THERMAL ENGINEERING -2
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Transcript of THERMAL ENGINEERING -2
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NAME :- Pamara alpesh M.
ENROLLMENT NO :- 146018319004
SUB TOPIC :- Psychrometer
GUIDANCE BY :- Arpit SIR
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On Topic : :- Psychrometer
SUB :THERMAL ENGNEERIG-3
PREPARED BY
GUIDE : ARAPIT SIR Parmar Alpesh M.
146018319004
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Signature of Guide: Signature of Principal: Signature of HOD:
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Sling Psychrometer• consists of two thermometers
mounted together with a handle attached on a chain
• a psychrometer so designed that the wet-bulb thermometer can be ventilated, to expedite evaporation, by whirling in the air.
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Sling Psychrometer
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A Sling Psychrometer A Sling Psychrometer is used to measure is used to measure relative humidity.relative humidity.
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Psychrometer Parts:Psychrometer Parts:
•Dry Bulb ThermometerDry Bulb Thermometer
•Wet Bulb ThermometerWet Bulb Thermometer
•Reservoir and StockingReservoir and Stocking WETWETDRYDRY
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Uses
• The Sling Psychrometer measures the humidity of the air.
• Measures the amount of water vapor in the air• Estimates the dew point
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As the wet-bulb thermometer goes through the airAs the wet-bulb thermometer goes through the air
1. Water evaporates1. Water evaporates
2. Energy is used; water changes from liquid 2. Energy is used; water changes from liquid to vaporto vapor
3. Wet-bulb temperature goes down3. Wet-bulb temperature goes down
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What influences how What influences how much the wet-bulb much the wet-bulb temperature goes temperature goes down?down?
HumidityHumidity
TemperatureTemperature
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Using our wet- and Using our wet- and dry-bulb temperatures, dry-bulb temperatures, we can consult tables we can consult tables made by scientists…made by scientists…
……to determine to determine humidityhumidity and and saturation valuesaturation value..
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On the side of the psychrometer is On the side of the psychrometer is a sliding scale which calculates a sliding scale which calculates
relative humidity for us.relative humidity for us.
Align the dry-bulb reading with the Align the dry-bulb reading with the wet-bulb reading. The arrow will point wet-bulb reading. The arrow will point to the relative humidity reading on the to the relative humidity reading on the center scale. It’s easy!center scale. It’s easy!
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Dew Point and
Relative HumidityUsing a Sling Psychrometer
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Sling Psychrometer• A double thermometer
– One is ‘normal’ = dry bulb– One is covered with a wet piece
of cloth = wet bulb• When water evaporates, it
removes heat.• Therefore, the wet bulb will
always record a lower temperature than the dry bulb.
Dry Bulb
Wet Bulb
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Using the psychrometer
• Wet the cloth at the end of one of the apparatus.
• Carefully (!), gently (!), etc spin the psychrometer around for a few minutes.
• Record the temperature of the dry bulb and the wet bulb in °C
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Calculating Dew Point
• Subtract the wet bulb temperature from the dry bulb temperature and record this value.– You should now have 3 values recorded:
• Dry bulb ____ °C• Wet bulb ____ °C• Difference ____ °C
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Calculating Dew Point, cont.
• Open your ESRT to page 12.• Locate the dry bulb temperature on the vertical
(left) axis of the Dew Point Temperature Chart.
• Locate the difference between the wet and dry bulb temperature on the horizontal (top) of the chart.
• Locate where the two values intersect: this is the dew point.
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Calculating Relative Humidity (%)
• Record and calculate the same three values as you did for dew point:– Dry bulb temp ___ °C– Wet bulb temp ___ °C– Difference ___ °C
• Use the Relative Humidity chart on pg. 12 of your ESRT as you did for dew point.
• The relative humidity is at the intersection of the dry bulb temperature and the difference values.