25. A piston-cylinder device initially contains steam at...

25. A piston-cylinder device initially contains steam at 3.5MPa, superheated by 5°C. Now steam loses heat to the surroundings and the piston moves down, hitting a set of stops, at which point the cylinder contains water at 200°C. Determine a) the initial temperature, b) the enthalpy change per unit mass of the steam by the piston first hits the stops, and c) the final pressure and the quality (if mixture). (3-59)

Transcript

00:01 Temperature the enthalpy change per unit mass of steam by time that piston first hits the top in see the final pressure and the quality so we can say that here the piston cylinder device initially contains steam at 3 decimal 5 mpa so superheated by 5 degrees celsius and the steam loses heat to surrounding the piston moves down hitting a set of stops which point the cylinder contains saturated liquid water so here we can see that in diagram this is v this is t and here 3 2 and this is 1 so in which point the cylinder the contains saturated liquid water the cooling continues under the cylinder contains water at 200 degrees celsius so now we can say that here data from a to 6 using interpolation now we can write here h1 equal to h1 plus h2 minus h1 divided by c2 minus d1 so t t 1 minus 3 1 dash so so we can write here 28 02 decimal 7 plus 28 29 decimal 7 minus 2802802 decimal 7 divided by 250 minus 242 decimal 56.

02:48 And we can write here 247 decimal 56 minus 2.

02:54 4 7 decibel 56 now we can write here h1 equal to 2820 8 kjouled per kg now in a we can write here initial temperature from table 8 to 5 so we can write here t saturated at the rate 5 m p .a equal to 242 decimal 56 degrees celsius.

03:40 Now we can write here, t1 equal to 242 decimal 56 decimal 5.

03:48 So t1 equal to 247 decimal 56 degrees celsius.

03:55 Answer.

03:57 Now in v, in b, the enthalpy change per unit mass of steam by the time the position first hits the stop.

04:09 So we know that here is given h1 equal to 2820 .8 kjule per kg.

04:19 Now del h equal to h2 minus h1.

04:25 So here is h2 is 1049 decimal 7 minus 28 20...