JPH0450504B2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field This invention mainly applies to organic refrigerant-absorbents, such as trifluoroethanol as a refrigerant and N-methyl 2-pyrrolidone or N-butyl 2-pyrrolidone as an absorbent. The present invention relates to an evaporator for an absorption chiller that obtains cold water or cold air for cooling, hot water supply, and hot water or hot air for space heating through a closed circulation cycle of these refrigerants and absorbents.

(b) Prior art Machines for obtaining cooled fluid, such as heated fluid, through a closed circulation cycle of a refrigerant absorbent include absorption chillers, absorption chiller-heating machines, absorption heat pumps, etc. (abbreviated as absorption chiller). Each of these absorption chillers has a generator that heats the absorption liquid to reseparate the refrigerant from the absorption liquid that has absorbed the refrigerant, and a condenser that liquefies the obtained refrigerant and supplies it to the evaporator. In order to obtain a cooled fluid, the liquid refrigerant is vaporized under low pressure conditions, and the latent heat during vaporization is used to cool the fluid supplied to the load. In addition, when obtaining heated fluid, the heat obtained when the refrigerant vaporizes in the evaporator is recovered by the absorbing liquid, and the fluid supplied to the load is heated with that heat and the heat of the absorbing liquid itself. ing.

Therefore, when a water-lithium bromide system is used as the refrigerant-absorbent in such an absorption chiller, water (H ₂ O) has a large vapor specific volume of about 150 m ³ /Kg.
Evaporators using heat exchanger tubes for general Freon-type refrigerators, such as tubes with a diameter of 15.9 mm or 9.52 mm, have been difficult to use because of the large pressure loss in the tubes. In addition, when using pipes with a large diameter to keep this pressure loss within an allowable limit, heat exchangers using such pipes require special mechanical equipment to secure the heat radiation fins and the pipes. The drawback was that the cost of absorption chillers was high.

For example, in FIG. 1, reference numeral 1 denotes a refrigerant pipe into which a large number of heat exchange fins 2 installed vertically are fitted;
3 is a refrigerant liquid pipe that supplies liquid refrigerant to this refrigerant pipe 1;
4, 4'... are liquid reservoirs that temporarily store the liquid refrigerant flowing in through the refrigerant liquid pipe 3 and supply it to the refrigerant pipes 1, 1'...;
5, 5'... have openings 6, 6'... on the upper side, and release the refrigerant gas that has been vaporized by gaining heat in the refrigerant pipes 1, 1'..., while collecting the liquid refrigerant that could not be vaporized and sequentially discharging it. , is a supply liquid reservoir that drips into the lower liquid reservoir 4'.
Refrigerant pipes 1, 1'..., liquid reservoirs 4, 4'..., supply liquid reservoir 5,
5'... are constructed to be enclosed in airtight headers 7, 7' communicating with an absorber (not shown).

However, since conventional absorption chillers use water as a refrigerant, the refrigerant pipes 1 and 1' must also be made thicker.
In the headers 7, 7', liquid reservoirs 4, 4'... and supply liquid reservoir 5,
Not only is it difficult to form 5', but it also poses a major obstacle to reducing manufacturing costs and downsizing of absorption chillers.

For example, in Utility Model Application No. 58-78465, there is a U-shape at both ends of the evaporation tube which is bent into a U-shape.
An evaporator for an absorption air conditioner is disclosed in which a bend is connected and an upward opening is formed at the connection between the U-bend in the steam duct and the evaporator tube. In this evaporator, it is necessary to form openings at both ends of each evaporation tube, and the process of drilling holes to form these openings takes time and effort, resulting in a problem that the manufacture of the evaporator becomes complicated. Furthermore, in the evaporator,
Since the opening and the vapor duct are provided only at one end of the evaporator, a problem arises in that the refrigerant gas vaporized in the evaporator tube is difficult to escape from the evaporator tube.

Furthermore, in Utility Model Publication No. 45-11503, the ends of the upper evaporator tube and the lower evaporator tube are connected by a down-flow tube, and upward refrigerant vapor exhaust pipes are connected to both ends of each evaporator. An absorption refrigerating device is disclosed which includes an exhaust tank containing a downflow pipe and a refrigerant vapor exhaust pipe at both ends. In the evaporator of this refrigeration system, exhaust tanks are provided at both ends of the evaporator, and refrigerant vapor exhaust pipes are connected to both ends of the steam pipes, so refrigerant gas escapes from each steam pipe. Refrigerant gas escapes easily compared to the evaporator disclosed in No. However, since the refrigerant vapor exhaust pipe is connected at right angles to each evaporator pipe, there is a large flow resistance when the refrigerant gas that flows through the vapor pipe flows into the refrigerant vapor exhaust pipe and is discharged, and the refrigerant gas flows smoothly. The problem arises that the steam is not discharged from the pipe. Furthermore, it is necessary to connect a downflow pipe to the steam pipe and to connect a refrigerant vapor exhaust pipe to both ends of each evaporator, which increases the number of connection points and creates a problem in that the fabrication of the evaporator becomes complicated.

(c) Purpose of the Invention This invention, which was created in view of the above points, aims to use the structure of the evaporator used in absorption chillers as commonly as possible with the components widely used in heat exchangers for fluorocarbon-based refrigerants. In addition, the structure is simpler than the evaporator of a conventional absorption chiller, simplifying the manufacturing work, and also making it possible to divide the refrigerant liquid into the refrigerant pipes and quickly remove the refrigerant vaporized in the refrigerant pipes. This is how it was done.

(d) Structure of the Invention The evaporator of the absorption chiller according to the present invention has an evaporation pipe line formed by a refrigerant pipe installed substantially horizontally and fitted with a large number of heat exchange fins, and a U-bend connecting the refrigerant pipe vertically. The liquid refrigerant inlet pipe, the gas vent pipe formed in the U-bend, and the refrigerant outlet pipe of this evaporation pipe are comprehensively housed in an airtight header, and the vaporized refrigerant is supplied to the absorber through this header. The refrigerant pipes, U-bends, heat exchange fins, etc. used in this evaporator are the same parts as the heat exchangers used in compression refrigerators using fluorocarbon-based refrigerants. This simplifies the manufacture of the evaporator and allows the refrigerant gas to quickly escape from the refrigerant pipes, thereby achieving the required cooling and heating function.

(e) Examples Examples of the present invention will be described below with reference to the drawings. In FIGS. 2 and 3, 8, 8'... are multi-stage refrigerant pipes in which a large number of heat exchange fins 9 are inserted and expanded, and the pipes and fins are fixed together; 10 is the refrigerant pipes 8, 8; '... is a U-bend that connects the top and bottom,
By installing the refrigerant pipes 8, 8' horizontally or slightly inclined, the upper liquid refrigerant sequentially flows down to the lower refrigerant pipe 8' through the U-bend. On the other hand, this U
The flow path including the bend 10 forms an evaporation pipe 11 that vaporizes most of the liquid refrigerant flowing down by heat applied through the heat exchange fins 9, refrigerant pipes 8, 8', . . .

As shown in FIG. 4, an opening 12 is formed upward at the starting end of the evaporation pipe line 11, and a liquid refrigerant inlet pipe 13 into which the liquid refrigerant from the condenser 20 is introduced is formed at the starting end of the evaporation pipe line 11.
is connected. Similarly, the terminal end is inserted into the heat exchange fin 9 as shown in FIG. A gas vent pipe 15 bent upward is fixed (see Fig. 6).

Note that the liquid refrigerant inlet pipe 13 may be constructed by bending the end of the refrigerant pipe 8, which has been expanded through the heat exchange fin 9, slightly upwardly. Reference numerals 16 and 16' denote headers that enclose these liquid refrigerant inlet pipe 13, refrigerant outlet pipe 14, and gas vent pipe 15, and form an airtight refrigerant gas chamber together with the tube plates 17 and 17' at both ends. A passage 19 communicating with the absorber 18 is formed in 16'.

The evaporator of this invention having such a configuration is
The refrigerant liquid flowing from the condenser 20 is guided from the liquid refrigerant supply pipe 23 to the opening 12, and while flowing down while wetting the insides of the refrigerant pipes 8, 8', heat of vaporization is applied from outside the pipe to evaporate it. The refrigerant gas is transferred to refrigerant pipe 8.
The gas flows from the U-bend 10 into the U-bend 10, and smoothly flows into the gas vent pipe 15.
5, the header 16, and the absorber 18.

The refrigerant liquid that could not be vaporized during the process of the refrigerant flowing down the evaporation pipe passes through the U-bend 10 and flows into the lower refrigerant pipe 8', and is transferred by the heat exchange fins 9 in the same way as described above. The heat obtained from the air outside the tube is given as heat of vaporization and becomes refrigerant gas.
Pass through the bend 10 and the gas vent pipe 15 to the header 16'
flows into.

The refrigerant liquid that could not be further vaporized even after flowing down each refrigerant pipe in this manner flows out from the refrigerant outlet pipe 14 to the bottom of the header 16, and is pumped up again to the upper refrigerant inlet pipe 13 by an appropriate pump. Alternatively, it flows out from the bottom of the header 16 to the absorber 18, is mixed with the absorption liquid, and is returned to the generator (not shown).

As described above, the evaporator of the present invention utilizes the evaporator tube of a compression refrigerator using a conventionally widely used fluorocarbon refrigerant to connect the starting end of the evaporation line to the U
Since a bend, a gas vent pipe, and a refrigerant outlet pipe are formed, there is no difficulty in forming a specially structured liquid reservoir or supply liquid reservoir in the header as in the conventional case, and it is possible to use ordinary refrigerant pipes and heat exchange fins. Fixation of the refrigerant pipe, connection of the refrigerant pipe with a U-bend with a gas vent pipe formed in advance, processing of the start and end ends of the refrigerant pipe, and the length of the U-bend and the length to provide a header containing the start and end of the refrigerant pipe for absorption refrigerators. It is possible to manufacture air-cooled evaporators.

Furthermore, the refrigerant gas in the refrigerant pipe flows into the U-bend from the upper and lower parts of the U-bend, and the refrigerant gas that flows into the U-bend smoothly flows into the gas vent pipe from the U-bend formed in a U shape and exits the gas vent pipe. Since the refrigerant gas flows to the header, the refrigerant gas can quickly flow out to the absorber.

As shown in Figs. 7 and 8, the refrigerant pipe can be further improved in thermal efficiency by using a finch tube having a thin spiral groove 21 inside, for example, a groove with a depth of about 2 mm and an angle β = 25° with the axial direction. However, when using trifluoroethanol as the refrigerant and using it as an evaporator of an absorption chiller, if the refrigerant pipe diameter is 15.9 mm or less, the spiral groove 21 can be formed without special surface treatment.
This alone will allow sufficient leakage inside the tube and improve heat transfer.

Furthermore, when using the evaporator of this invention using trifluoroethanol as a refrigerant, the specific volume of this refrigerant vapor is approximately 1/15 of water, and the refrigerant tube of the evaporator is heated by the conventional fluorocarbon refrigerator. Diameter 15.9 similar to exchanger
Even if a refrigerant pipe with a diameter of 9.52 mm or 9.52 mm is used, it is possible to provide a versatile air-cooled evaporator that can vaporize the refrigerant liquid, quickly drain the refrigerant vapor, and flow it down to the absorber.

Note that the starting end and the terminal end of the refrigerant pipe may be connected to the refrigerant pipe outside the header depending on the processing conditions for the refrigerant inlet and the refrigerant outlet.

(F) Effects of the Invention This invention forms an evaporation pipe line with multiple stages of refrigerant pipes fitted with a large number of heat exchange fins and mounted in a substantially horizontal direction, and U-bends connecting these refrigerant pipes vertically. The U-bend is provided with a gas vent pipe bent upward, and headers containing the U-bend and the gas vent pipe are provided at both ends, making the structure of the air-cooled evaporator extremely simple. It is only necessary to connect the U-bend with the gas vent pipe fixed to the refrigerant pipe, and furthermore, the evaporation pipe can be formed by holding pipes with the same pipe diameter, which greatly simplifies the manufacturing work of the evaporator. On the other hand, the refrigerant gas vaporized in the refrigerant pipe can smoothly flow into the gas vent pipe through the U-bend, and the refrigerant gas can quickly flow out to the absorber, making it possible to provide an efficient evaporator for an absorption chiller. It is something.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing an example of the conventional structure of an evaporator for an absorption chiller, FIG. 2 is a vertical cross-sectional view showing an example of the evaporator according to the present invention, and FIG. 3 similarly shows another embodiment. FIG. 4 is an enlarged partially cutaway view showing an example of the starting end of the evaporation pipe used in the evaporator of the present invention, FIG. 5 is an enlarged longitudinal sectional view showing an example of the ending end, and FIG. Similarly, FIG. 7 is an enlarged view of a partial cutout of the U-bend portion, FIG. 7 is a side view of a partial cutout showing an example of a refrigerant pipe, and FIG. 8 is a partial enlarged sectional view corresponding to A-A in FIG. 7. 8, 8'...Refrigerant pipe, 9...Heat exchange fin, 1
0... U bend, 11... Evaporation pipe line, 13... Liquid refrigerant inlet pipe, 14... Refrigerant outlet pipe, 15... Gas vent pipe, 16, 16'... Header, 23... Liquid refrigerant supply pipe, 18...Absorber.

Claims (1)

[Claims] 1 An evaporation pipe is formed by multiple stages of refrigerant pipes fitted with a large number of heat exchange fins and installed in a substantially horizontal direction, and a U-bend connecting these refrigerant pipes vertically, and the starting end of this evaporation pipe is A liquid refrigerant inlet pipe, a refrigerant outlet pipe with the end open, and a gas vent pipe bent upward at the U-bend are provided at both ends, and headers containing the gas vent pipe and the U-bend are provided at both ends to connect the liquid refrigerant inlet. An evaporator for an absorption chiller, characterized in that the pipe is provided with a liquid refrigerant supply pipe, and the header is provided with a communication port to the absorber.