GATE ME 2026 Set 1 — Question 55
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Heat Transfer → Conduction → LMTD Method
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Question
Convective heat transfer coefficients for Fluid 1 and Fluid 2 in a heat exchanger, as shown in the figure below, are and , respectively. The inner tube is made of a material which has a thermal conductivity for the given range of temperatures in the heat exchanger. The length of the heat exchanging surface, the inside radius of the inner tube, and thickness of the inner tube are , , and , respectively. Considering no heat exchange between the outer tube and the surrounding, the heat transfer rate for the heat exchanger is ________ W (rounded off to 1 decimal place).
Correct answer
49.5 to 51.5
Solution
1.Identify the heat exchanger type: From the figure, Fluid 1 (hot) enters at and exits at . Fluid 2 (cold) enters at and exits at . The flows are in opposite directions, so it is a counter-flow heat exchanger.
2.Calculate the Log Mean Temperature Difference (LMTD):
3.Calculate the total thermal resistance ():
Inner radius Outer radius
Length
Thermal conductivity
Convective coefficients: (Fluid 2), (Fluid 1)
4.Calculate the heat transfer rate ():
Rounding to 1 decimal place, we get .Continue learning with Success Tracker
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