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GATE ME 2020 Heat Transfer Rapid Mini Mock
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Question 1
A thin metal plate is exposed to solar radiation. The air and the surroundings are at 30 °C. The heat transfer coefficient by free convection from the upper surface of the plate is 17.4 W/m2K. The plate has an absorptivity of 0.9 at solar wavelength and an emissivity of 0.1 at the long wavelength. Neglecting any heat loss from the lower surface, determine the incident solar radiation intensity in kW/m2, if the measured equilibrium temperature of the plate is 50 °C. Stefan Boltzmann constant is 5.67×10-8 W/m2K4.
Question 2
The fouling factor in heat exchanger is defined as
Question 3
The copper fins having square cross sectional area (1mm x 1mm) of 15mm length are provided on a motor to carry 1.5 w of energy generated by this motor The temperature of the surface of casing of motor should not exceeds 1000c when surrounding temperature is 300c. Assume k(copper)=200w/m0c, h=15w/m2 0c and neglect heat loss from the tip of fin. Find the number of fins required
Question 4
A composite wall, having unit length normal to the plane of paper, is insulated at the top and bottom as shown in the figure. It is comprised of four different materials A, B, C and D.
The dimensions are: HA = HD = 3m, HB = HC = 1.5 m, L1 = L3 = 0.05m, L2 = 0.1 m
The thermal conductivity of the materials are: KA = KD = 50 W/m-K, KB = 10W/m-k, KC = 1 W/m-k.
The fluid temperatures and Heat-Transfer coefficients (see figure) are: T1 = 200 ºC, h1 = 50 W/m2-K, T2 = 25 ºC, h2 = 10 W/m2 –K.
Assuming one-dimensional conduction,
Determine the rate of Heat-Transfer through the wall.
The dimensions are: HA = HD = 3m, HB = HC = 1.5 m, L1 = L3 = 0.05m, L2 = 0.1 m
The thermal conductivity of the materials are: KA = KD = 50 W/m-K, KB = 10W/m-k, KC = 1 W/m-k.
The fluid temperatures and Heat-Transfer coefficients (see figure) are: T1 = 200 ºC, h1 = 50 W/m2-K, T2 = 25 ºC, h2 = 10 W/m2 –K.
Assuming one-dimensional conduction,
Determine the rate of Heat-Transfer through the wall.
Question 5
A copper tube of 20 mm outer diameter, 1 mm thickness and 20 m long (Thermal conductivity = 400 W/m-K) is carrying saturated steam at 150 C (Convective heat transfer coefficient = 150 W/m2-K). The tube is exposed to an ambient temperature of 27 C. The convective heat transfer coefficient of air is 5 W/m2-K. Glass wool is used for insulation (Thermal conductivity = 0.075 W/m-K). If the thickness of the insulation used is 5 mm higher than the critical thickness of insulation, calculate the rate of steam condensation in kg/hr-m (The enthalpy of condensation of steam = 2230 kJ/kg).
Question 6
Two fluids, A and B exchange heat in a counter flow heat exchanger. Fluid A enters at 4200C and has mass flow rate of 2 kg/s. fluid B enters at 200C and also has mass flow rate of 2 kg/s, effectiveness of heat exchanger is 75%. The exit temperature (0C) of fluid B is (specific heat of fluid A is 1 kJ/kg-K and that of fluid B is 4 kJ/kg-K)
Question 7
A solid copper ball of mass 0.5 kg when quenched in a water bath at 300C, cools from 5300C to 4300C in 10 seconds. What will be the temperature (0C) of the ball after the next 10 seconds?
Question 8
A 
flat plate is suspended in a room, and is subjected to air flow parallel to its surfaces along its 3m long side. The free stream temperature and velocity of air are 20 °C and 7m/s. The total drag force acting on the plate is measured to be 1.86 N. The average heat transfer coefficient for the plate is ___________ W/m2-K.
[The properties of air at 20 °C temperature and 1 atmospheric pressure are,
Prandtl number, Pr= 0.7309]
flat plate is suspended in a room, and is subjected to air flow parallel to its surfaces along its 3m long side. The free stream temperature and velocity of air are 20 °C and 7m/s. The total drag force acting on the plate is measured to be 1.86 N. The average heat transfer coefficient for the plate is ___________ W/m2-K. [The properties of air at 20 °C temperature and 1 atmospheric pressure are,
Prandtl number, Pr= 0.7309] Question 9
Emissivities of two large parallel plates maintained at 900 °C and 400 °C are 0.3 and 0.5 respectively. What is the net radiant heat exchanger per square meter for the plate ?
Question 10
Consider two infinitely long concentric cylinders with a diameter ratio D2/D1 = 5. The shape factor for the outer cylinder with itself is
Question 11
A metallic rod (k=32 W/m°C), 10 mm in diameter and 80 mm long, with an insulated end is to be used as spine. It is exposed to surrounding with a temperature of 80°C and a heat transfer coefficient 55 W/m2°C. The temperature at the base of fin is 100°C. the fin efficiency will be
Question 12
A chemical having specific heat capacity of 18.35kW/K enters a parallel flow heat exchanger at 120 ° C. The cooling water having specific heat capacity of 58.14kW/K enters at a temperature of 20 ° C. The heat transfer area is 10 m2 and the overall heat transfer coefficient is 1050 W/m2-K. The effectiveness of the heat exchanger is
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