An air-water vapour mixture has a dry bulb temperature of 60°C and a dew point temperature of 40°C. The total pressure is 101.3 kPa and the vapour pressure of water at 40°C and 60°C are 7.30 kPa and 19.91 kPa respectively.The humidity of air sample expressed as kg of water vapour/kg of dry air is

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?

A

1 and 2

B

2 and 3

C

1 and 4

D

3 and 4

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

Suppose saturated polar air has an air temperature and dew point of -10o C, and unsaturated desert air has an air temperature of 35o C and a dew point of 10o C. The desert air contains ______ water vapour and has a ________ relative humidity than the polar air.

A

More, lower

B

More, higher

C

Less, lower

D

Less, higher

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

Relative humidity is given by (where pv = Partial pressure of water vapour, pb = Barometric pressure, ps = Pressure of saturated air, pd = Pressure at dry bulb temperature, pw = Saturation pressure corresponding to wet bulb temperature, and μ = Degree of saturation)

A

0.622 Pv / (Pb - Pv)

B

μ/[1 - (1 - μ) (Ps/Pb)]

C

[Pv (Pb - Pd)]/ [Pd (Pb - Pv)]

D

None of these

Relative humidity is given by (where p_v = Partial pressure of water vapour, p_b = Barometric pressure, p_s = Pressure of saturated air, p_d = Pressure at dry bulb temperature, p_w = Saturation pressure corresponding to wet bulb temperature and $$\mu $$ = Degree of saturation)

A

$$\frac{{0.622{{\text{p}}_{\text{v}}}}}{{{{\text{p}}_{\text{b}}} - {{\text{p}}_{\text{V}}}}}$$

B

$$\frac{\mu }{{1 - \left( {1 - \mu } \right)\frac{{{{\text{p}}_{\text{s}}}}}{{{{\text{p}}_{\text{b}}}}}}}$$

C

$$\frac{{{{\text{p}}_{\text{v}}}\left( {{{\text{p}}_{\text{b}}} - {{\text{p}}_{\text{d}}}} \right)}}{{{{\text{p}}_{\text{d}}}\left( {{{\text{p}}_{\text{b}}} - {{\text{p}}_{\text{v}}}} \right)}}$$

D

None of these

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

How far is point 'R' from Point 'T'? Statement (I): Point 'R' is 5 metres to the north of point 'M'. Point 'U' is 4 metres to the east of point 'R'. Point 'T' is to the west of point 'R' such that points 'U' 'R' and 'T' form a straight line of metres. Statement (II): Point 'Z' is metres to the south of point 'T'. Point 'U' is metres to the east of point 'T'. Point 'M' is metres to the east of point 'Z'. Point 'R' is metres to the north of point 'M'. Point 'R' lies on the line formed by joining points 'T' and 'U'.

A

Statement (I) and (III) are independently sufficient to answer the question.

B

Statement (I) and (II) are together required to answer the question.

C

Statement (I) alone is sufficient to answer the question while statement (II) is not sufficient to answer the question.

D

Statement (II) alone is sufficient to answer (I) is not sufficient to answer the question.

The wet bulb temperature is lower in dry air than in wet air at the same temperature. A dry bulb thermometer registers a higher temperature than a wet bulb thermometer except at __________ percent relative humidity.

A

0

B

100

C

50

D

None of these

The bypass factor (B. P. F.) in case of sensible heating of air is (Where td₁ = Dry bulb temperature of air entering the heating coil, td₂ = Dry bulb temperature of air leaving the heating coil, and td₃ = Dry bulb temperature of heating coil)

A

(td₂ - td₃)/(td₃ - td₁)

B

(td₃ - td₂)/(td₃ - td₁)

C

(td₃ - td₁)/(td₂ - td₃)

D

(td₃ - td₁)/(td₃ - td₂)

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