PSYCHROMETRY MULTIPLE CHOICE QUESTIONS (MCQ) WITH ANSWERS

PSYCHROMETRY MULTIPLE

CHOICE QUESTIONS

(MCQ) WITH ANSWERS

MCQ on psychrometry increases level of

understanding & clarity. Psychrometry

deals with the properties of moist air.

Psychrometric processes on

psychrometry chart help to reach

from the existing condition of air to

reach the design conditions. It is very

useful in air conditioning applications.

Fig. Psychrometric Chart ( AB, CD & EF =Constant Enthalpy Lines, GH, IJ & KL =Constant specific volume lines, Curves MP & QR are constant Relative Humidity Lines)

Fig. Psychrometric Processes on Psychrometric Chart

• OA=Sensible heating moving horizontally towards right of the point.

• OB= Sensible cooling moving horizontally towards left of the point.

• OC =Humidification moving vertically upwards of the point

• OD =Dehumidification moving vertically downwards of the point

• OE =Heating and humidification

• OF =Cooling and dehumidification

• OG =Cooling and humidification

• OH = Heating and dehumidification

 

1. Psychrometry deals with

   1. Dry air

   2. Moist air

   3. Both dry & moist air

   4. None

ANS: (b)

2. Dry bulb temperature is given by

   1. Bulb of an ordinary thermometer

   2. Wet bulb of a psychrometer

   3. Can’t say

   4. None

ANS: (a)

3. Wet bulb temperature is given by

   1. Bulb of an ordinary thermometer

   2. Wet bulb of a psychrometer

   3. Can’t say

   4. None

ANS: (b)

4. Dew point temperature is that temperature at which

   1. Water droplet start coming on sensible cooling of air

   2. Water droplet start adding into the air on sensible heating

   3. Can’t say

   4. None

ANS: (a)

         5. Relative humidity is the ratio of

1. 1. Firstly    Moisture in a given volume of air/Moisture in the same volume when saturated at the same temperature

   2. Secondly     Moisture in a given volume when saturated / Moisture in a given volume of air at the same temperature

   3. Thirdly     Moisture in a given mass of air/Moisture in the same mass when saturated at the same temperature

   4. None

ANS: (a)

      6. Humidity ratio is the ratio of

1. 1. Firstly    Moisture in a given volume of air/Moisture in the same volume when saturated at the same temperature

   2. Secondly     Moisture in a given volume when saturated /Moisture in a given volume of air at the same temperature

   3. Thirdly     Moisture in a given mass of air/Moisture in the same mass when saturated at the same temperature

   4. None

ANS: ©

7. Specific volume of air means

   1. Volume per kg of dry air

   2. Volume per kg of moist air

   3. Can’t say

   4. None

ANS: (a)

8. Specific enthalpy of air at a certain temperature means

   1. Enthalpy of dry air

   2. Enthalpy of 1 kg of dry air + enthalpy of moisture associated with 1 kg of dry air

   3. Both (a) & (b)

   4. None

ANS: (b)

9. Specific humidity means

   1. Mass of moisture in a certain volume of air

   2. Mass of moisture per kg of dry air

   3. Both (a) & (b)

   4. None

ANS: (b)

10. Sensible heating of air means

    1. Only rise of temperature

    2. Rise of temperature & moisture

    3. Can’t say

    4. None

ANS: (a)

11. Sensible cooling of air means

    1. Only decrease of temperature

    2. Decrease of temperature & moisture

    3. Can’t say

    4. None

ANS: (a)

12. Humidification means addition of

    1.  Heat

    2.  Moisture

    3. Heat and moisture

    4. None

ANS: (b)

13. Dehumidification means addition of

    1.  Heat

    2.  Moisture

    3. Heat and moisture

    4. None

ANS: (d)

14. Humidification means removal of

    1.  Heat

    2. Moisture

    3. Heat and moisture

    4. None

ANS: (b)

15. Adiabatic saturation of air means addition of

    1. Heat at constant temperature

    2. Moisture at constant temperature

    3.  Moisture at constant enthalpy

    4. None

ANS: (c )

16. Heating & humidification means addition of

    1.  Latent heat & moisture

    2.  Sensible heat

    3. Sensible heat & moisture

    4. None

ANS: (c )

17. Cooling & dehumidification means addition of

    1.  Latent heat & moisture

    2.  Sensible heat

    3. Sensible heat & moisture

    4. None

ANS: (d )

18. Cooling & dehumidification means removal of

    1.  Latent heat & moisture

    2.  Sensible heat

    3.  Sensible heat & moisture

    4. None

ANS: (c )

19. For saturated air

    1. Firstly          t_db > t_wb > t_dp

    2. Secondly      t_db < t_wb < t_dp

    3. Thirdly          t_db = t_wb = t_dp

    4. None

ANS: ©

20. The equation of specific humidity is

    1. Firstly         w = 0.622 p_wv/(p_t–p_wv)

    2. Secondly       w = 0.622 p_wv/p_t

    3. Thirdly            w = 0.622 p_wv/(p_t+p_wv)

    4. None

ANS: (a)

21. The equation of relative humidity is

    1. Firstly        Ф = p_v/p_vs

    2. Secondly    Ф = p_t/p_vs

    3. Thirdly        Ф = p_v/p_t

    4. None

ANS: (a)

22. The equation for enthalpy of moist air is

    1. Firstly        h_ma = 1 c_p dt + w c_pv (t_db -t_dp)

    2. Secondly    h_ma = 1 c_p dt + w [h₀ +c_pv (t_db -t_dp)]

    3. Thirdly        h_ma = 1 c_p dt + w [h₀ +c_pv (t_db –t_wb)]

    4. None

ANS: (b)

23. A Sling Psychrometer contains

    1. Dry bulb thermometer

    2. Wet b ulb thermometer

    3. Both (a) & (b)

    4. None

ANS: (c )

24. When two steams of moist air are mixing, the properties of the final steam are found by

    1. Enthalpy and Temperature balance

    2. Temperature and moisture balance

    3. Enthalpy and moisture balance

    4. None

ANS: (c )

Q25. Specific humidity is on

1. 1. Vertical on extreme right

   2. Vertical on extreme left

   3. Both (a) & (b)

   4. None

ANS: (a)

Q26. Sensible heat factor is on

1. 1. Vertical on extreme right

   2. Vertical on extreme left

             © Both (a) & (b)

             (d)None

ANS: (a)

Q27. Dry bulb temperature is on

1. 1. Vertical axis

   2. Horizontal axis

   3. Both (a) & (b)

   4. None

ANS: (b)

Q28. Wet bulb temperature is on 100 % R.H. curve where cuts a constant

1. 1.  Pressure line

   2. Enthalpy line

   3.  Dry bulb temperature line

   4. None

ANS: (b)

Q29. Dew point temperature is on 100 % R.H. curve where cuts a

1. 1. Horizontal line from the given wet bulb temperature

   2. Horizontal line from the given dry bulb temperature

   3. Vertical line from the given specific humidity

   4. None

ANS: (b)

Q30. Constant value of Relative Humidity is represented by

1. 1. Horizontal lines

   2. Vertical lines

   3. Curves

   4. None

ANS: (c )

Q31. Relative humidity increases as we move from

1. 1. Left to right

   2. Right to left

   3. Both (a) & (b)

   4. None

ANS: (b)

Q32. Constant enthalpy lines are slant parallel lines which pass through constant

1. 1.  Dry bulb temperature meeting the 100 % R.H. curve

   2. Wet bulb temperature at 100 % R.H. curve

   3. Both (a) & (b)

   4. None

ANS: (b)

Q33. Constant specific volume lines are

1. 1. Vertical lines

   2. Horizontal lines

   3. Curves

   4. None

ANS: (c )

Q34. Specific volume increases as we move from

1. 1. Left to right

   2. Right to left

   3. Both (a) & (b)

   4. None

ANS: (a)

Q35. Constant dry bulb temperature values are represented by

1. 1. Horizontal lines

   2. Vertical lines

   3. Curves

   4. None

ANS: (b)

Q36. Constant wet bulb temperature values are represented by

1. 1. Horizontal lines

   2. Vertical lines

   3. Curves

   4. None

ANS: (d)

Q37. Sensible heating on chart is represented by

1. 1. Horizontal line from right to left

   2. Horizontal line from left to right

   3. Vertical line

   4. None

ANS: b)

Q38. Increase of specific humidity is as we move from

1. 1. Left to right

   2. Right to left

   3. Vertically upwards

   4. None

ANS: ©

Q39. Increase in Sensible Heat Factor is as we move from

1. 1. Left to right

   2. Vertically upwards

   3. Vertically downwards

   4. None

ANS: (c )

Q40. On chart, sensible cooling presented as we move from

1. 1. Left to right

   2. Right to left

   3. Vertically upwards

   4. None

ANS: (b)

Q41. On chart, humidification presented by as we move from

1. 1. Right to left

   2. Left to right

   3. Vertically downwards

   4. None

ANS: (d)

    Q42. On chart, dehumidification presented by as we move from

1. 1. Right to left

   2. Left to right

   3. Vertically downwards

   4. None

ANS: (c)

    Q43. On chart, humidification and heating presented by as we move from

• 1. Right to left

  2. Left to right

  3. Vertically downwards

  4. None

ANS: (d)

Q44.  Heating & Humidification on chart is represented by as we move in a slant direction from

1. 1. Right to left

   2. Left to right

   3. Vertically downwards

   4. None

ANS: (b)

    Q45. Cooling & Humidification on chart is represented by as we move in a slant direction from

1. 1. Right to left

   2. Left to right

   3. Vertically downwards

   4. None

ANS: (a)

    Q46. Cooling & Dehumidification on chart is represented by as we move in a slant direction from

1. 1. Right to left

   2. Left to right

   3. Vertically downwards

   4. None

ANS: (a)

    Q47. Heating & Dehumidification on chart is represented by as we move in a slant direction from

1. 1. Right to left

   2. Left to right

   3. Vertically downwards

   4. None

ANS: (b)

    Q48. On chart, adiabatic saturation presented by a constant

1. 1.  R. H. curve

   2.  Enthalpy line

   3.  Specific humidity line

   4. None

ANS: (b)

 

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