SU932291A1 - Method of determination of heater heat losses in connecting wires - Google Patents

Description

(5) METHOD FOR DETERMINING HEAT LEAKAGE OF HEATER UNDER CONDUCTING WIRES

The invention relates to the field of measuring the amount of heat, and specifically to a method for determining the heat leaks of a heater caused by heat conduction of supply wires, and can be used for precision measurements of thermal parameters.

Methods are known for detecting uncontrolled heat leaks by radiation in the supply wires 1,

The disadvantage of these methods is that they detect heat leaks by radiation, and this does not take into account heat leaks by heat conduction and the convention in the supply wires.

Closest to n | The proposed method is a method for determining the heat leaks of the heater through the lead wires by means of a differential thermocouple, which consists in determining the temperature gradient in the lead wires and calculating the heat leakage using an analytical dependence 23.

The disadvantage of this method of determining heat leaks caused by thermal conductivity is that, depending on the type

"T

where X 1 thermal conductivity coefficient

wires;

t is the distance between the points of the wire at which it is measured

10 temperature gradient; S - wire section; LT is the measured temperature gradient,

substitute the calculated geometric

15, the size and the expected temperature gradient in the supply wire, which reduces the accuracy of the determination of uncontrolled heat loss.

The purpose of the invention is to improve the accuracy of measuring uncontrolled heat leaks.

This goal is achieved by the fact that the method additionally passes 3932291

electric current of different polarity along the supply wires of the heater is measured, the magnitude of the current and voltage in each supply wire in the area between the spacings of the differential thermocouple is measured, and the heat leakage is calculated using the formula | -ii-P where., is the heat conduction coefficient of the supply wires; Р is the coefficient of specific resistance of the supply tubes & and - voltage drop in the forward conductor in the area between the thermocouples of the differential thermocouple at positive polarity of the electric current; and - voltage drop in the conductor in section M between differential thermocouple springs with negative electric polarity. current; I - positive current electric current; negative electric current; о - coefficient of thermo-emf of a differential thermocouple. The drawing shows a diagram of the device. The device contains an electric heater, the supply wires of one l-section, of which 2 and 3 are copper current, and 1 and - constants | e potential lead wires 1 - are connected to the voltmeter and to the power supply circuit via the supply wire switch 5 contains a current network polarity switch 6, a sample resistance coil 7, potential taps of which are connected to a voltmeter, a power supply 8, a resistance store 9, thermocouple wires A, B, C, D. The method is as follows. The electric current of different polarity across the supply wires of the electric heater in the stationary mode of operation of the device measures the electrical current drop in voltage in each supply wire in the section between the thermocouple spacings and determines the temperature gradient in each supply wire using

Claims (2)

 / U- / C The purpose of reducing errors from the inaccuracy of measuring the geometrical dimensions of the supply wires in the area between the spacings of the differential thermocouple is that the ratio S / P is expressed in terms of the ratio P / R, i.e. c / P / GMC- / R U-f where R is the resistance of the section of supply wire in which the temperature gradient is measured. But since W A T, then substituting the obtained expressions, we obtain the formula H x Ilu HuilDrkirn OS and, Thus, using the proposed method for determining heat leakage improves the accuracy of determining uncontrolled heat leakage in supply wires due to the fact that The obtained values — electric current and voltage drop in the area between the thermocouple spacings can be measured with great precision by a precision voltmeter. Substituting the table thermodynamic constants and accurately measured values of electric current and voltage drop in the area between the slots of the differential thermocouple into the resulting thermal conductivity formula and determining the heat leakage in each supply wire with great accuracy. Using the power source 8 and the resistance store 9, the thermal power of the calorimeter electric heater is exposed and measured by the method of four wires of the voltage drop on the supply wires 1 and the current flowing through the supply wires 2 and 3 through the Resistance exemplary coil 7, which potential leads connected to a voltmeter. The electrically passed, the current of different polarity with the help of the current polarity switch 6, for example, over copper supply wires 2 and 3, measure the voltage drop on the electric heater of the device by supplying constantan wires and k. The voltage drop at a different current polarity in the copper lead wire 2 is measured by the differential thermocouple 1, C. The voltage drop is not at different polarity of the current in the copper lead wire 3 measurements by the differential thermocouple k, D. I substitute the obtained values Mula, heat leakages in the copper supply wires 2 and 3 are found. Switch 5e passes electric current of different polarity with the help of switch 6 polarity current through constantan supply cables n k, measure the voltage drop of copper The supply wires 2 and 3 "The voltage drop at different polarities of the current in the constantan under the lead wire 1 is measured by a differential thermocouple 2, A. The drop in the voltage at different polarities of the current in the constantan ground wire k is measured by the differential thermocouple 3 V. Substituting the values obtained in the formula, find heat leakage by thermal conductivity in constantan supply wires 1 and t. In sum, the heat leaks found by thermal conductivity in each supply wire 1- receive complete heat leaks. The proposed method for determining heat leaks in the supply wires by thermal conductivity allows to improve the accuracy of precision measurements of thermal parameters taking into account heat leaks by 3-5%. Claims The method of determining heat leaks of a heater through a wire through a differential thermo-thermop 9 9 ry consists in determining a temperature gradient in the supply wires and calculating heat leaks by analytic dependence, in addition, in order to improve the accuracy of measuring uncontrolled heat leaks, Pass electric current of different polarity through the supply wires of the heater, measure the current / voltage of the current and voltage in each supply wire in the area between the spans and a differential thermocouple, and the heat leakage is calculated by the formula. ; p lu i-lu- | uithiriJTToG iu hiuH where X is the thermal conductivity of the supply wires; resistivity coefficient of supply wires; voltage drop in the supply wire in the area between the thermocouple spans with a positive polarity of the electric current; voltage drop in the supply wire in the area between the thermocouple spacings with a negative polarity of the electric current; electric current of positive polarity; negative electric current; thermo-emf coefficient of a differential thermocouple. Sources of information taken into account during the examination 1. USSR author's certificate No. 555296, cl. G 01 K 17/00, 1976. 2. Journal of Physical Chemistry, 197, t. KS, V E. p. 2377-2379 (prototype).