Home Thermodynamics

# Thermodynamics

### Why does ice form on the top of a lake?

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Learn in this article why ice form always on top of a lake in winter. The negative thermal expansion of water (density anomaly) has an existential importance for life on earth. More...

### 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...

### 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...

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### 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....

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### 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...

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### 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...

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### Thermodynamic derivation of the Stefan-Boltzmann Law

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In this article the Stefan-Boltzmann-Law is to be derived using the laws of thermodynamics. This article provides answers to the following questions, among others: How can the Stefan-Boltzmann law be derived from the...

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### 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...

### 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...

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### 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...

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### 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...

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### 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...

### 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...

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### 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...

### 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...

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### 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...

### 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 thermal convection, thermal conduction and thermal radiation. You can read...

### The process quantities: Heat and work

Work and heat are process quantities that describe the process of a supply of energy ("energy in transit")! Learn more about it in this article. Work and heat transferred to a substance Energy...

### Internal energy & first law of thermodynamics

Internal energy is the sum of the different forms of energy on a microscopic level inside a substance. Learn more about it in this article. Energy transfer as heat and as work In...

### Thermodynamic systems

A thermodynamic system is a confined space of matter (e.g. gas) within which thermodynamic processes take place. The system boundary separates the system from the environment. Learn more about it in...

### Stefan-Boltzmann law & Kirchhoff’s law of thermal radiation

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The Stefan-Boltzmann law states that the radiant power of an object in thermal equilibrium is proportional to the fourth power of temperature and directly proportional to its surface! Learn more about...

### Internal energy & heat capacity of ideal gases

This article provides answers to the following questions, among others: What is the internal energy of a gas?What are the characteristics of the thermal energy of a gas?What is meant...

### Derivation of the Maxwell-Boltzmann distribution function

The Maxwell-Boltzmann distribution function of the molecular speed of ideal gases can be derived from the barometric formula. This article shows the derivation. Introduction For ideal gases, the distribution function (f(v)) of the...

### Equipartition theorem

This article provides answers to the following questions, among others: What statement does the equipartition theorem provide?What is a degree of freedom in the thermodynamic sense?Why does a direction of oscillation have...

### Ideal gas law (explained and derived)

The ideal gas law describes the relationship between pressure, volume, mass and temperature of ideal gases. Learn more about it in this article. Parameters influencing the gas pressure The figure below shows a...

### How does a thermal imaging camera work?

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This article provides answers to the following questions, among others: How do thermal imaging cameras work?Why is the thermal image displayed in false colors? Thermal imaging cameras are based on the same principle...

### How does a infrared thermometer (pyrometer) work?

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This article provides answers to the following questions, among others: How do IR thermometers (pyrometers) work?What are the advantages of pyrometers? The thermometers presented in the previous articles must directly touch the object...

### How does a thermocouple work?

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This article provides answers to the following questions, among others: How does a thermocouple work?What is the Seebeck effect?What are the differences between the types of thermocouples?What is cold junction compensation?What are...

### How does a resistance temperature detector (resistance thermometer) work?

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This article provides answers to the following questions, among others: How do resistance thermometers work?Why should the measurement current for an RTD be as low as possible?How can the temperature be determined...

### How does a vapour pressure thermometer (vapour-in-metal) work?

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This article provides answers to the following questions, among others: How do vapor pressure thermometers work?Why do vapor pressure thermometers have a non-linear scale? The less popular vapour pressure thermometers work according to...

### How does a gas filled thermometer (gas-in-metal) work?

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This article provides answers to the following questions, among others: How do gas filled thermometers work?What are the advantages of gas-in-metal thermometers compared to liquid-in-metal thermometers?How can the influence of the...

### How does a liquid filled thermometer (liquid-in-metal) work?

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This article provides answers to the following questions, among others: How do a liquid-in-metal thermometers work?Why should the inner diameter of the coiled tube be kept as small as possible?How can large...

### How does a bimetallic strip thermometer work?

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This article provides answers to the following questions, among others: How do bimetal thermometers work?Why is the bimetal wrapped into a spiral or a helix?Why are some bimetal thermometers equipped with switch...

### How does a liquid-in-glass thermometer work?

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This article provides answers to the following questions, among others: How do liquid thermometers work?What properties must thermometric liquids have?Why is mercury hardly used as a thermometer fluid nowadays?Which liquids are predominantly...

### Determination of the speed distribution in a gas

This article provides answers to the following questions, among others: How can the speeds of the particles in a gas be determined experimentally?What is a histogram?What is a relative frequency distribution?How does...

### Pressure and temperature

This article provides answers to the following questions, among others: What is the kinetic theory of gases?What are the assumptions on which the kinetic theory of gases is based?How can the pressure...

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### Maxwell–Boltzmann distribution

The Maxwell-Boltzmann distribution describes the molecular speed distribution of ideal gas molecules. Find out more in this article. This article provides answers to the following questions, among others: What is the Maxwell-Boltzmann distribution?For...

### Why do liquids evaporate?

This article provides answers to the following questions, among others: How can the evaporation of liquids be explained?Why does a cooling effect occur during evaporation?Why does one freeze faster with wet skin...

### Temperature scales

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This article provides answers to the following questions, among others: What is temperature in the physical sense a measure for?Which reference points are used as the basis for the Celsius scale and...

### 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...

### Temperature and particle motion

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This article provides answers to the following questions, among others: What is the general relationship between the temperature and the particle movement of a substance?Why does the volume of a substance usually...

### Particle model of matter

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This article provides answers to the following questions, among others: What is the particle model of matter?How can the solid, liquid and gaseous states of matter be explained with the particle...