Question

Question 5 (a) A sample of moist air at a temperature of 36 °C and total pressure 1.01 bar has 0.018 kg of moisture per kg of dry air. Calculate the relative humidity and the enthalpy (kJ/kg of dry air) of the air. (8 marks) (b) The air in (a) is cooled at constant total pressure until condensation of water just begins. Calculate the temperature and the enthalpy (kJ per kg of dry air) when condensation just begins. (6 marks) (c) Calculate the total heat removed from the air and the work done on the moist air during the cooling process (b), in kJ per kg of dry air. (11 marks) The specific heat capacity of moist air is 1.02 kJ/kgK.

Answer 1

uh solution of the problem Creun Td = dry bulb tomberature = 36% Pb= Tatial bressure = lol bor. We specie humidity= 1018 1g / ing I dry. Parta 0= Relative humidity = my pr o Where Py = Partial pressure of water nabour PS= saturation pressese consesponding dry bulb timp. the value of Ps corresponding to 366 temperates a 5744 Pa. ms W = 0,622 Pv Pb-Pv 0.old = 0,622 x Pv 1.01- PV old 18 r018ly = 0.622 Pv I P = 1028 bar Cutting the value in equation 18 = or 99%

PARTE Inthalpy Inthalpy of dry air is guun by. he 1°005 ++ W[2500+ 11897] Where t= Dry bulb temp. W = specific humidity Rio 1.005 X 36+ 018 [2500 +1.88X36] = 82.39 kJ/kg og dry an. PART-C Since the air is cooled at constant pressure then the temperature at which the condensation begins is dew point temperature & The Valeng dun point temperatese can be calculated from steam table corresponding to Puole PART-D The PARTE Tdp = Dew point tempa 23.6°C The enthalpy corresponding to this temperatur ho 1'005 x 23.6 +.010 [2500 + 188x23.67 h2= 69.51 kJ/kg of dry air. The total heat remoed will be (BI-R2). Kilkg og dry air. Thank you. Please give a thumbs up. (As HOMEWORKLIB POLICY 4 subparts can be answered)