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. B

    Space Shuttle, thermal energy transfer, book makes no sense

    Homework Statement Space shuttle enters the atmosphere. (i) What happens to the transferred energy? (ii) how do the high temperatures generated in the shuttle enters the Earth atmosphere relate to the material used for the underside of the shuttle surface? Why is the underside not made from...
  2. O

    Exploring Independent Research in Thermal & Material Engineering and Physics

    Hi, is there any independent research group I could tap into in thermal and material engineering and general physics. What are the credits and funding I could get from it?
  3. I

    Thermal energy distribution of an object?

    Hey all, I just wanted confirmation. The thermal energy distribution of molecules in a system corresponds directly to its blackbody curve right?
  4. B

    Thermal coefficients of expansion

    Homework Statement A brass rod (linear expansion coef 19*10-6/°C) has a radius of 8139 cm and a copper (linear expansion coef 17*10-6/°C) sheet has a hole or radius 8139+8.86cm. What temperature change (K) is required to close the gap? Homework Equations ΔL/Lo = αΔT? The Attempt at a Solution...
  5. G

    Calculating heat flux (Q) without thermal conductivity (K)

    How to calculate K or Q without one or the other? For example, if the material is unknown (but cannot test density, or melting temperature) how would you test heat flux? Q=K(Th-Tc)/(x)
  6. William89

    Maximizing Efficiency in Passive Cooling: A Thermoelectric Solution

    Hello everybody, I have a computer case project and I need to create a fanless (passive) cooling. I feel excited of the idea to use paltier thermoelectric coolers, but their efficiency is considered very low, because the hot side is usually exhausted via passive radiators. So I came up with...
  7. Soumalya

    Physical Significance of Thermal Diffusivity

    What physical interpretation can we draw from the thermophysical property of thermal diffusivity? How might we visualize the true physical meaning of this property and relate it to its definition?
  8. K

    Calculating Heat Flow in Composite Sheet with Different Thermal Conductivities

    1. A sheet of rubber and a sheet of cardboard, each 2 mm thick, are pressed together and their outer faces are maintained respectively at 0 oC and 25 oC. If the thermal conductivities of rubber and cardboard are respectively 0.13 and 0.05 W m-1 K-1, find the quantity of heat which flows in one...
  9. David Gin

    Compressor Water Cooled Chiller Thermal Calculations

    Hi All, Is there a list of thermodynamics equations regarding the chiller process from condenser, evaporator, compressor to the regulator. Say I have chiller load at 90%, what set of equations could I use to determine the supply temperature of chill water and condenser supply temperature to...
  10. D

    Calculating Thermal Expansion of Water: Is the Formula Correct?

    Hello, I'm trying to determine a way of calculating the thermal expansion of a volume of water. The formula I have come across is: ΔV = βV0ΛT The general consensus seems to be that water expands roughly 4% from 20°C to 100°C, or 4.2% from 4°C to 100°C...
  11. A

    Thermal Radiation Homework: Snow-Covered Surface Absorption

    Homework Statement Consider a snow-covered surface. Assume that the amount of solar radiation that reaches the top of the atmosphere is 1367 Wm-2. Given that 50% of this solar radiation is either absorbed in the atmosphere or reflected by clouds before reaching the the snow covered surface...
  12. 3

    Conversion of Thermal Energy into Work

    This question appeared in my IB Physics HL mock exam and I am stumped by the answer on the mark sheet. It really should be a trivial question but it's open to interpretation which is why I find it unreasonable. It was in Paper 1 from November 2014, 1. Homework Statement ? Which of the following...
  13. E

    Thermal Resistance due to Convection Heat Transfer

    Homework Statement 1) A typical wall construction for a single-family residence might consist of 0.375 inches of outer sheathing (insulating board, hardwood siding, etc.), 3.5 inches of mineral fiber insulation and then a 0.375 inches inner surface (gypsum, etc.). Typical thermal...
  14. Ascendant78

    Thermal Physics - energy, microstates, and probabilities

    Homework Statement Homework Equations The Attempt at a Solution The first part I'm not worried about, but the second part is worked out in the "relevant equations" section. Honestly, it looks like more magic than a Harry Potter movie going on there to me. I'm at a loss as to what...
  15. S

    Thermal Equilibrium and Longitudinal Relaxation

    Homework Statement Problem 6.2 from Magnetic Resonance Imaging: Physical Principles and Sequence Design. Show that M_o \approx \rho_o \frac{s(s+1)\gamma^2\hbar^2}{3kT}B_o Homework Equations M_o = \rho_o \gamma \hbar \frac{\sum m_s e^{m_s(\hbar w_o / kT)}}{\sum e^{m_s(\hbar w_o / kT)}} ...
  16. A

    Uniformity of thermal vibrations

    Hello, I have a question on the nature of vibrations due to thermal energy. Earlier today I read this article which talked about cooling a glass string to near absolute zero using feedback from a high precision sensor. http://phys.org/news/2015-08-smallest-vibration.html what I understood from...
  17. M

    Extracting Ambient Thermal Energy Without Gradients

    It seems possible to extract energy from the ambient air without temperature gradients (or at least with very small local gradients that will always be available). Being curious about this, I checked out some other threads and did not really find the specific question. (I did find some...
  18. S

    Heat transfer by thermal radiation

    Homework Statement The ice is placed in water, we know the surface area A, emissivity of both ice and water, Stefan-Boltzmann constant and the temperature of both ice and water. What is the equation for heat transfer rate between water and ice? Homework Equations Heat transfer rate by...
  19. neosoul

    Thermal physics junior or senior year

    I am registered for Thermal Physics for this year (my junior year). The online curriculum advises physics majors to take it fall of their senior year. (The class isn't offered in the spring.) I am taking 3 other physics classes as well. I felt inclined to take thermal this fall because I wanted...
  20. DavideGenoa

    Thermal efficiency: reversible and irreversible machines

    In the proof of Clausius inequality ##\oint\frac{\delta Q}{T}<0## for an irreversible cycle, I always find the fact that the thermal efficiency of an irreversible machine is **stricly less** than the thermal efficiency of a reversible machine, both operating between temperatures ##T_H## and...
  21. KingDaniel

    Engineering Systems Modeling Question (First order thermal circuit)

    Homework Statement I have a problem with understanding the thermal circuit I attached to this thread. Please help. It's a Thermal circuit of a computer CPU that needs to be simplified to have just 2 lumped capacitances and resitances. How would one go about doing that? along with the equations?
  22. A

    Difference between electrical and thermal faults?

    In case of power transformer,what is the difference between electrical fault and thermal fault? I want to know that if internal fault is occurred in power transformer then on what basis we can differentiate electrical and thermal fault?
  23. T

    Thermal Management Question in Spacecraft

    Hello guys, Below I am presenting a question related to thermal management in spacecraft . Perhaps many of you might find it interesting! And this could be a real-life problem for thermal engineering in a spacecraft . So, the question is following: An instrument dissipates 10W and, in order...
  24. K

    Thermal Emission and Scattering (Mie or Rayleigh)

    From a book intro I've been reading, Scattering, Absorption and Emission of Light by Small Particles by Mishchenko, it states that when incident light hits a particle, that particle may absorb light, scatter light or emit the light. Excerpt: Can anyone explain to me, on a physical level, the...
  25. H

    Thermal Expansion of Two Holes

    I have a problem understanding the concept of thermal expansions of solids with a hole in it. I do not want to accept face value the traditional explanation i am given that hole will increase in size because i am told to imagine if the hole was never cut. I fail to see the congruency in these...
  26. S

    Relation between thermal expansion and density in Polymers

    Hello all, Is there any direct relation ship exists between the thermal expansion and density of polymer material (eg. PMMA, Teflon) ? Like, Lorentz- lorentz law relates directly the refractive index and density of the polymer. similarly any laws relating (thermal expansion and density of...
  27. PytrTchaikovsky

    Thermal Radiation: Calc Total Emitted Joules in Certain Temp Range

    Dear forum I am working with thermal radiation. This is the specific formula: P = σ ⋅ A ⋅ T4 P = emitted effect (W, J/s) σ = Stefan-Boltzmann constant (5,67 ⋅ 10-8) A = area of object (m2) T = temperature of object (K) How can I get to know the...
  28. F

    Why are startup sources typically not used in BWRs?

    Why doesn't the ceramic pellets react with each other in the fuel tube when it is being fabricated?
  29. P

    Thermal motion of graphite atoms

    Hi everyone, I've been thinking about the quantum pencil, and I can't quite convince myself that you could perfectly balance a perfectly sharpened pencil even if the uncertainty principle went away. For those who are unfamiliar with the problem, you can read about it here...
  30. A

    Automotive What's the thermal conductivity of car insulation

    whats the thermal conductivity for car insulation? roof or dashboard, basically the thermal conductivity of foam used in most cars.
  31. T

    Thermal conductivity air to metal

    Let's say you have a small metal case that is 3 inches by 3 inches versus 2 inches by 2 inches. Inside at center is a heat generating source (let's say a small processor chip). How efficient is the transfer of heat from the processor to the air... and from air to metal between the 2 different...
  32. Coffee_

    Assumption of thermal equilibrium for ensembles

    Take for example a canonical ensemble, to use the derived distributions and probabilities, the considered system has to be in thermal equilibrium with the heat bath. Where in the derivation of the probabilities and distributions do we usually assume this? There is a point that I can identify...
  33. KaseyKC

    Thermal Kinetic Physics Question involving PV diagram

    Homework Statement I'm stuck on question A4 that is linked below. University won't provide me with any solutions. I have a TKP resit exam next month. Homework Equations dU=dQ-PdV The Attempt at a Solution Internal energy is equal to heat flow plus the work done. Work done is 0 because it's...
  34. E

    LEDs, LED Drivers, Thermal Management

    I'm trying to wrap my head around thermal management of LEDs and LED driver circuits. http://blogs.indium.com/blog/amanda-hartnett/controlling-junction-temperature-of-leds-with-thermal-management-materials A concern has been expressed that a lighting supplier needs to demonstrate (not sure...
  35. A

    Thermal Expansion of piano wire

    I'd like to setup an Excel spreadsheet to demonstrate the expected change in string frequency due to small changes in temperature. How should I go about doing this? This is the data from the piano that I can gather: -string length -string diameter -string area -string/partial frequency How do...
  36. A

    Thermal Equilibrium: How Objects Reach Balance

    Hello, What "path" do objects take to reach thermal equilibrium? Does heat from a hot part sitting in room temperature air like to travel through the most thermally conductive portions? My thought is that it is similar to current in a circuit taking the path of least resistance (where the most...
  37. j3dwards

    Thermal conduction between 3 rods

    Homework Statement Rods of copper, brass and steel are welded together to form a Y-shaped figure. The cross-sectional area of each rod is 2.0 cm2 . The free end of the copper rod is maintained at 100◦C, and the free ends of the brass and steel rods at 0 ◦C. Assume there is no heat loss from the...
  38. S

    What is the significance of thermal resistance in heat transfer?

    Hi, I shall be grateful if someone can help with this fundamental understanding, Thermal resistance (in case of conduction mode of heat tarnsfer) can be defined as; Rt = L / kA where k is the thermal conductivity Thus. thermal resistance if inversely proportional to the thermal...
  39. Y

    Thermal Physics: Cooling by both Conduction & Convection

    Hi all, I am not sure if the is the right place to post the question being new to the forum, but I am looking for some help with a heat transfer experiment that I ran for my honours thesis. Essentially the aim is to determine if warmed saline fluid bags taped to 3 different types of tree barks...
  40. S

    Thermal Hydraulics: Solving a PWR Problem

    Hi guys, I'm a starter in Nuclear thermal hydraulics course, and I'm having a hard time in solving this problem:1. Consider a PWR operating at the thermal power of 1893MW. It contains 193 fuel assemblies, each consisting of 204 UO2 fuel rods 1cm in diameter. Using the equation...
  41. V

    Using Laminar Flow to measure Thermal Conductivity

    So, there's a project I'm working on (no, it's not school related), where I'm trying to figure out how to measure thermal conductivity of a material using laminar flow. The idea is to integrate this into a larger system, and it's a measurement I'd like to take in the process. I know the...
  42. P

    Exposure rate from thermal neutrons through water

    Homework Statement A beam of thermal neutrons (10^12 neutrons per cm^2 second) strikes a 1cm thick water target normal to its surface. The target is a round disk with diameter 20cm. Find the exposure rate (R/second) 100cm beyond the water target (the middle of the disk) from only the...
  43. L

    How to turn thermal energy of room into work

    So I live in Florida and I don't use my air conditioner, so my apartment gets pretty hot sometimes. It occasionally gets over 90 degrees F. I had an idea of how to cool the room, but I'm not sure how feasible it is. My idea is a device that could turn that thermal energy into work, which should...
  44. B

    Thermal expansion (Simple) (attempt posted)

    Homework Statement I'm looking for a good explanation, not interested in the answer. A geodesic dome constructed with an aluminum framework is a nearly perfect hemisphere; its diameter measures 55.0 on a winter day at a temperature of -18 C. How much more interior space does the dome have in...
  45. M

    What is the average power of the warmer bath in this thermal dynamics problem?

    Homework Statement A warm water bath containing 10.0L of water is connected to an ice-water bath with a piece of metal of length L = 2.11 m and cross sectional area A = 1975 cm2. The metal has a thermal conductivity of km = 60.5 Wm-1K-1, a specific heat of cm = 239.7 Jkg-1K-1 and a density of...
  46. goonking

    Kinetic energy to thermal energy

    Homework Statement Homework Equations Q = c m ΔT The Attempt at a Solution so converting 55 mph to meters per sec gives me a velocity of 24.58 m/s kinetic energy of car is 1/2 m v2 i set 1/2 m v2 = c m ΔT plugging in v and c and masses of both ΔT = 134.56 is that correct?
  47. A

    How does density affect thermal conductivity?

    Since the flow of heat in solids happens due to the collision of the molecules with each other, thereby increasing their internal energy, a higher denser material will have molecules closer, does it mean that the thermal conductivity of high density materials will be higher than the lower...
  48. Mr Davis 97

    How do we measure the thermal energy of an object?

    I know that temperature is used to measure the average internal kinetic energy of an object, but how do we go about measuring thermal energy? It seems as though temperature could only compare the thermal energy of objects with the same mass and volume. But for objects with different mass and...
  49. R.Mesri

    How much energy is produced during thermal expansion?

    We say the expansion coefficient of steel is 12 × 10 -6 m/m°C, Young's modulus 210 × 109 N/m2 and yield stress 250 mega Pascal. With 100 meters length and 0.1 m2 section area , If we increase its temperature 10 °C, how much energy will be produced by expansion force in Joules? with young's...
  50. mattyboson12

    Understanding Thermal Resistance in Heat Transfer: An Analysis and Explanation

    Homework Statement [/B] Explain how the concept of thermal resistance can be used in the analysis of heat transfer problems 2. The attempt at a solution So I'm made a few key points but I am not sure if I have answered the question fully: Thermal resistance is a heat property and a...
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