Snip 3.06 07 86 bridges and pipes. Bridges and pipes
GOST 25380-82
Group W19
STATE STANDARD OF THE USSR UNION
BUILDINGS AND CONSTRUCTIONS
Method for measuring heat flux density,
passing through enclosing structures
Buildings and structures.
Method of measuring density of heat flows
passing through enclosure structures
Date of introduction 1983 - 01-01
APPROVED AND ENTERED INTO EFFECT by Resolution of the USSR State Committee for Construction Affairs dated July 14, 1982 No. 182
REISSUE. June 1987
This standard establishes a unified method for determining the density of heat flows passing through single-layer and multi-layer enclosing structures of residential, public, industrial and agricultural buildings and structures during experimental research and under operating conditions.
Heat flow density measurements are carried out at ambient temperatures from 243 to 323 K (from minus 30 to plus 50°C) and relative air humidity up to 85%.
Measurements of heat flow density make it possible to quantify the thermal technical qualities of building envelopes and structures and establish real heat consumption through external building envelopes.
The standard does not apply to translucent enclosing structures.
1. General Provisions
1.1. The method for measuring heat flux density is based on measuring the temperature difference across a “auxiliary wall” (plate) installed on the building envelope. This temperature difference, proportional in the direction of the heat flow to its density, is converted into emf. batteries of thermocouples located in the “auxiliary wall” in parallel along the heat flow and connected in series along the generated signal. The "auxiliary wall" and the thermocouple bank form a heat flow converter
1.2. The heat flux density is measured on the scale of a specialized device, which includes a heat flux converter, or is calculated from the results of measuring the emf. on pre-calibrated heat flow converters.
The diagram for measuring heat flux density is shown in the drawing.
Heat flux density measurement circuit
1 - enclosing structure; 2 - heat flow converter; 3 - emf meter;
Indoor and outdoor air temperature; , , - outside temperature,
the internal surfaces of the enclosing structure near and under the converter, respectively;
Thermal resistance of the enclosing structure and heat flow converter;
Heat flux density before and after fixing the converter.
2. Equipment
2.1. To measure the density of heat fluxes, the ITP-11 device is used (the use of the previous model of the ITP-7 device is allowed) according to the technical conditions.
Technical characteristics of the ITP-11 device are given in reference Appendix 1.
2.2. During thermal engineering tests of enclosing structures, it is allowed to measure the density of heat flows using separately manufactured and calibrated heat flow converters with thermal resistance up to 0.025-0.06 (sq.m)/W and instruments that measure the emf generated by the converters.
It is allowed to use a converter used in the installation to determine thermal conductivity in accordance with GOST 7076-78.
2.3. Heat flow converters according to clause 2.2 must meet the following basic requirements:
materials for the “auxiliary wall” (plate) must retain their physical and mechanical properties at ambient temperatures from 243 to 323 K (from minus 30 to plus 50 ° C);
materials should not be wetted or moistened with water in the liquid and vapor phases;
the ratio of the diameter of the transducer to its thickness must be at least 10;
converters must have security zone, located around the thermocouple bank, the linear size of which must be at least 30% of the radius or half the linear size of the transducer;
each manufactured heat flow converter must be calibrated in organizations that, in accordance with the established procedure, received the right to produce these converters;
under the above conditions external environment The calibration characteristics of the converter must be maintained for at least one year.
2.4. Calibration of converters according to clause 2.2 can be carried out on an installation for determining thermal conductivity in accordance with GOST 7076-78, in which the heat flux density is calculated based on the results of measuring the temperature difference on reference samples of materials certified in accordance with GOST 8.140-82 and installed instead of the test samples. The calibration method for the heat flow converter is given in recommended Appendix 2.
2.5. Converters are checked at least once a year, as indicated in paragraphs. 2.3, 2.4.
2.6. To measure emf. heat flow converter, it is allowed to use a portable potentiometer PP-63 in accordance with GOST 9245-79, digital voltammeters V7-21, F30 or other emf meters that have a calculated error in the region of the measured emf. heat flow converter does not exceed 1% and the input resistance is not less than 10 times the internal resistance of the converter.
When performing thermal testing of enclosing structures using separate converters, it is preferable to use automatic recording systems and instruments.
3.Preparation for measurement
3.1. Measurement of heat flow density is carried out, as a rule, from the inside of the enclosing structures of buildings and structures.
It is allowed to measure the density of heat flows from the outside of enclosing structures if it is impossible to carry them out from the inside (aggressive environment, fluctuations in air parameters), provided that a stable temperature on the surface is maintained. Heat transfer conditions are monitored using a temperature probe and means for measuring heat flux density: when measured for 10 minutes, their readings must be within the measurement error of the instruments.
3.2. Surface areas are selected that are specific or characteristic of the entire enclosing structure being tested, depending on the need to measure local or average heat flux density.
The areas selected for measurements on the enclosing structure must have a surface layer of the same material, the same treatment and surface condition, have the same conditions for radiant heat transfer and should not be in close proximity to elements that can change the direction and value of heat flows.
3.3. The areas of the surface of the enclosing structures on which the heat flow converter is installed are cleaned until visible and tactile roughness is eliminated.
3.4. The transducer is tightly pressed over its entire surface to the enclosing structure and fixed in this position, ensuring constant contact of the heat flow transducer with the surface of the areas under study during all subsequent measurements.
When attaching the converter between it and the enclosing structure, the formation of air gaps is not allowed. To eliminate them, a thin layer of technical petroleum jelly is applied to the surface area at the measurement sites, covering surface irregularities.
The transducer can be fixed along its side surface using a solution of building plaster, technical petroleum jelly, plasticine, a rod with a spring and other means that prevent distortion of the heat flow in the measurement area.
3.5. For operational measurements of heat flux density, the loose surface of the transducer is glued with a layer of material or painted over with paint with the same or similar degree of blackness with a difference of 0.1 as that of the material of the surface layer of the enclosing structure.
3.6. The reading device is located at a distance of 5-8 m from the measurement site or in an adjacent room to eliminate the influence of the observer on the heat flow value.
3.7. When using devices for measuring emf that have restrictions on ambient temperature, they are placed in a room with an air temperature acceptable for the operation of these devices, and the heat flow converter is connected to them using extension wires.
When carrying out measurements with the ITP-1 device, the heat flow converter and the measuring device are located in the same room, regardless of the air temperature in the room.
3.8. The equipment according to clause 3.7 is prepared for operation in accordance with the operating instructions for the corresponding device, including taking into account required time holding the device to establish a new temperature regime in it.
4. Taking measurements
4.1. Heat flux density measurements are carried out:
when using the ITP-11 device - after restoring heat exchange conditions in the room near the control sections of the enclosing structures, distorted during preparatory operations, and after restoring directly in the test area the previous heat transfer regime, disturbed when attaching the converter;
during thermal tests using heat flow converters according to clause 2.2 - after the onset of a new steady state of heat exchange under the converter.
After completing the preparatory operations according to paragraphs. 3.2-3.5 when using the ITP-11 device, the heat exchange mode at the measurement site is restored in approximately 5 - 10 minutes, when using heat flow converters according to clause 2.2 - after 2-6 hours.
An indicator of the completion of the transient heat transfer regime and the possibility of measuring the heat flux density can be considered the repeatability of the results of measuring the heat flux density within the established measurement error.
4.2. When measuring the heat flow in a building envelope with a thermal resistance of less than 0.6 (sq.m)/W, the temperature of its surface at a distance of 100 mm from the converter, below it, and the temperature of the internal and external air at a distance of 100 mm from the wall are simultaneously measured using thermocouples .
5. Processing of results
5.1. When using ITP-11 devices, the heat flux density value (W/sq.m) is obtained directly from the device scale.
5.2. When using separate converters and millivoltmeters to measure emf. The heat flux density passing through the converter, , W/sq.m, is calculated using the formula
(1)
5.3. The calibration coefficient of the converter, taking into account the test temperature, is determined according to the recommended Appendix 2.
5.4. The value of heat flux density, W/sq.m, when measuring according to clause 4.3 is calculated using the formula
(2)
|
Where - And - |
outside air temperature opposite the converter, K (°C); surface temperature at the measurement site near the transducer and under the transducer, respectively, K (°C). |
5.5. The measurement results are recorded in the form given in the recommended Appendix 3.
5.6. The result of determining the heat flux density is taken as the arithmetic mean of the results of five measurements at one position of the converter on the enclosing structure.
Annex 1
Information
Technical characteristics of the ITP-11 device
The ITP-11 device is a combination of a heat flow converter into an electrical signal direct current with a measuring device, the scale of which is calibrated in units of heat flux density.
1. Heat flux density measurement limits: 0-50; 0-250 W/sq.m.
2. Instrument scale division value: 1; 5 W/sq.m.
3. The main error of the device is expressed as a percentage at an air temperature of 20 °C.
4. The additional error from changes in air temperature surrounding the measuring device does not exceed 1% for every 10 K (°C) temperature change in the range from 273 to 323 K (from 0 to 50°C).
The additional error from changing the temperature of the heat flow converter does not exceed 0.83% per 10 K (°C) temperature change in the range from 273 to 243 K (from 0 to minus 30 °C).
5. Thermal resistance of the heat flow converter is no more than 3·10 (sq/m·K)/W.
6. Time to establish readings - no more than 3.5 minutes.
7. Overall dimensions of the case - 290x175x100 mm.
8. Overall dimensions of the heat flow converter: diameter 27 mm, thickness 1.85 mm.
9. Overall dimensions of the measuring device - 215x115x90 mm.
10 The length of the connecting electrical wire is 7 m.
11. The weight of the device without a case is no more than 2.5 kg.
12. Power supply - 3 elements "316".
Appendix 2
Heat flow converter calibration method
The manufactured heat flow converter is calibrated using an installation to determine thermal conductivity building materials according to GOST 7076-78, in which, instead of the test sample, a calibrated converter and a reference sample of material according to GOST 8.140-82 are installed.
When calibrating, the space between the thermostatic plate of the installation and the reference sample outside the converter must be filled with a material similar in thermophysical properties to the material of the converter in order to ensure the one-dimensionality of the heat flow passing through it in the working area of the installation. E.M.F. measurement on the converter and the reference sample is carried out by one of the devices listed in clause 2.6 of this standard.
The calibration coefficient of the converter, W/(sq.m·mV) at a given average temperature of the experiment is found from the results of measurements of heat flux density and emf. according to the following relation
The heat flux density is calculated from the results of measuring the temperature difference on a reference sample using the formula
|
Where |
thermal conductivity of the reference material, W/(m.K); |
|
|
temperature of the upper and lower surfaces of the standard, respectively, K(°С); |
||
|
standard thickness, m. |
It is recommended to select the average temperature in experiments when calibrating the converter in the range from 243 to 323 K (from minus 30 to plus 50 °C) and maintain it with a deviation of no more than ±2 K (°C).
The result of determining the converter coefficient is taken to be the arithmetic mean of the values calculated from the measurement results of at least 10 experiments. The number of significant digits in the value of the calibration coefficient of the converter is taken in accordance with the measurement error.
The temperature coefficient of the converter, K (), is found from the results of emf measurements. in calibration experiments at different average temperatures of the converter according to the ratio
,
|
Where , |
Average temperatures of the converter in two experiments, K (°C); |
|
Calibration coefficients of the converter at average temperature and respectively, W/(sq.m·V). |
The difference between the average temperatures must be at least 40 K (°C).
The result of determining the temperature coefficient of the converter is taken to be the arithmetic mean value of the density, calculated from the results of at least 10 experiments with different average temperatures of the converter.
The value of the calibration coefficient of the heat flow converter at test temperature, W/(sq.m mV), is found using the following formula
,
|
Where |
(The value of the calibration coefficient of the converter at the test temperature W/(sq.m mV) Type and number measuring instrument
Operator signature ___________________ Date of measurements ___________ The text of the document is verified according to: official publication Gosstroy USSR - M.: Standards Publishing House, 1988 | |||||||||||||||||||||||||||||||||||||||||||||||||||
GOST 25380-2014
INTERSTATE STANDARD
BUILDINGS AND CONSTRUCTIONS
Method for measuring the density of heat flows passing through building envelopes
Buildings and structures. Method of measuring density of heat flows passing through enclosing structures
MKS 91.040.01
Date of introduction 2015-07-01
Preface
The goals, basic principles and basic procedure for carrying out work on interstate standardization are established in GOST 1.0-92 "Interstate standardization system. Basic provisions" and GOST 1.2-2009 "Interstate standardization system. Interstate standards, rules, recommendations for interstate standardization. Rules for development, adoption , updates and cancellations"
Standard information
1 DEVELOPED by the Federal State budgetary institution "Research Institute of Building Physics of the Russian Academy of Architecture and Construction Sciences (NIISF RAASN) with the participation of SKB Stroypribor LLC
2 INTRODUCED by the Technical Committee for Standardization TC 465 "Construction"
3 ADOPTED by the Interstate Council for Standardization, Metrology and Certification (protocol dated September 30, 2014 N 70-P)
The following voted for adoption:
Short name of the country according to MK (ISO 3166) 004-97 | Abbreviated name of the national standardization body |
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Ministry of Economy of the Republic of Armenia |
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Belarus | State Standard of the Republic of Belarus |
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Kyrgyzstan | Kyrgyzstandard |
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Moldova-Standard |
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Rosstandart |
4 By Order of the Federal Agency for Technical Regulation and Metrology dated October 22, 2014 N 1375-st, the interstate standard GOST 25380-2014 was put into effect as a national standard Russian Federation from July 1, 2015
5 INSTEAD GOST 25380-82
(Amendment. IUS N 7-2015).
Information about changes to this standard is published in the annual information index "National Standards", and the text of changes and amendments is published in the monthly information index "National Standards". In case of revision (replacement) or cancellation of this standard, the corresponding notice will be published in the monthly information index "National Standards". Relevant information, notices and texts are also posted in information system for public use - on the official website Federal agency on technical regulation and metrology on the Internet
An amendment was made, published in IUS No. 7, 2015
Amendment made by database manufacturer
Introduction
Introduction
The creation of a standard for a method for measuring the density of heat flows passing through building envelopes is based on the requirements of Federal Law N 384-FZ of December 30, 2009. N 384-FZ* "Technical Regulations on the Safety of Buildings and Structures", according to which buildings and structures, on the one hand, must exclude irrational consumption during operation energy resources, and on the other hand, not to create conditions for unacceptable deterioration of the parameters of the human environment and the conditions of production and technological processes.
_______________
* The text of the document corresponds to the original. - Database manufacturer's note.
This standard was developed with the aim of establishing a unified method for measuring, in laboratory and field conditions, the density of heat flows passing through the fences of heated buildings and structures, which makes it possible to quantify the thermal qualities of buildings and structures and the compliance of their enclosing structures with the regulatory requirements specified in the current regulatory documents, to determine the real heat loss through external enclosing structures, check design structural solutions and their implementation in constructed buildings and structures.
The standard is one of the basic standards that provides parameters for the energy passport and energy audit of operated buildings and structures.
1 area of use
This standard establishes a unified method for measuring the density of heat flows passing through single-layer and multi-layer enclosing structures of residential, public, industrial and agricultural buildings and structures during experimental research and under operating conditions.
The standard applies to the enclosing structures of heated buildings, tested under climatic influences in climatic chambers and during full-scale thermal engineering studies under operating conditions.
2 Normative references
This standard uses references to the following standards:
GOST 8.140-2009 State system ensuring uniformity of measurements. State primary standard and state verification scheme for means of measuring thermal conductivity of solids from 0.1 to 5 W/(m K) in the temperature range from 90 to 500 K and from 5 to 20 W/(m K) in the temperature range from 300 to 1100 K
GOST 6651-2009 Resistance thermal converters. Are common technical requirements and test methods
GOST 7076-99 Construction materials and products. Method for determining thermal conductivity and thermal resistance under stationary thermal conditions
GOST 8711-93 Analog indicating electrical measuring devices of direct action and auxiliary parts for them. Part 2. Special requirements for ammeters and voltmeters
GOST 9245-79 Direct current measuring potentiometers. General technical conditions
Note - When using this standard, it is advisable to check the validity of the reference standards using the “National Standards” index compiled as of January 1 of the current year, and according to the corresponding information indexes published in the current year. If the reference standard is replaced (changed), then when using this standard you should be guided by the replacing (changed) standard. If the reference standard is canceled without replacement, then the provision in which a reference is made to it is applied in the part that does not affect this reference.
3 Terms and definitions
In this standard, the following terms with corresponding definitions apply:
3.1 heat flow , W: The amount of heat passing through a structure or medium per unit time.
3.2 heat flux density (surface) , W/m: The amount of heat flow passing through a unit surface area of a structure.
3.3 heat transfer resistance of the enclosing structure , m°C/W: Sum of resistance to heat absorption, thermal resistance of layers, resistance to heat transfer of the enclosing structure.
4 Basic regulations
4.1 Essence of the method
4.1.1 The method for measuring heat flux density is based on measuring the temperature difference on an “additional wall” (plate) installed on the building envelope. This temperature difference, proportional in the direction of the heat flow to its density, is converted into thermoEMF (thermoelectromotive force) by a battery of thermocouples located in the “additional wall” parallel to the heat flow and connected in series according to the generated signal. The “additional wall” (plate) and the thermocouple bank form a heat flow converter.
4.1.2 Heat flux density is measured on the scale of a specialized device ITP-MG 4.03 "Potok", which includes a heat flux converter, or is calculated from the results of thermoEMF measurements on pre-calibrated heat flow converters.
The heat flux density is determined by the formula
where is the heat flux density, W/m;
- conversion coefficient, W/m mV;
- value of thermoelectric signal, mV.
The scheme for measuring heat flux density is shown in Figure 1.
1
- measuring device (DC potentiometer according to GOST 9245);
2
- connecting the measuring device to the heat flow converter;
3
- heat flow converter; 4
- the studied enclosing structure;
- heat flux density, W/m
Figure 1 - Scheme for measuring heat flux density
4.2 Hardware
4.2.1 To measure the density of heat fluxes, the ITP-MG 4.03 "Potok" * device is used.
________________
* See Bibliography section. - Database manufacturer's note.
Specifications device ITP-MG 4.03 "Potok" are given in Appendix A.
4.2.2 During thermal technical tests of enclosing structures, it is allowed to measure the density of heat flows using separately manufactured and calibrated heat flow converters with a thermal resistance of up to 0.005-0.06 m °C/W and instruments that measure thermoEMF generated by the converters.
It is allowed to use a converter whose design is given in GOST 7076.
4.2.3 Heat flow converters according to 4.2.2 must meet the following basic requirements:
materials for the “additional wall” (plate) must retain their physical and mechanical properties at ambient temperatures from 243 to 343 K (from minus 30°C to plus 70°C);
materials should not be wetted or moistened with water in the liquid and vapor phases; the ratio of the sensor diameter to its thickness must be at least 10;
converters must have a security zone located around the thermocouple bank, the linear size of which must be at least 30% of the radius or half the linear size of the converter;
The heat flow converter must be calibrated in organizations that in the prescribed manner received the right to produce these converters;
under the above environmental conditions, the calibration characteristics of the converter must be maintained for at least one year.
4.2.4 Calibration of heat flow converters according to 4.2.2 can be carried out on an installation for determining thermal conductivity in accordance with GOST 7076, in which the heat flow density is calculated based on the results of measuring the temperature difference on reference samples of materials certified in accordance with GOST 8.140 and installed instead of the test samples. The heat flow converter calibration method is given in Appendix B.
4.2.5 The converter is checked at least once a year, as specified in 4.2.3, 4.2.4.
4.2.6 To measure the thermoEMF of the heat flow converter, it is allowed to use a portable potentiometer PP-63 in accordance with GOST 9245, digital voltammeters V7-21, F30 in accordance with GOST 8711 or other thermoEMF meters, the calculated error of which in the area of the measured thermoEMF of the heat flow converter does not exceed 1% and whose input resistance is at least 10 times higher than the internal resistance of the converter.
When performing thermal testing of enclosing structures using separate converters, it is preferable to use automatic recording systems and instruments.
4.3 Preparation for measurement
4.3.1 Measurement of heat flow density is carried out, as a rule, from the inside of the enclosing structures of buildings and structures.
It is allowed to measure the density of heat flows from the outside of enclosing structures if it is impossible to carry them out from the inside (aggressive environment, fluctuations in air parameters) provided that a stable temperature on the surface is maintained. Heat transfer conditions are monitored using a temperature probe and means for measuring heat flux density: when measured for 10 minutes, their readings must be within the measurement error of the instruments.
4.3.2 Surface areas are selected that are specific or characteristic of the entire enclosing structure being tested, depending on the need to measure local or average heat flux density.
The areas selected for measurements on the enclosing structure must have a surface layer of the same material, the same treatment and surface condition, have the same conditions for radiant heat transfer and should not be in close proximity to elements that can change the direction and value of heat flows.
4.3.3 The areas of the surface of the enclosing structures on which the heat flow converter is installed are cleaned until visible and tactile roughness is eliminated.
4.3.4 The transducer is tightly pressed over its entire surface to the enclosing structure and fixed in this position, ensuring constant contact of the heat flow transducer with the surface of the areas under study during all subsequent measurements.
When attaching the converter between it and the enclosing structure, the formation of air gaps is not allowed. To eliminate them, a thin layer of technical petroleum jelly is applied to the surface area at the measurement sites, covering surface irregularities.
The transducer can be fixed along its side surface using a solution of building plaster, technical petroleum jelly, plasticine, a rod with a spring and other means that prevent distortion of the heat flow in the measurement area.
4.3.5 When performing operational measurements of heat flux density, a thin layer of the fencing material on which the converter is mounted is glued onto the loose surface of the converter, or painted over with paint with the same or similar degree of blackness with a difference of 0.1 as that of the material of the surface layer of the enclosing structure.
4.3.6 The measuring device is located at a distance of 5 to 8 m from the measurement site or in an adjacent room to exclude the influence of the observer on the heat flow value.
4.3.7 When using devices for measuring thermoEMF that have restrictions on ambient temperature, they are placed in a room with an air temperature acceptable for the operation of these devices, and heat flow converters are connected to them using extension wires.
When carrying out measurements with the ITP-MG 4.03 "Potok" device, the heat flow converters and the measuring device are located in the same room, regardless of the air temperature in the room.
4.3.8 The equipment according to 4.3.7 is prepared for operation in accordance with the operating instructions for the corresponding device, including taking into account the necessary holding time for the device to establish a new temperature regime in it.
4.4 Taking measurements
4.4.1 Measurement of heat flux density is carried out:
when using the ITP-MG 4.03 "Potok" device after restoring heat exchange conditions in the room near the control sections of the enclosing structures, distorted during preparatory operations, and after restoring directly in the test area the previous heat transfer regime, disturbed when attaching the converters;
during thermal tests using heat flow converters according to 4.2.2 - after the onset of a new steady-state heat exchange under the converter.
After performing the preparatory operations according to 4.3.2-4.3.5 when using the ITP-MG 4.03 "Potok" device, the heat exchange mode at the measurement site is restored in approximately 5-10 minutes, when using heat flow converters according to 4.2.2 - after 2-6 hours .
An indicator of the completion of the transient heat transfer regime and the possibility of measuring the heat flux density can be considered the repeatability of the results of measuring the heat flux density within the established measurement error.
4.4.2 When measuring heat flow in an enclosing structure with a thermal resistance of less than 0.6 (m ° C)/W, simultaneously measure using thermocouples the temperature of its surface at a distance of 100 mm from the converter, below it and the temperature of the internal and external air at a distance 100 mm from the wall.
4.5 Processing of measurement results
4.5.1 When using ITP-MG 4.03 "Potok" devices, the value of heat flux density (W/m) is recorded on the display screen of the electronic unit of the device and is used for thermal engineering calculations or entered into the archive of measured values for subsequent use in analytical studies.
4.5.2 When using separate converters and millivoltmeters to measure thermoEMF, the heat flux density passing through the converter, , W/m, is calculated using formula (1).
4.5.3 Determination of the conversion coefficient taking into account the test temperature is carried out according to Appendix B.
4.5.4 The value of heat flux density, W/m, when measured according to 4.2.2 is calculated using the formula
where is the outside air temperature opposite the converter, °C;
and - surface temperature at the measurement site near the heat flow converter and under it, respectively, °C.
4.5.5 The measurement results according to 4.5.2 are recorded in the form given in Appendix B.
4.5.6 The result of measuring the heat flux density is taken as the arithmetic average of the results of five measurements at one position of the heat flux transducer on the enclosing structure.
Appendix A (for reference). Technical characteristics of the device ITP-MG 4.03 "Potok"
Appendix A
(informative)
Structurally, the heat flow and temperature meter ITP-MG 4.03 "Potok" is made in the form of an electronic unit and modules connected to it via cables, to each of which, in turn, 10 heat flow and/or temperature sensors are connected via cables (see. Figure A.1).
The operating principle underlying the meter is to measure the thermoEMF of contact thermoelectric heat flow converters and the resistance of temperature sensors.
The heat flow converter is a galvanic copper-constantan thermopile consisting of several hundred series-connected thermocouples, folded bifilarly into a spiral, filled with an epoxy compound with various additives. The heat flow transducer has two terminals (one from each end of the sensing element).
The operation of the converter is based on the principles of an “additional wall” (plate). The converter is fixed on the heat transfer surface of the object under study, forming an additional wall. The heat flow passing through the converter creates a temperature gradient in it and a corresponding thermoelectric signal.
Platinum resistance transducers in accordance with GOST 6651 are used as remote temperature sensors in the meter, which provide measurement of surface temperatures by attaching them to the surfaces under study, as well as temperatures of air and granular media by immersion.
1.Measuring limit:
- heat flux density: - 10-999 W/m;
- temperatures - from minus 30°C to 100°C.
2. Limits of permissible basic absolute error in measurement:
- heat flux density: ±6%;
- temperature: ±0.2°С.
3. Limits of permissible additional relative error during measurement:
- heat flux density caused by temperature deviation of heat flux converters from 20°C: ±0.5%;
- temperature caused by temperature deviation of the electronic unit and modules from 20°C: ±0.05°C.
4. Thermal resistance of converters:
- heat flux density no more than 0.005 m °C/W;
- temperatures not more than 0.001 m °C/W.
5. The conversion coefficient of heat flow converters is no more than 50 W/(m mV).
6. Overall dimensions no more than:
- electronic unit 175x90x30 mm;
- module 120x75x35 mm;
- temperature sensors with a diameter of 12 mm and a thickness of 3 mm;
- heat flow converters (rectangular): from 10x10 mm plates, 1 mm thick, to 100x100 mm plates, 3 mm thick;
- heat flow converters (round) from plates with a diameter of 18 mm, a thickness of 0.5 mm to plates with a diameter of 100 mm, a thickness of 3 mm.
7. Weight no more than:
- electronic unit 0.25 kg;
- module with ten converters (with a cable 5 m long) 1.2 kg;
- single temperature transducer (with a cable 5 m long) 0.3 kg;
- single heat flow converter (with a cable 5 m long) 0.3 kg.
Figure A.1 - Diagram of cable connections of heat flow converters and temperature sensors of the ITP-MG 4.03 "Potok" meter
Appendix B (recommended). Heat flow converter calibration method
The manufactured heat flow converter is calibrated in an installation for determining the thermal conductivity of building materials in accordance with GOST 7076, in which, instead of the test sample, a calibrated heat flow converter and a reference material sample in accordance with GOST 8.140 are installed.
When calibrating, the space between the thermostatic plate of the installation and the reference sample outside the converter must be filled with a material similar in thermophysical properties to the material of the converter in order to ensure the one-dimensionality of the heat flow passing through it in the working area of the installation. The thermoEMF measurement on the converter and the reference sample is carried out by one of the instruments listed in 4.2.6.
The conversion coefficient, W/(m mV) at a given average temperature of the experiment is found from the results of measurements of the heat flux density and thermoEMF according to the following relationship
where is the value of the heat flux density in the experiment, W/m;
- calculated value of thermoEMF, mV.
The heat flux density is calculated from the results of measuring the temperature difference on a reference sample using the formula
where is the thermal conductivity of the reference material, W/(m °C);
, - temperature of the upper and lower surfaces of the standard, respectively, °C;
Standard thickness, m.
It is recommended to select the average temperature in experiments when calibrating a heat flow converter in the range from 243 to 373 K (from minus 30°C to plus 100°C) and maintain it with a deviation of no more than ±2°C.
The result of determining the conversion coefficient is taken to be the arithmetic mean of the values calculated from the results of measurements of at least 10 experiments. The number of significant figures in the value of the conversion factor is taken in accordance with the measurement error.
The temperature coefficient of the converter, °C, is found from the results of thermoEMF measurements in calibration experiments at different average temperatures of the converter according to the ratio
where , are the average temperatures of the converter in two experiments, °C;
, - conversion coefficients at average temperature, respectively, and , W/(m mV).
The difference between average temperatures should be at least 40°C.
The result of determining the temperature coefficient of the converter is taken to be the arithmetic mean value of the density, calculated from the results of at least 10 experiments with different average temperatures of the converter. The value of the conversion coefficient of the heat flow converter at test temperature , W/(m mV), is found using the following formula
where is the conversion coefficient found at the calibration temperature, W/(m mV);
- temperature coefficient of change in the calibration coefficient of the heat flow converter, °C;
- difference between the transducer temperatures during measurement and calibration, °C.
Appendix B (recommended). Form for recording the results of measuring heat flows passing through the building envelope
Name of the object on which the measurements are carried out |
||||||||
Type and number of heat flow converter |
||||||||
Conversion factor | ||||||||
at calibration temperature | ||||||||
Converter temperature coefficient | ||||||||
Temperatures of external and internal air, | ||||||||
Temperatures of the surface of the building envelope near |
||||||||
converter and below it | ||||||||
Conversion coefficient value at temperature |
||||||||
tests | ||||||||
Type and number of measuring device | ||||||||
Table B.1
Type of enclosing structure | Plot number | Device readings, mV | Heat flux density value |
||||||
Measurement number | Average for the area | scaled | valid |
||||||
Operator signature | ||||
Date of measurements | ||||
Bibliography
State Register of Measuring Instruments of the Russian Federation*. All-Russian Research Institute of Metrology and Standardization. M., 2010
________________
* The document is not provided. Behind additional information refer to the link. - Database manufacturer's note.
UDC 669.8.001.4:006.354 MKS 91.040.01
Key words: heat transfer, heat flow, heat transfer resistance, thermal resistance, thermoelectric heat flow converter, thermocouple
_________________________________________________________________________________________
Electronic document text
prepared by Kodeks JSC and verified against:
official publication
M.: Standartinform, 2015
The amount of heat passing through a given surface per unit time is called heat flux Q, Tue.
The amount of heat through a unit surface area per unit time is called heat flux density or specific heat flow and characterizes the intensity of heat transfer.
Heat flux density q, is directed normal to the isothermal surface in the direction opposite to the temperature gradient, i.e., in the direction of decreasing temperature.
If the distribution is known q on the surface F, then the total amount of heat Qτ passed through this surface in time τ , found by the equation:
and heat flow:
If the value q is constant over the surface under consideration, then:
Fourier's law
This law sets the amount of heat flow when heat is transferred by conduction. French scientist J.B. Fourier in 1807 he established that the heat flux density through an isothermal surface is proportional to the temperature gradient:
The minus sign in (9.6) indicates that the heat flow is directed in the direction opposite to the temperature gradient (see Fig. 9.1.).
Heat flux density in any direction l represents the projection onto this direction of heat flow in the normal direction:
Coefficient of thermal conductivity
Coefficient λ , W/(m·K), in the equation of Fourier's law is numerically equal to the heat flux density when the temperature drops by one Kelvin (degree) per unit length. The thermal conductivity coefficient of various substances depends on their physical properties. For a certain body, the value of the thermal conductivity coefficient depends on the structure of the body, its volumetric weight, humidity, chemical composition, pressure, temperature. In technical calculations the value λ taken from reference tables, and it is necessary to ensure that the conditions for which the value of the thermal conductivity coefficient is given in the table correspond to the conditions of the calculated problem.
The coefficient of thermal conductivity depends especially strongly on temperature. For most materials, as experience shows, this dependence can be expressed by a linear formula:
Where λ o - thermal conductivity coefficient at 0 °C;
β - temperature coefficient.
Thermal conductivity coefficient of gases, and especially vapor, is highly dependent on pressure. The numerical value of the thermal conductivity coefficient for various substances varies within a very wide range - from 425 W/(m K) for silver to values of the order of 0.01 W/(m K) for gases. This is explained by the fact that the mechanism of heat transfer by thermal conductivity in various physical environments different.
Metals have highest value thermal conductivity coefficient. The thermal conductivity of metals decreases with increasing temperature and decreases sharply in the presence of impurities and alloying elements. Thus, the thermal conductivity of pure copper is 390 W/(m K), and that of copper with traces of arsenic is 140 W/(m K). The thermal conductivity of pure iron is 70 W/(m K), steel with 0.5% carbon is 50 W/(m K), alloy steel with 18% chromium and 9% nickel is only 16 W/(m K).
The dependence of the thermal conductivity of some metals on temperature is shown in Fig. 9.2.
Gases have low thermal conductivity (about 0.01...1 W/(m K)), which increases greatly with increasing temperature.
The thermal conductivity of liquids deteriorates with increasing temperature. The exception is water and glycerol. In general, the thermal conductivity coefficient of droplet liquids (water, oil, glycerin) is higher than that of gases, but lower than that of solids and ranges from 0.1 to 0.7 W/(m K).
Rice. 9.2. The influence of temperature on the thermal conductivity of metals
BUILDING REGULATIONS
BRIDGES AND PIPES.
SURVEY RULES
AND TESTS
SNiP 3.06.07-86
STATE CONSTRUCTION COMMITTEE OF THE USSR
Moscow 1987
DEVELOPED by Soyuzdorni Ministry of Transport (engineers V.V. Vasiliev - topic leader, P.V. Rutgars, E.A. Tenyaev, I.L. Katzman) and TsNIIS Ministry of Transport (candidates of technical sciences V.P. Polevko- topic leader, I.I. Kazei, P.M. Zelevich; Eng. V.P. Boychun) with the participation of NIImostov LIIZhT Ministry of Railways, Giprodornia of the Ministry of Road Transport of the RSFSR and Giprokommundortrans of the Ministry of Housing and Communal Services of the RSFSR.
INTRODUCED by the Ministry of Transport.
PREPARED FOR APPROVAL by the Department of Standardization and Technical Standards in Construction of the USSR State Construction Committee ( IN AND. Chuev, M.M. Borisova).
With the entry into force of SNiP 3.06.07-86 “Bridges and pipes. Rules for Inspections and Tests" from July 1, 1987. "Instructions for inspection and testing of bridges and pipes" (VSN 122-65), approved by the Ministry of Transport, the Ministry of Railways, the Ministry of Road Transport of the RSFSR and the Ministry of Economic Affairs of the RSFSR, is not applied.
When using a regulatory document, one should take into account the approved changes to building codes and regulations and state standards published in the journal “Bulletin of Construction Equipment”, “Collection of Amendments to building regulations and rules" of the USSR State Construction Committee and information index " State standards USSR" State Standard of the USSR.
These norms and rules apply to inspections, static and dynamic tests and running-in of bridges (overpasses, viaducts, overpasses) and pipes under embankments, designed for moving live loads and located on railways, metro and tram lines, highways(including roads of industrial enterprises, as well as on-farm roads in collective farms, state farms and other agricultural enterprises and organizations), on the streets and roads of cities, towns and rural settlements. The norms and rules apply to inspections and tests carried out after completion of construction (when accepting structures for permanent or temporary operation), after reconstruction (strengthening) and can be used for inspections and tests of structures in operation, as well as for inspections of bridges designed for special types loads (from pipelines, channels, etc.).
The rules and regulations do not apply to:
to incomplete surveys conducted by design, research and other organizations to obtain limited data;
for research tests carried out before the destruction of structures;
for control inspections and tests of structures, components and parts performed during their manufacture and installation.
1. GENERAL PROVISIONS
1.1. Surveys and tests of bridges and pipes are carried out to determine the condition and study the operation of these structures.
Inspections of bridges and pipes can be carried out as an independent type of work (without testing).
Testing and running-in of structures may be carried out only after inspections have been completed (see) and taking into account the data obtained from them.
2. Removal of samples of materials can only be carried out from minor and non-stressed parts and elements of the structure. Places in the structure where samples were removed must be sealed (covered) and, if necessary, reinforced.
2.4. When inspecting bridges and pipes, the system of notation and counting of structure elements adopted in the technical documentation should be used. This system should be used in both field and survey reporting documents.
2.5. When inspecting bridges and pipes, faults (defects, defects, damage) found in structures should be noted and assessed according to their significance.
Typical defects and damage found in various designs bridges and pipes, indicating the most likely causes of their origin are given in the recommended.
Familiarization with TECHNICAL DOCUMENTATION
2.6. When performing inspections and tests, the degree of detail in reviewing technical documentation in relation to specific objects is determined by the bridge station work manager based on the tasks set in the work program.
The provision of the necessary technical documentation for review is carried out during inspections and tests:
structures completed by the general construction contractor or, on his behalf, by the construction organization that carried out the construction;
operated structures - by the organization in charge of the structure.
2.7. When familiarizing yourself with technical documentation completed construction of structures, as a rule, you should pay attention to:
on the correctness of execution of deviations from the approved project and current regulatory documents;
for compliance with physical, mechanical and chemical characteristics used building materials to the requirements of the project and regulatory documents;
for the availability and quality of registration of intermediate acceptance of individual structures (for example, beams of prefabricated spans, support blocks, etc.), as well as critical hidden work performed on site.
2.8. Familiarization with the technical documentation of operated bridges and pipes also includes the study of materials and data from previously verified surveys and tests. In this case, it should be determined to what extent previously issued recommendations for maintaining the structure in good condition have been implemented.
In addition, materials related to the performance of routine maintenance (including troubleshooting), repairs, and long-term observations should be studied.
INSPECTION OF STRUCTURES
2.9. When inspecting a structure, the main attention should be paid to identifying faults in its parts and elements (for example, cracks, chips, bents and bulgings, disorders in butt joints and attachments of elements, corrosion damage, destruction of slopes of cones, flow guides and bank protection dams, damage to drainage, waterproofing, deformation seams, equalizers and other elements of the bridge deck or superstructure). It is also necessary to note in the structures places where, due to the inevitable accumulation of dirt, water, snow, ice, intensive development of various unfavorable phenomena (corrosion processes, wood rotting, defrosting, etc.) is possible.
2.10. When inspecting bridges and pipes located in areas of permafrost, as well as in mudflow and seismic areas, it is necessary to pay attention to the condition and operation of existing protective devices and structures.
2.11. Detected malfunctions must be described with the necessary completeness in the examination materials, indicating the time of detection and possible causes of occurrence.
The most dangerous, as well as characteristic damages and defects must be reflected in sketches or photographed.
CONTROL MEASUREMENTS AND INSTRUMENTAL SURVEYS
2.12. Control checks the general dimensions of the structure and the dimensions of transverse settlements, joints and attachments are carried out to assess the compliance of the actual geometric characteristics of the structure (taking into account the established tolerances) with the characteristics specified in the design, as-built or operational technical documentation.
The type and required volume of control measurements taken are determined by the bridge station work manager after reviewing the technical documentation and inspecting the structure.
(ST SEV 2859-81)
APPENDIX 3
Document text
Building regulations
SNiP 3.06.07-86
"Bridges and pipes. Rules for inspection and testing"
(approved by Decree of the USSR State Construction Committee dated December 31, 1986 N 77)
performing work on inspection and testing of bridges and
pipes (required)
requirements which should be followed when
quality control of materials (reference)
various designs of bridges and pipes, and methods for their
damage identified during the examination
rules, departmental regulations, which
should be used when performing survey work
and testing of bridges and pipes (informative)
These norms and rules apply to inspections, static and dynamic tests and running-in of bridges (overpasses, viaducts, overpasses) and pipes under embankments, designed for moving temporary loads and located on railways, metro and tram lines, roads (including roads industrial enterprises, as well as on-farm roads in collective farms, state farms and other agricultural enterprises and organizations), on the streets and roads of cities, towns and rural settlements. The norms and rules apply to inspections and tests carried out after completion of construction (when accepting structures for permanent or temporary operation), after reconstruction (strengthening) and can be used for inspections and tests of structures in operation, as well as for inspections of bridges designed for special types of loads (from pipelines, channels, etc.).
The rules and regulations do not apply to:
to incomplete surveys conducted by design, research and other organizations to obtain limited data;
for research tests carried out before the destruction of structures;
for control inspections and tests of structures, components and parts performed during their manufacture and installation.
When carrying out work to inspect completed and reconstructed bridges and pipes, it is also necessary to be guided by the requirements of SNiP III-43-75 and SNiP 2.05.03-84.
Notes: 1. When carrying out quality control of materials using non-destructive methods, as well as when removing samples of materials for laboratory research, it is necessary to be guided by the requirements and instructions of the current state standards given in the reference
2. Removal of samples of materials can be carried out only from minor and non-stressed parts and elements of the structure. Places in the structure where samples were removed must be sealed (covered) and, if necessary, reinforced.
2.4. When inspecting bridges and pipes, the system of notation and counting of structure elements adopted in the technical documentation should be used. This system should be used in both field and survey reporting documents.
2.5. When inspecting bridges and pipes, faults (defects, defects, damage) found in structures should be noted and assessed according to their significance.
Typical defects and damage found in various structures of bridges and pipes, indicating the most likely causes of their origin, are given in the recommended
3.12. The first loading of the structure with a test load should be carried out gradually, with control over its operation. different stages according to the readings of individual measuring instruments.
3.13. The holding time of the test load in each of the provided positions should be determined by stabilization of the readings of the measuring instruments: the increments of the observed deformations over 5 minutes should not exceed 5%.
In order to increase the accuracy of instrument readings, the time for loading and unloading structures, as well as the time for taking readings from instruments, should be as short as possible.
If it is necessary to achieve the greatest deformations of the structure under load, the holding time should be assigned depending on the observed increase in deformations, the material of the structure, the type and condition of the butt joints, and previous loads.
Determination of residual deformations of a structure should be made based on the results of its first loading with a test load.
3.14. Loading of structures with a test load should, as a rule, be repeated. The number of required repeated loadings is determined by the bridge station work manager based on the results of the first loadings.
3.15. During static testing, the following should be measured:
general movements and deformations of the structure and its parts;
stresses (relative deformations) in sections of elements;
local deformations (opening of cracks and seams, displacements in joints, etc.).
In addition, depending on the type of structures and their condition and in accordance with the test objectives, measurements of angular deformations, mutual movements of parts of the structure, forces in elements (cables, trusses), etc. can be made.
3.16. The installation locations of measuring instruments should be assigned based on the need to obtain, as a result of testing, a sufficiently complete understanding of the operation of the structure under temporary vertical loads.
To measure displacements and deformations, you should select elements and parts of structures that work most intensively under the influence of load, as well as elements and connections that need to be verified based on survey results or other data.
3.21. When testing road and city bridges in necessary cases (for example, to identify the dynamic characteristics of a structure, to assess the influence of irregularities possible on the roadway, etc.), the dynamic effect of a moving load can be enhanced by the use of special measures - driving vehicles over artificially created irregularities (sills) ).
Disturbing dynamic forces in the form of periodically repeating impulses can be created by driving a two-axle car along thresholds (boards laid across the driveway), separated from one another at distances equal to the wheelbase of the car.
3.22. When dynamically testing a structure with a temporary moving load, the runs should be performed at different speeds, which makes it possible to identify the nature of the structure’s operation in the range of possible speeds of the load.
The load movement speeds during runs, as well as the number of runs at one speed or another in each specific case are set by the bridge station work manager. It is recommended to perform at least 10 runs at different speeds and repeat individual runs at which an increased dynamic impact of the load is observed.
3.23. During dynamic tests, the general movements of the structure (for example, deflections in the middle of the span, displacements of the ends of the span on movable supporting parts), as well as, if necessary, movements and deformations (stresses) in individual elements of the structure should be recorded using recording instruments.
4.5. Based on the materials of the surveys and tests carried out, as well as based on the results of assessing the design load-carrying capacity of the structure, in each case measures must be developed to ensure the normal and safe operation of the structure.
Depending on the nature, significance and distribution of detected defects and damage, it may be necessary to carry out various types repair work, strengthening of individual elements, introducing restrictions for circulating loads (including reducing the number of rows or increasing the intervals between transport units on road and city bridges), limiting the speed of vehicles, etc.
Conclusions based on the results of inspections and tests of newly built or reconstructed structures are drawn up by bridge stations if it is necessary to transfer the received data to acceptance commissions in a short time. In addition, conclusions can be drawn up by bridge stations based on the results of local work (for example, on inspections and tests of one or more individual elements of the structure).
Reports on surveys and tests with conclusions and proposals are compiled by bridge stations after complete processing and analysis of all received materials and data.
5.2. Documents based on the results of examinations and tests must contain:
a) acts and conclusions:
a brief description of the object being examined and tested;
list of completed works;
main results of the work and their brief analysis;
conclusions about the possibility of passing loads on the structure;
b) reports:
description of the structures of the structure and the necessary information from the design and other technical documentation for the structure, used to justify the conclusions of the bridge station;
a brief description of the construction technology indicating the existing deviations, as well as defects that arose during the construction stage;
results of control measurements and instrumental surveys;
the results of the inspection of the structure, indicating the condition of its individual parts and a description of the detected defects and damage; if there are a large number of defects and damages, a list of them is compiled;
bridge test results (including comparison of experimental data with data obtained by calculation);
conclusions about the condition of the structure and the compliance of its operation with the design prerequisites;
conditions for further operation of the structure.
If it is necessary to conduct repeated examinations and tests (including to study the operation of a structure after a certain period of operation) or long-term observations, appropriate proposals should be made in the conclusions.
5.3. The report must include drawings, diagrams, photographs and other illustrative materials. Auxiliary materials, calculation tables, etc. should be given in appendices.
It is also recommended to include in the appendices to the report: test program, extracts from design, construction and operational documentation, results of verification calculations, reports and materials on work performed with the involvement of specialized organizations, etc.
──────────────────────────────
Mandatory
Occupational Health and Safety Regulations
when performing survey work and
testing of bridges and pipes
1. Workers who have undergone training, knowledge testing, and labor safety briefings in accordance with the requirements of SNiP III-4-80 (section 1) and GOST 12.0.004-79 are allowed to carry out work on the inspection and testing of bridges and pipes.
Information
List of basic state standards,
requirements which should be followed when
quality control of materials
Typical defects and damage found in
various designs of bridges and pipes, and ways to identify them
Information
List of state standards, building codes and regulations,
departmental regulations that should be used
when performing work on inspection and testing of bridges and pipes
GOST 23457-79. Technical means traffic organization. Rules of application.
GOST 10807-78. Road signs. General technical conditions.
GOST 13508-74. Road markings.
SNiP 2.05.03-84. Bridges and pipes.
SNiP III-43-75. Bridges and pipes. Rules for production and acceptance of work. Instructions for the maintenance of artificial structures (TsP/4363), approved by the Main Directorate of Tracks and Structures of the Ministry of Railways in 1986.
See SNiP 3.06.04-91. "Bridges and pipes", approved by Decree of the USSR State Construction Committee dated November 28, 1991 N17
Technical rules for the repair and maintenance of highways (VSN 24-75), approved by the Ministry of Road Transport of the RSFSR in 1975.
Instead of VSN 24-75, VSN 24-88, approved by the Ministry of Road Transport of the RSFSR on June 29, 1988, is in force.
Instructions for carrying out inspections of bridges and pipes on highways (VSN 4-81), approved by the Ministry of Roads of the RSFSR in 1981.
Guidelines for determining the load-carrying capacity of metal spans of railway bridges, approved by the Main Directorate of Tracks and Facilities of the Ministry of Railways in 1985.
Guidelines for determining the load-carrying capacity of reinforced concrete superstructures of railway bridges, approved by the Main Directorate of Tracks and Facilities of the Ministry of Railways in 1974.
Instructions for determining the load-carrying capacity of reinforced concrete beam superstructures of road bridges (VSN 32-78), approved by the Ministry of Road Transport of the RSFSR in 1978.
Instructions for organizing and ensuring traffic safety on highways (VSN 25-76), approved by the Ministry of Roads of the RSFSR in 1976.
Instructions for hydrological observations at bridge crossings, approved by the Main Directorate of Tracks and Facilities of the Ministry of Railways in 1979.
Traffic rules approved by the USSR Ministry of Internal Affairs in 1986.
Currently, the Traffic Rules of the Russian Federation are in force, approved by Resolution of the Council of Ministers of the Russian Federation dated October 23, 1993 N 1090
