Learning Psychrometrics and Sensors measuring T and RH

Learning Psychrometrics and 方煒 Sensors measuring T and RH台大生機系教授 Wei Fang, Ph. D. , Professor Dept. of Bio-Industrial Mechatronics Engineering, National Taiwan University

Analog Dry Bulb Temperature sensor

Analog Dry and Wet Bulb Temperature

Digital Dry Bulb Temperature reader

Infra-red Dry Bulb Temperature

Sensing element

Dry and wet Bulb Temperature sensors in Weather station and greenhouse

Tdb and RH Sensors

Tdb and RH data logger

Day/Night trends of T and RH

High T coexist with Low Hum. 濕度 溫度 午夜 中午 午夜

High humid Env. Low T, High RH High T, Low RH

Forced ventilation

Evaporative cooling Fogging

Evaporative cooling Pad and Fan system

Approach to release thermal stress

Approach to release thermal stress Beware of the side effect.

Psychrometric Chart

Process: from one state to another

Human comfort zone

Productivity Animal comfort zone – T only Dry bulb temperature

Impact of T and RH on 64. 65 milk 82. 49 production of cows 63. 39 68. 47 72. 32 76. 68 87. 09 90. 09 88. 06 65. 05 75. 73 79. 96 63. 7 64. 31 86. 01 82. 09 84. 21 82. 36 THI>85, no recovery Adapted from ASHRAE Fundamentals, 1999

Reduction of milk vs. Temperature-Humidity Index (THI) Adapted from ASHRAE Fundamentals, 1999

Milk Production=f(HD 74, HA 80 S) MP = 21. 48 – 0. 051 * HD 74 – 0. 0099 * HA 80 S Where, – MP: Milk production (in kg/day/cow) – 21. 48: daily production (in kg) per cow in normal weather condition – HD 74: total hrs of THI > 74 for previous 4 days – HA 80 S: square of total hrs of THI > 80 for previous day Linvill and Pardue (1992)

THI lines on Psychrometric chart

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

The End