RU111644U1 - INSTALLATION FOR STUDYING NONSTATIONARY FREE CONVECTIVE HEAT EXCHANGE OF HORIZONTAL CYLINDER OF LIMITED LENGTH - Google Patents

Abstract

 1. Installation for studying unsteady free convective heat transfer of a horizontal cylinder of limited length, containing thermocouples mounted on the outer surface of the horizontal cylinder, a power source, a switching device, a control station, characterized in that the horizontal cylinder is made in the form of a thin-walled cylinder mounted on tripods, made of electrically conductive material and connected by means of a switching device to a control station and a power source made in ide DC power source, wherein a horizontal cylinder cavity established ballast cylindrical body made of a dielectric material, and a thermocouple attached to an area bounded by a semicircle of the outer surface of the horizontal cylinder. ! 2. Installation according to claim 1, characterized in that the thermocouples are made in the form of low-inertia thermocouples with a time constant of 0.06 s. ! 3. Installation according to claim 1, characterized in that the control station comprises a data acquisition and recording system and includes a personal computer connected in series with an installed application package, an expansion card, a connection panel, a terminal block to which thermocouples are connected.

Description

The utility model relates to the field of experimental research of natural convective heat transfer and can be used in laboratory facilities, with which you can simulate the flowing parts of power plants under conditions of thermal load increase.

Closest to the proposed technical solution is a laboratory unit for studying free-convective heat transfer of a horizontal cylinder of limited length (E.P. Barulin, A.S. Kuvshinova and others. Laboratory workshop on thermal processes. A training manual. GOU VPO "Ivanovo State Chemical Technological University ”), The installation consists of a thick-walled pipe, an electric heater powered by an alternating current main, and mounted on ceramic inserts, while the ends of the pipe in order to reduce leakage heats are closed by heat-insulating plugs, and thermocouples are fixed on the outer surface of the pipe.

The disadvantages of the known installation, which allows to study the heat transfer process only with stationary natural convection, are:

1. The large inertia of the heat transfer process.

2. The effect of an alternating current magnetic field on temperature.

3. Manual registration and data processing.

Modern power plants have a large number of pipelines of various lengths and configurations. The operation of the plants and their elements proceeds under complex thermodynamic-dynamic conditions caused by the presence of disturbing factors such as temperature inhomogeneity and thermal non-stationarity.

As a rule, plant elements are involved in conjugate heat transfer. Natural unsteady heat transfer under conditions of time-varying temperature of the cylinder wall of the part leads to significant changes in the structure of convection associated with high non-linearity of processes and the application of the superposition principle becomes unacceptable. The lack of accounting for non-stationarity in some cases leads to significant errors in the design of technical devices, the choice of modes of their optimal functioning and the development of control and automatic control systems. Knowledge of methods for calculating the local heat transfer coefficients of natural convection under non-stationary conditions play a significant role in increasing the efficiency of the apparatus.

The objective of the proposed utility model is to enable experimental study of the heat transfer process in unsteady free-convective heat transfer of a horizontal cylinder of limited length.

The technical result is achieved by the fact that in the installation for studying non-stationary free-convective heat transfer of a horizontal cylinder of limited length, containing thermocouples fixed on the outer surface of the horizontal cylinder, a power source, a switching device, a control station, according to the proposed utility model, the horizontal cylinder is made in the form of a thin-walled a cylinder mounted on tripods made of electrically conductive material and connected using a switching device At the same time, there is a control station and a power source made in the form of a direct current power source, while in the cavity of the horizontal cylinder there is a cylindrical ballast body made of dielectric material, and thermocouples are fixed in the area limited by the semicircle of the outer surface of the horizontal cylinder. In addition, the thermocouples are made in the form of low-inertia thermocouples with a time constant of 0.06 s, and the control station contains a data acquisition and recording system including a personal computer connected in series with an installed application package, an expansion board, a connection panel, and a terminal block to which thermocouples are connected.

The essence of the utility model is illustrated by the drawings, in which Fig. 1 shows a schematic diagram of the proposed installation for studying unsteady free-convective heat transfer of a horizontal cylinder of limited length, Fig. 2 is a diagram of the termination of thermocouples, and Fig. 3 is a diagram of data acquisition and recording.

In the drawings, the numbers indicate:

1 - horizontal thin-walled cylinder of limited length,

2 - low-inertia thermocouples, non-ripe chromel-kopel,

3 - DC power source,

4 - switching device

5 - control post.

6 - tripod,

7 - ballast cylindrical body,

8 - personal computer,

9 - expansion card,

10 - connecting panel

11 - terminal block.

Installation for studying unsteady free-convective heat transfer of a horizontal cylinder 1 of limited length contains thermocouples 2 mounted on the outer surface of the horizontal cylinder 1, a power source 3, a switching device 4, control post 5.

The proposed installation is characterized in that the horizontal cylinder 1 is made in the form of a thin-walled cylinder mounted on tripods 6 made of electrically conductive material and connected by means of a switching device 4 with a control station 5 and a power source 3. The horizontal cylinder 1 is made by laser welding in the form of a thin-walled, 0.1 mm thick, cylinder made of stainless steel X18H10T with a diameter of 22.5 mm and a length of 337.5 mm, equal to 15 cylinder diameters. The power source 3 is made in the form of a DC power source. In the cavity of the horizontal cylinder 1, a ballast cylindrical body 7 is made of dielectric material. Temperature measurements are taken directly on the heating surface. For this, the thermocouples 2 are fixed in the area limited by the semicircle of the outer surface of the horizontal cylinder 1, and are made in the form of low-inertia thermocouples with a time constant of 0.06 s. The control station 5 comprises a data acquisition and recording system, including a personal computer 8 connected in series with an installed application package, an expansion board 9, a connection panel 10, a terminal block 11 to which thermocouples 2 are connected.

Installation for studying unsteady free convective heat transfer of a horizontal cylinder of limited length works as follows.

The horizontal cylinder 1 is placed on tripods 6 mounted on both ends of the cylinder, which are conductors for supplying electric direct current. Thermal non-stationary conditions are realized by supplying and disconnecting electric current through the experimental site. Heating is carried out by applying direct current and for a very short time. To exclude conjugate convection inside the horizontal cylinder 1, a ballast cylindrical body 7 is installed with a diameter of 22.5 mm. As a ballast body used wood, machined from aspen. The source 3 of the DC power supply for heating are two car batteries having parameters of 12 V and 50 A / h, connected in series. The power source 3 is switched with a horizontal cylinder 1 by means of a switching device 4 and a control post 5.

To measure the temperature on the surface of a horizontal steel cylinder 1, low-inertia, non-ripe, chrome-copel-free thermocouples 2 with a diameter of 0.02 mm are used. The contact pair of thermoelectrodes is made by the method of capacitor welding. The termination scheme of thermocouples in the experimental section is presented in figure 2. Seven thermocouples are prepared to the semi-surface of the cylindrical experimental section through the central angle φ = 30 ° starting from the front critical point.

In non-stationary conditions, the dynamic characteristics of thermocouples are important. The time constant of thermocouples 2 is 0.06 s, which is approximately two orders of magnitude lower than the duration of the investigated thermal processes. Thermophysical experimental studies are associated with the need for a large volume of measurements of various physical quantities, an increase in the volume, accuracy and complexity of the mathematical processing of experimental data. The use of automated measuring and information systems can significantly overcome difficulties. Such systems shorten the time for obtaining results, processing experimental materials and improve the quality of the results. In the proposed installation for the study of unsteady free-convective heat transfer of a horizontal cylinder of limited length, the equipment of National Instruments (NI), with the Lab View software package, was used. Figure 3 presents a diagram of the collection of information from thermocouples 2 to a personal computer 8, on which temperature data were recorded in real time.

Data acquisition is implemented as follows. The analog information from the thermocouples 2 through the terminal block 11 is entered into the connecting panel 10 of the brand BNC 2120 manufactured by NI. The signal is transmitted through the bus to the PCI-6040E brand expansion card 9, which is installed in the slot of the personal computer 8. Universal DAQmx drivers are installed in the personal computer 8. Information is processed, recorded and displayed graphically on a monitor in the Lab VIEW virtual instrument software environment. Knowledge of methods for calculating the local heat transfer coefficients of natural convection under non-stationary conditions play a significant role in increasing the efficiency of the apparatus.

The use of the claimed utility model will allow for the non-stationarity to be taken into account when designing technical devices, choosing the modes of their optimal functioning, and developing control and automatic control systems.

Claims (3)

1. Installation for studying unsteady free convective heat transfer of a horizontal cylinder of limited length, containing thermocouples mounted on the outer surface of the horizontal cylinder, a power source, a switching device, a control station, characterized in that the horizontal cylinder is made in the form of a thin-walled cylinder mounted on tripods, made of electrically conductive material and connected by means of a switching device to a control station and a power source made in ide DC power source, wherein a horizontal cylinder cavity established ballast cylindrical body made of a dielectric material, and a thermocouple attached to an area bounded by a semicircle of the outer surface of the horizontal cylinder. 2. Installation according to claim 1, characterized in that the thermocouples are made in the form of low-inertia thermocouples with a time constant of 0.06 s. 3. Installation according to claim 1, characterized in that the control station comprises a data acquisition and recording system and includes a personal computer connected in series with an installed application package, an expansion card, a connection panel, a terminal block to which thermocouples are connected.