RU2031328C1 - Method of operation of absorption-diffusion refrigerating plant - Google Patents

Abstract

FIELD: domestic equipment. SUBSTANCE: absorber strong solution is collected in vessel and supplied to level of boiling solution in boiler by means of tube of steam-lift pump; the level is higher is higher than drainage level of weak solution into absorber. Steam-lift pump operates due to steam of coolant which is got in boiler at conditions which are practically identical to evaporation from thin films of liquid. Steams of coolant are directed to condenser from the receiver. EFFECT: improved efficiency. 2 cl, 3 cl, 3 dwg

Description

 The invention relates to refrigeration and can be widely used in domestic refrigerators equipped with absorption-diffusion refrigeration units (ADHA).

 A well-known ADHA generator containing a vertical cylindrical housing with outlet fittings for a weak solution and refrigerant vapors and a nozzle for introducing a strong solution, an electric heater and a pump chamber and a thermosiphon arranged in series along the axis of the housing are connected along the axis of the housing. The ADHA generator is equipped with three coaxial cylinders mounted along the axis of the housing, forming annular gaps between themselves and the housing, the inner cylinder being sealed and containing a pump chamber, an electric heater and a thermosiphon, the upper end of which is brought into the cavity of the middle cylinder.

 A disadvantage of the known ADHA generator is the limited flow characteristics of the thermosiphon pump, due to the features of its design and operating parameters of the unit.

 Known ADHA (prototype), containing sequentially installed in the solution of a boiler, an absorber and a heat exchanger-regenerator, and the boiler is made in the form of a cylindrical vessel equipped with a heating jacket, and the absorber is placed horizontally at the level of the boiling solution in the boiler.

A disadvantage of the known ADHA is its low thermodynamic efficiency, since the design does not provide a high intensity of heat and mass transfer processes occurring in the unit. In particular, the design of the ADHA prototype does not allow evaporation of the solution under conditions practically equivalent to the evaporation mode from thin films of liquid. This is due to the fact that in the flooded boiler of the prototype, the heat flux from the heating surface is transferred to the liquid only by natural convection, especially at the initial stage of evaporation. More intense heat transfer process will be realized only in the nucleate boiling regime exists when a temperature difference between the heating surfaces and the saturation of the order of 5-7 ° ^C. Given that Adha domestic refrigerator operates in a batch mode, then repeated to achieve and maintain such a wall superheat associated with significant energy consumption in the production of cold.

 In addition, the design of ADHA - the prototype does not allow for a reduction in energy consumption to provide a more complete heat recovery between circulating substances, for example, due to direct heat transfer between a high temperature refrigerant vapor and a strong solution.

 The aim of the invention is to increase thermodynamic efficiency by intensifying heat and mass transfer processes.

 This goal is achieved by the fact that the boiler is equipped with two coaxial cylinders mounted along the axis of the housing, forming annular gaps between itself and the housing, the inner cylinder being hermetically connected to the housing, made with a lower muffled end and an electric heater placed in it, and the external cylinder with an open upper an end face located at the level of a strong solution in the receiver, but higher than the level of supply of a weak solution to the absorber, and a muffled lower end located with a gap relative to the housing and behind the inner end of the inner cylinder, while the gap between the inner and outer cylinders is connected at the bottom to the inlet of the strong solution inlet, and the steam cavity of the housing is connected by a steam line with the formation of a water seal to the lift pipe of the perlift pump, the upper end of which is inserted into the steam cavity of the receiver, and the lower end connected with the formation of a water seal to the container made from the lower part and the absorber.

 The heat exchanger-generator is of the “pipe in pipe” type and its heated cavity connects the receiver to the inlet of the strong solution, and the cooled cavity connects the outlet of the weak solution to the absorber.

 The steam pipe and the riser pipe of the steam lift pump are thermally coupled to the body and the heat exchanger-regenerator, for example, by means of a longitudinal weld.

 Comparative analysis shows that the inventive device differs from the prototype in that the boiler is equipped with two coaxial cylinders installed along the housing axis, forming annular gaps between itself and the housing, the inner cylinder being hermetically connected to the housing, made with the lower end face and in it an electric heater is placed, and the outer cylinder is made with an open upper end located at the level of a strong solution in the receiver, but above the supply level of a weak solution in the absorber, and a muffled lower end located with a gap relative to the housing and the closed end of the inner cylinder, while the gap between the inner and outer cylinders is connected in the lower part to the inlet of the strong solution, and the steam cavity of the housing is connected by a steam line with the formation of a water seal to the lift pipe of the lift pump, upper the end of which is inserted into the vapor cavity of the receiver, connected to the lower end with the formation of a water seal to the container made from the lower part of the absorber.

 This allows us to conclude that the claimed solution meets the criteria of the invention of "novelty."

 Comparison of the claimed device not only with the prototype, but also with other technical solutions in this technical field, allows us to recognize the claimed solution meets the criterion of "significant differences".

 The implementation of ADHA in the proposed manner allows to increase its thermal efficiency due to the intensification of heat and mass transfer processes. Since the level of the boiling solution in the boiler is located at the level of a strong solution in the receiver and above the level of draining the weak solution from the heat exchanger-regenerator into the absorber, the annular gap between the external cylinder and the housing is not filled, and this leads to the fact that after the exit (as a result of boiling) a vapor-liquid emulsion from the annular gap between the inner and outer cylinders, it is divided into refrigerant vapors directed into the steam line, and a weak solution flowing in the form of a film along the heated parts of the pyatilnika (outer cylinder and housing). In the process of solution draining, its turbulization occurs, as a result of which the thermal boundary layer located near the walls and representing the main thermal resistance to the heat flux is destroyed. This provides favorable conditions for the evaporation of the solution in the range of very small wall overheating due to intense heat transfer. Significant intensification of heat transfer in the ADHA boiler with small wall overheating is of considerable interest for household refrigeration equipment.

 The use of a steam lift pump as an executive unit to ensure circulation of a solution in a refrigeration unit allows not only to increase the ADHA capacity (cooling capacity) by increasing the circulation of substances, but also to deeply utilize the heat of the refrigerant vapor to heat the strong solution and then supply it to the boiler. This is due to the organization of ADHA, when the refrigerant vapor generated in the boiler, passing through the steam line, displaces the solution from the hydraulic solution and then enters the lift pipe of the perlift pump, forming a two-phase mixture that rises through the lift pipe into the receiver. The upward two-phase flow is characterized by a clearly expressed slug (piston) flow regime. The presence of a large number of refrigerant bubbles rising in the riser pipe significantly increases the contact surface of the phases, which ensures efficient rectification of the refrigerant vapor and heating of the strong solution due to the direct heat exchanger between the vapor and the liquid.

 Since the process of raising steam bubbles is quite long and depends on the height of the lifting pipe, the considered ADCA design option allows for complete heat recovery between the circulating substances and thereby reduce energy consumption for producing cold compared to known devices.

 Figure 1 shows a General view of ADHA; figure 2 is a longitudinal section of a boiler; figure 3 is a section aa in figure 2.

 The unit contains a vertical cylindrical boiler body 1 with a fitting 2 for injecting a strong solution, a fitting 3 for outputting a weak solution and a steam line 4, an electric heater 5, an absorber 6, a receiver 7, and a heat exchanger-regenerator 8.

 The unit is equipped with an external 9 and an internal 10 coaxial cylinders mounted along the axis of the housing, forming annular gaps between themselves and the housing 1, the inner cylinder being hermetically connected to the housing, made with a lower end face and placed in it an electric heater 5, and the outer cylinder is made with an open upper an end face located at the level of a strong solution in the receiver 7, but higher than the level of supply of a weak solution to the absorber 6, and a muffled lower end located with a gap relative to the housing 1 and the closed end vn the cylinder 10. The gap between the inner and outer cylinders is connected in the lower part to the strong solution inlet 2, and the steam cavity of the housing 1 is connected by a steam line 4 with the formation of a water seal to the lift pipe 11 of the steam lift pump, the upper end of which is inserted into the steam cavity of the receiver 7, and the lower end is connected to form a water trap to the container 12 made from the lower part of the absorber 6.

 The heat exchanger-regenerator 8 is of the “pipe in pipe” type and its heated cavity connects the receiver 7 to the strong solution inlet 2, and the cooled cavity connects the weak solution outlet 3 to the absorber 6.

 The steam line 4 and the lift pipe 11 of the steam lift pump are connected to the housing 1 and the heat exchanger-regenerator 8 in a heat ratio, for example, using a longitudinal weld. Figure 1 thermal connection of the lifting pipe 11 with the heat exchanger-regenerator 8 and the housing 1 is not shown.

 The boiler, steam line, heat exchanger-regenerator, lifting pipe of the steam lift pump and the receiver are closed by thermal insulation.

 The operation of the device is as follows.

 The internal cavity of ADHA is evacuated and filled with a water-ammonia solution with a mass concentration of 0.34 ... 0.36 kg / kg of solution and an inert gas (hydrogen) to a pressure of 1.9. ..2.1 MPa. The volume of the solution is chosen so that after filling the receiver 7 (to the level of the upper open end of the outer cylinder 9) and the cavities of the heat exchanger-regenerator 8 in the tank 12, the steam cavity remains empty to pass through it a cold vapor-gas mixture from the ADXA evaporator (not shown) into the absorber 6 With this filling of the tank 12, the hydraulic locks of the lifting pipe 11 and the steam line are simultaneously filled 4. The dimensions of the tank 12 are selected so that during the operation of ADHA, when as a result of partial evaporation the volume of the solution will decrease, the aforementioned water locks would be guaranteed to be filled with a strong solution.

 From the receiver 7, the strong solution is directed through the heated cavity of the heat exchanger-regenerator 8 into the gap between the outer 9 and inner 10 cylinders. As a result of heat removal from the electric heater 5, the strong solution boils, which leads to the exit of the vapor-liquid emulsion from the annular gap into the vapor cavity of the housing 1, in which it is divided into refrigerant vapors and a weak solution.

 A weak solution in the form of a film flows down over the heated parts of the boiler (external cylinder 9 and housing 1). In this case, it is re-evaporated under conditions of intense heat transfer with a small overheating of the wall. Next, a weak solution through the nozzle 3 and the cooled cavity of the heat exchanger-regenerator 8 enters the upper part of the absorber 6, and the level of discharge of the weak solution into the absorber is lower than the level of the boiling solution in the boiler.

 After separation from a weak solution, the refrigerant vapor accumulates in the cavity of the housing 1 and the steam drive 4. Due to the excess pressure, the refrigerant vapor squeezes the strong solution from the hydraulic solution of the steam pipe 4 and enters the riser pipe 11 of the steam lift pump. In this case, a two-phase mixture is formed, which rises through the riser pipe into the vapor cavity of the receiver 7. In the receiver, the strong solution and the refrigerant vapor are separated, which are practically clean and then go to a condenser (not shown). A strong solution accumulates in the receiver 7 to maintain the level of the boiling solution in the boiler. A constant inflow of steam from the boiler creates the conditions for achieving the greatest stabilization of a sufficiently powerful flow in the solution circulation system.

 After a decrease in the condenser, the liquid refrigerant is discharged into an ADHA evaporator, in which it evaporates into circulating hydrogen, which initially has a low partial pressure of ammonia, while producing a cooling effect and simultaneously increasing the concentration of ammonia vapor in circulating hydrogen. The rich hydrogen-ammonia mixture from the evaporator enters through the cooling cavity of the gas heat exchanger (not shown) into the tank 12 and then into the absorber 6, in which ammonia vapor is absorbed from it with a weak solution. In this case, the solution becomes strong and merges into the tank 12, and the hydrogen-ammonia mixture is freed from a significant amount of ammonia vapors and enters the depleted through the heating cavity of the gas heat exchanger into the ADHA evaporator. A strong solution from the tank 12 by means of a steam lift pump, working with the help of refrigerant vapor obtained in the boiler, is transported to the receiver 7. This completes the working cycle of the proposed unit.

 The tests showed that the steam lift pump provides a mass flow rate of liquid that is 4.5 ... 6 times higher than the flow rate of the thermosiphon pump that is currently widely used in ADXA designs (naturally, under similar operating conditions - pressure supplied by the electric power heater, height of liquid rise and pipe diameters). Based on the experimental data, it can be concluded that the proposed use of an airlift pump in ADHA is guaranteed and with lower energy consumption will ensure the solution rises to the height necessary for its circulation through the remaining units of the unit, and thereby increase the reliability of the ADHA as a whole.

 The implementation of the unit in the proposed way, when the steam pipe and the riser pipe of the elevator pump are connected with the body and the heat exchanger-regenerator in heat terms, for example, using a longitudinal weld, also increases the degree of heat use.

 Thus, the proposed technical solution allows to organize the ADHA operation of a household refrigerator with high thermodynamic efficiency by evaporating the solution under conditions almost equivalent to the evaporation mode from thin films and ensuring deep heat recovery between circulating substances by direct heat transfer. This reduces energy consumption during the production of cold by 15 ... 20% compared with the known units of similar refrigerating capacity.

 Positive test results of the inventive device open the way to create a whole gamut of highly efficient refrigeration units for household refrigeration equipment for various purposes (minibars, refrigerators, freezers, etc.). To ensure different cooling capacities, ADXA boilers with different flow characteristics can be used, the designs of which will differ significantly from the claimed device. However, the inventive concept common to such refrigeration units provides a basis for formulating a common way for them to work ADHA.

 A known method of operation of a hydrogen-filled absorption refrigeration unit with a receiver for a water-ammonia solution, an absorber for absorption with a weak solution of ammonia from an ammonia-hydrogen mixture and an evaporator for producing cold.

 The disadvantage of this method is the need for high heating of the solution in the boiler to ensure the normal operation of the thermosiphon.

 There is a known method (prototype), according to which an absorption-diffusion refrigeration unit is operating, comprising a boiler arranged sequentially in a solution, an absorber, a heat exchanger-regenerator and a heating jacket of a boiler, as well as a rectifier, a condenser, high and low temperature evaporators, a gas heat exchanger, a strong solution receiver and pipelines.

 When implementing the known method of operation of ADHA, a coolant is supplied to the heating jacket, the heat of which releases refrigerant vapor from the solution in the boiler, which are supplied to the condenser for reduction. A weak solution from the boiler through the pipeline goes to the heat exchanger-regenerator and then merges into the absorber, which is placed horizontally at the level of the boiling solution in the boiler.

 The disadvantage of this method of operation of ADHA is its low thermodynamic efficiency, due to the low intensity of heat and mass transfer processes occurring during its implementation.

 The purpose of the invention is to increase thermodynamic efficiency.

 This goal is achieved by the ADHA method of operation by evaporating refrigerant from a strong solution supplied from the receiver through a heat exchanger-regenerator in the boiler, condensing the refrigerant vapor in the condenser, evaporating the liquid refrigerant into an inert gas medium in the evaporator, and then transporting the cold vapor-gas mixture to the absorber to obtain a strong solution by absorption with a weak solution of refrigerant vapor. At the same time, a strong solution from the absorber is collected in a container and sent through a water trap to the riser pipe of the steam lift pump, which works with the help of refrigerant vapor obtained in the boiler and brought in by the steam line to form a water trap to the riser to supply the two-phase mixture to the receiver and then collect the strong solution in the receiver at the level of a boiling solution in a boiler, which is higher than the level of discharge of a weak solution into the absorber. From the receiver, refrigerant vapor is sent to the condenser.

 Comparison of the proposed method with the prototype made it possible to establish compliance with its criterion of "novelty." When studying other known technical solutions in this and related fields of technology, the features that distinguish the claimed invention from the prototype were not identified, because they provide the claimed method with the criterion of "significant differences".

 The inventive method was implemented by ADHA, a General view of which is shown in figure 1.

 The nature of the work of this ADHA was discussed in detail above, however, it should be added that for the implementation of the proposed method, boilers of completely different designs can be used, for example with one or more thermosyphons, which expands the scope of this method.

 The economic effect obtained by using the proposed method of operation of ADHA is achieved by increasing the thermodynamic efficiency of the refrigeration unit.

Claims (5)

 ABSORPTION-DIFFUSION REFRIGERATING UNIT AND METHOD OF ITS OPERATION.  1. Absorption-diffusion refrigeration unit containing a vertical cylindrical boiler body with fittings for entering strong and weak solutions, a steam line, an electric heater, an absorber, a receiver and a heat exchanger-regenerator, characterized in that, in order to increase thermodynamic efficiency, the boiler is equipped with axially mounted the housing by two coaxial cylinders, forming annular gaps between themselves and the housing, the inner cylinder being hermetically connected to the housing, made with a lower plug electric heater and the electric heater is placed in it, and the outer cylinder is made with an open upper end located at the level of a strong solution in the receiver, but higher than the level of supply of a weak solution to the absorber, and a muffled lower end located with a gap relative to the housing and the closed end of the inner cylinder, in this case, the gap between the inner and outer cylinders is connected in the lower part to the strong solution inlet fitting, and the steam cavity of the housing is connected by a steam line with the formation of a water seal to the lift pipe a pump whose upper end is introduced into the steam chamber of the receiver, and a lower end connected to form a water seal formed by the bottom of the absorber vessel.  2. The unit according to claim 1, characterized in that the heat exchanger-regenerator is made like a pipe in a pipe and its heated cavity connects the receiver to the inlet of the strong solution, and the cooled cavity connects the outlet of the weak solution to the absorber.  3. The unit according to claim 2, characterized in that the steam line and the riser pipe of the steam lift pump are connected with the housing and the heat exchanger-regenerator in thermal terms, for example, using a longitudinal weld.  4. The method of operation of the absorption-diffusion refrigeration unit by evaporating the refrigerant in the boiler from a strong solution supplied from the receiver through the heat exchanger-regenerator, condensing the refrigerant vapor in the condenser, evaporating the liquid refrigerant into an inert gas medium in the evaporator, and then transporting the cold vapor-gas mixture to the absorber obtaining a strong solution by absorption of a refrigerant vapor with a weak solution, characterized in that, in order to increase thermodynamic efficiency, the solution from the absorber is collected in a container and sent through a water trap to the riser pipe of the perlift pump, which works with the help of refrigerant vapor obtained in the boiler and brought in by the steam line to form a water trap to the riser to supply the two-phase mixture to the receiver, followed by the collection of a strong solution in the receiver at the boiling level solution in the boiler, which is higher than the level of discharge of a weak solution into the absorber, and the refrigerant vapor from the receiver is then sent to the condenser.

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