SU1747842A1 - Heat tube - Google Patents

Abstract

Usage: in heat engineering, in particular, heat exchangers, can be used as a heat exchanger in energy, process and heating installations and as a device for separating mixtures into separate components. SUMMARY OF THE INVENTION: A heat pipe is provided with a distributing device 9. installed above the bundle of evaporator tubes 11, a downstream steam pipe 17. connecting the sub-pipe chamber 16 of the evaporation beam 11 to the annular space of the condensation beam 1 and the transition chamber 19 of the primary heat carrier located under the bottom of the sub-pipe chamber 16 Heat pipe -the heat exchanger has a high efficiency in the field of low densities of heat flows from 2 to 40 kW / m2. 2 Il.

Description

The invention relates to heat engineering and in particular to heat exchangers in power, heat engineering and heating installations.

A vertical shell-and-tube regenerator is known, which contains a tube sheet and heat pipes fixed to it with evaporation and condensation sections, characterized in that in order to increase reliability, the pipe grid is made up of two parts, the upper and lower parts, in which, respectively, condensation and evaporation sections are fixed. heat pipes.

The known heat exchanger is characterized by shortcomings in the difficulty of removing non-condensing gases, the difficulty of controlling the filling of pipes with intermediate heat carrier, the relatively low heat transfer coefficients to the intermediate heat carrier, the difficulty of scaling the outer surface of the condensation sections of heat pipes due to the fact that

each heat pipe works as a single heat transmitter, and there is no organized movement of steam and condensate in the heat pipe

The closest to the proposed technical essence is a heat pipe-heat exchanger containing condensation and evaporation parts, consisting of pipes fixed in tube sheets and enclosed in a detachable body, characterized in that in order to increase heat production due to removal of non-condensing gases and organized flow of steam and condensate, as well as maintaining an optimal level of filling of the intermediate coolant, the condensation and evaporation parts are made of tube bundles separated from each other, bounded from both ends by two tube sheets, and the condensation and evaporating pipe bundles, together with the split housing, constitute a single heat pipe, under the condensation beam C

2

VI

00 4. U

A device for organized movement of steam and condensate flows, made in the form of a tray and a standpipe, is installed, and the detachable housing is equipped with a device for removal of non-condensable gases and a device for controlling the level and charging of heat exchange by an intermediate heat carrier.

However, this heat exchanger has a relatively low intensity of heat transfer to the intermediate coolant, and especially in the area of low heat flux densities q 2-40 kW / m2.

The purpose of the invention is to increase the intensity of heat transfer to the intermediate coolant when the heat exchanger is operating in the region of small heat fluxes from 2 to 40 kW / m2.

The goal is achieved by the fact that in a heat pipe - a heat exchanger containing condensation and evaporation parts, consisting of pipes fixed in tube sheets and forming a single heat pipe together with a detachable housing, a constructive solution is introduced, according to which evaporation of the intermediate heat carrier in the evaporation pipes occurs in the gravitationally-flowing down the play of fluid with the simultaneous descending motion of fluid and steam, while in L s

A heat exchanger is installed in the exchanger, causing the intermediate heat carrier to be uniformly fed to the evaporative beam pipes; a steam supply line through the steam supply pipe to the condensing beam pipes and a transitional heat transfer chamber

Since these distinctive features are absent in the known invention, the proposed technical solution meets the novelty criterion.

Using a switchgear, the intermediate heat transfer fluid is evenly distributed over the entire cross section of the evaporator tube from the stream of small diameter, defined by the diameter of the underwater pipe, to the stream of large diameter, determined by the diameter of the evaporation pipe bundle. A liquid uniformly distributed over the entire cross section of the tube bundle flows by overflow through the upper edge of the evaporator tubes in the form of a film along the inner surface. When heat is supplied from the primary coolant through the walls of the tubes, a boiling film of liquid flows. Thus, the switchgear serves to organize the process.

boiling of intermediate heat carrier in flowing film

In the absence of a switchgear, condensate will flow only.

in those pipes that are located near the underwater pipe, and the peripheral part of the pipes will not be irrigated with liquid. Moreover, the liquid enters the irrigated pipes irregularly - in one pipe more, in others

0 less. In this case, the heat output of the heat pipe-heat exchanger drops sharply (some pipes are not irrigated). The average intensity of heat transfer in pipes with a small amount of incoming

5 liquids also drastically decrease. This is due to the appearance of bare spots on the surface of the pipes. Such areas arise due to an insufficient amount of liquid to completely wet the surface, as well as due to its evaporation. Thus, the uniformity of pipe irrigation with liquid (condensate) with the help of a distributor increases the intensity of heat transfer.

5 The intensity of heat transfer increases not only because of the uniformity of pipe irrigation, but mainly due to the organization of the process of boiling the intermediate heat transfer medium in the flowing film. Increase

0 the intensity of heat transfer, especially in the area of small heat fluxes from 2 to 40 kW / m2, is confirmed by the data shown in Fig. 1

The evaporation of solutions in pipes in a gravitational-flowing film of liquid with a simultaneous descending movement of liquid and steam is carried out in evaporators with a flowing film of liquid. Existing heat exchanger designs

0 composed of individual heat pipes (thermosyphons) do not allow organizing such a boiling regime in addition.

A switchgear consisting of a pipe with a valve of a distribution tank with a perforated bottom and inclined fender plates ensures the uniformity of supply of the intermediate heat carrier to the upper ends of the evaporator tubes. The distribution tank and the slanting inclined plates are included in the bidet of elements in the distribution device used in evaporators with a flowing film of liquid. Compared switchgears have

5 significant differences. Thus, in the proposed design, the internal volume of the distribution tank does not contain any structural elements, since the circulation of the intermediate heat transfer medium occurs in a confined space and in

the coolant does not have large mechanical inclusions, while concentric partitions, a blower device, a conical bottom, are installed to remove mechanical inclusions in the tank of the evaporator switchgear. In addition, in the proposed design, the intermediate coolant is distributed, and in the evaporator the vial solution (secondary coolant) is liberated. At the same time, the switchgear in the proposed design, together with the transition chamber and the overflow steam line, serves to organize the process of boiling the intermediate coolant in the gravitationally flowing liquid with the vapor.

The overflow steam line connects the evaporative and condensation parts of the heat pipe-heat exchanger. It does not have a direct effect on the increase in the intensity of heat transfer, however, in the absence of a flow-through steam pipe, the heat exchanger will not work, since the circulation circuit of the heat pipe is broken.

Depending on the heat load of the heat exchanger, the intermediate heat transfer medium in the evaporator tubes may not be completely evaporated. Steam and liquid after the evaporator tubes enter the sub-tube chamber. Then the steam parallel to the steam line is directed to the condensation tube bundle, and non-evaporating liquid remains on the bottom of the subtubular chamber. The steam in the condensation bundle condenses and the condensate enters the reflux of the upper ends of the evaporator beam tubes, while as part of the liquid remained on the bottom of the under-cavity chamber. As a result, the density of the reflux pipe of the evaporative bundle is reduced. Irrigation density is the ratio of fluid flow to irrigated perimeter (kg / d). Research has shown that with increasing density of irrigation, heat transfer intensity increases and vice versa. Therefore, in order for the heat transfer rate not to decrease, it is necessary to evaporate the liquid remaining on the bottom of the chamber. For this purpose, the primary coolant is passed through the transition chamber and, due to the transfer of heat through the bottom wall, produces additional evaporation of the liquid, then all the intermediate heat carrier vapor enters the condensation part.

FIG. Figure 1 shows the dependence of the heat transfer coefficients on the heat flux density with different ways of organizing the intermediate heat carrier boiling.

Curve 1 corresponds to the boiling process in individual thermosyphons. An empirical equation was used to calculate it.

, GG P0,5. p 0.22 AND- With q G

(D

where c is a constant coefficient for calculated conditions. from 12;

q is the heat flux density, W / m2;

PH - saturation pressure, bar.

Curve 2 corresponds to the boiling process in the pipes. To calculate it, the Kichizhna-Tobilevich equation was used.

and az q

0.6

(2)

where A2 is a constant factor, for water A2 12.4.

Curves 3 and 4 correspond to the process of boiling in a liquid film flowing in conjunction with a vapor at irrigation densities of 0.2 and 1.85 kg / (m s), respectively. They postrbeny on experimental data.

The analysis of the location of the curves in FIG. Figure 1 shows that in the region of low heat flux densities q 2-40 kW / m2, the organization of the boiling process in a liquid film flowing together with vapor allows an increase in the intensity of heat transfer. Curves 3 and 4 in this region are much higher than curves 1 and 2.

Due to such an implementation of the heat pipe of the heat exchanger, an increase in the intensity of heat transfer in the region of small heat fluxes is provided, which, when the heat exchanger is implemented, will allow an increase in its heat production to be achieved.

Thus, in the proposed design, new properties appear that do not coincide with the properties of the known solutions, which leads to the conclusion: the proposed technical solution meets the criterion of significant differences.

FIG. 2 shows a diagram of a heat pipe heat exchanger.

The heat pipe-heat exchanger consists of a bundle of horizontal condensation pipes 1 and its tube sheets 2, enclosed in the housing 3 on which the device for removing non-condensing gases 4 is located and controlling the level of intermediate heat carrier 5, the end ends of the housing are closed with lids fitted

The inlet 6 and outlet 7 of the secondary heat carrier, a distribution device installed under the condensation body, consisting of an underwater pipe with a valve 8, a tank 9 with a perforated bottom and blunt inclined plates 10, a distribution device located above the beam of evaporating pipes 11 and its tube sheets 12 enclosed in the housing 13 to which the elbow 14 and the outlet pipe of the primary heat carrier 15 are attached, under the evaporator tubes, the sub-chamber 16 is located, the space of which is connected chnym steam pipe annulus 17c of the condensing tube bundle sub Tubular chamber 18 through the bottom bordered with transition chamber 19 for housing a primary heating medium pipe 20 is set input.

Heat pipe heat exchanger works as follows

A part of the annular space of the condensation bundle of pipes 1 is filled through the device 4 with an intermediate heat carrier. The filling level is controlled by the device 5, both during refueling and during operation of the heat exchanger. Intermediate coolant from the annular space through the pipe with valve 8 enters the tank 9 with a perforated bottom Rows in the bottom are arranged Rows An intermittent heat carrier is installed in each row Intermediate heat carrier flows out of the tank by the streams falling on the baffle plates 10, is reflected from them and in the form of a flat thin film is directed to the evaporator tubes 11 and the upper tube sheet 12 Generating a captive and liquid occurs by overflowing through the upper edge of the pipe, and inside it under the action of surface tension forces. Intermediate coolant flows down the inner surface of the evaporator tubes and evaporates due to the heat perceived through the walls of the evaporator tubes from the primary coolant. The resulting vapor together with the liquid film enters into the piped chamber 16. The wall of the casing 3 of the condensation beam and the liquid in the tank 9 and the pipe with the 8 V valve of the sub-pipe chamber prevent upward movement of the vapor. the vapor separates from the non-evaporated liquid. The vapor flows through the overflow steam line 17 to the condensation tube 1 and condenses on the outer surface of these tubes, giving the heat of condensation to the secondary coolant, which enters the heat exchanger through the inlet 6, passes inside the condensation tubes and leaves the apparatus through the nozzle 7. Condensate flows into the lower part of the housing 3 and through the pipe with

valve 8 enters the switchgear tank again. The remainder of the non-evaporating coolant is evaporated at the bottom 18. The primary coolant enters the transition chamber 19 through the nozzle 20, where part of the heat is spent on additional evaporation of the intermediate heat carrier located at the bottom 18, and then through knee 14 enters the inter-coarse evaporation pipe

and through the pipe 15 leaves the heat exchanger. When the primary coolant moves along the annular space, heat is transferred to the intermediate coolant flowing in the form

liquid films on the inner surface of the steam pipes. Thus, the heat from the primary coolant is transferred to the intermediate coolant and is spent on its evaporation, and the heat

from the intermediate coolant is transferred to the secondary coolant in the process of condensation of the vapor of the intermediate coolant non-condensable gases periodically, and if necessary constantly

discharging from the top of the condensation tube bundle through device 4

The economic effect resulting from the use of the proposed construction is due to the reduction in

metal intensity of the heat exchanger

Claims (1)

Invention Formulation Heat pipe containing a detachable body in which a condensation housing and located under it are placed evaporative parts consisting of tube bundles; fixed in tube sheets and devices for removal of non-condensable gases and control of the level of intermediate coolant that, in order to intensify the heat exchange by organizing the process of boiling the intermediate coolant in a graphitically flowing liquid film with vapor, it is additionally equipped a distribution device installed above the evaporator tube bundle and a transfer vapor pipe connecting the sub-tube chamber that is additionally installed under the tube tube of the evaporative part with the annular space of the tube bundle of the condensation part and the transition chamber of the primary heat carrier, additionally located under the bottom of the sub-tube chamber 5 6 7 to 9 10 1 Fi, i 3 4 5 6 7 6 S 10 20 four / FIG. t