https://preview.redd.it/6qgzdca2a2xc1.png?width=1075&format=png&auto=webp&s=1bed05e46978fabcf16e9f1c2f94b9fbba33b3e1

I have this entropy equation that I derived from peng-robinson equation of state
Trying to prove the fundamental postulate that says: A system entropy approaches zero as the temperature reaches absolute zero - S(@T=0) = 0
But looking at the equation, ln(Z-B) when T=0 is infinity, also ln(U/U_0) when plugging in the relation between u and T is infinity.
I'm sure that I'm missing something here.

I have a steel plate with cooling channels in it, i know the temperature of the plate, size of the channels, water flow, pressure and the temperature of the water coming in.

The question is how do I calculate the temperature of the water coming out?

I’m trying to do this, so i can calculate how much cooling power i need to install into the water reservoir that keeps the water for recirculation into the plate.

And also can someone direct me to some good lectures on the topic, because it has been only 2 years since i got my degree and don’t remember anything about thermodynamics, besides Q=c m dt.

I'm trying to determine the exact time it takes for a cup of tea boiled at like 100 Celsius too cool down to like 70-60 Celsius. Originally I was planning on using 2nd law for to find it but google said to use the Law of Cooling. I am confused on how they derived the law of cooling from 2nd law.

The problem states, “A rigid tank contains 8.5 kg of saturated water mixture at 500 kPa. A valve at the bottom of the tank is now opened, and liquid is withdrawn from the tank. Thermal energy is transferred to the steam such that the pressure inside the tank remains constant. The valve is closed when no liquid is left in the tank. A total of 5 kJ of thermal energy is transferred to the tank, determine (a) the quality of the steam in the tank at the initial state, (b) the amount of mass that has escaped, and (c) the entropy generation during the process if thermal energy is supplied to the tank from a source at 550 °C.”

Hey guys!

First I have to confess that I am an engineer who has forgotten almost everything about thermodynamics since I dont need any at my job, so please dont judge me too hard....

I am currently building a immersion cooled mini PC in a nano cube aquarium filled with mineral oil. I know that it is a stupid idea but I wanted to do this the past 20 years and I finally have a usecase that kinda makes sense.

I have been measuring power consumption of the mini PC for the past 2 days and it is running at an average of 35 W with peaks of 40 W. Since the PSU and HDDs are staying outside of the tank I would guess we are talking about an average load of 30 W.

The tank is 25 x 25 x 30 cm but will only get filled up to 25 cm. Since the tank has a cover on top with a stagnant layer of air inbetween I would have only calculated the 4 walls for heat exchange.

My room gets up to 28°C in the summer and the oil should stay below 60 °C while 50°C or lower would be better.

Summary:

Medium in tank: Mineral-Oil

Medium of tank: Pyrex 5 mm

Medium outside: Air at max 28°C

Load inside tank: 30 W

Surface for heat exchange: .25 m²

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Would be great if you guys could help me out!

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Hi i'm making a neural network ( ann ) to predicate the thermal conductivity of SiO2/water–ethylene glycol (50:50)

hybrid nanofuid for example with the inputs of Volume fraction (φ) and temperature (T)

where can i find a dataset that contains information about the thermal conductivity of nanofluid at specific Volume fraction (φ) and temperature's (T)

like should i search for research papers regarding the specific nanofluid or is there a website

(Open problem)

**Problem:**

I need to study a single concentric tube heat exchanger (air-air). I'm looking for the outlet temperatures.

I have all the other relevant parameters.

To do this, I divide it into a succession of small dX sections in which I assume a linear temperature evolution in each section.

The aim is to find a result close to the usual methods (NTU or LMTD)

**Givens/Unknowns/Find:**

* "Given: " Fluids caracteristics, mass flow, inlet temperatures, heat-exchanger type and geometry

* "Unknown: "Outlets temperatures

* "Find: "Outlets temperatures

**Equations and Formulas:**

Q=m*cp*Delta(T)

dQ=U*Delta(T)*dA

with U the overall heat transfer coefficient, A the surface area of the transfer

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I think i need to assume a first linear temperature distribution for the one of the fluid (for example the cold one) then i must calculate for each section of the hot fluid the correspond temperature thanks to relevants equations and then pass again on the cold fluid then the hot and so one until i get a consistent temperature distribution along the exchanger. But my results are inconsistants, i'm really not confidents with the equations i'm using

Hi guys maybe you can help me i think i miss the forest for the trees.

i need to calculate the thermal capacity of a Methan - Hydrogen mix

75-Vol% Methane. 25-Vol% Hydrogen

Density Methane: 0,83 kg/m^3
Density Hydrogen: 0,09 kg/m^3

Density of the mixture rho_b = 0,75 * 0,93 + 0,25 * 0,09 = 0,645 kg/m^3

Now i need the mass fraction of Methane and Hydrogen to calculate according to this Formula:

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https://thermtest.com/thermal-resources/rule-of-mixtures

Mass Fractions:

0,75 * 0,83 kg/m^3 = 0,6225 kg/m^3 m_1 = 0,6625 / 0,645 = 0,965

0,25 * 0,09 kg/m^3 = 0,0225 kg/m^3 m_2 = 0,0225/0,645 = 0,035

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c_p_methane = 2,21 kJ/(kg*K)

c_p_hydrogen = 14,2 kJ/(kg*K)

​

c_p_mixture = (0,965/1) * 2,21 + (0,035/1) * 14,2 = 2,63 kJ/(kg*K)

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However, if i calculate the c_p according to this website:
https://thermtest.com/thermal-resources/rule-of-mixtures

i get c_p_mixture 5,2 kJ/(kg*K) wich is the c_p calculated with the volumetric fractions (wich is incorrect in my opinion)

can someone validate my calculation or correct me?

Thanks in advance!

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I wanted make this post because everywhere I see this question and answers, in my perspective it is completely wrong. The answer in every version I seen, it is -136.58 degrees Celsius, because the Kelvin scale, -273 and all. But as we people with thermodynamics knowledge need to address a more sensible solution. If I said two times colder, it doesn't mean you gonna freeze to death in seconds.

No, the concept of coldness, hotness should be taken in consideration in respect to objects. Thus, in our question, we obviously mean that it is cold for "us", humans. Human skin is approximately 34 Celsius.

The heat loss (Q) can be calculated as:

Q=h⋅A⋅ΔT

where ( h ) is the heat transfer coefficient, ( A ) is the surface area, and ( delta T ) is the temperature difference in Kelvin.

We need to obviously make an assumption, because what is a problem solution without an assumption even lol. So since the question has no information of the state of air (wind, humidity etc.) we will assume heat transfer coefficient is the exactly same. Since human skin surface area will obviously be also the same for each person, the only value that will change is the temperature difference. We said the environment temperature is 0 Celsius. To temperature difference with human skin is 34 Celsius. Double the coldness, thus heat loss, the difference shall become 68 celsius. Thus tomorrow it is -34 Celsius.

Of course, we could refine the calculation further by considering that heat transfer for the human body occurs not only through convection with the environment but also through radiation. If we assume that sunlight exposure remains constant while other parameters change, the final temperature value would be slightly different. However, this solution is still more sensible than saying -137 Celcius.

What do you guys think?

Iam looking to advance my understanding of Thermodynamics. We used thermodynamics an engineering approach for my class but iam looking for something more advanced Any suggestions?

Hi there, I am wondering how the field of Thermodynamics will change after combustion processes become fewer and fewer. I am thinking about specializing in this field as ME, but I see most research on topics such as

• some analysis of injection of fuel in ICEs
• multiphase pumping for a more profitable opertion of gas and oil mining sites
• more efficient gasification and condensation of heavy oil

This somehow feels outdated to me, especially as I am from Germany, where there is a strong drive towards electrification and use of renewables. Nuclear and gas will not be part of the energy grid in future. I support this move (apart from nuclear). I really care about climat change and I am thankful for anything that is being done to slow it down. But does that mean that Thermodynamics will shrink to HVAC and maybe electronics cooling? I can't see myself in only those two jobs for my entire career. Passive electronics cooling also is quite a lame job. But is that it?

I already feel like that some of our research facilites artifcially focus on H2 electrolysis, H2 combustion and power2heat energy storage. As if those solutions would be feasable in large scale. There also is very little novelty to them. They are just artificially hyped through a lot of media attention and research grants. Due to their inefficiencies, those solutions will only happen if governments constanly poor money into them. Heating water as energy storage to then drive a turbine seems about the dumbest thing to do for me.

I currently have an excel spreadsheet where I have calculated the heat transfer (I.e., the temperatures) in a set of nodes. I’m now trying to do the same calculation in Python but not sure how to go about it as I’m pretty much a complete beginner.

The calculation includes heat transfer due to conduction, convection, radiation, or some combination of the 3, as well as some internal generation on some nodes. In addition, there are various materials. The current methodology includes applying a heat balance equation and solving to obtain the heat accumulation ( temperature) within a node based on the heat coming in and heat going out (and, if applicable, internal generation). I’m trying to avoid going into too much detail because the method is complex. The key thing is that the equations applied to each node vary.

I suppose my first question is, how do I setup Python to only include the specific heat transfer mechanisms on each particular node? E.g., node 4 has conduction coming in and conduction going out, node 13 has conduction in and radiation out, etc.

I think it will involve defining equations for conduction, radiation, and convection both for heat coming into a node and heat leaving a node. Then somehow ‘telling’ python which mechanisms are applicable to each node..? But I have no idea how to actually get started because I’m a beginner.

Any advice or links to useful resources on this subject would be greatly appreciated.

Thanks

Hi everyone. I have a question regarding alternative to Thermocalc and JMatPro. My institution does not have nickel library for any of them and I would really need a constructed isopleth phase diagram for my masters thesis regarding Inconel 718. If anyone knows if there is a free alternative, I would kindly ask if someone could share the information with me. Thank you in advance!

P2 as in pressure at point 2 after Pump , I don't mean P2 as in Pump 2

Also does P6=P7 or not cause of Temperature inside boiler?

I think I got the T-s diagram wrong, and also I'm not sure about how the pressure lines go here.

I have thermodynamics exam next week. My prfoessor said I can use whatever I wnat except for communication with others so I will use ChatGPT for my exam. Is there any GPTs for me? The problems will be simple, just calculation with given conditions.

Hello Reddit community,

I'm working on an odor assessment project involving various petroleum products. I need to understand how properties like vapor pressure, volatility, and temperature change under different conditions.

Experiments are not feasible due to cost and time constraints. I have MSDS and some general information, but these only provide properties at standard conditions.

I've heard about Computational Fluid Dynamics (CFD) for modeling these properties, but I'm unsure about its complexity for this purpose. Are there simpler or more cost-effective methods? Any resources or tools for extrapolating properties under different conditions would be helpful.

Any advice or suggestions would be greatly appreciated. Thank you!

I’ve been testing TECs under very controlled conditions and can’t achieve anything close to the performance of the product specs. Running them at optimal power and conditions as far as I can tell. Any thoughts on what I’m doing wrong?

Excuse my drawing skills 😅

I’m trying to turn my garage into a working space, I recently renovated and put some nice laminate floors.

I live in Florida so in summer it gets insanely hot in the garage, so I’m trying to figure out a way to reduce it.

The picture is the front view of my garage. The yellow part is the ceiling of the garage and the blue is the roof. There’s an attic between the two. The blue part is pretty much just plywood with shingles on top, there’s no insulation.

My question is, would laying insulation above the ceiling (yellow part) reduce the heating significantly?

I know putting insulation on the inside if the roof would probably be best but to hold it up there I’d be spending more money.

I hope this makes sense

I'm currently in a Thermodynamics course for my chemistry Masters. The assignment is to "propose a new thermodynamic cycle," or evaluate one you find in the real world, and compare it to the Carnot cycle. I need to make a PV diagram and TS diagram, calculate efficiency using W/Q, and discuss how it compares to Carnot.

The diagram below shows the heat transfer fluid cooling system that is used in the plasma etching of computer chips, which is relevant to what I do for work, and both myself and my prof are excited to analyze something I have a personal connection to. However, the lack of information about the system is really challenging for me (not to mention that I'm an organic R&D chemist, not a pchemist). The data I know is listed below, but I don't know if I have enough information to calculate everything I need.

The cascading cycles are confusing me as well because I don't know the temperatures at each point and how I demonstrate this in a P/V diagram. My prof did say I can make assumptions about the properties of the fluid, such as Cpm, and about the system, such as compressor conditions, as the point is more to apply what we're learning rather than get exact values.

Maximum fluid temp: 120C (395K)
Minimum fluid temp: -60C (213K)
Cooling capacity: 10kW (10kJ/sec)
Specific heat capacity (actual value of a fluid used in this setup): 1.1 kJ / kg K
Flow rate: 0.0505 kg/s (calculated)

https://preview.redd.it/drh47x77wbuc1.png?width=3362&format=png&auto=webp&s=f439d03c1fbcf0ff083f791aafb2da813ea937c6

Process module: cold reservoir (the wafer is being maintained at a particular temperature by the fluid as heat is transferred to the wafer via plasma etching)
Cooling tower: hot reservoir?

I'm seriously struggling with this. I've spent probably 6 hours just trying to figure out what to do and I think I'm just confusing myself more and more.

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Hey, for my bachelor's thesis, I need to simulate a rotary kiln. The only software I found was Vulcano by Dynamis, but it's quite limited. I wanted to know which one between OpenFOAM, COMSOL, and Gmsh would be the easiest to use, considering I haven't used any software like this before. Also, if you could help me with tutorials or other materials for these software. Thanks!

As we know, simple systems can reach equilibrium states defined by just three measurable properties: internal energy (U), Volume (V), and the number of each molecule type (N) which can be defined with entropy function: S = S(U, V, N1, N2, ... , Nr)

I want to find the fundamental equation (Entropy) using the Peng-Robinson EoS. In order to do that, I need to solve the partial differential equation from the third postulation that I received in the image below:

https://preview.redd.it/yo4ep8w8k1uc1.png?width=572&format=png&auto=webp&s=9232f7c1fd095c155ff18631732abed654d2fb28

An example of finding the fundamental equation (Entropy) using another EoS (Van der Waals) can be seen in the image below:

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https://preview.redd.it/9hp3gsuek1uc1.png?width=683&format=png&auto=webp&s=e564f85438242c1b3d5577c91149ef8924d8805a

Could anyone please help me solving the equation on the first image and find the Entropy relation as seen in the second image?

Thank you,
Roee.

Since liquid Hydrogen has a boiling point of 20K, does that mean using it as a working fluid in a Rankine Cycle engine would give very high efficiencies for typical powerplant heat source temperatures (say 800K)? (Assuming the setup is in a perfect vacuum)

Hello there,

I hope you guys are doing good (well better than me anyways, I've been stuck in this thermo problem for like forever). I have a been asked a question in one of my thermodynamics lecture to find the speed of sound in a gas given by C= √ ( ∂ P) / ( ∂ p) where P is the pressure and p is the density, using the Maxwells equation of Cp, Cv and the Isothermal Compressibility k ?? We can also use the fundementals like Helmholtz, Gibbs or Enthalpy... but I serioulsy can't figure out where to start with as I've been just turning circle to circle by partially deriving some terms, and then ending up nowhere. Do you guys have any advice how to attack this certain problem?

Thanks again for you support, I greatly appreciate it !!!

Hi guys, just trying to figure out what an isochoric process looks like on a P-h diagram. I wish to understand what Co2 would look like when sublimated inside a rigid cylinder while heat is added. Any help is welcome Thank you

Hello Everybody,

Can you please tell me if you know any open source website where high school students can practice theory? Please let me know.

Researchers from the University of Toronto demonstrate the precise reason for an ultimate link between energy and information. Heat is related to intelligence, temperature to randomness, and entropy to uncertainty. How do all these concepts truly relate, and where does intelligence fit into the picture?

Read and find out! https://www.mdpi.com/1099-4300/26/3/203