Which conducts heat better, steel or aluminum?

Which has better heat dissipation: aluminum or copper?

I was somehow also puzzled by the aluminum-copper problem for the radiator.
I bought aluminum. The idea was this: copper conducts heat better, but a lot depends on the shape. A copper radiator is thinner and has much fewer fins than an aluminum one. IMHO, aluminum will have a larger cooled surface area. . Incorrect installation. The fact is that due to the better heat dissipation properties of copper, the smaller area of ​​the copper radiator is identical in heat transfer to the larger surface of the aluminum

My copper one is 2 centimeters thick, as opposed to probably 6-8 cm of aluminum, but it works better.

In addition, do not forget that if the copper one is made at a factory, and not in the basement, then its plates are soldered. to the tubes and not crimped like on aluminum, and this greatly improves heat transfer.

The installation is no more incorrect than comparing a 16-year-old clogged aluminum radiator with a new copper one by eye. No wonder it works better.

IMHO, the incorrect setting is contained in the phrase: “The fact is that due to the better heat-removing properties of copper, the smaller area of ​​the copper radiator is identical in heat transfer to the larger surface of the aluminum one.” There are concepts: heat capacity, thermal conductivity and heat transfer. For example, for a computer radiator, both thermal conductivity and heat transfer are equally important - heat must first be effectively removed from a point source (crystal), and then effectively dissipated. In a car radiator, the thermal conductivity of the material plays a lesser role (the tubes are thin, the losses due to thermal conductivity are small, the liquid is inside the tubes), but heat transfer plays a huge role, which depends not so much on the material and its thermal conductivity, but on the shape of the radiator and the area of ​​its cooled surface.

It would also be nice, when quoting is used, not to cut off important sentences, somewhat distorting the meaning. (I repeat once again: “These are obviously speculative conclusions. Of course, it would be nice to measure heat transfer in laboratory conditions, but who would do it.”). This is so, by the way, it had to be.

Source

What heats up slower, water or land?

Sushi has greater thermal conductivity and cools more slowly due to its greater heat capacity! Several centimeters (or meters) of the surface of the land warm up. And the layers of water, mixing, absorb more heat.

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A little about thermal conductivity

In physics, thermal conductivity is understood as the movement of energy in an object from more heated small particles to less heated ones. Thanks to this process, the temperature of the object in question as a whole is equalized. The magnitude of the ability to conduct heat is characterized by the thermal conductivity coefficient. This parameter is equal to the amount of heat that a material 1 meter thick passes through a surface area of ​​1 m2 for one second at a unit temperature difference.

Copper has a thermal conductivity coefficient of 394 W/(m*K) at temperatures from 20 to 100 °C. Only silver can compete with it. And for steel and iron this figure is 9 and 6 times lower, respectively (see table). It is worth noting that the thermal conductivity of products made from copper largely depends on impurities (however, this also applies to other metals). For example, the rate of heat conduction decreases if substances such as:

Copper wire

If you add zinc to copper, you get brass, which has a much lower thermal conductivity coefficient. At the same time, adding other substances to copper can significantly reduce the cost of finished products and give them characteristics such as strength and wear resistance. For example, brass is characterized by higher technological, mechanical and anti-friction properties.

Since high thermal conductivity is characterized by rapid distribution of heating energy throughout the entire object, copper is widely used in heat exchange systems. At the moment, radiators and tubes for refrigerators, vacuum units and cars are made from it for rapid heat removal. Copper elements are also used in heating installations, but for heating.

Copper heating radiator

In order to maintain the thermal conductivity of the metal at a high level (and therefore make the operation of copper devices as efficient as possible), forced airflow by fans is used in all heat exchange systems. This decision is due to the fact that as the temperature of the environment increases, the thermal conductivity of any material decreases significantly, because heat transfer slows down.

The concept of thermal resistance and thermal conductivity coefficient

If thermal conductivity characterizes the ability of metals to transfer the temperature of bodies from one surface to another, then thermal resistance shows an inverse relationship, i.e. the ability of metals to prevent such transfer, in other words, to resist. Air has high thermal resistance. It is he who, most of all, prevents the transfer of heat between bodies.

The quantitative characteristic of the change in temperature of a unit area per unit of time by one degree (K) is called the thermal conductivity coefficient. The international system of units usually measures this parameter in W/m*deg. This characteristic is very important when choosing metal products that must transfer heat from one body to another.

Table 1

Aluminum and copper - which is better?

Aluminum has one disadvantage compared to copper: its thermal conductivity is 1.5 times less, namely 201–235 W/(m*K). However, compared to other metals, these are quite high values. Aluminum, like copper, has high anti-corrosion properties. In addition, it has advantages such as:

• low density (specific gravity 3 times less than that of copper);
• low cost (3.5 times less than copper).

Aluminum heating radiator
Thanks to simple calculations, it turns out that an aluminum part can be almost 10 times cheaper than a copper part, because it weighs much less and is made of cheaper material. This fact, along with high thermal conductivity, allows the use of aluminum as a material for cookware and food foil for ovens. The main disadvantage of aluminum is that it is softer, so it can only be used in alloys (for example, duralumin).

For effective heat transfer, the rate of heat transfer to the environment plays an important role, and this is actively facilitated by the cooling of radiators. As a result, the lower thermal conductivity of aluminum (relative to copper) is leveled out, and the weight and cost of the equipment are reduced. These important advantages allow aluminum to gradually replace copper from use in air conditioning systems.

Use of copper in electronics

In some industries, for example, in the radio industry and electronics, copper is essential. The fact is that this metal is very ductile in nature: it can be drawn into extremely thin wires (0.005 mm), and also can be used to create other specific conductive elements for electronic devices. And high thermal conductivity allows copper to extremely effectively remove the heat that inevitably arises during the operation of electrical appliances, which is very important for modern high-precision, but at the same time compact equipment.

The use of copper is relevant in cases where it is necessary to deposit a certain shape on a steel part. In this case, a copper template is used, which is not connected to the element being welded. Using aluminum for these purposes is impossible, as it will melt or burn through. It is also worth mentioning that copper can act as a cathode when welding with a carbon arc.

Properties of aluminum: density, thermal conductivity, heat capacity Al

The table shows the thermophysical properties of aluminum Al depending on temperature. The properties of aluminum are given over a wide temperature range - from minus 223 to 1527 ° C (from 50 to 1800 K).

As can be seen from the table, the thermal conductivity of aluminum at room temperature is about 236 W/(m deg) , which makes it possible to use this material for the manufacture of radiators and various heat sinks.

In addition to aluminum, copper also has high thermal conductivity.

Which metal has the greater thermal conductivity? It is known that the thermal conductivity of aluminum at medium and high temperatures is still less than that of copper, however, when cooled to 50K, the thermal conductivity of aluminum increases significantly and reaches a value of 1350 W/(m deg). For copper, at such a low temperature, the thermal conductivity value becomes lower than for aluminum and amounts to 1250 W/(m deg).

Aluminum begins to melt at a temperature of 933.61 K (about 660 ° C), while some of its properties undergo significant changes. The values ​​of properties such as thermal diffusivity, aluminum density and thermal conductivity are significantly reduced.

The density of aluminum is mainly determined by its temperature and depends on the state of aggregation of this metal.

For example, at a temperature of 27°C, the density of aluminum is 2697 kg/m3 , and when this metal is heated to the melting point (660°C), its density becomes equal to 2368 kg/m3.

The decrease in aluminum density with increasing temperature is due to its expansion when heated.

The table shows the following thermophysical properties of aluminum:

• aluminum density, g/cm3;
• specific (mass) heat capacity, J/(kg deg);
• thermal diffusivity coefficient, m2/s;
• thermal conductivity of aluminum, W/(m deg);
• electrical resistivity, Ohm m;
• Lorentz function.

Specific heat capacity of aluminum

The specific heat capacity of aluminum depends significantly on temperature and at room temperature is about 904 J/(kg deg) , which is significantly higher than the specific (mass) heat capacity of other common metals, such as copper and iron.

Below is a comparative table of the specific heat capacities of these metals. The heat capacity values ​​in the table are in the temperature range from -223 to 927°C.

According to the table, it can be seen that the value of the specific heat capacity of aluminum is significantly higher than the value of this property for copper and iron , therefore this property of aluminum, such as the ability to accumulate heat well, is widely used in industry and heating engineering, making this metal irreplaceable.

Comparative table of heat capacity of aluminum, copper and iron Heat capacity of metal, J/(kg deg)

Sources:

from here

Thermophysical properties of aluminum alloys AMts, AMg, D16, AK, etc.

The table presents the composition and thermophysical properties of aluminum alloys for cold-worked, hardened and annealed states of the alloy:

• density of alloys, kg/m3;
• thermal conductivity coefficient, W/(m deg);
• coefficient of linear thermal expansion, 1/deg;
• specific electrical resistance, Ohm m.

Thermophysical properties are presented for the following aluminum alloys: A, AMts, AMg, Amg1, AMg5, AB, D18, D1, D16, AK8, AK4, 32S, V95. The properties of the alloys are given at room temperature, with the exception of the coefficient of thermal expansion (CTE), which is indicated for the temperature ranges of 20-100, 20-200 and 20-300°C.

Thermal conductivity of aluminum alloys

A summary table of the thermal conductivity of aluminum alloys is presented. It shows the thermal conductivity values ​​of common aluminum alloys (aluminum alloys with silicon, copper, magnesium and zinc, casting alloys, duralumin) at various temperatures in the range from 4 to 700K.

According to the table, it can be seen that the thermal conductivity of aluminum alloys mainly increases with increasing temperature. An alloy such as AD1 has the greatest thermal conductivity at room temperature - its thermal conductivity at this temperature is 210 W/(m deg). Lower thermal conductivity is characteristic mainly of cast aluminum alloys, for example AK4, AL1, AL8 and others.

The temperature in the table is in degrees Kelvin!

Table of thermal conductivity of aluminum alloysAluminum alloyTemperature, KThermal conductivity of aluminum alloy, W/(m deg)

Properties of aluminum alloys with silicon, copper, magnesium and zinc

The table presents the composition and the following thermophysical properties of aluminum alloys:

• density of alloys, kg/m3;
• thermal conductivity coefficient, W/(m °C);
• coefficient of linear thermal expansion, 1/deg;
• corrosion resistance in water and air;
• temperature of strength change.

The density, thermal conductivity and coefficient of linear thermal expansion of the alloys are presented as a function of temperature in the range from 500 to 660°C. The density of aluminum alloys with silicon and zinc is the highest. Light alloys include alloys containing magnesium.

It should be noted that aluminum alloys with a high copper content have the greatest corrosion resistance in water and air - they are resistant to corrosion up to temperatures of 200...250°C. Such alloys also have high strength characteristics.

Thermal conductivity of aluminum alloys depending on temperature

The table shows the composition of aluminum alloys and their thermal conductivity coefficient in the temperature range from 173 (-100°C) to 773K (500°C). According to the table, it can be seen that the more aluminum contained in the alloy, the higher its thermal conductivity. When aluminum alloys are heated, their thermal conductivity usually increases.

Thermal conductivity of aluminum alloy with lithium

The values ​​of the thermal conductivity coefficient of an aluminum alloy with lithium at room temperature are given. Thermal conductivity is indicated depending on the lithium content of the alloy by weight (from 0 to 11%). It should be noted that an increase in the percentage of lithium leads to a decrease in the thermal conductivity of the alloy.

Density, thermal conductivity, heat capacity of aluminum alloys Amts, Amg1, Amg2, D1, D16

The values ​​of density (at a temperature of 293 K), thermal conductivity coefficient, W/(m °C), and specific (mass) heat capacity, kJ/(kg °C) of some aluminum alloys are presented depending on temperature (properties are given at temperatures of 25. 100, 200, 300, 400 °C).

The table shows the density, thermal conductivity, and heat capacity of the following aluminum alloys: Amts, Amg1, Amg2, D1, D16. It should be noted that the density of aluminum alloys is approximately the same, but aluminum alloy such as D-1 stands out a little - its density is 2800 kg/m3.

Thermal conductivity, heat capacity and resistivity of alloy 1151T

The table shows the values ​​of the thermal conductivity coefficient, W/(m deg), specific (mass) heat capacity, kJ/(g deg) and resistivity of aluminum alloy 1151T.

The properties of aluminum alloy 1151T are given depending on temperature (in the range from 0 to 400 ° C).

According to the table, it can be seen that the thermal conductivity of this alloy increases when heated, but around a temperature of 200°C there is a slight decrease followed by an increase.

The same nature of change is characteristic of the specific heat capacity of the 1151T alloy. The electrical resistivity of the alloy in question increases as its temperature increases.

Temperature coefficients of linear expansion (CTE) of alloy 1151T

The table shows the values ​​of the temperature coefficients of linear expansion (CTE) of aluminum alloy 1151T. Linear expansion coefficients of aluminum alloy 1151T are given depending on temperature (in the range from 0 to 500 °C). At high temperatures, the CTE of alloy 1151T increases.

Thermophysical properties of aluminum alloys of the Al-Cu-Mn system

The table shows the thermophysical properties of aluminum alloys containing copper and manganese. such alloys as alloy 01205, 1201, D21, D20 were considered. The properties of the alloys are presented depending on the temperature in the range from 25 to 400°C. Of the alloys considered, the most thermally conductive is the D20 alloy, with a thermal conductivity of 138 W/(m deg) at a temperature of 25°C.

The following thermophysical properties of the alloys are given:

• thermal conductivity coefficient, W/(m deg);
• specific (mass) heat capacity, kJ/(kg deg);
• coefficient of linear thermal expansion, 1/deg.

Thermophysical properties of aluminum alloys of the Al-Mg-Si system

The table presents the following thermophysical properties of aluminum alloys with magnesium and silicon:

• density, kg/m3;
• thermal conductivity coefficient, W/(m °C);
• specific heat capacity, kJ/(kg °C).

Properties are presented depending on temperature in the range from 25 to 400°C. The properties of the following alloys are given: AD31, AD33, AD35, AB. It should be noted that the specific heat capacity of alloys increases when heated.

Specific heat capacity of high-strength aluminum alloys V93, alloy 1933, V95, alloy 1973, V96, etc.

The mass heat capacity kJ/(kg °C) at temperatures from 20 to 400°C of the following alloys is indicated: V93, V93pch, alloy 1933, V95, V95pch, V95och, alloy 1973, V96Ts, V96Ts-3. As the temperature of the alloy increases, its heat capacity increases.

Thermal conductivity of high-strength aluminum alloys V93, alloy 1933, V95, alloy 1973, V96, etc.

The table shows the thermal conductivity values ​​in the dimension W/(m deg) depending on the temperature (range from 25 to 400°C) of the following aluminum alloys: V93, V93pch, alloy 1933, V95, V95pch, V95och, alloy 1973, V96Ts, V96Ts -3. The most thermally conductive, according to the table, are alloys V93, V93pch, alloy 1933, having a thermal conductivity value of 163 W/(m deg) at a temperature of 25°C.

Sources:1. Physical quantities. Directory. A.P. Babichev, N.A. Babushkina, A.M. Bratkovsky and others; Ed. I.S. Grigorieva, E.Z. Meilikhova. - M.: Energoatomizdat, 1991. - 1232 p.

2. Chirkin V.S. Thermophysical properties of nuclear technology materials.

3. V.M. Beletsky, G.A. Krivov. Aluminum alloys (composition, properties, technology, application). Directory. Under the general editorship. Academician of the Russian Academy of Sciences I.N. Fridlyandera - K.: "Comintekh", 2005. - 365 p.

4. Bogdanov S.N., Burtsev S.I., Ivanov O.P., Kupriyanova A.V. Refrigeration equipment. Air conditioning. Properties of substances: Reference / Ed. S.N. Bogdanov. 4th ed., revised. and additional - St. Petersburg: SPbGAKhPT, 1999. - 320 p.

Which conducts heat better: aluminum or copper?

Today, radiators are made from a variety of materials, the most common being steel, stainless steel and aluminum.

Always have doubts about which radiator to choose for installation in your home? Obviously, this depends on personal taste, as well as on the requirements that you have set for yourself regarding the quality of the heating of the room.

Aluminum is by far the most environmentally friendly material and has a huge number of advantages.

How to choose a heating radiator: expert advice

In this article we will not consider cast iron radiators, because... they are losing popularity among buyers.

Let's focus on the most popular models.

The material will tell you in detail about the advantages of aluminum and steel batteries.

Aluminum radiators are lightweight

Aluminum radiators are lighter than traditional steel or cast iron radiators, this fact makes it possible to place such a radiator on any wall in the room.

Aluminum batteries can be hung on the wall, even in situations where the thickness does not allow for deep fastening.

This significantly saves the cost of paying for construction work, since they can be hung very quickly and reliably.

We recommend that you familiarize yourself with the range of heating radiators presented in online stores; on the manufacturers' websites you can buy aluminum radiators from leading European manufacturers (ESPERADO, FERROLI, GLOBAL, FARAL, FONDITAL) with a 10-year guarantee!

Aluminum is a corrosion resistant material

Aluminum is not subject to corrosion, which makes it an ideal material for the production of radiators that are intended to be installed in areas such as bathrooms and kitchens where there is high humidity.

Aluminum conducts heat well

Aluminum heats up quickly, making it an excellent heat conductor.

Aluminum radiators have a low water content, which means that once turned on, such devices give an intense burst of heat and heat up rooms quite quickly.

By installing aluminum radiators, you can quickly achieve the required temperature in the rooms, as they have the shortest response time.

The main advantage is a significant saving in energy costs during the heating season and, as a wonderful bonus, saving money, since aluminum radiators can be turned off while you are away from the house, and when you return home, turn them on and quickly get a warm home without spending a long time waiting.

Aluminum radiators come in a wide range of designs and colors

There is a common belief that efficient heat cannot be beautiful and original. Fortunately, the days when design must give way to superior performance are over.

Aluminum radiators have a diverse range of designs and offer even the most demanding buyer a decent choice.

You can choose your own finishing color that will perfectly match the style of your home, the shape of the radiator will be one hundred percent in harmony with your home or office atmosphere.

Style sacrifice? Absolutely not when you choose aluminum radiators for your home!

Stainless steel

The use of steel for the production of heat exchangers allows us to obtain durable products, which are mainly used for individual heating systems in houses and cottages.

Due to the ability to control the quality of the coolant and the pressure in the system, steel appliances will be an excellent choice for autonomous heating systems.

Provided that high-quality coolant is supplied and the working fluid pressure is moderate, such devices will last more than 30 years.

Steel radiators have low thermal inertia, which means there will be no problems with rapid changes in room temperature. In addition to low thermal inertia, steel radiators have other advantages:

Effect of carbon concentration

The carbon concentration in steel affects the amount of heat transfer:

1. Low carbon steels have a high conductivity index. That is why they are used in the manufacture of pipes, which are then used to create the heating system pipeline. The coefficient value varies from 54 to 47 W/(m* K).
2. The average coefficient for common carbon steels is a value from 50 to 90 W/(m* K). That is why such material is used in the manufacture of parts for various mechanisms.
3. For metals that do not contain various impurities, the coefficient is 64 W/(m* K). This value does not change significantly under thermal influence.

Thus, the considered indicator for alloyed alloys may vary depending on the operating temperature.

Importance in everyday life and production

Why is it important to consider thermal conductivity? A similar value is indicated in various tables for each metal and is taken into account in the following cases:

1. In the manufacture of various heat exchangers. Heat is one of the important carriers of energy. It is used to provide comfortable living conditions in residential and other premises. When creating heating radiators and boilers, it is important to ensure rapid and complete heat transfer from the coolant to the end consumer.
2. In the manufacture of outlet elements. You can often encounter a situation where you need to remove heat rather than supply it. An example is the case of heat removal from the cutting edge of a tool or gear teeth. To ensure that the metal does not lose its basic performance qualities, rapid removal of thermal energy is ensured.
3. When creating insulating layers. In some cases, the material should not conduct thermal energy transfer. For such operating conditions, a metal is selected that has a low heat conductivity coefficient.

The indicator under consideration is determined when testing under various conditions. As previously noted, the thermal conductivity coefficient may depend on the operating temperature. Therefore, the tables indicate several of its values.

What does thermal conductivity depend on?

Studying the ability of heat transfer by metal products, it was revealed that thermal conductivity depends on:

• type of metal;
• chemical composition;
• porosity;
• sizes.

Metals have different crystal lattice structures, and this can change the thermal conductivity of the material. For example, in steel and aluminum, the structural features of microparticles affect differently the rate of transfer of thermal energy through them.

The thermal conductivity coefficient can have different values ​​for the same metal when the exposure temperature changes. This is due to the fact that different metals have different melting degrees, which means that under other environmental parameters, the properties of the materials will also differ, and this will affect thermal conductivity.

Application

The state of aggregation of materials has a distinctive structure of molecules and atoms. This is what has a great influence on metal products and their properties, depending on their purpose.

The different chemical composition of components and parts made of iron allows them to have different thermal conductivities. This is due to the structure of metals such as cast iron, steel, copper and aluminum. The porosity of cast iron products promotes slow heating, and the density of the copper structure, on the contrary, accelerates the heat transfer process. These properties are used for rapid heat removal or gradual heating of inert products. An example of using the properties of metal products is:

• kitchen utensils with various properties;
• pipe soldering equipment;
• irons;
• rolling and sliding bearings;
• plumbing equipment for heating water;
• heating devices.

Copper tubes are widely used in radiators of automobile cooling systems and air conditioners used in everyday life. Cast iron radiators retain heat in the apartment, even with an inconsistent supply of coolant at the required temperature. And radiators made of aluminum contribute to the rapid transfer of heat to the heated room.

When high temperatures occur as a result of friction of metal surfaces, it is also important to take into account the thermal conductivity of the product. In any gearbox or other mechanical equipment, the ability to remove heat will allow the mechanism parts to maintain strength and not be subject to destruction during operation. Knowledge of the heat transfer properties of various materials will allow you to competently use certain alloys of non-ferrous or ferrous metals.

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