RU2063006C1 - Heat release measurement technique - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: prior to installing heat meter with differential thermocouple junctions at source and drain on equipment under test, heat flux of same order of magnitude as heat release of equipment is passed through this heat meter, temperature of the latter between source and drain is measured before and after its installation on equipment, and potential difference across differential thermocouple junctions heated by equipment is determined. Desired heat release is calculated by using equation given in description of invention including thermal and physical properties of heat meter material and temperature coefficient of thermal emf of thermocouple at measured temperatures. EFFECT: improved measurement accuracy. 1 dwg

Description

 The invention relates to the measurement of heat and can be used to measure heat in the details of the combustion chambers (COP) of thermal machines.

 A known method of determining the amount of heat at which the test object is brought into contact with a heat meter having junctions of a differential thermocouple at the source and drain, measures the temperature gradient in the heat meter between the source and drain, and the desired value is calculated. The source temperature of the heat meter is kept constant by changing the temperature of its drain (1).

 The disadvantage of this method is that it can be used only at a specific temperature of the test object. When expanding the temperature range of measurements of test objects, the thermophysical properties of the heat meter and the thermoelectric properties of the differential thermocouple change, which introduces an error in the measurement of the temperature gradient and reduces accuracy.

The closest to the invention in terms of technical nature and the technical result achieved is a method for determining heat release, which consists in installing a heat meter in the form of a planar differential thermocouple on the test object and measuring the potential difference E _and between its junctions and temperature t _and . When determining the amount of heat, a correction is made to the calculation formula that takes into account the temperature dependence of the thermal conductivity of the heat meter material.

 The disadvantage of this method is the low accuracy when expanding the temperature range of the test objects, due to a change in the thermoelectric properties of the differential thermocouple.

 The technical result obtained from the use of the claimed method consists in increasing the accuracy of determining the heat emission of objects operating at elevated temperatures.

Said result is achieved by that in the known method, prior to installation on the object passed through the calorimeter heat flow q _r of the same order with heat q object and measure heat flow meter temperature t _m between source and drain, and the required heat is calculated by the relation:
q = K • λ _and / λ _t • [1 + α (t _t -t _u )] • e _and / e _t • E _and ,
where K is the coefficient of proportionality;
λ _and is the coefficient of thermal conductivity of the heat meter in contact with the test object;
λ _t - thermal conductivity coefficient of the heat meter before contacting with the used object;
α is the average temperature coefficient of linear expansion of the heat meter material;
e _r differential thermo emf of the thermocouple at temperature _T t;
e _and , differential thermo-emf of thermocouple at temperature t _and .

 The drawing shows a diagram of a device that implements a method for determining the amount of heat.

 The device comprises a heat meter 1 with junctions 2 of a differential thermocouple 3 at source I and drain C connected to a potential difference measuring device 4. Between the source and the drain C of the heat meter, a temperature converter 5 is connected to the temperature measuring device 6. The heat meter 1 is installed on the test object 7.

 The essence of the method for determining heat dissipation is as follows.

Испытуемый объект 7 приводят в контакт с тепломером 1, измеряют разность потенциалов Е_и между спаями 2 дифференциальной термопары 4 на истоке И и стоке C прибором 4 и температуру t_и тепломера 1 между истоком И и стоком С преобразователем температуры 5 и прибором 6, и вычисляют тепловыделение по соотношению:
q=K•λ_и/λ_т•[1+α(t_т-t_и)]•e_и/e_т•E_и (1)
Пример. Предложенным способом определялось тепловыделение в головку цилиндров двигателя внутреннего сгорания.Before contacting with the object 7 through the heat meter 1 using a calorimeter with compensating insulation pass heat flux q _{t of the} same order as the heat of the object, providing preliminary heating of the heat meter to a certain temperature t in the range t _st <t <t _it , where t _it and t _article respectively the temperature of the source and drain of the heat meter when heated by a heat flow q _t The potential difference E _t between them is measured by the device 4 and the temperature t _{t of the} heat meter 1 between the source and the drain With the temperature converter 5 and the device 6, and the proportionality coefficient is calculated by the formula:

The test object 7 is brought into contact with the heat meter 1 measuring the potential difference E _between junctions 2 differential thermocouple 4 on the source of the AND and stock C unit 4 and the temperature t _{and the} heat meter 1 between the source and-drain C temperature transducer 5 and the device 6, and the calculated heat dissipation in the ratio:
q = K • λ _and / λ _t • [1 + α (t _t -t _u )] • e _and / e _t • E _and (1)
Example. The proposed method determined the heat release into the cylinder head of the internal combustion engine.

 The used heat meter is a flattened differential thermocouple with an intermediate electrode made of costantan.

 Copper current collector plates were deposited onto the intermediate electrode by the galvanic method.

Prior to contacting the cylinder head through a heat flux calorimeter passed q _t = 200 • March ¹⁰ W / m ^2. The potential difference between the junctions of the differential thermocouple at the source and drain of the heat meter was E _t 392 μV, and the temperature of the heat meter between the source and drain t _t = 150 ^o C.

При контактировании головки цилиндров двигателя внутреннего сгорания с тепломером разность потенциалов между спаями дифференциальной термопары на истоке и стоке не изменилась Е_иE_т 392 мкВ, а температура тепломера между истоком и стоном повысилась до t_и 350^oС.The proportionality coefficient of the heat meter is equal to:

When the cylinder head of the internal combustion engine was in contact with the heat meter, the potential difference between the junctions of the differential thermocouple at the source and drain did not change E _and E _t 392 μV, and the temperature of the heat meter between the source and groan increased to t _and 350 ^o C.

For the temperatures of the heat meter before contacting t _t and when contacting t _and with the cylinder head, the thermal conductivity coefficients and the differential thermo-emf of the thermocouple were determined.

Coefficients of thermal conductivity of the heat meter λ _t = 23 W / (m • ^° C) at a temperature of T _t 150 ^o C; λ _and = 31.25 W / (m • ^° C) at a temperature of T _and 350 ^o C.

Differential Thermo-EMF Thermocouple
e _t 50.1 μV / ^o C at a temperature t _t 150 ^o C
e _and 60.1 μV / ^o С at t _and 350 ^o C. The average temperature coefficient of linear expansion of the costanan is α = 15.6 • 10 ^{-6 °} C ^-1 (in the temperature range 20-400 ^o С).

Точность определения тепловыделения при исследовании тепловыделений в головку цилиндров двигателя внутреннего сгорания в интервале температур от 150 до 350^oС повысилась и составила

Sought heat

The accuracy of determining heat during the study of heat in the cylinder head of an internal combustion engine in the temperature range from 150 to 350 ^o With increased and amounted to

Claims (1)

A method for determining heat release, which consists in installing a heat meter on the test object with junctions of a differential thermocouple at the source and drain and measuring the potential difference E _and and temperature t _{and the} heat meter between the source and the sink, characterized in that a heat flow q _{t is} passed through the heat meter before installation of the same order with the heat release q of the object and measure the temperature t _{t of the} heat meter between the source and drain, and the desired heat release is calculated by the ratio
q = K • λ _and / λ _t [1 + α • (t _t -t _and ] • e _and / e _t • E _and ,
where K is the coefficient of proportionality;
λ _{and the} coefficient of thermal conductivity of the heat meter in contact with the test object;
λ _{t is the} coefficient of thermal conductivity of the heat meter before contacting with the test object;
α average temperature coefficient of linear expansion of the heat meter material;
e _t differential thermo-EMF thermocouple at a temperature t _t ;
e _and differential thermo-EMF thermocouples at temperature t _and .