Convert kilocalorie (IT)/hour/meter/°C to calorie (th)/second/centimeter/°C • Thermal Conductivity Converter • Thermodynamics — Heat • Compact Calculator • Online Unit Converters (2024)

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Overview

Thermal conductivity is a property of an object to allow heat to move through it. This property is independent of the size of the object. It does, however, depend on the temperature. The higher the thermal conductivity of a material — the greater the heat transfer. For example, wool has much lower thermal conductivity than does metal, so if a child licks her mitten while outside in sub-zero temperature, nothing will happen to her. If she decides to lick a metal door handle, the heat from her tongue would quickly transfer to the metal, and the liquid on her tongue would likely get frozen and her entire tongue — stuck to the handle.

Thermal conductivity has many applications in technology and in everyday life. It is used for regulating body temperature, for cooking, and for making people’s life comfortable, among other things.

Uses for Thermal Conductivity

Thermal Conductivity in the Kitchen

Thermal conductivity is very important in cooking. Because metals conduct heat well but can withstand high temperatures, they are used to make pots and pans. When a metal pot is put on the heat source, it cooks the food by transferring this heat to the food. When one needs to control the overall conductivity, it can be decreased by choosing a pot made from different materials, or by adjusting the cooking method. For example, cooking on a double boiler reduces the overall conductivity because a metal pot that has direct contact with the heat has less conductive water inside, and then another pot with food is in the water. The maximum temperature of the inner container will not exceed 100° C (212° F), the boiling point of water. This works well with foods that burn easily or should not be boiled, like chocolate.

Copper and aluminum are some of the metals that have really good thermal conductivity, with copper being superior but more costly. Both of them are used for cooking, but some foods react with these metals, and this can leave a metallic taste in the food. This is especially a problem with acidic foods. These pots also need regular maintenance, especially the copper ones. Because of this, the less conductive stainless steel pots are more common.

Different types of cooking require different amounts of thermal conductivity, depending on the desired effect. For example, boiling assumes less conductivity than frying. This can be controlled by choosing the cookware, but adjusting the conductivity of the food products involved also helps. For example, controlling how much oil is used for frying influences thermal conductivity. The amount of other liquid in the pan also has an effect.

Not all of the materials used for making pans have high thermal conductivity. Ceramics, for example, do not conduct heat as well as metals do. Their main advantage is good heat retention — sometimes this is more important than good conductivity.

The stove is also a good example of the use of thermal conductivity. Heaters of an electric stove, for example, are made from highly conductive metals, to ensure that they transfer heat to the pot well.

To prevent burns people hold the highly conductive metal pots and lids by handles that are made from plastics and other materials with low thermal conductivity. Oven mitts are used for the same reason.

Materials with low thermal conductivity are used to keep the food’s temperature constant for a long time. For example, when going on a trip or taking lunch to work or to school, one may want to keep their soup or coffee hot. An insulated portable flask or cup is very useful in this situation. It keeps the food hot (or cold) because the space between its walls is filled with materials that have low thermal conductivity. Some examples of insulation include having a layer of air trapped between the external and the internal walls, or some styrofoam. Take-out coffee cups and containers are also made from styrofoam, to prevent the heat from escaping in the environment and to keep the drinks or the food hot. This insulation also protects the hands from burns. A portable vacuum flask (well-known under the brand name of Thermos) has very little air between the two walls, to reduce thermal conductivity even further.

Thermal Conductivity for Warmth

We use materials that have low thermal conductivity to prevent heat from escaping from our body. Wool, synthetic wool-like materials, and feathers are some examples. Animals and birds are generally covered by low-conductivity fur and feathers. We use these animal products or produce similar synthetic materials to make clothes and shoes for winter, and we also make blankets to sleep under, because our body temperature drops when we sleep and we need additional warmth. It is also more comfortable to use a blanket than thermal clothes because it is less restrictive, but in some extreme conditions, thermal clothes are necessary, because a blanket is not generally attached to the bedsheets, so if we move during sleep it may allow cold air through the gaps.

The problem with cold air is that if unrestricted, air can move freely, and the warm air escapes from around our body and is replaced by cold air. When the movement of air is restricted, like in insulated cups, it works as a good insulator because of its low thermal conductivity. Animals use this property of air as well in addition to the insulators above. For example, when the weather gets cold we can see birds with fluffed-up feathers. This allows them to trap air inside their feathers and to stop it from moving. Such additional layering increases their insulation and keeps them warm even in cold weather. People also have this mechanism — we get goosebumps when we are cold, although it is not effective anymore because we lost our fur during the evolution process.

Snow and ice also have relatively low thermal conductivity and are natural insulators. Snow often has air trapped inside of it, which allows for even better insulation because air’s thermal conductivity is lower than that of the snow. Both ice and snow preserve the plants in the ground from freezing. Animals sometimes hibernate in snow caves. People who hike in the snow occasionally do the same. Ice has been used to build shelters since ancient times, and there are entertainment facilities and hotels made from ice. They are often heated by fire and people use furs and synthetic sleeping bags at night. Visitors who stayed there report that they were comfortable and warm in their sleep, although they usually do not recommend leaving the bed at night to go to the bathroom. Because of the low thermal conductivity of ice, it is also possible to make votive candle holders from it, and there are many photo and video tutorials online on how to do that.

Animal and Human Internal Temperature Regulation

Bodies of animals and humans need to maintain a constant temperature within a very small range, to ensure that their internal processes run smoothly. Blood and other internal fluids, as well as tissue, have different thermal conductivity. Depending on the temperature in the environment, people and animals can increase or decrease the amount of blood that they circulate around all or parts of the body, to maintain this constant temperature. The amount of blood for circulation is regulated by widening or narrowing the blood vessels. The thermal conductivity of the blood itself can be regulated by changing its thickness.

Other Uses

People often enjoy relaxing in hot places like steam rooms or saunas, but when they want to sit down, they cannot sit on objects with high thermal conductivity such as metals, because, highly conductive materials cannot adjust to the body temperature quickly enough, and it is painful to sit on them. Wood and other materials that have low conductivity can adjust to the body temperature faster, this is why they are commonly used in saunas. People also often protect their heads from the heat by wearing woolen caps in the bath. Turkish baths known as hamams maintain lower temperatures inside, so the areas for relaxation use more conductive stone.

Some traditional baths, for example, the Japanese hot springs or onsens, are outside. Because the human body is insulated well with fat, which has relatively low thermal conductivity, people can enjoy these hot water baths even if the outside temperatures are below zero. People are not the only ones who discovered this wonderful property of the body: macaque monkeys also enjoy bathing in the natural hot springs in winter.

Thermal Conductivity of Common Materials

References

This article was written by Kateryna Yuri

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Compact Calculator Full Calculator Unit definitions

Online Unit Converters Thermodynamics — Heat

Thermodynamics — Heat

Thermodynamics is the branch of physics concerned with heat and its relation to other forms of energy and work. It defines thermodynamic variables (such as temperature, entropy, and pressure; they are also referred to as macroscopic variables) that describe average properties of material bodies and radiation, and explains how they are related and by what laws they change with time.

Thermal Conductivity Converter

Thermal conductivity is the physical value describing the ability of various materials to conduct heat. Heat transfer across materials of high thermal conductivity such as metals occurs at a higher rate than across materials of low thermal conductivity such as wood. Correspondingly materials of high thermal conductivity like copper are widely used in heat sink applications and materials of low thermal conductivity, for example, rigid polyurethane foam, are used as thermal insulation. Thermal resistivity is the opposite of thermal conductivity.

In SI units, thermal conductivity is measured in watts per meter kelvin (W·m⁻¹·K⁻¹). From these units, we can see that thermal conductivity is a measure of how much power moves through a distance due to a temperature difference. In Imperial units, thermal conductivity is measured in BTU/(hr·ft⋅°F). Other units which are closely related to the thermal conductivity are commonly used.

Using the Thermal Conductivity Converter Converter

This online unit converter allows quick and accurate conversion between many units of measure, from one system to another. The Unit Conversion page provides a solution for engineers, translators, and for anyone whose activities require working with quantities measured in different units.

You can use this online converter to convert between several hundred units (including metric, British and American) in 76 categories, or several thousand pairs including acceleration, area, electrical, energy, force, length, light, mass, mass flow, density, specific volume, power, pressure, stress, temperature, time, torque, velocity, viscosity, volume and capacity, volume flow, and more.
Note: Integers (numbers without a decimal period or exponent notation) are considered accurate up to 15 digits and the maximum number of digits after the decimal point is 10.

In this calculator, E notation is used to represent numbers that are too small or too large. E notation is an alternative format of the scientific notation a · 10^x. For example: 1,103,000 = 1.103 · 10⁶ = 1.103E+6. Here E (from exponent) represents “· 10^”, that is “times ten raised to the power of”. E-notation is commonly used in calculators and by scientists, mathematicians and engineers.

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• Alternatively, you can enter the value into the right To box and read the result of conversion in the From and Result boxes.

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