The psychrometric chart
(1) Selection of the Coordinates
Horizontal coordinate — Enthalpy (155°)
Vertical coordinate — Humidity Ratio
(2) Dry Bulb Temperature
I = 1.0T + W(2501.3 +1.867) (SI Unit)
7 = const=>7 ocW
Isothermal lines are not parallel.
Dry i? u!t temperature |
(3) Relative Humiditx’
W = 0-622—~~ <P = — xl00%
P-(p Pv, s Wsp-Ps
Under a certain P, W = f{pv s) pv, = f(T)
From P587 Table A-lb. find W-T relationship
W
Approximately (J) « — x 100% (equal division)
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(4) Specific Volume
Pa + Pr=-TZ +
RJ RJ T
(5) Wet-Balb Temperature
Dry tu/t temperature ffj |
Go |
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I = (Cp, a + W Cp, v) Twet + W x 2501 when Twet= const, linear relationship
I = (Cp, a + w Cp, v) Twet + w x 2501 + W iw when <|> * 100%
(6) Sensible Heat /Total Heat
Enthalpy/Humidity ratio
See figure: Primary moist air parameter on the psychrometric chart.
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For specific pressure:
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Repeat the previous problem by using the psychrometric chart. Given: Tdiy =30°C, Twet = 26°C
Find: Primary moist air parameter on psychrometric chart Solution:
Posted in Fundamentals of Heating. Ventilating, and Air-Conditioning