JPS5825949B2 - Multiple effect absorption refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-effect absorption refrigerator that uses water as a refrigerant and uses an aqueous salt solution such as lithium bromide as an absorption liquid.

Generally, in dual-effect absorption refrigerators, the refrigerant vapor generated when heating and concentrating the absorption liquid in the high-temperature regenerator on the high-pressure side is used to heat and concentrate the absorption liquid again in the low-pressure side low-temperature regenerator. However, for safety reasons, the pressure of the high-temperature regenerator is kept at a vacuum state of about 0.9 ata, and the low-temperature regenerator heated by the refrigerant vapor generated from the high-temperature regenerator is used for economical absorption. The concentration range of the liquid is approximately 60.5% ~
It is said to be around 62.5%.

On the other hand, the higher the concentration of the concentrated absorption liquid supplied to the absorber, the stronger the absorption capacity, but there is a problem of crystallization below the well-known solubility curve, so it is generally said that about 64% to 65% is preferable.

However, in conventional dual-effect absorption refrigerators, the dilute absorption liquid from the absorber with the lowest pressure is passed from the first heat exchanger (low temperature side) to the second heat exchanger (high temperature side) to increase the pressure. The refrigerant is supplied to a high-temperature regenerator at a high temperature, heated to an absorption liquid temperature at which the refrigerant can evaporate, and concentrated to about half its concentration.
This concentrated intermediate concentration absorption liquid is introduced into a low-temperature regenerator through a second heat exchanger, that is, a high-temperature heat exchanger, and in this low-temperature regenerator, the remaining half is heated and concentrated using refrigerant vapor generated from the high-temperature regenerator. A refrigeration cycle is used in which the refrigeration cycle is circulated through one heat exchanger, that is, a low-temperature heat exchanger, and then to an absorber.

Therefore, the concentration of the concentrated absorption liquid supplied to the absorber is approximately 62.
It is unsatisfactory at about 5%, and the concentration of the concentrated absorption liquid is about 6%.
This required a significantly larger absorber heat transfer area compared to a single-effect absorption refrigerator, which can increase the heat transfer area to about 4.5%.

Furthermore, on the concentrated absorption liquid side of the low temperature heat exchanger, there is a slight pressure difference ( Approximately 0.
Since the allowable flow path resistance is limited due to the fact that the concentrated absorption liquid is flowed using approximately 1 kgA-n￥, it is necessary to slow down the internal flow velocity of the heat exchanger, which results in poor heat transfer performance and large size. required a heat exchanger.

Therefore, the applicant of the present application previously proposed in Japanese Patent Application No. 126979/1987 that the absorber was constructed by increasing the absorbent concentration while maintaining the internal pressure conditions exactly the same as those of the conventional dual-effect absorption refrigerator. We are proposing a multi-effect absorption refrigerator that is compact and has a high internal resistance of each low-temperature and high-temperature heat exchanger, thereby increasing the internal flow velocity and reducing the size of each heat exchanger.

In other words, this multi-effect absorption refrigerator concentrates the dilute absorption liquid sent from the absorber by the dilute absorption liquid pump to an intermediate concentration in the low-temperature regenerator, and then concentrates the dilute absorption liquid sent from the absorber by the dilute absorption liquid pump to an intermediate concentration in the low-temperature regenerator. The absorbent liquid is concentrated to a high concentration in a high-temperature regenerator, and this highly concentrated absorbent liquid is circulated to the absorber.

Therefore, it has become possible to reduce the size of absorbers, low-temperature heat exchangers, and high-temperature heat exchangers to a certain extent, but they have their own limits and cannot be said to be fully satisfactory from the standpoint of resource and energy conservation. .

This invention has been made in consideration of the above-mentioned viewpoint, and instead of sending all of the intermediate concentration absorption liquid from the low temperature regenerator to the high temperature regenerator, a part of the intermediate concentration absorption liquid is sent from the high temperature regenerator to the absorber. By bypassing the liquid circulation system and providing a flash chamber upstream of the high-concentration absorption liquid circulation system, the high-temperature, high-pressure high-concentration absorption liquid is concentrated and cooled by self-evaporation due to pressure reduction, that is, the liquid temperature is lowered. At the same time, the concentration is increased, eliminating the need for a high-temperature heat exchanger, and simplifying the structure by further downsizing the absorber and low-temperature heat exchanger, reducing the amount of expensive absorption liquid held. It is also advantageous in terms of low cost.

The present invention will be explained below with reference to embodiments shown in the accompanying drawings.

In FIG. 1, 14 is an evaporator, and pipes (not shown) are regularly arranged in the evaporator 14, fixed to tube holes in tube sheets at both ends of the body 13 with expansion bands, etc., and connected to each other via headers. An evaporator tube group 14a in which cold water to be cooled flowing in and out flows inside, and refrigerant flows down on the outer surface of the tubes.
A distribution device 17 for uniformly distributing refrigerant onto the evaporator tube group 14a is housed above the distribution device 1.
A partition plate 31 is provided above the cylinder 13 over the entire length of the cylinder 13, thereby dividing the inside of the cylinder 13 into an upper high-pressure side and a lower low-pressure side.

The absorbers 15 below the evaporator 14 are arranged regularly and fixed to the tube plates at both ends of the shell 13 in the same manner as described above, and cooling water flowing in and out through pipes (not shown) flows inside the absorbers 15, so that absorption liquid is formed on the outer surface of the pipes. A downstream absorber tube group 15a and a distribution device 18 above the absorber tube group 15a that uniformly distributes the absorbent liquid onto the absorber tube group 15a.
is stored.

Since the interior of the shell 13 is maintained at a high degree of vacuum on both the high-pressure side and the low-pressure side, the liquid refrigerant flowing down the tube surface of the evaporator tube group 14a evaporates at a low temperature, and the fluid inside the tubes passes through the tube wall. to the required low temperature.

Therefore, this fluid, primarily water, is directed to cooling, industrial, and other various cooling applications.

The unevaporated refrigerant flows down from the lowest end of the evaporator tube group 14a into the refrigerant reservoir 32, exits the liquid outlet 33, passes through the pipe line 23 by the refrigerant pump 22, and returns to the distribution device 17, and this operation is repeated. .

The evaporated refrigerant vapor is separated into droplets by an eliminator (not shown) provided in the passage, and is immediately absorbed by the absorption liquid flowing down the tube surface of the absorber tube group 15a, so that the refrigerant evaporates actively and continuously. It will be done.

The dilute absorption liquid that has absorbed refrigerant vapor and lost its absorption capacity is in the shell 13.
The diluted absorbent liquid is pumped up from the diluted absorbent reservoir 19 in the lower part by the diluted absorbent pump 20 to the low temperature regenerator 1 via the low temperature heat exchanger 7 provided in the conduit 9 and through the conduit 10 .

The low-temperature regenerator 1 is filled with absorption liquid until it maintains a predetermined liquid level, and is heated by refrigerant vapor, which will be described later, flowing inside the low-temperature regeneration container tube group 1a, and first reaches a concentration of about half the operating concentration condition, that is, an intermediate concentration. The refrigerant vapor that is concentrated and evaporated by this concentration flows into the condenser 16 through the eliminator 26, which serves to separate droplets containing the absorption liquid, and coolant water is supplied from the outside through a pipe (not shown). contacts the outer surface of the regularly arranged condenser tube group 16a passing through the inside,
Condenses and drips.

The refrigerant condensed inside the low temperature regenerator tube group 1a flows through the pipe line 12 onto the partition plate 25 provided below the condenser tube group 16a of the condenser 16, and the pipe surface of the condenser tube group 16a flows into the condenser 16. Mix with the refrigerant condensed above and dripped.

This refrigerant passes through the pipe line 24, joins with the refrigerant passing through the pipe line 23, and is returned to the distribution device 17.

On the other hand, the intermediate concentration absorption liquid, which is concentrated by evaporation and separation of the refrigerant in the low temperature regenerator 1, is pumped up to the high temperature regenerator 4 via the conduit 3 by the intermediate concentration absorption liquid pump 21 provided in the conduit 2.

The high-temperature regenerator 4 is filled with intermediate concentration absorption liquid until a predetermined liquid level is maintained, and in this example, combustion gas is used as the heating medium. A heat transfer tube group 28 is arranged above as a passage for the combustion gas generated in the combustion chamber 29, but this combustion chamber is abolished and steam, high temperature water, and combustion gas are introduced into the heat transfer tube group 28 from the outside. When the intermediate concentration absorption liquid is heated and boiled by the heat of these heating media, Sagi's low-temperature regenerator 1
A portion of the unevaporated refrigerant at is evaporated, increasing the concentration by half.

When this evaporated refrigerant vapor passes through the eliminator 30, it separates droplets containing the absorption liquid, and passes through the pipe 11 to the low temperature regenerator 1.
flows into the regularly arranged pipes of the low temperature regenerator 1 1a.

On the other hand, the absorbed liquid concentrated to a high concentration in the high-temperature regenerator 4 flows out from the high-temperature regenerator 4, and in the conventional method, high-temperature heat is exchanged by the action of gravity and the internal pressure difference between the high-temperature regenerator 4 and the absorber 15. through a low temperature heat exchanger to an absorber 15, i.e.
It flows into the distributing device 18 above the absorber tube group 15a and drips onto the tube surface of the absorber tube group 15a to perform an absorption action.

In the present invention, a flash chamber 35 is provided in the circulation system of the high concentration absorbent liquid returned from the high pressure regenerator 4 to the absorber 15, whereby the high temperature and high pressure high concentration absorbent liquid is depressurized and cooled by self-evaporation, and then flashed. A portion of the intermediate concentration absorption liquid sent from the low temperature regenerator 1 to the high temperature regenerator 4 is bypassed to the downstream side of the chamber 35.

That is, the high concentration absorption liquid from the high temperature regenerator 4 is transferred to the absorber 1.
In the flash chamber 35 provided between the pipes 5 and 6 on the way to the refrigerant 5, the amount of heat required to evaporate a predetermined amount of refrigerant from the high concentration absorption liquid is reduced due to the self-evaporation effect, and the liquid temperature is lowered. At the same time, the concentration increases.

The heat of the refrigerant vapor generated in the flash chamber 35 is removed to the outside of the apparatus via the condenser 16 through the pipe 36 and the low-temperature regenerator 1.

The high-concentration absorbent liquid, which has increased in temperature and concentration after flowing into the pipe line 6 from the flash chamber 35, is passed between the pipes 2 and 3, which sends the intermediate-concentration absorbent liquid from the low-temperature regenerator 1 to the high-temperature regenerator 4. The intermediate concentration absorption liquid flows into a branch pipe 34 branched from the suction side pipe 2 of the intermediate concentration absorption liquid pump 21 provided, or from a branch pipe (not shown) branched from the discharge side pipe 3. The mixed liquid is sent from pipe 6 through low-temperature heat exchanger 7 and pipe 8 to distribution device 18 in absorber 15, and is dripped onto the pipe surface of absorber pipe group 15a to perform an absorption action. be.

As with the conventional method, the refrigeration load fluctuates and the evaporator tube group 1
When the temperature of the cold water flowing out from 4a through the pipe changes from a predetermined value, the temperature detector installed at the cold water outlet detects this, and the temperature controller operates, reducing the supply amount of heating fuel, steam, other high-temperature water, etc. The amount of refrigerant vapor evaporated in the high-temperature regenerator 4 is controlled by operating a control valve that adjusts the amount of refrigerant vapor to obtain a refrigerating capacity corresponding to the refrigerating load and at the same time keep the chilled water temperature constant.

For example, when the cold water temperature is high, the absorption liquid concentration is raised and lowered, and when the cold water temperature is low, the absorption liquid concentration is diluted and the absorption capacity is weakened, which slows down the evaporation effect. It works to make it higher.

In addition, depending on the case, a flow control valve may be provided in each of the pipe 9 provided with the dilute absorption liquid pump 20 and the pipe 3 provided with the intermediate concentration absorption liquid pump 21, so that the supply amount of fuel for heating, etc. can be adjusted at the same time, respectively. It is also possible to adjust the circulation amount of the absorption liquid to increase the refrigeration efficiency at partial load, or to balance the flow rate of the defined liquid collection pump.

The refrigeration cycle diagram of the refrigerator of the present invention constructed as described above is qualitatively shown in FIG.

That is, if we take the saturated vapor pressure P of the absorption liquid on the vertical axis and the absorption liquid concentration ξ1 to ξ5 on the horizontal axis, the temperature and concentration decrease during the absorption process while passing from the absorber 15 through the low-temperature heat exchanger 7. The diluted absorption liquid is heated and changed from 9 to 10 points, then enters the low temperature regenerator, heated to its saturation point and changed from 10 to 1, and further heated and concentrated in the low temperature regenerator 1. , its density increases by half and moves from point 1 to point 2, resulting in the density of ξ2.

The intermediate concentration absorption liquid having a concentration of ξ2 is pressurized by the intermediate concentration absorption liquid pump 21 from the two exit points of the low temperature regenerator 1, enters the high temperature regenerator 4 through a pipe, and is heated, and is heated to the saturation temperature state 4 from the third point. Reach the point.

The refrigerant that is further heated in the high temperature regenerator 4 is concentrated to more than half the concentration ξ3 by evaporation of the refrigerant, becomes an absorbent liquid with a high concentration ξ4, moves from point 4 to point 5, and passes through the pipe from the outlet of the high temperature regenerator 4. On the way to the flash chamber 35, the temperature of the liquid decreases due to self-evaporation due to reduced pressure, and at the same time it becomes concentrated, becoming an absorbing liquid with a high concentration ξ5, and moves from point 5 to point 6.

The high-concentration absorbent flowing into the pipe 6 from the flash chamber 35 bypasses part of the intermediate-concentration absorbent sent from the low-temperature regenerator 1 to the high-temperature regenerator 4 through the branch pipe 34 on the way, and is merged with the high-concentration absorbent as described above. It is diluted to the required concentration ξ3.

On the other hand, the bypass intermediate concentration absorption liquid merges and mixes -
2 and 6 to 7 respectively.
Moving on to the point, while the high-concentration absorption liquid of these mixed liquids passes through the low-temperature heat exchanger 7, it exchanges heat with the dilute absorption liquid sent from the absorber 15 to the low-temperature regenerator 1, giving it heat and lowering its temperature. Changed from 7 to 8 points.

Points 8 to 9 indicate changes in the pressure and concentration of the absorption liquid during the absorption process in the absorber 15.The concentrated absorption liquid entering the absorber 15 is cooled by cooling water flowing through the tubes of the absorber tube group. By absorbing the refrigerant vapor from the evaporator 14 as it flows down the pipe surface, the concentration decreases to ξ1 and accumulates in the absorption liquid reservoir 19 at the bottom.

At the same time, the temperature also drops. As is clear from the description of the embodiments above, according to the configuration of the present invention, a flash chamber is provided in the high-concentration absorbent circulation system that returns from the high-temperature regenerator to the absorber. is not necessary,
Furthermore, the high-concentration absorbent liquid can be condensed by self-evaporation due to reduced pressure, and at the same time can be cooled.The intermediate-concentration absorbent liquid is supplied from the downstream side of the flash chamber provided in the high-concentration absorbent circulation system and from the low-temperature regenerator. Since a branch pipe is provided that communicates with the suction side or discharge side of the intermediate concentration absorption liquid pump installed in the pipe that sends the liquid to the high-temperature regenerator, it is possible to reduce the amount of circulation to the high-temperature regeneration system where heat loss is large. , and the refrigeration cycle efficiency can be greatly improved.

In addition, a part of the intermediate concentration absorption liquid is bypassed and flowed into the high concentration absorption liquid whose temperature has decreased and the concentration has increased from the flash chamber, and the mixed liquid is guided to the absorber through a low temperature heat exchanger. In the low-temperature heat exchanger section, where the temperature normally drops and concerns about crystals occur, the concentration is diluted to an appropriate level, eliminating concerns about crystals.

In addition, if the branch pipe is provided on the discharge side of the intermediate concentration absorption liquid pump, a larger pressure loss during low-temperature heat exchange can be tolerated, so the flow rate of the mixed liquid is increased, the heat transfer performance is improved, and the low-temperature heat exchanger is made smaller. This is extremely advantageous economically, since it is possible to reduce the amount of expensive absorbent liquid required.

Furthermore, since the dilute absorption liquid is first concentrated in the low-temperature side regenerator and the remaining concentration is performed in the high-temperature side regenerator, the concentration can be relatively increased compared to the conventional method, and the amount of high-temperature regeneration is itself In addition to being able to downsize the refrigerator, the entire refrigerator can also be significantly downsized.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing one embodiment of the present invention, and Fig. 2 is a system diagram showing an embodiment of the present invention.
It is a refrigeration cycle diagram of the figure. 1... Low temperature regenerator, 4... High temperature regenerator, 7... Low temperature heat exchanger, 14... Evaporator, 15...・Absorber, 16... Condenser, 19... Absorption liquid reservoir, 20... Dilute absorption liquid pump, 21... Intermediate concentration absorption liquid pump,
22...Refrigerant pump, 32...Refrigerant reservoir, 34...Branch pipe, 35...Flash chamber, 36...Pipe line .

Claims (1)

[Claims] 1. In a multi-effect absorption refrigerator that concentrates the dilute absorption liquid from the absorber to an intermediate concentration in a low-temperature regenerator, and concentrates the intermediate concentration absorption liquid to a high concentration in a high-temperature regenerator and circulates it to the absorber,
A flash chamber is provided in the high-concentration absorption liquid circulation system, and a part of the intermediate-concentration absorption liquid is bypassed downstream of the flash chamber, and the mixed liquid with the high-concentration absorption liquid is introduced into the inlet side of the low-temperature heat exchanger and the absorber is heated. A multi-effect absorption refrigerator characterized in that the refrigerant vapor self-evaporated in the flash chamber is guided to a low-temperature regenerator and sent to a condenser together with the refrigerant vapor generated in the low-temperature regenerator.