An adiabatic pump of efficiency 40% is used to increase the water pressure from 200 kPa to 600 kPa. The flow rate of water is 600 L/min. The specific heat of water is 4.2 kJ/(kg·°C). Assuming water is incompressible with a density of 1000 kg/m³, the maximum temperature rise of water across the pump is ____ °C (rounded off to 3 decimal places).

Question

Accepted Answer

The correct answer is 0.139 to 0.145. GATE 2025 official key: 0.139 to 0.145°C. Ideal (reversible) work = ΔP/ρ = 400,000/1000 = 400 J/kg. Actual work = 400/0.4 = 1000 J/kg; the loss (1000−400=600 J/kg) appears as a temperature rise: ΔT = 600/4200 ≈ 0.143°C.