Consider the following statements: 1. The relative humidity of air does not change with temperature as long as specific humidity remains constant. 2. Dew-point temperature is the temperature at which condensation begins when air is cooled at constant volume. 3. Saturated air passing over a water surface does not cause change of air temperature. 4. For saturated air, dry-bulb, wet-bulb and dew-point temperatures are identical. Which of the above statements are correct?

Consider the following statements and choose the correct answer:
1. A direct proportionality exists between vapour pressure and the concentration of water vapour in the atmosphere
2. Relative humidity is an expression of the ratio of the actual vapour pressure of the atmosphere when saturated at the same temperature
3. A rise or fall in temperature with no change in vapour pressure will cause a drop or rise, respectively, in relative humidity
4. A rise or fall in vapour pressure with no change in temperature will be accompanied by a rise or fall, respectively, in relative humidity

A

1, 2, 3 and 4 are true

B

Only 3 and 4 are true

C

Only 2 and 4 are true

D

Only 1, 2 and 3 are true

Consider the following statements for the appropriate context: 1. The Relative Humidity of air remains constant during sensible heating or cooling 2. The Dew Point Temperature of air remains constant during sensible heating or cooling 3. The total enthalpy of air remains constant during adiabatic cooling 4. It is necessary to cool the air below its Dew Point Temperature for dehumidifying Which of the above statements are correct?

A

1, 2 and 3

B

1, 2 and 4

C

3 and 4 only

D

2, 3 and 4

Consider the following statements with regard to atmospheric humidity: 1. Absolute humidity is the amount of water vapour per unit volume. 2. Hygrometer is used to measure relative humidity. 3. Dew point is the temperature at which the relative humidity is 75%. Which of the above statements are correct?

A

1 and 2 only

B

1 and 3 only

C

2 and 3 only

D

1, 2 and 3

Consider the following statements (i) If a condensing liquid does not wet a surface, then drop wise condensation will not take place on it (ii) Drop wise condensation gives a higher transfer rate than film wise condensation (iii) Reynolds number of condensing liquid is based on its mass flow rate (iv) Suitable coating or vapor additive is used to promote film wise condensation Identify the correct statement

A

i and ii

B

ii, iii and iv

C

iv only

D

i, ii and iii

Consider the following statements for cooling towers: 1. Cooling tower is an artificial device used to cool the hot cooling water coming out of condenser more effectively. 2. The amount of water usually lost with induced draft cooling tower ranges from 5% to 6% by evaporation. 3. The amount of water usually lost with induced draft cooling tower ranges from 7% to 8% by drift losses. 4. The rate of evaporation of water and its cooling effect on the remaining water depends upon the relative humidity of air passing through the tower. Which of the above statements are correct?

A

1 and 4 only

B

1 and 3 only

C

2 and 3 only

D

1, 2, 3 and 4

Which are the correct statements? (a) Film condensation usually occur on oily surface. (b) Temperature of condensate gradually increases towards the liquid-vapour interface. (c) Suitable coating is used to promote dropwise condensation. (d) Dropwise condensation gives lower heat transfer rate than film condensation.

A

(a), (d)

B

(e), (d)

C

(a),(b)

D

(b), (c)

Consider the following statements: 1. There is no change in temperature when a liquid is being evaporated into vapour 2. Vapour is a mixed phase of liquid and gas in the zone between saturated liquid line and saturated vapour line 3. The saturated dry vapour curve is steeper as compared to saturated liquid curve on a T-s diagram 4. The enthalpy of vaporization decreases with increase in pressure Which of the above statements are correct?

A

1, 2 and 3 only

B

3 and 4 only

C

1, 2 and 4 only

D

1, 2, 3 and 4

Statement (I): Piston temperature profiles near full load are flattened in case of liquid cooled engines whereas for air cooled engines temperature profiles are steeper. Statement (II): The piston temperature profiles are different in nature for liquid cooled and air cooled engines because of the different values of heat capacities.

A

Both Statement I) and Statement II) are individually true and Statement II) is the correct explanation of Statement I)

B

Both Statement I) and Statement II) are individually true but Statement II) is not the correct explanation of Statement I)

C

Statement I) is true but Statement II) is false

D

Statement I) is false but Statement II) is true

The statement concern psychrometric chart. 1. Constant relative humidity lines are uphill straight lines to the right 2. Constant wet bulb temperature lines are downhill straight lines to the right. 3. Constant specific volume lines are downhill straight lines to the right. 4. Constant enthalpy lines are coincident with constant wet bulb temperature lines. Which of the statements are correct?

A

2 and 3

B

1 and 2

C

1 and 3

D

2 and 4

Consider an enclosure formed by three surfaces having the following values of shape factors, emissivities and temperatures Surface 1 i.e. curved cylindrical has an emissivity 0.75 and temperature 800 K Surface 2 i.e. closing disc has an emissivity 0.8 and temperature 700 K Surface 3 i.e. closing disc has an emissivity 0.8 and temperature 700 K The closing flat discs are 25 mm in diameter and they have interspacing distance equal to 100 mm. If the shape factor between these two identical discs is 0.05, calculate the net rate of radiant heat flow from the curve surface to each of the closing end surface

A

1.561 W

B

2.561 W

C

3.561 W

D

4.561 W

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