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In a condenser, water enters at 30°C and flows at the rate 1500 kg/hr. The condensing steam is at a temperature of 120°C and cooling water leaves the condenser at 80°C. Specific heat of water is 4.187 kJ/kgK. If the overall heat transfer coefficient is 2000 W/m2 K, the heat transfer area is
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- 0.707 m2
- 7.07 m2
- 70.7 m2
- 141.4 m2
Correct Option: A
Here, θ1 = 120 – 30 = 90ºC
θ2 = 120 – 80 = 40ºC
Log mean temperature difference,
Q = mcpw ∆T
| 1500 × | × 4.187 × (50) × 103 | 3600 |
= 87.22 × 103 Joule/s
Again
Q = UAθm
or 87.22 × 103 = 2000 × A × 61.65
∴ A = 0.707 m2
