GATE XL concept:heat-transfer PYQs & Answers

Questions 1–7 of 7. Imported answers require independent review unless marked reviewed.

For a given temperature difference between the top and bottom surfaces of a flat metal plate, Fourier’s law of heat conduction implies that

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temperature gradient increases with increase in heat transfer area

heat flux is proportional to the thermal conductivity of the metal

heat flux increases with increase in thickness of the metal plate

temperature gradient decreases with increase in thickness of the metal plate

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Hot oil is being cooled in a countercurrent, double-pipe heat exchanger from 410 K to 340 K by chilled water entering at 290 K and exiting the exchanger at 330 K. The Log Mean Temperature Difference (LMTD) for this heat transfer is _______K. (Round off to one decimal place)

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In a dairy plant, spray drying technology is used to produce whey powder. The rate of spray drying depends on

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Temperature of the incoming air

Shape of the cyclone separator

Diameter of the whey droplet

Heat transfer coefficient of hot air

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Which among the following expresion(s) is/are correct?

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Reynolds number =

Nuselt number =

Schmidt number =

Biot number =

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An orange juice flowing at 0.80 kg s

enters a counter current double pipe heat exchanger at 20 °C and leaves at 72 °C. Inlet and outlet temperatures of the hot water used as heating medium in the exchanger are 81 °C and 74 °C, respectively. The specific heat of the orange juice is 3.74 kJ kg

and overall heat transfer coefficient is 492 W m

. The heat transfer surface area (round off to 2 decimal places) will be ______ m

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Freezing of 100 mm spherical meat ball with 60% moisture at 35 °C is being done in an air blast freezer maintained at -45 °C. Given, latent heat of fusion for water is 333.2 kJ kg⁻¹, thermal conductivity of meat is 1.5 W m⁻¹ °C⁻¹, convective heat transfer coefficient is 40 W m⁻² °C⁻¹, density of frozen meat is 980 kg m⁻³ and initial freezing temperature of meat ball is -10 °C. Using Plank’s equation, freezing time (h) is ____________ (round off to 2 decimal places).

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The rate of heat transfer per unit area from a metal plate is 1000 W m⁻². The surface temperature of the plate is 120°C and ambient temperature is 20°C. The convective heat transfer coefficient (W m⁻² °C⁻¹) using the Newton’s law of cooling will be ______.

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GATE XL concept:heat-transfer PYQs

How to practice concept:heat-transfer

Question 118

Question 122

Question 108

Question 120

Question 20

Question 20

Question 20