Thermal Definition and 1000 Threads

A thermal column (or thermal) is a column of rising air in the lower altitudes of Earth's atmosphere, a form of atmospheric updraft. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example of convection, specifically atmospheric convection. The Sun warms the ground, which in turn warms the air directly above it. A thermal is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically.

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  1. Grinkle

    Construction Can a radiant barrier in the attic be effective?

    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...
  2. B

    Thermal Physics Kittel chapter 6 -- Entropy of mixing problem

    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)).
  3. jmex

    Solenoid valve thermal part

    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...
  4. Z

    Chemistry How to understand the zeroth law through these specific equations?

    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...
  5. Astronuc

    Thermal effects in aircraft engines - sudden/rapid cooling

    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...
  6. H

    A Thermal stresses in the stress tensor

    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...
  7. J

    Rocket nozzle thermal protection

    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...
  8. K

    Help with Calculation: Thermal Expansion of Neon

    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.
  9. Fishworks

    Rank Copper, Brass and Bronze by Thermal Conductivity

    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...
  10. PeterDonis

    A Gravity in the Thermal Interpretation

    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...
  11. S

    I Atmospheric escape parametre statistics

    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...
  12. F

    I Nuclear power plant vs coal power plant efficiency

    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...
  13. ATT55

    Stress in cylinders due to thermal expansion

    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...
  14. gmason85

    I How do emissivity and absorptivity affect thermal imaging results?"

    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...
  15. V

    Designing a Thermal Protection System for Spacecraft: Where to Begin?

    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?
  16. D

    Engineering Thermal expansion of oil overflowing from a tank

    Just wanted to know if I was barking up the wrong bush or not with my working out if anyone could help?
  17. yashboi123

    Why Is Average Thermal Power Not Negative in This Friction Scenario?

    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 *...
  18. Islam Nabil

    Thermal neutron detection using MCNP

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

    Is Thermal Expansion Fatigue a Concern for Aluminum Alloy Motorcycle Frames?

    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?
  20. K

    A Measurement uncertainty due to thermal noise

    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...
  21. Engineer_Kosyakova

    Engineering COMSOL plot of thermal radiation from heated surfaces -- Help please

    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!
  22. K

    A Two level system in a thermal noise electric field

    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...
  23. Gwen

    Python Thermal lattice Boltzmann model ignoring source term -- python code help please

    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...
  24. abdulbadii

    Measuring thermal conductivity of a metal

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

    Thermal expansion of square from temperature increase of 50K

    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##...
  26. D

    A Heat exchange in a thermal storage based on phase change materials

    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...
  27. V

    B Heat exchange after thermal equilibrium

    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...
  28. lxhull

    Doubling the Thermal Energy of a Frozen Chocolate Bar

    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.
  29. mathbrain9

    Link between increase in Potential energy and the thermal energy lost

    "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...
  30. L

    B The collision of molecules during thermal expansion

    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...
  31. B

    A Electrical & thermal conductivities

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

    Thermal expansion of air bubbles in plastic

    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...
  33. FEAnalyst

    Triangular cavity thermal radiation simulation

    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...
  34. Conn_coord

    I The CMB has a thermal black body spectrum

    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...
  35. P

    How does energy affect the melting point of water?

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

    Is the Calculation of Thermal Energy in Mixing Water and Steam Accurate?

    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?
  37. Dario56

    I Concept of Thermal Equilibrium in the Context of Canonical Ensemble

    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...
  38. S

    Thermal energy dissipated from the brakes in a car

    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 ==...
  39. camerart

    Photovoltaic vs. thermal radiator Solar Panel comparison (using a lens)

    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...
  40. C

    I Simple model of thermal shape fluctuations of liquid interface

    Consider a container filled with two essentially incompressible liquids with densities ##\rho > \rho'## and (respective) volumes ##V##, ##V'##, rotated by a centrifuge in some orbit-based space lab to maintain a roughly constant (co-moving) simulated "gravitational field" g. Let's suppose that...
  41. Solid-Statist

    Thermal Dissipation of High-Power Electronic Subassemblies

    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...
  42. S

    I Does pressure affect the thermal breakdown of water?

    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...
  43. Erwinux

    I Calculating the thermal coefficient between the insulated interior of a telescope instrument package and the cold ambient air outside

    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...
  44. kasnay

    Question about these thermal expansion coefficient units (m/mK)

    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?
  45. D

    I Is it cooler hanging ice packs from a fishnet bag or in a thermal lunch-bag?

    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...
  46. Poorneshwar 2

    I Difference between the thermal and mechanical efficiency

    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
  47. F

    Night vision technology vs thermal imaging

    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...
  48. G

    I Interpreting Thermal Power in Cylinder with Source & Sink

    I have a cylinder that is separated with an insulator. In the internal cylinder there is a thermal source, while outside the insulator we have a thermal sink. The power of the internal cylinder is positive, while of the external one in total is negative. How I should interpet the results. Like...
  49. T

    I What are thermal fluctuations?

    I often think thermal fluctuations as random changes in the temperature but when it is said in the context "thermally fluctuate over the energy barrier" does it mean to classically overcome the barrier?
  50. A

    Lithium hydroxide from Li-7 as used in thermal reactors

    So I read that lithium hydroxide made from Li-7 is used as an anti-corrosion additive in light water reactors purely for the "longevity" and "well being" of the vessel and structural auxiliary elements like steam pipes etc. Lithium separation is a rather chemically "nasty" task if using the...
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