Thermal Definition and 1000 Threads

I can't understand how both the material and the scale's expansion are being taken into account at the respective temperatures. Please explain the concept in detail.

I am quite confused. I know about the continuity equation, for instance ##\frac{\partial \rho}{\partial t}+\nabla\cdot \vec J = \sigma##. In steady state, ##\frac{\partial \rho}{\partial t}=0## which implies ##\nabla\cdot \vec J = \sigma##. In words, the divergence of the vector field ##\vec J##...

Hello Dear Experts. I need help with the calculation of total thermal power in nuclear reactors. Can someone explain the general mathematical approach or provide useful formulas for this calculation? Thanks!

Hello! I have a 2-level system, with the resonant frequency ##\omega_0## in a thermal bath, by which I mean that I have photons with mean frequency and standard deviation of frequency at a temperature ##T## given by: $$<\omega> = \sigma_\omega = \frac{\pi^2}{6}\frac{k_B T}{\hbar}$$ I can...

I am considering installing a radiant barrier in my attic to reduce the thermal load on the A/C in the summer. The radiant barrier will only help me if it is at a lower temperature than the roof, once its at the same temp at the roof, it just becomes an equivalent radiator into the interior of...

I've been working on this problem for the past 3 days. I have other papers with different ways of tackling the problem. However, I just cannot get to the answer (change in entropy = 2Nlog(2)).

Hello folks, I have a new different design of solenoid valve and would like to evaluate heat generation in the system. I am a mechanical engineer and might have less understanding of electrical components. Just trying to understand, the solenoid valve will have heat generation due to current...

I've seen this math also in a lecture once. It seems very vague to me. Here is the relevant part of the book ##F_1## and ##F_2## are introduced as seen above. There is, as far as I can tell, no previous mention of them. Why does ##F_1(P_A,V_A,P_B,V_B)=0## signify thermal equilibrium...

I was watching some videos about aircraft performance and found a common theme - rapid or sudden cooling - of piston engine heads (there is some disagreement/controversy on the subject) or turbine stators, leading to component or performance failure. The Focke-Wulf Fw 190 A-4 had a performance...

Suppose I have a mechanical stress tensor \sigma. Say I have the stress tensor for viscous flow: \boldsymbol{\sigma}=-p\mathbf{I}+\frac{1}{2}(\nabla\mathbf{u}+(\nabla\mathbf{u})^{T}) If the thermal flux is given by \boldsymbol{\sigma}_{th}=\alpha T\mathbf{I}, so I have a total flux as...

Hello, I'm looking for information on materials used in the nozzle thermal protection. In particular I'm interested in a protection made by different layers, an inner/outer lining, a conductive and an insulating layer, whitout rigenerative/film cooling. I would like to know typical mateials used...

If neon is stored at 40 psi . 65 degrees fahrenheit. How do i calculate the psi in a closed system when the container is heated.

Hi, Can I get help ranking Copper, Brass and Bronze by Thermal Conductivity? This stuff below says Copper is the best Thermal Conductor, and Bronze is the worst. https://en.wikipedia.org/wiki/List_of_thermal_conductivities https://www.engineersedge.com/properties_of_metals.htm...

This question is mainly for @A. Neumaier, but I post it in public in case others are interested. The usual reason given for needing to quantize gravity is, heuristically, that, in the presence of quantized stress-energy where there can be a superposition of different stress-energy tensors...

What could be most sensible parametre for atmospheric escape excluding higher order (and nonlinear!) effects? Black body radiation is proportional to fourth power of temperature. Therefore temperature of black body is proportional to 4th root of incident radiation. Radiation from a point source...

Hello, I have been reading that a coal power plant and a nuclear power plant have similar efficiencies, i.e. ~30%. This 30% refers to the conversion of thermal energy into electricity. For example, for 100 Joule of thermal energy, we only get 30 Joule out of electrical energy. How is that...

I have two concentric thick cylinders in close tolerance (currently 50 micron gap), with a thin layer of glue between them. Internal cylinder is made from steel and external cylinder is made from ceramic (so the thermal expansion coefficient is not the same) The assembly is headed form inside...

Hi all, I’ve run into a number of paints that are sold as “thermal” paints, or insulation paints. I know it’s mostly bs, but want a clarification on how emissivity and infrared absorption relate. The salesperson says the paint surface has an emissivity of 0.91, and reflects 99.5% of infrared...

Hello, I want to learn how to design a spacecraft's thermal protection system. But I don't know where to start. Someone can help me?

Just wanted to know if I was barking up the wrong bush or not with my working out if anyone could help?

I'm curious as to why the average power is not negative in this scenario, since I thought the friction force is in the opposite direction of velocity. As far as I see friction force is the only acting force in the problem, but I may be wrong. I solved this by simply doing (Friction Force *...

How can i detect the thermal neutron, E = 0.025 Ev, by MCNP using CUToff Or PHYS:N cards?

Hello, assuming to keep an aluminum alloy motorcycle frame not in use, still, will the daily temperature variations cause thermal fatigue due to the continuous expansions and retractions or is the force developed by a few degrees of variations not sufficient to create microstructural dislocations?

I have a charged particle in a Penning trap. The particle motion is non-relativistic and the energy is high enough such that we can assume it is not in the quantum regime. For the purpose of the question I am interested only in the axial motion of the particle, so basically this is a classical...

There is heating of the surface of the material using an electron beam. It is necessary to calculate how much heat will be released and build a graph of dependence. Please tell me how this can be done, which modules in COMSOL can be used?Thank you!

Hello! I have a 2 level system with a dipole moment d. I want to simulate numerically the evolution of the system under an external sinusoidal electric field (far off resonant). This is straightforward using SE. However I also have on top of that another electric field, created by a coupling of...

LBM model for phase change- relevant equations found here. Also here. #Thermal LBM #solves 1D 1 phase phase-change #D2Q5 Lattice nx=100 # the number of nodes in x direction lattice direction ny=5 # the number of nodes in y...

What'd be practical method and/or portable, simple tool (like sort of electricians' multimeter) to meter the heat conductive constant of a metal?

For this problem, The solution is, I understand their logic for their equation, but when I was trying to solve this problem, I came up with a different expression: ##\Delta A = \Delta L_x\Delta L_y## ##\Delta L_x =\Delta L_y = \Delta L## since this is a square. ##\Delta A = \Delta L^2##...

Hello, I want to model a thermal battery based on phase change materials (PCM). It is a plate heat exchanger immersed in a PCM bath. The diagram is given in the attached file. I want to determine the temperature at each moment and from everywhere in the battery. The hypotheses are the...

In screenshot below, systems A and B are separated by an adiabatic wall initially while each of them exchanges energy with system C via a diathermic wall. Once A and B reach thermal equilibrium with C, then A,B are allowed energy exchange via a diathermic wall, and energy exchange between A and...

The farthest I got was double thermal energy equals mass times specific heat capacity times change in temperature (115+34) 2Eth=(mc149) To Eth=mc74.5 I'm not sure where to go from here. It seems like I don't have enough information.

"Heat is the transfer of kinetic energy between molecules. If the velocity is more, the kinetic energy will be more so that the heat is more." "As an object's speed increases, the drag force from the fluid increases exponentially. For example, when you drive at high speeds, the frictional force...

Greetings everyone. I learned that the distance between molecules in liquid increases while the temperature increases. Hence, its density is decreased. The process is thermal expansion. At the same time, the collision between molecules would be more frequent when the temperature increases...

What's the mechanism underlying the correlation between electrical & thermal conductivities in metals ?

I am interested in the potential for air bubbles in a plastic structure to expand with heat, and put pressure on the plastic surrounding the air bubble. In this case the plastic structure is formed by melting a thermoplastic powder. In between the grains of powder are voids with air in them. As...

Hi, I'm trying to solve a problem involving radiation in a triangular cavity: As you can see, lengths and emissivities of all surfaces are given. For two of them, the heat flux is known and the temperature has to be found while for the remaining surface it's the other way around. I have the...

https://en.wikipedia.org/wiki/Wien's_displacement_law "Maxima differ according to parameterization ... Using the value 4 to solve the implicit equation yields the peak in the spectral radiance density function expressed in the parameter radiance per proportional bandwidth. (That is, the density...

Im not really sure how to answer this question. Would you have any ideas?

Q=Qwarm water+Qsteam Q=mct+mLv Q=(8kg)(4200J)(100C-25C)+(2kg)(2.3*10 to the power of 6 J/Kg) Q=7.12*10 to the power of 6 J Is this the correct answer?

Canonical ensemble can be used to derive probability distribution for the internal energy of the closed system at constant volume ##V## and number of particles ##N## in thermal contact with the reservoir. Also, it is stated that the temperature of both system and reservoir is the same, i.e...

My sign doesn't check out and I don't get why that'd be the case. Forces that act --> ##F_{fr} and F_g## derivation: ##\Delta K = W_{NC} + W_C (1)## ##\Delta K + \Delta U = W_{NC}## ##\frac 12 mv_2^2 - \frac 12 mv_1^2 + mgy_2 - mgy_1 = W_{NC}## NOTE: ##y_2## assumed to be datum line so ##y_2 ==...

Hi, Has anyone experience with photovoltaic solar panels and thermal radiator type solar panels? 1/ How do they compare when both have the same collection area? If the thermal radiator was much smaller than the collection area, and a lens the size of the collection area was used, focused on...

High-power electronic subassemblies – housing CPU or power-conversion semiconductors, for instance – require significant thermal dissipation to keep their chip-junction temperatures at or below their maximum operating temperature. (As a rule-of-thumb, every 10oC increase in junction temperature...

As per the title, I'm trying to research how the thermal breakdown (thermolysis) of water works. I gather that you need circa 3000°C to get it to break down, which is a lot, and I'm curious as to how pressure might affect this. I know that pressure affects the boiling point of water, and as...

I've built an insulated chamber to protect a sensitive instrument at freeze temperatures in the winter. The instrument is mounted on a telescope, so the heat inside the chamber will slowly dissipate in the ambient. A digital PID thermostat is used to keep the temperature at a safeguard level...

so I have never seen this unit before. 10^-6m/mK for the thermal expansion (linear expansion). I believe this unit is micrometers divided by mili kelvins?

Summary: I think I found the solution at the end of the post, posting in case someone has a better idea. I plan on going shopping somewhere a bit distant because my local supermarkets dropped the majority of store brands. I suspect the whole trip will take 90-120 mins. I have a deep freezer...

Hello, I'm confused between the difference between the thermal and mechanical efficiency of a Sterling heat engines or heat engines in general. I hope you could be able to guide and help me. Thank you

Hello Everyone, I have a thermal imager and I am interested in better understanding night vision (NV) technology. Apparently, NV goggles respond to NIR and SW See this article. NV goggles can see from the near infrared (NIR) to the shortwave infrared (SWIR) portions of the light spectrum. Do...