SU817559A1 - Device for determing heat emission at boiling water - Google Patents

Description

I

The invention relates to a measurement technique and can be used to study heat transfer processes during boiling liquids.

A device is known for. tj time of heat transfer when boiling liquid on the surface of an experimental tube with an internal heater {D.

However, this device allows to investigate only stationary processes, in addition, the thermocouple has a large inertia.

The closest technical solution is a device for studying heat transfer during boiling of liquid with direct electric heating of an experimental tube, containing a vessel with a liquid in which a metal tube is placed, heated by joule heat passed through a constant current tube, a movable thermocouple for determining the air temperature inside tubes, fixed thermocouple for measuring the temperature of the boiling liquid,.

However, it is not possible to create electrically controlled temperature gradients in a metal tube of a known device and to achieve them

self-oscillating pulsations, which is necessary to study various boiling regimes on non-isothermal surfaces.

The purpose of the invention is to increase the measurement accuracy when obtaining controlled, electrically controlled, 1 hp, 1, ionic and auto lobe temperature gradients.

The goal is achieved by the fact that in a device for determining heat transfer during boiling a liquid containing a closed vessel with liquid

15 and an experienced heater placed in it with a direct electric heating with a constant toxolation, the pilot heater is equipped with an electric probe and is made of a semiconductor with an electrical thermal negative negative resistance.

Placing an experienced heater along the semiconductor electric probes and measuring with their help the fall

Claims (2)

25 voltage, calculated by the electrical conductivity of individual parts of the pilot heater. Comparing the obtained values with the known temperature dependence without joule heating, it is possible to determine the wall temperature of individual parts of the heater. FIG. 1 schematically shows the proposed device; in fig. voltage distribution graphs. The device consists of a vessel 1 with a lid 2 filled with liquid 3, a semiconductor pilot heating 1 4, equipped with electrical probes 5, 6 ... n and a thermocouple 7 for measuring the temperature of the liquid. The vessel 1 is filled with the test liquid and a constant current from the power source is passed through the test heater 4. With the help of electrical probes 5 - n, the incidence of sludge along the heater is measured. Termopair 7 measures the temperature of the liquid. From the experimentally obtained voltage distribution curve, the voltage drop at the desired site is calculated (zone number and n). Target: on the electrical conductivity is calculated by the formula - (ANG where C is the specific conductivity d1 is the distance between the probes; S is the cross section of the heater; 1 is the current passing through the heater under voltage; then the temperature of this part of the heater corresponding to the calculated specific value electrical conductivity The experimental heater is made of electron silicon with a resistivity of 400 ohms with a rectangular plate with dimensions of 10 x b, 5 x o, 2 cm and is equipped with 19 zones. liquid nitrogen is used. A uniform voltage distribution along the heater gradually changes to a non-uniform voltage with increasing applied voltage. In Fig. 2, curve a represents the voltage distribution, and curve g represents the temperature distribution of the heater at 800 li voltage. that the distribution is already non-uniform. Increasing up to 2200 V leads to significant modifications of temperature gradients. Curves d and e, representing the course t (. are obtained using the voltage distribution U along the heater (b) curves at and equal to 2000 and 2200 V, respectively. With a further increase in U, temperature gradients come into self-oscillatory motion with a oscillation period, controlled voltage (the period is regulated from ten seconds to tens minutes) .. The proposed device allows to investigate boiling on non-isothermal surfaces, by creating electrically an orojTOM heater. controlled stationary and auto-oscillating temperature gradients, and also to simulate the processes of mixed boiling on the non-thermothermic surface of an experienced heater. Apparatus of the Invention A device for determining heat transfer during boiling of a liquid, containing a closed vessel with a liquid and placed in it an experienced heater with a direct current electric heating, characterized in that, in order to improve the accuracy in obtaining controlled, electrically controlled, stingable and auto-oscillating gradients temperature, an experienced heater is equipped with electrical probes and is made of a semiconductor with an electrothermal negative differential resistance. Sources of information taken into account in the examination 1. Petuhov B.S. An open study of heat transfer processes. M., 1952, p. 240 2. In the same place 241 (prototype). - -lai . -ISO