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You don't need the SG of the fluid because they are giving you the volumetric flow rate (in gpm). As @Audi driver, P.E. has pointed out, the table 18-5 can be a real time saver here. The equation in the table that has Q (volumetric flow rate in gpm) does not use SG. Here's why: Look at...

Hi @AlliChEME Congratulations! We're glad you did well. We appreciate the mention in your excellent post.

A shout-out to the men and women that have visited these boards and either just read along or actively seeked advice and/or help. I hope you found value in the group effort we all put around here in helping out. Be sure to come back later to share stories from the trenches!

Correct. If T5 had not been given, then you would need to calculate it.

The table of temperature values are all actual values. When they say "Station 5" they mean that is what a probe is registering there. The provided turbine efficiency is unnecessary for this problem and is a "distractor".

I think their 17 feet and your 23 feet are within the uncertainty of these problems in the real world, given the approximate nature of these values for loss coefficients (especially for valves). The problem in the PPI book is a throwback from the olden days when a human being actually laid eyes...

Ok. 4.6ft for the elbows makes more sense, but K is still not 0.6

Well, for starters 40ft + 5(6.4ft) + 2.5ft is actually 74.5 ft, not 65.5 -- but that's not all. There also seems to be something going on with the "conversion" from K to L_eq. For example, according to your data, the elbows have an equivalent length L_eq = 6.4 feet, and a loss coefficient K...

If the given conditions (T,p) are such that the thermodynamic state is “compressed liquid” then you could use the compressed liquid table. That table, however, typically only lists moderately high pressures. 1 MPa (10 bar) is too low and is not listed (at least in the one in MERM Appendix 23.Q...

Interesting observation. The dry bulb T and the relative humidity at the inlet are also given, so giving h_1 makes the problem over-specified. Luckily 33.6 Btu/lbm is the right enthalpy for the given values of T and r.h. I think it is more likely that the h_1 in the handwritten notes was looked...

We also advocate for this approach. The very first post in this thread is a good example showing how much time can be saved. Of course, Mollier diagrams are useful for superheated steam and high quality water-steam mixtures, that is, the typical steam turbine problem.

Close. m*Cp*DELTA-T is accurate for sensible cooling/heating. This would be somewhat accurate even for moist air as long as there is no condensation or humidification (i.e., the process is a horizontal line on a psych chart). If there is condensation (like in this problem) or humidification...

No. the nitrogen is flowing through an external jacket around the chamber. Look at the figure. One surface of the jacket is at -320F the other is adjacent to insulation. the 80F is the surface temperature of a heat source (because it has a heating element inside) inside the vacuum chamber...

The nitrogen is changing phase because it is being heated by convection het transfer occurring from the chamber walls to the nitrogen. It cannot be neglected. It is just not necessary to calculate it, because you can do an energy balance on the nitrogen. For example; suppose I ask to calculate...

If in that example they had specified the inlet and outlet conditions of the air in the duct, then you wouldn't need to calculate the heat loss with a heat transfer analysis. A simple energy balance for the air in the duct should give you the heat loss. In our problem, the inlet and outlet...

This is the correct approach. @MikeGlass1969

I hope. The level of activity on this thread (and others) now pales in comparison to what we had for the April exam.  

Yep. Its badly crafted as is. The factor (3.28/.2) or (.1368/.-0083) is too big and makes the final answer too sensitive to Tdp. I need to change the relative magnitude of the given R-values to improve the problem.   I think the problem itself is still pretty cool... just needs better numerical...