Fluidic Device

Abstract

A fluidic device comprising an inlet passage for receiving a heat vaporizable supply liquid, a main power nozzle connected to the inlet passage, a pair of outlet passages communicated through an interaction chamber with the outlet of the power nozzle and at least one, preferably a pair of by-pass control passages for directing the main stream of liquid through the device to one or the other of the outlet passages. The by-pass control passage communicates the inlet passage directly with the interaction chamber by-passing the power nozzle. It includes heating means for vaporizing the flow of liquid therethrough. A small portion of the main liquid stream through the inlet passage of the device is diverted to the control by-pass to be used as control flow. During passage through the control by-pass, the control liquid flow may be vaporized into gas flow by heating means. The vaporization of the control liquid causes a decrease in the mass flow of the control fluid which is effective to produce a transverse pressure differential across the main liquid stream through the interaction chamber sufficient to bias it for flow through the desired one of the two outlet passages. A refrigeration system includes a pair of evaporators, means for supplying a liquid refrigerant to the evaporators and a fluidic device of the type described. The fluidic device is provided between refrigerant supplying means and a pair of evaporators with its inlet passage connected to refrigerant supplying means for receiving the refrigerant and each of its two outlet passages connected to respective one of the evaporators. Heating means on the control by-passes are adapted to be operated in response to predetermined temperature conditions within the spaces where the evaporators are disposed so as to bias the flow of refrigerant through the fluidic device to one or the other of its outlet passages for supply into corresponding one of the evaporators.

Description

BACKGROUND OF THE INVENTION

This invention relates to a thermally controlled fluidic device and an apparatus having such fluid device incorporated therein.

Fluidic devices have been known and used primarily in logic circuit applications. Such devices also offer distinct advantages as reliable low cost value means for controlling relatively large volume flows of liquid in recirculation systems. The desired control function is accomplished by the actions and interactions of moving fluid without the aid of mechanical moving parts such as flappers, piston, or diaphragms The absence of the mechanical moving parts in a fluidic device assures dependable, trouble-free control operation for a extended period of time. Although such is the nature of the fluidic device itself, conventional fluidic devices generally have associated auxiliary mechanism for providing requisite control input in the form of control flow of fluid to the control port or ports of the devices and one or more mechanical moving parts are inevitably included in the mechanism. For example, some conventional fluidic devices have one or two control ports and they are connected to a control fluid source for receiving the control flow of fluid which is the control input to the device. The control fluid source is separate from and independent of a main power source of the fluidic device and the supply of the control flow of fluid to the control ports are controlled by suitable valve means such as solenoid valves, throttle valves, flappers, or diaphragms which are interposed between the control source and the control ports of the fluidic device. The fact that mechanical valve means are connected to the control ports of the fluidic device and that they are easily subject to operational troubles and difficulties due to, for example, abrasion, wear down and the like tend to kill or offset the distinct advantages of the fluidic device itself. Accordingly, in order to make the best use of the benefits inherent to the fluidic device it is highly desirable to provide a control mechanism for the device which is entirely free of mechanical moving parts. Also, it is still more preferable if such control mechanism is to be inexpensively provided without causing substantial design change of the conventional fluidic device.

In operation of the fluidic device, switching control of the main flow of fluid is effected by causing a transverse pressure differential across the main flow of fluid sufficient to bias it to one or the other of a pair of output or outlet ports. The desired transverse pressure differential is in turn created by applying control input in the form of the control flow of fluid through one or two control ports to the main flow.

Incidentally, it is generally known to those well versed in hydrodynamics that the volumetric flow Qv and mass flow Qm of a viscous fluid flowing through a small and elongated passage such as a capillary tube or pipe could be expressed by the following formulas:

Qv = (.pi. `a.sup.4)/(8 .mu.) .sup.. (.DELTA. P)/(L) 1. Qm = (.pi. a.sup.4)/(8 .nu.) .sup.. (.DELTA. P)/(L) 2.

wherein

A: radius of the capillary tube

.mu.: Coefficient of viscosity of the fluid through the tube

.nu.: Coefficient of kinetic viscosity of the fluid through the tube .DELTA. P : Pressure differential between the inlet and outlet of the capillary tube

L : The length of the tube

Considering now a ready-to-vaporize liquid refrigerant such as one known under the trademark of Freon R-12, it has a coefficient of viscosity in gas form approximately one twentieth of that in liquid form. While on the other hand, it possesses a coefficient of knetic viscosity in gas form approximately ten times as great as that in liquid state. Accordingly, as can be induced from the above mentioned formulas 1 and 2, the tube length L and the pressure differential .DELTA.P being the same the volumetic flow Qv of the refrigerant R-12 as it passes the capillary tube in gas form increases greater than as it passes in liquid form, while its mass flow as it passes the tube in gas form decreases substantially less than as it passes in liquid form. The present invention is based on this fluid phenomena and contemplates to use it in obtaining the desired switching control of the flow of fluid through fluidic devices.

It is, therefore, a primary object of this invention to provide a new and improved fluidic device for switching the flow of fluid with small control signals utilizing the above mentioned fluid phenomena.

It is another object of this invention to provide a new and improved fluidic device for switching the flow of fluid which operates with high reliability for an extended period of time.

It is another object of this invention to provide a new and improved fluidic device for switching the flow of fluid which has no mechanical moving parts.

It is another object of this invention to provide a new and improved fluidic device for switching the flow of fluid having thermal means operative to produce necessary control signals.

It is still another object of this invention to provide a new and improved refrigeration system having a plurality of evaporators and at least one fluidic device of the nature described for controlling the flow of refrigerant to the evaporators in order to keep the temperatures thereof within predetermined ranges.

It is still another object of this invention to provide a new and improved refrigeration apparatus including a freezer compartment and a fresh food compartment and having incorporated therein a fluidic device of the nature described for controlling the flow of refrigerant to one or the other of the evaporators disposed within the freezer and fresh food compartments, respectively, thereby to maintain the freezer and fresh food compartments within their predetermined temperature range.

SUMMARY OF THE INVENTION

In accordance with one aspect of this invention, there is provided a fluidic device comprising an inlet passage for receiving a heat vaporizable liquid and a main jet nozzle communicated with the inlet passage. The fluidic device also includes a pair of outlet or output passages connected through an interaction region to the outlet of the jet nozzle. ready-to-vaproizable least one, preferably a pair of control passages are provided to connect the inlet passage with the interaction chamber by-passing the main jet nozzle. More specifically, a first control by-pass extends from one side wall of the inlet passage to a first control outlet formed in a one side wall of the interaction leading to the first outlet passage, while a second control by-pass extends from the other side wall of the inlet passage to a second control outlet made in the other side wall of the interaction chamber leading to the second outlet passage. A portion of the read-to-vaporizable liquid supplied to the inlet passage of the fluidic device is diverted into the control by-passes to be used as control input. Each of the control by-passes has heater means for vaporizing control liquid through the by-passes. In order to direct the main stream of liquid to one or the other of the outlet passages, heater means of the control by-passes are selectively energized. If heating means of one control by-pass is energized and heating means of the other by-pass control is not energized the control liquid through the heated control by-pass is vaporized into gas stream and the gaseous control fluid flows through the control outlet into the interaction chamber. Due to a substantially lower mass flow of a gas stream through a small passage such as a capillary tube with respect to that of a liquid stream, the vaporization of the control liquid through one control by-pass creates a sufficient transverse pressure differential across the main stream of liquid through the interaction chamber which tends to bias it to the side wall of the interaction chamber wherein the gaseous control fluid is flowing from the control outlet. The main stream of liquid then flows out the outlet passage communicating with this this side wall. For the purpose of causing a greater reduction in the mass flow of the vaporized control flow as it passes the control by-pass, the control by-pass may preferably be so designed that the portion of the by-pass downstream of the heater means has a greater flow resistance than the portion upstream of heater means. In accordance with the present invention, this may be accomplished in varied ways. In one way, the control by-pass may be made to have a longer downstream portion than the upstream portion. Or it may be formed to have a greater cross sectional flow area in the downstream section than in the upstream section. Alternatively, suitable flow restricting means in the form of a constriction or orifice may be provided in the control by-pass at a position downstream of the heater.

In accordance with the present invention, there is also provided a refrigeration system including a pair of evaporators and means for supplying circulating a liquid refrigerant to both of the evaporators and a fluidic device of the nature described. The fluidic device is provided between refrigerant supplying means and a pair of the evaporators with its inlet passage connected to refrigerant supplying means for receiving the refrigerant and each of its two outlet passages connected to respective one of the evaporators. Heater means of the first control by-pass is so related to a first evaporator that the energization of the heater may depend on the temperatures of the first evaporator. Heater means of the second control by-pass is also related to the second evaporator in the same manner. When the temperature of the first evaporator rises to a predetermined value, heater means on the first control by-pass is automatically energized to bias the flow of refrigerant through the fluidic device toward the first outlet passage for flow into the evaporator. The energization of the heater is continued until such time as the temperature of the first evaporator reaches to a predetermined lower level. Similarly, when the temperature of the second evaporator rises to a predetermined upper level, heater means on the second control by-pass is automatically turned on thereby to switch the flow of refrigerant through the fluidic device for flow through the second outlet passage and into the second evaporator. The heater is kept in energized state until a desired minimum temperature of the second evaporator is attained. The temperatures of the two evaporators are thus maintained within the desired ranges through the automatic switching control over the flow of refrigerant by the fluidic device.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a plan view showing the basic profile of a fluidic element embodying one form of this invention and having control by-pass with a longer flow path downstream of heating means;

FIG. 2 is a plan view showing the basic profile of a fluidic element embodying another form of this invention and having control by-passes with a flow path of reduced cross sectional area at the downstream of heating means;

FIG. 3 is a plan view showing the basic profile of a fluidic element embodying another form of this invention and having control by-passes formed with a constriction at a point downstream of heating means;

FIG. 4 is a plan view showing the basic profile of a fluidic device embodying still another form of this invention and having control by-passes provided with a constriction at a point within heating means;

FIG. 5 is a graphic representation showing the relation of the mass flow of gaseous control fluid through the control by-passes with respect to the pressure differential between inlet and outlet end portions of the control by-passes of a fluidic element which has no constriction in its control by-passes;

FIG. 6 is a graphic representation showing the relation of the mass flow of gaseous control fluid through the control by-passes with respect to the pressure differential between inlet and outlet end portion of the control by-passes of a fluidic element according to this invention and having a constriction in its control by-passes;

FIG. 7 is an exploded perspective view in enlarged scale of a fluidic device made in accordance with the present invention; and

FIG. 8 is a schematic diagram showing a multi-evaporator type refrigeration system having a fluidic device of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawing and in particular to FIG. 1, there is schematically illustrated the basic configuration or profile of a wall attachment type fluidic element embodying one preferred form of this invention. As shown, the fluidic element includes an inlet passage 10, for receiving supply fluid through the element. The inlet passage 10 communicates through a reduced power nozzle portion 12 with an enlarged interaction region or chamber 14 which in turn is communicated with a pair of diverging outlet or output passages 16 and 18.

A pair of small elongated control passages 20 and 22 are symmetrically provided to connect the inlet passage 10 to the interaction region 14 by-passing the nozzle portion 12. More specifically, one control by-pass 20 has an inlet port 21a provided in one side wall of the inlet passage and extends in general form of U to an control outlet 21b formed in the corresponding side wall 24 of the interaction region at a point adjacent and just downstream of the nozzle section 12. Similarly, other control by-pass 22 has an inlet opening or port 22a formed in the other side wall of the inlet passage 10 at a location directly opposite the inlet port 21a of the first control by-pass 20 and extends in general U form to a control outlet 22b made in the corresponding side wall 26 of the interaction chamber at a point adjacent and downstream of the nozzle section in direct opposite relation with respect to the outlet 21b of the first U-shaped control by-pass. For the purpose of hereinafter explained, electric heater means 28 and 30 are provided around the by-pass control passages 20 and 22, respectively, at a suitable location thereof to partially cover the passages.

With this construction of the fluid element, a suitable heat vaporizable liquid such as the liquid refrigerant known under the trademark of Freon R-12 is supplied to the inlet passage 10 and it flows through the main nozzle 12 in power jet into the interaction chamber 14. Meanwhile, a portion of supply liquid provided to the inlet passage is diverted to the control by-passes 20 and 22 and flows through their respective control outlet into the interaction chamber 14 of the fluid device as indicated by the arrows.

In order to direct the main stream of liquid through the fluidic device to one or the other of the outlet passages 16 and 18, in accordance with the usual fluid amplifier practice, a sufficient transverse pressure differential must be created across the main stream of liquid as it emerges in power jet from the nozzle which tends to bias it toward one of side walls 24 and 26 of the interaction chamber for flow therealong. For this purpose in accordance with the present invention the heaters 28 and 30 may be selectively energized. More specifically, if the first heater element 28 placed to partially surround the first control by-pass 20 is energized, the control flow of liquid through the first control by-pass is heated up to substantially vaporize into gas phase by the heater and the vaporized gas stream flows out the control outlet 21b of the first control by-pass. As explained hereinabove, when the control lo liquid flow is turned into a gas stream in the small elongated by-pass control passage 20 its mass flow is substantially decreased. While on the other hand, since the second heater element 30 disposed to partially surround the second control by-pass 22 is not yet energized the control flow passes the by-pass in normal liquid form with relatively higher mass flow rate as compared with the gaseous control flow through the first control by-pass.

An incessant flow of the power jet emerging from the nozzle through the interaction chamber tends to draw or entrain the control flows out of the both control by-passes 20 and 22. Under the above mentioned condition a relatively large amount of control fluid is drawn from the non-heated second control by-pass than from the heated first control by-pass as viewed in terms of the mass flow. The fact is due to the described difference of the mass flow of fluid in its liquid state and gas state. As the result, the pressure in the area of the first control outlet 21b of the heated first control by-pass decreases with respect to the second control outlet 22b of the non-heated second control by-pass which will cause a transverse pressure differential across the main jet stream of liquid through the interaction chamber 14. This transverse pressure differential tends to cause the stream of liquid to attach itself to the side wall 24 of the interaction chamber where the control outlet 21b of the first control by-pass is made so that it will flow out through the first outlet passage 16.

On the other hand, if the first heater 28 is deenergized and the second heater 30 of the second control by-pass 22 is then energized, the control liquid into the second control by-pass is substantially vaporized by the heater and flows through the control by-pass in gas stream. The portion of the control liquid diverted into the non-heated first control by-pass 28 flows therethrough in liquid form. Due to a relatively small mass flow of the gaseous control fluid through the heated second control by-pass 22 with respect to that of the control liquid through the first control by-pass 20, a transverse pressure differential is created in substantially the same manner as discussed above across the main jet stream of liquid through the interaction chamber which tends to cause the main liquid stream to detach itself from side wall 24 and switch over into attachment to side wall 26 so that it will flow out through the second outlet passage 18.

When it is desired to switch the main stream of liquid back to the first outlet passage 16, the second heater 30 is turned off and the first heater element 28 of the first control by-pass is again turned on to vaporize the control liquid through the first by-pass. The fluidic element of the present invention may be so designed that the main liquid stream through the element may flow out the both outlet passages at substantially the same rate under such condition where no control signal are applied i.e. neither of the two control heaters 28 and 30 is energized. It may also be designed such that both of the heaters are normally energized providing a no signal or control state and they are adapted to be selectively deenergized to switch the main liquid flow to either the first or second outlet passage.

As can be easily understood by those skilled in the art, when a vaporizable fluid is to be heat vaporized in a small passage such as a capillary tube or the like it causes an instantaneous pressure rise and the generated high pressure proceeds through the passage. If such high pressure occurring in the control by-pass during heat vaporization of the control liquid by the heater, it proceeds downstream through the control by-pass and tends to disturb the desired low pressure condition which is produced in the area of the control outlet as the result of a decrease in the mass flow of the control fluid caused by the heat evaporation. This in turn may disturb the desired transverse pressure differential across the main liquid stream and result in erratic operation of the fluidic element during which the stream of liquid cannot be switched over to the desired direction. Accordingly, it is essential to provide means for preventing the instantaneous high pressures from proceeding downstream through the control by-passes.

Moreover, in order to provide a quick and assured switching of the main stream of liquid through the fluidic device of this invention, it would be preferable to produce a greater transverse pressure differential across the main stream. A greater transverse pressure differential is obtained by causing the pressure in the area of one of the control outlets 20 and 22 to decrease as much as possible with respect to the pressure in the area of the other of the control outlets. As is apparent from the foregoing description, a greater pressure reduction at a control outlet may be attained through reducing the mass flow of the control fluid through the corresponding control by-pass to a greater extend. One way to achieve this is to have a greater resistance against the mass flow of the control fluid.

According to this invention, in order to attain the above described purposes, the control by-passes are so designed to have a greater flow resistance in the portion downstream of the heating elements than in the portion upstream of the heating elements. In the fluid device illustrated in FIG. 1, this has been accomplished by making the downstream flow sections 32 and 34 of the control by-passes 20 and 22 between the respective heater elements 28 and 30 and control outputs 21b and 22b much longer than the upstream flow sections 36 and 38 between the respective heater elements and inlet openings 21a and 22a. With this arrangement of the control by-passes 20 and 22, the instantaneous high pressures occurring at the heating sections during heat vaporization of the control flows of liquid by the heaters 28 and 30 are not allowed to proceed downstream through the by-passes to interaction chamber due to a greater flow resistance of the downstream flow sections 32 and 34. Instead, the high pressures move upstream from the heating sections through the upstream flow sections 36 and 38 of a lower flow resistance into the inlet passage 10. Accordingly, any possibility of the high pressures caused at the heating sections of the control by-passes adversely affecting the desired low pressure conditions at the control outlets, thus the desired transverse pressure differential across the main flow of liquid through the interaction chamber is effectively eliminated assuring normal expected control operation of the fluidic device. Moreover, the longer flow passage of the control by-passes downstream of the heating elements presents a larger flow resistance against the gaseous control stream produced at the heating sections and moving downstream through the control by-passes. This is effective in additionally reducing the mass flow of the gaseous control fluid, which in turn assists in creating a greater transverse pressure differential across the main stream of liquid through the fluidic device.

In the embodiment illustrated in FIG. 2, the desired greater flow resistance in the portion of the control by-passes downstream of the heater elements is provided by making downstream flow sections 32 and 34 to have a smaller diameter than the upstream flow sections 36 and 38. The construction is also effective in preventing the high pressure caused at the heating sections of the control by-passes from proceeding downstream therethrough and in crating a greater transverse pressure differential across the main liquid stream through a reduction in the mass flow of one control fluid.

In another embodiment illustrated in FIG. 3, the control by-passes 20 and 22 are respectively formed with constrictions 40 and 42 in the form of an orifice at a location adjacent and downstream of the heating elements 28 and 30. The constriction orifices 40 and 42 adds a sufficient flow resistance to the downstream sections 32 and 34 of the control by-passes which performs a dual function of preventing the instantaneous high pressures caused at the heating section during the heat vaporization of the control liquid from proceeding downstream through the control by-pass as well as reducing substantially the mass flow of vaporized control fluid as it passes the downstream section in the manner essentially similar manner as explained above. These flow restricting constrictions are advantageous in that they eliminate the need of a longer downstream flow path as is the case with the fluid element of FIG. 1. The fact enables a small and compact construction of a fluidic element.

An additional feature of accomplishing a higher heat vaporization efficiency may be obtained by making the constricted parts 40 and 42 within the heating sections of the control by-passes 20 and 22 i.e. within the portions of the control by-passes surrounded by the heater elements 28 and 30 as shown in FIG. 4. This is attributed to the fact that it is easy to heat the stream of liquid flowing through a narrower space. The constrictions or orifices 40 and 42 provide narrower spaces through which the control liquid to be heat vaporized flows.

The benefit of forming constricted orifices in the control by-passes can also be clearly understood with reference to FIGS. 5 and 6 which show in graphic representation the relation of the mass flow of the control fluid through the downstream section of the control by-pass with respect to the pressure differential between the opposite ends of the downstream section. If the fluidic element of this invention has no constrictions in its control by-passes, the relationship between the control fluid flow through the downstream section and the pressure differential generally presents itself as shown by the straight line in FIG. 5. Thus, as the pressure differential between the opposite ends become greater due to higher pressure occuring upstream of the orifice the mass flow of the control fluid through the downstream section of the control by-pass increases accordingly. In other words, if the control by-pass has no constriction orifice any pressure rise caused in the portion of the control by-pass upstream of the orifice may give direct and undesirable effect upon the mass flow of gaseous control fluid through the downstream section of the control by-pass in that an increase in the mass flow of the gaseous control fluid brings about a corresponding pressure rise in the area of the control outlet resulting in a failure of creating a sufficient transverse pressure differential across the main stream of liquid necessary for the desired switching control thereof.

Whereas in the fluidic element of this invention which has the constriction orifices in the control by-passes the above mentioned relation manifests itself as shown by the curve line of FIg. 6. In this case an increasing pressure differential does not necessarily cause a corresponding increase of the mass flow. The rate of increase in the mass flow is substantially lower than that of the pressure differential and as the pressure differential exceeds a certain point the rate of increase in the mass flow reduces to such small degree as to be considered substantially zero phrased differently, unusual higher pressure condition occuring in the portion of the control by-pass upstream of the constriction gives no substantial increase in the mass flow of the gaseous control fluid through the downstream section of the control by-pass and, accordingly, the gaseous control fluid flows at essentially the same predetermined rate independent of the upstream higher pressure thereby to create the desired transverse pressure differential across the main stream of liquid through the fluidic element. This is entirely due to the fact that the presence of the constrictions in the control by-passes is effective to prevent undesirable upstream higher pressure from proceeding downstream through the control by-passes. Thus, the simple constrictions provides effective and inexpensive means for assuring the proper, expected operation of the fluidic element.

FIG. 6 illustrates in exploded perspective view a typical fluid device constructed in actual practice according to teaching of this invention. The fluid device includes a top cover member 55 and a bottom base member 52 made preferably of a suitable synthetic resin material. The upper surface of the base member 52 is recessed downwardly in general accordance with the basic profile disclosed in FIGS. 1 to 4, thereby to form essential fluid flow paths. The recessed portion comprises an inlet passage 54 for receiving source fluid. The inlet passage communicates through a power jet nozzle 56 of reduced width with a relatively enlarged interaction region 58 defined by spaced, elongated side walls 60 and 62. These side walls extend in diverging manner towards the lower end of the bottom base member 52 and terminate at the semicircular end wall 64 and 66. A V-shaped intermediate splitter section 68 is formed between the diverging side walls 60 and 62 at the end opposite the inlet end. The side wall 60 and the intermediate section 68 define a first outlet or output passage 70, while side wall 62 and the intermediate section 68 define second outlet or output passage 72, with both of the outlet passages communicating with the inlet passage 54 through the interaction chamber 58 and the restricted power jet nozzle 56.

The recessed profile further includes a pair of upper control inlets 74 and 76 which are generally perpendicularly connected to the opposite side walls of the inlet passage 54 at their one end and terminate at their other end in circular holes 74a and 76a, respectively. The control inlets 74 and 76 are substantially identical in configuration and are disposed in mutual alignment. A pair of control outlets similar to the control inlets are formed to extend generally perpendicularly to the direction of the main stream of liquid through the device. As shown, the control outlets 78 and 80 communicate at their one end with the interaction chamber 58 through outlet ports 78b and 80b formed in direct opposite alignment in side walls 60 and 62 at positions adjacent and just downstream of the power nozzle 56. The other ends of the control outlet 78 and 80 terminate in circular holes or cavities 78a and 80a, respectively.

The top cover member 50 is adapted to be superimposed on the bottom base member 52 and includes a relatively large inlet opening 82 made in alignment with the upper or upstream end portion of the inlet passage 54. It also has a pair of relatively large outlet or output openings 84 and 86 formed in positions corresponding to the lower or downstream ends of the first and second outlet passages 70 and 72, respectively. An inlet or supply conduit 88 is fixedly mounted in the inlet opening 82, while outlet conduits 90 and 92 are fixedly planted in the outlet openings 84 and 86, respectively. A U-shaped tube 94 of relatively small diameter is vertically set up in the upper member 94 such that one open end of the tube may come into registry and communication with the recessed circular cavity 74a of the one control inlet 74, while the other open end with the recessed circular cavity 78a of the one control outlet 78 on the same side as the control inlet 74 when the top cover member 50 is placed in position on the bottom base member 52. A second generally U-shaped control tube 96 substantially similar to the first mentioned control tube 94 is also set vertically on the top cover member 50 such that one open end of the tube may be brought in registry and communication with the recessed circular cavity 76a at the end of the right control inlet 76 while the other open end with the recessed circular cavity 80a at the end of the right control outlet 80.

As shown in the drawing, the first and second control tubes 94 and 96 are equipped with electric heater 98 and 100. Heaters 98 and 100 are placed in heat transfer relationship to partially surround the tubes 94 and 96, respectively, at a position adjacent their upper ends. These heaters may suitably be connected to electric power supply through control means. The control tubes have also formed therein constrictions 102 and 104 at a location closest to the electric heaters 98 and 100.

With the above arrangement, when the top cover member 50 is assembled in place on the bottom base member 52 to complete a fluid device, the first U-shaped control tube 94, left control inlet 74 and left control outlet 78 together form a first control by-pass of the fluid device together form a first control by-pass which corresponds to the first control by-pass 20 shown in the basic profiles of FIGS. 1 to 4. The second U-shaped control tube 96, right control inlet 76 and right control outlet 80 form a second control by-pass corresponding to the second control by-pass 22 of the basic profiles. It should be appreciated that in order to obtain better control results the first and second control by-pass means should preferably made such that they are precisely identical in construction and size. The top cover member 50 and bottom base member 52 are assembled together in tight sealing engagement to complete a fluid device.

In operation of the fluid device, a suitable vaporizable operation liquid supplied through the inlet conduit 88 to the inlet passage 54. Substantial portion of the source liquid provided to the inlet flows through the main jet nozzle 58 into the interaction chamber 58 while a relatively small amount of the liquid is diverted into the pair of the control tubes 94 and 96 through the control inlets 74 and 76. The diverted control liquid flows through the control tubes the control outlets 78 and 80 and into the interaction chamber 58 when the electric heater 98 on the first control tube 98 is energized to heat vaporize the control liquid through the tube, the transverse pressure differential across the main liquid stream through the interaction chamber is such that the main stream is caused to attach itself to the side wall 60 and it will flow out through the first outlet passage 70. While on the other hand, when the first heater is deenergized and the electric heater 100 of the second control tube 96 is energized the control liquid through the tube is vaporized to create a sufficient transverse pressure differential across the main stream of liquid which tends to cause it to detach from the side wall 60 into attachment to the side wall 62. The main stream of liquid is thus switched from the side wall 60 to side wall 62 so that it will flow out the second outlet passage 72. When it is desired to switch the main stream of liquid back to the first outlet passage, the second heater 100 may be deenergized and the first heater 98 is again energized. Under no control signal condition i.e. under such condition where both of the heaters 98 and 100 are deenergized, the main stream of liquid through the fluidic device may flow out through both of the outlet passages 70 and 72 at substantially the same rate. Of course, it is also possible to operate the fluidic device in such manner as to permit the main liquid stream to flow out through both of the outlet passages only when two heaters are simultaneously energized.

The control tubes may preferably be formed to receive control liquid in an amount less than 2 percent of the source liquid provided to the inlet passage. A smaller amount of the control liquid makes it easier to vaporize by a heater of smaller heating capacity. As an example, the by-pass control tube may be 0.2 mm in diameter and 150 mm in length if it has no contriction orifice. The power jet nozzle may be formed to have a diameter and length of 0.5mm and 1.0mm, respectively.

In FIG. 8, there is schematically illustrated a multi-evaporator type refrigerant, circuit for a combination refrigerator having the fluidic device of the present invention incorporated therein. The refrigerant circuit comprises a motor compressor 120, a condenser 122, flow restricting means in the form of a capillary tube 124 and a pair of evaporators 126 and 128. One evaporator 126 is provided for cooling a freezer compartment 126a of a combination refrigerator adapted to operate at a temperature below freezing and the other evaporator 128 is provided for cooling a fresh food compartment 128a intended to operate at an above freezing temperature. In accordance with the usual refrigerator practice, the component parts are to be connected in closed series flow relationship in order to form a closed refrigerant circuit. As shown in FIG. 8, the motor compressor 120, the condenser 122 and the flow restricting capillary tube 124 are series connected. For controlling the supply of the refrigerant to the two evaporators 126 and 128, thus the temperatures within the compartments 126a and 128a, fluid device 130 of the present invention is provided in the refrigerant circuit between the capillary tube 124 and the two evaporators. More specifically, inlet passage 131 of the device is connected to the outlet of the capillary tube 124 for receiving the flow of refrigerant from the capillary tube, while a first and second outlet passages 132 and 133 are communicated respectively with the inlets of the evaporators 126 and 128 for directing the flow of refrigerant thereinto. Outlets of the evaporators are jointly connected to the compressor 120. The refrigerant circuit is further associated with a suitable operational circuit means indicated by the reference numeral 140. The operational circuit 140 is operatively connected to motor compressor 120, first and second heating elements 134 and 135 provided on first and second control by-passes 136 and 137, and also with temperature sensing means 126b and 128b disposed within freezer and fresh food compartments 126 and 128. As hereinafter explained in more detail, the operational circuit 14 functions to control the energization of the heaters and the motor compressor in response to the temperatures within the freezer and fresh food compartments detected by temperature sensing means 126b and 128b.

With the above mentioned arrangement of the refrigerant, during operation the liquid refrigerant is circulated by the compressor 120 through the condenser 122, flow restricting capillary tube 124 to the fluidic device 130. Now, if a predetermined lower temperature is not yet attained in the freezer compartment 126a, the operational circuit 140 maintains the heater element 134 on the first control by-pass 136 in energized state to heat up the control liquid flow through the by-pass into gas. As described hereinabove, this results in a transverse pressure differential across the main stream of refrigerant as it emerges from power jet nozzle 138 into interaction chamber which tends to bias it toward the first outlet passage 132 for flow therethrough and into the first evaporator 126. A continued flow of refrigerant through the evaporator 126 cools down the freezer compartment 126a. When the temperature within the freezer compartment 126a reaches a predetermined lower level, temperature sensing means 126b gives a suitable signal to the operational circuit 140. The operational circuit in turn operates to turn off the heater element 134. The motor compressor 120 is simultaneously turned off excepting when a refrigeration is called for in the fresh food compartment. Circulation of the refrigerant to the first evaporator is then stopped until the temperature within the freezer compartment rises to a predetermined upper level, when the operational circuit 140 is caused to energize the heater 134 and the compressor 120 by a signal produced and supplied by temperature sensing means 126a. If a refrigerating operation is required for the fresh food compartment since a present lower temperature is not yet attained, the operational circuit 140 functions to keep the compressor energized and actuates the heater element 135 of the second control by-pass 137. The main stream of refrigerant is then switched back from the first outlet passage 132 to the second outlet passage 133 so that it will flow into the second evaporator 128 thereby to cool down the fresh food compartment 128. When the temperature within the fresh food compartment reaches a predetermined lower value, temperature sensing means 128a provide a requisite signal to the operational circuit 140. Upon receipt of which the circuit 140 deenergizes the second heater 135. The compressor 120 is also simultaneously turned off excepting when a refrigeration is called for in the freezer compartment. The heater 135 is kept turned off until such time as the temperature within the fresh food compartment rises to a predetermined upper value, when the heater 135 and the compressor 120 are again energized by the circuit 140.

Under such unusual condition where refrigerating operation is called for in both of the compartments, the operational circuit is so designed that it functions to give a priority supply of refrigerant to one or the other of the two evaporators upon considering all informations provided to the circuit. If, on the other hand, neither of the two compartments calls for refrigerating operation, the operational circuit 140 keeps the compressor 120 turned off resulting in a complete stoppage of the system.

In alternative way, it is also possible to design the system such that the main stream of refrigerant may be normally biased for flow through the first outlet passage into the first evaporator and it may be switched over for flow through the second outlet passage to the second evaporator whenever the refrigeration of the fresh food compartment is required.

Freon is used as a liquid refrigerant in the refrigerant circuit of FIG. 8, a one wattage heater is sufficient to vaporize the control liquid into gas although it depends on the flow rate of the liquid through the control by-pass.

While there has been illustrated and explained hereinabove fluidic devices including a pair of control by-passes each having its own heating element, it should be noted that a fluidic device having only one control by-pass with an associated heater element may be made and function to brings about the desired flow control results.

From the foregoing description, it is appreciated that in the fluidic device of the present invention the transverse pressure differential across the main stream of liquid necessary for the switching control is created through the thermal vaporization of the control liquid. The fact eliminates the need of mechanical valve means which was an essential part of the conventional fluidic devices. A complete elimination of mechanical moving part from a fluidic device assures a long, reliable and trouble free control operation and also extends an effective operational life of the device. Further, the control liquid for the switching operation of the main stream of liquid through the present fluidic device is directly diverted from the main stream itself by means of the control by-pass and, therefore, no separate source of control liquid and its associated mechanism are required resulting in a simple as well as inexpensive construction of the entire device. The fact that the control liquid is obtained from the main liquid stream enables a complete closed flow construction of the fluidic device and this in turn renders the fluidic device of the present invention suitable for use in various closed flow circuit applications such as refrigeration circuits where inflow of external and foreign fluid must be excluded. The amount of the required control liquid is so small in comparison with the main stream of liquid that the diversion of the control liquid from the main stream in no way adversely affects the main flow. In this connection, it should be noted that only a small amount of thermal energy is required to vaporize the control liquid.

While there has been shown and described a few specific embodiments of the present invention, it is to be understood that it is not limited thereto and it is intended by the appended claims to cover all such modification as fall within the scope thereof.

Claims

What we claim is:

1. A fluidic device comprising an inlet passage for supplying heat vaporizable liquid; a main nozzle connected to said inlet passage; a pair of outlet passages connecting through an interaction chamber to the outlet of said main nozzle; means for biasing the flow of liquid from said main nozzle toward a first of said outlet passages; at least one by-pass control passage extending from said inlet passage to a control port which is located near the outlet of said main nozzle and open in the wall of the interaction chamber; said by-pass control passage including a heater therein to vaporize the liquid flowing through the by-pass control passage and being so constructed that the flow resistance in said by-pass control passage is larger at the downstream portion than at the upper stream portion with respect to the location of said heater whereby vaporization of the liquid flowing through said by-pass control passage causes a decrease in the mass flow in said by-pass control passage which is inturn effective to divert the flow of liquid from said main nozzle to the first outlet passage.

2. A fluidic device as defined in claim 1, in which said downstream portion of said by-pass control passage comprises an elongated tube.

3. A fluidic device as defined in claim 1, in which the length of said downstream portion of said by-pass control passage is larger than that of said upperstream portion.

4. A fluidic device as defined in claim 1, in which the flow sectional area of said downstream portion of said by-pass control passage is smaller than that of said upperstream portion.

5. A fluid device as defined in claim 1 in which a source of heat vaporizable liquid is provided in fluid communication with said main nozzle.

6. A fluidic device as defined in claim 1 in which said downstream portion of said by-pass control passage has a constriction.

7. A fluidic device as defined in claim 6, in which said constriction is provided in the form of an orifice having a narrower diameter than the other portion.

8. A fluidic device as defined in claim 6, in which said constriction is located close to the said heater.

9. A fluidic device comprising an inlet passage for supplying heat vaporizable liquid; a main nozzle connected to said inlet passage; a pair of outlet passages connecting through an interaction chamber to the outlet of said main nozzle; means for biasing the flow of liquid from said main nozzle toward a first of said outlet passages; a pair of by-pass control passages extending from said inlet passage to the respective control ports which are located near the outlet of said main nozzle and opposedly open in the walls of the interaction chamber; at least one of said by-pass control passages including a heater therein to vaporize the liquid flowing through the by-pass control passage and being so constructed that the flow resistance in said by-pass control passage is larger at the downstream portion than at the upperstream portion with respect to the location of said heater whereby vaporization of the liquid flowing said by-pass control passage causes a decrease in the

mass flow in said by-pass control passage which is in turn effective to divert the flow of liquid from said main nozzle to the second outlet passage.

10. A fluid device as defined in claim 9 including a source of heat vaporizable liquid in fluid communication with said main nozzle.

11. A fluidic device comprising an inlet passage for supplying heat vaporizable liquid; a main nozzle connected to said inlet passage; first and second outlet passages connecting through an interaction chamber to the outlet of said main nozzle; a pair of by-pass control passages extending from said inlet passage to the respective control ports which are located near the outlet of said main nozzle and opposedly open at the walls of said first and second outlet passages, respectively, each of said by-pass control passages including a heater therein to vaporize the liquid flowing through the by-pass control passage and being so constructed that the flow resistance in said by-pass control passage is larger at the downstream portion than at the upper stream portion with respect to the location of said heater; and means for alternatively operating said heaters in said by-pass control passages whereby vaporization of the liquid flowing through said by-pass control passage causes a decrease in the mass flow in said by-pass control passage which is in turn effective to divert the flow of liquid to the selected outlet passage connected to the by-pass control passage in which said heater is operating.

12. A fluid device as defined in claim 11 including a source of heat vaporizable liquid in fluid communication with said main nozzle.