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
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OA=Sensible heating moving horizontally towards right of the point.
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OB= Sensible cooling moving horizontally towards left of the point.
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OC =Humidification moving vertically upwards of the point
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OD =Dehumidification moving vertically downwards of the point
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OE =Heating and humidification
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OF =Cooling and dehumidification
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OG =Cooling and humidification
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OH = Heating and dehumidification
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Psychrometry deals with
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Dry air
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Moist air
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Both dry & moist air
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None
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ANS: (b)
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Dry bulb temperature is given by
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Bulb of an ordinary thermometer
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Wet bulb of a psychrometer
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Can’t say
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None
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ANS: (a)
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Wet bulb temperature is given by
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Bulb of an ordinary thermometer
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Wet bulb of a psychrometer
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Can’t say
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None
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ANS: (b)
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Dew point temperature is that temperature at which
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Water droplet start coming on sensible cooling of air
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Water droplet start adding into the air on sensible heating
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Can’t say
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None
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ANS: (a)
5. Relative humidity is the ratio of
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Firstly Moisture in a given volume of air/Moisture in the same volume when saturated at the same temperature
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Secondly Moisture in a given volume when saturated / Moisture in a given volume of air at the same temperature
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Thirdly Moisture in a given mass of air/Moisture in the same mass when saturated at the same temperature
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None
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ANS: (a)
6. Humidity ratio is the ratio of
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Firstly Moisture in a given volume of air/Moisture in the same volume when saturated at the same temperature
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Secondly Moisture in a given volume when saturated /Moisture in a given volume of air at the same temperature
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Thirdly Moisture in a given mass of air/Moisture in the same mass when saturated at the same temperature
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None
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ANS: ©
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Specific volume of air means
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Volume per kg of dry air
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Volume per kg of moist air
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Can’t say
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None
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ANS: (a)
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Specific enthalpy of air at a certain temperature means
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Enthalpy of dry air
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Enthalpy of 1 kg of dry air + enthalpy of moisture associated with 1 kg of dry air
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Both (a) & (b)
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None
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ANS: (b)
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Specific humidity means
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Mass of moisture in a certain volume of air
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Mass of moisture per kg of dry air
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Both (a) & (b)
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None
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ANS: (b)
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Sensible heating of air means
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Only rise of temperature
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Rise of temperature & moisture
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Can’t say
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None
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ANS: (a)
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Sensible cooling of air means
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Only decrease of temperature
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Decrease of temperature & moisture
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Can’t say
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None
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ANS: (a)
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Humidification means addition of
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Heat
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Moisture
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Heat and moisture
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None
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ANS: (b)
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Dehumidification means addition of
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Heat
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Moisture
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Heat and moisture
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None
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ANS: (d)
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Humidification means removal of
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Heat
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Moisture
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Heat and moisture
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None
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ANS: (b)
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Adiabatic saturation of air means addition of
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Heat at constant temperature
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Moisture at constant temperature
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Moisture at constant enthalpy
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None
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ANS: (c )
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Heating & humidification means addition of
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Latent heat & moisture
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Sensible heat
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Sensible heat & moisture
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None
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ANS: (c )
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Cooling & dehumidification means addition of
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Latent heat & moisture
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Sensible heat
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Sensible heat & moisture
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None
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ANS: (d )
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Cooling & dehumidification means removal of
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Latent heat & moisture
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Sensible heat
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Sensible heat & moisture
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None
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ANS: (c )
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For saturated air
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Firstly tdb > twb > tdp
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Secondly tdb < twb < tdp
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Thirdly tdb = twb = tdp
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None
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ANS: ©
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The equation of specific humidity is
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Firstly w = 0.622 pwv/(pt–pwv)
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Secondly w = 0.622 pwv/pt
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Thirdly w = 0.622 pwv/(pt+pwv)
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None
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ANS: (a)
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The equation of relative humidity is
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Firstly Ф = pv/pvs
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Secondly Ф = pt/pvs
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Thirdly Ф = pv/pt
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None
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ANS: (a)
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The equation for enthalpy of moist air is
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Firstly hma = 1 cp dt + w cpv (tdb -tdp)
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Secondly hma = 1 cp dt + w [h0 +cpv (tdb -tdp)]
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Thirdly hma = 1 cp dt + w [h0 +cpv (tdb –twb)]
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None
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ANS: (b)
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A Sling Psychrometer contains
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Dry bulb thermometer
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Wet b ulb thermometer
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Both (a) & (b)
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None
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ANS: (c )
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When two steams of moist air are mixing, the properties of the final steam are found by
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Enthalpy and Temperature balance
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Temperature and moisture balance
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Enthalpy and moisture balance
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None
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ANS: (c )
Q25. Specific humidity is on
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Vertical on extreme right
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Vertical on extreme left
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Both (a) & (b)
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None
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ANS: (a)
Q26. Sensible heat factor is on
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Vertical on extreme right
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Vertical on extreme left
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© Both (a) & (b)
(d)None
ANS: (a)
Q27. Dry bulb temperature is on
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Vertical axis
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Horizontal axis
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Both (a) & (b)
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None
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ANS: (b)
Q28. Wet bulb temperature is on 100 % R.H. curve where cuts a constant
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Pressure line
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Enthalpy line
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Dry bulb temperature line
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None
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ANS: (b)
Q29. Dew point temperature is on 100 % R.H. curve where cuts a
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Horizontal line from the given wet bulb temperature
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Horizontal line from the given dry bulb temperature
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Vertical line from the given specific humidity
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None
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ANS: (b)
Q30. Constant value of Relative Humidity is represented by
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Horizontal lines
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Vertical lines
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Curves
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None
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ANS: (c )
Q31. Relative humidity increases as we move from
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Left to right
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Right to left
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Both (a) & (b)
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None
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ANS: (b)
Q32. Constant enthalpy lines are slant parallel lines which pass through constant
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Dry bulb temperature meeting the 100 % R.H. curve
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Wet bulb temperature at 100 % R.H. curve
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Both (a) & (b)
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None
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ANS: (b)
Q33. Constant specific volume lines are
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Vertical lines
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Horizontal lines
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Curves
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None
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ANS: (c )
Q34. Specific volume increases as we move from
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Left to right
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Right to left
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Both (a) & (b)
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None
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ANS: (a)
Q35. Constant dry bulb temperature values are represented by
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Horizontal lines
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Vertical lines
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Curves
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None
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ANS: (b)
Q36. Constant wet bulb temperature values are represented by
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Horizontal lines
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Vertical lines
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Curves
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None
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ANS: (d)
Q37. Sensible heating on chart is represented by
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Horizontal line from right to left
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Horizontal line from left to right
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Vertical line
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None
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ANS: b)
Q38. Increase of specific humidity is as we move from
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Left to right
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Right to left
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Vertically upwards
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None
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ANS: ©
Q39. Increase in Sensible Heat Factor is as we move from
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Left to right
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Vertically upwards
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Vertically downwards
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None
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ANS: (c )
Q40. On chart, sensible cooling presented as we move from
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Left to right
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Right to left
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Vertically upwards
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None
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ANS: (b)
Q41. On chart, humidification presented by as we move from
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Right to left
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Left to right
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Vertically downwards
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None
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ANS: (d)
Q42. On chart, dehumidification presented by as we move from
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Right to left
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Left to right
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Vertically downwards
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None
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ANS: (c)
Q43. On chart, humidification and heating presented by as we move from
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Right to left
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Left to right
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Vertically downwards
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None
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ANS: (d)
Q44. Heating & Humidification on chart is represented by as we move in a slant direction from
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Right to left
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Left to right
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Vertically downwards
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None
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ANS: (b)
Q45. Cooling & Humidification on chart is represented by as we move in a slant direction from
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Right to left
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Left to right
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Vertically downwards
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None
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ANS: (a)
Q46. Cooling & Dehumidification on chart is represented by as we move in a slant direction from
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Right to left
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Left to right
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Vertically downwards
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None
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ANS: (a)
Q47. Heating & Dehumidification on chart is represented by as we move in a slant direction from
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Right to left
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Left to right
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Vertically downwards
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None
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ANS: (b)
Q48. On chart, adiabatic saturation presented by a constant
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R. H. curve
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Enthalpy line
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Specific humidity line
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None
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ANS: (b)
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