At a location in California and at a depth of 7 km, there is a magma reservoir with a temperature of 900 °C. It has been proposed to drill a well into the magma chamber and insert two coaxial pipes. Cold water is forced down the annular region between the two pipes, hits the hot magma and evaporates. The steam generated will rise through the inner pipe and feed a thermal power station. The cost of the electrical energy thus produced is expected to range from 9 to 22 cents per kWh. Compare this cost with that of electrical energy generated in nuclear power stations and in thermal power stations using fossil fuels.

After some research it appears to be directly proportional. However I am in the midst of a question where I have the opposite results. I have a hunch it’s relating to time through the heat exchanger but I’m not too sure.

The context is regarding a condensing shell and tube heat exchanger where the T,cold-in and T,hot-out are given. I have produced the attached calculation of results (step by step). I’m pretty sure the results are right as I have compared with other students. However I would like a better understanding of why it appears to be against expectations.

Good evening smart folk. Trying to find a doggie door because keeping the human door open all day during winter really doesnt do well on my human heat needs (nor the power bill).

First of let me clarify you dont need to provide me an exact model of a doggie door or something. Would be nice if you did, but I could probably figure that part out if i know what to look for.

Next. Forgive me for being ignorant about all this, but i assume it needs to seal to not leak heat. From walking into big freezers i have also seen these rubbery drape things to trap heat. These two dont seem to go well together though as last i checked a seal needs to seal.

Seen some designs where its 2 doors. Like how you deal with cattle. House > door > room > door > outside. Minimizes leakage more i think.

Not sure if this info matters (not sure if any of this matters), but the enterance will be at the furthest point from the heating in the house. There will be 1 wall mounted heater right next to it, but most of the house heating will be on the other side. Dog is also a german shephard, so i guess the hole in the wall would be about 50-60cm (19-20inch).

Almost forgot one of the important parts. How cold will it get? It gets chilly around here. Could drop down to -20c or lower. Sure wouldnt hope it does though.

Sorry for the wordy words. Thanks in advance. Stay cool (or hot? Whatever the compliment would be)

junkrat likes to sleep on it because it’s warm. i make sure to keep it on low level so he doesn’t get hurt. is this ok?

This was the question:

Steam flows steadily into a turbine at 3 MPa and 400C at a flow rate of 30 kg/s. If the turbine is adiabatic and the steam leaves the turbine at 100kPa, what is the maximum power output of the turbine?

Since its adiabatic, 1Q2 = 0

So your first law equation you just get -1W2 = m(h2 - h1)

And you have the values for enthalpy for h1 from super heated steam tables, and you can look at enthalpy of gas at 100kPa from saturated steam tables.

Did I mess up and was supposed to use second law to get T2 so I could get a more accurate enthalpy?

My answer was about 16.6 MW

Currently I am working on a project to manufacture 1,2,3-Triazole and the last step of the entire process involves distillation of the final product and N, N-DIMETHYLFORMAMIDE. To design this distillation column I need the Vapour- liquid equilibrium data for this at reduced pressure but I am unable to find it. I tried searching the data of similar compounds also but was unsuccessful. And UNIFAC calculations are too complicated to start with. I tried doing it but couldn't complete it. Can someone please tell me how to proceed with this situation of finding the most appropriate VLE data?

https://preview.redd.it/6wtyw7p1441e1.png?width=1023&format=png&auto=webp&s=596aa3cdfe73c2ee78ab450c753393d00aed2664

this isnt hw, its from a online course im taking for fun and im rlly interested so id rlly love some help.

In a adiabatic furnace there is 1tons of Cu at 1250°C. We put 10kg of Al at 25°C in the system. What is the final temperature?

Reminding while Al gains heat, temperature of Cu goes down a bit.

Solution should include heat capacity, enthalpy etc. 1st and 2nd thermodynamic formulas.

Please help me!!!

I am trying to solve a problem and I am so stuck on where to even start honestly. I have the state entering the diffuser, and unknown amount of heat going isobarically in the middle, and the state coming out of the nozzle. In my mind there are ways that I could solve it but I have a hold back for each. I would think to set the outgoing KE of the diffuser equal to the incoming KE of the nozzle but I honestly don't even know where to start with it. Part of me wants to say that the speed coming out of the diffuser and going into nozzle is zero but the problem specifically says that Ek becomes negligible during heating. So would the outcoming for the diffuser be non-zero but the incoming to the nozzle is zero?

TLDR: I'm stuck on an interheating question for air. It goes into a diffuser (incoming values known) then into isobaric heating where Ek becomes negligable, then into a nozzle (outgoing values known). Both have an efficiency of 90%

I get thermal diffusivity with thermal boundary laye and viscosity with velocity boundary layer but that’s about all. Are they correlated? Are they proportional? And how do they both cause heat transfer?

Thank you

Is there a 1 stop shop for good thermo learning and practice?

This product is a scam right? Ever winter I see these:-

https://youtu.be/MsyD6hXftP8?si=c0J-wWBIHFO7IP-x

Hello guys, I'm currently working on a thermodynamics project. I have to design A thermodynamic cycle using a Brayton cycle and a Rankine cycle using the energy of the Brayton cycle. It has to get an efficiency of 60% and produce 500MW.
I designed a cycle (see first photo) and I don't know if it can reach those performances. Could you also give me a hint to calculate the enthalpies without having any data at the beginning and how to make the fusion between the two cycles.

I also asked myself if I should replace the Rankine cycle part by a Rankine cycle I found (see second photo), would it help me ?

The cycle I designed

Should I change my Rankine cycle part to this cycle ?

How to solve the work non flow of a compression gas system which starts with an isobaric process, isothermal, polytropic, and ends with isochoric process given that p_3= 3000 and p_5= 6000 with v_1= 0.2; v_2= 0.4; v_3 and v_4= 0.6 and v_5= 0.8?

Hello folks, anyone here had cycle tempo software? Or maybe free download links? And also could it running simulation for geothermal powerplant with organic rankine cycle?

In the classic home a/c cycle .. the phase change in the evaporator coil and heat absorption is easier to understand than what happens outside the house with the compressor and the condenser coil..

1. Does a phase change happen in the condenser?
2. Is the heat that’s added to the refrigerant by the compressor a key part of the cycle OR is it a unfortunate byproduct when the vapor gets pressurized back into a liquid

3 since energy is conserved… is the condenser coil / fan able to remove ALL of the heat added by the compressor PLUS SOME of the heat absorbed by the evaporater coil? Otherwise the physics of the net removal of heat inside doesn’t make sense, right?

So, my textbook says that the shaft work in a polyprotic process will reduce by k% if inlet temperature is reduced by k%, this is possible if and only if the ratio of new exit pressure and new inlet pressure remains the same as the ratio of original exit pressure and original inlet pressure. The process is polytropic, hence P^(1-n)T^(n) = Constant.

I have been trying to prove this by considering new temperature T' = (1-k/100)T and then applying the polytropic process equations but I am not getting the required result, that is P1/P2 = (P1'/P2'). Any help will be highly appreciated.

(I'm just a student, and my question is somewhat pointless, but I'm asking here because I can't get proper answers anywhere else)
If we fill a liquid in a closed insulated container, and then begin rotating it such that the liquid inside undergoes motion, would it change the liquid's temperature in ideal conditions?

Say you are in a room with 6 beers, no fridge or anything. What is the best way to keep all 6 cold for the longest possible time. Assume temperature is a room temp room and you only have normal room stuff in your room

Hello, I have built a web tool that lets you plot thermodynamics cycles (e.g. Rankine, Brayton, Joule-Thompson, etc.) interactively.

I thought it might be a useful tool for students learning and also practitioners and design engineers for choosing operating points and understanding their process.

In the image I drew a vapor compression cycle for Propane.

If it interests you, the tool is available at thermoplot.com

I’d love to hear people’s feedback!

This is not a homework problem, just an example in our textbook that I came across and am stumped by. I am working on a note sheet for our exam and want to be prepared.

The problem states that a compressed liquid enters a valve at State 1 at 75 bar, and moves to State 2 with a quality of 0.2 at 3 bar. It asks to find the enthalpy and pressure at State 1 (in that order).

Obviously there are ranges to what the temperature can be, but is there any way to derive it from the pressure alone? I looked through the tables for a compressed liquid, but couldn't understand why the book shows an answer of ~230° C for the temperature. Enthalpy is not given.

I assume the questions it asks past these two can be assumed to have a constant temperature given it is a closed system.

I have a questiom about calculating the delta G for vaporization of toluene into the atmosphere at its boiling point. My logic is that dG=VdP-SdT, pressure and temperature are both constant, so dG=0 and delta G is also 0. This makes sense for vaporization at toluene's boiling point, because vaporization at the boiling point is reversible so delta G is 0.

My question is, what am I missing that causes this logic to break down when it is hotter than the boiling point? I would think I could apply the same logic, dP=0 and dT=0 so delta G is 0. But, I know that vaporization beyond the boiling point is spontaneous, so delta G should be <0. What am i missing here?

Also i know i could probably look up values for delta H and delta S of vaporization and then find delta G, but we haven't gotten there in my p chem course so I'm trying to use what we have been taught.

Is Gibbs free energy only for closed systems? How do I account for mass exchange when calculating how much work a system is capable of doing?

I was doing questions on Brayton cycle and there they considered the variation. So far everything I learned assumed calorifically perfect gas.

Hi guys,

I'm back again. I'm captioning an instructor that can be tough to understand with her accent. I usually can google quickly and figure out what she's saying. I'm having trouble making out what she's saying when discussing vapor/liquid phases. Sounds like she's saying isoflat and the other term is something that sounds like LEM or LEN. Maybe she's referring to a symbol? Thanks for your help! Here's the portion of transcript below:

"Okay, I think we have time to discuss one more concept before we leave today. Questions at this point? Okay, and on this topic we will learn how to determine the amount of vapor and liquid that are coexisting, so suppose we have component A and that component will have some liquid and some vapor as we are boiling things and as they are coexisting, they are coexisting inside this region here, so inside this region here there are some amount of liquid and some amount of vapor.

How do we find out how we estimate how much of A is vapor and how much of A is liquid? We are going to introduce a new term, isoflat. This one has a constant composition, so this is called isoflat, the same composition of the mixture except that what happens on this line? Temperature is varied. If temperature is varied now you're varying the amount of liquid and vapor in the system. So we can estimate the amount of vapors in liquids by this equation here. Number of moles in the vapor phase times the [AUDIO UNCLEAR] closer to the liquid phase and equal to the number of moles times the LEM closer to the liquid phase, so this gives us the ratio of the number of moles in the vapor phase over the number of moles in the vapor phase and that is equal to the LEM, closer to the liquid phase, divided by the LEM, closer to the vapor phase.

So I have a crazy theory and I want to run it by someone.

I had a crystalization lab (ikik not directly thermo but its thermo related I promise)

So basically we cooled a solution to induce crystallization, but the lab assistant didn't really know if we were supposed to stirr the solution or not. He told us to turn on the stirrer once we already had started the cooling during the experiment and then told us to turn it off because he made a mistake oops. Stirring period is highlighted in grey.

https://preview.redd.it/hit62wxivryd1.png?width=717&format=png&auto=webp&s=53e7aea764eb7aad837d5760f972ff5e59bed1f1

I've already explained why the temperature spiked:

- mixing of colder water on the outer areas near cooling jacket and location of the temperature sensor

Also explained why the concentration spiked:

- increased homogeneity of the solution and location of conductivity probe

- breaking apart of metastable clusters due to stirring but also temperature spikes

Now that im trying to explain why the concentration dropped so fast during the stirring even before the nucleation temperature, i have the obvious:

- stirring breaks up metastable clusters and increases mass transfer of molecules towards clusters.

Here's my theory: whats if additionally the decrease in enthalpy in the solution from the the spike in temperature in combination with the increase in entropy caused by the dissolution of metastable clusters induces nucleation?

overall gibbs free energy decreases that way (dG=dH-TdS) and could lead to nucleation right?

ps. yes i know the data suggests an issue with the conductivity probe lol but surely this doesnt have a lot to do with it