns, the velocity can be determined, and thus the flow rate can be calculated. This is only a theoretical approach; there may be slight differences from the actual traffic volume