Saturated steam at 100°C condenses on the outside of a

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Saturated steam at 100°C condenses on the outside of a tube. Cold enters the tube at 20°C and exits at 50°C. The value of the Log Mean Temperature Difference (LMTD) is ______°C.

1. 613.83 °C
2. 63.83 °C
3. 638.3 °C
4. 1163.83 °C

Correct Option: B

Here T_ci → cold fluid which enters the tube (temperature)
T_co → cold fluid which exits at tube (temperature)
θ₁ = T_hi – T_ci = 100 – 20 = 80 °C
θ₂ = T_ho – T_co = 100 – 50 = 50 °C

θ_im =	θ₁ - θ₂
	ln	θ₁
		θ₂

θ_im =	80° - 50°		= 63.83 °C
	ln	80
		50