JPH10306957A - Absorption refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a pressure loss of vapor in an absorber of an absorption refrigerator and enable a smooth discharge of non condensible gas in the absorber. SOLUTION: An absorption refrigerator comprises an evaporator which generates vapor by evaporating liquid on the surface of a plurality of heat transfer pipes and an absorber which makes an absorbent on the surface of heat transfer pipes absorb the vapor fed into the absorber. In this absorber, on a cross section of the heat transfer pipes 1 as seen from a longitudinal direction of the transfer pipes 1, vapor channels 2 are formed between a wall surface and the neighboring heat transfer pipes 1 along the wall surface. A gas extraction port 7 is disposed in a set of heat tranfer pipes 1 arranged in a grid array, wherein the surface distance L1 between the heat transfer pipe in a horizontal direction is set to not less than 10 mm, while the surface distance L2 between the heat transfer pipe in a vertical direction is set to not more than 5 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absorption refrigerator used for cooling and heating.

[0002]

2. Description of the Related Art In general, an absorption refrigerator has an absorber, an evaporator,
It consists of a condenser, a low-temperature regenerator, a high-temperature regenerator, a pump connecting them, and a heat exchanger. FIG. 7 is a system diagram showing the principle. Water is passed through the tubes of the tube group in the evaporator, and water is sprayed outside the tubes as a refrigerant. The water in the tubes is cooled by the latent heat of evaporation, and supplied to a cooler or the like as cold water. The water vapor generated by the evaporator flows into the absorber, and is absorbed by the absorbing liquid (such as lithium bromide) sprayed on the outer surface of the tube group in the absorber. At this time, the absorption heat generated by the cooling water flowing in the tube Cooled.

[0003] The absorption liquid having absorbed the water vapor in the absorber has a reduced concentration and a reduced absorption power. Then, after pre-heating this through a heat exchanger, it is sent to a high-temperature regenerator and a low-temperature regenerator to be heated and concentrated. As a heat source of the high-temperature regenerator, heat obtained by burning gas, oil, or the like is generally used. Steam generated by the high-temperature regenerator is used as the heat source of the low-temperature regenerator. The steam generated in the low-temperature regenerator and the high-temperature regenerator is finally cooled by the cooling water in the condenser and condensed. The condensed water is supplied to an evaporator as an evaporation medium. Of these components of the absorption refrigerator, the absorber is particularly important in that the performance of the absorption refrigerator is affected.

[0004] The evaporator and absorber are kept at low pressure. Therefore, in the evaporator, as described above, by evaporating the evaporation medium such as water sprayed on the outer surface of the pipe, the latent heat can cool the cooling medium such as water flowing in the pipe. The absorber generally includes a heat transfer tube group in a staggered or lattice arrangement and a spraying device for spraying the absorbing liquid on the surface thereof. In general, a lithium bromide solution is used as the absorbing solution, and is sprayed on the outer surface of the heat transfer tube. The vapor pressure of lithium bromide is much lower than that of water, and the vapor flowing into the absorber from the evaporator is absorbed by the absorbent based on the difference in vapor pressure. At this time, since the temperature of the absorbing liquid rises due to the absorbed heat, a cooling medium such as water is flown in the heat transfer tube to cool the tube.

In order to improve the performance of the absorption refrigerator, it is necessary to increase the effective pressure difference between the vapor pressure of the evaporation medium in the evaporator and the vapor pressure of the absorption liquid in the absorber from the above-mentioned principle of the absorption cycle operation. is there. Therefore, first, the flow resistance (pressure loss) of the steam in the tube group of the absorber and the evaporator should be reduced, and the pressure difference available for absorbing the steam in the absorber should be increased.

[0006] Second, it is to improve absorption heat transfer characteristics in the absorber. There are three main ways to do this. One is not directly related to the present invention, but fins are formed on the surface of the heat transfer tube as described in JP-A-63-6363 in order to improve the absorption heat transfer characteristics of the heat transfer tube. There is a method of increasing the holding area of the absorbing liquid while increasing the heat area. Another measure is to prevent accumulation of non-condensable gases, such as air, which provide heat transfer resistance on the steam side. Another measure is to supply and distribute the absorbing liquid evenly to each heat transfer tube in the absorber to eliminate useless heat transfer tubes that are not used for absorption.

As a prior art for these performance improvement measures, as described in Japanese Patent No. 1187335, a steam upstream of an evaporator is arranged in a heat transfer tube array having a narrow grid arrangement, and a downstream portion having a large steam flow rate is arranged in a pitch. In the absorber, the staggered array with a wide pitch is used in the upstream of the steam with a large steam flow rate, and the heat transfer tubes in the grid array with a narrow pitch are used in the downstream of the steam in the absorber, so that the steam in the There is a method for equalizing the flow resistance. Further, as described in Japanese Patent Application Laid-Open No. Sho 62-155482, there is a method of preventing the accumulation of non-condensable gas and bleeding by providing a partition plate parallel to the tube row in the heat transfer tube group of the absorber. .

[0008]

In the above prior art, it is impossible to simultaneously reduce both the pressure loss in the absorber and the air (non-condensable gas) stagnation. The flow state of the vapor in the absorber is very complicated, and it is extremely difficult to measure the flow velocity, the flow direction, or the location of air retention of the vapor. Therefore, the tube arrangement is designed based on empirical knowledge, and it is very difficult to obtain a tube group that satisfies both low pressure loss and suppression of air stagnation. By combining the heat transfer tubes in the absorber with a staggered arrangement and a grid (checkerboard) arrangement and devising the tube pitch,
Even if the pressure loss can be reduced, air stagnation cannot be suppressed.

On the other hand, by providing a partition plate parallel to the tube row in the heat transfer tube group of the absorber, even if air stagnation can be suppressed, the pressure loss increases. Further, in the absorber, whether or not the absorption liquid is supplied to each heat transfer tube greatly affects the vapor absorption performance. If there is a heat transfer tube to which no absorbing liquid is supplied, the tube will not contribute to the absorption of steam at all. Both of these problems are closely related to the arrangement of the heat transfer tubes of the absorber, that is, the tube bank structure.

[0010] An object of the present invention is to provide an absorption refrigerator capable of reducing pressure loss in a heat transfer tube bank and suppressing air stagnation.

[0011]

In order to achieve the above object, according to the present invention, an evaporator for evaporating liquid on the surfaces of a plurality of heat transfer tubes to generate steam and a plurality of steams flowing from the evaporator are provided. In an absorption refrigerator provided with an absorber that absorbs with the absorbing liquid on the surface of the heat transfer tube, the absorber has a cross section viewed from a longitudinal direction of the heat transfer tube, and is provided between a wall surface and the heat transfer tube adjacent thereto. A steam flow passage is formed along the wall surface, a bleed port is provided in a tube group in which the heat transfer tubes are arranged in a grid pattern, and a distance between horizontal heat transfer tube surfaces is 10 mm or more, and a vertical heat transfer tube is provided. The configuration is such that the distance between the surfaces is 5 mm or less.

[0012] The flow resistance of the steam in the steam flow path is much smaller than the flow resistance in the tube group in which the heat transfer tubes are densely arranged, and can be ignored. According to the present invention, the steam in the absorber mainly flows through the steam flow path, and the pressure loss in the entire absorber can be significantly reduced. If a means (steam guide means) for guiding steam in the tube group is not installed in the steam flow path, the steam flows from the entire periphery of the tube group toward the center of the tube group, and the steam flow reaches the pipe Near the center of the group.

[0013] As the vapor flows through the tube group, the vapor is absorbed by the absorbing liquid and the flow rate decreases, and the non-condensable gas (air) which is not mainly absorbed by the absorbing liquid reaches the final point of the vapor flow.
Therefore, air extraction can be performed by arranging the extraction port in the tube bank. In this way, pressure loss in the tube bank can be reduced and air stagnation can be suppressed. For the above reason, it is more effective to arrange the bleeding port near the center of the tube group.

[0014] In addition, the installation of the steam guide member for guiding the steam in the tube group in the steam flow path has an effect of changing the final point of the steam flow. In particular, when the lower part of the tube group becomes the final point (bleed port) of the steam flow, the steam flows in from the upper part of the tube group, and the steam flow in the flow path is formed in the steam flow path between the side wall surface and the tube group. By providing the steam guide member that guides the inside of the tube group and the direction of the bleeding port, the steam flow as the entire absorber can flow from the upper part of the tube group to the lower bleeding port. Therefore, it is possible to reduce the pressure loss in the tube group and suppress the stagnation of air. In this case, the bleeding port arranged at the lower part of the tube bank can also serve as a discharge port of the absorbing liquid by having an ejector structure or the like.

[0015] When the right side of the tube group of the absorber is the final arrival point (bleed port) of the steam flow, the steam flow in the flow path is placed in the steam flow path on the left side of the tube group of the absorber. By providing a steam guide member that guides the flow toward the bleed port and the direction of the bleed port, the steam flow as the entire absorber can flow from the left side to the right side bleed port of the tube group.

Further, the present invention will be described more specifically based on embodiments. The supply of the absorbing liquid in the absorber is first scattered to the heat transfer tubes at the top of the tube group, flows on the surface of the heat transfer tubes, and sequentially flows down to the heat transfer tubes arranged therebelow. In order for the lower heat transfer tube surface to be sufficiently covered with the absorbing liquid, it is preferable that the interval between the upper and lower heat transfer tubes is small. In order to stably supply the absorbing liquid to the lower tube, the distance between the upper and lower heat transfer tube surfaces (the shortest distance between the outer surfaces of the heat transfer tubes) must be 5 mm or less.

In order to satisfy this condition regardless of the outer diameter of the heat transfer tubes, the heat transfer tubes are arranged in a grid pattern. The pressure loss in the cross-sectionally arranged tube group is determined by the pipe spacing in the direction perpendicular to the steam inflow direction, that is, the cross-sectional area through which steam can flow. When the steam flows in from the upper part of the tube group, the pressure loss can be reduced by making the distance between the horizontal surfaces of the heat transfer tubes 10 mm or more, and the steam flows down when the space between the upper and lower heat transfer tubes is made 5 mm or less. The absorbing liquid connects the upper and lower pipes in a curtain shape, and the steam flows downward as if flowing between the flat plates, and the final point of the steam flow is below the center of the tube bank. Therefore, by arranging the bleeding port at a position near the center of the tube bank or at a lower position, air can be effectively discharged from the bleeding port.

[0018]

FIG. 8 shows an example of an absorption refrigerator according to the present invention. The absorption refrigerator has an absorber 10 and an evaporator 1
1, a condenser 12, a low-temperature regenerator 13, a high-temperature regenerator 14, a heat exchanger 15, and piping connecting them, and various pumps.

In FIG. 8, a plurality of heat transfer tubes 1 are provided in the evaporator 11.
A heat transfer tube group, which is an aggregate of the above, is built in, and water is passed through each heat transfer tube 1. Water is sprayed on the outer surface of each heat transfer tube 1 as a coolant from a coolant spraying device 17. Number inside evaporator 11
Since the pressure is maintained at a low pressure of mmHg / cm ² , the heat transfer tube 1
The refrigerant on the outer surface evaporates, and the water flowing in the heat transfer tube 1 is cooled by the latent heat of evaporation, and supplied to a cooler or the like as cold water. The refrigerant that has not evaporated is circulated from the bottom of the evaporator 11 to the refrigerant distribution device 17 through the pipe 22 by the refrigerant pump 27.

The vapor generated in the evaporator 11 flows into the absorber 10 from above. A heat transfer tube group is also arranged in the absorber 10, and an absorption liquid spraying device 4 is arranged above the heat transfer tube group, and the absorption liquid 5 (LiBr or the like) is sprayed on the outer surface of the heat transfer tube 1. The steam flowing from the evaporator 11 is absorbed by the absorbing liquid 5 on the outer surface of the heat transfer tube 1. The absorption heat generated at that time is cooled by cooling water flowing in the heat transfer tube 1. This cooling water circulates through the low-temperature regenerator 13 and the cooling tower. Absorber 10
Inside, there is a space between the heat transfer tube group and the side wall surface, which forms the steam flow path 2. A steam flow straightening plate 9 is provided in the steam flow path 2 and guides the flow of steam obliquely downward toward the region of the heat transfer tube group. Details of the structure of the absorber 10 will be described later.

In the absorber 10, the concentration of the absorbing liquid 5 decreases because the absorbing liquid 5 absorbs the vapor. The absorbent 5 whose concentration has become low is discharged from the lower part of the absorber 10 and sent to the heat exchanger 15 by the absorbent pump 16 to be preheated.
Is sent to the high-temperature regenerator 14 through the pipe 25. In the high temperature regenerator 14, the absorption liquid 5 sent from the heat exchanger 15 is heated and concentrated by the combustion of oil or gas. The concentrated absorbent 5 is returned to the heating side of the heat exchanger 15 through the pipe 20 and is used as a heating source, and a part is supplied to the absorbent dispersion device 17 in the absorber 10 through the pipe 18. Is done.

The steam generated by concentration of the absorbent 5 in the high-temperature regenerator 14 passes through a pipe 21 and passes through the low-temperature regenerator 13.
The absorption liquid 5 which is supplied as a heating source, is preheated by the heat exchanger 15 and is supplied to the low temperature regenerator 13 by the pipe 24 is heated and concentrated. The concentrated absorbent 5 is returned to the heating side of the heat exchanger 15 through the pipe 19. The vapor generated by the concentration of the absorption liquid 5 in the low-temperature regenerator 13 is cooled and condensed in the condenser 12 and supplied to the refrigerant dispersion device 17 of the evaporator 11 through the pipe 23 as the refrigerant.

Although the inside of each of the above-described units is a closed container maintained at a low pressure of about 0.01 to 0.1 atm, if a small amount of air (non-condensable gas) leaks from a welded portion or the like, it is absorbed. Vessel 1
At 0, the absorption characteristic of the refrigerant vapor by the absorbing liquid 5 is reduced.
Therefore, it is necessary to perform bleeding in the absorber 10. FIG.
Then, the extraction port of the absorbing liquid 5 also serves as the bleeding port 6, and the non-condensable gas is discharged from the absorber 10 together with the absorbing liquid 5 from the absorber 10 by an ejector method or the like. It is discharged outside. The non-condensable gas can be efficiently discharged by the steam flow path 2 and the steam rectifying plate 9 in the absorber 10, and the non-condensable gas extraction port of the absorber 10 It is possible to use an independent port that does not double as the discharge port, as described later.

FIG. 9 is a block diagram showing another example of an absorption refrigerator according to the present invention. The basic configuration is the same as that of FIG. 8, but the flow direction of steam from the evaporator 11 to the absorber 10 and the structure of the absorber 10 are different. Evaporator 11 and absorber 10
An eliminator 28 is disposed between the eliminator 2 and the evaporator 11.
8 and flows into the absorber 10. Eliminator 2
The main function of 8 is to remove mist from the vapor flowing into the absorber 10 from the evaporator 11.

In the absorber 10, an opening serving as a steam inlet is oriented horizontally and horizontally so that steam flows in from the side of the heat transfer tube group. A steam flow passage 2 is formed between the heat transfer tube group and the wall surface, and a straightening plate 9 is installed in the steam flow passage 2 at an angle as a means for guiding steam in a direction inside the heat transfer tube group. Unlike the case of FIG. 8, the non-condensable gas extraction port 7 is provided on the side wall surface and is independent of the discharge port 8 of the absorbent 5.

Hereinafter, the absorber 10 will be described in detail. FIGS. 1 (a) and 1 (b) are schematic diagrams of cross sections of two embodiments of the absorber of the absorption refrigerator of the present invention, respectively, as viewed from the longitudinal direction of the heat transfer tube. 1 is a heat transfer tube, 2 is a steam flow path, 3 is an inflow portion of steam flowing from an evaporator, 4 is an absorbent dispersion device,
Reference numeral 5 denotes an absorbing liquid, 6 denotes a bleeding port also serving as an absorbing liquid discharge port, 7 denotes a bleeding port, 8 denotes an absorbing liquid discharge port, and 9 denotes a rectifying plate installed in a steam flow path and functioning as a steam guide member. The vapor inflow section 3 may be provided with an eliminator or the like in order to prevent the absorption liquid from scattering, but may be provided with an opening where nothing is provided.

(A) is an absorber in which steam flows in from the upper part of the tube group, and (b) is an absorber in which steam flows in from the side surface of the tube group. The pressure loss in the absorber is reduced by the effect of the steam flow path 2 formed between the tube group and the wall surface. (A)
In the above absorber, a flow straightening plate is installed in the steam flow path on the side wall surface,
The steam flow flows from the upper part to the lower part, and the final point of the steam flow is at the lower part of the tube bank. The non-condensable gas (air) can be discharged from the bleed port which also serves as the absorbent discharge port disposed below the tube group. In the absorber of (b), a flow straightening plate is installed in the steam flow path on the upper and lower surfaces and the inner side wall surface, the steam flows in the horizontal direction, and air can be extracted from the air outlet provided on the outer side wall surface of the tube group. .

FIGS. 2A and 2B are cross-sectional views of the absorber substantially similar to FIGS. 1A and 1B, respectively, as viewed from the longitudinal direction of the heat transfer tube. A straightening plate is not provided in the steam flow path of FIGS. 1A and 1B, and a bleeding port 7 is provided substantially at the center of each tube group. The steam that has flowed in both (a) and (b) flows through the steam flow path 2 from the entire periphery of the tube group toward the center, and the final point of the steam flow is near the center of the tube group. Therefore, air can be discharged from the bleed port 7 arranged near the center of the tube group.

In this embodiment, the distance L ₁ between the horizontal surfaces of the heat transfer tubes is set to 10 mm or more, and the distance L ₂ between the upper and lower surfaces of the heat transfer tubes is set to 5 or more.
By arranging the bleeding port at a position slightly below the center of the tube bank with the diameter being equal to or less than mm, it is possible to more effectively discharge air from the bleeding port. FIG. 3A also shows a cross-sectional view of an absorber of an absorption refrigerator according to another embodiment of the present invention as viewed from the longitudinal direction of the heat transfer tubes. The steam flows in from the upper part of the tube bank, and two straightening plates are installed in the steam passage on one side wall.
The heat transfer tubes in the tube group are arranged in a grid pattern, the horizontal tube pitch is about twice as large as the pipe diameter (that is, the horizontal pipe surface spacing is about the pipe diameter), and the vertical pipe pitch is vertical. It is quite narrow so that the pipe surface spacing is about 3 mm.

FIGS. 3 (b) and 3 (c) are cross-sectional views of the absorber of the absorption refrigerator according to still another embodiment of the present invention as viewed from the longitudinal direction of the heat transfer tubes. In FIG. 3B, the steam flow passages 2 are formed between both side wall surfaces and the heat transfer tube group, and one steam flow straightening plate 9 is installed in each steam flow passage 2 on both sides.
In FIG. 3C, the steam flow path 2 is formed between one side wall surface and the heat transfer tube group, and one steam flow straightening plate 9 is provided in the steam flow path 2.

Next, it is confirmed that the principle of the present invention is valid.
A description will be given based on the results of a numerical analysis of the basic arrangement of the tube banks in the absorber. In this numerical analysis, the law of conservation of mass and momentum is solved for the flow, and the amount of steam absorption in the heat transfer tube group is obtained based on an empirical formula. For more information on this analysis model,
(Proceeding of the Second International Symposium
on Condensers and condensation (1990), p.235-p.24
4) is shown.

FIGS. 4 (a) and 4 (b) show cross sections of the heat transfer tube groups of the two types of absorbers as viewed from the longitudinal direction of the heat transfer tubes subjected to numerical analysis. In each of the two types of absorbers, 198 heat transfer tubes (outer diameter 19.05 mm) of the same number are arranged at the same pitch. Steam flows in from the top of the absorber. (A) is an absorber in which a steam flow path is formed between a tube group (hatched in the figure) and a wall surface. (B) is an absorber in which a steam channel is not formed between the tube bank and the side wall surface. FIG. 9C shows the results of numerical analysis of the pressure distribution at the pressure plot positions in FIGS. 9A and 9B. This clearly shows that forming the steam flow passage between the tube bank and the wall surface makes the pressure distribution uniform and reduces the pressure loss.

FIGS. 5 (a) and 5 (b) show steam flow velocity distributions in an absorber having a steam flow path formed between a tube group (a region surrounded by a dotted line in FIG. 5) and a wall surface. 3 shows the results of numerical analysis of the air partial pressure distribution. Steam flows in from the top of the tube bank. From the steam flow velocity distribution in (a), it can be seen that the steam flows through the steam flow path 2 and is supplied to the entire absorber, and almost the center of the tube group is the final point of the steam flow. (B) shows the air partial pressure distribution at that time. It can be seen that air stays near the final point of the vapor flow and the partial pressure is high. Therefore, by providing a bleeding port substantially at the center of the tube group as shown in FIG. 2A, the air of the non-condensable gas can be continuously discharged.

6 (a) and 6 (b), similarly to FIGS. 5 (a) and 5 (b), the steam flow path is formed between the tube group (the area surrounded by the dotted line in the figure) and the wall surface. It is a figure which shows the numerical analysis result of the steam flow velocity distribution and the air partial pressure distribution in the absorber which is formed, respectively. However, six straightening plates are provided in the steam flow path on the side wall surface. The steam flows in from the upper part of the tube group and flows toward the lower part of the tube group. From the steam flow distribution shown in (a), it can be seen that the vicinity of the lower part of the tube bank is the final point of the steam flow. (B) shows the air partial pressure distribution at that time. It can be seen that air stays near the final point of the vapor flow and the partial pressure is high. Therefore, by providing a bleed port at the lower part of the tube group as shown in FIG. 1A, the air of the non-condensable gas can be continuously discharged.

[0035]

According to the present invention, the pressure loss of steam in the absorber of the absorption refrigerator can be reduced, and the non-condensable gas can be efficiently extracted.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a heat transfer tube of an absorber of an absorption refrigerator according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a heat transfer tube of an absorber of an absorption refrigerator according to a second embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of a heat transfer tube of an absorber of an absorption refrigerator according to a third embodiment of the present invention.

FIG. 4 is a pressure distribution diagram of the present invention and the prior art by numerical analysis.

FIG. 5 is a diagram showing a steam flow rate distribution and an air partial pressure distribution in an absorber having a steam flow channel by numerical analysis.

FIG. 6 is a diagram showing a steam flow rate distribution and an air partial pressure distribution in an absorber having a steam flow path by a numerical analysis and having a flow straightening plate installed in the steam flow path.

FIG. 7 is an overall system diagram of a conventional absorption refrigerator.

FIG. 8 is an overall system diagram of an absorption refrigerator according to an embodiment of the present invention.

FIG. 9 is an overall system diagram of an absorption refrigerator according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heat transfer pipe, 2 ... Steam flow path, 3 ... Steam inflow part, 4 ... Absorbent liquid spraying device, 5 ... Absorbent liquid, 6, 7 ... Bleed port, 8 ... Absorbent liquid outlet, 9 ... Steam rectification plate.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Michihiko Aizawa 603, Kandamachi, Tsuchiura-shi, Ibaraki Pref. In the Tsuchiura Plant, Hitachi, Ltd. Energy Research Institute

Claims (3)

[Claims] 1. An absorption device comprising: an evaporator for evaporating liquid on the surfaces of a plurality of heat transfer tubes to generate steam; and an absorber for absorbing the vapor flowing from the evaporator with the absorbent on the surfaces of the plurality of heat transfer tubes. In the refrigerator, the absorber has a cross section viewed from a longitudinal direction of the heat transfer tube,
A steam flow passage is formed along the wall surface between the wall surface and the heat transfer tube adjacent thereto, and a bleed port is provided in a tube group in which the heat transfer tubes are arranged in a grid pattern. An absorption refrigerator having a space between heat pipe surfaces of 10 mm or more and a space between heat transfer tube surfaces in a vertical direction of 5 mm or less. 2. The absorption refrigerator according to claim 1, wherein the bleeding port is disposed near a center of a tube group of the heat transfer tubes. 3. The absorption refrigerator according to claim 2, wherein the air extraction port is disposed below a center of a tube group of the heat transfer tubes.