SU1758452A1 - Method of determining heat losses via calorimeter wires - Google Patents

Abstract

The invention can be used in thermophysics, heat and power engineering and calorimetry and allows to increase the accuracy of measurement of thermophysical parameters. To do this, in a method involving passing a direct electric current through the calibration element and measuring the joule power allocated to it during stationary operation of the device, followed by calculating the heat leakage using analytical dependence, introduces new operations, namely The sensitivity and signals of the calorimeter are measured at different wire diameters and a constant joule power released at the calibration element, each measurement being carried out with a set of uniform wires of the same They determine the sensitivity and signal of the calorimeter in the absence of wires, and determine the heat leakage for different wire diameters using a mathematical formula. 3 il. (Ls

Description

The invention relates to measuring the amount of heat, namely to a method for determining heat leakage through the wires of a calorimeter, and can be used for precision measurements of thermal and physical parameters.

For example, a method is known for determining heat leakage through the wires of a calorimeter by means of a differential thermocouple, which consists in finding a temperature gradient in the wires and calculating heat leakage by analyzing the 1J dependence.

The disadvantage of this method is that the calculated estimated temperature gradient along the length of the wire is substituted for the analytical dependence, which reduces the accuracy of determining the heat leakage.

The closest to the proposed invention (prototype of the invention) is a method for determining heat leakage through wires, which consists in passing a constant electric current through the calibration element and measuring the joule power released on it during steady state operation of the device, followed by calculating the heat leakage from using analytical dependence 2.

The disadvantage of the method is. that it only allows heat leakage to be determined by heat conduction, and it does not take into account heat leakage by convection and radiation, and this increases the measurement error of the thermal parameters.

The purpose of the invention is to improve the accuracy of determining the heat leakage through the wires of the calorimeter.

The goal is achieved. that in the method at a constant joule power for different | ate

00

the next

The diameter of the device makes it possible to measure the sensitivity and signal of the calorimeter, by which the sensitivity and the signal of the calorimeter are determined by extrapolation in the absence of wires, and the calculation of tepp leakage is performed by the mathematical expression

 -w-deM

where W is the Joule power allocated to the calibration element;

Е (Фп) calorimeter signal depending on the diameter of the wires;

K (Fp) - the sensitivity of the calorimeter, depending on the diameter of the wires;

Е (Ф 0) is the calorimeter signal in the absence of wires,

K (f 0) is the sensitivity of the calorimeter in the absence of wires.

Comparative analysis with the prototype allows us to conclude that the claimed method differs in the use of a time sequence of operations performed with a calorimeter and a set of homogeneous wires of the same cross section; the ability to detect heat leakage through the wires of the calorimeter taking into account leakage due to heat conduction, convection and radiation from the side surface of the wire; using a new calculation formula for finding heat leaks.

Thus, the proposed technical solution meets the criterion of novelty.

The invention has been implemented using a device whose scheme is shown in FIG. one; in fig. 2 shows the dependence of the sensitivity of the calorimeter on the diameter of the wires; in fig. 3 shows the dependence of the calorimeter signal on the diameter of the wires.

The device contains a calorimeter 1, a calibration element 2, a signal 3 and potential 4 wires that are connected to a voltmeter, current wires 5 are connected to a sample resistance coil 6 and a DC power source 7.

Since no technical solutions have been found which have features similar to the distinctive features of our proposal, it can be concluded that the criteria are being observed to be significantly different.

The method is carried out as follows.

The calorimeter 1 is placed, for example, with a set of homogeneous copper wires of 0.4 mm (F1) diameter (current 5 and Almay A) of the same cross section in thermostatted conditions, Transmit electric current from the power source 7 through the current

the wires 5 and the calibration element 2 determine the joule power generated on it by detecting the voltage drop U by the potential wires 4 and the current I passing through

model resistance coil 6; In steady-state mode, the calorimeter measures its sensitivity K (cbi) and signal E (F1). Then, the above measurements are carried out with different diameters.

wires (Ф2 0.25 mm and Фз 0.10 mm) with a constant power allocated to the cushioning element. Moreover, to build dependencies K (Fp) and E (Fp), it is sufficient to measure K and E at 2-3

wire diameters of the same cross section, e.g. 0.1, 0.3 and 0.5 mm, after which they are found with the aid of those constructed in fig. 2 and 3 dependences sensitivity K (F 0) and signal E (F 0) of the calorimeter by extrapolation

obtained straight in the direction of reducing the diameter of the wires to the point of intersection of the direct with the axis of ordinates, i.e. in the absence of wires. Next, heat leakage from the calorimeter is determined for a different set of wire diameters by the formula

qym (wn & ") ,.

where n is the number of sets of wires (n - 1, 2, 3.. N). For example, for our case, if the diameter of the wires is Ft 0, 20 mm of heat leakage through the copper wires of the calorimeter will be

Qym (ft) 0.20) 0. -1 .1 0.76

 1.66-W3 W;

1.3-0.65

45

or

Lp Qy ™ (ft 0.2) n „,

Aqym- HJ °

On the other hand, the measurement of heat leakage by the method (prototype) will give a value for Ft 0.2 mm,

dut (ft 0,2) 0,9b-10 3 W

or

An Ош1Фт 0,2) По70 /

ii QymI. I I U 3 / / o.

those. we obtain an underestimation of the measurement error Aqym (ft 0.2) by 0.43%. This difference can be explained by the fact. that the method (prototype) measures the heat leakage through the wires only taking into account thermal conductivity, without taking into account convection and radiation from the side surface of the wire, and this introduces an additional error in the final result of the measurement of thermal parameters,

Thus, the proposed method for determining the heat leakage in the wires of the calorimeter allows, in comparison with the prototype, to improve the accuracy of the precision thermophysical parameters, taking into account the heat leakage by about 1%,

Claims (1)

Invention Formula Method for determining heat leakage through the wires of the calorimeter, including passing a constant electric current through the calibration element of the calorimeter, measuring the Joule power on the calibration element of the calorimeter, and calculating the heat leakage, so as to improve the accuracy of determining heat leakage through the calorimeter wires , at a constant Joule power, for different diameters, the @ sensitivity and the calorimeter signal are measured, which are used to extract the signal and signal to - / yurimogr in the absence of wires, and heat leakage calculation is performed by the mathematical expression Ruth (Phgp) - W 1 where W is the Joule power at the calorimeter calibration element; Е (Фп) - signal of the calorimeter depending on the diameter of the wires; K (Fp) - the sensitivity of the calorimeter, depending on the diameter of the wires; Е (Ф 0) is the calorimeter signal in the absence of wires; K (f 0) is the sensitivity of the calorimeter in the absence of wires. to, Hi 3m ABOUT Oj 0.2 Fie. i Oj 0,2 о, з of 05 -,, Fig.Z 0.3 AB 0.5 ft, mm