Thermal storage capacity of materials. Indicators of specific heat capacity of various types of bricks Use of various materials in construction

When selecting a suitable material for a particular type of construction work, special attention should be paid to its technical characteristics. This also applies to the specific heat capacity of brick, on which the house’s need for subsequent thermal insulation and additional wall decoration largely depends.

Characteristics of brick that affect its use:

• Specific heat. A value that determines the amount of thermal energy required to heat 1 kg by 1 degree.
• Thermal conductivity. A very important characteristic for brick products, which allows you to determine the amount of heat transferred from the room to the street.
• The level of heat transfer of a brick wall is directly affected by the characteristics of the material used for its construction. In cases where we are talking about multi-layer masonry, it will be necessary to take into account the thermal conductivity of each layer separately.

Ceramic

Based on production technology, brick is classified into ceramic and silicate groups. Moreover, both types have significant differences in material density, specific heat capacity and thermal conductivity coefficient. The raw material for making ceramic bricks, also called red bricks, is clay, to which a number of components are added. The formed raw blanks are fired in special ovens. The specific heat capacity can vary between 0.7-0.9 kJ/(kg K). As for the average density, it is usually at the level of 1400 kg/m3.

Among the strengths of ceramic bricks are:

1. Smoothness of the surface. This increases its external aesthetics and ease of installation.
2. Resistance to frost and moisture. Under normal conditions, walls do not require additional moisture and thermal insulation.
3. Ability to withstand high temperatures. This allows the use of ceramic bricks for the construction of stoves, barbecues, and heat-resistant partitions.
4. Density 700-2100 kg/m3. This characteristic is directly affected by the presence of internal pores. As the porosity of a material increases, its density decreases and its thermal insulation characteristics increase.

Silicate

As for sand-lime brick, it can be solid, hollow and porous. Based on the size, there are single, one-and-a-half and double bricks. On average, sand-lime brick has a density of 1600 kg/m3. The noise-absorbing characteristics of silicate masonry are especially appreciated: even if we are talking about a wall of small thickness, its level of sound insulation will be an order of magnitude higher than in the case of other types of masonry material.

Facing

Separately, it is worth mentioning the facing brick, which with equal success resists both water and increased temperature. The specific heat capacity of this material is at the level of 0.88 kJ/(kg K), with a density of up to 2700 kg/m3. Facing bricks are available for sale in a wide variety of shades. They are suitable for both cladding and laying.

Refractory

Represented by dinas, carborundum, magnesite and fireclay bricks. The mass of one brick is quite large due to its significant density (2700 kg/m3). The lowest heat capacity when heated is carborundum brick 0.779 kJ/(kg K) for a temperature of +1000 degrees. The heating rate of a furnace laid from this brick significantly exceeds the heating of fireclay masonry, but cooling occurs faster.

Furnaces are built from refractory bricks, providing heating up to +1500 degrees. The specific heat capacity of a given material is greatly influenced by the heating temperature. For example, the same fireclay brick at +100 degrees has a heat capacity of 0.83 kJ/(kg K). However, if it is heated to +1500 degrees, this will provoke an increase in heat capacity to 1.25 kJ/(kg K).

Dependence on temperature of use

The technical performance of bricks is greatly influenced by temperature conditions:

• Trepelny. At temperatures from -20 to + 20, the density varies within 700-1300 kg/m3. The heat capacity indicator is at a stable level of 0.712 kJ/(kg K).
• Silicate. A similar temperature regime of -20 - +20 degrees and a density from 1000 to 2200 kg/m3 provides the possibility of different specific heat capacities of 0.754-0.837 kJ/(kg K).
• Adobe. When the temperature is identical to the previous type, it demonstrates a stable heat capacity of 0.753 kJ/(kg K).
• Red. Can be used at temperatures of 0-100 degrees. Its density can vary from 1600-2070 kg/m3, and its heat capacity can range from 0.849 to 0.872 kJ/(kg K).


• Yellow. Temperature fluctuations from -20 to +20 degrees and a stable density of 1817 kg/m3 gives the same stable heat capacity of 0.728 kJ/(kg K).
• Building. At a temperature of +20 degrees and a density of 800-1500 kg/m3, the heat capacity is at the level of 0.8 kJ/(kg K).
• Facing. The same temperature regime of +20, with a material density of 1800 kg/m3, determines the heat capacity of 0.88 kJ/(kg K).
• Dinas. Operation at elevated temperatures from +20 to +1500 and density 1500-1900 kg/m3 implies a consistent increase in heat capacity from 0.842 to 1.243 kJ/(kg K).
• Carborundum. As it heats from +20 to +100 degrees, a material with a density of 1000-1300 kg/m3 gradually increases its heat capacity from 0.7 to 0.841 kJ/(kg K). However, if the heating of the carborundum brick is continued further, its heat capacity begins to decrease. At a temperature of +1000 degrees it will be equal to 0.779 kJ/(kg K).
• Magnesite. A material with a density of 2700 kg/m3 with an increase in temperature from +100 to +1500 degrees gradually increases its heat capacity of 0.93-1.239 kJ/(kg K).
• Chromite. Heating a product with a density of 3050 kg/m3 from +100 to +1000 degrees provokes a gradual increase in its heat capacity from 0.712 to 0.912 kJ/(kg K).
• Chamotte. It has a density of 1850 kg/m3. When heated from +100 to +1500 degrees, the heat capacity of the material increases from 0.833 to 1.251 kJ/(kg K).

Select the bricks correctly, depending on the tasks at the construction site.

kvartirnyj-remont.com

Types of bricks

In order to answer the question: “how to build a warm house from brick?”, you need to find out what type of brick is best to use. Since the modern market offers a huge selection of this building material. Let's look at the most common types.

Silicate

Sand-lime bricks are the most popular and widely used in construction in Russia. This type is made by mixing lime and sand. This material has become very widespread due to its wide range of applications in everyday life, and also due to the fact that its price is quite low.

However, if we turn to the physical quantities of this product, then not everything is so smooth.

Consider the double sand-lime brick M 150. The M 150 brand indicates high strength, so it even comes close to natural stone. Dimensions are 250x120x138 mm.

The thermal conductivity of this type is on average 0.7 W/(m o C). This is a fairly low figure compared to other materials. Therefore, warm walls made of this type of brick most likely will not work.

An important advantage of such bricks compared to ceramic ones is their soundproofing properties, which have a very beneficial effect on the construction of walls enclosing apartments or dividing rooms.

Ceramic

The second place in popularity of building bricks is rightfully given to ceramic ones. To produce them, various mixtures of clays are fired.

This type is divided into two types:

1. Building,
2. Facing.

Construction bricks are used for the construction of foundations, walls of houses, stoves, etc., and facing bricks are used for finishing buildings and premises. This material is more suitable for DIY construction, as it is much lighter than silicate.

The thermal conductivity of a ceramic block is determined by the thermal conductivity coefficient and is numerically equal to:

• Full-bodied – 0.6 W/m* o C;
• Hollow brick - 0.5 W/m* o C;
• Slot – 0.38 W/m* o C.

The average heat capacity of a brick is about 0.92 kJ.

Warm ceramics

Warm brick is a relatively new building material. In principle, it is an improvement on the conventional ceramic block.

This type of product is much larger than usual; its dimensions can be 14 times larger than standard ones. But this does not greatly affect the overall weight of the structure.

Thermal insulation properties are almost 2 times better compared to ceramic bricks. The thermal conductivity coefficient is approximately 0.15 W/m* o C.

A block of warm ceramics has many small voids in the form of vertical channels. And as mentioned above, the more air in the material, the higher the thermal insulation properties of this building material. Heat loss can occur mainly on internal partitions or in masonry joints.

Summary

We hope our article will help you understand the large number of physical parameters of bricks and choose the most suitable option for yourself in all respects! And the video in this article will provide additional information on this topic, watch.

klademkirpich.ru

To heat any material with mass m from temperature t start to temperature t end, you will need to spend a certain amount of thermal energy Q, which will be proportional to the mass and temperature difference ΔT (t end -t start). Therefore, the heat capacity formula will look like this: Q = c*m*ΔТ, where c is the heat capacity coefficient (specific value). It can be calculated using the formula: c = Q/(m* ΔТ) (kcal/(kg* °C)).

Table 1

Brick has a high heat capacity, so it is ideal for building houses and constructing stoves.

What should the walls of a private house be like in order to comply with building codes? The answer to this question has several nuances. To understand them, an example will be given of the heat capacity of the 2 most popular building materials: concrete and wood. The heat capacity of concrete is 0.84 kJ/(kg*°C), and that of wood is 2.3 kJ/(kg*°C).

At first glance, you might think that wood is a more heat-intensive material than concrete. This is true, because wood contains almost 3 times more thermal energy than concrete. To heat 1 kg of wood you need to spend 2.3 kJ of thermal energy, but when cooling it will also release 2.3 kJ into space. At the same time, 1 kg of concrete structure can accumulate and, accordingly, release only 0.84 kJ.

Tree

Brick

You may be interested in: drilling a water well in Kaluga: the cost is reasonable

opt-stroy.net

Definition and formula of heat capacity

Each substance, to one degree or another, is capable of absorbing, storing and retaining thermal energy. To describe this process, the concept of heat capacity was introduced, which is the property of a material to absorb thermal energy when heating the surrounding air.

To heat any material with mass m from temperature t start to temperature t end, you will need to spend a certain amount of thermal energy Q, which will be proportional to the mass and temperature difference ΔT (t end -t start). Therefore, the heat capacity formula will look like this: Q = c*m*ΔT, where c is the heat capacity coefficient (specific value). It can be calculated using the formula: c = Q/(m* ΔТ) (kcal/(kg* °C)).

Conventionally assuming that the mass of the substance is 1 kg, and ΔТ = 1°C, we can obtain that c = Q (kcal). This means that the specific heat capacity is equal to the amount of thermal energy that is expended to heat a material weighing 1 kg by 1°C.

Using heat capacity in practice

Building materials with high heat capacity are used for the construction of heat-resistant structures. This is very important for private houses in which people live permanently. The fact is that such structures allow you to store (accumulate) heat, thanks to which the house maintains a comfortable temperature for quite a long time. First, the heating device heats the air and the walls, after which the walls themselves warm the air. This allows you to save money on heating and make your stay more comfortable. For a house in which people live periodically (for example, on weekends), the high thermal capacity of the building material will have the opposite effect: such a building will be quite difficult to heat quickly.

The heat capacity values ​​of building materials are given in SNiP II-3-79. Below is a table of the main building materials and their specific heat capacity values.

Table 1

Speaking about heat capacity, it should be noted that heating stoves are recommended to be built from brick, since the value of its heat capacity is quite high. This allows you to use the stove as a kind of heat accumulator. Heat accumulators in heating systems (especially in water heating systems) are used more and more every year. Such devices are convenient because they only need to be heated well once with the intense fire of a solid fuel boiler, after which they will heat your home for a whole day or even more. This will significantly save your budget.

Heat capacity of building materials

What should the walls of a private house be like in order to comply with building codes? The answer to this question has several nuances. To understand them, an example will be given of the heat capacity of the 2 most popular building materials: concrete and wood. The heat capacity of concrete is 0.84 kJ/(kg*°C), and that of wood is 2.3 kJ/(kg*°C).

At first glance, you might think that wood is a more heat-intensive material than concrete. This is true, because wood contains almost 3 times more thermal energy than concrete. To heat 1 kg of wood you need to spend 2.3 kJ of thermal energy, but when cooling it will also release 2.3 kJ into space. At the same time, 1 kg of concrete structure can accumulate and, accordingly, release only 0.84 kJ.

But don't rush to conclusions. For example, you need to find out what heat capacity 1 m 2 of concrete and wooden walls 30 cm thick will have. To do this, you first need to calculate the weight of such structures. 1 m2 of this concrete wall will weigh: 2300 kg/m3 * 0.3 m3 = 690 kg. 1 m 2 of wooden wall will weigh: 500 kg/m 3 * 0.3 m 3 = 150 kg.

• for a concrete wall: 0.84*690*22 = 12751 kJ;
• for a wooden structure: 2.3*150*22 = 7590 kJ.

From the obtained result we can conclude that 1 m 3 of wood will accumulate heat almost 2 times less than concrete. An intermediate material in terms of heat capacity between concrete and wood is brickwork, a unit volume of which under the same conditions will contain 9199 kJ of thermal energy. At the same time, aerated concrete, as a building material, will contain only 3326 kJ, which will be significantly less than wood. However, in practice, the thickness of a wooden structure can be 15-20 cm, when aerated concrete can be laid in several rows, significantly increasing the specific heat capacity of the wall.

Use of various materials in construction

Tree

For comfortable living in a home, it is very important that the material has high heat capacity and low thermal conductivity.

In this regard, wood is the best option for houses not only for permanent but also for temporary residence. A wooden building that is not heated for a long time will respond well to changes in air temperature. Therefore, heating of such a building will occur quickly and efficiently.

Coniferous species are mainly used in construction: pine, spruce, cedar, fir. In terms of price-quality ratio, the best option is pine. Whatever you choose to design a wooden house, you need to consider the following rule: the thicker the walls, the better. However, here you also need to take into account your financial capabilities, since with an increase in the thickness of the timber, its cost will increase significantly.

Brick

This building material has always been a symbol of stability and strength. The brick has good strength and resistance to negative environmental influences. However, if we take into account the fact that brick walls are mainly constructed with a thickness of 51 and 64 cm, then in order to create good thermal insulation they additionally need to be covered with a layer of thermal insulation material. Brick houses are great for permanent residence. Once heated, such structures are capable of releasing the heat accumulated in them into space for a long time.

When choosing a material for building a house, you should take into account not only its thermal conductivity and heat capacity, but also how often people will live in such a house. The right choice will allow you to maintain coziness and comfort in your home throughout the year.

ostroymaterialah.ru

Heat capacity of brick

Physical quantities are of high importance when choosing materials for building construction.

Let's consider the main indicators used in construction, for example, to understand what the specific heat capacity of a brick is, it is necessary to find out what this physical quantity is.

• Heat capacity. Essentially, specific heat capacity is determined by the amount of heat required to heat one kilogram of a substance by one degree Celsius (one Kelvin).
• Thermal conductivity.An equally important physical indicator of a brick structure is the ability to transfer heat at different temperatures outside and inside the building, called the thermal conductivity coefficient. This parameter expresses how much heat is lost per 1 meter of wall thickness when the temperature differs by 1 degree between the external and internal areas.
• Heat transfer. The heat transfer coefficient of a brick wall will largely depend on what type of brickwork material you choose. To determine this coefficient for a multilayer wall, you need to know this parameter for each layer separately. Then all values ​​are added up, since the total coefficient of thermal resistance is the sum of the resistances of all layers included in the wall.

Note!
Solid bricks have a fairly high thermal conductivity coefficient and therefore it is much more economical to use the hollow type.
This is due to the fact that the air in the voids has lower thermal conductivity, which means the walls of the structure will be much thinner.

• Heat transfer resistance. The heat transfer resistance of a brick wall is defined as the ratio of the temperature difference at the edges of the building structure to the amount of heat passing through it. This parameter is used to reflect the properties of materials and is expressed as the ratio of the density of the material to its thermal conductivity.
• Thermal homogeneity. The coefficient of thermal uniformity of a brick wall is a parameter equal to the inverse ratio of the heat flow through the wall to the amount of heat passing through a conditional enclosing structure equal in area to the wall.

Note!
The instructions on how to calculate this parameter are quite complex, so it is better to do this by companies that have experience and appropriate instruments for determining certain indicators.

In essence, the coefficient of thermal uniformity for brickwork expresses how many and what intensity “cold bridges” are in a given enclosing structure. In most cases, this value ranges from 0.6-0.99, and a completely homogeneous wall that does not have heat-conducting flaws is taken as a unit.

Types of bricks

In order to answer the question: “how to build a warm house from brick?”, you need to find out what type of brick is best to use. Since the modern market offers a huge selection of this building material. Let's look at the most common types.

Silicate

Sand-lime bricks are the most popular and widely used in construction in Russia. This type is made by mixing lime and sand. This material has become very widespread due to its wide range of applications in everyday life, and also due to the fact that its price is quite low.

However, if we turn to the physical quantities of this product, then not everything is so smooth.

Consider the double sand-lime brick M 150. The M 150 brand indicates high strength, so it even comes close to natural stone. Dimensions are 250x120x138 mm.

The thermal conductivity of this type is on average 0.7 W/(m o C). This is a fairly low figure compared to other materials. Therefore, warm walls made of this type of brick most likely will not work.

An important advantage of such bricks compared to ceramic ones is their soundproofing properties, which have a very beneficial effect on the construction of walls enclosing apartments or dividing rooms.

Ceramic

The second place in popularity of building bricks is rightfully given to ceramic ones. To produce them, various mixtures of clays are fired.

This type is divided into two types:

1. Building,
2. Facing.

Construction bricks are used for the construction of foundations, walls of houses, stoves, etc., and facing bricks are used for finishing buildings and premises. This material is more suitable for DIY construction, as it is much lighter than silicate.

The thermal conductivity of a ceramic block is determined by the thermal conductivity coefficient and is numerically equal to:

• Full-bodied – 0.6 W/m* o C;
• Hollow brick - 0.5 W/m* o C;
• Slot – 0.38 W/m* o C.

The average heat capacity of a brick is about 0.92 kJ.

Warm ceramics

Warm brick is a relatively new building material. In principle, it is an improvement on the conventional ceramic block.

This type of product is much larger than usual; its dimensions can be 14 times larger than standard ones. But this does not greatly affect the overall weight of the structure.

Thermal insulation properties are almost 2 times better compared to ceramic bricks. The thermal conductivity coefficient is approximately 0.15 W/m* o C.

A block of warm ceramics has many small voids in the form of vertical channels. And as mentioned above, the more air in the material, the higher the thermal insulation properties of this building material. Heat loss can occur mainly on internal partitions or in masonry joints.

Summary

We hope our article will help you understand the large number of physical parameters of bricks and choose the most suitable option for yourself in all respects! And the video in this article will provide additional information on this topic, watch.

klademkirpich.ru

Ceramic

Based on production technology, brick is classified into ceramic and silicate groups. Moreover, both types have significant differences in material density, specific heat capacity and thermal conductivity coefficient. The raw material for making ceramic bricks, also called red bricks, is clay, to which a number of components are added. The formed raw blanks are fired in special ovens. The specific heat capacity can vary between 0.7-0.9 kJ/(kg K). As for the average density, it is usually at the level of 1400 kg/m3.

Among the strengths of ceramic bricks are:

1. Smoothness of the surface. This increases its external aesthetics and ease of installation.
2. Resistance to frost and moisture. Under normal conditions, walls do not require additional moisture and thermal insulation.
3. Ability to withstand high temperatures. This allows the use of ceramic bricks for the construction of stoves, barbecues, and heat-resistant partitions.
4. Density 700-2100 kg/m3. This characteristic is directly affected by the presence of internal pores. As the porosity of a material increases, its density decreases and its thermal insulation characteristics increase.

Silicate

As for sand-lime brick, it can be solid, hollow and porous. Based on the size, there are single, one-and-a-half and double bricks. On average, sand-lime brick has a density of 1600 kg/m3. The noise-absorbing characteristics of silicate masonry are especially appreciated: even if we are talking about a wall of small thickness, its level of sound insulation will be an order of magnitude higher than in the case of other types of masonry material.

Facing

Separately, it is worth mentioning the facing brick, which with equal success resists both water and increased temperature. The specific heat capacity of this material is at the level of 0.88 kJ/(kg K), with a density of up to 2700 kg/m3. Facing bricks are available for sale in a wide variety of shades. They are suitable for both cladding and laying.

Refractory

Represented by dinas, carborundum, magnesite and fireclay bricks. The mass of one brick is quite large due to its significant density (2700 kg/m3). The lowest heat capacity when heated is carborundum brick 0.779 kJ/(kg K) for a temperature of +1000 degrees. The heating rate of a furnace laid from this brick significantly exceeds the heating of fireclay masonry, but cooling occurs faster.

Furnaces are built from refractory bricks, providing heating up to +1500 degrees. The specific heat capacity of a given material is greatly influenced by the heating temperature. For example, the same fireclay brick at +100 degrees has a heat capacity of 0.83 kJ/(kg K). However, if it is heated to +1500 degrees, this will provoke an increase in heat capacity to 1.25 kJ/(kg K).

Dependence on temperature of use

The technical performance of bricks is greatly influenced by temperature conditions:

• Trepelny. At temperatures from -20 to + 20, the density varies within 700-1300 kg/m3. The heat capacity indicator is at a stable level of 0.712 kJ/(kg K).
• Silicate. A similar temperature regime of -20 - +20 degrees and a density from 1000 to 2200 kg/m3 provides the possibility of different specific heat capacities of 0.754-0.837 kJ/(kg K).
• Adobe. When the temperature is identical to the previous type, it demonstrates a stable heat capacity of 0.753 kJ/(kg K).
• Red. Can be used at temperatures of 0-100 degrees. Its density can vary from 1600-2070 kg/m3, and its heat capacity can range from 0.849 to 0.872 kJ/(kg K).
• Yellow. Temperature fluctuations from -20 to +20 degrees and a stable density of 1817 kg/m3 gives the same stable heat capacity of 0.728 kJ/(kg K).
• Building. At a temperature of +20 degrees and a density of 800-1500 kg/m3, the heat capacity is at the level of 0.8 kJ/(kg K).
• Facing. The same temperature regime of +20, with a material density of 1800 kg/m3, determines the heat capacity of 0.88 kJ/(kg K).


• Dinas. Operation at elevated temperatures from +20 to +1500 and density 1500-1900 kg/m3 implies a consistent increase in heat capacity from 0.842 to 1.243 kJ/(kg K).
• Carborundum. As it heats from +20 to +100 degrees, a material with a density of 1000-1300 kg/m3 gradually increases its heat capacity from 0.7 to 0.841 kJ/(kg K). However, if the heating of the carborundum brick is continued further, its heat capacity begins to decrease. At a temperature of +1000 degrees it will be equal to 0.779 kJ/(kg K).
• Magnesite. A material with a density of 2700 kg/m3 with an increase in temperature from +100 to +1500 degrees gradually increases its heat capacity of 0.93-1.239 kJ/(kg K).
• Chromite. Heating a product with a density of 3050 kg/m3 from +100 to +1000 degrees provokes a gradual increase in its heat capacity from 0.712 to 0.912 kJ/(kg K).
• Chamotte. It has a density of 1850 kg/m3. When heated from +100 to +1500 degrees, the heat capacity of the material increases from 0.833 to 1.251 kJ/(kg K).

Select the bricks correctly, depending on the tasks at the construction site.

kvartirnyj-remont.com

What it is?

The physical characteristic of heat capacity is inherent in any substance. It denotes the amount of heat that a physical body absorbs when heated by 1 degree Celsius or Kelvin. It is a mistake to identify the general concept with the specific one, since the latter implies the temperature required to heat one kilogram of a substance. It seems possible to accurately determine its number only in laboratory conditions. The indicator is necessary to determine the thermal resistance of the walls of a building even in the case when construction work is carried out at sub-zero temperatures. For the construction of private and multi-storey residential buildings and premises, materials with high thermal conductivity are used, since they accumulate heat and maintain the temperature in the room.

The advantage of brick buildings is that they save on heating costs.

Return to contents

What does the heat capacity of bricks depend on?

The heat capacity coefficient is primarily affected by the temperature of the substance and its state of aggregation, since the heat capacity of the same substance in the liquid and solid states differs in favor of the liquid. In addition, the volume of the material and the density of its structure are important. The more voids there are in it, the less it is able to retain heat inside itself.

Return to contents

Types of bricks and their indicators

More than 10 varieties are produced, differing in manufacturing technology. But silicate, ceramic, facing, fireproof and warm are more often used. Standard ceramic bricks are made from red clay with impurities and fired. Its heat index is 700-900 J/ (kg deg). It is considered quite resistant to high and low temperatures. Sometimes used for laying out stove heating. Its porosity and density vary and affect the heat capacity coefficient. Sand-lime brick consists of a mixture of sand, clay and additives. It can be full or hollow, of different sizes and, therefore, its specific heat capacity is equal to values ​​​​from 754 to 837 J / (kg deg). The advantage of silicate brickwork is good sound insulation even when laying the wall in one layer.

The facing brick used for building facades has a fairly high density and heat capacity within 880 J/ (kg deg). Refractory brick is ideal for laying a stove because it can withstand temperatures up to 1500 degrees Celsius. This subspecies includes fireclay, carborundum, magnesite and others. And the heat capacity coefficient (J/kg) is different:

• carborundum - 700-850;
• fireclay - 1000-1300.

Warm brick is a new product on the construction market, which is a modernized ceramic block, its dimensions and thermal insulation characteristics are much higher than the standard one. A structure with a large number of voids helps to accumulate heat and warm the room. Heat loss is possible only in masonry joints or partitions.

etokirpichi.ru

Definition and formula of heat capacity

Each substance, to one degree or another, is capable of absorbing, storing and retaining thermal energy. To describe this process, the concept of heat capacity was introduced, which is the property of a material to absorb thermal energy when heating the surrounding air.

To heat any material with mass m from temperature t start to temperature t end, you will need to spend a certain amount of thermal energy Q, which will be proportional to the mass and temperature difference ΔT (t end -t start). Therefore, the heat capacity formula will look like this: Q = c*m*ΔT, where c is the heat capacity coefficient (specific value). It can be calculated using the formula: c = Q/(m* ΔТ) (kcal/(kg* °C)).

Conventionally assuming that the mass of the substance is 1 kg, and ΔТ = 1°C, we can obtain that c = Q (kcal). This means that the specific heat capacity is equal to the amount of thermal energy that is expended to heat a material weighing 1 kg by 1°C.

Using heat capacity in practice

Building materials with high heat capacity are used for the construction of heat-resistant structures. This is very important for private houses in which people live permanently. The fact is that such structures allow you to store (accumulate) heat, thanks to which the house maintains a comfortable temperature for quite a long time. First, the heating device heats the air and the walls, after which the walls themselves warm the air. This allows you to save money on heating and make your stay more comfortable. For a house in which people live periodically (for example, on weekends), the high thermal capacity of the building material will have the opposite effect: such a building will be quite difficult to heat quickly.

The heat capacity values ​​of building materials are given in SNiP II-3-79. Below is a table of the main building materials and their specific heat capacity values.

Table 1

Speaking about heat capacity, it should be noted that heating stoves are recommended to be built from brick, since the value of its heat capacity is quite high. This allows you to use the stove as a kind of heat accumulator. Heat accumulators in heating systems (especially in water heating systems) are used more and more every year. Such devices are convenient because they only need to be heated well once with the intense fire of a solid fuel boiler, after which they will heat your home for a whole day or even more. This will significantly save your budget.

What should the walls of a private house be like in order to comply with building codes? The answer to this question has several nuances. To understand them, an example will be given of the heat capacity of the 2 most popular building materials: concrete and wood. The heat capacity of concrete is 0.84 kJ/(kg*°C), and that of wood is 2.3 kJ/(kg*°C).

At first glance, you might think that wood is a more heat-intensive material than concrete. This is true, because wood contains almost 3 times more thermal energy than concrete. To heat 1 kg of wood you need to spend 2.3 kJ of thermal energy, but when cooling it will also release 2.3 kJ into space. At the same time, 1 kg of concrete structure can accumulate and, accordingly, release only 0.84 kJ.

But don't rush to conclusions. For example, you need to find out what heat capacity 1 m 2 of concrete and wooden walls 30 cm thick will have. To do this, you first need to calculate the weight of such structures. 1 m2 of this concrete wall will weigh: 2300 kg/m3 * 0.3 m3 = 690 kg. 1 m 2 of wooden wall will weigh: 500 kg/m 3 * 0.3 m 3 = 150 kg.

• for a concrete wall: 0.84*690*22 = 12751 kJ;
• for a wooden structure: 2.3*150*22 = 7590 kJ.

From the obtained result we can conclude that 1 m 3 of wood will accumulate heat almost 2 times less than concrete. An intermediate material in terms of heat capacity between concrete and wood is brickwork, a unit volume of which under the same conditions will contain 9199 kJ of thermal energy. At the same time, aerated concrete, as a building material, will contain only 3326 kJ, which will be significantly less than wood. However, in practice, the thickness of a wooden structure can be 15-20 cm, when aerated concrete can be laid in several rows, significantly increasing the specific heat capacity of the wall.

Use of various materials in construction

Tree

For comfortable living in a home, it is very important that the material has high heat capacity and low thermal conductivity.

In this regard, wood is the best option for houses not only for permanent but also for temporary residence. A wooden building that is not heated for a long time will respond well to changes in air temperature. Therefore, heating of such a building will occur quickly and efficiently.

Coniferous species are mainly used in construction: pine, spruce, cedar, fir. In terms of price-quality ratio, the best option is pine. Whatever you choose to design a wooden house, you need to consider the following rule: the thicker the walls, the better. However, here you also need to take into account your financial capabilities, since with an increase in the thickness of the timber, its cost will increase significantly.

Brick

This building material has always been a symbol of stability and strength. The brick has good strength and resistance to negative environmental influences. However, if we take into account the fact that brick walls are mainly constructed with a thickness of 51 and 64 cm, then in order to create good thermal insulation they additionally need to be covered with a layer of thermal insulation material. Brick houses are great for permanent residence. Once heated, such structures are capable of releasing the heat accumulated in them into space for a long time.

When choosing a material for building a house, you should take into account not only its thermal conductivity and heat capacity, but also how often people will live in such a house. The right choice will allow you to maintain coziness and comfort in your home throughout the year.

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Brick products - characteristics

Clinker brick has the highest coefficient of thermal conductivity, due to which its use is very highly specialized - for masonry walls, using a material with such properties would be impractical and costly in terms of further insulation of the building - the declared thermal conductivity of this material (λ) is in the range of 04-09 W/( m K). Therefore, clinker bricks are most often used for road surfaces and laying durable floors in industrial buildings.

For silicate products, heat transfer is directly proportional to the mass of the product. That is, for a double silicate brick of grade M 150, the heat loss is λ = 0.7-0.8, and for a slotted silicate product, the heat transfer coefficient will be λ = 0.4, that is, twice as good. But it is recommended to additionally insulate walls made of sand-lime brick; moreover, the strength of this building material leaves much to be desired.

Ceramic bricks are produced in different forms and characteristics:

1. Solid products with thermal conductivity coefficient λ = 0.5-0.9;
2. Hollow products - λ is taken equal to 0.57;
3. Ordinary refractory material: the thermal conductivity coefficient of fireclay brick is λ = 06-08 W/(mK);
4. Slotted with coefficient λ = 0.4;
5. Ceramic brick with increased thermal insulation characteristics and λ = 0.11 is very fragile, which significantly narrows its range of application.

All types of ceramic bricks can be used to build the walls of a house, but each has its own thermal parameters, based on which the future external insulation of the walls is calculated.

The thermal conductivity of ceramic products is the lowest among the options listed above.

Porous brick as a material with thermal conductivity characteristics is the best, as is warm brick ceramics. The porous product is made in such a way that, in addition to the cracks in the body, the material has a special structure that reduces the brick’s own weight, which increases its heat resistance.

Any brick whose thermal conductivity can reach 0.8-0.9 tends to accumulate moisture in the body of the product, which is especially negative in cold weather - the transformation of water into ice can cause destruction of the brick structure, and constant condensation in the wall is the reason for the appearance mold, an obstacle to the passage of air through the walls and a decrease in the thermal conductivity of the walls in general.

To prevent or minimize the accumulation of moisture in the walls, brickwork is made with air gaps. How to properly ensure a constant air gap:

1. Starting from the first row of bricks, air gaps up to 10 mm thick are left between the products, which are not filled with mortar. The pitch of such gaps is 1 meter;
2. An air gap of 25-30 mm thick is left between the brick and the heat insulating material along the entire height of the wall - similar to a ventilated facade. Constant air flows will pass through these air channels, which will prevent the wall from losing its thermal insulation properties and will ensure a constant temperature in the house, provided the heating is running in winter.

A significant reduction in the thermal conductivity coefficient of brick masonry can be achieved without incurring large expenses, which is important for individual construction. The quality of housing will not suffer when implementing the above methods, and this is the most important thing.

If you use fire-resistant fireclay bricks in the construction of a house, you can significantly increase the fire safety of your home, again without significant costs, except for the price difference in the brands of bricks. The thermal conductivity coefficient of refractory bricks is slightly higher than that of clinker bricks, but safety is also of great importance when operating a house.

The level of sound insulation of walls made of ceramic bricks is ≈ 50 dB, which is close to the standard requirements of SNiP - 54 dB. This level of sound insulation can be provided by a brick wall laid out in two bricks - this is 50 cm thick. All other sizes require additional sound insulation, implemented in a variety of options. For example, reinforced concrete panel walls with a standard thickness of 140 mm have a sound insulation level of 50 dB. You can improve the sound insulation properties of a house by increasing the thickness of the brick walls, but this will be more expensive than laying an additional layer of sound insulation.

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Specific heat capacity of materials

Heat capacity is a physical quantity that describes the ability of a material to accumulate temperature from a heated environment. Quantitatively, specific heat capacity is equal to the amount of energy, measured in J, required to heat a body weighing 1 kg by 1 degree.
Below is a table of the specific heat capacity of the most common materials in construction.

• type and volume of heated material (V);
• the specific heat capacity of this material (Sud);
• specific gravity (msp);
• initial and final temperatures of the material.

Heat capacity of building materials

The heat capacity of materials, the table for which is given above, depends on the density and thermal conductivity of the material.

And the thermal conductivity coefficient, in turn, depends on the size and closure of the pores. A fine-porous material, which has a closed pore system, has greater thermal insulation and, accordingly, lower thermal conductivity than a large-porous one.

This is very easy to see using the most common materials in construction as an example. The figure below shows how the thermal conductivity coefficient and the thickness of the material influence the thermal insulation properties of external fences.

The figure shows that building materials with lower density have a lower thermal conductivity coefficient.
However, this is not always the case. For example, there are fibrous types of thermal insulation for which the opposite pattern applies: the lower the density of the material, the higher the thermal conductivity coefficient will be.

Therefore, you cannot rely solely on the indicator of the relative density of the material, but it is worth taking into account its other characteristics.

Comparative characteristics of the heat capacity of basic building materials

In order to compare the heat capacity of the most popular building materials, such as wood, brick and concrete, it is necessary to calculate the heat capacity for each of them.

First of all, you need to decide on the specific gravity of wood, brick and concrete. It is known that 1 m3 of wood weighs 500 kg, brick - 1700 kg, and concrete - 2300 kg. If we take a wall whose thickness is 35 cm, then through simple calculations we find that the specific gravity of 1 square meter of wood will be 175 kg, brick - 595 kg, and concrete - 805 kg.
Next, we will select the temperature value at which thermal energy will accumulate in the walls. For example, this will happen on a hot summer day with an air temperature of 270C. For the selected conditions, we calculate the heat capacity of the selected materials:

1. Wall made of wood: C=SudhmuddhΔT; Sder=2.3x175x27=10867.5 (kJ);
2. Concrete wall: C=SudhmuddhΔT; Cbet = 0.84x805x27 = 18257.4 (kJ);
3. Brick wall: C=SudhmuddhΔT; Skirp = 0.88x595x27 = 14137.2 (kJ).

From the calculations made, it is clear that with the same wall thickness, concrete has the highest heat capacity, and wood has the lowest. What does this mean? This suggests that on a hot summer day, the maximum amount of heat will accumulate in a house made of concrete, and the least amount of heat will accumulate in a house made of wood.

This explains the fact that in a wooden house it is cool in hot weather and warm in cold weather. Brick and concrete easily accumulate a fairly large amount of heat from the environment, but just as easily part with it.

Brick is widely used in private and professional construction. There are many varieties of this material. When choosing a building material for the construction or cladding of structures, its characteristics play an important role.

Characteristics affecting quality

The following product properties must be taken into account:

• thermal conductivity– this is the ability to transfer heat received from indoor air to the outside;
• heat capacity– the amount of heat that allows one kilogram of building material to be heated by one degree Celsius;
• density– determined by the presence of internal pores.

Below is a description of the different types of products.

Ceramic

Made from clay with the addition of certain substances. After manufacturing, they are subjected to heat treatment in specialized ovens. The specific heat capacity is 0.7 – 0.9 kJ, and the density is about 1300–1500 kg/m3.

Today, many manufacturers produce ceramic products. Such products differ not only in size, but also in their properties. For example, the thermal conductivity of a ceramic block is much lower than that of a regular one. This is achieved due to the large number of voids inside. The voids contain air that does not conduct heat well.

Silicate

Sand-lime brick is in high demand in construction; its popularity is due to its strength, availability and low cost. The specific heat capacity is 0.75 - 0.85 kJ, and its density is from 1000 to 2200 kg/m3.

The product has good sound insulation properties. A wall made of silicate product will insulate the structure from the penetration of various types of noise. It is most often used for the construction of partitions. The product is widely used as an intermediate layer in masonry, acting as a sound insulator.

Facing

Cladding blocks are widely used when finishing the external walls of buildings, not only because of their attractive appearance. The specific heat capacity of the brick is 900 J, and the density value is within 2700 kg/m3. This value allows the material to well resist the penetration of moisture through the masonry.

Refractory

Fireproof blocks can be divided into several types:

• carborundum;
• magnesite;
• dinas;
• fireclay.

Fire-resistant products are used to build high-temperature furnaces. Their density is 2700 kg/m3. The heat capacity of each type depends on the manufacturing conditions. Thus, the heat capacity index of carborundum brick at a temperature of 1000 o C is 780 J. Fireclay brick at a temperature of 100 o C has an index of 840 J, and at 1500 o C this parameter will increase to 1.25 kJ.

Influence of temperature conditions

The quality is greatly influenced by temperature. Thus, with an average density of the material, the heat capacity may differ depending on the ambient temperature.

From the above it follows that it is necessary to select building materials based on its characteristics and further scope of its application. This way it will be possible to build a room that will meet the necessary requirements.

Brick is a popular building material in the construction of buildings and structures. Many people only distinguish between red and white brick, but its types are much more diverse. They differ both in appearance (shape, color, size) and in properties such as density and heat capacity.

Traditionally, a distinction is made between ceramic and sand-lime bricks, which have different manufacturing technologies. It is important to know that the density of brick, its specific heat capacity, and each type can differ significantly.

Ceramic brick is made from various additives and fired. The specific heat capacity of ceramic brick is 700…900 J/(kg deg). The average density of ceramic bricks is 1400 kg/m3. The advantages of this type are: smooth surface, frost and water resistance, as well as resistance to high temperatures. The density of ceramic brick is determined by its porosity and can range from 700 to 2100 kg/m3. The higher the porosity, the lower the density of the brick.

Sand-lime brick has the following varieties: solid, hollow and porous; it has several standard sizes: single, one-and-a-half and double. The average density of sand-lime brick is 1600 kg/m3. The advantages of sand-lime brick are excellent soundproofing. Even if you lay a thin layer of such material, the sound insulation properties will remain at the proper level. The specific heat capacity of sand-lime brick ranges from 750 to 850 J/(kg deg).

The density values ​​of various types of bricks and their specific (mass) heat capacity at various temperatures are presented in the table:

It is necessary to note another popular type of brick – facing brick. He is not afraid of either moisture or cold. The specific heat capacity of the facing brick is 880 J/(kg deg). The facing brick has shades from bright yellow to fiery red. This material can be used for finishing and facing work. The density of this type of brick is 1800 kg/m3.

It is worth noting a separate class of bricks - refractory bricks. This class includes dinas, carborundum, magnesite and fireclay bricks. Refractory bricks are quite heavy - the density of bricks of this class can reach 2700 kg/m3.

Carborundum brick has the lowest heat capacity at high temperatures - it is 779 J/(kg deg) at a temperature of 1000°C. Masonry made from such bricks warms up much faster than fireclay bricks, but retains heat less well.

Refractory bricks are used in the construction of furnaces with operating temperatures up to 1500°C. The specific heat capacity of refractory bricks depends significantly on temperature. For example, the specific heat capacity of fireclay bricks is 833 J/(kg deg) at 100°C and 1251 J/(kg deg) at 1500°C.

Sources:

1. Franchuk A. U. Tables of thermal technical indicators of building materials, M.: Research Institute of Construction Physics, 1969 - 142 p.
2. Tables of physical quantities. Directory. Ed. acad. I. K. Kikoina. M.: Atomizdat, 1976. - 1008 p. construction physics, 1969 - 142 p.

In construction, a very important characteristic is the heat capacity of building materials. The thermal insulation characteristics of the walls of the building depend on it, and, accordingly, the possibility of a comfortable stay inside the building. Before you begin to familiarize yourself with the thermal insulation characteristics of individual building materials, you need to understand what heat capacity is and how it is determined.

Specific heat capacity of materials

Heat capacity is a physical quantity that describes the ability of a material to accumulate temperature from a heated environment. Quantitatively, specific heat capacity is equal to the amount of energy, measured in J, required to heat a body weighing 1 kg by 1 degree.
Below is a table of the specific heat capacity of the most common materials in construction.

• type and volume of heated material (V);
• the specific heat capacity of this material (Sud);
• specific gravity (msp);
• initial and final temperatures of the material.

Heat capacity of building materials

The heat capacity of materials, the table for which is given above, depends on the density and thermal conductivity of the material.

And the thermal conductivity coefficient, in turn, depends on the size and closure of the pores. A fine-porous material, which has a closed pore system, has greater thermal insulation and, accordingly, lower thermal conductivity than a large-porous one.

This is very easy to see using the most common materials in construction as an example. The figure below shows how the thermal conductivity coefficient and the thickness of the material influence the thermal insulation properties of external fences.

The figure shows that building materials with lower density have a lower thermal conductivity coefficient.
However, this is not always the case. For example, there are fibrous types of thermal insulation for which the opposite pattern applies: the lower the density of the material, the higher the thermal conductivity coefficient will be.

Therefore, you cannot rely solely on the indicator of the relative density of the material, but it is worth taking into account its other characteristics.

Comparative characteristics of the heat capacity of basic building materials

In order to compare the heat capacity of the most popular building materials, such as wood, brick and concrete, it is necessary to calculate the heat capacity for each of them.

First of all, you need to decide on the specific gravity of wood, brick and concrete. It is known that 1 m3 of wood weighs 500 kg, brick - 1700 kg, and concrete - 2300 kg. If we take a wall whose thickness is 35 cm, then through simple calculations we find that the specific gravity of 1 square meter of wood will be 175 kg, brick - 595 kg, and concrete - 805 kg.
Next, we will select the temperature value at which thermal energy will accumulate in the walls. For example, this will happen on a hot summer day with an air temperature of 270C. For the selected conditions, we calculate the heat capacity of the selected materials:

1. Wall made of wood: C=SudhmuddhΔT; Sder=2.3x175x27=10867.5 (kJ);
2. Concrete wall: C=SudhmuddhΔT; Cbet = 0.84x805x27 = 18257.4 (kJ);
3. Brick wall: C=SudhmuddhΔT; Skirp = 0.88x595x27 = 14137.2 (kJ).

From the calculations made, it is clear that with the same wall thickness, concrete has the highest heat capacity, and wood has the lowest. What does this mean? This suggests that on a hot summer day, the maximum amount of heat will accumulate in a house made of concrete, and the least amount of heat will accumulate in a house made of wood.

This explains the fact that in a wooden house it is cool in hot weather and warm in cold weather. Brick and concrete easily accumulate a fairly large amount of heat from the environment, but just as easily part with it.

Heat capacity and thermal conductivity of materials

Thermal conductivity is a physical quantity of materials that describes the ability of temperature to penetrate from one wall surface to another.

To create comfortable indoor conditions, it is necessary that the walls have a high heat capacity and a low thermal conductivity coefficient. In this case, the walls of the house will be able to accumulate thermal energy from the environment, but at the same time prevent the penetration of thermal radiation into the room.