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 $$\mu $$ = Degree of saturation)

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

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

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

A

0.048

B

0.079

C

0.122

D

0.152

It is desired to condition the outside air from 70% relative humidity and 45°C dry bulb temperature to 50% relative humidity and 25°C dry bulb temperature (room condition). The practical arrangement will be

A

Dehumidification

B

Cooling and humidification

C

Cooling and dehumidification

D

Dehumidification and pure sensible cooling

According to Dalton's law of partial pressures, (where pb = Barometric pressure, pa = Partial pressure of dry air and pv = Partial pressure of water vapour)

A

Pb = pa - pv

B

Pb = pa + pv

C

Pb = pa × pv

D

$${\text{Pb}} = \frac{{{\text{pa}}}}{{{\text{pv}}}}$$

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

The bypass factor, in case of sensible cooling of air, is given by (where td₁ = Dry bulb temperature of air entering the cooling coil, td₂ = Dry bulb temperature of air leaving the cooling coil and td₃ = Dry bulb temperature of the cooling coil)

A

$$\frac{{{\text{t}}{{\text{d}}_1} - {\text{t}}{{\text{d}}_3}}}{{{\text{t}}{{\text{d}}_2} - {\text{t}}{{\text{d}}_3}}}$$

B

$$\frac{{{\text{t}}{{\text{d}}_2} - {\text{t}}{{\text{d}}_3}}}{{{\text{t}}{{\text{d}}_1} - {\text{t}}{{\text{d}}_3}}}$$

C

$$\frac{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_1}}}{{{\text{t}}{{\text{d}}_2} - {\text{t}}{{\text{d}}_3}}}$$

D

$$\frac{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_2}}}{{{\text{t}}{{\text{d}}_1} - {\text{t}}{{\text{d}}_3}}}$$

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

$$\frac{{{\text{t}}{{\text{d}}_2} - {\text{t}}{{\text{d}}_3}}}{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_1}}}$$

B

$$\frac{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_2}}}{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_1}}}$$

C

$$\frac{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_1}}}{{{\text{t}}{{\text{d}}_2} - {\text{t}}{{\text{d}}_3}}}$$

D

$$\frac{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_1}}}{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_2}}}$$

The rear window of an automobile is made of thick glass i.e. AB = 5 mm and thermal conductivity is 0.8 W/m degree. To defrost this window, a thin transparent film type heating element has been fixed to its inner surface. For the conditions given below, determine the electric power that must be provided per unit area of window if a temperature 5 degree Celsius is maintained at its outer surface. Interior air temperature and the corresponding surface coefficient are 20 degree Celsius and 12 W/m2 degree. Surrounding air temperature and the corresponding surface coefficient are – 15 degree Celsius and 70 W/m2 degree. Electric heater provides uniform heat flux

A

232.5 /m2

B

1232.5 /m2

C

2232.5 /m2

D

3232.5 /m2

At equilibrium the concentration of water in vapour phase (C^*) in kg/m³ of air space and the amount of water (m) adsorbed per kg of dry silica gel are related by, C^* = 0.0667 m. To maintain dry conditions in a room of air space 100 m³ containing 2.2 kg of water vapour initially, 10 kg of dry silica gel is kept in the room. The fraction of initial water remaining in the air space after a long time (during which the temperature is maintained constant) is

A

0.0

B

0.2

C

0.4

D

1.0

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)

Related Questions