What is Heat: Definition and 1000 Discussions

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. A

    Transient Heat transfer from water through pipe to ground

    Hi I am trying to do a transient heat transfer calculation. The water flowing through the pipe is laminar (1 m/s, id = 0.0127 m, Re_d = 0.01) transferring heat to the pipe via convection, then the pipe (od = 0.015875 m, l = 144 m) transfers heat to the ground again via conduction. I found this...
  2. V

    How calculate the Heat flux requiered to evaporate sub cool water

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  3. T

    Heat radiation between two non-parallel surfaces

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  4. S

    Kinetic energy of an electron or the whole atom to produce heat?

    Does electron really vibrate to produce heat energy or is it atom in whole to produce heat?
  5. B

    How can I calculate heat loss from a pipe system in a building with 9 floors?

    halo every one... i have question . if i have pipe inside building with 9 floor's length ,and i have calorie meter between the incoming and outgoing pipe's. how i can calculate the losses of pipe if i now that temperature inside building is 22. i want to be sure that the system working normal. i...
  6. F

    Exploring the Relationship Between Heat and Force in Molecular Breakage

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  7. A

    Solving PDE heat problem with FFCT

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  8. A

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  9. S

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  10. Idrees Afridi

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  11. M

    Phase of refrigerant crossing heat exchanger devices

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  12. J

    Understanding Heat: Exploring Molecular Jigglyness and Radiating Waves

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  13. L

    What is the Effect of Isothermal Movement on Internal Energy of a Gas?

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  14. L

    Problem with units for conduction rate?

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  15. L

    How much water is converted to ice?

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  16. D

    Specified equation of state from heat capacity

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  17. S

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  18. 1

    Calculating Heat Transfer in Copper Conductors: A Thermodynamics Question

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  19. C

    Is specific heat capacity always ignored in Steady State

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  20. Const@ntine

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  21. Jason Louison

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  22. K

    Time taken for heat transfer

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  23. C

    Two materials heated in vacuum

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  24. G

    Heat required to increase the temperature

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  25. prakhargupta3301

    Why isn't the Heat generated = Voltage*Charge carried?

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  26. C

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  27. OcaliptusP

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  28. D

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  29. D

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  30. A

    Can We Store Heat Generated by Azobenzene for Later Use?

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  31. D

    Heat and Mass Transfer Problem

    Homework Statement A plastic pipe (k=0.092 W/m.K) of inner and outer radius of 1 and 1.25 cm, respectively. If the inner and outer surfaces are at 60 °C and 30 °C, respectively. The rate of heat transfer per unit length is close to: a) 98 W/m b) 89 W/m c) 78 W/m d) 168 W/m e) 112 W/m...
  32. R

    Calculating Heat Loss in a Series Circuit

    Homework Statement Determine the heat loss in the circuit that is connected in series with two batteries (12 V and 6V) and two resistors (6ohms and 4 ohms). Homework EquationsThe Attempt at a Solution I used the difference in P = V^2/R, the power dissipated in the circuit, to calculate the...
  33. T

    Amount of energy required to heat a kg of water?

    So recently I've become familiar with concepts like specific heat, and we use a formula Q=mcΔT to calculate the Joules necessary to heat up say a kg of water from 50 to 70 degrees celsius. Now I was wondering if there is a equation that incorporates the amount of heat lost to the atmosphere...
  34. Zaya Bell

    Heat Transfer in Water: Convection, Expansion & Conduction

    Looking back to heat transfer by convection, which means denser molecules move down, lighter molecules move up. And then water at 4°C expands when cooled further, and at 0°C it contracts when heated. So if water at 0°C in a container is heated from the bottom, its molecules should...
  35. F

    Calculating Heat Loss in Pipes with Air Flow and Water Surrounding

    I am new and have a math and finance background. Because of my work I am starting to get into engineering related questions, specifically in piping. I flyfish a lot and can give pointers to anyone that helps me with my questions. Say I have a 5-10' length of pvc, metal or copper pipe that is 4...
  36. electr

    How Does Fuel Composition Affect Combustion Efficiency and Steam Generation?

    A fuel gas consists of 75% butane (C4H10), 10% propane (C3H8) and 15% butene (C4H8) by volume. It is to be fed to the combustion chamber in 10% excess air at 25ºC, where it is completely burnt to carbon dioxide and water. The flue gases produced are to be used to generate 5 bar steam from water...
  37. Quantum Velocity

    I How stuff in empty space cools down?

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  38. lonelypancreas

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    Homework Statement What is the net heat flow of an aluminum disk (emissivity = 0.05) with radius 10 cm and temperature 293K placed inside a room where the temperature is 300K? Asurface = π*r2 = 0.01π m2 Homework Equations Hnet = A*e*σ(Tradiate4-Tabsorb4) The Attempt at a Solution By simply...
  39. M

    Can Sound Absorbing Mats Reduce Noise from Central Heat & Air Units?

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  40. SciencyBoi

    Internal Energy of an Ideal gas related to Molar specific heat

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  41. H

    How to find added thermal heat in monoatomic gas?

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  42. J

    Thanks in advance.Heat Transfer Modeling: Get Insight for Physical Intuition

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  43. E

    Calculating the mass of water from Temperature and Heat Added

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  44. P

    How much energy does a bar of iron radiate after losing 8.0 × 10^6J?

    A bar of iron is 0.5m long, 0.2m wide and 0.1m high (which means its volume is 1.0 × 10−2m3 and its surface area is 3.4 × 10−1m2 ). Iron has a density of 7900 kg m3 , a heat capacity of 400 J kg◦C , and a coefficient of linear expansion of 1.2 × 10−5 . The bar of iron is initially at 600K...
  45. F

    Trouble with Galilean transform problem heat equation

    Homework Statement 1. The common form of the heat-diffusion equation governing the temperature distribution $$\rho C_p \frac{\partial T}{\partial t}=k\nabla^2T$$ Is this equation valid in any inertial frame of reference? (i.e. does it have the property of Galilean invariance?) If not, can it...
  46. H

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  47. A

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  48. oversight

    How do I measure the temperature of my infrared sauna?

    Sooooo... I have a Far infrared (FIR) sauna. It has large flat 'carbon' panel heaters. They get warm to the touch and won't burn you if you touch them. My non contact infrared thermometer zapper says that they get to about 70 degrees C. They are meant to be producing lots of FIR. A regular...
  49. E

    Linear expansion by heat for an object

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  50. Vitani11

    Help with understanding BVP for the Heat equation (PDE)?

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