Owner manual

45
10. Calculation Result: DT, WB, AH, and HR
10.1 What is DT
DT -- Dew Point Temperature
Air with higher temperature contains more water vapor, and the air reaches a saturation point as
temperature lowered （Relative humidity: 100％）. Then continuously lowered temperature causes water
vapor to start condensing -- this temperature is called Dew Point Temperature.
There are many formulas to calculate the Dew Point Temperature; however, this manual uses calculation in
conformity with JIS standard Z8806.
ln(e
w
）=-6096.9385×T
-1
+21.2409642-2.711193×(10
-2
) ×T
+1.673952×(10
-5
) ×T
2
+2.433502×ln(T)
e=U/100×e
w
ｙ＝
ln
（ｅ／
611.213
）
When y≧0;
td=13.715×y+8.4262×(10
-1
) ×y
2
+1.9048×(10
-2
) ×y
3
+7.8158×(10
-3
) ×y
4
When y＜0;
td=13.7204×y+7.36631×(10
-1
) ×y
2
+3.32136
×
(10
-2
)
×
y
3
+7.78591×(10
-
３
) ×y
4
e
w
: Saturated water vapor pressure （Pa）
T: Absolute temperature （K）＝t(℃) + 273.15
T: Dry bulb temperature （℃）
E: Water vapor pressure （Pa）
U: Relative humidity
Td: Dew point temperature （℃）