What is Thermal: Definition and 1000 Discussions

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. G

    Is there a way to calculate thermal conduction speed or time?

    Hello. I'm working in the plasma physics and trying to calculate the thermal conduction time or speed. Thanks to the people here replied my questions, I was able to calculate the thermal conductivity of the plasma with the given electron temperature in SI unit...
  2. C

    The change in entropy of the gas vs thermal reservoir

    Homework Statement Homework Equations The Attempt at a Solution I don't know what is the difference between the change in entropy of the gas vs the thermal reservoir??
  3. J

    Thermal and Kinetic Energy Conversion

    A man is running and chemical energy converts to thermal and kinetic. The output (thermal and kinetic ) has the same amount of energy as the input (chemical). But what does thermal and kinetic energy convert to?
  4. G

    Unit conversion problem for the electron thermal conductivity

    Hello. In CGS unit electron thermal conductivity for plasma is expressed as \frac{n_{e}T_{e}}{m_{e}\upsilon_{e}}\Gamma_{1} [1] where \Gamma_{1} is the dimensionless transport coefficient. [2] You can also find similar expression in...
  5. S

    Collision of thermal neutrons and Cobalt

    Homework Statement The cross section of ##^{59}Co## for capturing the thermal neutrons is ##2000 fm^2##. A ##10g##, thin paper of ##^{59}Co## is radiated for ##100 hours## in reactor with neutron flux ##2\cdot 10^{18} /m^2s##. Density of ##^{59}Co## is ##8.9g/cm^3##. Half life time of...
  6. U

    Thermal Conductivity - Forming ice under water

    Homework Statement Part (a): Derive Clausius-Clapeyron Equation. Find latent heat of fusion of ice. Part (b): Find rate of formation of ice Part (c): What is the maximum thickness of ice formed? Homework Equations The Attempt at a Solution Part (a) I have derived the...
  7. PsychonautQQ

    Thermal: Entropy of Ideal Gas (Sackur-Tetrode equation)

    okay so I suck at La-Tex so I'm not going to put the actual equation, but it's not important for my question. In the equation the entropy is dependent on the natural log with mass in the numerator of the argument. Why is mass involved when talking about entropy at all? I mean I think of...
  8. M

    Does Material Expansion Impact Accuracy in Thermal Expansion Experiments?

    A glass bottle is filled with salted water, and a pipette is inserted in the top through the cork. ( Leaving the bottle sealed). A thermometer is also inserted to keep record of the temperature. The glass bottle is then inserted in ice until the water reaches Zero Celsius. Finaly, the...
  9. L

    Best Material to conduct thermal heat from water at 50 degrees celsius

    I am trying to figure out what kind of material would be best used in order to transport water through a material that would be the same size/shape/diameter of a conventional pipe inside a home running water. The idea is that the water running through the pipe would be at a temperature of...
  10. B

    Two Objects In Thermal Equilibrium

    Hello everyone, I was wondering, is there any way of calculating the time it takes for two objects in thermal contact to come to thermal equilibrium?
  11. B

    Thermal Energy in 1 cubic meter of air at room temperature

    Homework Statement How much thermal energy was in 1 cubic meter of air at room temperature. Give your answer in Joules. How much kinetic energy does one cubic meter of air have if it were to hit the ground after falling 100 m? Give your answer in Joules. Which has more energy...
  12. N

    Calculating Thermal Speed VTh with R Constant

    VTh= sqrt[(3RT)/M] where M is the molar mass How do we determine which R constant to use?
  13. R

    How to Calculate Thermal Expansion Coefficient Without Overall Density?

    I need a question answered. If given the density of 2 materials in a composite, the fibres & the matrix, but not the over all density of the composite, how can one go about finding the thermal expansion coefficient, alpha of the composite? I have Youngs modulus, density of each individual...
  14. U

    Thermal Diffusion Problem - Cylindrical Rod

    Homework Statement Part (a): Under what circumstances do these equations work? Part (b): Find Temperature as a function of x, in steady state. Part (c): Show heat loss is proportional to r^1.5 Part (d):Assume A = 0, show solution works, and find γ.Homework Equations The Attempt at a Solution...
  15. T

    How does partial pressure of O2 affect thermal oxidation time for Si?

    Hi guys, I'm trying to use thermal oxidation with Si wafers in order to get SiO2 to use for electric components. I've been trying to find out how the partial pressure of the gases used (O2 in this case, it's a dry oxidation) affect the oxidation time, but I haven't been able to find an...
  16. Y

    How Does an Electric Heater Affect the Melting Process of Ice?

    1. A 0.25kg piece of ice at -30°C is warmed by an electric heater and the following graph of the temperature is produced (I just redrew the graph). Assume that there has been no loss of energy to the surroundings. a) use the information on the graph to determine the power output of the heater...
  17. U

    Thermal Conductivity - Estimate Temperature

    Homework Statement Given an insulating case outer surface at 25C, radiates heat to surroundings at 20C. Find temperature inner surface. Homework Equations The Attempt at a Solution The heat is conducted through a thickness of 2.5mm, with a temperature difference of 5oC. Thus...
  18. M

    Thermal Equilibrium With Insulated Liquid And Gas Containers

    Homework Statement A beaker with a metal bottom is filled with 20g of water at 20∘C. It is brought into good thermal contact with a 4000 cm^3 container holding 0.40mol of a monatomic gas at 10atm pressure. Both containers are well insulated from their surroundings. What is the gas pressure...
  19. S

    Thermal, steady-flow, table, continuity

    Homework Statement Steam at 2 MPa and 208°C enters a nozzle with 20m/s. During the expansion process, its enthalpy drops to 2.86 MJ/kg because of the losses encountered. a) Determine the exit velocity from the nozzle. b) If the mass flow rate is 1kg/s, determine the flow area at the...
  20. A

    Thermal Expansion of a circular steel plate

    Homework Statement A circular steel plate of radius 15 cm is cooled from 350 C to 20 C. By what percentage does the plates area decorate ? Homework Equations A=∏r^2 Af = Ai (1+2∂ΔT) specific heat of steel = 12 x 10^-6 The Attempt at a Solution r = 15 cm = .15 m Ai = .070685 m^2...
  21. F

    Thermal conductivity and Debye temperature

    Hi all Homework Statement The Debye temperature of argon is 92 K and that of silicon is 345 K. Rank the following in order of thermal conductivity (largest value first): (i) A 1 cm3 cube of silicon at 6 K (ii) A 512 mm3 cube of silicon at 2 K (iii) A 1 mm3 cube of argon at 4 K (iv)...
  22. T

    What are the best thermal physics textbooks for self-study?

    Hi again, I'm looking for a book to self study thermal physics/statistical mechanics. I would like one with an abundance of worked examples and problems with solutions as well. I've browsed through a few other threads and found these were the general "good" books deemed by the community...
  23. C

    How Does a Magnetic Field Affect Thermal Transport in Graphene?

    Published values for the room temperature thermal conductivity of graphene vary from ~2000 W/m*k to 5600 W/m*k, for freely suspended samples. The large discrepancy shows the sensitivity of graphene to lattice defects (contact with substrate, edge defects, etc.) Thermal conductivity increases...
  24. J

    Modelling an Micro Thermal Enrergy Harvestor in COMSOL

    Good Evening , i am post graduate student of Thermal Engineering.I have some experience to COMSOL software(but not expert atleast). So now i am doing a project on Modelling a Micro thermal energy harvestor. The problem goes something like this , there is strip made up of bimetal ( material of...
  25. V

    Show that the total weight w of an assembly in thermal equilibrium is

    Homework Statement Show that the total weight w of an assembly in thermal equilibrium is a maximum. Homework Equations S= k ln W? dS = dQ/ T ? S is maximize when thermal equilibrium is reached. The Attempt at a Solution First of all, i don't know what does "total weight w" means...
  26. I

    Bragg Angles and Thermal Expansion

    Problem statement: The Bragg angles of a certain reflection from copper is 47.75◦ at 20◦C but is 46.60◦ at 1000◦C. What is the coefficient of linear expansion of copper? (Note: the Bragg angle θ is half of the measured diffraction (deflection) angle 2θ). Attempt at solution: Using...
  27. N

    Thermal Equilibrium of Lens and Disk in Solar Projection

    Lens & Disk The image of the sun is projected on the disk using a lens of radius r<<d and focal length f<<d (d is the distance between the sun and the disk.. The magnification of the lens is M`f/d, so that the image completely fills the disk R`=MR. When the disk reaches thermal equilibrium...
  28. S

    Why Do Thermal Neutrons Use v = sqrt(2kT/m) Instead of v = sqrt(3kT/m)?

    The most probable velocity of thermal neutrons can than be approximated by the Boltzmann constant and is given by the following: v = sqrt (2kT/m) where k is the Boltzmann constant T is the temperature m is the mass of the neutrons My question is why is the above equation not the...
  29. Entanglement

    Where does thermal radiation come from?

    Where does thermal radiation come from? vibration of the molecules or the excitement of electrons ?
  30. M

    Materials that change thermal properties by applying electrical input?

    Do such materials exist? If they do, are there materials that go from very high to very low thermal conductivity depending on electrical input?
  31. C

    Good thermal conductor but insulator

    Hi, Does anybody know a material which is a good thermal conductor and an insulator at the same time (at temperatures around 4 K) and is "easy" to fabricate? For e.g. sapphire fulfils the first two requirements, but is extrmely hard.
  32. C

    Calculating Thermal Conductance of Axial Cylinder

    How to calculate the thermal conductance ( in axial direction ) of a cylinder having length equal to its radius
  33. A

    Manufacturing question for thermal expansion disagreement

    Hello, my colleague and I are having a disagreement about the amount of thermal expansion in a particular part we are working on (manufacturing environment). It is a piece of structural steel, which has a thermal expansion value of 12 (10^-6/K according to the chart at...
  34. U

    Thermal boundary layer and hydrodynamic boundary layer

    So I know individually how these form. Unfortunately I haven't found any sources that describe more detailed questions that pop up in my mind. Could someone help me answer a couple of questions? 1. So if a thermal boundary layer forms in a 'plug flow' model i.e. when there is no momentum...
  35. A

    (Thermal) Vibrational degrees of freedom

    Let's say I have a molecule such as CO2, where there are three atoms and a linear structure. I understand that there are 3 translational degrees of freedom and 2 rotational degrees of freedom (since it's symmetric). However, the number of vibrational degrees of freedom (DoF) confuses me. My...
  36. E

    Can This New Insulating Board Ignite Quickly Under High Heat Flux?

    Homework Statement A new type of insulating board has been developed by that esteemed construction company Kaput Ltd. They warn that at extremely high heat fluxes it could be ignited, but they don’t think it’s very likely and it would take hours, so there’s no real risk! As an expert on the...
  37. C

    [Thermal] Is it possible that increases of moles decrease entropy?

    From Statsitical And Thermal Physics (Reif. international edition 1985) 160 page. (5.4.4) S(T,V;√) = √[∫{cv(T`)/T`}dT` + Rln(V) - Rln(√) + constant] (integral is from T0 to T , cv is specific heat) This is a entropy of system for temperature 'T' , Volume 'V' , Moles '√' <--...
  38. T

    Does thermal radiation involve ultraviolet x ray and jamma ray

    does thermal radiation involve ultraviolet x ray and jamma ray or just heat of light...
  39. R

    A thermal expansion coefficient of spacetime?

    Are there any theories or thoughts that view spacetime as 'having' a coefficient of thermal expansion... analogous to the CTE of water? An inflection with density in regards to temperature?
  40. R

    Why is the direction of temperature gradient important in thermal conductivity?

    I'm doing Thermal conductivity and I'm kinda confused on something wrt to the temperature gradient...why is it that ΔΘ in the first case the smaller value minus the larger but in the second example it's the larger minus the smaller?
  41. Feodalherren

    Thermal Equilibrium of a system

    Homework Statement A combination of .25kg of H2O at 20C, .4kg of Al at 26C and .1kg of Cu at 100C is mixed in an insulated container and allowed to come to thermal equilibrium. Ignore any energy transfer to or from the container and determine the final T of the mixture. Homework Equations...
  42. J

    Measuring thermal energy of surface contaminants

    Using a heat source to increase the temperature of an agricultural commodity like corn, could a thermal camera detect temperature differentials over time as the commodity cools, versus localized surface contaminants such as mold or fungus? I'm thinking yes in theory but the differences might be...
  43. T

    Why is a resistor for convection not included in the thermal circuit solution?

    Homework Statement Here is a picture of the question with the solution: When I attempted this I added a resistor for the convection of the fluid inside. But the solution does not do this, does anyone know why?
  44. G

    Find Thermal Diffusivity from Kelvin Functions

    Homework Statement I performed an experiment where we have to find the thermal diffusivity of rubber. This is done using the phase difference of the axial and external temperatures of the rubber. The teacher's guide says to use the Kelvin functions, plot them against x. Where x = r(√(2pi/TD))...
  45. J

    Varying thermal conductivity with length

    I'm interested in modeling a system where the material varies along its length, thus the conductivity coefficient would be a function of both T, and x. k(T,x). For starters, if I assume negligible change w.r.t T, then he heat diffusion equation would be d/dt(k(x)dT/dx)=0. Correct? What if k just...
  46. K

    Linear thermal expansion problem

    Hey fellas please consider helping me with this.. There is a bar of some material that is heated from state 1 to 2 to 3. If l1 is the length at 1 then we have, l2 - l1 = l1(1 + a(t2-t1)) l3 - l1 = l1(1 + a(t3-t1)) If, t3-t2 = t2-t1, Then l3-l2 = l2-l1 But if it is written l3 - l2 =...
  47. M

    Thermal equilibrium for ice being added to liquid water

    Homework Statement 0.05625 m^3 of H2O(s) is added to a thermally isolated system of 20 L of H2O (l). If the ice was initially at 0 C and the liquid water was initially at 95 C, what is the final state and temperature? The Attempt at a Solution I missed class for this so I'm going by...
  48. W

    Thermal decomposition of calcium carbonate - problem

    Hello, here goes the problem: The mass of calcium carbonate upon thermal decomposition decreased by 1/5. (a) How many molecules of CaCO3 per 100 molecules were decomposed to CaO and CO2. (b) The content of CaO in the final sample express in molar fraction. My solution: I set the starting...
  49. C

    Heat flux as a fraction of energy flux due to thermal re-radiation

    Homework Statement Radioactive decay of elements in the Earth's interior results in a mean heat flux through the Earth's surface of 5x10^-2 W/m^2. What is this flux expressed as a fraction of the energy flux due to thermal re-radiation of absorbed solar energy? If radioactive decay were the...
  50. M

    Thermal decomposition of calcium carbonate ?

    In general, we heat CaCO3 to temperature of approximately 825°C it decomposes into calcium oxide and liberates carbon dioxide gas: CaCO3 →825°C→ CaO + CO2 Is it possible to heat the calcium carbonate at temperatures below 825 degrees Celsius, so the decomposition into calcium oxide.
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