The average heat transfer co-efficient on a thin hot vertical plate suspended in still air can be determined from observations of the change in plate temperature with time as it cools. Assume the plate temperature to be uniform at any instant of time and radiation heat exchange with the surroundings negligible. The ambient temperature is 25°C, the plate has a total surface area of 0.1 m2 and a mass of 4 kg. The specific heat of the plate material is 2.5 kJ/kgK. The convective heat transfer co-efficient in W/m2K, at the instant when the plate temperature is 225°C and the change in plate temperature with lime dT/dt = -0.02 K/s, is

1.  200

2.  20

3.  15

4.  10

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4
Correct Answer :

200


Explanation :
No Explanation available for this question

A 200 x 100 x 50 mm steel block is subjected to a hydrostatic pressure of 15 MPa.The Young’s modulus and Poisson's ratio of the material are 200 GPa and 0.3 respectively.The change in the volume of the block in mm-1 is

1.  85

2.  90

3.  100

4.  110

View Answer  
4
Correct Answer :

90


Explanation :
No Explanation available for this question

A model of a hydraulic turbine is tested at a head of 1/4th  of that under which the full scale turbine works. The diameter of the model is half of that of the full scale turbine. If N is the RPM of the full scale turbine, then the RPM of the model will be

1.  N/4

2.  N/2

3.  N

4.  2N

View Answer  
4
Correct Answer :

N


Explanation :
No Explanation available for this question

A stepped steel shaft shown below is subjected to 10 Nm torque. If the modulus of rigidity is 80 GPa, the strain energy in the shaft in N mm is

1.  4.12

2.  3.46

3.  1.73

4.  0.86

View Answer  
4
Correct Answer :

1.73


Explanation :
No Explanation available for this question

The stroke and bore of a four stroke spark ignition engine are 250 mm and 200 mm respectively. The clearance volume is 0.001 m'. If the specific heat ratio γ= 1.4, the air-standard cycle efficiency of the engine is

1.  46.40%

2.  56.10%

3.  58.20%

4.  62.80%

View Answer  
4
Correct Answer :

58.20\%


Explanation :
No Explanation available for this question

A thin spherical pressure vessel of 200 mm diameter and 1 mm thickness is subjected to an internal pressure varying from 4 to 8 MPa. Assume that the yield, ultimate, and endurance strength of material are 600, 800 and 400 MPa respectively. The factor of safety as per Goodman's relation is

1.  2.0

2.  1.6

3.  1.4

4.  1.2

View Answer  
4
Correct Answer :

1.4


Explanation :
No Explanation available for this question

A building has to be maintained at 21° C (dry bulb) and 14.5° C (wet bulb). The dew point temperature under these conditions is I0.17°C The outside temperature is -23° C (dry bulb) and the internal and external surface heat transfer coefficients are 8 W/m2 K and 23 W/m3 K respectively. If the building wall has a thermal conductivity of 1.2 W/mK, the minimum thickness (in m) of the wall required to prevent condensation is

1.  0.471

2.  0.407

3.   0.321

4.  0.125

View Answer  
4
Correct Answer :

0.407


Explanation :
No Explanation available for this question

A natural feed journal bearing of diameter 50 mm and length 50 mm operating at 20 revolution/ second carries a load of 2.0 kN. The lubricant used has a viscosity of 20 mPa s. The radial clearance is 50 nm. The Sommerfeld number for the

1.  0.062

2.  0.125

3.  0.250

4.  0.785

View Answer  
4
Correct Answer :

0.250


Explanation :
No Explanation available for this question

Atmospheric air at a flow rate of 3 kg/s (on dry basis) enters a cooling and dehumidifying coil with an enthalpy of 85 kj/kg of dry air and a humidity ratio of 19 grams/kg of dry air. The air leaves the coil with an enthalpy of 43 kj/kg of dry air and a humidity ratio of 8 grams/kg of dry air. If the condensate water leaves the coil with an enthalpy of 67 kj/kg, the required cooling capacity of the coil in kW is

1.  75.0

2.  123.8

3.    128.2

4.  159.0

View Answer  
4
Correct Answer :

123.8


Explanation :
No Explanation available for this question

A heat transformer is a device that transfers a part of the heat, supplied to it at an intermediate temperature, to a high temperature reservoir while rejecting the remaining part to a low temperature heat sink. In such a heat transformer, 100 kj of heatis supplied at 350 K. The maximum amount of heal in kj that can be transferred lo400 K, when the rest is rejected to a heal sink at 300 K is

1.  1250

2.  14.29

3.  33.33

4.  57.14

View Answer  
4
Correct Answer :

57.14


Explanation :
No Explanation available for this question
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