RU2668415C1 - Device of stand automated laboratory complex for studying heat exchange processes - Google Patents

Abstract

FIELD: teaching.SUBSTANCE: invention relates to special equipment intended for demonstration and practical training of students of universities and colleges for technical disciplines, and more specifically for demonstration and practical study of heat transfer processes in a plate heat exchanger between hot and cold water circulation circuit. Device of the bench automated laboratory complex for studying heat exchange processes contains a personal computer, to which a monitor, column loudspeakers, keyboard control unit, installation for the study of thermal processes, additionally containing a block of analog-to-digital converters connected to a personal computer, and a heat exchanger on a stand provided with studs for fixing the outer tube with air inlet pipes, the inner tube is inserted into the outer tube, with one of the tubes being fitted with temperature sensors, connected to the block of analog-to-digital converters. Usefulness is also to involve students in modern technical capabilities in fast and accurate processing of experimental studies.EFFECT: technical result consists in raising the technical level of knowledge transfer to students in the discipline of "Thermal technology", taught at a university, by equipping the stand with modern instruments and devices, allowing to receive high accuracy and reliability of work and, in addition, allowing to transfer received information about a process to a computer for further processing and obtaining both analytical equations, and graphical dependencies.1 cl, 5 dwg, 1 tbl

Description

The invention relates to special equipment intended for demonstration-practical training of university students and colleges in technical disciplines, and more specifically, for demonstration-practical study of heat transfer processes in a plate heat exchanger between a hot and cold water circulation circuit.

There is a well-known bench laboratory complex "Liquid heat engineering" TPZh-010-6LR-01 of heat engineering and heat engineering equipment at a university. The stand is made of one table with a hinged shelf for a laptop, a horizontal installation surface, under which there are two tanks with hot and cold water, two circulation pumps, and on a vertical surface attached to the rear edge of the horizontal installation surface, heat exchangers and several interchangeable devices - modules. In addition, two flow meters are attached to the vertical surface, which make it possible to measure the flow rate of the fluid flowing in the pipes supplied by a pump placed under the horizontal surface. (http://www.gpm-stend.ru/index.php/production/teplotechnika-termodynamika/303-teplotechnika-zhidkosti)

The disadvantage of such a stand is that it is not possible to create virtual models of real plants, enabling students to study its design and understand the physical process before working on a real plant.

The technical task is to increase the accuracy and quality of measurements at the bench of all necessary parameters. obtained both using measuring sensors and on a virtual image of a laboratory bench and ensuring their comparison in automatic mode, as well as providing automation of measurements of all necessary parameters, obtaining the required calculated predetermined functional dependencies and output to electronic and paper media used in the form report.

The technical problem is achieved by the fact that the device bench automated laboratory complex for studying heat transfer processes, containing a personal computer to which a monitor, sound speakers, a keypad control unit, an apparatus for studying thermal processes additionally contains a block of analog-to-digital converters connected to a personal computer and a heat exchanger on stand equipped with studs for attaching the outer pipe with nozzles for supplying air into the outer pipe inserted into the inner tube, wherein one of the pipe mounted temperature sensors connected to the unit analog-to-digital converters.

The technical result is to increase the technical level of knowledge transfer to students in the discipline "Heat Engineering" taught at the university, by equipping the stand with modern instruments and devices that allow to obtain high accuracy and reliability of work and, in addition, allowing you to transfer the received information about the process under study to a computer subsequent processing and obtaining both analytical equations and graphical dependencies. The usefulness also lies in introducing students to modern technical capabilities in the field of quick and accurate processing of experimental research

The device bench automated laboratory complex is characterized by the following drawings: in FIG. 1 shows a table with a personal computer (front view), FIG. 2 shows the installation for studying thermal processes. a) front view, b) side view, c) top view; in FIG. 3 shows a heat exchanger on a stand. a) front view; b) top view; in FIG. 4 shows an electrical circuit diagram; in FIG. 5 is a block diagram of a virtual installation.

The device (Fig. 1) consists of a table 1 with a personal computer containing a system unit 2, a personal computer to which are connected via cables: monitor 3, speakers 4, multi-tiered block device from analog-to-digital converters ADC 5, key control unit 6 mounted on the drawer 7 of table 1.

The installation for studying thermal processes (Fig. 2) contains a vertical panel 8, a water heater 9, an electric SHAPE 10ST pump 10 for increasing pressure of the CL15 GRS series, a plate heat exchanger 11, a flow meter 12 of SV-15X cold water, a flowmeter 13 of SV-15G hot water, a safety valve 14, air vent 15, filler pipe 16, hoses 17 and 18, manifolds 19 and 20, valve 21, three-way valve 22, temperature sensors 23. The water heater 9 is connected to an air vent 15, which is connected to a pump 10, which is connected to a flow meter 13, which connected to jellied th pipe 16, which is connected to the heat exchanger 11 and the collector 19, which is connected to the flow meter 12, which is connected to the hose 17, through plumbing fittings. The water heater 9 is connected to a faucet 22 connected to a manifold 20 connected to a valve 21, which is connected to a hose 18, by means of plumbing fittings.

The heat exchanger on the stand (Fig. 3) contains: a stud 24, hair dryers 25 and 26, an outer pipe 27 with two nozzles, an inner pipe 28. An outer pipe 27 with two nozzles is installed on the stand using studs and clamps, inside of which an inner pipe 28 passes. To create an air flow, hairdryers 25 and 26 are used, which are installed using clamps mounted on studs and directed into one of the pipes of the outer pipe 27 and into one of the outlets of the inner pipe 28.

The electrical circuit diagram (Fig. 4) of the installation consists of a power and matching part, galvanically isolated from each other by a power source 29. The power part consists of a circuit breaker 30, an electric heater 31, a boost pump 32, an indicator 33 for turning on the NETWORK installation, and switches 34 and 35 with suspension, respectively, “PUMP” and “Upr" of plugs 36 and 37 and sockets 38 and 39. The matching part is a power supply 40 of direct current 24 V and a matching board 41 with temperature sensors 42, 43, 44 and 45 and a connector46 “EXIT”. The matching board 41 is designed to power temperature sensors and connect them to a data acquisition device (for example, NL USB 6008) through a connecting cable.

The block diagram of the virtual installation (Fig. 5) consists of: block 47 "signal converter", block 48 "signal averaging", indicators 49, signal storage 50, waveforms 51, time delays 52, stop keys 53.

To measure the temperature and air flow rate in both the outer and inner pipes, a digital anemometer from the accessory kit is used, which is installed in one of the special holes on the pipes of the outer pipe 27 and at the ends of the inner pipe 28.

To control the temperature and air flow rate in the heat exchanger, a digital Testo 405-V1 anemometer is used from the tool kit and accessories, which is installed in one of the special holes on the pipes of the outer pipe 27 and at the ends of the inner pipe 28. Reinstalling the hair dryers and including the flows of cold and hot air in the outer and inner pipes, it is possible to obtain the conditions of heat transfer from the inner pipe 28 to the outer 27 and vice versa with the movement of cold and hot air both in passing and in the opposite direction x

On the vertical top of the table are fixed: equipment, appliances and components that form two circuits of water circulation - hot (heated water circuit) and cold.

Installation work.

The device operates as follows. The hot circuit is closed, with water heating in the electric heater 9 and forced circulation by the pump 10. Cold circuit - for running cold water. Heated closed loop water and cold water must pass through a plate water heat exchanger 11, where heat transfer occurs. The heat transfer process is controlled by thermal sensors 23.

Two water circuits are formed on the panel. The hot water circuit is closed. A pump 10 pumps this water through an electric heater 9, a flow meter 12, a plate heat exchanger 11, and again through an electric heater 9. To prevent excess pressure in the circuit above that allowed by the electric heater 9, a safety valve 14 is installed on it, adjusted to a pressure of 8 bar. An air vent 15 is used to remove air when filling the circuit with water. The circuit is filled with water through the filler pipe 16.

The cold water circuit operates from the water supply network. Water from the water supply through a hose 17, a flow meter 12 and a collector 19 passes through a plate heat exchanger 11, where it is heated from contact with hot water. After exiting the plate heat exchanger 11, water through the collector 20, the valve 21 and the hose 18 is discharged into the sewer. The valve 21 is used to control the flow of cold water. By switching the taps on the collectors 19 and 20, it is possible to change the direction of the cold water flow in the plate heat exchanger 11. The heat exchanger on the stand (Fig. 3) allows you to demonstrate the heat exchange between hot and cold air flows through a thin wall separating them. By reinstalling the hair dryers 25 and 26 and including the flows of cold and hot air in the outer 27 and inner pipes 28, it is possible to obtain the conditions of heat transfer from the inner pipe 28 to the outer 27 and vice versa when the cold and hot air moves both in the concurrent and in the opposite directions. By installing a digital anemometer Testo 405-V1 in the path of cold and hot air currents, you can control their speed and temperature. Hair dryers are connected to an AC power outlet with a voltage of 220 V and a frequency of 50 Hz installed in the room.

To control the process of heat transfer are four temperature sensors 23, the signals from which through a data cable and analog-to-digital Converter 5 is transmitted to a computer. To control the temperature and air flow rate in the heat exchanger, a digital Testo 405-V1 anemometer from the tool kit and accessories (table 6) is used, which is installed in one of the special holes on the pipes of the outer pipe 27 and at the ends of the inner pipe 28. As a liquid flow meter a device has been installed that provides the output of the creation of electric pulses that ensure coordination with the block of analog-to-digital converters of the Lab View program.

The stand can be equipped with two cold and hot water flow meters of the Sayany brand IVKA 407323 PS with an electronic output signal.

The Lab View analog-to-digital converters block is located on the second table, from the side closest to the first table.

Electrical equipment.

The electrical equipment is supplied from a single-phase AC network with a voltage of 220 V and a frequency of 50 Hz.

The electrical equipment includes starting, signaling and control equipment, an electric heater 9 and a boosting pump 10, as well as a data acquisition cable for transmitting signals from thermal sensors to an analog-to-digital converter 5 with the possibility of outputting data to a computer screen.

The installation has a network cable 6 meters long with a plug for connecting to the room’s power supply.

The electrical circuit diagram and connections are shown in FIG. 4. It serves to study the processes of heat transfer in a plate heat exchanger between the hot and cold water circulation circuit. When the circuit breaker 30 located on the vertical panel of the unit is turned on, the lamp of the “NETWORK” power indicator 33 lights up.

When you turn on the power to the temperature sensors 42, 43, 44 and 45 with the switch 35 "U _pr ", the switch will light up.

Turning the control knob of the electric heater 9 to the maximum heating position - the indicator on it will light up during the operation time of the heater. After heating the water to a maximum temperature of + 75 ° C, the heating elements turn off automatically and the indicator goes out.

When you turn on the pump for circulating water in the hot water circuit switch 34 "PUMP" - the switch will light up.

Observing the rotation of a mirror sprocket on a hot water flow meter. If it does not rotate, it means that the circuit is not completely filled with water. In this case, the pump 10 must be turned off and added to the water circuit.

Immediately after heating and circulating the water to the circuit, screw the cap of the air vent 15 in place.

If air enters the circuit (possibly due to untimely tightening of the cap and cooling of the water in the circuit), it is necessary to reheat the water and circulate it with the pump 10. In this case, the mirror sprocket on the flow meter should rotate. After that, immediately screw the cap onto the air vent 15.

Instructions for the experiment.

Run a special program on the computer connected to the installation.

In parallel with the “manual” experiment, turn on the PC, display the Lab View program, create a virtual sketch of the measuring instruments (thermal sensors connected to the plate heat exchanger, a virtual liquid flow meter) on the monitor. In accordance with the experimental procedure, we set the readings of thermal sensors in degrees from the keyboard. At the end of the experiment, we give a command to build a graph of the dependence of temperature on fluid flow. The computer temperature will display the water temperature in the first and second circuits before and after the heat exchanger. A virtual installation diagram, for example, studying heat exchange processes in a plate heat exchanger, is shown in FIG. 3.

To measure the temperature of cold and hot water at the inlet / outlet of the heat exchanger, the installation uses TP-1, TP-2, TP-3, TP-4 chromel-drop thermocouples. Thermocouples are connected to an automatic electronic potentiometer, the laboratory setup is connected via a cable and the ADC to a PC, and the “parameters” are read through a virtual model (Fig. 5).

The computer temperature will display the water temperature in the first and second circuits before and after the heat exchanger. The numbering of temperature sensors in the installation corresponds to the numbering on the computer screen.

With the help of a bench-mounted automated laboratory complex for studying heat transfer processes with measurements and processing results in the Lab View software environment, other laboratory works are carried out, the methodology of which is described in the methodological manual: Semenova E.V., Kireev D.V., Tretyak P.V. , Koryachkin V.P., Vanin BC Using Lab VIEW graphical programming environment for laboratory stands. Department "Machines and equipment for food production". Orel State Technical University, Oryol, 2007.

With the pump turned on, set the required cold water flow rate with the valve 21. The water temperature in both circulation circuits at the inlet and at the outlet of the plate heat exchanger will be displayed on the computer screen. The numbering of temperature sensors on the table panel corresponds to the numbering on the computer screen.

At the end of the work, you must:

- shut off the cold water supplied to the circuit;

- completely block the valve 21;

- disable a special program on the computer;

- turn off the power to the temperature sensors switch "U _pr ";

- turn off the electric heater by turning the knob to the “MINIMUM” position;

- turn off the pump with the “PUMP” switch on the table panel;

- disconnect the power plug from the outlet.

If necessary, you can drain the water from both circuits of water and electric heater (to produce when the power to the heater and installation is turned off).

To drain from the cold water circuit, direct the drain and supply hoses to the sewer and fully open the valve 21.

To drain from the hot water circuit

- make sure that the drain is blocked on two three-way valves 22

- disconnect the electric heater from the pipeline;

- install under the taps of the tank approximately 1.5 liters;

- unscrew the plugs on the taps;

- start to smoothly open the taps and gradually drain the water

After draining the water, close the taps 22 and unscrew the plug of the filler pipe 16 to communicate with the atmosphere. Open taps 22 again and finally drain the water from the top of the circuit.

To drain water from an electric heater it is necessary:

- to impose its inlet and outlet pipes with a cloth absorbing water;

- unscrew the union nuts and disconnect the supply fittings, while a small amount of water will pour onto the fabric;

- carefully remove the electric heater from the hooks fixed on the table panel, turn it over and drain the water into a container of at least 10 l;

- install the electric heater in place;

- wrap the plugs on the three-way valves 22 and the filler pipe 16.

2. The study of thermal processes on a heat exchanger on a stand.

To conduct the study it is necessary:

- install the heat exchanger on the stand in any convenient place or on the installation table;

- install with the help of clamps a hair dryer on one of the pipes of the outer pipe 27 (see Fig. 3), a second hair dryer - on one of the ends of the inner pipe 28. By turning on the flow of cold or hot air, it is possible to obtain heat exchange from the air flow in the inner pipe to the flow air in the outer pipe and vice versa, both in the opposite and in the associated direction of flow.

To measure the temperature and air velocity in both the outer and inner pipes, a digital anemometer Testo 405-V1 from the accessory kit is used. (table 6), which is installed in one of the special holes on the nozzles of the outer pipe 28 and at the ends of the inner pipe 29. (p. 2)

Measuring instruments, tools and accessories

As measuring instruments in the installation,

- flowmeter SV-15X;

- flowmeter SV-15G;

- digital anemometer Testo 405-V1.

The principle of operation of the SV-15X flowmeter is to measure the number of revolutions of the impeller rotating under the action of a flow of flowing water. The flowmeter has a special inlet filter, after passing through which cold water enters the measuring chamber with an impeller. Then the water passes into the outlet pipe. By the number of revolutions of the impeller, the volume of cold water flowing through the flowmeter is determined, which is converted into cubic meters by a scaling mechanical gearbox built-in inside. The arrow of the indicator device registers all data of the flowmeter.

Specifications:

- conditional diameter: 15 mm;

- nominal flow rate: 1.5 m ³ / h;

- medium temperature from + 5 ° C to + 40 ° C;

- pressure of the measured medium: not more than 1.0 MPa;

- counter type: vane.

Digital Anemometer Testo 405-V1 is a miniature device for measuring flow velocity and temperature with a function for calculating volume flow (the cross-sectional area is entered into the device memory). The design of the device provides for various positions of the probe and the rotary display, allowing you to simultaneously read the readings and monitor the direction of the air flow. The speed sensor is protected by a rotary cap, which is opened only during the measurement process. The device is equipped with a holder for mounting in a pipe.

Specifications for the Digital Anemometer Testo 405-V1 are shown in Table 1.

Table 1 - Specifications for the Digital Anemometer Testo 405-V1 Parameter Name Parameter value Measuring range 0.1 ... 10 m / s -20 ... 50 ° C 0 ... 99990 m ³ / h Error ± (0.1 m / s ± 5% of measured value) (0.1 ... 2.00 m / s) ± (0.3 m / s ± 5% of the measured value) (2.01 ... 10 m / s) ± 0.5 ° C (-20 ... 50 ° C) Resolution 0.01 m / s (0.1 ... 10 m / s) 0.1 ° C (-20 ... 50 ° C) Working temperature 0 ... 50 ° C Storage temperature -20 ... 70 ° C

Claims (1)

A bench-mounted automated laboratory complex for studying heat transfer processes, comprising a personal computer, to which a monitor, speakers, a keyboard control unit, a unit for studying thermal processes are connected, characterized in that it additionally contains an analog-to-digital converter unit connected to a personal computer, and a heat exchanger on a stand equipped with studs for attaching the outer pipe with nozzles for supplying air, is inserted into the outer pipe an early pipe, moreover, temperature sensors connected to a block of analog-to-digital converters are mounted in one of the pipes.

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