JPH0518633A - Absorption refrigerating apparatus - Google Patents

Abstract

PURPOSE:To improve performance and to reduce size by a method wherein a heat transfer pipe having a groove with a given width and depth formed at a given pitch facing an axially helically extending protrusion formed on the inner surface of a pipe is used as a heat pipe for a condenser and a vaporizer. CONSTITUTION:A heat transfer pipe 30 is formed in a spiral shape and has a spiral groove 31 formed in the outer surface thereof, and a protrusion 32 is formed on the inner surface of the heat transfer pipe in a manner to be positioned facing the groove 31. A ratio P/D of a pitch P of the groove 31 to the diameter of the heat transfer pipe is set to 0.5-1.25, and the pitch P is, for example, 14 mm. Thus, compared with a smooth pipe, the coefficient of overall heat transmission is improved by 20% or more. A depth H of the groove 31 is, for example, 0.4 mm. When the depth is increased, a refrigerant enters the groove 31 and is not spread over the outer surface of the heat transfer pipe 30 but dropped. When the depth is decreased, turbulence effect operation of cold water owing to the protrusion 32 is reduced, whereby the depth is set to 0.3-0.8mm. Further, a width W of the groove 31 is, for example, 0.9 mm. When the width W is increased, the refrigerant is centralized in the groove 31, whereby the width is set to 0.5-5.0mm. A radius R of the groove is set to 0.4-1.0mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absorption refrigerating machine in which an evaporator, an absorber, a regenerator and a condenser are connected by piping to form a refrigeration cycle.

[0002]

2. Description of the Related Art As a heat transfer tube provided in an evaporator of an absorption refrigerating machine, for example, there is one disclosed in Japanese Utility Model Publication No. 53-40776. It is cooled by the refrigerant sprayed on it.

[0003]

In the above-mentioned prior art, since the outer surface and the inner surface of the heat transfer tube are smooth, the cold water flowing in the tube is not sufficiently agitated, and the cold water flows smoothly in the tube and is transferred to the cold water. The heat transfer coefficient with the heat tubes is low, and in order to secure the amount of heat transfer, the number of heat transfer tubes increases and the volume of the evaporator increases. Also, when a heat transfer tube with smooth outer and inner surfaces is used in the condenser, the cooling water flowing in the heat transfer tube is not sufficiently agitated as in the evaporator, and the cooling water and the heat transfer tube are not mixed. Has a low heat transfer coefficient, and in order to secure the heat transfer amount, that is, the cooling capacity in the condenser, the number of heat transfer tubes increases, the capacity of the condenser increases, and together with the problem in the evaporator, There has been a problem that the absorption chiller becomes large.

In order to solve the above problems, a spiral tube having a ridge formed on the inner wall of the tube is used in an evaporator.
In the above spiral tube, one having a narrow pitch and a diameter of approximately 0.4 to 0.5 times the outer diameter of the heat transfer tube is widely used, and a turbulent flow effect is caused in the tube by the projections to improve the heat transfer coefficient in the tube. The amount of heat exchange is increasing. However, since the pitch is narrowed, in a heat transfer tube group of an evaporator having a plurality of heat transfer tubes provided in upper and lower stages, when a refrigerant is sprayed from above, the heat exchanger is formed by grooves on the outer wall of the tube corresponding to the protrusions. There was a problem that the refrigerant gathered toward the lower part of the above, a dry heat transfer surface appeared, the heat transfer performance deteriorated, and the refrigerating capacity decreased.
Further, when the groove depth of the spiral is increased, the refrigerant enters the groove portion, does not spread to the outer surface of the heat transfer tube, and the wetting on the heat transfer surface becomes worse. Similarly, in the absorber, when the pitch of the ridges is narrow, the absorbing liquid gathers on the outer surface of the heat transfer tube to show a dry heat transfer surface, and the ability to absorb the refrigerant vapor deteriorates.

It is an object of the present invention to improve the refrigerating capacity of an evaporator and the refrigerant absorbing capacity of an absorber to improve the performance and size of an absorption refrigerator.

[0006]

In order to solve the above problems, the present invention forms a refrigeration cycle by connecting an evaporator 2, an absorber 3, a high temperature regenerator 4, a low temperature regenerator 11 and a condenser 12 by piping. In the absorption refrigerating machine described above, a protrusion 32 extending spirally in the pipe axis direction is provided on the inner surface of the pipe, and a groove 31 is provided on the outer surface of the pipe corresponding to the protrusion 32. The ratio to 0.5 to 1.25 and groove 3
The width of 1 is set to 0.5 mm to 5 mm, and the groove 31
The heat transfer pipe with the depth of 0.3 mm to 0.7 mm is set, and the cooling water inside the pipe is cooled by the heat transfer pipe 35 for the condenser and the cooling water flowing in the pipe and the refrigerant is dropped or sprinkled on the outer surface of the pipe. An absorption refrigerating machine equipped with a condenser 12 and an evaporator 2 used for a heat transfer tube 30 for an evaporator is provided, and the condenser 12 and the evaporator 2 are improved in performance to achieve miniaturization of each, and absorption refrigeration. It is intended to downsize the machine.

Further, the heat transfer tube 3 of the condenser 12 and the evaporator 2
A heat transfer tube formed in the same manner as 5, 30 is used for the heat transfer tube 30 of the absorber 3, and the condenser 12, the evaporator 2, and the absorber 3 are downsized, and the absorption refrigerator is downsized. Is.

[0008]

A part of the refrigerant dropped into the heat transfer tube 30 of the evaporator 2 travels down the groove 31 and flows down, and the remaining refrigerant spreads over almost the entire outside of the tube to improve the heat transfer between the refrigerant and the heat transfer tube. Further, the flow of the cold water flowing in the pipe is disturbed by the protrusions 32, the heat transfer between the cold water and the heat transfer pipe 30 is improved, the heat exchange efficiency in the heat transfer pipe 30 is significantly improved, and the evaporator 2 is improved in performance. As a result, the evaporator 2 is downsized. Further, the refrigerant condensed on the outer surface of the heat transfer tube 35 in the condenser 12 gathers in the groove 31 on the outer surface of the tube and flows down, so that the refrigerant can be prevented from spreading over the entire outer surface of the tube and a condensed area can be secured, thereby improving the condensing ability. To do. In addition, the ridge 32 formed on the inner surface of the heat transfer tube 35 causes a turbulent flow in the cooling water, which improves the heat transfer between the cooling water and the heat transfer tube 35, thereby significantly improving the heat exchange efficiency in the heat transfer tube 35. However, it is possible to improve the performance of the condenser 12 and to downsize the absorption refrigerator by downsizing the condenser 12 and the evaporator 2.

Further, like the heat transfer tube 30 of the evaporator 2, the concentrated absorbing liquid dropped on the heat transfer tube 30 of the absorber 3 in which the groove portion 31 and the protrusion 32 are formed spreads on almost the entire outer surface of the heat transfer tube 30. The heat transfer between the concentrated absorbent and the heat transfer tube 30 is improved, and
Turbulent flow is generated by the ridges 32 in the cooling water flowing in the pipe,
The heat exchange efficiency between the cooling water and the heat transfer tube 30 is improved, the performance of the condenser is improved, and the condenser 3 can be downsized, and the evaporator 2 and the condenser 12 are downsized, and the absorption type It is possible to further reduce the size of the refrigerator.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. In FIG. 1, reference numeral 1 denotes a low temperature evaporative absorber cylinder (lower cylinder), and an evaporator 2 and an absorber 3 are housed in the evaporative absorber cylinder 1. Reference numeral 4 denotes a high temperature regenerator, for example, a gas burner 5. The first absorbent pump P, the low temperature heat exchanger 7 and the high temperature heat exchanger are provided in the middle of the dilute absorbent liquid pipe 6 from the absorber 3 to the high temperature regenerator 4. 8 are provided.

Reference numeral 10 denotes a high temperature condensing regenerator cylinder (upper body), and a low temperature regenerator 11 and a condenser 12 are housed in the condensing regenerator cylinder 10. Further, 13 is a refrigerant vapor pipe from the high temperature regenerator 4 to the low temperature regenerator 11, 14 is a heater provided in the low temperature regenerator 11, and 15 is a refrigerant pipe from the heater 14 to the condenser 12. Reference numeral 16 is a refrigerant liquid downflow pipe from the condenser 12 to the evaporator 2, 17 is a refrigerant circulation pipe connected to the evaporator 2 by piping, 18 is a refrigerant pump, and 19 is a refrigerant spraying device. 21 is a cold water pipe connected to the evaporator 2, 21A
Is an evaporator heat exchanger.

Reference numeral 22 is an intermediate absorption liquid pipe from the high temperature regenerator 4 to the high temperature heat exchanger 8, 23 is an intermediate absorption liquid pipe from the high temperature heat exchanger 8 to the low temperature regenerator 11, and 23A is an inlet port of the intermediate absorption liquid. Reference numeral 24 is a second absorption liquid pump provided in the intermediate absorption liquid pipe 23. 25 is the low temperature regenerator 11 to the low temperature heat exchanger 7
The concentrated absorption liquid pipe to 26, the low temperature heat exchanger 7 to the absorber 3
The concentrated absorbent pipe to 27 and 27 are sprayers of the concentrated absorbent.
Also, 29 is a cooling water pipe, 29A is an absorber heat exchanger, and 29B.
Is a condenser heat exchanger.

As shown in FIG. 2, the evaporator heat exchanger 21A is composed of evaporator heat transfer tubes 30 arranged in a plurality of stages and a plurality of rows. Both inner and outer surfaces of these heat transfer tubes 30 are degreased with, for example, alcohol, and outer surfaces of the tubes are polished with, for example, a brush. Also, the heat transfer tube 30 ...
Supports 30A and 30A are formed at both ends of the support, and the outer and inner surfaces of the support 30A and 30A are smooth. The supporting portions 30A, 30A are supported by the tube plates 1A, 1A at both ends of the evaporation absorber body 1. Also, heat transfer tube 3
0 ... is circular and the diameter is, for example, 16 mm over the entire length.
Is. Above the heat transfer tubes 30 ... A spraying device (tray) 19 having a plurality of dropping holes 19a for spraying the refrigerant is provided. The heat transfer tube 30 is a corrugated tube, the heat transfer tube 30 has a spiral shape, and a spiral groove 31 is formed on the outer surface thereof. A ridge 32 is formed on the inner surface of the heat transfer tube so as to correspond to the groove 31.

At both ends of the groove 31 and the protrusion 32, the supporting portion 3 is provided.
Unsafe spiral portions 31B and 31B that gradually reduce the depth of the groove 31 and the height of the protrusion 32 toward 0A and 30A.
Are formed. And the unsafe spiral part 31
B and 31B are formed to have a length equal to or less than 1/2 of the outer circumference of the heat transfer tube 30, for example.

The pitch P of the grooves 31 is, for example, 14 mm. Here, if the pitch is narrowed, the amount of the dropped refrigerant that enters the groove 31 increases, and the refrigerant does not spread laterally. If the pitch is too wide, the turbulence effect due to the ridges 32 decreases, so the transmission of the pitch P is reduced. Ratio of heat pipe diameter D P / D
Is set to 0.5 to 1.25, and the pitch P is, for example, 14 mm. By setting the ratio P / D in this way, it was confirmed by experiments that the heat transmission coefficient is improved by 20% or more as compared with the smooth tube. Further, as shown in FIG. 3, the depth H of the groove 31 is 0.4 mm, for example. Here, when the depth H is increased, the dropped refrigerant enters the groove 31 and falls onto the outer surface of the heat transfer tube 30 without spreading, so that the groove 31
When the depth of the groove 31 is shallow, the effect of the turbulent flow effect of the cold water by the protrusion 32 corresponding to the groove 31 is reduced, so that the depth of the groove 31 is 0.
It is set from 3 mm to 0.8 mm. Further, the width W of the groove 31 is 0.9 mm, for example. Here, the groove width W is the groove 31
Is the width between the inflection point 33 where the curved surface starts and the inflection point 34 where the curved surface ends.
Since it concentrates on 1, it is set to 0.5 mm to 5.0 mm. The radius R of the groove is set to 0.4 mm to 1.0 mm.

The outer diameter of the heat transfer tubes 30 ...
FIG. 4 shows the magnification of the heat transfer coefficient of the heat transfer tube 30 with respect to the heat transfer coefficient of the smooth tube when the pitch of the grooves 31 is changed. Here, the depth H of the groove 31 is constant at 0.4 mm, and the width W
Was fixed at 0.9 mm. As is clear from the results shown in FIG. 4, when the pitch P is changed from 8 mm to 20 mm, that is, the ratio of the pitch P to the outer diameter D is 0.5 to 1.25.
In the case of, the heat transmission coefficient is 1.1 times or more as compared with the smooth tube.

The condenser heat exchanger 29B of the condenser 12 is composed of a plurality of stages and a plurality of rows of heat transfer tubes 35 ... Like the evaporator heat exchanger 21A. As shown in FIG. 5, these heat transfer tubes 35 are corrugated tubes like the heat transfer tubes 30 for the evaporator, and both ends thereof are supported by the tube plates 10A, 10A of the evaporative regenerator body 10. Then, a spiral groove 31 is formed on the outer surface. A ridge 32 is formed on the inner surface of the heat transfer tube so as to correspond to the groove 31. Further, in the heat transfer tube 35, in order to promote the condensation of the refrigerant vapor, the wettability is preferably not good, so the outer surface of the tube is not polished.

During operation of the absorption refrigerator constructed as described above, the gas burner 5 of the high temperature regenerator 4 burns, and the absorber 3
The rare absorption liquid, such as an aqueous solution of lithium bromide, which has flown from the heating unit is heated, and the refrigerant vapor is separated from the rare absorption liquid. The refrigerant vapor flows through the refrigerant vapor pipe 13 to the low temperature regenerator 11.
Then, the refrigerant liquid obtained by heating and condensing the intermediate absorption liquid from the high temperature regenerator 4 in the low temperature regenerator 11 flows into the condenser 12. In the condenser 12, the refrigerant vapor flowing from the low temperature regenerator 11 is condensed and flows down to the evaporator 2 together with the refrigerant liquid flowing from the low temperature regenerator 11. In the evaporator 2, the refrigerant liquid is sprayed to the evaporator heat exchanger 21A by the operation of the refrigerant pump 18. Then, cold water that has been cooled by the evaporator heat exchanger 21A and has its temperature lowered is supplied to the load. The refrigerant vapor vaporized in the evaporator 2 flows to the absorber 3 and is absorbed by the concentrated absorbing liquid sprinkled on the absorber heat exchanger 29A.

The intermediate absorption liquid whose refrigerant vapor has been separated in the high temperature regenerator 4 and has increased in concentration passes through the intermediate absorption liquid pipe 22, the high temperature heat exchanger 8, the intermediate absorption liquid pipe 23 and the second absorption liquid pump 24 to be regenerated at low temperature. It flows to the vessel 11. Here, the intermediate absorbent from the high temperature regenerator 4 is accelerated by the second absorbent pump 24 and flows in. Then, the intermediate absorption liquid is heated by the heater 14, the refrigerant vapor is separated from the intermediate absorption liquid, and the concentration of the absorption liquid is further increased.

The concentrated absorption liquid heated and concentrated in the low temperature regenerator 11 flows into the concentrated absorption liquid pipe 25 and flows into the absorber 3 via the low temperature heat exchanger 7 and the concentrated absorption liquid pipe 26. And the spraying device 2
7 to the absorber heat exchanger 29A.

When the absorption refrigerator is operating as described above, the refrigerant drops from the spraying device 19 of the evaporator 2 to the heat transfer tube 30. Then, the refrigerant spreads over the outer surface of the heat transfer tube 30 and smoothly flows and drops almost uniformly to the heat transfer tube 30 below, and at the same time, a part of the refrigerant flows down the groove 31. or,
Turbulent flow is generated in the cold water flowing in the heat transfer tube 30 by the ridges 32, and heat transfer between the cold water and the heat transfer tube 30 is improved. or,
Also in the lower heat transfer tube 30 of the evaporator 2, the refrigerant drips from the upper heat transfer tube 30 almost uniformly, and the heat transfer tube 30 is formed by the refrigerant.
Wetting of the surface is ensured.

In the heat transfer tubes 30 ..., the outer diameter is 16 m.
FIG. 4 shows the magnification of the heat transfer coefficient of the heat transfer tube 30 with respect to the heat transfer coefficient of the smooth tube when the pitch of the grooves 31 is changed. Here, the depth H of the groove 31 is constant at 0.4 mm, and the width W
Was fixed at 0.9 mm. As is clear from the results shown in FIG. 4, when the pitch P is changed from 8 mm to 20 mm, that is, the ratio of the pitch P to the outer diameter D is 0.5 to 1.25.
In the case of, the heat transmission coefficient is 1.1 times or more as compared with the smooth tube.

In the heat exchanger 29B of the condenser 12, the refrigerant vapor flowing from the low temperature regenerator 11 is condensed on the outer surface of the heat transfer tube 35. Then, the refrigerant flows downward on the outer surface of the heat transfer tube 35 and drops from the lower end to the heat transfer tube 35 below. Here, the refrigerant on the outer surface of the tube collects in the groove 31 and drops downward. In this way, on the outer surface of the heat transfer tube 35, the refrigerant does not spread and travels along the groove 31 and drops, so that the condensation area increases.
Therefore, the pitch P is set so that the refrigerant can easily propagate through the groove 31.
Is preferably smaller than the heat transfer tube 30. In addition, turbulent flow is generated in the cooling water flowing in the heat transfer tube 35 by the protrusion 32, and heat transfer between the cooling water and the heat transfer tube 35 is improved.

According to the above embodiment, the heat transfer tube 3 of the evaporator 2
Since 0 is the ratio of the pitch P to the outer diameter D, the groove depth, and the width are set as described above, when the refrigerant is dropped into the heat transfer tubes 30, the refrigerant on the outer surface of the tube is concentrated in the grooves 31. Without flowing, it spreads out almost all over the pipe, and the refrigerant and heat transfer pipe 3
The heat transfer with zero can be improved, and the refrigerant can be dripped into the lower heat transfer tube 30 almost uniformly. In addition, turbulent flow occurs in the cold water flowing in the heat transfer tube 30 due to the ridge 32, and this turbulent flow improves heat transfer between the cold water and the heat transfer tube 30, thereby significantly improving heat exchange efficiency in the heat transfer tube 30. Can be made. As a result, the performance of the evaporator 2 can be significantly improved, the number of heat transfer tubes 30 can be reduced, the evaporator 2 can be downsized, and the evaporation absorber body 1 can be downsized.

Further, when the outer surface of the heat transfer tube 30 is polished, the wettability is further improved, and the heat exchange efficiency in the heat transfer tube 30 can be further improved.

Further, since the heat transfer tube 35 of the condenser 12 is a corrugated tube and the spiral groove 31 and the projection 32 are formed, the refrigerant condensed on the outer surface of the tube flows to the groove 31 and flows. It is possible to prevent the refrigerant from spreading over the entire outer surface of the tube and to secure a condensation area, and in particular, it is possible to secure a condensation area in the lower heat transfer tube 35 where the refrigerant drips from above.
Here, in the heat transfer tubes 35, it is preferable that the pitch of the grooves 31 is smaller than that of the heat transfer tubes 30 so that the refrigerant does not spread on the outer surface of the tubes and flows down the grooves 31. Further, the ridge 32 formed on the inner surface of the heat transfer tube 35 causes a turbulent flow in the cooling water, which improves the heat transfer between the cooling water and the heat transfer tube 35.
The heat exchange efficiency at 5 can be greatly improved. As a result, the performance of the condenser 12 can be significantly improved, the number of heat transfer tubes 35 can be reduced, the condenser 12 can be downsized, and the condensation regenerator body 10 can be downsized, and the absorption refrigeration system can be used. The machine can be significantly downsized. In addition, the absorption refrigerator can be downsized to reduce the filling amount of the absorbing liquid.

Further, the heat exchanger 29A provided below the spraying device 27 of the absorber 3 is composed of a plurality of heat transfer tubes 30 which are corrugated tubes formed similarly to the heat transfer tube 30 of the evaporator 2. In this case, since the depth, pitch and width of the groove are almost the same as those of the heat transfer tube 30, it is possible to prevent the concentrated absorbent dropped from the spraying device 27 from concentrating and flowing into the groove during operation of the absorption refrigerator. The concentrated absorbent spreads out almost the entire surface of the tube to improve heat transfer between the concentrated absorbent and the heat transfer tube 30, and the concentrated absorbent spreads over the entire surface of the evaporator 2.
The absorption capacity can be improved by absorbing the refrigerant vapor from the above, and further, the concentrated absorption liquid can be dripped almost uniformly into the lower heat transfer tube 30. In addition, turbulent flow is generated in the cooling water flowing through the heat transfer tube 30 by the ridge 32, and the heat transfer between the cooling water and the heat transfer tube 30 is improved by the turbulent flow, and the heat transfer efficiency in the heat transfer tube 30 is significantly improved. can do. As a result, the performance of the absorber 3 is significantly improved, the number of heat transfer tubes 30 is reduced,
The absorber 3 can be miniaturized, and the absorption refrigerating machine can be greatly miniaturized as well as the evaporator 2 and the condenser 12 can be miniaturized.

[0028]

The present invention is an absorption refrigerating machine configured as described above, and in an absorption refrigerating machine in which an evaporator, an absorber, a regenerator and a condenser are connected by piping, the inner surface of the tube is arranged in the axial direction of the tube. It has a ridge extending spirally, and a groove is formed on the outer surface of the pipe corresponding to this ridge, and the groove pitch is 0.5 mm to 1.25.
mm and the width of the groove is 0.5 mm to 5 m
m and the groove depth is 0.3 mm to 0.7 m
Since the heat transfer tube set to m is used as the condenser heat transfer tube and the evaporator heat transfer tube, the condenser and the evaporator are provided, so that the refrigerant dropped in the evaporator heat transfer tube spreads almost all over the tube, And the heat transfer between the heat transfer tube and
Further, the refrigerant can be dripped into the lower heat transfer tube almost uniformly, and the heat transfer of the entire heat transfer tube provided in the evaporator can be improved. In addition, turbulent flow occurs in the cold water flowing in the heat transfer tube due to the ridges, improving heat transfer between the cold water and the heat transfer tube,
The heat exchange efficiency in the heat transfer tube can be greatly improved. As a result, the performance of the evaporator is significantly improved, and the size of the evaporator can be reduced. Furthermore, the refrigerant condensed on the outer surface of the heat transfer tube of the condenser flows in the grooves to collect and secure a condensing area.In addition, turbulent flow occurs in the cooling water flowing in the heat transfer tube due to the ridges, and The heat exchange efficiency of can be greatly improved, and as a result, the performance of the condenser can be greatly improved and the size can be reduced, and the size of the evaporator and the absorption refrigerator can be significantly reduced. be able to.

Furthermore, by defining the width, depth and pitch of the grooves of the heat transfer tubes of the evaporator and the condenser, and by using the heat transfer tubes in which the dimensions of the grooves are specified in the absorber as in the above heat transfer tubes. In addition, the evaporator and the condenser can be downsized, and the heat transfer and heat exchange efficiency in the heat transfer tube of the absorber can be significantly improved, and the absorption capacity of the refrigerant vapor can be further improved. The size can be reduced, and as a result, the absorption refrigerator can be further downsized and the filling amount of the absorption liquid can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an absorption refrigerator.

FIG. 2 is a side view illustrating the configuration of an evaporator.

FIG. 3 is a cross-sectional view of a heat transfer tube.

FIG. 4 is a relationship diagram of a groove pitch and a ratio of heat transmission coefficient of a grooved heat transfer tube to a smooth tube.

FIG. 5 is a side view illustrating the configuration of a condenser.

[Explanation of symbols]

2 evaporator 3 absorber 4 High temperature regenerator 11 Low temperature regenerator 12 condenser 19 Spraying device 27 Spraying device 30 heat transfer tubes 31 groove 32 ridges 35 heat transfer tube

Claims (2)

[Claims] 1. An evaporator that cools chilled water by vaporizing a refrigerant and supplies it to a load, and an absorber in which the refrigerant vapor flows from the evaporator and a rich absorbing liquid is sprayed to absorb the refrigerant vapor by the rich absorbing liquid. And a regenerator for heating the rare absorption liquid from this absorber to separate the refrigerant vapor, and a condenser for inflowing the refrigerant vapor from this regenerator and condensing the refrigerant vapor to connect the piping to form a refrigeration cycle. In the absorption chiller thus formed, there is a protrusion on the inner surface of the pipe that extends spirally in the pipe axis direction, and there is a groove on the outer surface of the pipe corresponding to this protrusion, and the ratio of the pitch of this groove to the outer diameter of the pipe Is set to 0.5 to 1.25, the width of the groove is set to 0.5 mm to 5 mm, and the depth of the groove is set to 0.3 mm to 0.7 mm. Flowing heat transfer tubes for condensers and refrigerant dripping or scattering on the outer surface of the tubes. An absorption refrigerator comprising a condenser and an evaporator used as a heat transfer tube for an evaporator, which is covered with a refrigerant to cool the cold water in the tube. 2. An evaporator that cools cold water by vaporizing the refrigerant and supplies it to a load, and an absorber in which the refrigerant vapor flows from the evaporator and a rich absorbing liquid is sprayed to absorb the refrigerant vapor by the rich absorbing liquid. And a regenerator for heating the rare absorption liquid from this absorber to separate the refrigerant vapor, and a condenser for inflowing the refrigerant vapor from this regenerator and condensing the refrigerant vapor to connect the piping to form a refrigeration cycle. In the absorption chiller thus formed, there is a protrusion on the inner surface of the pipe that extends spirally in the pipe axis direction, and a groove is formed on the outer surface of the pipe corresponding to this protrusion, and the ratio of the pitch of this groove to the outer diameter of the pipe is Is set to 0.5 to 1.25, the width of the groove is set to 0.5 mm to 5 mm, and the depth of the groove is set to 0.3 mm to 0.7 mm. Heat transfer tube for condenser flowing in the tube, refrigerant dripping on the outer surface of the tube, or Is for the evaporator that is sprayed and cools the cold water inside the pipe with the refrigerant.For the heat transfer pipe and cooling water that flows through the pipe, and the absorbent is dropped or sprayed on the outer surface of the pipe.For the absorber that cools the outside absorption liquid with the cooling water. An absorption refrigerator comprising a condenser used for a heat transfer tube, an evaporator and an absorber.