Learning Psychrometrics and Sensors measuring T and RH

1
Learning Psychrometrics and Sensors measuring T
and RH

• ??
• ???????

Wei Fang, Ph.D., Professor Dept. of
Bio-Industrial Mechatronics Engineering,
National Taiwan University
2
Analog Dry Bulb Temperature sensor
3
Analog Dry and Wet Bulb Temperature
4
Digital Dry Bulb Temperature reader
5
Infra-red Dry Bulb Temperature
6
Thermal Imager
http//www.landinst.com/infrared/products/thermal_
imaging/tp8_portable_imager.htm
http//us.fluke.com/usen/products/CategoryTI/
http//www.landinst.com/infrared/products/thermal_
imaging/guide_M4_thermal_imager.htm
7
(No Transcript)
8
Sensing element
9
Dry and wet Bulb Temperature sensors in Weather
station and greenhouse
10
RH f(Tdb, Twb)
Patm 101.325 kPa
11
Tdb and RH Sensors
12
Tdb and RH data logger
13
Day/Night trends of T and RH
14
High T coexist with Low Hum.
15
High humid Env.
Low T, High RH
High T, Low RH
16
Forced ventilation
17
Evaporative cooling
Fogging
18
Evaporative cooling
Pad and Fan system
19
Approach to release thermal stress
20
Approach to release thermal stress
Beware of the side effect.
21
Psychrometric Chart
22
(No Transcript)
23
(No Transcript)
24
Process from one state to another
25
(No Transcript)
26
(No Transcript)
27
Human comfort zone
28
Animal comfort zone T only
Productivity
Dry bulb temperature
29
Impact of T and RH on milk production of cows
64.65
82.49
72.32
68.47
63.39
76.68
64.31
75.73
79.96
63.7
65.05
87.09
90.09
88.06
86.01
82.09
84.21
82.36
THIgt85, no recovery
Adapted from ASHRAE Fundamentals, 1999
30
Reduction of milk vs. Temperature-Humidity Index
(THI)
Adapted from ASHRAE Fundamentals, 1999
31
Milk Productionf(HD74, HA80S)

• MP 21.48 0.051 HD74 0.0099 HA80S
• Where,
• MP Milk production (in kg/day/cow)
• 21.48 daily production (in kg) per cow in normal
  weather condition
• HD74 total hrs of THI gt 74 for previous 4 days
• HA80S square of total hrs of THI gt 80 for
  previous day
• Linvill and Pardue (1992)

32
THI lines on Psychrometric chart
33
More about Psychrometric chart

• Following contents, created by the author, are
  available from DSpace at UVM.
• Tutorial for digital psy chart
• Digital psychrometric chart software

34
The End