Answer Happy

Task 4 (23.5 points) An air-conditioning system operating in cyclic mode is used to air-condition a seminar room with a volume VR = 255 m3. The procedural process of this system is kept very simple: In the operating cycle, exhaust air (A) is drawn in, which is first mixed with fresh air. The air mixture is then cooled down at the evaporator of a compressor, whereby water condenses out. After separation of the condensate, the supply air (z) is finally fed into the seminar room in a saturated state (p = 1). At the time to the air conditioning is switched off and the room air (R) has a temperature of tr (to) = 20 °C and a relative humidity of QR (TO) = 55 %. Abluft (A) Raumluft (R) tR(To) = 20 °C PR(To) = 55 % Zuluft (2) tz = ? °C xz = 8.61 9 (Wasser) kg (Luft) Hint: - Only the conditions of the room air (R), exhaust air (A) and supply air (2) are relevant for the solution dask parts a) to f), therefore the figure above only shows the situation in the seminar room. - Air and water vapour de regarded as ideal gases. - The admixture of the water vapour from the persons present in the seminar room is isenthalp. - The substance data for air and water were deliberately changed for this exam, so that the h1+x -x diagram from the adocuments cannot be used. All parts of the assignment must be solved purely by calculation. - Round the results to one decimal place (e.g. 1023.0 or 58.2).

a) (5.5 P] What is the enthalpy HR (to ) (in kJ) of the room air (R) in the seminar room at time to? The people present in the seminar room emit heat and, through breathing, also water vapour into the room air (R). After a period of Aton = T1 - To = 1 h has passed with the air conditioning switched off, a temperature of tr (11) = 28°C and a relative humidity of 4 (TR) = 45 % is reached in the seminar room at the time t.1 If necessary, use the following values task part b): - Mass of dry air in the seminar room mtr.LR= 461.5 kg - Enthalpy of the room air (R) in the seminar room at the time to is HR (T0 ) = 28479.9 kJ b) What is the kilow in W) and the mass flow of water niv.p (in g/h) emitted by the persons ? [5.5 P] At the time t1 the air conditioner is switched on and runsfor a period of At 12 = T2-T1 = 0.5 h. During this time, the air conditioner draws in exhaust air (A) and blows supply air (2) into the room. The mass flow of dry air is constant: n.L,A = 1.lz. The supply air (Z) is in a saturated state (uz = 1) and has a water content of xz = 8.61 g (water) /kg (air). Use the following values, if necessary, bask parts c) to f): Mass of dry air in the seminar room mtr.LR = 593.4 kg - low emitted by the people in the seminar room = 3724.6 W - Mass flow of water emitted by the people in the seminar room , p = 1709.9 g/h c) [3.5 P] Calculate the temperature tz (in °C) and the enthalpy of the supply air (2) h1+x,z (in kJ/kg). At the time t2 the initial temperature tr (+2 ) = tr (to ) = 20 °C is reached again in the seminar room. However, the room air (R) now has a higher water content xr (12) = 11.13 g (water) / kg (air) > XR (To). d) What is the relative humidity QR (T2) (in percent) in the semi-room? [2P]