GB/T 38588-2020 in English

《GB/T 38588-2020城镇供热保温管网系统散热损失现场检测方法》由TC455（全国城镇供热标准化技术委员会）归口，主管部门为住房和城乡建设部。

In-situ measurements of heat loss of insulating pipes for urban heat-supplying

1 Scope

This standard specifies the terms, definitions and symbols, test methods, test grading and use conditions, test requirements, data processing, test errors and test reports of in-situ measurements of heat loss of insulating pipes for urban heat-supplying.

This standard is applicable to the in-situ measurement of heat loss of insulating pipes, pipe interfaces and their fittings (hereinafter referred to as pipelines) for urban heat-supplying with the hot water medium temperature less than or equal to 150 °C and the steam medium temperature less than or equal to 350 °C.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 10295 Thermal insulation - Determination of steady-state thermal resistance and related properties - Heat flow meter apparatus
GB/T 17357 In-situ measurements of heat loss through thermal insulation of equipments and pipes - Heat flow meter apparatus and surface temperature method
JJF 1059.1-2012 Evaluation and expression of uncertainty in measurement

3 Terms, definitions and symbols

3.1 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

3.1.1
steady heat transfer
heat transfer process in which the radial temperature at each point does not change with time in the thermal insulation structure layer of thermal insulation pipeline

3.1.2
heat flow meter apparatus method
heat flux test method for directly measuring radial heat transfer of insulation construction of thermal insulation pipeline with thermal resistance type heat flux sensor (heat flux probe) and measurement indicator

3.1.3
surface temperature method
heat flux test method for calculating radial heat transfer by measuring the outer surface temperature, ambient temperature, wind direction and speed, surface thermal emissivity and external dimensions of insulation construction

3.1.4
temperature difference method
heat flux test method for calculating radial heat transfer of insulation construction by measuring the material thickness of each layer of insulation construction, the temperature on the interface of each layer and the thermal conductivity of each layer of materials at the service temperature

3.1.5
heat balance method
method for calculating the whole heat loss value of the pipeline according to the enthalpy difference method or the principle of energy balance by in-situ measurement of the medium flow of the pipeline under test, the medium temperature and (or) pressure at the starting point and the end point of the pipeline under the stable operation state of pipe network system

3.1.6
pseudo steady state of transducer
heat transfer state when the difference of average reading of the heat flux sensor is not greater than 2% and the difference of average reading of the temperature sensor at the same measuring point is not greater than 0.2 °C in two consecutive 5-minute cycles

3.1.7
heat flux
heat passing through a unit cross-sectional area of an object per unit time

3.1.8
insulation construction
generic term of insulating layer and protective cover

3.1.9
ground temperature
natural temperature of soil at the same depth as the tested insulation construction, which is greater than or equal to 10 m away from the laying site of the tested insulation construction
 
3.2 Symbols

For the purposes of this document, the following symbols apply.

a1—the temperature factor, K3;

CA—the calculation coefficient of approximate value of overall heat transfer coefficient for the outer surface of horizontal pipeline;

CB—the calculation coefficient of approximate value of overall heat transfer coefficient for the outer surface of vertical pipeline;

Cr—the radiation coefficient of material surface, W/(m2·K4);

Foreword i
1 Scope
2 Normative references
3 Terms, definitions and symbols
3.1 Terms and definitions
3.2 Symbols
4 Test methods
4.1 Heat flow meter apparatus method
4.2 Surface temperature method
4.3 Temperature difference method
4.4 Heat balance method
5 Test grading and service conditions
5.1 Test grading and selection
5.2 Test apparatus
6 Test requirements
6.1 Test preparation
6.2 Layout of test sections and measuring points
6.3 Environmental conditions for test
6.4 Test procedures
7 Data processing
7.1 Data collation
7.2 Calculation of heat loss
8 Test error
8.1 Error analysis
8.2 Error range
9 Test report
Annex A (Normative) Heat flux correction
Annex B (Normative) Calculation of the overall heat transfer coefficient by surface temperature method
Annex C (Normative) Investigation form of condition along the thermal insulation pipeline
Annex D (Normative) Test data record form for heat loss of insulation construction of thermal insulation pipeline