Heat Transfer

181. If all the conditions and dimensions are same, then the ratio of velocity through the tubes of a double pass heat exchanger to that through the single pass heat exchanger is

1. 1
2. 2
3. 43862
4. 4

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182. If average heat transfer co-efficient is h_a and the local coefficient at the end of the plate is hl then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length

1. h_a = hl
2. h_a = 2hl
3. h_a = 0.5 hl
4. h_a = 0.75 hl

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183. If h₁ = inner film co-efficient and /h₂ = outer film co-efficient, then the overall heat transfer co-efficient is

1. Always less than h₁
2. Always between h₁ and h₂
3. Always higher than h₂
4. Dependent on metal resistance

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184. If heat transfer rate varies with the time, it is termed as

1. Forced convection
2. Steady state conduction
3. Monochromatic radiation
4. None of these

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185. If Prandtl number is greater than the Schmidt number, then the

1. Thermal boundary layer lies inside the concentration boundary layer
2. Concentration boundary layer lies inside the thermal boundary layer
3. Thermal & concentration boundary layers are of equal thickness
4. Hydrodynamic (i.e., momentum) boundary layer is thicker than the other two

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186. If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid

1. Remains unchanged
2. Increases
3. Increases or decreases depending on number of shell passes
4. Decreases

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187. If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows _________ law.

1. Parabolic
2. Hyperbolic
3. Linear
4. Logarithmic

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188. In a 1^-1 concurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is

1. ∞
2. 0
3. Equal to the difference between hot and cold fluids inlet temperature
4. Equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature

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189. In a backward feed multiple effect evaporator

1. Feed is introduced in the first effect
2. Feed flows from low pressure to high pressure
3. No pumps are required between successive effects
4. None of these

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190. In a boiling curve, the peak heat flux is called the _________ point.

1. Nusselt
2. Leidenfrost
3. Boiling
4. Burnout

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