GATE ME 2018: Heat Transfer Rapid Revision Test for ESE & GATE ME Exams

Question 1

For a diffused body, emissivity is given as 0.5 and emissive power of the black body is given as 20W/m². Calculate the intensity of radiation of body? (in W/m²)

Question 2

Which of the following graph represent a counter-flow heat exchanger ?
1)

2)

3)

Question 3

The given plate has grashoff’s number equals to 7000,dynamic viscosity of 36 kg/ms, thermal conductivity of 52 W/mK and specific heat at constant pressure equals to 1 J/kgK. The flow is

Question 4

It is desired to increase the heat dissipation rate over the surface of an electronic device of spherical shape of 5 mm radius exposed to convection with h = 20 W/m²k by encasing it in a spherical sheath of conductivity 0.08 W/m-k. For maximum heat flow the diameter of the sheath will be

Question 5

Which of the following is a wrong statement?

Question 6

Heat is generated uniformly in a long solid cylindrical rod (diameter = 10mm) at the rate of

. The thermal conductivity of the rod material is 25W/m.K. Under steady state conditions, the temperature difference between the centre and the surface of the rod is _________ °C.

Question 7

A counterflow heat exchanger is used to heat water from 40 °C to 100 °C by using hot exhaust gas entering at 150 °C and leaving at 90 °C. the LMTD for the heat exchanger is

Question 8

Statement 1 : If oil used is dirty, it will reduce the overall heat transfer coefficient.
Statement 2 : The overall thermal resistance of heat exchanger increases due to fouling

Question 9

A body at 600 K cools by radiating heat to ambient atmosphere maintained at 300 K. When the body has cooled to 500 K, then the cooling rate as a percentage of original cooling rate is about

Question 10

A horizontal cylinder of 6m diameter is placed with surface temperature is 200⁰C and cooled by air of temperature 30⁰C. The given nusselt number is 25 and thermal conductivity is 51.8 W/m K . Calculate heat flux.(W/m²)

Question 11

A solid cylinder (surface 2) is located at the center of a hollow sphere (surface 1). The diameter of the sphere is 1m, while the cylinder has a diameter and length of 0.5m each. The radiation configuration factor F11 is

Question 12

A heat exchanger is used to heat cold water (C_p=4.18kJ/kg-K) entering at 12⁰C at a rate of 1.2 kg/s by hot air (C_p=1.005 kJ/kg-K) entering at 90⁰C at rate of 2.5 kg/s. The highest rate of heat transfer in the heat exchanger is

Question 13

Air (ρ= 1.2 kg/

and kinematic viscosity. v = 2 ×

/s) with a velocity of 2 m/s flows over the top surface of a flat plate of length 2.5 m. If the average value of friction coefficient is

,the total drag force (in N) per unit width of the plate is_______

Question 14

A sphere of mass 5.5 kg and initially at a temperature of 290 K is suddenly emerged in a liquid of 15 K and convective heat transfer coefficient is 58 W/m²K. Estimate the time(in minutes) required to cool the sphere to 95K and the given properties are
ρ = 2700kg/m³, C= 900J/kg and k=205W/m K r=4.5 mm

Question 15

Determine the ratio of C for a counter flow heat exchanger which has a mass of hot and cold fluids is 2 kg/s and 0.5 kg/s. The specific heat of hot fluid is 1.045 kJ/kg℃and cold fluid is 4.18 kJ/kg℃.