Description:

A. S. Gorshkov, Cand. tehn Sciences, Director of the Scientific and Training Center "Monitoring and Rehabilitation of Natural Systems" of FGAOU VS "St. Petersburg State Polytechnic University"

P. P. Rymkevich, Cand. physical mat. Sciences, Professor of the Department of Physics FGKUOU VPO "Military Space Academy. A. F. Mozhaysky

N. I. Vatin, Doctor Tehn. Sciences, Professor, Director of the Engineering and Construction Institute of FGAOU VS "St. Petersburg State Polytechnic University"

In some cases, * the specific consumption of thermal energy in old panel buildings and modern monolithic-frame houses with two-layer walls from aerated concrete and facial brick is practically no different. One of the reasons for this phenomenon is that the designs of two-layer walls are often overwhelmed from the point of view of their heat-shielding parameters. Therefore, the calculation of the reduced resistance to the heat transfer of the two-layer wall structure was carried out, which showed that its heat engineering characteristics do not correspond to not only the required, but also the minimum permissible regulatory requirements. At the design stage, the coefficient of thermal uniformity of 0.9 is usually laid for this constructive solution, which is overshadowed for many cases. In addition, designers use unreasonable thermal conductivity of aerated concrete.

Currently, in the practice of designing and building buildings with a monolithic reinforced concrete frame and the floor support of the outer walls on monolithic or collection-monolithic reinforced concrete floors, one of the most common options for filling out the outer heat shutter is a structural solution of a wall consisting of two layers (Fig. 1):
- an internal undessel layer made by masonry from aerated concrete blocks with a thickness of 300-400 mm depending on the region of construction and its climatic parameters;
- Outdoor facing layer from facial brick thickness in one or two bricks.

Description of the design of wall fence

In the constructive solution under consideration, the inner layer of wall fencing performs the function of thermal insulation, the external function of protection against external climatic influences, ensures the required durability of the facades and forms the architectural appearance of the building. It is believed that this constructive solution meets the requirements of thermal protection for most regions of the Russian Federation.
In St. Petersburg, the traditional solution is a wall fencing, in which the thickness of the gas-concrete layer is 375 mm (Fig. 1a).

Regulatory requirements

In SNiP, 23-02-2003 "Thermal protection of buildings" (hereinafter referred to as SNiP 23-02) for buildings, three thermal protection indicators are installed:
a) individual elements of the building structures;
b) sanitary-hygienic, including the temperature difference between the inner air temperatures and on the surface of the enclosing structures and the temperature on the inner surface above the temperature of the dew point;
c) Specific heat consumption for the heating of a building, which allows to vary the magnitudes of the heat shield properties of various types of enclosing structures of buildings, taking into account the volume-planning solutions of the building and selecting microclimate maintenance systems to achieve the normalized value of this indicator.

The reduced resistance of heat transfer R. R 0 enclosing structures should be taken no less normalized values \u200b\u200b1 R. REQ, defined 2, depending on the degree and day of the heating period (hereinafter - the HSOP) of the construction region.

The HSOP for residential buildings located on the territory of St. Petersburg is 3 4,796 ° C, and the normalized meaning of the reduced heat transfer resistance for the outer walls of residential buildings is 4 3.08 m 2 ° C / W. At the same time, 5 decrease in the normalized value of the resistance of heat transfer for walls of residential and public buildings by 37% is allowed to perform a SNIP 23-02 (clause 5.1).

Thus, in relation to the case under consideration, the minimum permissible meaning of the resistance of heat transfer for the external walls of residential buildings, designed in St. Petersburg, should not be below 6 R. MIN \u003d 1.94 m 2 ° C / W.

Purpose and objectives of the study

The reduced resistance of heat transfer R. R 0 For exterior walls, it is necessary to count for the facade of the building or for one intermediate floor, taking into account the slopes of the openings without taking into account their fillings 7. Consider on a specific example, as this requirement is performed.

To do this, we will calculate the resistance of the heat transfer of the external walls of the intermediate floor of a typical apartment building with a constructive monolithic frame circuit and two-layer outer walls (Fig. 1) and compare the obtained value with the normalized R. REQ and minimally permissible R. Min values \u200b\u200bof the resistance of the heat transfer of the exterior walls of a residential apartment building.

Source data for heat engineering calculation

Construction area - St. Petersburg.
The appointment of the building is residential.
Calculated Temperature: Inner Air t. B \u003d 20 ° C; Outdoor air t. H \u003d -26 ° C.
Moisture zone - wet.
The humidity regime of the building is normal.
The conditions of operation of the enclosing structures - "b".

Thermal characteristics of materials used as part of a wall fence:
- cement-sandy solution γ O \u003d 1 800 kg / m 3, λ b \u003d 0.93 W / (M ° C);
- brickwork made of ordinary clay brick on a cement-sandy solution Γ O \u003d 1 800 kg / m 3, λ b \u003d 0.80 W / (M ° C);
- laying of wall unarmed blocks from autoclave aerated concrete density γ O \u003d 400 kg / m 3, λ b \u003d 0.14 W / (M ° C).

Border conditions:
Estimated heat transfer coefficient:
- the inner surface of the wall α int \u003d 8.7 W / (m 2 ° C);
- window blocks α int \u003d 8 W / (m 2 ° С);
- outer surface of the walls, windows α ext \u003d 23 W / (m 2 ° C).

The calculated schemes of external wall fragments are presented in Fig. 2.

Results of calculation

The reduced resistance to the heat transfer of the building fragments under consideration of the building is calculated on the basis of calculating temperature fields. The essence of the method is to model the stationary heat transfer process through the enclosing structures of buildings using computer programs 8. The method is designed to estimate the temperature mode and calculating the resistance of the heat transfer of the enclosing structures of the buildings or their fragments, taking into account the geometric shape, the location and characteristics of structural and thermal insulation layers, ambient air temperature, surface heat transfer coefficients.

The magnitude of the resistance of the heat transfer of the average intermediate floorR. R 0 is defined on the basis of calculating the resistance of a number of areas (fragments) R. R 0, I, taking into account the heat loss through the ends of the slabs of the floors, the slopes of window openings and balcony doors (see table), in particular the following fragments:
- Deaf Walls without openings, Dimensions: Height - floor height h. \u003d 3.0 m, in width - 1.2 m (Fig. 2a);
- Walls with window openings, dimensions: height - height of the floor h. \u003d 3.0 m, in width - the distance between the axes of window openings (Fig. 2b);
- Walls with a balcony door, sizes: height - height of the floor h. \u003d 3.0 m, in width - the distance between the axes of the seasplets (Fig. 2B).

The reduced resistance to the heat transfer of the external walls of the middle intermediate floor of an apartment building R. R 0, given the areas of the walls of walls by facades of the building, calculated by formula (1) (see the calculated formulas), is 1.81 m 2 ° C / W.

Calculating conditional (without taking into account the influence of heat-conducting inclusions on the heat engineering uniformity of the walls) heat transfer resistance R. 0 of the constructive solution under consideration (formula (2), calculated formulas), we obtain 2.99 m 2 ° C / W.

Hence the coefficient of thermal uniformity r., considered in the example of the outer wall of the standard intermediate floor, taking into account the slopes of the openings, without taking into account their fillings, will be 0, 61 (formula (3), calculated formulas).

What affects the coefficient of thermal heterogeneity?

In for a similar constructive solution, an even lower settlement value of the coefficient of heat engineering homogeneity was obtained r. = 0,48.

Differences in thermal homogeneity coefficients may be due to differences in design solutions used in the project, quantitative and qualitative composition of heat-conducting inclusions. Also, the heat engineering heterogeneity of the wall structure depends on the quality of installation.

In particular, it is noted that, according to the results of shooting 15, the thermograms measured in full-scale conditions, the resistance of the two-layer outer wall heat transfer was 1.3-1.5 m 2 ° C / W (with the conditional resistance of the heat transfer of the wall fencing R. 0 \u003d 3.92 m 2 ° C / W). It turns out that the actual coefficient of thermal uniformity may be even less than the calculated value and draw up according to r. \u003d (1.3 ÷ 1.5) / 3.92 \u003d 0.33 ÷ 0.38.

As one of the possible reasons for the detected inconsistency, there are poor-quality construction, due to the flow of incorrect form blocks. Indeed, the presence of cracks, faults, elevation and other defects of products can lead to an overrunning of a building solution, which acts as an additional heat-conducting inclusion, not taken into account when calculating.

It should be noted that the actual humidity of products from aerated concrete in the initial period of operation can significantly exceed the calculated one. In this regard, the thermal conductivity of products from aerated concrete can be addressed compared to the calculated values \u200b\u200btaken in the project, since the thermal conductivity of the material depends on the mass content of moisture.

Based on the calculations obtained, we formulate the following conclusions:

The reduced resistance of heat transfer R. R 0 two-layer wall structural design consisting of an internal self-supporting layer from aerated concrete wall unarmed blocks of the D400 density of D400 and the outer facing layer from facial ceramic bricks with a thickness of 120 mm, calculated on the basis of calculating temperature fields for the standard intermediate floor of an apartment building, is 1.81 m 2 ° C / W.
The design of the considered wall fence (Fig. 1) does not satisfy the regulatory requirements for thermal protection ( R. REQ \u003d 3.08 m 2 ° C / W).
The design of the wall fencing (Fig. 1) does not satisfy the minimum allowable thermal protection requirements ( R. MIN \u003d 1.94 m 2 ° C / W).
The coefficient of heat engineering homogeneity r. The design of the outer wall, made by masonry from the density of the density of the D400 density with a facing layer of facial brick, does not exceed 0.61.
The actual value of the coefficient of thermal uniformity of the constructive solution under consideration, taking into account the quality of the goods delivered to the object and the quality of their installation, may be significantly smaller compared to the calculated value.
To ensure the regulatory requirements for the level of thermal protection of the outer walls of buildings in the composition of the wall fence (Fig. 1), it should be either to increase the thickness of the aerated concrete blocks in the composition of a two-layer wall structure, or use the intermediate layer of thermal insulation materials with the calculated thermal conductivity of no more than 0.05 W / m ° C. The heat insulation layer should be located between aerated concrete and facial (facing) layers.
In all cases, to effectively remove moisture from the wall fencing between the layer of thermal insulation and facial brick, it is necessary to provide a ventilated gap, the effective cross section of which (thickness) should be determined by the calculation.

Literature

Krivoshein A. D., Fedorov S. V. To the question of calculating the resistance of the heat transfer // Engineering and construction journal. 2010. № 8.
Krivosheein A. D., Fedorov S. V. User Guide to the Temper software package for calculating temperature fields of the enclosing structures of buildings. Omsk: Sibadi, 1997.
Sokolov N. A., Gorshkov A.S. Thermal conductivity of building materials and products: the level of harmonization of Russian and European building standards // Construction materials, equipment, technologies of the XXI century. 2014. No. 6 (185).
Gagarin V. G. Thermophysical problems of modern wall enclosing structures of multi-storey buildings // Academia. Architecture and construction. 2009. № 5.
Nemova D. V., Spiridonova T. I., Kurazova V. G. Unknown properties of a known material // Construction of unique buildings and structures. 2012. No. 1.

* Data on the magnitude of the actual energy consumption of residential buildings of different years of construction was collected and analyzed by the authors of the article. - approx. Red ..

1 In accordance with the requirements of SNiP 23-02 (clause 5.3).

2 According to SNiP 23-02, Table 4.

3 According to the requirements of the RMD 23-16-2012 "St. Petersburg. Recommendations for the provision of energy efficiency of residential and public buildings ", Table 3.

4 Like, Table 9.

5 According to the requirements of SNiP 23-02, paragraph 5.13.

6 cm. Snip 23-02, formula (8).

7 According to the requirements of SNiP 23-02, paragraph 5.6.

8 In our case, the calculation is made using the TEMPER 3D software package.

Already mentioned in paragraph 2.1.7 the coefficient of thermal uniformity R It is an assessment of the impact of various cases of violation of the acuteness of the heat flux through the outdoor fencing. These can be regular internal connections that attract the layer of insulation and the facade layer to the inner structural layer; Brackets holding mounted facade systems, as well as adjacent fencing structures. For heat engineering calculations, R is a very convenient characteristic, as it immediately shows the share that the heat transfer resistance of the real design is in relation to the conditional resistance of the heat transfer of the design without heat-conducting inclusions and adjoints.

The values \u200b\u200bof the thermal homogeneity coefficient are obtained from a detailed direct calculation of a complex three-dimensional design by one of the numerical methods, for example, by the method of finite differences. Therefore, it is clear that the accuracy of the use of the coefficient of thermal uniformity depends on how closely the calculation reflects the calculated case.

The range of values \u200b\u200bof the coefficient of thermal uniformity lies in very wide limits: 1 - 0.5 and even lower. Of course, architects and designers strive for the design of enclosing structures with high R, however, in some cases it is almost impossible. Such a significant range of R suggests that when calculating heat transfer engineer, the heat engineer should be very responsible to assess the resistances of the heat transfer of fences, since the overestimation of the value of the coefficient of thermal uniformity can lead to an understatement of the actual heat loss, and an understatement to the extent of the building insulation costs.

Calculation of the coefficient of heat engineering homogeneity of enclosing structures on table values

1. Calculation of the coefficient of thermal uniformity R under formula (2.7)
Table B.1.
Table to determine the coefficient Ki
0,1 0,2 0,4 0,6 0,8 1 1,5 2 2 1,02 1,01 1,01 1,01 1 1 1 1 5 1,16 1,11 1,07 1,05 1,04 1,03 1,02 1,01 10 1,33 1,25 1,15 1,1 1,08 1,06 1,04 1,03 30 1,63 1,47 1,27 1,18 1,14 1,11 1,07 1,05 10 - 40 2,65 2,2 1,77 1,6 1,55 - - - 2 1,02 1,01 1,01 1,01 1,01 1,01 1,01 1 5 1,12 1,08 1,05 1,04 1,03 1,03 1,02 1,01 10 1,18 1,13 1,07 1,05 1,04 1,04 1,03 1,02 30 1,21 1,16 1,1 1,07 1,05 1,04 1,03 1,02 2 1,05 1,04 1,03 1,02 1,01 1,01 1,01 1,01 5 1,28 1,21 1,13 1,09 1,07 1,06 1,04 1,03 10 1,42 1,34 1,22 1,14 1,11 1,09 1,07 1,05 30 1,62 1,49 1,3 1,19 1,14 1,12 1,09 1,06 2 1,06 1,04 1,03 1,02 1,02 1,01 1,01 1,01 5 1,25 1,2 1,14 1,1 1,08 1,07 1,05 1,03 10 1,53 1,42 1,25 1,16 1,12 1,11 1,08 1,05 30 1,85 1,65 1,38 1,24 1,18 1,15 1,11 1,08 2 1,03 1,02 1,02 1,01 1,01 1,01 1 1 5 1,12 1,10 1,07 1,05 1,04 1,03 1,02 1,01 10 1,2 1,16 1,1 1,07 1,06 1,05 1,03 1,02 30 1,28 1,22 1,14 1,09 1,07 1,06 1,04 1,03 5 1,32 1,25 1,17 1,13 1,1 1,08 1,06 1,04 10 1,54 1,42 1,27 1,19 1,14 1,12 1,09 1,06 30 1,79 1,61 1,38 1,26 1,19 1,16 1,12 1,08 2 1,07 1,05 1,04 1,03 1,02 1,02 1,01 1,01 5 1,36 1,28 1,18 1,14 1,11 1,09 1,07 1,05 10 1,64 1,51 1,33 1,23 1,18 1,15 1,11 1,08 30 2,05 1,82 1,5 1,33 1,25 1,21 1,16 1,11
The diagram of heat-conducting inclusion λm / λ. Ki coefficient at α / δ
I.
II.
III with C / Δ 0,25
0,5
0,75
IV with C / Δ 0,25
0,5
0,75

Table B.2.
Table for determining the coefficient ψ
0,25 0,5 1 2 5 10 20 50 150 0,024 0,041 0,066 0,093 0,121 0,137 0,147 0,155 0,19 - - - 0,09 0,231 0,43 0,665 1,254 2,491 0,25 0,016 0,02 0,023 0,026 0,028 0,029 0,03 0,03 0,031 0,5 0,036 0,054 0,072 0,083 0,096 0,102 0,107 0,109 0,11 0,75 0,044 0,066 0,095 0,122 0,146 0,161 0,168 0,178 0,194 0,25 0,015 0,02 0,024 0,026 0,029 0,031 0,033 0,039 0,048 0,5 0,037 0,056 0,076 0,09 0,103 0,12 0,128 0,136 0,15 0,75 0,041 0,067 0,01 0,13 0,16 0,176 0,188 0,205 0,22
Thermal Conduct Scheme The values \u200b\u200bof the coefficient ψ at αλt / Δisol λisol
I.
IIB
III with C / Δ
IV with C / Δ

Note. Designations and schemes accepted by adj. 5 * SNiP II-3-79 * (ed. 1998)

Example of calculation
Determine the reduced resistance to the heat transfer panel with an effective insulation (polystyrene foam) and steel trimming of a public building.
A. Source data
Panel sizes 6 × 2 m. Constructive and heat engineering panel characteristics:
The thickness of steel trimbs 0.001 m, the thermal conductivity coefficient λ \u003d 58 W / (M · ° C), the thickness of the polystyrene foam insulation 0.2 m, the thermal conductivity coefficient is 0.04 W / (M · ° C).
Flashing of sheet material along the extended sides of the panel leads to the formation of heat-conducting inclusion of type IIB (adj. 5 * SNiP II-3-79 * (ed. 1998)), having a width of a \u003d 0.002 m.
B. Calculation order
The heat transfer resistance was away from turning on ROCON and on the heat-conducting inclusion RO ':
ROCON \u003d 1 / 8.7 + 2 (0,001 / 58) + 0.2 / 0.04 + 1/2 \u003d 5.16 m2 · ° C / W
RO '\u003d 1 / 8.7 + (2 · 0.001 + 0.2) / 58 + 1/23 \u003d 0.162 m2 · ° C.
The value of the dimensionless parameter of the heat-conducting power on for Table. B.2.
Aλt / Δisolλisol \u003d 0002 · 58 / (0.2 · 0.04) \u003d 14.5
Table. B.2 by interpolation determine the magnitude ψ
ψ \u003d 0.43 + [(0.665 - 0,665) · 4,5] / 10 \u003d 0.536
Ki coefficient according to formula (2.8)
ki \u003d 1 + 0,536 \u003d 52.94
The coefficient of thermal uniformity of the panel by formula (2.7)
R \u003d 1 / (0.002 · 6 · 52.94) \u003d 0.593
The reduced resistance to heat transfer by formula (2.6)
Ror \u003d 0.593 · 5,16 \u003d 3.06 m2 · ° C / W.
2. Calculation of the coefficient of thermal uniformity r under formula (2.9)
Table B.3.
Table to determine the effect of FI effect

Type of heat-conducting inclusion 10 20 RCM / RKCON: 1 or more - 0,07 0,12 0,9 - 0,14 0,17 0,8 0,01 0,17 0,19 0,7 0,02 0,24 0,26 0,6 0,03 0,31 0,34 0,5 0,04 0,38 0,41 0,4 0,05 0,45 0,48 0,3 0,06 0,52 0,55 Window slopes 20 mm Δf '/ Δw': 0,2 0,67 0,3 0,62 0,4 0,55 0,5 0,48 0,6 0,41 0,7 0,35 0,8 0,28 Thickening of the inner reinforced concrete layer RY / RKCON: 0,9 - 0,8 - 0,7 - 0,6 - 0,5 - Flexible bonds with a diameter, mm: 4 - 6 - 8 - 10 - 12 - 14 - 16 - 18 - 20 -

FIR influence coefficient
Junctions	without adjoining internal fences	With the adjoining of internal fences
		without ribs	with ribs thick, mm


-
0,1
0,13
0,2
0,27
0,33
0,39
0,45
without ribs		with ribs thick
		10 mm

0,45		0,58
0,41		0,54
0,35		0,47
0,29		0,41
0,23		0,34
0,17		0,28
0,11		0,21


0,02		-
0,12		-
0,28		-
0,51		-
0,78		-

0,05		-
0,1		-
0,16		-
0,21		-
0,25		-
0,33		-
0,43		-
0,54		-
0,67		-

Notes:
1. The table shows RKCON, RCM, RY - thermal resistance, m2 · ° C / W, respectively, the panel outside the heat-conducting power on, joint, thickening the inner reinforced concrete layer, determined by formula (2.2); Δf 'and Δw' - distances, m, from the longitudinal axis of the window box to its edge and to the inner surface of the panel.
2. Intermediate values \u200b\u200bshould be determined by interpolation.

Example of calculation
Determine the reduced resistance to the heat transfer ROR of the one-gradder three-layer reinforced concrete panel on flexible links with the window opening of a large-pointed residential building of the III series.
A. Source data
A 300 mm thick panel contains an outer and inner reinforced concrete layers, which are interconnected by two suspension (in transferentials), a tire located in the lower zone of the windows section, and the struts: 10 - in horizontal joints and 2 - in the window slope area (Fig. B .one).
Fig. B.1. Construction of the three-layer panel on flexible ties
1 - strut; 2 - loop; 3 - suspension; 4 - concrete thickening (δ \u003d 75 mm of the inner reinforced concrete layer); 5 - troops
In tab. B.4 shows the calculated panel parameters.
In the suspension zone and loops, the inner concrete layer has thickening, replacing a part of the insulation layer.
Table 4.
B. Calculation order
The design of the fence contains the following heat-conducting inclusions: horizontal and vertical joints, window slopes, thickening of the inner reinforced concrete layer and flexible connections (suspension, struts, struts).
To determine the coefficient of the effect of individual heat-conducting inclusions, we calculate the thermal resistance of individual sections of the panel in the formula (2.2):
In the thickening zone of the inner reinforced concrete layer
Ry \u003d 0.175 / 2.04 + 0.06 / 0.042 + 0.065 / 2.04 \u003d 1.546 m2 · ° C / W;
By horizontal junction
Rjng \u003d 0.1 / 2,047 + 0,065 / 2.04 \u003d 2.95 m2 · ° C / W;
Vertical junction
Rjnv \u003d 0.175 / 2,04 + 0.06 / 0.047 + 0.065 / 2.04 \u003d 1.394 m2 · ° C / W
Thermal panel resistance away from heat-conducting inclusions
Rkcon \u003d 0.1 / 2.042 + 0,065 / 2.04 \u003d 3,295 m2 · ° C / W.
Conditional resistance to heat transfer away from heat-conducting inclusions
ROCON \u003d 1 / 8.7 + 3,295 + 1/2 \u003d 3.453 m2 · ° C / W.
Since the panel has a vertical axis of symmetry, then the definition of subsequent values \u200b\u200bwe carry out for half the panel:
We define the area of \u200b\u200bhalf of the panel without taking into account the opening windows
AO \u003d 0.5 · (2.8 · 2.7 - 1.48 · 1.51) \u003d 2.66 m2.
The thickness of the panel Δw \u003d 0.3 m.
We define the area of \u200b\u200bthe influence of AI and FI coefficient for each heat-conducting panel switching on:
For horizontal junction
RJNG / RKCON \u003d 2.95 / 3,295 \u003d 0.895
Table. B.2 Fi \u003d 0.1. The area of \u200b\u200binfluence area by formula (2.10)
Ai \u003d 0.3 · 2 · 1.25 \u003d 0.75 m2;
For vertical junction
RJNV / RKCON \u003d 1,394 / 3,295 \u003d 0,423
Table. B.2 Fi \u003d 0.375. The area of \u200b\u200binfluence area by formula (2.10)
Ai \u003d 0.3 · 2.8 \u003d 0.84 m2.
For window slopes at Δf '\u003d 0.065 m and Δw' \u003d 0.18 m, in the table. B.2 Fi \u003d 0.374. The area of \u200b\u200bthe area of \u200b\u200bhalf of the window opening, taking into account the angular sites, is determined by the formula (2.11)
Ai \u003d 0.5 · \u003d 1.069 m2;
For concrete thickening of the inner reinforced concrete layer in the suspension zone and loops with RY '/ RKCON \u003d 1.546 / 3,295 \u003d 0.469, according to Table. B.2 Fi \u003d 0.78. The total area of \u200b\u200bthe area of \u200b\u200binfluence of thickens of the suspension and loops is found by formula (2.12)
Ai \u003d (0,6 + 2 · 0.3) (0.47 + 0.1) + (0.2 + 0.3 + 0,1) (0.42 + 0.3 + 0.075) \u003d 1,161 m2 ;
For suspension (rod diameter 8 mm) by table. G. 3 Fi \u003d 0.16, the area of \u200b\u200bthe influence of the formula (2.12)
Ai \u003d (0.13 + 0.3 + 0.14) (0.4 + 2 · 0.3) \u003d 0.57 m2;
For a pier (rod diameter 8 mm) by table. B.3 Fi \u003d 0.16, according to the formula (2.12)
Ai \u003d (0.13 + 0.3) (0.22 + 0.3 + 0.09) \u003d 0.227 m2.
For strut (rod diameter 4 mm) by table. B.2 Fi \u003d 0.05.
In determining the total area of \u200b\u200bthe area of \u200b\u200binfluence of the five spacer, it should be borne in mind that the width of the area of \u200b\u200bthe effect on the side of the joint is limited by the edge of the panel and is 0.09 m. According to formula (2.13):
Ai \u003d 5 (0.3 + 0.3) (0.3 + 0.09) \u003d 1.17 m2.
Calculate R by formula (2.9)
R \u003d 1 / (1 + · (0.84 · 0.375 + 0.75 · 0.1 + 1,069 · 0.374 + 1,161 · 0.78 + 0.57 · 0.16 + 0.227 · 0.16 + 1,17 · 0.05)) \u003d 0.71
The reduced resistance of the heat transfer panel is determined by formula (2.6)
Ror \u003d 0.71 · 3,453 \u003d 2.45 m2 · ° C / W.

All without exception walls and coverage (and other types of enclosing structures of buildings and structures) cannot be called isothermal. In other words, saying the distribution of the temperature field in a section perpendicular to the heat flow in the structure is not a constant value, due to the presence of all sorts of heat-conducting inclusions (the so-called "cold bridges"), which are almost always present in the design of the fence. As heat-conducting inclusions, reinforcement steel or composite rods in the dressing of facing masonry to the supporting structures, cement-sandy solution or glue in masonry, fixators of thermal insulation materials, corners and adjuncing overlaps and coatings are possible. Therefore, such a concept is taken as the reduced heat transfer resistance of the R REQ fence, which is equal to the averaged heat engineering characteristics of the combined (inhomogeneous composition) of the structure, the flow of heat in which, with a permanent mode, which is not one-dimensional in the perpendicular cross section of the structure.

Thus, R Req is equal to the resistance of the heat transfer of the single-layer fencing of the same unit of the area, which passes the heat flow is the same as in the actual design at the same temperature gradient between the inner and outer surface of the fence. In that case, if you drop the influence of the above thermal-conducting inclusions or, as we have already spoken "cold bridges" in the design of the fence, its heat shielding characteristics are conveniently submitted using the concept of conditional resistance to heat transfer. Once we are determined with such concepts as conditional and resistance, you can enter the definition of the coefficient of heat engineering homogeneity. r. which represents the ratio of the resistance to heat transfer to the conditional resistance to heat transfer. In this way, r. It depends on the characteristics of the materials and thicknesses of the components of the enclosing design of the layers, as well as on the presence of the heat-conducting inclusions themselves. The numerical value of the ratio R rates how efficiently the thermal insulation properties of the insulation in the enclosing structure and the effect on this is the presence of heat-insulating inclusions. Based on the decisions on the design of the fence, the value of the coefficient of heat engineering homogeneity varies from 0.5 to 0.98. If it is equal to 1, it means that there is virtually heat-conducting inclusions, and the efficiency of the layer of thermal insulation material is maximum used.

Determination of the coefficient of heat engineering uniformity of enclosing structures.

The value of the coefficient r. It is necessary to determine using sufficiently time-consuming calculations using the method of temperature fields or by means of heat-conducting measurements on the basis of the experiment. In particular, the coefficient of thermal uniformity - r. You can also calculate on the instructions that are in the SP 23-101-2004 "Design of thermal protection of buildings". In practice, it is enough to take the value of the software coefficient. If, when the coefficient of thermal uniform adopted according to regulatory documents, the fence design still does not meet the current standards, then the coefficient can be enhanced by confirming its values \u200b\u200bapplied by the calculation.

In the event that in the calculated design of the fence, it is not possible to withstand the requirements of the regulatory documents of the heat-engineering uniformity, the use of such a design is subject to revision. There are various options, such as replacing the types of types and types of materials in the fencing, reducing the thickness of the seams in the masonry, replacing the binding steel reinforcement to the composite, change the size of the masonry blocks.

Accounting for the coefficient when calculating masonry.

If the laying of cellular concrete, ceramzitbeton and polystyrene blocks is used in the design of the fences, cement-sand or glue laying seams should be taken into account. This is primarily due to the fact that for masonry in the joint venture 23-10-2004 in the heat engineering calculation of the fences in determining the above value of the heat transfer values \u200b\u200bof the thermal conductivity of the materials should be taken taking into account the presence of seams. In the SP 23-101-2004 in Appendix D for materials such as cellular concrete, ceramzite concrete, polystyrene bauton, etc. The heat engineering characteristics of solid (solid) materials are presented. This is due to the fact that actually the seams in the masonry have much greater thermal conductivity than the material itself. For the correct enclosing structures using the above materials, it is also necessary to introduce the coefficient of thermal uniformity.

Figure H.1 - diagrams of heat-conducting inclusions in enclosing structures

H.1 Calculation of the coefficient of thermal uniformity of formula (12)

Of a real army of rules

Table H.1 - Definition of the coefficient

			Coefficient at (Figure H.1)






























Note - Designations taken in Figure H.1.

Example of calculation

Determine the reduced resistance to the heat transfer panel with an effective insulation (polystyrene foam) and steel trimming industrial buildings.

Initial data

Panel size 6x2 m. Constructive and heat engineering panel characteristics:

thickness of steel trimbs 0.001 m, thermal conductivity coefficient;

the thickness of the polystyrene insulation is 0.2 m, the thermal conductivity coefficient.

Flashing of sheet material along the extended sides of the panel leads to the formation of heat-conducting inclusion of type IIB (Figure H.1) having a width \u003d 0.002 m.

Calculation order

Resistance heat transfer away from inclusion and heat-conducting inclusion:

The value of the dimensionless parameter of the heat-conducting inclusion on Table H.2

0.002 · 58 / (0.2 · 0.04) \u003d 14.5.

Table H.2 - Definition of the coefficient

# G0Shem heat-conducting inclusion in Figure H.1		The values \u200b\u200bof the coefficient at (in Figure H.1

According to Table H.2 in interpolation, we determine the magnitude

0,43+[(0,665-0,43)4,5]/10=0,536.

Coefficient, according to formula (13)

The coefficient of thermal uniformity of the panel by formula (12)

The reduced resistance to heat transfer by formula (11)

H.2 Calculation of the coefficient of heat engineering homogeneity by formula (14)

Of a real army of rules

Example of calculation

Determine the reduced resistance to heat transfer of the one-point three-layer reinforced concrete panel on flexible links with the window opening of a large-pasted residential building of the III-133 series.

Initial data

The 300 mm thick panel contains an outdoor and inner reinforced concrete layers, which are interconnected by two suspension (in simpleness), a subpatch located in the lower zone of the subcast section, and the struts: 10 - in horizontal joints and 2 - in the window of the window slope (Figure N. 2).

1 - strut; 2 - loop; 3 - suspension;

4 - concrete thickening (\u003d 75 mm of the inner reinforced concrete layer); 5 - troops

Figure H.2 - Construction of the three-layer panel on flexible ties

In # M12293 0 1200037434 4120950664 4294967273 80 29972111231 403162211 2325910542 403162211 2520Tube N.4 # S The calculated panel parameters are given.

In the suspension zone and loops, the inner concrete layer has thickening, replacing a part of the insulation layer.

Calculation order

The design of the fence contains the following heat-conducting inclusions: horizontal and vertical joints, window slopes, thickening of the inner reinforced concrete layer and flexible connections (suspension, struts, struts).

To determine the coefficient of the effect of individual heat-conducting inclusions, we calculate the thermal resistance of individual sections of the panel in the formula (7):

in the thickening zone of the inner reinforced concrete layer

by horizontal junction

vertical junction

thermal panel resistance away from heat-conducting inclusions

Conditional resistance to heat transfer away from heat-conducting inclusions

Since the panel has a vertical axis of symmetry, then the definition of subsequent values \u200b\u200bwe carry out for half the panel.

We define the area of \u200b\u200bhalf of the panel without taking into account the opening windows

Panel thickness \u003d 0.3 m.

We define the area of \u200b\u200bthe influence zones and the coefficient of each heat-conducting panel switching on:

for horizontal junction

2,95/3,295=0,895.

Table H.3 \u003d 0.1. Square area of \u200b\u200binfluence according to formula (15)

for vertical junction

Table H.3 - Definition of influence coefficient

# G0VID heat-conducting inclusion	Influence coefficient
	Without adjoining internal fences	With the adjoining of internal fences
		Without ribs	With ribs thick, mm










Window slopes	Without ribs	With ribs thick, mm: