ES2556225B1 - Expansion, absorption and compression device for absorption machines - Google Patents

Abstract

The invention describes a device (1) for expansion, absorption and compression for absorption machines, comprising: an inlet cavity (2), which has a vapor phase coolant inlet (3) and a convergent nozzle (4) of concentrated solution inlet; a mixing throat (5) adjacent to the inlet cavity and coaxial with the convergent nozzle (4), which has a smaller passage area than that of the inlet cavity (2); and a diffuser (6) adjacent to the throat (5), comprising a first portion (6a) of increasing passage area and a second portion (6b) of passage area greater than the throat passage area (5) . In addition, this device (1) allows to control the flow of concentrated solution emitted by the convergent nozzle (4) by opening and closing alternately and completely its outlet end.

Description

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DESCRIPTION

Expansion, absorption and compression device for absorption machines OBJECT OF THE INVENTION

The present invention belongs to the field of absorption machines used to produce cold, heat, work, or a combination of them.

The object of the present invention is a new expansion, absorption and compression device, specially designed to improve the operability of an absorption machine, reduce its size and cost and additionally allow supplementing the production of cold and / or heat by consuming electricity to attend User demand, efficiently.

BACKGROUND OF THE INVENTION

The absorption machines in their classic implementation are heat pumps that consume primarily heat instead of primarily work and are used to produce cold or heat, usually from residual heat, geothermal energy, solar heat or heat generated specifically to activate them . When producing steam in an area inside the machine at a pressure higher than that prevailing in another area of the machine, where steam is absorbed, it can expand between both pressure levels in an expander or turbine, obtaining mechanical work, exclusively or Simultaneously to thermal production.

Fig. 1 shows an example of a cycle carried out by a single-effect absorption machine (100) using in this case an absorber (101), in this case conventional adiabatics. A refrigerant fluid circulates through a circuit at low pressure and evaporates in an exchanger called evaporator (102) thanks to the contribution of external heat. Next, the vapor phase refrigerant enters the adiabatic absorber (101), where it is absorbed by a solution concentrated in solvent to give rise to a diluted or weak solution at the outlet of the absorber (101). This weak solution is pumped by means of the impulsion pump (108) to pass to the generator (103), where the refrigerant is separated thanks to the supply of motive, or activation heat, coming from an external source. The refrigerant then passes to the condenser (104), where it gives heat to the outside, passing to

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liquid state, and from alK it passes back to the evaporator (102) through a refrigerant expansion valve (110), where it receives heat from the outside. The concentrated solution, meanwhile, returns to the absorber (101), expanding into the expansion valve of the solution (109).

Additionally, a heat exchanger (105) is usually used so that the ducts joining absorber-generator and generator-absorber exchange heat, thus preheating the weak solution before entering the generator (103) and cooling the concentrated solution before entering in the absorber (101), with the result of increasing the efficiency and effectiveness of the machine.

The absorber (101) is usually not adiabatic, but diabetic. As a result, it is a large, heavy and expensive component and sometimes difficult to control, since it also houses a mass transfer of the vapor to the liquid and within the liquid itself in addition to a heat transfer; all this in a two-phase flow, steam and liquid. The transfer of heat to the outside is necessary to evacuate the heat from the absorption of the refrigerant vapor by the solution. Separating both functions is an effective technique to reduce this size. Part or all of the heat transfer can be carried out in a heat exchanger whose internal flow is single phase, commonly called sub-cooler (106), which allows to reduce the size of the assembly that forms with the adiabatic absorber (101). When the concentrated solution begins to absorb steam in the adiabatic absorber (101), its temperature increases, causing a decrease in the absorption rate. If the absorber (101) is long enough, the adiabatic equilibrium is achieved upon exiting it. However, as the heat of absorption does not evacuate, it is not possible to reach the diabetic equilibrium within this absorber (101) but rather a balance is reached at a higher temperature, which leads to a lower absorption of refrigerant.

As a consequence, it is necessary to perform an external recirculation and a subcooling of the weak solution to continue absorbing. This recirculation is carried out with the help of a second pump (107) additional to the drive pump (108) normally arranged at the outlet of the absorber (101), which could increase the overall cost and complexity of the system.

In addition, certain refrigerants, such as ammonia, cause a large pressure difference between the high pressure zone at the outlet of the steam generator (103) and the zone of

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low absorber pressure (101), depending on condensation and evaporation temperatures. In the case of the amomaco refrigerant, even for temperature differences of just 15 ° C. The mechanical energy that originates from the concentrated solution due to this pressure difference generally degrades in a valve (109) through the viscosity of the solution, therefore without utility, resulting in an increase in thermal energy in the solution. concentrated.

Fig. 2 shows another example of a cycle that also includes a volumetric type expander, or a turbomachine machine, (111) that can obtain mechanical work by taking part or all of the steam emerging from the generator (103), which is voluntarily reheated to favor the expansion process. It allows converting the heat provided in the generator (103) into mechanical work on an axis, thus becoming a thermal motor, for example, producing electricity with an electric generator connected to it. Its fluid outlet is connected to the evaporator (102), since the outgoing fluid stream may contain liquid phase, or it may be at a temperature low enough to increase the capacity of the evaporator (102) in its function of receiving heat from the outside. Alternatively, its output can be connected to the absorber input (101).

DESCRIPTION OF THE INVENTION

The present invention solves the problems described above thanks to a device that produces expansion, absorption and compression. With this, it performs the functions of the adiabatic absorber and the expansion valve of the solution, in addition to acting as an ejector to compress the refrigerant vapor together with the solution, thus facilitating absorption and with the favorable consequence of reducing the pressure difference between absorber and generator.

In a first aspect of the invention, the expansion, absorption and compression device basically comprises three different parts: an inlet cavity, a mixing throat, and a diffuser. Next, each of these parts is described in greater detail.

a) Inlet cavity

The inlet cavity has a vapor phase refrigerant inlet and a

convergent nozzle of concentrated solution inlet. Steam inlet

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The refrigerant is connected to the duct from the evaporator, and can be made up of one or more inlet holes. The holes may take the form of a groove.

In another preferred embodiment of the invention, the hole (s) are perpendicular to the direction of the jet emitted by the convergent nozzle. In another preferred embodiment the hole (s) are tangential to the direction of the jet emitted by the convergent nozzle. And in another preferred embodiment, the hole (s) are parallel to the direction of the jet emitted by the convergent nozzle.

For its part, the convergent nozzle allows the concentrated solution from the generator and exchanger (105) to enter the device, as well as the recirculated from the device's own outlet, converting the high pressure difference existing in kinetic energy in form of free jet directed towards the throat of mixture.

According to a preferred embodiment of the invention, the convergent nozzle comprises means for progressively controlling the area of the fluid outlet end.

In another preferred embodiment, the convergent nozzle lacks progressive variation of its outlet area, but the means for controlling the area of the fluid outlet end works to open and close it completely alternately. In this preferred embodiment, the regulation of the flow is produced by complete interruption of the flow only part of the time, in a rapid periodic manner, by means of an object that acts as an obstacle commanded at will from the outside, which leaves the passage free. , or interrupts it. The average value of the flow obtained is thus determined by the frequency of actuation and the time that the passage is free to the flow.

In either case, the means for modifying the output area may be a longitudinally displaced coaxial spike, with a conical tip and axial displacement, which is electrically actuated.

The residence time of the jet in the inlet cavity is so short that even if the incoming solution is slightly overheated, there is no time

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material to desorb refrigerant steam.

In another preferred embodiment, the approach conduit to the outlet opening of the nozzle may comprise static elements inside it for printing a tangential velocity component to the concentrated solution jet. The purpose of these static elements, such as for example, is to increase mixing with the steam that occupies the inlet cavity.

b) Mixing throat

The mixing throat is adjacent to the inlet cavity and coaxial with the convergent nozzle, and has a smaller passage area than that of the inlet cavity.

When the stream of concentrated solution emitted by the convergent nozzle enters this throat, it drags and encompasses the refrigerant in the vapor phase, sucking it. This phenomenon occurs already from the narrowing of the cavity that involves the entry into the mixing throat, and continues in the mixing throat itself, depending on the opening of the jet and the overall dimensions of the device. As a result of this encompassing, a large number of bubbles and a very intense turbulent mixing is produced which favors rapid absorption of the refrigerant in a very small space. This contrasts with current adiabatic absorbers, which as mentioned are heavier and bulky. As a result of absorption there is an increase in the average density of the flow and pressure. The latter favors absorption.

c) Diffuser

The diffuser is contiguous to the throat, and comprises a first portion of the growing passage area downstream and a second portion of the passage area wider than the passage area of the mixing throat. In a preferred embodiment of the diffuser this section of the duct may be of constant passage area.

The increase in the area of passage of the first portion of the increasing area downstream can be progressive, for example conically, or sharply, for example with a stepped shape. In this first portion, the liquid-vapor mixture or the already fully liquid solution diffuses, reducing its energy

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kinetics. A part of this kinetic energy becomes an increase in additional pressure in the current. The increase in pressure favors the operation of the absorption machine as a heat pump. It can allow the evaporation and / or generation temperature to be lowered; it can allow to raise the temperature of condensation, and / or absorption; it can also allow to reduce the amount of solution existing in the machine and therefore its size; Or you can allow a combination of them. In addition, it is possible to increase the power of the machine as a heat pump and / or as a thermal engine by increasing the rate of coolant production.

The portion of the passage area greater than that of the throat, downstream of the diffuser, can be prolonged enough to improve absorption, given the low velocity of the fluid in that part because it is of a wide passage section.

A preferred embodiment of the device further comprises means for evacuating heat from the device without contact with the solution. This can be achieved, for example, by means of one or more ducts that totally or partially surround the inlet cavity, the mixing throat and / or the diffuser, thus helping the subcooler (106) in its task.

The described device, although it is presented applied to a simple basic effect machine, is applicable to multi-effect absorption machines, in their different variants, and even of half effect. It can also be applied to single-acting machines that include auxiliary elements to improve their efficiency and operability, outside the device described here. In addition to being applicable in absorption machines for the production of cold and / or heat, the device is also applicable in absorption machines intended exclusively for power production, such as those based on the Kalina or Goswani cycle.

Another preferred embodiment of the invention is directed to an absorption machine comprising an expansion, absorption and compression device as described.

A second aspect of the present invention is directed to a method of operation of a device such as that described in the previous paragraphs which comprises the step of controlling the flow of concentrated solution emitted by the convergent nozzle (4) by opening and closing alternately and in a manner Complete your exit end.

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BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 shows an example of a single acting absorption machine according to the prior art.

Fig. 2 shows an example of an absorption machine that includes an expander for obtaining work.

Fig. 3 shows an example of an expansion, absorption and compression device for absorption machines according to the present invention.

Fig. 4 shows an example of an absorption machine comprising an expansion, absorption and compression device according to the present invention, including the expander for obtaining work.

PREFERRED EMBODIMENT OF THE INVENTION

A concrete example of an expansion, absorption and compression device (1) according to the invention is described below with reference to the attached figures. For simplicity, similar reference numbers have been used to name similar elements in different figures.

Fig. 1 shows an absorption machine (100) according to the prior art employing a conventional adiabatic absorber (101). As described earlier in this document, this absorption machine (100) requires a valve (109) to reduce the pressure of the concentrated solution leaving the generator (103), as well as a second pump (107) to drive the recirculation of the weak solution.

Fig. 2 shows an absorption machine (100) similar to the previous one, but where an expander (111) connected between the generator outlet (103) and the evaporator (102) has been added to obtain additional work.

Fig. 3 shows a device (1) for expansion, absorption and compression, according to the present invention, where the different parts that comprise it are appreciated. An inlet cavity (2) receives the vapor phase refrigerant through an inlet port (3) and the concentrated solution through a convergent nozzle (4) whose section

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transverse at its outlet end can be controlled by axially displacing a pin (7) provided with a conical tip.

The pin (7) can be operated essentially in two different ways to control the flow emitted by the convergent nozzle (4). In a first mode, the pin (7) is actuated so that it gradually opens or closes the outlet area of the convergent nozzle (4). In a second mode, the pin (7) opens or closes periodically and completely the outlet area of the convergent nozzle (4), in accordance with an all-nothing mechanism. In any case, the pin (7) can be electrically operated, for example by means of a spring (8) that pushes the pin (7) axially towards the closed position and the mobile core of an electroiman (9) arranged in such a way that, when the electroiman (9) is activated, it counteracts the force exerted by the spring (8) and produces a rapid recoil of the spike that increases the opening of the nozzle (4). The interruption of the activation of the electroiman (9) causes the immediate return of the pin (7) due to the force of the spring (8), closing the outlet of the nozzle (4).

In addition, it is observed how the convergent nozzle (4) passes through the cavity (2) in the longitudinal direction of the device (1). In this way, when the concentrated solution exits through the convergent nozzle (4), a region of low pressure is created in the inlet cavity (2) that tends to suck and drag the refrigerant in the vapor phase that enters the entrance hole (3). During the passage of these fluids through the throat (5), a very intense turbulent mixing occurs that promotes the absorption of the refrigerant in the vapor phase in the solution, by increasing the contact surface and by renovating this surface. The increased pressure involved in dragging and mixing, as well as absorption, contribute to further promoting the absorption itself. The throat (5) ends in a diffuser (6) having a first conical area increase portion (6a) and a second wide area cylindrical portion (6b). In this diffuser (6) the kinetic energy of the mixture is reduced, appearing an additional pressure increase. As mentioned previously, both pressure increases favor the operation of the absorption machine (100 ’) as a heat pump. It also favors the absorption machine (100 ’) as a working producer by allowing a pressure in the evaporator (102) lower than that prevailing in the device (1).

Fig. 4 shows an absorption machine (100 ') comprising the absorption device (1) of the present invention, so that, in relation to the conventional absorption machine (100) of Fig. 1, it is possible remove the expansion valve (109) from the

solution and the second pump (107). This absorption machine (100 ') follows a cycle with three levels of pressure instead of the two levels of the cycle described in Fig. 1. In addition, the use of the pin (7) to control the outlet section of the nozzle Convergent (4) allows to control the operation of the absorption machine (100 ') completely better.

5 As a consequence, the machine (100 ') can be better adapted to the demands of cold, heat and mechanical power and the temperatures of the at least four heat exchangers that constitute the thermal interface of the machine (100') with external heat flows.

10 This configuration has an additional advantage. Increasing the flow through the recirculation pump (108) and properly regulating the valve downstream of it that divides the flow between the one that goes to the generator (103) and the one that goes to the subcooler (106), increases the solution flow which is made to reach the nozzle (4) of the device (1). This has the effect of enhancing the increase in pressure that occurs in the device (1) and with it the

15 amount of refrigerant absorbed. Increasing the flow of liquid can increase the flow of refrigerant that can be absorbed. The result is an increase in the ability to pump heat. This makes the operation of this machine more flexible (100 ’), since it can increase its heat pumping capacity efficiently, simply by voluntarily consuming more electricity in the pump (108).

Claims (16)

5 10 fifteen twenty 25 30 35 1. Device (1) for expansion, absorption and compression for absorption machines, characterized in that it comprises: an inlet cavity (2), which has a vapor phase refrigerant inlet (3) and a concentrated solution inlet nozzle (4); a mixing throat (5) adjacent to the inlet cavity and coaxial with the convergent nozzle (4), which has a smaller passage area than that of the inlet cavity (2); Y a diffuser (6) adjacent to the throat (5), comprising a first portion (6a) of increasing passage area and a second portion (6b) of passage area greater than the throat passage area (5). 2. Device (1) according to claim 1, wherein the convergent nozzle (4) comprises a means for progressively modifying the area of its outlet end. 3. Device (1) according to claim 1, wherein the convergent nozzle (4) comprises means for closing or opening completely and alternatively the area of its outlet end. 4. Device (1) according to any of claims 2-3, wherein the means for modifying the area of the outlet end of the convergent nozzle (4) is an electrically operated longitudinal displacement coaxial pin (7). 5. Device (1) according to claim 4, further comprising a spring (8) that pushes the pin (7) axially towards the closed position and an electro-handle (9) which, when activated, counteracts the force exerted by the dock (8). 6. Device (1) according to any of the preceding claims, wherein the first portion (6a) of increasing passage area has a conical shape. 7. Device (1) according to any of claims 1-5, wherein the first portion (6a) of increasing passage area has a stepped shape. 8. Device (1) according to any of the preceding claims, wherein the vapor phase refrigerant inlet (3) comprises one or more holes. 5 10 fifteen twenty 25 9. Device (1) according to claim 8, wherein the hole (s) are perpendicular to the direction of the jet emitted by the convergent nozzle (4). 10. Device (1) according to claim 8, wherein the hole (s) are tangential to the direction of the jet emitted by the convergent nozzle (4). 11. Device (1) according to claim 8, wherein the hole (s) are parallel to the direction of the jet emitted by the convergent nozzle (4). 12. Device (1) according to any of the preceding claims 8-11, wherein the hole (s) are grooves. 13. Device (1) according to any of the preceding claims, which further comprises means of evacuation of heat without contact with the fluids. 14. Device (1) according to claim 13, wherein the heat evacuation means comprise one or more ducts that totally or partially surround the inlet cavity (2), the mixing throat (5) and / or the diffuser (6). 15. Absorption machine (100 ') comprising an expansion (absorption) and compression device (1) according to any of the preceding claims. 16. Operating method of a device (1) according to any of the preceding claims 1-14, characterized in that it comprises the step of controlling the flow of concentrated solution emitted by the convergent nozzle (4) by opening and closing alternately and completely its output end