Heat

Why does metal feel colder or warmer than wood depending on the temperature?

Why does metal feel colder than wood (human thermal response)?

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Find out in this article why metal feels colder than wood of the same temperature, while at higher temperatures the metal suddenly feels warmer than wood. The property of an object to...
Convection current for radiators placed below a window

Why are radiators usually located under a window?

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Central heating systems use the principle of thermal convection. The water is heated by a central heater and then transferred to the radiators by means of pumps. It is thus a...
Design of a measuring device for the determination of thermal conductivity according to the Guarded-Hot-Plate Method (GHP)

Guarded-Hot-Plate method for determining thermal conductivity (GHP)

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With the Guarded-Hot-Plate method (GHP) the thermal conductivity is determined by the electrical power output of a hot plate with guided heat conduction. Learn more about this measurement method in this...
Heat transfer using the example of a central heating system

Heat transfer by thermal convection

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With heat transfer by thermal convection, heat is transported with a flowing substance. Convection only occurs in fluids, i.e. gases and liquids. You will find more information in this article. This article...
Melting metal

Specific latent heat of fusion (enthalpy of fusion)

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The specific latent heat of fusion (enthalpy of fusion) is the amount of heat required to melt a solid substance! Learn more about it in this article. Process of melting If a solid...
Comparison of volume between liquid water and gaseous water (water vapor)

Difference between latent heat of vaporization and enthalpy of vaporization

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For isobaric vaporization, the added heat of vaporization (process quantity) leads to a change in the enthalpy of the substance (state variable). Learn more about the different meaning of both terms...
Heat of condensation released during condensation of steam (water vapor) leads to severe burns

Why steam burns are more dangerous than water burns?

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Steam burns are more dangerous than water burns because more heat is transferred due to the additional release of latent heat of condensation. Learn more about it in this article. To vaporize...
Sprinkling a grapevine with water as frost protection

Vineyard Frost Protection (sprinkling with water)

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With sprinklers for frost protection, the crop stays protected from low temperatures by the heat of solidification released when the water freezes. Learn more about it in this article. If growing fruits...
Heating of a gas at constant volume (left) and constant pressure (right)

Specific heat capacity of gases (at constant volume or pressure)

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Due to compressibility of gases, a distinction must be made between the isobaric and the isochoric specific heat capacity. Learn more about this in this article. Differentiation between isochoric and isobaric heat...
Principle of thermal conduction in solids by oscillation of the atoms

Thermal conduction in solids and ideal gases

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The thermal conductivity in crystalline, non-metallic solids first increases and then decreases again with increasing temperature. Learn more about this behavior in this article. This article provides answers to the following questions,...
Assembly of a building wall to calculate the U-value

Thermal transmittance (U-value)

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The thermal transmittance (U-value or U-factor) describes the heat transfer through a solid object, which is located between two fluids (gas or liquid) with different temperatures. Learn more about it in...
Vaporization of water in a pot on a hotplate

Specific latent heat of vaporization

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The specific latent heat of vaporization (enthalpy of vaporization) is the amount of heat required to vaporize a liquid substance! Learn more about it in this article. Process of vaporization If a liquid...
Extinguishing fire with water using a fire extinguisher

Why does water extinguish fire?

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By absorbing a very large amount of heat during vaporization, water draws energy from the fire site and thus cools it down until the fire goes out! Learn more about it...
Influence of the hydrodynamic and thermal boundary layer on convective heat transfer

Nusselt number to describe convective heat transfer

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The Nusselt number is a dimensionless similarity parameter to describe convective heat transfer, independent of the size of the system. Learn more about it in this article. This article provides answers to...
Mean free path in a thin gas with low pressure and a dense gas with high pressure

Thermal conductivity of gases

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The thermal conductivity of ideal gases is not dependent on pressure for gases that are not too strongly diluted. This is no longer the case for gases with low pressure. Learn...
Final temperature when mixing two liquids

Final temperature of mixtures (Richmann’s law)

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Richmann's law of mixtures describes the final temperature resulting in thermodynamic equilibrium when two bodies with different initial temperatures are brought into contact. Learn more about it in this article. Adiabatic mixing If...
Definition of the heat transfer coefficient for convective heat transport

Heat transfer coefficient for thermal convection

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The heat transfer coefficient describes the convective heat transfer from a solid to a flowing fluid and vice versa! Learn more about it in this article. This article provides answers to the...
Heating a pot of water with a sausage in it

Heating and cooling of several objects

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Heating of several objects In practice, when heating or cooling objects, one usually has to deal with several materials that are heated or cooled simultaneously. Such simultaneous heating can be seen, for...
Definition of the thermal boundary layer (temperature boundary layer)

Thermal and concentration boundary layer

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In addition to the hydrodynamic boundary layer, the thermal boundary layer and the concentration boundary layer also have a decisive influence on the entire heat and mass transport in a flow....
Hydrodynamische Grenzschicht, thermische Grenzschicht und Konzentrationsgrenzschicht

Dimensionless numbers of the boundary layers (Prandtl, Schmidt and Lewis number)

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To describe the heat and mass transport, dimensionless numbers are introduced to describe the processes within the boundary layers. Learn more about this in this article. This article provides answers to the...
Heat flow through a wall by thermal convection and thermal conduction

Difference between thermal conductivity, diffusivity, transmittance, resistance and heat transfer coefficient

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Learn more in this article about the differences and importance of thermal conductivity, thermal diffusivity, heat transfer coefficient, thermal transmittance and thermal resistance, etc. Thermal conductivity Thermal conductivity (lambda) describes the heat transfer...
Specific heat capacity of water/ice/vapor as a function of temperature

Specific heat capacity of water

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The specific heat capacity is not a material constant for a substance, but depends on the temperature and above all on the state of matter. The dependence of the specific heat...
Design and principle of a thermos (vacuum flask), how does work

How does a thermos work? Design of a vacuum flask!

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The reason why hot tea or coffee stays warm for so long in a thermos is the special design of the flask. This design limits the different mechanisms of heat transfer...
Forestville (Canada) and Karlsruhe (Germany) at 49° North

Gulf Stream & global ocean conveyor belt

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The Gulf Stream is an ocean current in the Atlantic Ocean which, as part of the earth's global conveyor belt, has a decisive influence on the climate in Northern and Western...
Reducing the temperature of water by releasing energy as heat to ice cubes

Important remarks on the specific heat capacity

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Definition of the specific heat capacity The specific heat capacity (c) describes the relationship between a transfer of heat (Q) and the associated temperature change (Delta T) of a substance of mass...
Heat flow from a hot object to a cooler one

Rate of heat flow: Definition and direction

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The rate of heat flow refers to the heat energy transferred per unit of time ("heat output"). The drive for the heat flow is a temperature difference. Learn more about the...
Experiment to demonstrate heat transport by thermal conduction

Heat transfer by thermal conduction

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Heat transfer by thermal conduction means that heat is conducted through a material. Heat energy is transferred from molecule to molecule at the atomic level. More information on this topic can...
Sun as a blackbody with a surface temperature of 5778 K

Heat transfer by thermal radiation

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With thermal radiation, heat is transferred by electromagnetic waves without the presence of a substance! You can read more about this mechanism in this article. The mechanisms of thermal convection and thermal...
Determination of thermal conductivity with the Transient Hot Wire method (HTW)

Transient-Hot-Wire method method for determining thermal conductivity (THW)

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With the Transient-Hot-Wire method (THW), the thermal conductivity is determined by the change in temperature over time at a certain distance from a heating wire. Learn more about the experimental determination...
Convective heat transfer at a flat plate with laminar-turbulent flow

Calculation of the Nusselt numbers for forced flows over plates and in pipes

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In this article you will find formulas for calculating the local and average Nusselt numbers for forced flows over plates and in pipes with circular cross sections. This article provides answers to...
Lewis number as a measure for the ratio of the thickness of the thermal boundary layer and the concentration boundary layer

Lewis number

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The Lewis number is a dimensionless similarity parameter to describe heat and mass transport. Learn more about it in this article. This article provides answers to the following questions, among others What does...
Calorimeter for determining the specific heat capacity of liquids (calorimetry)

Calorimeter to determine the specific heat capacities of liquids

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Calorimetry deals with the measurement of heat energy.These measurements are based on temperature changes, which are used to determine the amount of heat involved. In calorimeters, for example, the specific heat...
Temperature as a function of time during melting

Why does the temperature remain constant during a change of state (phase transition)?

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During a change of the state of matter, the supplied energy is not used to increase the kinetic energy of the molecules, but to change the binding energies. Therefore, the temperature...
Design of a Laser-Flash-Analyzer (LFA) for the determination of thermal diffusivity conductivity

Laser-Flash method for determining thermal conductivity (LFA)

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With the Laser-Flash method (Laser Flash Analyser, LFA), the thermal conductivity is determined by the temperature rise in a test sample that is heated by a short laser pulse from one...
Experimental setup for the measurement of thermal conductivity

Experimental setup for determining thermal conductivity

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In this article you can learn more about the experimental determination of the thermal conductivity of materials using steam and ice. This article provides answers to the following questions, among others What...
Heat capacity of selected substances

Specific heat capacity of selected substances

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In this article, learn more about the specific heat capacity of different materials and how it affects the change in temperature over time during a heat transfer. Definition of the specific heat...
Thermal conduction through a house wall

Thermal conductivity (Fourier’s law)

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Thermal conductivity is a measure of how well or poorly a material conducts heat energy (measure of the strength of heat conduction)! You can read more about this in this article. This...
Velocity gradients in a laminar and turbulent boundary layer

Hydrodynamic boundary layer

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The hydrodynamic boundary layer of a flow has a decisive influence on heat and mass transport. Learn more about it in this article. This article provides answers to the following questions, among...
Temperature profile through the wall of a cylindrical pipe

Temperature profiles and heat flows through different geometries

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In this article we discuss temperature curves and heat flows through a plane wall, through a cylindrical pipe and through a hollow sphere. This article provides answers to the following questions, among...
Convective heat transfer between a heated pipe and a fluid flowing through it

Prandtl number

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The Prandtl number is a dimensionless similarity parameter to describe the transport of heat and momentum. Learn more about it in this article. This article provides answers to the following questions, among...
Vaporization and condensation using the example of boiling water on a hotplate

Specific latent heat of condensation

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Specific heat of condensation is the heat energy to be released for condensation of a gas per kilogram of the substance! Learn more about it in this article. Vaporization and condensation In the...
Melting and solidification (freezing) using the example of water and ice

Specific latent heat of solidification (enthalpy of solidification)

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Specific heat of solidification is the heat energy to be released for solidification of a liquid per kilogram of the substance! Learn more about it in this article. Melting and solidification In the...
Mixing temperature when pouring cold milk into a cup of hot coffee

Heat and thermodynamic equilibrium

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In thermodynamics, heat is the transport of energy due to a temperature difference. Heat in this respect is never "contained" in an object! Learn more about the thermodynamic concept of heat...
Soft drink (beverage) cooling with ice cubes

Cooling drinks with ice cubes (Derivation and calculation with formula)

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Learn more about calculating the final temperature of a drink when cooling with ice cubes in this article. Introduction (Excel spreadsheet for calculation) If you want to cool a warm drink relatively quickly...
Heat capacity of a stove made of different materials

Heat capacity of objects

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Heat capacity is the amount of heat required to raise the temperature of an object by 1 Kelvin (1 °C). Learn more about it in this article. Specific heat capacity of substances The...