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GATE Prev Year : Heat-Transfer Test-5

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Question 1

In the laminar flow of air (Pr = 0.7) over a heated plate. if δ and δ_T denote, respectively, the hydrodynamic and thermal boundary layer thicknesses, then

Question 2

In a condenser of a power plant, the steam condenses at a temperature of 60 °C. The cooling water enters at 30 °C and leaves at 45 °C. The logarithmic mean temperature difference (LMTD) of the condenser is

Question 3

A stainless steel tub (k₈ = 19 W/mK) of 2 cm ID and 5 cm OD is insulated with 3 cm thick asbestos (k_a = 0.2 W/mK). If the temperature difference between the innermost and outermost surfaces is 600⁰C, the heat transfer rate per unit length is

Question 4

A fin has 5mm diameter and 100mm length. The thermal conductivity of fin material is 400Wm⁻¹K⁻¹. One end of the fin is maintained at 130 ºC and its remaining surface is exposed to ambient air at 30 ºC. if the convective heat transfer coefficient is 40Wm^-2K^-1, the heat loss (in W) from the fin is

Question 5

In a condenser, water enters a 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/kg K. If the overall heat transfer coefficient is 2000 W/m² K, the heat transfer area is _______.

Question 6

A small copper ball of 5 mm diameter at 500 K is dropped into an oil bath whose temperature is 300 K. the thermal conductivity of copper is 400 W/m.K, its density 9000 kg/m³ and its specific heat 385 J/kg.K. if the heat transfer coefficient is 250 W/ m².K and lumped analysis is assumed to be valid, the rate of fall of the temperature of the ball at the beginning of cooling will be, in K/s,

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ESE & GATE ME Heat Transfer

Jul 16ESE & GATE ME