tag:blogger.com,1999:blog-20953269.post6337796885081960127..comments2023-04-22T16:35:23.188-07:00Comments on Thermodynamics: ENGR 224 - HW #3Unknownnoreply@blogger.comBlogger52125tag:blogger.com,1999:blog-20953269.post-7614882641495500492011-04-21T00:43:43.288-07:002011-04-21T00:43:43.288-07:00Hey for WB-2 I got .743 in and 630 degrees Fahrenh...Hey for WB-2 I got .743 in and 630 degrees Fahrenheit. I am working on WB-3 now it is going ok I think...and ya I will see you at 8 haha.Jaysonhttps://www.blogger.com/profile/12297110225283255402noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-73107037931407302272011-04-20T23:21:51.270-07:002011-04-20T23:21:51.270-07:00yes, I will see you guys at 8amyes, I will see you guys at 8amAndreinoreply@blogger.comtag:blogger.com,1999:blog-20953269.post-69369202405824082022011-04-20T22:53:31.976-07:002011-04-20T22:53:31.976-07:00I'm working on this too, if we dont figure it ...I'm working on this too, if we dont figure it out, Hes supposed to have an office hour from 8 to 9 am on homework days, just in case you guys didn't knowCamdennoreply@blogger.comtag:blogger.com,1999:blog-20953269.post-47500190901525089522011-04-20T21:56:16.758-07:002011-04-20T21:56:16.758-07:00Hey Jason,
I am working on WB-2 too.
Look, you can...Hey Jason,<br />I am working on WB-2 too.<br />Look, you can find diameterthrough formula: Area=(PI/4)*D^2 ==> D=2*sqrt(Area/Pi)<br />let me know what answers you get, because my answers doeasn't match with answers on the HW sheetAndreinoreply@blogger.comtag:blogger.com,1999:blog-20953269.post-70635616223616547862011-04-20T21:50:56.925-07:002011-04-20T21:50:56.925-07:00Not sure if your still up Dr. B, but I am having t...Not sure if your still up Dr. B, but I am having trouble on finding diameter in WB-2. I think I should use a volume equation but I am not sure how volume can help me get diameter, cause the shape of the compressor is funky. Perhaps, the equation Velocity=(1/A)2pi(vr dr)integrated from r to 0?Jaysonhttps://www.blogger.com/profile/12297110225283255402noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-74086943087714768552011-04-20T20:59:51.553-07:002011-04-20T20:59:51.553-07:00Ok thanks Dr. B that helps a lot.Ok thanks Dr. B that helps a lot.Jaysonhttps://www.blogger.com/profile/12297110225283255402noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-74075782743318665352011-04-20T19:42:02.292-07:002011-04-20T19:42:02.292-07:005.35
Yes!!!Solved. I figured it out after "pl...5.35<br />Yes!!!Solved. I figured it out after "playing" with units!<br />Thank youAndrenoreply@blogger.comtag:blogger.com,1999:blog-20953269.post-1328526099895181592011-04-20T19:25:30.124-07:002011-04-20T19:25:30.124-07:00wb1
I've got to the point where i found H2(ha...wb1<br /><br />I've got to the point where i found H2(hat) but don't know what table to use in order to find T. I have a quality=1 (100%vapor) but P2 unknown. What table to use to find T2. <br />My value for H2 is kind of large 5059Btu/lbm<br /><br />TThank youAndreinoreply@blogger.comtag:blogger.com,1999:blog-20953269.post-55509766398116671742011-04-20T19:09:17.735-07:002011-04-20T19:09:17.735-07:005.35
o.k I understand this, but lets look at the u...5.35<br />o.k I understand this, but lets look at the units "delta"H(hat) in kJ/kg and "delta"Ek in (m/s)^2. ...or I have to devide everything by Gc ((kg*m)/N*s^2))<br />?Andreinoreply@blogger.comtag:blogger.com,1999:blog-20953269.post-36913823704304460842011-04-20T18:59:13.680-07:002011-04-20T18:59:13.680-07:005.35 , Andrei , 6:42pm
You should have reduced the...5.35 , Andrei , 6:42pm<br />You should have reduced the 1st Law to 0 = mdot*(DH^+DEk^)<br />Then, divide by mdot and it drops out of the problem! Always watch the units !<br /><br />I hope this helps.Dr. Bhttps://www.blogger.com/profile/16971900402833290264noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-709108208628499772011-04-20T18:54:18.910-07:002011-04-20T18:54:18.910-07:00@Dr.B: 5.112
Yeah, I got -19.938 kW also....@Dr.B: 5.112<br />Yeah, I got -19.938 kW also....Teenoreply@blogger.comtag:blogger.com,1999:blog-20953269.post-91140256568322530952011-04-20T18:42:18.179-07:002011-04-20T18:42:18.179-07:00Problem 5.35
after writing the first law and negle...Problem 5.35<br />after writing the first law and neglect all necessary terms, I end up with H2(hat)-H1(hat)+<br />+mass*(((V2^2)-(V1^2))/2) From table I get H1(hat), but I don't have mass value. in order to find H2<br />Please help!<br />ThanksAndreinoreply@blogger.comtag:blogger.com,1999:blog-20953269.post-61377408837654531572011-04-20T16:48:37.235-07:002011-04-20T16:48:37.235-07:00WB-2 , Jayson , 4:15
You can use Vdot or Vhat or V...WB-2 , Jayson , 4:15<br />You can use Vdot or Vhat or Vwiggle because they are all proportional to each other in this case. <br /><br />I don't see any way to calculate plain old volume, V, because this is a flow problem.Dr. Bhttps://www.blogger.com/profile/16971900402833290264noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-46835903176932144672011-04-20T16:15:15.535-07:002011-04-20T16:15:15.535-07:00For WB-2 When using the polytropic equation P1V1^1...For WB-2 When using the polytropic equation P1V1^1.34= Constant, can you use the specific volume or the volume flow rate, or do you need to solve for volume?Jaysonhttps://www.blogger.com/profile/12297110225283255402noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-92114091500192954472011-04-20T15:54:56.972-07:002011-04-20T15:54:56.972-07:00Thank you but that is frustrating cause I have bee...Thank you but that is frustrating cause I have been trying to use different variations of the first law for at least an hour. I need to think outside the box more.Jaysonhttps://www.blogger.com/profile/12297110225283255402noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-72194480453693196412011-04-20T15:49:47.481-07:002011-04-20T15:49:47.481-07:00WB-2 , Jayson , 3:37pm
N, you do not need to assum...WB-2 , Jayson , 3:37pm<br />N, you do not need to assume the compressor is adiabatic. Take a look at my previous comment.Dr. Bhttps://www.blogger.com/profile/16971900402833290264noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-85520281943305256082011-04-20T15:48:52.221-07:002011-04-20T15:48:52.221-07:00WB-2 , Jayson , 3:22pm
Yes, it is ok to divide the...WB-2 , Jayson , 3:22pm<br />Yes, it is ok to divide the 1st Law by mdot and write it as: Q_hat - Ws_hat = deltaE_hat.<br /><br />But the wierd part of this problem is that you do NOT need to write or solve the 1st Law to answer the question ! You already determined mdot. Use th polytropic path eqn to determine D2 and then use the IG EOS to determine T2.Dr. Bhttps://www.blogger.com/profile/16971900402833290264noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-10304036262394579152011-04-20T15:45:18.893-07:002011-04-20T15:45:18.893-07:00WB-2 , Jayson , 2:53pm
OK, I disregarded this ques...WB-2 , Jayson , 2:53pm<br />OK, I disregarded this question as you instructed in your next comment.Dr. Bhttps://www.blogger.com/profile/16971900402833290264noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-19706331977360969662011-04-20T15:44:18.908-07:002011-04-20T15:44:18.908-07:00WB-4 , Anon , 2:50pm
DOH ! My mistake. Thank you...WB-4 , Anon , 2:50pm<br />DOH ! My mistake. Thank you for pointing this out !<br /><br />I changed the process flow diagram and the stream numbers and forgot to change the hint! All the "T2" references in the hint should be "T3". But the reference in the hint to Hsatliq is correct.<br /><br />Stream 3 is a subcooled liquid. The lowest P table in the subcooled liquid table in your book is for 5MPa and P3 = 2.5 MPa. As a result, you need to interpolate between Hsatliq at 200C and H(5MPa,T3) to get H3=H(2.5 MPa,T3).<br /><br />This process is painful using the tables. I suggest you use either the NIST Webbook or the TFT plug-in for Excel.<br /><br />I hope this helps!Dr. Bhttps://www.blogger.com/profile/16971900402833290264noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-40744383706267625782011-04-20T15:37:21.033-07:002011-04-20T15:37:21.033-07:00Can we assume WB-2 is adiabatic? Cause if we can m...Can we assume WB-2 is adiabatic? Cause if we can my problems are smaller.Jaysonhttps://www.blogger.com/profile/12297110225283255402noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-13078998824159695292011-04-20T15:22:57.071-07:002011-04-20T15:22:57.071-07:00Disregard my comment made at 2:53 I realize that i...Disregard my comment made at 2:53 I realize that is not a good approach, I put mdot back in the problem (WB-2) and I solved for it no problem, and I used the plugin to find H1. However there is still H2 Qdot and Wdot. I am thinking maybe for Wdot I could use the area under the polytropic curve but that still leaves H2 and Qdot and I cant figure out what equation to use.<br /><br />Thanks For Helping by the way. I can not do this alone.Jaysonhttps://www.blogger.com/profile/12297110225283255402noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-2945752592749791152011-04-20T15:20:49.630-07:002011-04-20T15:20:49.630-07:00Jayson , 2:45pm
One way is to ASSUME the Ideal Gas...Jayson , 2:45pm<br />One way is to ASSUME the Ideal Gas EOS applies and use it to calculate the molar volume. Then, compare this molar volume to 20 L/mol or 5 L/mol (diatomic & noble gases). This is not perfect, but it is MUCH better than just making the IG assumption and never thinking about it again.<br /><br />I hope this helps.Dr. Bhttps://www.blogger.com/profile/16971900402833290264noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-38188482162646019552011-04-20T14:53:26.802-07:002011-04-20T14:53:26.802-07:00Also in WB-2 I assumed no kinetic and potential en...Also in WB-2 I assumed no kinetic and potential energy, that leaves Qdot-Wdot = mdot*(H2-H1). Then with another algebraic manipulation I turned the Qdot and Wdot into Qhat*mdot-W_hat-mdot= mdot*(H2-H1) and then divided by mdot, which gets rid of it. The question is, do I want to do that, and is that a legitimate step?Jaysonhttps://www.blogger.com/profile/12297110225283255402noreply@blogger.comtag:blogger.com,1999:blog-20953269.post-18613928394614490602011-04-20T14:50:31.330-07:002011-04-20T14:50:31.330-07:00In problem WB-4, why are you referring to T2 and H...In problem WB-4, why are you referring to T2 and Hsatliq instead of T3 and Hsatvap to plot the graph?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-20953269.post-55289123493378151932011-04-20T14:45:45.946-07:002011-04-20T14:45:45.946-07:00How can you verify that a gas is ideal without hav...How can you verify that a gas is ideal without having A volume amount given? Do you some algebraic manipulation with volumetric flow and mass flow or something?<br /><br />ThanksJaysonhttps://www.blogger.com/profile/12297110225283255402noreply@blogger.com