Heat

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. To vaporize a liquid, energy as heat must be...
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! The simple answer to this...
Supply of heat of fusion during melting and dissipation of heat of solidification during freezing

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! Melting and solidification In the article on specific latent heat of fusion,...
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! Process of melting If a solid is heated more and more, then at...
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! Vaporization and condensation In the article on specific latent heat of vaporization,...
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! Process of vaporization If a liquid is heated more and more, then at...
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...
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. Adiabatic mixing If two bodies with different initial temperatures are...
Heating a pot of water with a sausage in it

Heating and cooling of several objects

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Learn more about calculating the final temperature of several objects with different temperatures in this article. Heating of several objects In practice, when heating or cooling objects, one usually has to deal with...
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...
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. Test setup The experimental setups used in calorimetry are...
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. Differentiation between isochoric and isobaric heat transfer Unlike liquids or solids, gases are special...
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 of water depends on the temperature and is strongly dependent on the state of matter. The specific heat capacity is not a material constant for a substance, but...
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...
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 ΔT of a substance of mass m: begin{align}label{q}&...
Setup for the experimental determination of the specific heat capacity of water

Specific heat capacity (derivation and definition)

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The specific heat capacity indicates how much heat must be absorbed by a substance of mass 1 kg in order to increase its temperature by 1 K (1 °C). Introduction The temperature of...
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...

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...
Convection current for radiators placed below a window

Why are radiators usually located under a window?

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Learn in this article, why radiators are usually located under a window? Central heating systems use the principle of thermal convection. The water is heated by a central heater and then transferred...
Hydrodynamic, thermal and concentration boundary layer

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. Between a flowing fluid and a solid surface, different boundary layers are formed,...
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. Temperature...
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. Definition In the article on the different boundary layers, the importance of these boundary layers with respect...
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. The Lewis number always comes into play when a flowing fluid is transferring both heat by conduction and...
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. Nusselt number The definition and importance...
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! Introduction The heat transfer coefficient describes the convective heat transfer from a solid to...
Definition of the hydrodynamic boundary layer (velocity 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. Introduction In this article we take a closer look at the boundary layers between a solid surface...
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. Introduction Convective heat transfer describes the heat transport between a solid surface and...
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. Introduction Temperature differences cause heat flows. These heat flows, in...
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. Phonons: Quasiparticles of the lattice vibrations Thermal conduction refers to the transfer of thermal energy through a...
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...
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. Design With the transient-hot-wire method, the thermal conductivity...
Design of a Heat-Flow-Meter for determining thermal conductivity (HFM method)

Heat-Flow-Meter method for determining thermal conductivity (HFM)

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With the Heat-Flow-Meter method (HFM) the thermal conductivity is determined by comparative measurement of the heat flow using a reference sample. Thermal conductivity Thermal conductivity is a measure of how well or poorly...
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. Thermal conductivity Thermal conductivity is a measure of how well...
Temperature distribution along a heated thin rod

Derivation of heat equation (diffusion equation)

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The heat equation describes the temporal and spatial behavior of temperature for heat transport by thermal conduction. Derivation of the heat equation We first consider the one-dimensional case of heat conduction. This can...
Mean free path and mean speed of molecules in a gas

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. Introduction In the...
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. Thermal conductivity Thermal conductivity is a measure of how well or poorly...
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. Definition and unit of the U-value The...
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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Learn more about the structure of a vacuum flask and how a thermos works in this article! The reason why hot tea or coffee stays warm for so long in a thermos...
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! The mechanisms of thermal convection and thermal conduction explained in separate articles have one thing in common:...
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. Introduction One possibility of heat transfer is that hot substances flow...
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. Introduction The principle of thermal convection can basically...
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. Direction of the heat flow If...
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)! Thermal conduction In general, heat can be transferred in three different...
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! Equalization of temperature of two substances Everyday experience shows that...
Thermal image of a cup with hot tea and a building

Heat transfer (heat transport)

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Heat transfer is the transport of thermal energy from a warmer object to a cooler object. A distinction is made between convection, conduction and radiation. Example 1: Building The figure below shows a...
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...