During heating and humidification, the final relative humidity of air

The sensible heat factor during the heating and humidification process is given by (where h₁ = Enthalpy of air entering the heating coil, h₂ = Enthalpy of air leaving the heating coil and h_A = Enthalpy of air at the end of humidification process)

A

$$\frac{{{{\text{h}}_{\text{A}}} - {{\text{h}}_2}}}{{{{\text{h}}_1} - {{\text{h}}_2}}}$$

B

$$\frac{{{{\text{h}}_2} - {{\text{h}}_{\text{A}}}}}{{{{\text{h}}_1} - {{\text{h}}_2}}}$$

C

$$\frac{{{{\text{h}}_1} - {{\text{h}}_2}}}{{{{\text{h}}_{\text{A}}} - {{\text{h}}_2}}}$$

D

$$\frac{{{{\text{h}}_{\text{A}}} - {{\text{h}}_1}}}{{{{\text{h}}_2} - {{\text{h}}_1}}}$$

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

High relative humidity decreases the evaporative process and as the temperature is increased, the relative humidity decreases. The comfort range for human body is the ambient temperature of 22 to 27°C with relative humidity ranging from __________ percent.

A

5 to 10

B

15 to 25

C

45 to 50

D

75 to 80

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

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

Humidity chart is useful for the solution of problems concerning condensation, vaporisation and air conditioning. At a given dry bulb temperature, value of humidity obtained from the humidity chart directly, is in terms of __________ humidity.

A

Molal

B

Relative

C

Percentage

D

None of these

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 specific humidity during heating and humidification process.

A

Remains constant

B

Increases

C

Decreases

D

None of these

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

The percentage humidity is less than the relative humidity only at __________ percent humidity.

A

Zero

B

Hundred

C

Both zero and hundred

D

None of these

Statement 1: When there is an equilibrium between the vapor pressure and the percentage relative humidity, water activity is directly proportional to the percentage relative humidity. Statement 2: Even a water activity as high as 0.85 for food items is considered to be very dry for substances.

A

True, False

B

True, True

C

False, False

D

False, True

During heating and humidification, the final relative humidity of air

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