Note:

This calculator determines the required capacity (Kvr) of a steam valve under subsonic flow. It relates the steam mass flow rate (ṁs) to the upstream and downstream pressures (P1 and P2) to determine the necessary valve capacity.

Parameters:

• Kvr (Required capacity at lift 'H'): The flow coefficient required at a specific lift, measured in cubic meters per hour bar (m³/h bar).
• ṁs (Steam mass flow rate): The amount of steam flowing through the valve per unit time, measured in kilograms per hour (kg/h).
• P1 (Upstream pressure): The pressure of the steam before it enters the valve, measured in bar absolute (bar a).
• P2 (Downstream pressure): The pressure of the steam after it passes through the valve, measured in bar absolute (bar a).
• x: A dimensionless ratio representing the pressure drop across the valve, calculated as (P1 - P2) / P1.

Constants Explained:

• 12: A conversion factor for aligning units.
• 5.67: An empirical coefficient derived from steam thermodynamic properties and valve discharge characteristics.
• 0.42: An empirical constant related to the critical pressure ratio for steam in subsonic flow.

Real-life applications:

• Power Plants: To size steam valves in turbine systems and boiler feed lines.
• Chemical Plants: To control the flow of steam in reactors and heat exchangers.
• Refineries: To regulate steam flow in distillation and other processes.
• HVAC Systems: In large buildings and industrial facilities to control steam for heating.

Important:

Please note that ṁs and P1 must be greater than zero. Also, P1 must be greater than P2 for a pressure drop to occur. Zeros are not accepted as inputs because they would result in undefined or illogical calculations.

Conclusion:

This formula provides a way to determine the required steam valve capacity based on flow rate and pressure conditions, ensuring efficient and safe operation of steam systems.