Question

Air pressure = 100 kPa Air temperature = 20 deg Wet-bulb (Dew Point) temperature = 16 degC Find: - Vapor pressure - Relative humidity, - Specific humidity, - Air density

Answer 1

S ven data → Air Pressure 'Pa' = look pa Air tempo (DBT) Toei = 20°C wer bull temp? 'I woi - 16'6 lii vapour Pressure 'Po' => As cure know from " Dalton Partial Pressure Law Photo PIT P2 + P₃ .. so in our case, . - Pa t = t put vapour pressure - (need to calc.) - barometric o Pressure air pressure ClookPa) To to use need • - Modified find Apsonn 2 'Pr we equation" we know that Argohn - equn Pea Pu - [*** R (Toor Twer] 2700 Here in equna Pula saturation Pressure - at WBT from the help of steam table . we con calculare Pv! So at . 16°C , saturation Pressure is 108180 kPa ?u= 1:8180 kPa

Now put all data in Apjohn egun =) Pv = 1.8180 - [1.8 ( Pat Pv) (20-1677 2 700 => Po = leieo - (10975 Port IV 1.9180 - 100 + pv 375 => Pu + pv 375 = 108180 - 100 375 7 Ans =>> Pro 1.5472 kPa vapour pressure cil Relative humidity As we know that humidity (t) given by the relative & Puc= saturation Pressure corresponding to DBT. with the help of steam table, nu can find at 20°C tempi, saturation Pressure is . 2.3376 kPa. Pus = 2.33766 Pa Pu: 1.5472 kPa .. (calc. Previously) - - D.66.18 1.5472 2.3376

= 66. 18o. 30 Ans - "relative humidity" I mül specific humidity » that specific humidity w As we know t is given 'w's by my = ma mass of water vapour Kolkoot dry air mass of mass of air - The at can ideal 8 dry ma O water vapour Present in air ir very very low Pressure so we treat that water vapour as an gas. air is also treated as ideal gas > PV = ma Rata Pava= ma Ta Ra ma= R K = Pava Ra Ta Ra T Pu Vo = mv Rv Tv - - mu » - - Pu vy mu= P T TL mu - W = Pu Vv Ra. Ta Ru Tv Pava Rr Tv l ava] • Ra. Tal Ta - Ty 7 VV = Va ... bcoz they are au mixed together C Rv Pa Y.R Mrizo w = 3314/29 W = 8. 314/29 8.314 718 = 0.622

W= 0.622 x 105472 = 9.62 35x10-3kg kg of a 100 dry aire g. 623g/kg of DA w= 9.623x10 Pans - " specific humidity" egun lind Ain density to According to ideal gas Pu= MRT P= PRT - equcio use equncil on air Para= mara Ta . Par la Rała 100 1.1904 a lasta - Pa = q 8.314 X 293 29 I la = 1.1904 kg/m3. Ans. " Air density