How I Approach Understanding Thermodynamics

Рет қаралды 6,863

2 жыл бұрын

I'm no expert in thermodynamics... But in this video I show how I wrap my head around problems that come up in chemical thermodynamics so you can hopefully have an easier time understanding thermodynamics.
Huge thanks to the REFPROP team at NIST! The software I use to plot all charts you see in the video is FREE for download here: trc.nist.gov/refprop/MINIREF/MINIREF.HTM
00:00 Thanks to REFPROP/NIST
00:38 Different chemicals - similar diagrams
02:07 Enthalpy on the x axis
03:29 Increasing temperature without heat
05:36 Pressure on the y axis
06:01 Other thermodynamic charts
06:59 Isotherms & other lines
09:21 The two-phase region
09:50 The liquid region
11:00 Heating & boiling water
13:45 The effect of pressure on boiling
15:55 No molecule exists in the two phase region
18:37 Heat of vapourisation & specific heat
21:47 The critical temperature & air distillation
24:29 The critical pressure
25:22 Supercritical fluids
27:14 Final thoughts
Process with Pat is the place to come for perspective and to ask stupid questions. I want you to leave more knowledgeable, confident, motivated, and most importantly, curious. I also want to invigorate a field that seems tired and uninspiring, at least if you get your perspective from internet forums. These are not lectures. This is a place for you to leave thinking “Oh! That’s why...”
This channel is not only for chemical engineers - anyone who works with processes should be able to find something of value here.
#Thermodynamics
#UnderstandThermodynamics
#ChemicalEngineering

Пікірлер: 20

@dmcafx 3 ай бұрын

I have been engineer for many years and I did not know this information. Thanks a lot!!! understood many things which I didn’t know.

@mohamedjessar5770 10 ай бұрын

This is the best explanation ever, Hats off

@davidcora2751 9 ай бұрын

Thanks for enlightenment!! A good video to enlighten potential engineers. Thanks for the knowledge 💕❤️

@user-hs8om6xi9n 9 ай бұрын

Wonderful! You have changed the way I look at thermodynamics.

@ChemEngWeekly 2 жыл бұрын

Thanks for sharing Pat! I can definitely say I understand more about thermodynamics now!

@piotrektabo4750 Жыл бұрын

Absolutely amazing explanation skills!

@carultch Жыл бұрын

I never thought I'd see the value in the P-h diagrams, until I saw your videos. I'm so used to seeing cycles on T-s and P-V diagrams, that when I opened the P-h diagrams in my software that they looked so foreign to me. Seeing the heat exchanger processes take place on simple straight lines, makes it so much easier to draw than the isobars on T-s diagrams. The one disadvantage is that you no longer have area under the plot, corresponding to heat or work, like you do on T-s and P-V diagrams.

@DaveMody 11 ай бұрын

Pat, your vacuum cleaner is probably using the air flowing through it to cool the motor, so while you're right, that's not very good vacuum cleaner to illustrate the problem. I do like how you take items in your everyday environment and explain principles with them. Keep that up :)

@ProcesswithPat 9 ай бұрын

You are totally right. Thanks for pointing it out! I certainly need to keep a running list of mistakes I’ve made that should be corrected or clarified somehow.

@mikefochtman7164 10 ай бұрын

Nice explanation and discussion. I'd just one little 'nitpick'. Early at 1:30 you show C-O-C for CO2. While CO2 is a linear molecule (unlike water), it should be O-C-O :) After all, it has two oxygens and one carbon.

@fredkuijper6986 11 ай бұрын

Excellent video, much more educational than any other youtube videos I've seen so far. One note: would you mind removing that annoying background "music"? :)

@GuessWho-pq1or 9 ай бұрын

One quick clmment: measuring air temperature at the outlet of a vacuum cleaner, do we take into consideration the heat generated by the electrical motor? Unless, of course, that particular vacuum cleaner has separate casing for its motor and correspondingly separate cooling outlet.

@rasmussverdrup7479 2 жыл бұрын

I think that the institute of standards and technology has decided that if you are calling one end of an object the "business end" the other must be "the fun end."

@ProcesswithPat 2 жыл бұрын

By backup plan was the sucky and blowy ends. I definitely approve of the fun end!

@xse345 2 жыл бұрын

Nice explanation there. Just one clarification, at 22:01 you says at high enough pressure, It takes no energy to boil water, or i.e. its easier to vaporize with increasing pressure ? That doesn't seem right. Correct me if I am wrong.

@ProcesswithPat 2 жыл бұрын

Correct! Check it out in a steam table and prove it to yourself... Hear are a few heats of vapourisation at different pressures: 1 bar (atmospheric): 2258 kJ/kg 100 bar: 1317 kJ/kg 200 bar: 584 kJ/kg 221.2 bar: 0 kJ/kg (these are according to my steam table, I see a slight difference if I use some online versions, but they are small). It seems unintuitive because you think higher pressure steam, higher temperature more energy. Higher pressure steam simply contains energy that is available at a higher temperature. Even though 1 bar steam may have a higher latent heat, it is only available at 100 °C. Processes that utilise steam for heating need to be heated more than this.

@xse345 2 жыл бұрын

@@ProcesswithPat oh... it seemed unintuitive to me because, lower pressure --> lower boiling point --> less temp required --> less energy needed. Still confuses me.

@axeld53 2 жыл бұрын

@@xse345 A lower boiling point only tells you that the heat source you need to make that liquid boil doesn't have to be too high. However, it doesn't tell how how much energy you must give that liquid in order to make it boil. In the Pressure-Enthalpy diagram (P-h), you can see that the boiling point of the water is the line that becomes a horizontal in the two-phase region, meaning it is constant at constant pressure. You can see that " lower pressure --> lower boiling point --> less temp required" is indeed correct. But the amount of energy needed to make the liquid boil off if the difference of enthalpy between the vapor (right side of the two-phase region) and the liquid (left side of the two-phase region), which corresponds to the width of the two phase region. As you can see, as pressure goes up, the width of the two-phase region decreases, therefore the amount of energy required to completely boil the liquid decreases. As you approach the critical point, the width approaches zero, and when you reach the critical point, there is no difference between the enthalpy of the liquid and that of the vapor, hence the amount of energy needed to boil water at this point is zero. Further from that point there is no distinction between the liquid and vapor phases and the whole system becomes what is called a supercritical fluid. There are a lot of videos here on KZfaq showing this transition happening.