Why does energy have a direct proportionality with temperature, and whereas the temperature has various application based relations with different fundamental physical units,
like for example the Q/t=kA(∆T/d), and Q=k_b*∆T , and E=σT^4 , KE=3(k_b*T)/2 ,
also for entropy etc,
what i am really trying to learn is how is energy different , one such answer i got from
the internet is "Temperature is a measure of the average kinetic energy of particles in a substance, while heat refers to the total energy transferred between systems due to a temperature difference. Heat flows from a hotter object to a cooler one until thermal equilibrium is reached ." and the distinguishing factor between these has confused me,
"

1. Nature of Quantity:
   • Temperature is an intensive property: It does not depend on the amount of substance. For example, a small and large pot of boiling water can both have the same temperature.
   • Heat is an extensive property: It depends on the amount of substance. The total heat energy in a larger pot of boiling water is greater than that in a smaller pot.
2. Energy Transfer:
   • Heat flows spontaneously from a higher temperature body to a lower temperature body until thermal equilibrium is reached. The flow of heat can be described by Fourier's law of heat conduction, which states:

• Q=−k⋅A⋅ΔT/d,
• Temperature is an intensive property: It does not depend on the amount of substance. For example, a small and large pot of boiling water can both have the same temperature. by this do you mean , that the temperature does not depend on number of particles, rather , the particle's nature, and the heat contributes due to all existing particles and and their properties...
• if it were particle nature then would it be this way?,
• "Particle Nature: The temperature of a substance reflects the average kinetic energy of its particles. It is a measure of how fast the particles are moving, regardless of how many particles are present."
• "Heat Contribution:
• While temperature does not change with the number of particles, the total heat energy in a system does depend on the number of particles and their specific properties (like mass and specific heat capacity).
• The heat energy of the system is the sum of the kinetic energies of all the particles, but the temperature remains constant for a given state of matter."

my simple question is are these all analogies correct ,
if yes then, then
would it mean the 'Temperature' is an intensive property due to average KE of particles,
and their nature , by this i also mean system's nature, or rather an intrinsic property of
energy of the system,
and heat is total KE of the system contributed by the particles and their particle nature,
and other properties of system which add up to be energy ,
is my understanding or explanation correct on this,
please guide me further because i am new to this field and enthusiastic about
these fascinating things, it would be great help if somebody could explain me these things in a proper format, so i could learn and understand it better,...

Hi everyone, are there any real differences between these two textbooks? I'm studying mechanical engineering and I was looking for an heat and mass transfer textbook, only found the Principle's one in my Country. Thank you.

Years ago, I had a colleague that insisted that painting the inside walls of a sealed box black would increase its thermal conductivity. I can’t remember his reasoning for this.

There is no visible light inside the box, of course, but maybe there is something else going on?

Suppose you have a fully enclosed six sided sheet metal box, with a power supply or some other heat source inside. The goal is to keep the temperature inside the box as low as possible. Ignore the insulative qualities of a layer of paint. Would painting the inside of the box ever help? Would the color of the paint matter?

Hello, I have a Bubble T - VLE problem where I need to implement the UNIFAC model to determine the activity coefficients and find values of T and Y as I vary the values of X and keep the pressure constant. My system is the binary mixture (1) ETHANOL + (2) CYCLOHEXANE, and I must account for ALL the non-idealities in both phases (liquid and vapor), meaning I need to calculate the fugacity coefficients (using the Virial equation truncated at the second term), POY, and activity coefficients (gamma). I am doing all of this in Excel. I have already implemented the entire UNIFAC method in the spreadsheet, but the issue is that I cannot find an objective function to solve the vapor-liquid equilibrium problem (I cannot find consistent values for Y and T using Solver). plss, if anyone can help me

Say you got state 1 before the compressor, and state 2 after the compressor. The work W is then given as:

W = m(h_1 - h_2)?

I see sometimes my professor switches it up and says h_2 - h_1.

For example I had an exact problem in an exam where I knew the W in kW, h_1 and needed to find h_2. Again:

W= m(h_1 - h_2), solved for h_2:

h_2 = h_1 - W/m. But my professor got h_1 + W/m.

(I did the same for the turbine on the other side of the cycle, and got correct)

Can someone explain?

I work with large industrial engines and we often do cogeneration for heat and electricity. On our larger units we can have up to 871 m3/min of exhaust at 475C which is a lot of waste heat/energy.

On some sites they do not have the need for the excess heat so we dump to atmosphere. Specific to these sites, if we were to use a heat exchanger and run the resultant steam through a turbine attached to a generator, what kind of losses in energy would we be looking at aka how much electricity could we produce?

I’m assuming we’d be in the 500ekW to 1000ekW range but I’m having a hard time finding steam turbines small enough to get some efficiency data on.

Thoughts, recommendations, advice?

Hi everybody. I hope I can reach someone with this post. I am currentky working on a thesis about the cooling systems used by space suits for my bachelor degree in aerospace engineering. At the end I need to calculate the diameter of a collection of square pipelines to exchange approximately 800W. The pipelines have to stay inside a square plate which is 0.24 x 0.24 square meters. The fact is that when I try to calculate the diameters (which for sure have to be less than 0.24 meters I obtain a diameter of 3 meters). I am adding my calculus papers. Can someone help me?

Hi, i found this statement in a book "The efficiency of the Carnot cycle is greatly affected by the temperature T1 at which heat is transferred to the working fluid. Since the critical temperature for steam is only 374°C, therefore, if the cycle is to be operated in the wet region, the maximum possible temperature is severely limited." What does this mean? Isn't the critical point of water is 374 C only at 220 bar pressure? Why is this a constraint to Carnot's cycle if it usually operates way below this pressure?

If we have a hot solid metal sphere in open air, it will cool by natural convection. In this case we can find the heat transfer rate Q' by 1) estimating the Rayleigh and Prandtl numbers at the film temperature, 2) using a correlation to find the Nusselt number, 3) finding the surface heat transfer coefficient h, 4) Q' = hA * (T_surface - T_env).

Now, if the sphere is a good thermal conductor, as you would expect of a metal, its Biot number will be very small, and its temperature will change uniformly. So you could then say that T_surface = T (of the sphere), and say mc dT/dt = hA * (T_env - T) to find the temperature evolution. The thermal time constant will be mc/hA.

However, what if the sphere cannot be assumed to cool uniformly? The thermal resistance of a solid sphere from the centre to the surface is undefined so we can't use steady state analysis. The only way I can think of then is to solve the heat equation in spherical coordinates (only the radial part is needed though). But then, the boundary condition seems tricky. It would be a Robin-type boundary condition: -Q'/A = |∇T| -> dT/dr = h/λ * (T - T_env) at r = r_surface. I'm not sure if there is any analytic solution.

What I'm really interested in is the temperature at the centre of the sphere. Is there any better way to do this?

I have an electric dirt bike with a very large plastic wrapped lithium-ion battery. Would getting a winter insulated cover (similar to winter coat material) be sufficient to keep the bike above 40°F in as low as 5°F weather for long term winter storage? Or will the temperature outside eventually equalize with the insulated bike? Help would be greatly appreciated. I'm very new to thermodynamics.

Container 1 has volume V1​, and inside that container there is a number of moles n1​, temperature T1. Container 2 has volume V2​, and inside the container there is a number of moles n2, temperature T2. The gases in Container 2 are transferred adiabatically to Container 1 mixing both gases. What is the pressure and temperature​ inside Container 1 after the mix of those two gases?

Hello! I'm stuck on a calculation that requires me to determine C*pm (Dimensionless heat capacity). I know that I need to use the formula:

(T2/T1)=(1/π)^(n/C*pm)

and somehow iterate to find T2s by guessing and testing its value. The correct C*pm​ should be about 3.55 (according to the lecture material), but I keep getting 3.687.

Initial values:

• T1=616  (air temperature before the turbine compressor)
• P1=1 bar (air pressure before compression)
• P2=12.4 bar (air pressure after compression)
• η_isentrop=0.89 (isentropic efficiency)
• m_flow=120 kg/s (air mass flow rate through the compressor)

ChatGPT gave me some integral methods (which I tested and got the same Cpm=3.687), but the correct method should involve guessing T2s​ and iterating until reaching a consistent value. I'm a bit lost here because the lecture materials don't explain the iterative method clearly. Any tips?

Edit: T2s refers to the temperature under the same entropy but with a different enthalpy.

Edit2: Correcting my bad grammar

Hail mary but figured worth a shot.

Situation: creating a small water chiller system.

Issue: may have gotten in over my head - been entirely self-taught and been constantly learning, hopefully someone more knowledgable can help me out.

Details: sort of replicating a water chiller system with my own parts, but ran into issues when charging.

My system: a LBP/MBP R134a compressor, mini tube fin condenser, 1/8” OD capillary tubing as metering device, 40 plate BPHE, and 3/8” suction line. Using a freon scale to monitor freon charge.

Was advised I needed to get: suction saturation, liquid saturation, superheat, subcooling, water temp approach, and metering device type.

How can I obtain this data and calculate how to charge system with freon?

Hopefully looking for an engineer or expert that can help, even better if any in my area. Thank you so much for your time!

This is a compressor power formula.

https://preview.redd.it/lrokfia0mq2e1.png?width=980&format=png&auto=webp&s=686a91dd9305f73af0074bd3241fb4554ec16521

I think that T1 should be P1

Q is volume flow through compressor m^3/h or whatever units are used here.

PV=wRT (2.7)

V=(wRT)/P

This is from a different source:

https://preview.redd.it/p41x7ptbmq2e1.png?width=693&format=png&auto=webp&s=781ac84ea83b89727e410bb2db00b2215c0415f5

What confuses me is that the first equation is in imperial units and is supposed to be a real compressor formula. Other 2 formulas are soposed to be thermodynamic and theoretical.

I can't figure out which textbook this was taken from. Anybody recognize it? Thanks.

https://preview.redd.it/2wadum8pih2e1.png?width=1566&format=png&auto=webp&s=8f0e9ef85c76d3264b9c23707f6368255d9f9526

A few months ago, there was the announcement that 'polymetallic nodules' (basically high-entropy alloys) at the bottom of the ocean (the Clarion-Clipperton Zone) could produce oxygen gas, which had pretty big implications for biology. The paper hypothesised that the mechanism of oxygen production was electrolysis of the sea water, as a voltage of up to 0.95 V was measured across the nodules.

Some have contested this claim - such as in this response. Unfortunately, there is some competing interests on this topic, since deep-sea mining companies want to refute the claims so they can keep mining the nodules, as their metals are used in Li-ion batteries for example. The most obvious criticism I can think of is that the measured maximum of 0.95 V is not enough to generate the minimum of 1.23 V for water electrolysis. We should also consider some additional facts:

• The 0.95 V figure was the maximum they found, most of them were much smaller, around the range 0.3 V.
• The Gibbs free energy change would be even more endergonic at the high pressures found at the bottom of the ocean, raising the 1.23 V figure higher.
• An overpotential of about 0.37 V is required for seawater electrolysis at pH 7.4 found at the site. However the metal surfaces can act as catalysts for the reaction, reducing this overpotential significantly.

Surprisingly, barely any papers have been published on this topic ever since that July 2024 paper in Nature.

Do you think it's unlikely that electrolysis is occurring here?

I need to design it aesthetically but I'm confused with how could you make this work. Mantaining a volume of no more of a 10% additional of the space which a refrigerator should fill. Please I'm a noob in thermodynamics 😔

I see the first law written as Q+W=U and Q-W=U. I’m pretty sure it’s a directional thing, but if someone could explain this to me I would really appreciate it!

Hi fellow engineers. I've been assigned prob. 10-62 to solve with MATLAB, and i'm confused. As you can see, this is about an ideal diesel cycle using air as it's working fluid. I'm also specifically told to use refprop along with matlab, which is basically an equivalant to EES. But here is the thing: we use ideal gas formulas to solve such problems. We don't use anything from the tables. We can look up the fluid in different states and find details such as h or v, but i don't see how they could help solving the question. I already asked about this from my proffessor and he just told me to "pay more attention". So here i am, can anybody help me? What am i missing?

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%