PSYCHOMETER

1. NAME :- Pamara alpesh M.
ENROLLMENT NO :- 146018319004
SUB TOPIC :- Psychrometer
GUIDANCE BY :- Arpit SIR

2. On Topic : :- PsychrometerOn Topic : :- Psychrometer
SUB :THERMAL ENGNEERIG-3SUB :THERMAL ENGNEERIG-3 PREPARED BY
GUIDE : ARAPIT SIRGUIDE : ARAPIT SIR
Parmar Alpesh M.
146018319004

3. Signature of Guide: Signature of Principal: Signature of HOD:

4. 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.

5. Sling Psychrometer

6. 6
A Sling PsychrometerA Sling Psychrometer
is used to measureis used to measure
relative humidity.relative humidity.

7. 7
Psychrometer Parts:Psychrometer Parts:
•Dry Bulb ThermometerDry Bulb Thermometer
•Wet Bulb ThermometerWet Bulb Thermometer
•Reservoir and StockingReservoir and Stocking
WETWETDRYDRY

8. Uses
• The Sling Psychrometer measures the humidity of the
air.
• Measures the amount of water vapor in the air
• Estimates the dew point

9. 9
As the wet-bulb thermometer goes through theAs the wet-bulb thermometer goes through the
airair
1. Water evaporates1. Water evaporates
2. Energy is used; water changes from liquid2. Energy is used; water changes from liquid
to vaporto vapor
3. Wet-bulb temperature goes down3. Wet-bulb temperature goes down

10. 10
What influences howWhat influences how
much the wet-bulbmuch the wet-bulb
temperature goestemperature goes
down?down?
HumidityHumidity
TemperatureTemperature

11. 11

12. 12
Using our wet- andUsing our wet- and
dry-bulb temperatures,dry-bulb temperatures,
we can consult tableswe can consult tables
made by scientists…made by scientists…
……to determineto determine humidityhumidity andand saturation valuesaturation value..

13. 13
On the side of the psychrometer isOn the side of the psychrometer is
a sliding scale which calculatesa sliding scale which calculates
relative humidity for us.relative humidity for us.
Align the dry-bulb reading with theAlign the dry-bulb reading with the
wet-bulb reading. The arrow will pointwet-bulb reading. The arrow will point
to the relative humidity reading on theto the relative humidity reading on the
center scale. It’s easy!center scale. It’s easy!

14. Dew Point
and
Relative Humidity
Using a Sling Psychrometer

15. 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

16. 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

17. 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

18. 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.

19. 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.