please solve complete in one hour

Post by **answerhappygod** » Tue Apr 12, 2022 9:56 am

: Please Solve Complete In One Hour 1 (86.06 KiB) Viewed 21 times

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Task 4 An air-conditioning system operating in cyclic mode is used to air-condition a seminar room with a volume VR = 250 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 (v = 1). At the time to the air conditioning is switched off and the room air (R) has a temperature of Temperature of tr (to ) = 20 Cand a relative humidity of or (to ) = 55%. Abluft (A) Raumluft (R) tr(To) = 20 °C PR(To) = 55 % Zuluft (2) tz = ? °C Xz = 8.00 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 task 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).

The state of the extract air (A) is not constant in the real case and depends, among other things, on how quickly the room air (R) mixes with the supply air (Z). For simplification, assume infinitely slow mixing so that the state of the extract air (A) is constant and corresponds to the state of the room air (R) at the timet: ta = tr(t) = 28, QA = OR (TI) = 45%. Note: Bear in mind that the people present naturally also emit heat and water vapour into the air during the operating cycle of the air conditioner. e) What is the mass flow of dry air ri.LA = 1.lz (in kg/h)? f) Discuss how the state of the supply air (Z) and, if necessary, other parameters of the air-conditioning system must be changed in order to restore not only the temperature but also the relative humidity of the initial state: tr (12) = tr (to) and o (tr) = OR (T ). Substance data General gas constant: Rm = 8.314462 J/(mol K) Molar masses - Air: M = 32.46 g/mol Water: Mw = 19.52 g/mol Specific isobaric heat capacities - Dry air: Cp,l = 1,407 kJ/(kg K) Water vapour: Cp, D = 2.26 kJ/(kg K) - Liquid water: Cp,w = 5.19 kJ/(kg K) Enthalpy of evaporation of water at 0 : Ah, = 3000 kJ/kg Vapour pressure of water: In(p/mbar) = 18.9141 - 4010.823/(t/ C + 235.4623) Total pressure in the environment and in the seminar room: p = 1 bar

a) 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 also water vapour into the room air (R) through breathing. When the air-conditioning is switched off, a period of er of AT = Ti. T= 1 h has passed, the temperature at the time tiis tr (t) = 28 Cand a relative humidity of QR (T) = 45 % in the seminar room. If necessary, use the following values task part b): - Mass of dry air in the seminar room mtr.LR = 459.7 kg - Enthalpy of the room air (R) in the seminar room at time to is HR (to ) = 24612.7 kJ b) What is the laddow in W) and the mass flow of water ip (in g/h) emitted by the persons ? At the time t, the air conditioner is switched on and runsfor a period of A112 = T2. Ti = 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: 1.LA = nt.LZ. The supply air (Z) is in the saturated state (z = 1) and has a water content of xz = 8.00 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= 591.1 kg - how emitted by the people in the seminar room Q = 3231.3 W - Mass flow of water emitted by the people in the seminar room up = 1596.4 g/h c) Calculate the temperature tz (in °C) and the enthalpy of the supply air (2) hi+xz (in kJ/kg), At the time t2 the initial temperature tr (12) = tr (to ) = 20 is reached again in the seminar room. However, the room air (R) now has a higher water content xr (T2 ) = 10.35 g (water) / kg (air) > XR (T0). d) What is the relative humidity R (12) percent) in the semi-room?