Heat Definition and 1000 Threads

In thermodynamics, heat is energy in transfer to or from a thermodynamic system, by mechanisms other than thermodynamic work or transfer of matter. The various mechanisms of energy transfer that define heat are stated in the next section of this article.
Like thermodynamic work, heat transfer is a process involving more than one system, not a property of any one system. In thermodynamics, energy transferred as heat contributes to change in the system's cardinal energy variable of state, for example its internal energy, or for example its enthalpy. This is to be distinguished from the ordinary language conception of heat as a property of an isolated system.
The quantity of energy transferred as heat in a process is the amount of transferred energy excluding any thermodynamic work that was done and any energy contained in matter transferred. For the precise definition of heat, it is necessary that it occur by a path that does not include transfer of matter.Though not immediately by the definition, but in special kinds of process, quantity of energy transferred as heat can be measured by its effect on the states of interacting bodies. For example, respectively in special circumstances, heat transfer can be measured by the amount of ice melted, or by change in temperature of a body in the surroundings of the system. Such methods are called calorimetry.
The conventional symbol used to represent the amount of heat transferred in a thermodynamic process is Q. As an amount of energy (being transferred), the SI unit of heat is the joule (J).

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  1. R

    Engineering Heat Capacity and the Coefficient of thermal expansion

    thanks!
  2. Steven Bolgiano

    Does Copper Conduct Heat Better than cPVC?

    Hi Folks, I'm 70, so I often confuse myself! Ha ! My question is: Do materials both absorb and release heat equally? So when I evaluate different materials for thermo efficiency, does a copper pipe's surface absorb solar heat at the same rate it gives off heat? My question is specific to a...
  3. dRic2

    Two-phase flow heat transfer coefficient

    Hi, I'm looking to find a very very basic model to calculate the heat transfer coefficient in a tube with given heat power exchanged ##Q##. The fluid inside the tube starts sub-cooled (##T_{in}## is known) but exits the tube with a quality of steam around 0.15 (pressure is supposed constant)...
  4. mavidias

    Heat Engine Problem - Get Help Now

    Please help answering
  5. M

    How can I calculate the heat transfer in an air to air heat exchanger?

    I am considering building this type of heat exchanger, as I have seen several youtube videos on the build. The inside tube is aluminum, I am planning on building one from the top of my roof to nearly the floor, so ill say 5 feet. I am thinking of using a 1.5" inch aluminum tube, and bringing in...
  6. K

    I Heat Wave Equations: Explaining Delta t & x Approach to Zero

    When the delta t and x approached zero, assumably it results in the whole fraction to be zero. The slide shows it will be ##k^2##. Can someone explain this to me, please? P.S. I have tried to search this up, I could not find anything related to the confusion.
  7. J

    Debye Approximation of Heat Capacity in 1D

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  8. J

    Heat related problem -- Mercury solidifying liberates some energy

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  9. russ_watters

    What factors affect heat rejection in vacuum pump systems?

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  10. Nusselt

    Heat transfer problem for a long rectangular bar

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  11. Mark Everglade

    Gravity, heat, flooding, and centrifugal force on a tidal-locked planet

    Hi. I'm a science fiction author whose first novel Hemispheres, published through RockHill Publishing, explored a tidal-locked planet (Gliese 581g) where a group of activists increased its rotation to bring daylight cycles to both hemispheres. Now I'm writing the sequel, and there's ecological...
  12. M

    Optimizing Air Flow for CO2 and Heat Loss in Vans

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  13. J

    Can Heat Transfer Through Conduction Occur at Relativistic Speeds?

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  14. Mikkel

    Meridional Heat Transfer - Ocean and Atmosphere

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  15. Gaby

    Heat Transfer and Thermofluilds

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  16. A

    Heat Capacity of a Van Der Waals' gas in an Open system

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  17. B

    Heat dissipated by a steel disk

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  18. Steven Bolgiano

    Differences between these materials for absorbing and radiating heat?

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  19. phyzguy

    Efficiency of a heat engine in space

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  20. Spinnor

    Misc. Bending a spring steel rod to shape and heat treat, DIY?

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  21. jaumzaum

    Air conditioner without heat output - Is it possible?

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  22. K

    Surface integral: Calculate the heat flow from a cylinder

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  23. cwill53

    Specific Heat Capacity Derivation

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  24. M

    Heat Transfer: Effect of a Heat Fin

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  25. G

    Car Radiator as Air-to-Water Heat Exchanger

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  26. Z

    Cylinder in a heat bath @ 0C contains water and ice & is compressed

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  27. E

    Rate of conduction heat transfer with different hot-side and cold-side areas

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  28. P

    Relationship between Cp, Cv and R

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  29. T

    NTC thermistor heat dissapation calculation with graphs

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  30. H

    What percentage of heat is generated from LED lighting?

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  31. A

    Thermal energy/ heat in a parallel connection

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  32. bsharvy

    Energy Conservation and the Dragons (Game of Thrones)

    I thought I'd calculate how much heat was required to melt the Iron Throne, and then multiply that by the number of flame-gushes during the sack of Kings Landing, to get a total amount of energy expended. Then I'd convert that to calories and use the average number of calories per goat to...
  33. P

    Calculating Bricks for Winter Overnight Heat Storage in Stove

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  34. TechieDork

    Need help with calculating a Cv in PHYWE's Heat Capacity of gases

    I've conducted this experiment yesterday. The main goal of this experiment is to find a gas constant R and compare it with its theoretical counterpart but I get stuck in calculating a Cv so I tried to find out what's wrong with my calculations by trying to calculate a Cv from the given data...
  35. M

    B Low entropy early Universe and the heat death musings

    I came upon a realization recently. The early universe is always described to have begun in a state of extremely low entropy and it's been increasing ever since. But the same amount of stuff exists now as it did back then. Only thing that's changed is how big the universe is now vs then. So...
  36. P

    Heat engine that uses a rubber band (Thermodynamics)

    Nota that the path a to b is isothermal since J is proportional to L, then we can find the value of T_a and T_b using the equation of state and the figure. We have, \begin{equation} J_0=\alpha L_0T_b \end{equation} or \begin{equation} T_b=T_a=\frac{J_0}{\alpha L_0}=T_0 \end{equation} Also, by...
  37. Tom Booth

    Should ice take longer to melt when used to run a heat engine?

    If a heat engine converts heat into "work", will ice used to run a Stirling heat engine last longer than ice allowed to melt by itself? To try and answer this, I obtained a Stirling engine and ran this experiment: With the engine running: And not running: Without the engine running the...
  38. B

    Clausius clapeyron and heat capacity

  39. N

    Thermodynamics: phase change and latent heat problem

    The second question is where I'm lost. The answer to the first question is 5.39 grams. The second is 10.3 grams. Until I saw the answer I was setting the equation up as if some of the original steam had condensed. But it appears that some of the original water changed into steam. Is it necessary...
  40. GooseyGabe

    Does the rate of which something melts/vaporizes increases with heat?

    Something I've been thinking about recently is like how much heat would it take to evaporate an entire lake in less than a second. Or something like Tungsten Steel. The main question is does an increase in heat increase the rate of its change in structure? Sorry for the boring question.
  41. S

    Peak Amps of a heat pump based AC vs compressor based AC?

    In my city (USA) typical older houses have "100 Amp service" so their peak electric usage is limited to 100 Amps. In considering what sort of electric air conditioning system to install in such a house, peak usage is major consideration. Generally speaking, which type of residential unit...
  42. fluidistic

    I Heat transfer coefficient and convection

    I would like to fully understand two parameters involved in convection heat transfer systems. I have read the document https://fenicsproject.org/pub/tutorial/sphinx1/._ftut1005.html, and I am interested in the parameters ##r## and ##s## in eq. 69. As far as I understand, when one solves the...
  43. Like Tony Stark

    Determine the heat capacity at a constant volume for a Van der Waals gas

    Hi, what I've done so far is solving equation 2) for ##U##, and replacing what I get in equation 1). Then, ##c_V## is equal to the partial derivative of ##S## with respect to T times T, so I've done that. The derivative is ##CNR/T##, so ##c_V=CNR## but those aren't the correct units for ##c_V##.
  44. J

    Thermodynamics Problem: Finding Heat Transfer

    I have come across this problem from this booklet: https://www.ioc.ee/~kalda/ipho/Thermodyn.pdf
  45. jaumzaum

    What chemical properties affect the specific heat?

    Hello all! I would like to know what chemical/physical properties influencies the specific heat. For example, why are specific heat of metals smaller than the specific heat of water, and why do ice and steam have a smaller specific heat than liquid water do.
  46. T

    Grade 9 Physics (Heat fusion, Heat Capacity)

    Q1=2.5(390)(90-30) =58500 Q2=2.5(4000) = 10000 Qtotal = 58500+10000 Q=68500 =6.8x10^4 my teacher sent this as a homework but the options were 4.9x10^4 J 1x10^4 J 6.8x10^5 J 5.9x10^4 J im confused is is this a typo or did i do something wrong
  47. T

    Laten heat of fusion calculation

    Q1 = m(ice) * Cv * ∆T = amount of heat the ice absorbs Q2 = m(H2O) * Lf = amount of heat the water loses Q1 = (4*8 g) * (2198 J/g*K) * (0-(-15)) = 1.055 * 10^6 J Q1=Q2 Q2 = 1.055 * 10^6 J = m(H2O) * Lf Lf = 1.055 * 10^6 J / m(H2O) = 1.055 * 10^6 J / (0.25 L * 1000 g/1L) = 4220 J/g My answer is...
  48. C

    Solve Heat Pump COP Equation with Q & T

    I have tried to solve this with these equations: COP=T(H)/( T(H)-T(L) ) and COP = Q(H)/ ( Q(H)-Q(L) ) But since I need both Q and T in the same equation, I can't find anything to solve it.
  49. FEAnalyst

    Radiation heat transfer between parallel plates

    Hi, the approximate (not accounting for plate size and separation distance) formula for heat flux exchanged via radiation between two parallel plates is: $$q=\frac{\sigma (T_{1}^{4}-T_{2}^{4})}{\frac{1}{\varepsilon_{1}}+\frac{1}{\varepsilon_{2}}-1}$$ where: ##\sigma## - Stefan-Boltzmann...
  50. mastermechanic

    Undefined log-mean temperature in heat exchanger design

    For a course project, I need to design a heat exchanger to cool electronic components in an UAV. The heat exchanger will be cross-flow air to liquid. The cold side (air side) properties are evaluated at an altitude of 7620 m and -34.5 °C. For the hot side ethylene glycol - water solution with a...
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