Steam Choked Flow Calculator

Choked Flow Equation:

\[ Q = P_1 \times A \times \sqrt{\frac{k}{R T}} \times \left(\frac{2}{k+1}\right)^{\frac{k+1}{2(k-1)}} \]

Upstream Pressure (P1):

Flow Area (A):

m²

Specific Heat Ratio (k):

Gas Constant (R):

J/(kg·K)

Temperature (T):

Choked Flow Rate (Q):

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1. What is Choked Flow?

Choked flow occurs when the flow rate of a fluid through a restriction cannot increase despite a decrease in downstream pressure. This phenomenon is critical in steam systems and compressible fluid dynamics where maximum flow conditions are reached.

2. How Does the Calculator Work?

The calculator uses the choked flow equation:

\[ Q = P_1 \times A \times \sqrt{\frac{k}{R T}} \times \left(\frac{2}{k+1}\right)^{\frac{k+1}{2(k-1)}} \]

Where:

\( Q \) — Choked flow rate (kg/s)
\( P_1 \) — Upstream pressure (Pa)
\( A \) — Flow area (m²)
\( k \) — Specific heat ratio (dimensionless)
\( R \) — Gas constant (J/(kg·K))
\( T \) — Temperature (K)

Explanation: The equation calculates the maximum possible flow rate through a nozzle or orifice when choked flow conditions are met.

3. Importance of Choked Flow Calculation

Details: Accurate choked flow calculation is essential for designing steam systems, safety valve sizing, process control systems, and ensuring proper operation of compressible fluid handling equipment.

4. Using the Calculator

Tips: Enter all values in SI units. Ensure upstream pressure, flow area, specific heat ratio, gas constant, and temperature are all positive values for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the significance of choked flow in steam systems?
A: Choked flow determines the maximum steam flow rate through valves and nozzles, which is crucial for system design and safety considerations.

Q2: What is the typical value of k for steam?
A: For superheated steam, k is approximately 1.3. For saturated steam, it's around 1.135.

Q3: When does choked flow occur?
A: Choked flow occurs when the pressure ratio (P2/P1) reaches a critical value, typically around 0.528 for air (k=1.4).

Q4: What are the limitations of this equation?
A: The equation assumes ideal gas behavior, isentropic flow, and negligible friction losses. Real-world applications may require correction factors.

Q5: How does temperature affect choked flow?
A: Higher temperatures generally decrease choked flow rates due to the inverse relationship with the square root of temperature in the equation.