JPS5934956B2 - Evaporators used in hot water heat recovery systems, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an evaporator used in a hot water heat recovery system, more specifically, an evaporator for recovering heat from hot water to evaporate a cycle medium in a heat pump system, a Rankine cycle system, etc. Regarding the evaporator used.

Energy resources are extremely valuable and must be used as efficiently as possible.

In recent years, many systems for the use of so-called low-density energy such as solar heat and geothermal heat and for the recovery and use of waste heat energy have been proposed, and research and development of these systems is progressing.

For example, heat can be recovered from hot wastewater and used in heat pumps.
A method of raising the temperature by a system to obtain a high-temperature heat source that is easy to use, and a Rankine cycle that recovers heat from geothermally heated hot water or hot waste water and uses refrigerants such as fluorocarbons and ammonia as a medium.・This includes methods of generating electricity using a system.

In these systems, an evaporator is used to evaporate the cycle medium using hot water as a heat source.

Since these systems do not have a large overall effective temperature difference, a large heat transfer temperature difference in the evaporator will result in a decrease in system efficiency.

However, since it is generally required to increase the efficiency of the system as much as possible, it is necessary to reduce the heat transfer temperature difference in the evaporator used. Consequently, there is a problem in that equipment costs are high.

In addition, hot water often contains dissolved or suspended corrosive substances and scale-forming substances, and when such hot water is used, the cycle medium may leak due to corrosion of the heat transfer tubes or scale may form on the surface of the heat transfer tubes. There is a problem in that the effectiveness of the system or the reliability of the system decreases due to problems such as a decrease in heat transfer efficiency due to adhesion.

As this type of evaporator, a so-called flooded evaporator as shown in FIG. 1 has conventionally been used.

In the figure, 1 is a horizontal casing, and 2 is a hot water inlet/outlet chamber provided at one end of the casing, which is divided by a horizontal partition plate 3 into a lower hot water introduction section 4 and an upper hot water discharge section 5.

Reference numeral 6 denotes a hot water storage chamber disposed near the other end of the casing 1, and this is connected to a hot water introduction section 4 and a hot water discharge section 5 of the hot water inlet/output chamber 2 by a plurality of horizontal heat transfer tubes 7. .

Therefore, the high temperature hot water introduced into the hot water introduction part 4 from the hot water inlet 8 passes through the lower horizontal heat exchanger tube 7, turns upward in the hot water storage chamber 6, and passes through the upper horizontal heat exchanger tube T.
The hot water discharge section 5 is reached.

While the hot water passes through the upper and lower heat transfer tubes 7, it exchanges heat with the cycle medium in the casing 1, becomes low-temperature hot water, and is discharged from the hot water outlet 10.

Reference numeral 11 indicates a cycle medium liquid inlet provided on the lower wall of both ends of the casing 1, and 12 indicates a cycle medium gas outlet provided on the earthen wall of the other end of the casing 1.

In such conventional evaporators, when the cycle medium is a refrigerant, when the heat transfer temperature difference is small, the heat transfer rate often becomes small. is used to expand the heat transfer area, but there is a problem in that the equipment cost increases accordingly.

Further, since the hot water is caused to flow directly through the horizontal heat transfer tubes T, there is a problem that if the hot water contains corrosive substances, the hot water may leak into the cycle medium due to corrosion of the horizontal heat transfer tubes 7.

Furthermore, if the hot water contains scale-forming substances, scale will form inside the horizontal heat exchanger tubes T.

If such scale is left unattended, problems such as a decrease in heat transfer efficiency will occur, so either stop the system operation or switch to a spare evaporator of the same capacity.
Need to remove scale.

Therefore, it is very uneconomical, and especially when a spare evaporator is installed, the equipment cost will be about twice as high.

The use of conventional flooded evaporators thus reduces the effectiveness and reliability of the system.

This invention was made in order to solve the above-mentioned problems of the prior art. Hot water is flash-evaporated in a reduced pressure evaporator section, and the resulting steam and the cycle medium flowing in the heat transfer tubes exchange heat. Provided is an evaporator in which the hot water does not come into contact with the heat transfer tubes at all, and therefore no troubles arise due to the corrosive or scale-forming substances contained therein, ensuring the effectiveness and reliability of the system. The purpose is to

This invention will be described below with reference to embodiments shown in the drawings.

Note that this example shows an evaporator used in a heat pump system.

In FIG. 2, 21 is a vertical casing, 22 is a hot water inlet provided at the top of the casing 1, 23 is a hot water inlet opened on one side of the casing 1, and 24 is a casing 21
The cycle medium gas-liquid separation sections 26 are arranged in three rows in the vertical direction below the hot water introduction section 22, and are arranged next to the hot water introduction section 22 at the top of the section with a vertical partition plate 25 interposed therebetween. The provided hot water evaporator is divided by a perforated horizontal partition plate 27 having a plurality of water passage holes 28 and a vertical partition plate 26 provided with a demister 30, respectively.

31 is an upper horizontal partition plate 27 in each hot water evaporating section 26;
A baffle plate 32 is installed in a drooping manner, and 32 is a hot water outlet provided at the lower end and side of the lowermost hot water evaporator 26.
33 extends vertically below the cycle medium gas-liquid separation section 24.
A condensing section arranged in stages, including a tube plate 34 arranged at the same level as the perforated horizontal partition plate 27, and a vertical partition plate 29 provided with the demister 30.
The condensing section 33 of each stage communicates via the demister 30 with the hot water evaporating section 26 of the corresponding stage arranged at approximately the same level.

Reference numeral 35 denotes a cycle medium introduction section provided below the lowermost condensing section 33, and a cycle medium introduction port 36 is opened in the lower wall of this section.

37 is a plurality of vertical heat exchanger tubes 38 provided linearly passing through each condensing section 33 so as to communicate the cycle medium introduction section 35 and the cycle medium gas-liquid separation section 24;
39 is a demister disposed above the baffle plate 38 in the separation section 24, and 40 is a cycle medium provided on the top wall of the separation section 24. Steam outlet, 41 is the same separation part 24
A cycle medium liquid return port provided on one side, 42 a return cycle medium liquid inlet port provided on one side of the cycle medium introduction section 35, and 43 a return port 41 for these cycle medium liquids.
a cycle medium liquid return pipe 44 communicating with the inlet 42;
are condensed water collection pipes installed to connect the lower end and the upper end of the vertically adjacent condensing sections 33, each with a valve 4.
5.

Reference numeral 46 indicates a condensed water outlet provided at the lower end of the lowermost condensing section 33, and 47 indicates a non-condensable gas exhaust pipe connected to one side of each condensing section 33, each having a valve 48. ,
The discharge pipes 47 are combined into one and connected to a vacuum pump (not shown).

The vacuum pump maintains the hot water evaporating section 26 and condensing section 33 in each stage at a predetermined reduced pressure state.

49 is a cycle medium supply pipe connected to the cycle medium inlet 36, and 50 is an expansion valve interposed in the middle of this pipe.

In the above, first, hot water at temperature Twi is supplied to hot water inlet 2.
3 into the hot water introduction section 22 at the top of the casing 21, and then passes through a large number of water holes 28 in the perforated horizontal partition plate 27 and flows downward into the first hot water evaporation section 26.

The inside of this hot water evaporator 26 is reduced to a pressure P□,
Part of the hot water undergoes flash evaporation to generate steam at a temperature TSI, and the hot water itself is cooled to a temperature Tw1 (T Sl
”TWI).

The hot water at the temperature Tw□ accumulated at the bottom of the first hot water evaporator 26 flows down through the water passage holes 28 of the perforated horizontal partition plate 270 into the next second hot water evaporator 26.

In addition, the steam generated in the first hot water evaporator 26 is transferred to a demister 30.
is guided into the corresponding first condensing section 33, contacts the vertical heat exchanger tube 37, and condenses.

The hot water at the temperature Tw1 accumulated at the bottom of the first hot water evaporator 26 flows down through the water passage holes 28 of the perforated horizontal partition plate 270 into the next second hot water evaporator 26.

The inside of this second hot water evaporator 26 is maintained at a pressure P2 (P2 P□), steam at a temperature TS2 is generated here, and the hot water is cooled to a temperature TW2 (T 82 "TW2").
, accumulates at the bottom.

The steam is then guided to the corresponding second condensing section 33 and condensed, and the hot water flows down into the third hot water evaporating section 26 from the water passage hole 28 of the perforated horizontal partition plate 2T.

The inside of this third hot water evaporator 26 is maintained at a pressure P3 (P3 - P2), steam of hot water 'I'' 83 is generated here, and the hot water is cooled to a temperature Tw3 (Ts3ヱTW3).
Collects at the bottom.

The steam is then guided to the corresponding third condensing section 33 and condensed, and the hot water is discharged from the hot water outlet 32.

Note that the hot water evaporating section 26 and the condensing section 33 of each stage are maintained at different predetermined reduced pressure states, but this can be done by appropriately adjusting the opening degree of the valve 48 of the non-condensable gas exhaust pipe 47 corresponding to each stage. It is done by

Further, the hole diameters of the plurality of water passage holes 28 of each perforated horizontal partition plate 27 are set in accordance with the pressure and hot water flow rate of the hot water evaporating section 26 of each stage.

On the other hand, in a heat pump system, the cycle medium is condensed at high temperature and high pressure in a condenser (not shown), so after passing through the expansion valve 50, part of the cycle medium undergoes flash evaporation and becomes a gas-liquid two-phase flow, which is then supplied to the cycle medium. It flows through the pipe 49 and is introduced into the cycle medium introducing section 35 .

The cycle medium then ascends through the plurality of vertical heat transfer tubes 37 and reaches the cycle medium gas-liquid separation section 24 while being heated by hot water vapor in the condensing section 33 of each stage.

The gas-liquid two-phase flow of the cycle medium ejected into the gas-liquid separator 24 is separated into gas and liquid by the baffle plate 38 and the demister 39, and the steam of the cycle medium is taken out from the outlet 40 to a predetermined portion of the heat pump system. sent to.

Further, the cycle medium liquid is returned to the cycle medium introducing section 35 through the return pipe, and rises within the vertical heat transfer tube 37 again.

The condensed water generated in each condensing section 33 sequentially flows down from the upper stage to the lower stage in the condensed water collection pipe 44, and then
The condensed water is discharged from the condensed water discharge port 46.

In this case, the opening degree of the valve 45 of each condensed water collection pipe 44 is adjusted as appropriate so as to maintain the differential pressure between the condensing sections 33 at each stage.

Note that the heat transfer area of the condensing section 33 of each stage is distributed in accordance with the pressure and hot water flow rate of each stage.

In the above embodiment, the gas-liquid two-phase cycle medium that has passed through the expansion valve 50 is directly introduced into the cycle medium introduction section 35, but for example, a separate gas-liquid separator may be installed.
The cycle medium in the gas-liquid two-phase flow after passing through the expansion valve 50 is once introduced into this gas-liquid separator, the vapor and liquid of the cycle medium are separated, and only the liquid is introduced into the cycle medium introduction section 35. You can do it like this.

Furthermore, in the above embodiment, an example of a heat pump system was shown, but in the case of a Rankine cycle system, for example, the cycle medium is condensed in a condenser at low temperature and low pressure, so after increasing the pressure with a medium circulation pump etc., the cycle medium is It will be introduced into the medium introducing section 35.

In this case, since the cycle medium is supplied in a so-called safe state relative to the evaporator operating pressure, it is necessary to partially preheat it in the evaporator.

Further, in the above embodiment, in order to reduce loss due to temperature difference, the hot water is flash-evaporated in three stages, and the steam is condensed according to the temperature and pressure of each stage. The number of stages of the condensing section 330 may be multiple stages, and can of course be arbitrarily selected.

Note that the plurality of vertical heat transfer tubes 37 may each be a single tube, but may be a so-called inner fin tube, a porous tube inside the tube, or a special heat transfer tube with vertical grooves on the outside of the tube and porous inside the tube. , and if special heat transfer tubes with vertical grooves inside and outside the tubes are used, the heat transfer efficiency will be very high.
Evaporators can be dramatically improved.

Further, in the above embodiment, a case is shown in which the rows of hot water introduction section 22 and hot water evaporation section 26 and the row of cycle medium gas-liquid separation section 24 and condensation section 330 are housed in one vertical casing 21. However, it is also possible to separate these rows from each other depending on the installation location of the evaporators, and to connect the corresponding hot water evaporating sections 26 and condensing sections 33 to each other through communication pipes.

As described above, the evaporator used in the hot water heat recovery system of the present invention is provided with the hot water introduction section 22 and the cycle medium gas-liquid separation section 24 side by side, and the hot water introduction section 2
A plurality of hot water evaporators 26 are arranged in the vertical direction below the cycle medium gas-liquid separator 24, and the same number of condensing sections 33 as the hot water evaporators 26 are provided below the cycle medium gas-liquid separating section 24. The hot water evaporation section 2 of each stage is provided to correspond to the
6 and the corresponding condensing section 33 are communicated with each other, and a demister 30 is provided in each communicating section, so that the hot water evaporating section 26 and the condensing section 33 of each stage are brought into a predetermined reduced pressure state, and the lowest stage A cycle medium introduction section 35 is provided below the condensing section of the , and a plurality of vertical heat transfer tubes 37 connecting this cycle medium introduction section 35 and the cycle medium gas-liquid separation section 24 are arranged in a straight line within each condensation section 33 . The high-temperature hot water introduced into the hot water introduction section 26 flows down sequentially through the hot water evaporation sections 26 in multiple stages, and the water vapor generated in the hot water evaporation sections 26 at each stage flows through the demister. 30 and is introduced into the corresponding condensing section 33 where the vertical heat exchanger tube 3
The condensed water generated in the condensing section 33 of each stage is sequentially transferred to the lower stage, and the cycle medium introduced into the cycle medium introducing section 35 is condensed by contacting the T, and the condensed water generated in the condensing section 33 of each stage is transferred to the lower stage, and the cycle medium introduced into the cycle medium introducing section 35 is transferred into the plurality of vertical heat exchanger tubes 37. The cycle medium rises while being heated from the outside by steam and reaches the inside of the cycle medium gas-liquid separation section 24, where the cycle medium is separated into steam and liquid, and the steam of the cycle medium is taken out from the cycle medium outlet 40. The hot water is flash evaporated in the depressurized hot water evaporator 26, and the resulting steam and the cycle medium flowing in the vertical heat transfer tubes 37 exchange heat. No contact.

Therefore, troubles caused by corrosive substances or scale-forming substances contained in hot water do not occur at all, and the effectiveness and reliability of the system can be ensured.

In particular, the cycle medium rising inside the vertical heat transfer tubes 37 becomes a gas-liquid two-phase flow, resulting in two-phase boiling heat transfer with a high flow rate, which strengthens the convection effect and reduces heat transfer resistance, so the heat transfer area This makes it possible to make the evaporator more compact by making it smaller, which reduces equipment costs accordingly.

In addition, since there is no trouble caused by corrosion or scale adhesion of heat exchanger tubes, etc., the trouble of repairing heat exchanger tubes and removing scale can be saved, and the maintenance and operating costs of the evaporator can be significantly reduced. As a result, the hot water heat recovery system can be implemented extremely economically.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal sectional view illustrating a conventional evaporator, and FIG. 2 is a schematic longitudinal sectional view illustrating an embodiment of the present invention. 21...Casing, 22...Hot water introduction section, 24...Cycle medium gas-liquid separation section, 26
...Hot water evaporation section, 27...Horizontal partition plate with holes, 28...Water holes, 29...Vertical partition plate, 30... ...Demister, 33...
Condensing section, 34... tube sheet, 35... cycle medium introduction section, 37... vertical heat exchanger tube, 39...
... Demister, 44 ... Condensed water collection pipe,
47...Noncondensable gas discharge pipe.

Claims (1)

[Claims] 1. A hot water introduction section 22 and a cycle medium gas-liquid separation section 24 are provided side by side, and a hot water evaporation section 26 arranged in multiple stages in the vertical direction is provided below the hot water introduction section 22. The same number of condensing sections 33 as the hot water evaporating sections 26 are provided below the section 24 so as to correspond to the hot water evaporating sections 26 of each stage, and the hot water evaporating sections 26 of each stage and the corresponding condensing sections 33 communicate with each other. At the same time, a demister 30 is provided in each communication section, and the hot water evaporating section 26 and condensing section 33 of each stage are brought into a predetermined reduced pressure state, and a cycle medium introducing section 35 is provided below the condensing section 33 of the lowest stage. established,
A plurality of vertical heat transfer tubes 37 connecting the cycle medium introduction section 35 and the cycle medium gas-liquid separation section 24 are connected to each condensing section 3.
The high-temperature hot water introduced into the hot water introduction section 26 flows down sequentially through the hot water evaporation sections 26 in multiple stages, and the hot water generated in the hot water evaporation sections 26 at each stage is The water vapor passes through the demister 30 to the corresponding condensing section 33.
The condensed water produced in the condensation section 33 of each stage is sequentially transferred to the lower stage, and the cycle medium introduced into the cycle medium introduction section 35 is The steam rises inside the plurality of vertical heat transfer tubes 37 while being heated from the outside and reaches the cycle medium gas-liquid separation section 24, where the cycle medium is separated into steam and liquid, and the steam of the cycle medium is separated into a sifter medium. An evaporator used in a hot water heat recovery system, etc., characterized in that it is taken out from an extraction port 40.