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. F

    Max thermal conductivity required for heating elements

    I'm designing an oven and want to ensure that the insulation I specify has a low enough Thermal Conductivity (k) to resist excessive heat loss. I determine heat loss (Hout)with the following equation: Hout=A*U*(T1-T0). U is dependent on k (U=k/L). I omitted the heat transfer coefficient in...
  2. L

    Is Osmosis a Phenomenon of Thermodynamics?

    I have read that osmosis " works like a machine ". It lifts weight ( this is obvious ) on the expense of thermal energy. Does anyone has any thoughts about how it consumes thermal energy? Thank you in advance.
  3. I

    Thermal expansion of a liquid in a cylindrical container

    Homework Statement There is liquid in a cylindrical container at some level. Now when the container is heated, the level of the liquid remains the same in the container. What is the relationship between the coefficient of linear thermal expansion of liquid and the container ? Homework...
  4. M

    Thermal insulation in quantum computers

    Hello! I was watching a video () about how extreme low temperatures are achieved in a D-Wave computer. As they explain, they have this series of cooling stages, each of which providing a temperature drop over the previous. I was wondering however, how could they avoid thermal propagation through...
  5. T

    What is the distinction between thermal and internal energy?

    What is the difference? I read that thermal energy includes both kinetic and potential energy but isn't that what internal energy is? Cheers!
  6. E

    Thermal expansion over a large temperature range

    So I've been working at a steel mill where we deal with billets cooling from temperatures around 1200 C to between 10-25 C. I have access to average thermal expansion coefficients over this temperature range. First question: Over a large temperature range as aforementioned am I correct in...
  7. P

    Does Mixing Fluids A and B Create a Predictable Thermal Capacity?

    Hi, Say we have fluid A with thermal capacity C_a and fluid B with C_b. If we create a solution with X% of fluid A and (1-X)% of fluid B, is it true that the new thermal capacity of the mixture will be C_new ?= C_a*X + C_b * (1-X) Or it is a case-by-case relationship that depends on the nature...
  8. L

    Mixing Fluids: Calc Velocity & Temp of Final Mixture

    A stream of water at 300 Deg K flowing into a mixture at a velocity of 5m/s. Another stream of water at 400 Deg K is flowing in at 8 m/s.How to calculate the final velocity and temperature of the fluid after mixing? Please find the attached image? If it requires any c/s dimensions please assume..
  9. soothsayer

    Calculating thermal resistance across a metal flange

    I've been using the following equation for thermal resistance to make basic calculations for a few different engineering designs: $$R_t = \frac{L}{kA} $$ Where L is the resistance path length, A is the cross-sectional area perpendicular to this path and k is the thermal conductivity of the...
  10. F

    Solar thermal collectors in parallel

    I am using TRYNSYS software to simulate solar thermal cooling. I need to install many solar thermal panels (evacuated tubes) in parallel. However, there is no feature to do that automatically in the software; so I can only add them manually with complex piping and stuff. So my question is: Is...
  11. M

    I Thermal radiation and light pump

    Hello, I read a lot at this forum about thermal radiation but still i have questions. Consider black body at some temperature T. It means that inside that body we activate many modes of quantum oscillators with some probability(Bose-Einstein) depend on temperature T. Now let's have some bulk...
  12. A

    Exploring Thermal Effects: What Makes Particles Vibrate?

    I've recently begun studying thermal effects. I learned that thermal energy could be transferred within an object through conduction and from a distant object through radiation. (let me know if I'm wrong here) I also learned that when matter is heated, it's particles begin to vibrate, move apart...
  13. J

    What is the Optimum Thickness for a Thermal Container Design?

    Hello everyone, first of all, thank you very much for reading. I have to design a container (100 mm of height and 80 mm of interior radius of XPS) to keep a cryogenic mix (water and salt ice) at -15ºC at least for 40min. And my problem is to calculate the optimum thickness of XPS. I've been...
  14. Jordan D

    Thermal Dynamics - Ring Heated Up

    Homework Statement This is more of a question that doesn't require formulas as much as common sense. The question goes,"If you have a ring that is heated up, would the hole in the middle get smaller or larger." Homework Equations N/A The Attempt at a Solution I know that when objects are...
  15. N

    Thermal efficiency of reciprocating engines

    In a perfect, ideal world with constant specific heats the thermal efficiency of an otto cycle is dependent on its pressure ratio and a diesel cycle is dependent on its pressure ratio and cut off ratio. But since in the real world the equations with these terms do not hold since specific heats...
  16. Philip Koeck

    Why can one calculate entropy change for thermal conduction?

    A hot object in thermal contact with a cold one will finally reach a temperature in between. Why can the entropy change of each object be calculated as if the process was reversible? Is there a reversible process with the same final and initial state and what would that be?
  17. A. Neumaier

    I Particles from a thermal source

    In the following, I want to consider both photons in a sharply focussed, monochromatic beam of light (''type P'') and electrons in an electron beam (''type E'') on the same footing. In the following, X is either P or E. If we only concentrate on the internal degrees of freedom, both kinds of...
  18. J

    Relationship between pressure and thermal conductivity

    Homework Statement I would like to derive an equation that relates the thermal conductivity to the pressure using the kinetic theory of gases. However, I assumed that thermal conductivity was independent of pressure. Homework Equations I know that P = 2N/3V (1/2mv^2) Also: I believe that...
  19. C

    Thermal B.L Vs Viscous B.L

    How can I get the same properties of viscous B.L using thermal boundary layer as I am making a flow visualization for flow transition to turbulent using Schlieren Technique for flat plate? And also how can I compare between them in this situation?
  20. Titan97

    Thermal expansion of a rod with variable alpha

    Homework Statement The coefficient of linear expansion of a rod of length 1 meter (at 300K) varies with temperature as ##\alpha=\frac{1}{T}##, where T is the temperature. Find the increment in length when the rod is heated from 300K to 600K Homework Equations $$\Delta L=L\alpha \Delta T$$ The...
  21. dakota224

    Problem: using thermal expansion to calculate sea level rise

    Homework Statement Since the 1980's a total of 20 x 10^22 J of additional energy has been absorbed by the worlds oceans. This is 90% of the additional heat our planet is storing as a consequence of global warming. The surface area of the worlds oceans is 361,900,000 km^2 and we will assume this...
  22. empty_set

    Change in density due to thermal expansion

    Homework Statement I want to find the mathematical proof to show that the density of an object changes with thermal expansion. My professor showed this in class and it was horribly wrong because he let a few things out. The book I'm reading showed it in 4 steps and left out a lot of the crucial...
  23. R

    Sodium Bicarbonate Thermal Decomposition

    I have a question about the thermal decomposition of sodium bicarbonate (baking soda). I need to use baking soda for an experiment but will not be using a burner to heat it. We are heating it to about 90-100C and I was wondering if we put vessel the baking soda is in under vacuum -0.5bar or...
  24. randini

    High temperature insulating material for new engine concept

    In the past, reciprocating engine platforms have prevented the use of thermal insulating materials like ceramics due to, among other reasons, abrasion and vibration. One of the problems in the past has been the movement of the piston and piston rings over the cylinder wall where the insulating...
  25. R

    Thermal power of the air extracted from a building

    Good afternoon. I need to know if the thermal power of the air extracted from a building is greater than 80kW. I know the flows entering and leaving the building. Also, I know the temperature of the air inside and outside the building. How do I calculate the power of the air extracted? thank you
  26. J

    Black Body radiation and thermal equilibrium

    Wikipedia writes: "Black-body radiation is the type of electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment". Why does it write "thermodynamic equilibrium"? If it is not in a thermodynamic equilibrium, then what changes as far as the absorption...
  27. Y

    Insulator density and thermal conductivity

    How does insulator's density affect its thermal conductivity? For example, considering such insulators as rock wool, It seems that the thermal conductivity should increase with an increase in density (due to elimination of 'air pockets'). However, experimental results, in many cases, look more...
  28. JoAstro

    What's the thermal energy of a helium atom?

    I have this formula "E= 1/2 mv^2" which I don't fully understand. Also, I don't have the values for helium's mass and velocity.
  29. P

    Calculate thermal resistance of heatsink required

    Homework Statement Q4) Calculate the thermal resistance of the heat sink required for the regulator of Q3 above given the information below [from the datasheet] and the data in the table. Q3 FIGURE 2 shows an adjustable voltage regulator using the LT1083*. The LT1083 develops a 1.25V reference...
  30. M

    A question on thermal stress and axial force in a structure

    hi guys i've really been struggling with this question but I still can't get any glimpse of idea on how to solve the problem, so the conditions are given in the table and what the question is asking for is the axial force acting in each members of the structure. ah, almost forgot to tell you...
  31. N

    Calculating Fire Temperature from Thermal Energy

    is there a way to calculate the themperture of something like a fire, if you know the thermal energy it produces.
  32. J

    Depth at which thermal oscillations become negligible

    Hello everyone, I am working thru some of the mathematics of geo-exchange systems (semi passive heating and cooling systems for homes) and I'm starting with a very simple model: The ground is modeled as a perfectly insulated rod (perfectly insulated because of symmetry, there is no heat flux in...
  33. Searay330

    Thermal Expansion linear vs area expansion

    this is a picture of my notes for thermal expansion for linear vs area. my question is why does the area coefficient of expansion for the area = 2(liner coefficient of expansion). any insight would be appreciated.
  34. S

    Thermal Question -- Carnot Engine

    Homework Statement A Carnot engine extracts 745 J from a 592-K reservoir during each cycle and rejects 485J to a cool reservoir. It operates 16 cycles per second. Find work, efficient, temp of cool reservoir. Homework Equations W = Qh - Qc n=Wout/QhThe Attempt at a Solution I'm sure I can do...
  35. T

    How Thick Should My Thermal Barrier Be to Protect Against Heat?

    Hello friends, I am having a hard time understanding thermal conduction and was hoping someone could shed some light for me. I am looking to protect a component from heat by placing a thermal barrier between it and the heat source, the heat applied to the surface of this barrier would be...
  36. B

    Thermal Conductivity of Springs

    I have a question that I've been debating with some co-workers. We are using conical springs (tapered) that most of the time in our application fully compress once engaged. We are measuring minute changes in temperature and I was wondering if a spring diffuses more heat compressed or relaxed...
  37. W

    Does thermal radiation occur within a material?

    Homework Statement I am doing an assignment with multiple heat transfers, and have to investigate the effects of including thermal radiation vs saying that thermal radiation is negligible. I know that the equation for thermal radiation is q = A*σ*(T14 - T24) (*) In my case the equation...
  38. H

    Thermodynamics or thermal physics

    What are some interesting experiments for doing research in thermal physics or thermodynamics?
  39. wololo

    What is the solution for finding F in terms of T and V without integrating?

    Homework Statement Homework Equations Maxwell relations The Attempt at a Solution I have an attempt at a solution, but I am not sure if I can replace the integral of dT in the helmholtz equation by the T I found using the internal energy. Does this make sense? Thanks
  40. B

    Reaction rates, temperature, and thermal energy

    Homework Statement Hi there. My question is more for clarification than a homework question. In my studies, I noticed that my MCAT study manual provides problems relating reaction rates and the effect that temperature and thermal energy have on a reaction. For example, a question asks: in an...
  41. I

    Linear Thermal Expansion of a Meter Stick

    Hello, If a thermal linear expansion happens to a meter stick, for instance a 50 m steel meter stick, the new length would be 50(1+(coefficient of expansion )(ΔT)). My question is would this also work if we choose different segment of the meter stick?For example, Can the new length for the part...
  42. J

    Steady State Heat Equation with Source

    I am trying to solve the steady state heat equation with a heat source. I am starting out in 1 dimension (my book gives the solution in 2, but I'm just trying to get a feel right now) and I have a heat source Q, located at 0. It radiates heat through an infinite medium. So what would the steady...
  43. 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...
  44. 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?
  45. 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?
  46. 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...
  47. 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)
  48. 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...
  49. 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?
  50. 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...
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