JP2000074521A - Absorption refrigerating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the coefficient of performance COP of an absorption refrigerating machine. SOLUTION: An evaporator 1 and an absorber 2 forming a double effect absorption cycle 10 are formed in a multistage. In a low pressure side absorber 14, absorbing solution of high concentration is used at relatively high temperature, so that the crystallization of absorbent can be avoided. In a high pressure side absorber 13, the concentration of the absorbing solution is relatively low, so that the concentration range from the inlet side to the outlet side of the whole part of the absorber 2 can be increased. If the temperature difference between the inlet side and the outlet side when cooling water is cooled by a cold and hot water pipe 15 from a high pressure side evaporator 11 to a low pressure side evaporator 12 is higher than rated 5 deg.C, the coefficient of performance COP can be more improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absorption refrigerator using water as a refrigerant and a substance having an absorption capacity such as lithium bromide.

[0002]

2. Description of the Related Art Conventionally, water has been used as a refrigerant, and a substance having an ability to absorb moisture such as lithium bromide (lithium bromide: LiBr) has been used as an absorbent. Absorption refrigerators that constitute a refrigerating cycle and perform freezing are widely used. In an absorption refrigerator using water as a refrigerant, it is possible to cool cold water, which is an object to be cooled, flowing through a heat transfer tube provided in an evaporator to about 7 ° C. An absorber is provided to absorb the water, which is the refrigerant evaporated by the evaporator, into the absorbent again, and a regenerator is provided to supply the absorber with a high concentration of the absorbent, and the refrigerant generated from the regenerator is provided. A condenser is provided to condense the vapor. These evaporators, absorbers, regenerators and condensers are the basic components of a single-effect absorption refrigerator. In order to increase the efficiency as an absorption refrigerator, a regenerator is divided into a high-temperature regenerator and a low-temperature regenerator, and a double-effect absorption refrigerator for improving thermal efficiency is also used.

FIG. 4 shows the relationship between the temperature of an absorbing solution and the solution concentration in a double effect absorption refrigerator. In FIG. 4, the larger the area of the hatched portion, the higher the coefficient of performance COP as a refrigerator. To increase the coefficient of performance,
Although it is conceivable to increase the difference between the concentration range of the solution, that is, the concentration on the inlet side of the absorber shown by, and the concentration on the outlet side of the absorber shown by, lithium bromide may crystallize on the high concentration side. There is. On the low concentration side, the concentration is determined by the solution temperature and the refrigerant temperature, and even if the concentration range is widened, the refrigerant absorption capacity does not improve. The solution concentration on the inlet side of the absorber is limited to 5%. Therefore, a technique has been known in which the combination of an evaporator and an absorber is provided in a plurality of stages, and the refrigerant temperature in the upper stage of the evaporator is increased to increase the concentration range.

The prior art of providing a combination of an evaporator and an absorber in a plurality of stages and widening the concentration range of the solution as shown in FIG. 5 is disclosed in JP-B-53-35662 and JP-B-53-35663.
And JP-A-49-103239. These prior arts disclose a basic configuration for dividing an absorber and an evaporator into a plurality of stages.

[0005]

In a double effect absorption refrigerator having a single-stage type absorber having a solution cycle as shown in FIG. 4, the cooling water inlet temperature is 32 ° C. and the cold water outlet temperature is 7 ° C.
Under the rated condition of ° C., the concentration width between the inlet and the outlet of the absorber is set to about 5 wt%. Therefore, the coefficient of performance COP is 1.
About 2. The COP at this time is (refrigeration capacity) / (actual regenerator heat input), and is defined as follows.
Since the coefficient of performance COP is related to the efficiency of the refrigerator, it is desired to improve it. However,
In a double-effect refrigerator with a single-stage absorber, the concentration range is about 5
If an attempt is made to increase the coefficient of performance COP by increasing the concentration to not less than wt%, the concentration of the solution reaching the inlet of the absorber becomes too large, and the absorbent may be crystallized. In addition, there is a problem that pressure and temperature increase in a high-temperature regenerator and a low-temperature regenerator.

As shown in FIG. 5, if the absorber is made into a multistage type, it is expected that the concentration range becomes large and the coefficient of performance COP is improved. However, in each of the above prior arts,
It does not specifically describe how to set the concentration range in order to improve the coefficient of performance COP.

An object of the present invention is to improve the coefficient of performance,
An object of the present invention is to provide an absorption refrigerator capable of increasing the efficiency as a refrigerator.

[0008]

SUMMARY OF THE INVENTION The present invention relates to an absorption refrigerator having water as a refrigerant and lithium bromide as an absorbent, wherein a combination of an absorber (2) and an evaporator (1) is provided in a plurality of stages. The absorption type wherein the concentration width, which is the difference between the concentration of the absorbing solution on the inlet side and the concentration of the absorbing solution on the outlet side, with respect to the entire plurality of absorbers (13, 14) exceeds 7.8 wt%. It is a refrigerator.

According to the present invention, a combination of the absorber (2) and the evaporator (1) is provided in a plurality of stages, and the plurality of stages of the absorber (1) are combined.
3, 14) By increasing the concentration range, which is the difference between the concentration of the absorbent on the inlet side and the concentration of the absorbent on the outlet side, the coefficient of performance COP can be increased. Multi-stage evaporator (11,
Since the refrigerant temperature can be changed in 12), in the high-pressure side evaporator (11), the refrigerant temperature rises and the solution concentration on the low temperature side decreases, so that the concentration range increases and the COP improves.

The present invention is further characterized in that the outlet temperature of the cooling water is 7 ° C. and the inlet temperature of the cooling water is 32 ° C.

According to the present invention, a high coefficient of performance COP can be obtained even when the chilled water outlet temperature is 7 ° C. and the chilled water inlet temperature is 32 ° C., which is a rated operation as a refrigerator. Even in the conventional absorption refrigerator, if these temperature conditions are increased, the coefficient of performance is increased, but it deviates from practical use conditions.

Also, the present invention provides a high-temperature regenerator (3), a low-temperature regenerator (4), a condenser (5), a high-temperature heat exchanger (6), and a low-temperature heat exchanger (3) as components of an absorption refrigeration cycle. 7)
And an absorbent pump (8), which constitutes a double-effect absorption cycle (10).

According to the present invention, the high-temperature regenerator (3) and the low-temperature regenerator (4) and the high-temperature heat exchanger (6) and the low-temperature heat exchanger (7) constitute a double-effect absorption cycle. Therefore, the low-temperature regenerator (4) uses the excess heat of the high-temperature regenerator (3) to further improve the coefficient of performance COP, as compared with the single-effect type in which the absorbent is concentrated by a single regenerator. Can be. At this time, a plurality of absorbers (13, 14)
When the concentration width, which is the difference between the concentration of the absorbent on the inlet side and the concentration of the absorbent on the outlet side, exceeds 7.8%, the coefficient of performance CO
P can be increased to 1.45 or more (FIG. 3).

In the present invention, the multi-stage absorber (13,
14) and the evaporators (11, 12) are characterized in that they are arranged vertically in such a manner that the lower stage has a higher evaporation pressure than the upper stage.

According to the present invention, a plurality of absorbers (13,
14) and the evaporators (11, 12) are arranged vertically, and the lower side has a higher evaporation pressure than the upper side. At the top,
The low pressure side absorber to which the highest concentration absorbent is supplied (4)
And a low-pressure side evaporator (12) having the lowest steam pressure. At the lowest stage, a high-pressure side absorber (13) and a high-pressure side evaporator (11) are arranged. Low pressure side absorber (1
From 4) to the high pressure side absorber (13), it is possible to move the absorbing liquid in a dropping manner, so that there is no need to provide a pump for transporting the absorbing liquid, and the number of pumps to be installed is reduced. Can be.

The present invention also relates to the above-described multi-stage evaporator (1).
1,12) The difference between the temperature on the outlet side of the cold water and the temperature on the inlet side of the whole exceeds 5 ° C.

According to the present invention, a plurality of evaporators (11,
12) Since the difference between the temperature of the outlet side of the cold water and the temperature of the inlet side exceeds 5 ° C, the temperature difference between the outlet side and the inlet side of the evaporator at each stage must be large. And the refrigerant temperature of the high-pressure side evaporator (11) can be raised.
In general, an absorption refrigerator is operated with the temperature difference between the inlet side and the outlet side of the cold water at the evaporator being 5 ° C. However, when the evaporator is composed of a plurality of stages, the temperature difference at each stage of the evaporator is different. Becomes small, the refrigerant temperature of the evaporator on the high pressure side does not rise, and the effect of the multiple stages is limited. If the temperature difference between the chilled water at the inlet and the outlet at the entire evaporator (11, 12) in the plurality of stages is made larger than 5 ° C., the temperature difference in each stage also becomes large, and the evaporation temperature in the evaporator on the high pressure side becomes large. Can be further increased, and the solution outlet concentration in the high pressure side absorber can be further reduced, so that the concentration range in the entire absorber is expanded,
The coefficient of performance can be improved. If the temperature difference between the inlet and outlet of the cold water is changed from the conventional 5 ° C. to an 8 ° C. difference of 15 → 7 ° C., the concentration width reaches 11% and the COP reaches 1.55 (FIG. 3).

[0018]

FIG. 1 shows a schematic piping configuration of an absorption refrigerator as an embodiment of the present invention. The absorption refrigerator includes an evaporator (1), an absorber (2), a high-temperature regenerator (3), a low-temperature regenerator (4), a condenser (5), a high-temperature heat exchanger (6), and a low-temperature heat exchanger. (7) and an absorbent pump (8) are included as main components, and a burner (9) as a heat source of the high temperature regenerator (3) is also included to constitute a double effect absorption cycle (10). In the double-effect absorption cycle (10), water is used as a refrigerant, lithium bromide is used as an absorbent, and an aqueous solution of lithium bromide is used as an absorbent, and circulated by an absorbent pump (8).

In the double effect absorption cycle (10), water as a refrigerant is evaporated in the evaporator (1), and heat required for vaporization is taken from the cold water to cool the cold water. The refrigerant evaporated in the evaporator (1) is absorbed in the solution in the absorber (2). In the high-temperature regenerator (3) and the low-temperature regenerator (4), the absorbing liquid that absorbs the refrigerant in the absorber (2) evaporates water as a refrigerant from the aqueous solution of lithium bromide to increase the concentration of the solution. In the condenser (5), water as the evaporated refrigerant is condensed. In the high-temperature heat exchanger (6), a medium-concentration solution in which the concentration is increased by evaporating the refrigerant in the high-temperature regenerator (3) and a low-concentration solution in which the concentration is reduced by absorbing the refrigerant in the absorber (2) Heat exchange is performed with the absorbing solution. The low-concentration solution whose temperature has been increased by the heat exchange returns to the high-temperature regenerator (3), and the absorbent is regenerated. Absorber (2) to high temperature regenerator (3)
The dilute solution fed by the absorbent pump (8) into the low-temperature heat exchanger (6) before the heat exchange with the intermediate-concentration solution from the high-temperature regenerator (3) in the high-temperature heat exchanger (6). In 7), heat exchange is performed with the high-concentration absorbent supplied from the low-temperature regenerator (4) to the absorber (2).

The evaporator (1) and the absorber (2) of the present embodiment are each composed of a plurality of stages. The evaporator (1) is divided into a high-pressure side evaporator (11) and a low-pressure side evaporator (12). In addition, the absorber (2)
It is divided into a high pressure side absorber (13) and a low pressure side absorber (14). The high-pressure side evaporator (11) is disposed lower than the low-pressure side evaporator (12), and the cold / hot water pipe (15) through which cold water to be cooled flows flows through the lower high-pressure side evaporator (1).
The 1) side is the inlet side, and the upper low-pressure side evaporator (12) is the outlet side. The high pressure side absorber (13) communicating with the high pressure side evaporator (11) is disposed below the low pressure side absorber (14) communicating with the low pressure side evaporator (12).

The cooling water pipe (16) for cooling the absorbing liquid in the high-pressure side absorber (13) and the low-pressure side absorber (14) includes a lower high-pressure side absorber (13) on the input side and an upper low-pressure side. An absorber (14) is provided on the outlet side. The low-pressure side absorber (14) is supplied with the concentrated solution from the low-temperature regenerator (4) via the low-temperature heat exchanger (7) through the concentrated solution pipe (17). From the high-pressure side absorber (13), the absorbing solution diluted by absorbing the refrigerant is diluted by the absorbing solution pump (8) into the dilute solution pipe (1).
8) via low temperature heat exchanger (7), high temperature heat exchanger (6)
From the high temperature regenerator (3). Assuming that the temperature of the low-temperature water on the inlet side supplied to the cold / hot water pipe (15) as a whole is 12 ° C. and the temperature of the cold / hot water on the outlet side is 7 ° C., the high-pressure side evaporator (11) There is a temperature difference of 5 ° C. as a whole between the evaporator and the low pressure side evaporator (12). At this time, the cooling water inlet temperature to the cooling water pipe (16) of the high pressure side absorber (13) is set to 3
The cooling water outlet temperature from the cooling water pipe (16) of the low-pressure side absorber (14) is about 36 ° C. The temperature of the absorbent in the high-pressure side absorber (13) becomes 39 ° C.

FIG. 2 shows the double-effect absorption cycle (1) of FIG.
0) indicates a state change of the absorbing solution. FIG. 2A shows the temperature difference Δt between the inlet and outlet of the cold water in the evaporator (1) as described above.
The example of the cycle diagram in the case of 5 degreeC is shown. Point A shows the state at the outlet side of the high-temperature regenerator (3).
It turns out that it has risen to ° C. B shows the state of the absorbent at the outlet of the low-temperature regenerator (4), and the solution temperature is 93
It turns out that it has risen to ° C. C indicates the state at the inlet of the high-pressure side absorber (13), and the temperature of the absorbing solution is 52 ° C.
Which indicates that the concentration is 64 wt%. D
Indicates the state of the absorbent at the outlet side of the low-pressure side absorber (14), the temperature of the absorbent is 36 ° C., and the concentration is 56.2 wt.
%. In this case, the concentration range of the absorber (2) as a whole is 64-56.2 = 7.8 wt%.

FIG. 2B shows a state change of the absorbing liquid in the case of a large temperature difference specification in which the temperature difference of the cold water in the entire evaporator (1) is Δt = 8 ° C. Since the temperature of the cold water at the outlet side of the high-pressure side evaporator (11) is increased to 15 ° C. by adopting the large temperature difference specification, the evaporation pressure in the high-pressure side evaporator (11) is increased as shown in FIG.
(A) can be increased from 7.8 mmH to 8.7 mmH, and under the same conditions as in FIG. 2 (a) where the temperature of the absorbing liquid in the high-pressure side absorber (13) is 36 ° C., The concentration of the absorbing solution can be reduced to 53% by weight. As a result, the concentration range becomes 64-53 = 11 wt%, and the pressure and the solution temperature in the high-temperature regenerator (3) can be reduced as compared with the case shown in FIG.

FIG. 3 shows the relationship between the concentration range of the absorbing solution and the coefficient of performance COP in the entire absorber (2). The graph indicated by the imaginary line shows the change in the coefficient of performance in the double effect absorption refrigeration cycle when the conventional absorber and evaporator are of a single-stage type. As shown in FIG. 2A, when the temperature difference Δt of the cold water as a whole is 5 ° C., for example, the temperature of the cold / hot water at the inlet of the cold / hot water pipe (15) is 12 ° C. Shows the change when the temperature of the cold / hot water at 7 ° C. is 7 ° C. The broken line is shown in FIG.
The change when Δt = 8 ° C. is shown as shown in FIG. In this case, the temperature on the inlet side of the cold / hot water pipe (15) is 15 ° C., and the temperature on the outlet side is 7 ° C. From FIG. 3, it can be seen that the concentration width, which is the concentration difference of the absorbing solution between the inlet side and the outlet side to the absorber (2), is 7.8 wt.
% Or more, the coefficient of performance COP becomes 1.45 or more even when the cold water temperature Δt = 5 ° C., and it can be improved by 20% or more compared to the conventional COP of about 1.2.
Further, if the temperature difference Δt of the cold water is 5 ° C. or more, the concentration range is easily increased, and the concentration range is 11% and the coefficient of performance COP is increased.
It can be seen that 1.55 can be achieved.

In the embodiment described above, the evaporator (1)
Although the absorber and the absorber (2) each have a two-stage configuration, it is possible to further increase the concentration width and improve the coefficient of performance by using a multi-stage configuration of two or more stages.

[0026]

As described above, according to the present invention, the evaporators (11, 12) can be divided into a plurality of stages and the refrigerant temperature can be changed to further lower the concentration on the low concentration side. 13, 14) Even if the concentration width, which is the difference between the concentration of the solution on the inlet side and the concentration on the outlet side, exceeds 7.8 wt%,
The coefficient of performance COP, which indicates the ratio between the refrigeration capacity and the amount of heat flowing into the regenerator, can be increased without causing problems such as crystallization.

According to the present invention, the coefficient of performance COP can be increased under practical operating conditions.

Further, according to the present invention, a double effect absorption refrigeration cycle (10) is provided which divides the regenerator into a high-temperature regenerator (3) and a low-temperature regenerator (4).
P can be increased to 1.45 or more.

According to the present invention, a plurality of absorbers (1)
Since the evaporators (11, 12) and the evaporators (11, 12) are arranged one above the other with the high pressure side down, the absorber (13, 1)
4) There is no need to install a pump to transport the solution between them,
Compared to the necessity of a pump in the horizontal arrangement, the configuration can be simplified and the manufacturing cost can be reduced.

According to the present invention, the temperature difference between the inlet side and the outlet side of the cold water cooled by the evaporators (11, 12) in a plurality of stages is set to 5 ° C. or more, so that the evaporation temperature on the high pressure side is reduced. By further raising, the concentration of the absorbing solution at the outlet side of the absorber can be further reduced, and the concentration range of the solution over the entire absorber (13, 14) is expanded, so that the temperature difference is less than 5 ° C. Can also improve the coefficient of performance COP.

[Brief description of the drawings]

FIG. 1 is a simplified piping diagram showing a double-effect absorption cycle (10) according to an embodiment of the present invention.

FIG. 2 is a cycle diagram showing a state change of an absorbent in a double-effect absorption cyclile (10) of FIG.

FIG. 3 shows a density range and a coefficient of performance C obtained in the embodiment of FIG.
It is a graph which shows the relationship with OP.

FIG. 4 is a cycle diagram showing a state change of an absorbent in a conventional single-stage double-effect absorption cycle.

FIG. 5 is a cycle diagram showing a tendency of a state change of an absorbent in a multistage double effect refrigeration cycle according to the prior art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Evaporator 2 Absorber 3 High temperature regenerator 4 Low temperature regenerator 5 Condenser 6 High temperature heat exchanger 7 Low temperature heat exchanger 8 Absorbent pump 10 Double effect absorption cycle 11 High pressure side evaporator 12 Low pressure side evaporator 13 High pressure side Absorber 14 Low-pressure side absorber 15 Cold and hot water pipe 16 Cooling water pipe

Claims (5)

[Claims] 1. An absorption refrigerator having water as a refrigerant and lithium bromide as an absorbent, wherein a plurality of combinations of an absorber (2) and an evaporator (1) are provided, and a plurality of stages of absorbers are provided. The concentration width, which is the difference between the concentration of the absorbent on the inlet side and the concentration of the absorbent on the outlet side with respect to (13, 14), is
An absorption refrigerator characterized by exceeding 7.8 wt%. 2. The absorption chiller according to claim 1, wherein the chilled water outlet temperature is 7 ° C. and the chilled water inlet temperature is 32 ° C. 3. A component of the absorption refrigeration cycle,
High temperature regenerator (3), low temperature regenerator (4), condenser (5),
It further comprises a high-temperature heat exchanger (6), a low-temperature heat exchanger (7) and an absorbent pump (8), and comprises a double-effect absorption cycle (1).
The absorption refrigerator according to claim 1, wherein the absorption refrigerator comprises: 4. The plurality of absorbers (13, 14) and the evaporators (11, 12) are arranged vertically so that the lower stage has a higher evaporation pressure than the upper stage. An absorption refrigerator according to any one of claims 1 to 3. 5. The method according to claim 1, wherein the difference between the temperature on the outlet side and the temperature on the inlet side of the chilled water exceeds 5 ° C. for the whole of the plurality of evaporators (11, 12). The absorption refrigerator according to any one of the above.