Question

Question 20 A rigid, well Insulated tank of volume 0.9 m3 is initially evacuated. At timet, air from the surroundings at a pressure of 1 bar and temperature of 27 begins to flow into the tank, An electric resistor transfers energy to the air in the tank at a rate of 676 Watts. Determine the time required for the temperature of air inside the tank to reach 457 C at the same Initial pressure of 1 bar. Note: Please upload your answer sheet to receive partial credit. Any answer without an uploaded worksheet showing detail analysis will be given 25% of the mark only. Your answer must list all engineering model assumptions. Click if you would like to Show Work for this question Open Show Work

Answer 1

Question is solved below

Guiven :- Tank Volume v= 0.9 m3 Find Time sequined by ain to suoch Ta =4sać inside the tank ENGINEERING MODEL:- 1. Air is considered as ideal gas Air Tank 2. Control volume is defined as Pi = 1 bar shown in figure 3. Tank in insulated Qu=0 and Wer = 6765 energy is negligible 4. Ajn condition entering the # # tank is constant Fon the reviston AV resistos = 0 V=0.9m3 Ti = 27€ = 300k + change in potential & Kinetic Initially m-0 Finally P2 = 1 bay 7= 457°C = 730K st=? 5. dmcy Now The mass rate balance reduces to mi dt 0 The rate balance energy ducu - X - Wewt m; hs - więke dt There is no heat transfer no mais exits the control volume from een malu-m, Us = ta Wow at this my dt ti This dmcumi It Mella - neile - We At + hi(memorij ata midt mam, 0.4295 Wer= machi-U2) Initially m, zo at apply ideal gas equation to final state to deleormine m₂ P2 V2 17105x0.9 x12 m₂ R Tz due to from table of air hi = 300.19 KJ 42 = 536.07 kJ/kg syetem put all values inean 6768103 0.43 ( 300.19–536.07) - At = 150.0420 see a 2.5 min ot 0.2877730 kg = 0.43 kg Wersave work done on -