SU1703940A1 - Method and device for regulation of heat transfer between liquid and gaseous heat-transfer agents - Google Patents

Abstract

The invention relates to heat engineering and allows thermal stabilization of the gaseous heat carrier while simultaneously improving the accuracy of heat transfer control in the vertical position of the heat exchange surface between the gaseous and intermediate heat transfer media. The device for regulating the heat transfer of GT p 1 to 23 comprises a housing 1 with a pallet 5 filled with a dielectric intermediate gas-liquid coolant, and a heat exchanger 8 located in the housing 1 for intermediate and liquid heat carriers and a heat exchanger 22 for intermediate and gas coolants. The first of these heat exchangers is made like a pipe in a pipe and is equipped with an electrohydrodynamic pump with electrodes, and the second is in the form of vertical finned cylinders 23, in the cavity of each of which the te electrode is arranged as a perforated pipe. equipped with a spreader with the formation of an electro-jet dispersant. The device is equipped with a control system. When the device operates, due to the increased intensity of heat exchange in heat exchangers 8 and 22 and low inertia of electrohydrodynamic pumps, an increase in the accuracy of heat transfer control between the gaseous and intermediate heat transfer media, as well as the thermal stabilization of the heat transfer gaseous medium is achieved. 2 sec. and 1 z. p. f-ly, 9 ill. yy I / GG7 ate with VJ o SO y N O Figure 1 2 3

Description

The invention relates to heat and power engineering and can be used in cooling electronic equipment, in air conditioning systems, in thermostatic control of gaseous media and in various objects with a source of heat or cold of any nature connected to a consumer through a heat source, for example consumer, including on water transport.

There is a method of controlling heat exchange between two horizontal surfaces by applying heat to the bottom surface and then transferring it to the upper surface through a two-phase intermediate coolant, one of the phases of which is dispersed, and the other a continuous dielectric medium, with a variable effect on the intermediate coolant by an electric field by periodically turning it on and off, and the dispersed phase in the heat exchange process is fed into the liquid medium through the lower surface into the idea of non-condensing gas bubbles. In addition, the method provides for the possibility of additional regulation of heat transfer by continuously supplying a liquid medium, changing the phase feed rate during the circulation of an intermediate heat transfer fluid, and in the presence of an electric field the feed rates of both phases increase, and in the absence of a field, the feed rate of the dispersed phase reduce.

The method is implemented in a thermostat comprising a housing with a pallet filled with a dielectric intermediate gas-liquid coolant, and a main heat exchanger located in the housing connected to the coolant pipeline and a bubbler connected to the compressed air pipeline and connected in series a temperature sensor, an adjustment unit and an actuator, moreover, the bubbler is made in the form of a heat exchange surface, forming an additional heat exchanger, connected to the pipeline coolant, and Tel'nykh element is designed as electrode surfaces formed by the heat exchange core and the additional heat exchanger connected to a source of electric field communication control unit with zannomu.

The disadvantages of the known technical solutions are that they do not provide for thermal stabilization of the gaseous coolant. Use last

as an object of thermoregulation, it is impractical because of the gas flow rate limited during sparging and its pollution in the bubbling layer with vapors of an organic or other dielectric liquid, which, as a rule, is unacceptable. The main reason for the lack of necessary accuracy of thermal stabilization of the gaseous coolant lies in the fact that

0 low accuracy of heat transfer control (heat transfer intensity, temperature pressure, etc.), i.e. smoothness, subtlety and control flexibility are not high enough.

5 The purpose of the invention is to provide thermal stabilization of the gaseous coolant while simultaneously improving the accuracy of heat transfer control in the vertical position of the heat exchange surface between the gaseous and intermediate heat transfer media.

The goal is achieved by the fact that according to the method of regulating heat transfer between liquid and gaseous

5 heat transfer media limited by heat exchange surfaces and interacting with each other through the dielectric intermediate gas-liquid heat carrier circulating between the indicated

0 by the surface. By periodically affecting the heat exchange surface between the intermediate and gaseous heat carriers. The electric field, the circulation of the intermediate heat sink 5 l is carried out along the heat exchange surface with the liquid heat carrier by periodically acting on it with an additional electric field, measure the deviation temperature of the gas-gas different heat carriers from the temperature of thermal stabilization, and the impact of the main field is carried out to ensure the dispersion of the liquid phase intermediate heat carrier, and the periods

The 5 actions of this field are chosen within the periods of the additional field, and its intensity is directly proportional to the value of the indicated deviation of the temperature of the gaseous coolant.

0 In the proposed device for regulating heat transfer between liquid and gaseous heat transfer fluids, comprising a housing with a tray filled with a dielectric intermediate gas-liquid heat transfer fluid and heat exchangers located in the housing for heat exchange between intermediate heat exchangers on the one hand and liquid and gaseous heat transfer fluids on the other, and heat exchanger for intermediate and gaseous coolants

equipped with an electrode connected to an electric field source; a heat exchanger for intermediate and liquid coolants is made like a pipe in a pipe, in the inner of which is placed an electrohydrodynamic pump connected to a source of additional electric field and equipped with a suction nozzle immersed in the liquid phase of the intermediate heat carrier and the heat exchanger for intermediate and gaseous coolants is made in the form of vertically installed finned cylinders in the case of plugged upper ends, the electrode is located in the inner cavity of each cylinder along its axis and is made in the form of a perforated tube connected to the lower end of the discharge pipe, and equipped with a slitter with an annular horizontal slit for the passage of the intermediate heat carrier fluid at the upper end.

In addition, in order to reduce the effect on its operation, the position of the device in the aftermath of gravity is additionally filled with degassed dielectric fluid between the housing and the heat exchangers.

FIG. 1 shows a device for controlling heat transfer between liquid and gaseous heat transfer fluids, longitudinal section; in fig. 2 shows section A-A in FIG. one; in fig. 3 shows a section BB in FIG. one; in fig. 4 - finned cylinder with integrated perforated tube, longitudinal section; in fig. 5 shows a section B-B in FIG. four; in fig. 6 - section G-Y in FIG. 3; in fig. 7 is a functional diagram of the system of thermal stabilization and automatic control; in fig. 8 is an electrical circuit of the sensor and temperature sensor; in fig. 9 is an electrical polarity comparator circuit.

The device comprises a body that is shaped as a double vessel; outer 1, made of metal, and inner 2, made of durable dielectric (thermal insulation material). To ensure effective heat insulation of the hull, the surfaces of vessels 1 and 2 are coated with a thin layer with the lowest possible emissivity, for example, aluminum paint. Between the vessels a thin layer of air 3 is provided, the thickness of which is determined from the depth of

Grnp. 5pr P Ttnp YuOO. (one)

where Gr is the Grashof number; Pr - Prandtl number.

When performing (1), air convection is eliminated and the effective thermal conductivity of the layer Alp is determined by the thermal conductivity of air, Yes, which is not higher than the thermal conductivity of the best thermal insulation materials. In addition, due to the low density of air, the thermal inertia of such insulation is low, which has a positive effect on the quality of thermal control of the object.

The body is made collapsible in the form of a top cover 4 and a pallet 5 connected with the help of flanges 6. For the rigid connection of vessels 1 and 2, there are strips 7. made of a dielectric (heat insulator).

In the pallet 5 (Fig. 3) there is a heat exchanger 8, made like a pipe in a pipe according to a countercurrent circuit with an outer pipe 9. connected to the pipeline 10 of the heat-transfer fluid (VT). A multistage electrohydrodynamic (EHD) pump (Fig. 6) with high-voltage electrodes 12 and grounded electrodes 13 having galvanic contact with the pipe 11 is embedded in the inner tube 11 of the heat exchanger 8. The electrodes 12 are mounted on a common metal rod 14 through which the adjustable high-voltage potential is supplied ( The dielectric bushings 15 and 16 are installed between the electrodes 12 and 13, and the sleeves 16 contain spokes 17 (FIG. 4) and simultaneously serve to center the rod 14 relative to the pipe 11. Suction pipes 18 EHD-n Sosov immersed in a liquid phase intermediate heat medium (PT) is yuschuyus dielectric medium, and the discharge tubes 19 are connected to the collectors 20 feeding the liquid phase to the perforated pipe 21 Elektrostruynyh dispersants (FIGS. 3 and 4).

A heat exchanger 22 is fixed on the lid 4. It is made in the form of a vertical checkerboard beam communicating with the tray 5 of the cylinders 23 with the upper ends 24 closed (Fig. 4) and the common external fins. The fins are made in the form of a section of parallel horizontal disks 25, along the central axis of which channel 26 is provided. Connected to the inlet 27 of the supply of gaseous coolant (GT). Channel 26 has a built-in centrifugal fan 28 with an electric motor 29. Perforated pipes 21 are located inside the vertical cylinders 23 and communicating with them through channels 30, the spreading devices 31 (Fig. 4) of the liquid phase of the PT (Fig. 5), Spreading components 31 are made of a dielectric material and, by aligning the perforated pipes 21. at the same time, both decoupler ensures, high capacity pi from shorting to grounded cylinder 23. The horizontal beam 32 rastekatel annular slit 31 facing the inner side wall of the cylinder 23.

The perforated tube 21 (FIG. 4) is made of an electrically conductive material and performs the function of a high-voltage electrode 33 of an electrojet disperser. Holes 34 are drilled on the side surface of pipes 21. Electrodes 33 are connected to a high-voltage regulated potential (pi of an electric field source 35, built in a pallet 5 with a dielectric fluid PT. Centering of perforated pipes 21 relative to the longitudinal axis of the cylinder 23 is also carried out by a dielectric nozzle 36. the principle of non-casting inkstand. The last one warns the splashing of the rigid PT phase onto the surface of cylinder 23 during rolling when the device is operated on board water, ground or air The pipe 33 through the upper end communicates with the spreading device 31. Its lower end is connected to the collector 20 for feeding the liquid phase of the PT of the EHD pump from the tray 5. The total area of the living sections of the holes 34 should be less than the area of the living cross section of the perforated pipe 21, Otherwise, the separation of the flow of the liquid phase of the PT into the jet and film flows (through the spreading device 31) is difficult, since all the liquid will flow mainly through the holes 34.

Source 35 of the electric field (Fig. 7) is two-channel. The first channel produces a constant high-voltage potential (pi supplied to high-voltage electrodes 12 of the EHD pump 37 via a metal rod 14 (Fig. 6). The second channel of the source 35 produces an adjustable high-voltage potential pi. Supplied to the electrodes 33 of the electrojet dispersers. The EHD pumps 37 and electrojet dispersers 21 in the functional scheme of automatic heat and thermoregulation of the proposed device 38 (Fig. 7) function as actuators. At the same time, the temperature sensors RTI and Pt2 are set s in the output of the second branch pipes 39 (gas) heat exchanger, embodied as polup-. rovodnikovyh thermistors and are connected to two opposite arms of the bridge (Fig. 8), which is configured as a dial

40 temperature. In the remaining two arms of the setting unit bridge 40 (Fig. 8), paired potentiometers Rzi and RZ2 are connected, with which the temperature is set (roughly)

GG statisation. Fine adjustment of the set temperature is carried out using an additional R-3 potentiometer. connected to the output circuit U1 and Y2 of the knob 40, associated with the preamplifier 41 of the signal unbalance of the bridge. The bridge is powered via terminals nl and p2 (fig. 8) from a stabilized direct current source 42 connected to a common power supply unit 43.

The preamplifier 41 is coupled to a polarity comparator 44 made in the form of a diode switch D1 and D2 (Fig. 9). The polarity of the transmitted signal is set using a two-position switch P. connected at inputs Y3 and Y4 and outputs L and L2 of comparator 44.

Next, in the functional diagram, after the polarity comparator 44, an input signal voltage comparator 45 is connected with a unit 46 for thermal stabilization of the GT and a unit 47 for controlling the magnitude and time of application of the potential pi of the source 35 of the electric field. In the input circuit of the lumen source source 35, there is a common for both channels p and (pr breaker 48 and single-channel (channel only) breaker 49. The breakers turn on or off the source 35 from the supply (control) circuit, and the breaker 48 is connected to the comparator 45 eg and the breaker 49 with the control unit 47. In addition, the common breaker 48 has feedback to the electric field source 35 through the protection unit 50. The preamplifier 41, the voltage comparator 45, the control unit 47, the breakers 48 and 49 and the block 50 protections are connected, as well as a stabilized direct current source 42, to a common power supply unit 43, which converts mains or on-board voltage to the operating voltage of the indicated units.

For filling the device with a dielectric medium, evacuating and draining the liquid phase, nozzles 51 and 52 with valves 53 and 54 are provided.

The method is carried out as follows.

VT for which any liquid can be selected, circulates through conduit 10 in the annular gap between pipes 9 and 11 of the countercurrent coil. When the fan is running 28 GT. eg

air is sucked from the thermostatically controlled volume through the nozzle 27 and due to centrifugal forces it is injected radially through the slots between the ribs 25, blowing vertical Chess bundle of cylinders 23 and entering back into the thermostatted volume through the nozzles 39.

 During the period of switching on the main electric field created by the potential p, the liquid phase of the PT located in the sump 5 is sucked up by the EHD pumps through nozzles 18, is pumped back to the flow of VT through pipes 11, exchanging heat with VT, and further is pumped through the nozzles 19 and collectors 20 in perforated pipes - electrodes 21 of electrojet dispergators. In pipes 21, the liquid is divided into two streams: the first through the openings 34 forms a liquid film flowing along the outer wall of the pipe 21, the second flows through the channels 30 and the annular slots 32 of the spreading valves 31 to the inner walls of the vertical cylinders 23, forming the second flowing films through them, The films flow back into the tray 5 through the nozzles 36.

The inclusion of an additional electric field created by the potential p2 leads to the mutual dispersion of liquid films flowing along the walls of the cylinders 23 and the pipes 33, with the result that a drop-flow circulation of the liquid phase PT occurs in the interelectrode space. contributing to its intensive renewal and reduction of the effective film thickness. The thickness of the film depends on the intensity of the additional electric field. those. on the value of the potential p2, and with the increase of the latter within practically achievable limits, the film thickness becomes less than the thickness of the thermal boundary layer. Thus, the increase leads to a significant intensification of heat exchange between the liquid phase of PT and HT due to the intensification of the film renewal process and the reduction of its thickness.

In the absence of the main and additional electric fields, the liquid phase of the PT is completely inside the pallet 5 and heat transfer is limited by the heat transfer by free convection at the interface of the liquid phase of the PT with the walls of pipes 9 and 11. Since there is a gas (vapor-gas) between the heat exchange surfaces 9, 11 and 23 Since the phase of the PT, in the absence of fields, the heat transfer between the VT and GT is very insignificant due to the high thermal resistance of the gas phase.

Thus, the electric field, both primary and secondary, is a means of controlling the intensity of heat transfer, and the interaction

two fields, by varying the time of their application and the field strength, can significantly improve the accuracy of this adjustment.

When using a vapor-liquid dielectric medium with a phase equilibrium temperature between the temperatures of the heat exchange surfaces with the HT and HT, the heat transfer intensity increases due to

processes of phase transitions on these surfaces. In this case, the device operates in the mode of electrically adjustable heat pipe. However, the use of such PT is advisable when

heat flux from HT and VT, since in the opposite case, gravity forces contribute to the return of condensate formed on the heat exchange surface with HT to the boiling surface (heat exchange surfaces 9 and 11) and control of heat transfer intensity by electric fields less efficiently.

In the case of a strong change in the position of the device in the field of gravity, it is advisable to use a degassed dielectric fluid, i.e. exclude the content of the vapor phase from the PT. In this case, the harmful effects of gravitational forces are relatively

where the device changes its position arbitrarily, is suppressed by the forces of the electric field, which must prevail over the gravitational forces. The effect of controlling heat transfer in this case is achieved by electroconvection PT, the effect of which is significantly higher than thermogravitational convection.

Heat stabilization of GT is carried out

in the following way.

Using a paired potentiometer Rzi and Pr2. connected in the bridge circuit setpoint 40, set (roughly) the temperature of the stat GT. Since in the opposite shoulders of the bridge are connected semiconductor temperature sensors RTI and Rr2. then the balance of the bridge will depend on the difference between the current and the set temperature of the GT. To increase the sensitivity of the bridge

and the magnitude of its imbalance signal, it is necessary that RZ1 Rz2 Rn Rrt R. A change in resistance D R of sensors RTi and Rr2 depending on temperature is as large as possible, which is ensured by using a floor as RT and RT2

conductor thermistors for which

d (|) dt, (2)

where B and RO are constants depending on the properties of the semiconductor material, K and Ohm, respectively;

T - absolute sensor temperature, K; AT is the temperature change, K. If the specified conditions are met, the voltage of the bridge unbalance signal will be maximal and will be

UV1-V2 Unl -P2 -RG (3)

where UY1-Y2 is the voltage at the output of the 40-gauge.

Uni-n2 is the stabilized supply voltage from source 42 to terminals n1 and n2.

The unbalance signal of the bridge is amplified by the preamplifier 41 and goes further to the polarity comparator 44, operating in a diode mode and transmitting a signal, only if its polarity corresponds to a given one, using switch P. The purpose of the polarity comparator is to provide negative feedback between temperature sensor RT1, Rr2, and thermal control object 38 in any direction of heat flow between GT and VT. For example, if the heat flux is directed from HT to VT, then when the current temperature of the HT exceeds the set value in accordance with formula (2) NL, the polarity of the unbalance signal at the outputs Y1 and Y2 decreases depending on the polarity of the supply potentials at the terminals n1 and n2 will be one (for definiteness, let us take, and on Y2 -). In this case, the cooling intensity of the GT should increase, i.e. this unbalance signal must be passed by comparator 44. But if under the same conditions we assume that the heat flux is directed from the VT to the HT, then passing the unbalance signal by the comparator 44 will lead to even more heating of the HT, i.e. negative feedback will go to positive and regulation will not lead to thermal stabilization of the GT. To prevent this from happening, it is sufficient to use the switch P of the comparator 44 to provide a signal transmission mode depending on the direction of the heat flow.

Next, the unbalance signal is applied to the voltage comparator45. Depending on the

0

D

0

0

five

the accuracy of temperature control GT, which is set by setter 46, the comparator 45 passes the signal to the block 47 for controlling the magnitude and time of application of the potential p2, if the voltage of the incoming signal is greater than the specified one, or to the common breaker 48, if the signal voltage is equal to or less than the specified one by block 46 voltage comparison. In the first case, directly proportional to the voltage of the imbalance signal, the control unit 47 adjusts the potential (pi of the electric field source 35 and its application time by turning the fz channel on and off using the interrupter 49 controlled by it. In the second case, the source is turned off 35, i.e., the primary and secondary electric fields. Thus, control of the actuators, i.e., the electrojet dispersers 21 and the EHD pumps 37, is carried out.

When a breakdown mode occurs, the protection unit 50 generates a command to disconnect the electric field source 35 from the common power supply unit 43 using the common chopper 48.

The temperature of the HT is controlled by an exemplary thermometer, and if it is different from the desired one in the thermal stabilization mode, the driver unit 40 is adjusted with a resistor. those. the temperature of the GT stat is set (thinly).

Experimental verification of the proposed method showed that by varying the ratio Si / $ 2 (where Si is the area of the living sections of the holes 34 of the perforated pipe 21; 2 is the area of the living cross section of the pipe 21), the greatest effect of heat transfer control is achieved at 81/82 = 0.3- 0.8 In this case, the ratio of the heat flux densities in the electric field and in its absence Ч vf, / 0.0 can be adjusted within 2.2.1.

Stable dispersion is achieved at field voltages between the electrodes 23 and 33–20–70 kV / cm, however, at 30 kV / cm and above, the power consumption associated with corona discharge increases.

The high-voltage supply potential of the electrodes of the 12 EHD pump was kept constant during the experiment (p 20 kV). By switching the potential on and off (f and varying the value, the heat transfer intensity was adjusted to 5–90% of the maximum heat load, and the control accuracy did not depend on the direction of change in the heat flux density. The results were reproducible with an accuracy of ± 5%.

The sixfold intensification of heat exchange during dispersion compared to heat transfer with a clear film flow of the liquid phase PT (transformer oil and kerosene were used) is explained by a decrease in the thickness of the film flowing down the wall of the cylinder 23 less than the thickness of the heat transfer characteristic of large-volume convection.

The greatest intensity of heat transfer is achieved by providing phase transitions on the surface of the heat exchange of PT (vapor-liquid mixture of freon - 113) with HT and VT. A narrower adjustment range is achieved when the tank for a PT is completely filled with a liquid degassed phase (kerosene, transformer oil); however, at voltages above 20–30 kV / cm, the effect of regulation becomes self-similar from the orientation of the device in the field of gravity.

The proposed method and device for regulating heat transfer between liquid and gaseous heat transfer fluids provide thermal stabilization of the heat transfer gas with an accuracy of no less than ± 0.15 ° C while controlling heat transfer intensity within 5-90% of the maximum heat flow with an accuracy of ± 5% of its value .

F o rm u l a i z o b re n i

Claims (3)

1. Method of controlling heat transfer between liquid and gaseous heat-exchangers. limited heat exchange surfaces and interacting with each other through a dielectric intermediate gas-liquid coolant circulating between these surfaces, by periodically affecting the heat exchange surface between the intermediate and gaseous heat transfer fluids by an electric field, in order to ensure thermal stabilization of the gaseous heat transfer fluid while simultaneously increasing the accuracy controlling heat transfer in the vertical position of the heat exchange surface dy gaseous and washed zhu- precise heating medium E, the intermediate heat transfer fluid circulating is carried out along the heat exchange surface with a liquid coolant by periodically subjecting it to an additional electric field measured value deviations of the temperature of the gaseous coolant from the temperature of thermal stabilization, and the impact of the main field is carried out to ensure dispersion of the liquid phase of the intermediate coolant, and the periods of action of this field are chosen within the periods of the additional field, and its intensity is directly proportional to the value of the specified deviation of the temperature of the gaseous coolant. 2. A device for regulating heat transfer between liquid and gaseous heat transfer fluids, comprising a housing with a tray filled with a dielectric intermediate gas-liquid coolant and heat exchangers located in the housing for heat exchange between the intermediate on the one hand and the liquid and gaseous heat transfer fluids on the other hand, and the heat exchanger for intermediate and gaseous heat transfer fluids is equipped with an electrode connected to an electric field source, characterized in that, in order to ensure thermal stabilization of the heat transfer gaseous flow while maintaining the heat transfer surface between gaseous and intermediate heat carriers, the heat exchanger for intermediate and liquid heat carriers is made like a pipe in a pipe, in the inner of which is placed electrohydrodynamic pump connected to the source of an additional electric field and equipped with a suction nozzle, worn in the liquid phase of the intermediate coolant, and on. the discharge pipe and the heat exchanger for the intermediate and gaseous coolants are made in the form of vertically mounted finned cylinders with the upper ends shut off; The electrode is located in the internal cavity of each cylinder along its axis and is made in the form of a perforated pipe connected to the lower end of the discharge pipe, and at the upper end of the spreading valve with an annular horizontal slot for the passage of the intermediate fluid coolant. 3. Pop-2 device, characterized in that, in order to reduce the influence on its operation, the position in the field of gravity, the space between the casing and the heat exchangers is additionally filled with degassed dielectric fluid. -1 l tsa On 31 M at FI.5 figl r-r 12