A control valve with hyperbolic characteristics has a turndown ratio (ratio of maximum flow to minimum controllable flow) of 50. The flow rate through the valve at 70% open is 5 m³ s⁻¹. Assuming constant fluid density and pressure drop across the valve, which one of the following is the flow rate (in m³ s⁻¹) through the valve at 30% open?

Question

Accepted Answer

The correct answer is B, 2.2. GATE 2026 official key: (B). For an equal-percentage (hyperbolic) valve, f(x) = R^(x−1); solving with turndown ratio 50 and the 70%-open flow of 5 m³/s gives ≈2.2 m³/s at 30% open.