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. F

    Heat conduction between 2 objects

    Can someone tell me if my logic is correct here. I am trying to figure out how the cross sectional area to make the heat transfer from one object be the maximum amount of heat transfer with the minimal amount of area... I know the thermal transfer coefficient is watts per (meter*kelvin). I find...
  2. Rizwan Yaseen

    How to Convert Heat Capacity Equation Units to British Engineering System?

    How we change the units of Heat capacity equation to British engineering system Cp=2. 657*10^4 +42. 37T - 1. 425*10^-2T^2
  3. V

    Examples of conversion of gravitational PE to heat energy?

    Homework Statement I was looking for some examples where gravitational potential energy is converted to heat energy. Are there many such examples of this conversion? I could only come up with one such example and even that could be an incorrect example. Homework Equations PEg = mgh The...
  4. G

    Stirling cycle: Why neglect isochoric heat transfers?

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  5. P

    Method for determining the latent heat of oils

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  6. Carlos

    Heat capacity as a function of T under 298 K for metals

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  7. G

    Definition of efficiency of a thermodynamic cycle

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  8. Nacho Verdugo

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  9. rachel6589

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  10. B

    How Energy Is Spread In An Electric Kiln

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  11. V

    How to apply the First Law of Thermodynamics to this problem?

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  12. Jeremy Thomson

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  13. D

    Fourier/heat problem involving hyperbolic sine

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  14. V

    Heat energy in an inelastic collision

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  15. Carlos de Meo

    Heat exchange, emissivity and reflectance

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  16. N

    Molar heat capacity at constant pressure/volume

    Morning I am being stupid but cannot work out these problems: 1. Energy supplied to 2.0 moles of an ideal gas is 117J and it changes the temperature by 2.0K (at constant pressure).2. Calculate both molar heat capacities at constant P and V.3. Firstly, I divided 117J by 4 to get the energy...
  17. P

    Heat Transfer: Finding temperature at the junction

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  18. J

    Understanding Convection Heat Transfer in a Convection Heat Exchanger

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  19. G

    Algebra problem involving work using specific heat ratio

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  20. B

    Maximum vapor velocity from a heat exchanger into a turbine

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  21. A

    The latent heat of crystallisation of sodium chlorate

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  22. A

    Calculating the heat released in one part of an electrical network?

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  23. danyull

    Efficient Heat Engine and Final Temperature Calculation

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  24. C

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  25. H

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  26. durant35

    I Can a finite universe end in heat death?

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  27. AndyCh

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  28. S

    Working out heat transfer flux in a pipe

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  29. M

    Heat Transfer, Finite difference, Curved geometry

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  30. gsyz

    How can heat capacity be determined when both pressure and volume are changing?

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  31. heartshapedbox

    Latent heat and specific heat in insulated container

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  32. D

    Insulated bulbs immersed in heat reserviors

    Homework Statement Two glass bulbs of equal volume are connected by a narrow tube and are filled with a gas at ##0^{\circ}C## and a pressure of ##76\text{ cm}## of mercury. One of the bulbs is then placed in melting ice and the other is placed in water at ##62^{\circ}C##. What is the new value...
  33. F

    Radiating sphere inside spherical shell - heat transfer

    Homework Statement A sphere of radius r_s is at the center of a spherical shell of inner radius r_i=10\, r_s and thickness s = 10\, {\rm cm}\ll r_i. The sphere has a temperature T_s=1073\, {\rm K} and and an emissivity e=0.90. The inner surface of the shell has a temperature T_i = 873...
  34. N

    Change of variables in Heat Equation (and Fourier Series)

    Q: Suppose ##u(x,t)## satisfies the heat equation for ##0<x<a## with the usual initial condition ##u(x,0)=f(x)##, and the temperature given to be a non-zero constant C on the surfaces ##x=0## and ##x=a##. We have BCs ##u(0,t) = u(a,t) = C.## Our standard method for finding u doesn't work here...
  35. A

    Optimizing Heat Transfer in Boiler Tubes: Tube Number & Length Calculations

    Homework Statement flue gases = 50,000kg h^-1 surface area = 113.57m^2 Do = 25 + (3*2) = 31mm The tubes within a boiler are 25mm inside diameter with a wall thickness of 3mm. The flue gas velocity through the tubes is to maintain the overall heat transfer coefficient value and minimise...
  36. A

    Heat produced when a dielectric is inserted into a capacitor slowly

    if a capacitor is connected to a battery and then it is fully charged . then a dielectric slab of k is inserted in the capacitor while the battery is still connected SLOWLY my question is will there be any heat produced?? my approach -- after insertion of dielectric , the charge on the...
  37. W

    Clarification about Heat Conduction equations

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  38. Brunolem33

    B What fueled the Big Bang explosion?

    When, as a layman, I read or hear about the Big Bang, it generally comes to the same issues: massive release of energy, very high temperatures, very fast expansion, questions about what came before the Big Bang and so on. Yet, there are some issues that, at least to me, appear to be left aside...
  39. Saharka

    Heat of combustión of a mixture of two substances?

    Hello chemists, need some help here. I'm trying to calculate the power output of a certain otto cycle using different fuels, specifically gasoline, ethanol and different combinations of the two like 85% ethanol and 15% gasoline or 50% ethanol and 50% gasoline. However I have found it difficult...
  40. A

    Around how much do hot plate heat knobs increase per number?

    In my labs we use hot plates with a 0-10 temperature knob. The hot plates don't have a temperature monitor, so i have no idea how hot each number can increase it or how hot it is at the time. Sometimes i have labs where i have to heat something to more specific temperatures or else the reaction...
  41. pangru

    I Why does the heat capacity of solids drop exponentially at low temperatures?

    According to Einstein (or Debay) model of solids, heat capacity drops exponentially at low temperatures: question is >> why it changes so dramatically at low temperature that is physical explanation of this?
  42. T

    Figuring heat exchanger's surface temp

    Homework Statement Calculate surface temp of heat exchanger when it's heating the room with the known power of P. Room temperature T is also known, as is the heater surface area A. ε ≈ 1. Homework Equations P = εσAT^4 is what I've been trying to use. The Attempt at a Solution I've been...
  43. T

    Why does RMS power produce the same heat as the equivalent DC power?

    Hello. I was browsing online to answer the question to why RMS voltage is used as opposed to the average voltage (and by average I mean over half a period, roughly 0.64V_peak), and the explanation I found was that the RMS voltage would produce the same heat as equivalent DC through a resistor...
  44. U

    How is heat exactly measured in DSC

    In order to obtain DSC curves the instrument has to measure a HEAT when changing the temperature. During the measuring cycle with increasing temperature, I bet the heat is measured via Joule heating. But how is the sample cooled down together with measuring required heat during a cooling cycle?
  45. N

    What Is the Final Temperature of a Squeezed Hot Pack with LiCl and Water?

    Homework Statement What is the final temperature in a squeezed hot pack that contains 23.9 g of LiCl dissolved in 107 mL of water? Assume a specific heat of 4.18 J/(g⋅∘C) for the solution, an initial temperature of 25.0 ∘C, and no heat transfer between the hot pack and the environment...
  46. Manaf12

    Measuring the h conv from velocity not the same as that he gave

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  47. UdayShah

    Heat Exchanger Vs Cooling Tower?

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  48. L

    Heat Transfer. Ice and steam in a container (easy)

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  49. Joshua L

    What are the considerations for analyzing current through thin gold wires?

    Hey all, I've been thinking of a couple scenarios that involve thin wires (ones that have their diameter in the order of 1 mm). Suppose a gold wire with length L and diameter D is suspended straight in room temperature air and connected to some voltage V. Thus, a current will pass through the...
  50. B

    [PoM] Rotational and vibrational heat capacity

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