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. L

    I from a physics brain: thermal capacity, conduction, cooling

    I am doing a zainy experiment at home. I need to devise a way of applying a cooling intensity factor (CIF) of around 70 mW/cm2. I need to cool material that is roughly 30 degrees Celsius down to around 2 degrees Celsius. The cooling has to last for a period of one hour or more. The surface...
  2. V

    Thermal condution? little confusing can u to remove my doubt.

    thermal condution? little confusing can u please help to remove my doubt. According to law of thermal conduction dQ/dt=-kAdθ/x. variable have their usual meaning. first of all i want to know what is meaning of dQ/dt in this law?? If we see it in a cylindrical object with it's curved part...
  3. N

    Thermal Storage Simulation in TRNSYS Software

    Hi all, As part of my Final Year Project I am studying the feasibility of domestic seasonal thermal storage in water tanks. I am hoping to model this system and have been looking at the TRNSYS software for doing so. I know that this is possible to do because I have seen a number of studies in...
  4. R

    Steel Building Height Variation in Summer vs Winter: Thermal Physics Analysis

    Thermal Physics (Help me!) Following an engineering design, a building is constructed using a steel framework that is 50m high. How much taller is it on a summer day when the temperature is 38oC than on a -5oC winter day?
  5. D

    Passive mechanical safety: thermal sense rods.

    So, I had this idea for passive safety. Break-apart rods (zirconium with low-melting point metal inserts for example) which go through reactor core at regular intervals, are tensioned by springs, and in the event of overheating, are torn apart, operating simple (springs, latches) mechanisms to...
  6. T

    Solid mechanics thermal stress of infinite cylinder

    Homework Statement My problem is to calculate the Thermal stress of a Cylindric shell with inner radius a and outer radius b the inner surface is experiencing Temperature T1 and the outer surface is experiencing T2 with T1>T2 assuming that the linear thermal expansion coefficient is a, the...
  7. D

    What is the Relationship Between Coefficients for Thermal Expansion?

    Hi Physicsforums, I was trying to derive the formula that the coefficient for volume expansion, β, is 3 times the coefficient for length expansion, \alpha. As a reminder, the formulas are: \DeltaL = \alphaLo\DeltaT and \DeltaV = \betaVo\DeltaT where, supposedly, \beta = 3\alpha...
  8. Telemachus

    Why Is Thermal Radiation Usually Negligible in Solids?

    Hi there. Here is the deal. In my lab work, I've done experiments concerning on heat conduction. Now my professor had corrected my inform, and asked me a question for which I have no answer. I consulted for my work the book "heat conduction in solids" by H.S. Carslaw. The book says at the...
  9. H

    Thermal Expansion: Elongation Explained

    what exactly is elongation? in the thermal expansion question, it says if the elongation of the 2 rod fasten end to end is the same
  10. G

    Thermal equilibrium, find final temp. or system?

    I solved the problem and have the correct answer just not sure about something. Question:What will be the equilibrium temperature when a 274 g block of copper at 317°C is placed in a 137 g aluminum calorimeter cup containing 829 g of water at 13.0°C? So heat lost by copper = heat gained...
  11. A

    How Does Mercury Completely Fill an Aluminum Container When Heated?

    Homework Statement A 1-liter aluminum container at 20oC is filled with 0.975 liters of mercury at 20oC. If both the container and the mercury are heated, at what final temperature will the mercury completely fill the container? αAl = 24 × 10-6 (Cº)-1; βHg = 1.82×10-4 (°C)-1 Any help on...
  12. A

    Thermal expansion of an aluminum bar

    Homework Statement Consider a bar of aluminum which is 10 cm X ½ m X 20 m. If the bar undergoes a change in its temperature from 10° C to 20° C, determine the new dimensions of the bar. Homework Equations ΔL=αL0ΔT α=24x10-6 The Attempt at a Solution I understand how the formula...
  13. X

    Questions about kinetic energy, thermal energy and momentum

    Hello, kinetic energy is in some cases a bit of a mystery to me, I've made several assumptions about these things. But some of those assumptions seem to conflict a bit with what seems to be happening, so I thought I'd throw these assumptions out here to maybe hear where I'm wrong. Any comments...
  14. 1

    Another thermal expansion problem

    Homework Statement A vertical glass tube of length L = 1.2800000 is half-filled with a liquid at 20.0000* C. How much will the height of the liquid column change when the tube is heated to 30.0000*C? Glass linear expansion co = 1e-5/K Liquid volume expansion co = 4e-5/K Homework...
  15. 1

    I can't figure this one out thermal expansion of rod and ruler

    Homework Statement At 19°C, a rod is exactly 20.01 cm long on a steel ruler. Both the rod and the ruler are placed in an oven at 219°C, where the rod now measures 20.18 cm on the same ruler. What is the coefficient of linear expansion for the material of which the rod is made? Homework...
  16. S

    Convection and Thermal Resistance

    I have a question... Suppose you have a thin and long rectangular piece of aluminum. You heat one end (pt A). The thermal resistance (steady state) from one end (pt A) to the other (pt B) would be θ=ΔT/W Where W= Watts of heat energy. ΔT = temperature of ptA - temperature of ptB...
  17. C

    Why is steam condensed in thermal power cycle?

    Why is this done? Wikipedia says that condensing the steam makes the cycle 'more efficient.' How is it more efficient? Why can't the de-energized steam be transferred to the boiler without condensing it?
  18. I

    Calculating Velocity of a fluid (by thermal convection) from the heater power.

    Ok, I have some questions to answer for this lab report, and one of them has left me clueless. The experiment was as follows: An apparatus is made of a rectangular circuit (of known dimensions) of tubes filled with water with thermometers visible at various points throughout the circuit. No...
  19. S

    Thermal Expansion, Change in Temperature

    Homework Statement ""If the coefficient of thermal expansion of steel is 1.1 x 10^ -5 ℃^ -1 and a railway rail is 4. 5 m long, how much would the length Δ L of the rail increase by if the temperature changes from -10 ℃ to 30 ℃? "" Could anyone direct me to a youtube video, or something...
  20. M

    Thermal conductivity of a metalic bar

    Homework Statement we have a metalic bar with thermal condutivity of 200w/(m*k) it has an area of 20 cm^2 which is in contact with with an heater that delivers 200 W and is at 300ºC. the metalic bar has a thickness of 1cm The two questions are: a) once the system have entered a...
  21. P

    Shuttle Thermal Tiles: Description and Suggestions

    Friction with the air is often neglected, but when traveling at Mach 18 it becomes a huge factor. To cope with this, NASA engineers have ingeniously developed sand-based thermal tiles that are designed to withstand temperatures that can reach up to 2600 degrees Fahrenheit. There are 3 types of...
  22. P

    Computing Thermal Average for a Free Real Scalar Field

    Homework Statement Homework EquationsHi! I read a book where a free real scalar field with Hamiltonian H = \int \dfrac{\mathrm{d}^{3}p}{(2 \pi)^{3}} \, E_{\vec{p}} a_{\vec{p}}^{\dagger} a_{\vec{p}} is beeing discussed. Note that: E_{\vec{p}} = \sqrt{\vert \vec{p} \vert^{2} + m^{2}}...
  23. A

    Theory behind thermal insulation

    I wish to design highly insulating structural load-bearing walls using local materials. Part of that effort requires an understanding of the dynamics of current insulation materials and why some are much higher in R-value while using the same base material. Part of my study so far suggests that...
  24. S

    Net thermal radiation from an object outside at night

    I am trying to model the cooling of an object (for example, a sheet of glass) placed outside at night. At the moment I am only considering heat loss by radiation. I know that the net radiation from the object will be: Rnet = Robj - Rsky where: Rnet = the net radiation from the object...
  25. S

    How Much Energy Is Lost to Friction in This Physics Problem?

    Homework Statement In the diagram given, you pull upward on a rope that is attached to a cylinder on a vertical rod. Because the cylinder fits tightly on the rod, the cylinder slides along the rod with considerable friction. Your force does work (W = + 100 J) on the cylinder–rod–Earth system...
  26. S

    Pressure Calculation in Closed Loop PV Thermal

    Hi I am trying to design a closed loop testing system for a solar thermal system using water as the heat transfer medium. There a number of fittings and and pipework involved, the water might reach temperatures up to 80/90 deg C. I am trying to calculate what the max pressure in the...
  27. G

    Deriving the thermal conductivity of graphene

    How do I go about deriving the thermal conductivity of graphene (specifically, in the low temperature limit) when I'm given the phonon dispersion relation? I haven't been able to find anything explaining how the dispersion relation relates to the thermal conductivity in materials. (this is...
  28. H

    Why Is Thermal Expansion the Same for Solid and Hollow Spheres?

    Explain why the thermal expansion of a spherical shell made of a homogeneous solid is equivalent to that of solid sphere of the same material. I guess these equations would be of some help. (ΔA)=A*2α*(ΔT) α→ Coefficient of linear expansion. A→ Area T→ Temperature (ΔV)=V*3α*(ΔT)...
  29. L

    Thermal Vac chamber pressure gain question

    Hi group, I work at Thermal Vacuum Chamber, and we had an incident last night where our chamber, Which is 70' H x 30' D, was pumped down to a pressure of 3.7E-7. There was a release of gas into the chamber abruptly last night that caused the pressure in the chamber to rise to 5.0E-7, before it...
  30. N

    Rhodium Thermal absorption cross section.

    Rhodium has been measured and the following values have been obtained for the resonance parameters of a well-isolated resonance Eo=1.26 ev , σo=5000 b , Γ = 0.156 ev , σs=5.5 b , Is there anyone can help me HOW to calculate the thermal absorption cross section ? I'm disparate I don't know how to...
  31. R

    Discussion about thermal chemical-equilibrium gas and calorically perfect gas

    Homework Statement Calculate the percent difference of P2/P1, T2/T1, and ρ2/ρ1 between the CPG assumption and the thermal-chemical equilibrium assumption. Which percent difference is the lowest and what could be the possible reason? U1=4000 m/s Altitude=60 km R=8314 N m/(kmol K) P1=21.96 Pa...
  32. T

    Can't understand what's thermal equilibrium

    In wikipedia it says: "Thermal equilibrium is a theoretical physical concept, used especially in theoretical texts, that means that all temperatures of interest are unchanging in time and uniform in space." But isn't temperature defined because of the thermal equilibrium concept? It's defined...
  33. A

    Three magnetic systems in thermal contact

    Homework Statement "Consider three magnetic systems in thermal contact, each composed of N1, N2, N3 spins, +m or -m. Starting from s1 = s'1 + δ1 etc. calculate the average square deviation <si2 of each system. Homework Equations s'1 is the most probable configuration for s1. N1+N2+N3 =...
  34. K

    Entropy changes: Thermal energy to work and (some) back to Thermal energy

    In classical thermodynamics, if we dissipated the kinetic energy of an object as thermal energy, then we would increase the entropy. However, let's say we took 90% of some thermal energy in a reservoir, and converted it into work, and 10% of that is converted back into thermal energy after 1...
  35. D

    Time constant of a thermal model with multiple masses and units

    Hi, i have modeled a thermal system in simscape: the unit includes a polymer casing inside which there is a heater, heat spreader and a fluid sample in that order. i wish to validate this model by hand calculations such as finding the time constant. However i do not know how to find the time...
  36. K

    Thermal Physics Problem: CO2 Gas Heat Capacity at Different Temperatures

    1. Homework Statement Consider a CO2 molecule, which is linear and has vibrational modes with frequency corresponding to 2565 cm-1 (an asymmetric stretch), 1480 cm-1 (a symmetric stretch) 526 cm-1 (bends). Sketch a curve showing how the constant volume heat capacity of CO2 gas varies with...
  37. K

    CO2 Molecule Vibrational Modes and Heat Capacity | Thermal Physics Problem

    Homework Statement Consider a CO2 molecule, which is linear and has vibrational modes with frequency corresponding to 2565 cm-1 (an asymmetric stretch), 1480 cm-1 (a symmetric stretch) 526 cm-1 (bends). Sketch a curve showing how the constant volume heat capacity of CO2 gas varies with...
  38. M

    Heat,work, thermal efficiency problems

    This is the question that I can't really answer 1. A cycle looks like an ellipse in the T-S diagram. The maximum and minimum temperatures are 1000K and 400K. The maximum and minimum entropies are 0.705 KJ/K and 0.235 Kj/K. Determine a. the heat added per cycle, b. the work produced per...
  39. P

    A calculation on thermal energy from friction.

    Hello, I am new here and I joined because I was wondering if I could find any help concerning finding heat from friction. The question is fictional, I am not talking about something that has happened, but I am interested in a realistic calculation for the physics behind it. in my problem...
  40. L

    A 3D harmonic oscillator is thermal equilibrium

    hay guys, A three-dimensional harmonic oscillator is in thermal equilibrium with a temperature reservoir at temperature T. Finde The average total energy of the oscillator I have no idea, how can I solve this problem, can you hint me please:rolleyes:
  41. J

    Calculating the conversion of potential energy to thermal

    Homework Statement Horseshoe Falls, one of the Niagara Falls, has a 53 m drop. Consider one kg of water that falls over the falls. If, upon hitting the bottom of the falls, all of the water’s potential energy is converted to thermal energy and this heats the fallen water, calculate the...
  42. C

    Gaseous Core Nuclear Thermal Rocket

    http://www.projectrho.com/rocket/enginelist.php#id--Gaseous_Core_Nuclear_Thermal_Rocket http://en.wikipedia.org/wiki/Gas_core_reactor_rocket How practical would this be? How much of a technological leap would be needed to achieve this? Would it make outer solar system missions possible...
  43. U

    Thermal Insulation for Keeping Liquid Cold - 65 characters

    Hi, I am trying to keep a small vial of liquid cold (> 2 Celcius but < 8 Celcius) for 10 hours when the ambient temperature is 20 -> 30 Celcius. So if I'm making a container to hold it I'd like to know what is the best material to use. My initial thought was to simply place it in a thermos...
  44. E

    Bragg Angles + Thermal Expansion

    Homework Statement A crystal is heated from 0 to 100 degrees celcius, its lattice parameter 'a' increases by 0.17% due to thermal expansion. if we observe an x-ray reflection at a bragg angle theta= 19.3 degrees at 0 degrees celcius, by how much will theta change when the sample is heated to...
  45. A

    Thermal - derive a work equation

    Homework Statement Show how W= (P2V2 - P1V1) / \gamma -1 can be derived using relations between PVgamma = constant, and W(1 to 2) = -\int P(T,V) dV (from v1 to v2). Homework Equations I think we can use R = Cv (\gamma - 1) The Attempt at a Solution Not sure how to start. The...
  46. A

    Thermal Physics Joke: Is It as Silly as It Seems?

    The other day I sumbled upon the following joke: As we all know, it takes 1 calorie to heat 1 gram of water 1 degree centigrade. Translated into meaningful terms, this means that if you eat a very cold dessert (generally consisting of water in large part), the natural processes which raise...
  47. A

    Thermal - why check tire pressure when it's cold?

    Homework Statement Why should we check pressure in a tire when the tire is cold? Homework Equations ... The Attempt at a Solution After Googling around, I found a statement saying that when a tire is "cold," it means that it is at 'room' temperature, or the surrounding air in this...
  48. F

    Thermodynamics- thermal expansion coefficient

    Homework Statement Prove that the volume thermal expansion coefficient of a solid is equal to the sum of its linear expansion coefficients in the three directions. \beta=\alphax +\alphay+\alphaz For isotopic solid when \beta = 3\alpha Homework Equations \beta=[1/v][dv/dt]p= \alphax...
  49. W

    What's the relationship between phonon spectrum and thermal conductivity

    I mean how can i analysis the thermal conductivity of two structures with their phonon spectrum. thank you!
  50. 9

    Thermal Statistics - Microstate Probabilities

    Homework Statement For a system in equilibrium at temperature T, the probability of finding it in a microstate m is: P(m) = (1/Z)exp(-E/kT) where Z is the partition function. There are three accessible microstates, two with energy E_{a} and one with energy E_{b}. Two identical and...
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