WO2011092705A2

WO2011092705A2 - Liquid circulation system and method

Info

Publication number: WO2011092705A2
Application number: PCT/IL2011/000108
Authority: WO
Inventors: Noam Danenberg
Original assignee: Winpower Inc.
Priority date: 2010-02-01
Filing date: 2011-01-31
Publication date: 2011-08-04
Also published as: WO2011092705A3; IL208881A0; WO2011092705A8

Abstract

A liquid circulation system comprises a flasher having a plurality of controllably openable and closable ports by which the flasher is intermittently in fluid communication with a low pressure reservoir (LPR), from which a controlled amount of liquid is transferable to the flasher by means of a pressure differential or a height differential between the LPR and the flasher, and with a high pressure reservoir (HPR), from which is dischargeable a fluid at a sufficiently high pressure which will propel the controlled amount of liquid from the flasher to the HPR. In a liquid circulation method, the flasher is subjected to flash evaporation, causing a controlled amount of liquid to be transferred to the flasher from the LPR. In one embodiment, the system increases the thermal efficiency of a working fluid circulation system by subjecting heat depleted working fluid to flash evaporation.

Description

LIQUID CIRCULATION SYSTEM AND METHOD

Field of the Invention

The invention is related to a liquid circulation system and method. Specifically, the invention relates to a closed circuit thermodynamic cycle with improved working fluid circulation means.

Background of the Invention

Prior art condensate circulation systems are energy intensive, requiring a pump to deliver condensate from a condenser to a vaporizer, or to any other unit that is in heat exchanger relation with the condensate.

Fig. 1 schematically shows the essential features of a basic prior art closed cycle power generating system. The working fluid in system 10 undergoes a thermodynamic cycle generally referred to as the Rankine cycle. System 10 includes a vaporizer 12, by which the liquid working fluid is converted to a one or two phase gas at a high temperature and pressure, a mechanical power producer 14, e.g. a turbine in which part of the energy of the gaseous working fluid is converted into mechanical or electrical energy, a condenser 16 by which the working fluid is condensed into the liquid phase, and a pump 18, which increases the pressure of the liquid working fluid while delivering it towards vaporizer 12.

The overall efficiency and economic feasibility of the system is the ratio of the energy output to the energy input required to move the working fluid around the circuit, i.e. the energy requirement of pump 18, plus the energy required to change the phase (and temperature and pressure) of the working fluid in the vaporizer 12. The cost of the energy requirements of vaporizer 12 can (and has in some prior art systems) be reduced by using solar energy or waste heat, e.g. from engines or industrial processes, as the source of heat. In any prior art system, however, the pump is an essential component whose energy requirements cannot be eliminated or even reduced. Since most pumps in commercial use consume electrical energy, it is of high interest to reduce or save this energy investment.

Other known closed circuit condensate circulation systems include a combined power generating and refrigeration system in which a refrigerant is delivered by means of a pump from a condenser to a power producer.

It is therefore an object of the present invention to provide a closed cycle power generating system that does not require the presence of an electrically driven pump to circulate the condensed working fluid.

It is an additional object of the present invention to provide an economically viable closed cycle power generating system.

It is an additional object of the present invention to provide a closed cycle refrigeration system that does not require the presence of a pump, or any other electrically powered device, to circulate the working fluid.

Further purposes and advantages of this invention will appear as the description proceeds.

Summary of the Invention

The present invention is related to a liquid circulation method, comprising the sequential steps of providing a liquid having a first pressure at a low pressure reservoir; subjecting a flasher, while its interior is at a second pressure greater than said first pressure, to flash evaporation, whereby the pressure within said flasher interior decreases to a third pressure which is less than or equal to said first pressure; opening a first conduit extending between said low pressure reservoir and said flasher, thereby causing a controlled amount of said liquid to be transferred to said flasher by means of a pressure differential or a height differential between said low pressure reservoir and said flasher; occluding said first conduit; opening a second conduit extending from a high pressure reservoir at a fourth pressure greater than said second pressure to said flasher and a third conduit extending from said flasher to said high pressure reservoir, thereby causing fluid from said high pressure reservoir to propel said transferred liquid to said high pressure reservoir via said third conduit until said flasher interior achieves said second pressure; and occluding said second and third conduits.

In one aspect, the flasher is subjected to flash evaporation by opening a sub- circuit conduit extending between the flasher and a low pressure source having a pressure less than the first pressure.

In one aspect, the flasher is subjected to flash evaporation by causing the flasher to be in fluid communication with the low pressure reservoir.

In one aspect, the high pressure reservoir is a gas generator, the low pressure reservoir is a condenser, and the fluid which is not diverted via the second conduit to the flasher circulates from said gas generator to said condenser via a main circuit.

In one embodiment, the fluid flowing in the main circuit is sufficiently pressurized to generate power when expanded within a power-producing unit such as a turbine.

In one embodiment, the fluid flowing in the main circuit is sufficiently pressurized to cool a volume when delivered to an ejector of a refrigeration loop. The invention is therefore directed to a liquid circulation system, comprising a flasher having a plurality of controllably openable and closable ports by which said flasher is intermittently in fluid communication with a low pressure reservoir (LPR), from which a controlled amount of liquid is transferable to said flasher by means of a pressure differential or a height differential between said LPR and said flasher; and a high pressure reservoir (HPR), from which is dischargeable a fluid at a sufficiently high pressure which will propel said controlled amount of liquid from said flasher to said HPR.

In one aspect, the flasher is also intermittently in fluid communication with one or more low pressure sources having a pressure less than the pressure of the LPR, for initiating flash evaporation of liquid contained within the flasher.

In one aspect, the liquid contained within the flasher is subjected to flash evaporation when the flasher is caused to be in fluid communication with the LPR, the pressure of evaporate immediately decreasing to a level equal to or below that of the liquid contained within the LPR.

In one aspect, the HPR is a gas generator and the LPR is a condenser.

In one aspect, the liquid circulation system further comprises a closed, main conduit circuit through which the fluid for propelling the controlled amount of liquid sequentially circulates from the gas generator to the condenser, from the condenser to the flasher, and from the flasher to the gas generator.

In one aspect, the liquid circulation system further comprises a sub-circuit comprising a first conduit through which the fluid is divertable from said main-circuit and downstream to the gas generator to the flasher. The sub-circuit operates in a pulsate manner to maintain the continuous flow of the fluid throughout the main circuit. Condensed fluid is transferred in a first pulse from the condenser to the flasher. Gaseous fluid is discharged from the gas generator to the flasher in a second pulse in order to propel the transferred liquid to the gas generator, thereby raising the pressure of the liquid from its low value in the condenser to a high pressure level required in the main circuit.

In one aspect, the sub-circuit further comprises a second conduit extending from the flasher to a low pressure source having a pressure less than the pressure of the liquid contained within the flasher, for initiating a flash evaporation process.

In one aspect, the sub-circuit further comprises a controller and a plurality of control valves in electrical communication with said controller for opening the first conduit while the second conduit is occluded in order to propel the controlled amount of liquid from the flasher to the gas generator, for closing the first conduit and opening the second conduit in order to initiate a flash evaporation process with respect to liquid remaining within the flasher, and for closing the first and second conduits while the flasher is in liquid communication with the condenser so that the controlled amount of liquid will be transferred to the flasher.

In one aspect, the sub-circuit operates in the following manner:

a. an upper level sensor in the flasher transmits a first signal to the controller when the liquid level approaches the full capacity of the flasher;

b. the controller transmits a second signal to close a control valve in a conduit of the main circuit between the condenser and the flasher and transmits a third signal to open a control valve for enabling flow to the flasher of fluid for propelling the controlled amount of liquid from the flasher to the gas generator;

c. a lower level sensor in the flasher transmits a third signal to the controller when the liquid working fluid level approaches the bottom of the flasher;

d. the controller transmits a fourth signal to open the control valve between the condenser and the flasher while simultaneously transmitting a fifth signal for disabling flow to the flasher of fluid for propelling the controlled amount of liquid from the flasher to the gas generator;

e. the controller transmits a sixth signal to open the control valve between the flasher and the low pressure source, whereupon a flash evaporation occurs and the remaining fluid evaporates while decreasing in temperature and pressure, thereby preparing the flasher to start receiving liquid from the condenser; and

f. steps a through e are repeated in a cyclic fashion.

In one aspect, the liquid circulation system is a power generating system, wherein the main circuit further comprises a turbine for producing power from gaseous fluid exiting the gas generator.

In one aspect, the liquid circulation system is a refrigeration system, wherein the main circuit further comprises an ejector which also receives fluid exiting a refrigeration loop.

In one aspect, the liquid circulation system is a combined power generating and refrigeration system, wherein a closed refrigeration loop is in communication with an expansion valve for sufficiently reducing the pressure of the fluid exiting the condenser so as to cool a desired volume when said reduced pressure fluid is evaporated. In one aspect, the fluid exiting the refrigeration loop combines with the fluid in the main circuit flowing towards the turbine.

The liquid circulation system according to claim 11, wherein fluid discharged from the refrigeration loop is delivered to the turbine.

In one aspect, a conduit of the main circuit extends from the gas generator directly to the turbine.

In one aspect, an additional conduit branches from the conduit extending from the gas generator directly to the turbine, said additional conduit extending to an ejector which also receives fluid exiting the refrigeration loop.

In one aspect, all fluid discharged from the turbine is delivered to an ejector which also receives working fluid exiting a refrigeration loop.

In one aspect, the liquid circulation system further comprises a first gas generator for delivering fluid to the turbine and a second gas generator for delivering fluid to an ejector which also receives fluid exiting the refrigeration loop.

In one aspect, the gas generator comprises a vaporizer, a superheater, or a vaporizer and a superheater.

In one aspect, the liquid circulation further comprises a sub-circuit which comprises a compressing unit which is connected to the gas generator by means of one-way valve that permits the fluid to flow only from the gas generator to said compressing unit, and a conduit extending from said compressing unit to the flasher, wherein said sub-circuit operates in a pulsate manner to maintain continuous flow of the fluid within the main circuit by raising the pressure of the liquid in the flasher to a sufficiently high level which is required in the main circuit.

In one aspect, a heat source associated with the gas generator is solar energy.

In one aspect, a heat source associated with the gas generator is waste heat.

In one aspect, the liquid circulation system further comprises a controller which is adapted to command to propel the controlled amount of liquid from the flasher to the gas generator when a liquid level in the flasher approaches a full capacity and to command to open a control valve operative connected with a conduit extending between the condenser and flasher when a liquid level in the flasher approaches a predetermined low capacity.

In one aspect, the fluid exiting the refrigeration loop combines with the main circuit downstream from the condenser.

In one aspect, the one or more low pressure sources comprises an evaporator of a refrigeration loop.

In one aspect, the one or more low pressure sources is an external low pressure source, for example generated by means of a vacuum pump.

In one aspect, the expansion valve is operatively connected to the main circuit and the flasher is an evaporative liquid accumulator which is in heat exchanger relation with a duct through which warm air from a volume to be cooled circulates.

In one aspect, the condenser is of a direct transfer type. In one aspect, the liquid circulation system is a power generating system, wherein the HPR is a gas generator and the LPR is a condenser and a main circuit comprises a turbine for producing power from gaseous fluid exiting the gas generator, wherein the one or more low pressure sources is also used to subject heat depleted working fluid to flash evaporation and to thereby reduce the pressure and temperature of said heat depleted working fluid.

In one aspect, the LPR is a condenser.

In one aspect, the heat depleted working fluid is condensate contained within the condenser.

In one aspect, the heat depleted working fluid is turbine discharge, said heat depleted working fluid being contained within a pulse absorber connected to a discharge end of the turbine.

In one aspect, the volume of the pulse absorber is significantly greater than the instantaneous volume of the turbine discharge that is received within the pulse absorber.

In one aspect, the turbine discharge has a quality of no more than 5%.

In one aspect, the liquid circulation system is a power generating system, wherein the HPR is a gas generator and the LPR is a condenser, further comprising a main circuit which comprises a turbine for producing power from gaseous fluid exiting said gas generator and an ejector for compressing fluid discharged from said turbine, wherein an ejector suction conduit extends from said condenser to said ejector, thereby reducing the pressure and temperature of condensate. In one embodiment, the system is a closed circuit, combined power generating and refrigeration system, comprising:

a) a closed main circuit through which a working fluid flows from a condenser to a turbine after having being successively heated by a vaporizer and superheater;

b) a closed refrigeration loop in communication with an expansion valve for sufficiently reducing the pressure of the working fluid exiting the condenser so as to cool a desired volume when said reduced pressure working fluid is evaporated; and

c) a liquid accumulator positioned in said main circuit between the condenser and the vaporizer and having a plurality of controllably openable and closable ports by which said accumulator is intermittently in fluid communication with- i. the condenser, from which is transferable a controlled amount of condensed working fluid to said accumulator by means of a pressure differential between the condenser and said accumulator; and

ii. the superheater, from which is divertable a gas via a sub-circuit at a sufficiently high pressure which will propel said controlled amount of condensed working fluid from said accumulator to the vaporizer, the vaporizer delivering a continuous supply of vaporized working fluid and the turbine discharging heat depleted working fluid to the condenser.

In one aspect, the working fluid exiting the refrigeration loop combines with superheated working fluid in the main circuit flowing towards the turbine.

In one aspect, the working fluid exiting the refrigeration loop combines with the main circuit downstream from the condenser. The present invention is also directed to a closed circuit refrigeration system, comprising:

a) a closed main circuit through which a working fluid flows from a condenser to a vaporizer;

ii. a gas pressurizing unit, from which is divertable a gas via a sub- circuit at a sufficiently high pressure which will propel said controlled amount of condensed working fluid from said accumulator to the vaporizer.

The present invention is also directed to a system for increasing the thermal efficiency of a working fluid circulation system, comprising means for subjecting heat depleted working fluid to flash evaporation.

In one aspect, the means for subjecting heat depleted working fluid to flash evaporation comprises a low pressure source, a conduit extending from a pressure vessel containing said heat depleted working fluid at a pressure above the pressure of said low pressure source to said low pressure source, a control valve operatively connected to said conduit, and an actuator associated with said control valve for opening said control valve for a predetermined duration and for thereby exposing said heat depleted working fluid to said low pressure source so as to initiate a flash evaporation process and to reduce the pressure and temperature of said heat depleted working fluid.

In one aspect, the pressure vessel containing said heat depleted working fluid is a condenser.

In one aspect, the pressure vessel containing said heat depleted working fluid is a pulse absorber connected to a discharge end of a turbine.

In one aspect, the turbine discharge has a quality of no more than 5%.

In one aspect, the low pressure source is an evaporator of a refrigeration loop.

In one aspect, the low pressure source is an external low pressure source, such as a condenser or one generated by means of a vacuum pump. The condenser may be of a direct transfer type.

In one aspect, the low pressure source is a flasher intermittently in fluid communication with an evaporator of a refrigeration loop and with a gas generator.

In one aspect, the working fluid circulation system is selected from the group consisting of a power plant, a refrigeration cycle, and a coupled power-refrigeration system. All the above and other characteristics and advantages of the invention will be further understood through the following illustrative and non-limitative description of embodiments thereof, with reference to the appended drawings. In the drawings the same numerals are sometimes used to indicate the same elements in different drawings.

Brief Description of the Drawings

In the drawings:

Fig. 1 is a schematic illustration of a prior art closed circuit power generating system;

Fig. 2 is a schematic illustration of a closed circuit, pumpless power generating system which comprises a compressing unit, according to one embodiment of the present invention;

Fig. 3 is a schematic illustration of a power generating system which comprises, in addition to the components of Fig. 2, a superheater;

Fig. 4 is a schematic illustration of a power generating system wherein generated gas is diverted in order to propel accumulated liquid;

Fig. 5 is a schematic illustration of a power generating system wherein flash evaporate is placed in fluid communication with turbine discharge; Fig. 6 is a schematic illustration of a combined power generating and refrigeration system, according to one embodiment of the present invention;

Fig. 7 is a schematic illustration of a refrigeration system, according to one embodiment of the present invention;

Fig. 8 is a schematic illustration of a combined power generating and refrigeration system, wherein flash evaporate is in fluid communication with a refrigeration loop;

Fig. 9 is a schematic illustration of a combined power generating and refrigeration system, wherein flash evaporate is in fluid communication with an evaporator discharge; Fig. 10 is a schematic illustration of a combined power generating and refrigeration system, wherein the flasher is an evaporative liquid accumulator;

Fig. 11 is a schematic illustration of a combined power generating and refrigeration system, wherein the turbine is positioned upstream to the ejector;

Fig. 12 is a schematic illustration of a combined power generating and refrigeration system, wherein the discharge of the gas generator is split into parallel flows;

Fig. 13 is a schematic illustration of a combined power generating and refrigeration system, wherein condensate is subjected to flash evaporation;

Fig. 14 is a schematic illustration of a refrigeration system, wherein condensate is subjected to flash evaporation;

Fig. 15 is a schematic illustration of a combined power generating and refrigeration system, wherein the discharge of the gas generator is split into parallel flows and condensate is subjected to flash evaporation;

Fig. 16 is a schematic illustration of a system similar to that of Fig. 15, wherein the condenser is a direct transfer type;

Fig. 17 is a schematic illustration of a combined power generating and refrigeration system, wherein turbine discharge is subjected to flash evaporation;

Fig. 18 is a schematic illustration of a combined power generating and refrigeration system, wherein the discharge of the gas generator is split into parallel flows and the turbine discharge is subjected to flash evaporation;

Fig. 19 is a schematic illustration of a combined power generating and refrigeration system, wherein both turbine discharge and condensate are subjected to flash evaporation; Fig. 20 is a schematic illustration of a combined power generating and refrigeration system, wherein both the turbine discharge and the condensate are subjected to flash evaporation by means of the flasher; Fig. 21 is a schematic illustration of a combined power generating and refrigeration system similar to that of Fig. 19, wherein the pulse absorber is in intermittent fluid communication with the condenser;

Fig. 22 is a schematic illustration of a power generating system wherein flash evaporation processes are initiated by means of a low pressure source;

Fig. 23 is a schematic illustration of a combined power generating and refrigeration system similar to that of Fig. 19, wherein the condensate is circulated by means of a pump;

Fig. 24 is a schematic illustration of a combined power generating and refrigeration system which employs two gas generators;

Fig. 25 is a schematic illustration of a power generating system wherein a condenser discharge conduit extends to an ejector; and

Figs. 26 and 27 are schematic illustrations of two apparatus layouts, respectively, for demonstrate operability of the pressure differential based liquid transfer of the present invention.

Detailed Description of Embodiments of the Invention

The present invention is a novel power generating system by which condensate is delivered to a vaporizer, or any other gas generator, without use of a pump. Condensate is delivered by means of a pressure differential or a height differential to an intermediate holding tank (interchangeable with the terms "liquid accumulator" and "flasher") after the latter has been subjected to flash evaporation, and the transferred liquid is propelled to the vaporizer by means of a pressurized gas that is cyclically introduced to the holding tank. Although the power generating systems that are described herein refer to a Rankine type thermodynamic cycle, namely one in which condensate is transferred to a vaporizer, delivered therefrom to a power producer such as a turbine, and discharged from the power producer to a condenser, it will be appreciated that the condensate circulation means of the present invention may be suitably implemented with other thermodynamic cycles as well, such as one with a reheater, regenerator, or recuperator.

Fig. 2 schematically shows the essential features of a closed cycle power generating system, according to one embodiment of the invention. System 20 comprises a main flow circuit 25 of the working fluid for producing power and a sub-circuit 35 for elevation of the low pressure working fluid recovered from the condenser to the high pressure level required in the main circuit.

The main circuit 25 includes vaporizer 22, a condenser 30, a liquid holding tank 32, and a power-producing unit 26, e.g. a turbine which may be coupled to an electricity generator, located between the vapor generator 22 and the condenser 30. The working fluid circulates in the main circuit via conduits 29a-d. The working fluid is generally in a liquid phase while flowing in conduit 29a between condenser 30 and holding tank 32 and in conduit 29b between holding tank 32 and vaporizer 22, as represented by a solid line, and is in a vapor phase while flowing in conduit 29c between vaporizer 22 and power-producing unit 26 and in conduit 29d between power-producing unit 26 and condenser 30, as represented by a dashed line.

The vaporizer 22 continuously produces the required vapor flow to drive the power-producing unit 26, which produces the power output, symbolically represented by arrow 28, of system 20. The flow rate of the working fluid is controlled by the heat flux 24 supplied to the vapor generator 22. Vaporizer 22, is a closed pressure vessel, which is continuously supplied with liquid working fluid from fluid holding tank 32 by means of the sub-circuit, as will be described hereinbelow.

At the outlet of the power-producing unit 26 the vapor pressure of the working fluid is significantly reduced after having been expanded thereby, followed by condensation of the vapor to the liquid state in the condenser 30 and accumulation of the liquid in holding tank 32.

The pressure of the liquid in condenser 30 is the lowest steady state pressure in main circuit 25 and some means must be provided to move the liquid from condenser 30 to vaporizer 22. In the prior art system shown in Fig. 1, pump 18 fulfills this function. According to the present invention, a sub-circuit 35 is provided for recycling the low pressure working fluid in condenser 30 to the high pressure level of the vaporizer 22, without the use of an electric or petrol driven motor such as in a pump or compressor.

Sub-circuit 35 comprises a compressing unit 40 which receives vapor from vaporizer 22 via one-way valve 36, a conduit 33 extending from compressing unit 40 to holding tank 32, and a conduit 37 extending from holding tank 32 to conduit 29a.

The main flow circuit 25 operates continuously and thus maintains the vapor flow to the power-producing unit in a constant manner; however the sub-circuit operates in a pulsate manner. The vapor pressure in the compressing unit 40, which also is a closed pressure vessel, is to be maintained at somewhat higher level then the pressure in the vaporizer 22. When the liquid in the holding tank 32 approaches its full capacity, an upper level sensor sends a signal to a control unit 48, which in turn activates an electric solenoid valve 44 operative ly connected to conduit 36. Control unit 48 simultaneously opens valve 44 and closes electric solenoid valve 46 operatively connected to conduit 37. Liquid working fluid from the liquid holding tank 32 is therefore forced into the vaporizer 22 by the high pressured vapor discharged from compressing unit 40.

During each cycle of the sub-circuit 35, the vaporizer 22 is refilled with liquid while the pressure in compressing unit 40 decreases. The refilling process of vapor generator 22 is terminated when the pressure in compressing unit 40 becomes equal to that in vaporizer 22. At this point a lower level sensor sends a signal to control unit 48, which in turn closes valve 44 while simultaneously opening valve 46. When valve 44 closes, some of the working fluid moves from vaporizer 22 to compressing unit 40 until the pressure in the two units becomes equal. The liquid working fluid in compressing unit 40 is vaporized by heat flux 42 from the same or a different heat source as that which produces heat flux 24, thereby replenishing the high pressure vapor in compressing unit 40.

The heat fluxes 24 and 42 can be supplied from any source of heat but preferably is either heat from a solar collection system or waste heat from an available source, e.g. from, motors, vehicle engines, conventional electricity producing plants, or industrial processes, the only requirement being that the heat source/s is capable of continuously supplying heat fluxes 24 and 42 that are large enough to vaporize the working fluid inside vapor generator 20 and compressing unit 40, during the operating time of system 20. Clearly in parallel the vapor pressure P and temperature T of the vapor produced are determined and controlled accordingly, depending on the thermodynamic properties of the working fluid.

At the end of the sub-cycle step of propelling the working fluid from the liquid holding tank 32 into the vaporizer 22 by the high pressure in compressing unit 40, the remaining liquid in the holding tank is at a pressure which is higher than that in the condenser unit. When valve 46 is then opened and valve 44 is closed, the liquid working fluid remaining in holding tank 32 is exposed to the low pressure level at the exit of condenser 30, which is below the vapor pressure of the liquid remaining in holding tank 32. A flash evaporation occurs and the small amount of the remaining working fluid in the liquid holding tank evaporates. Although the evaporate achieves a temporal peak pressure significantly greater than the pressure of condenser 30, the temperature and pressure of the evaporate immediately decreases as a result of the latent heat of evaporation, reaching a pressure level below that of the condensate. Valve 38 operatively connected to conduit 29a downstream from the junction 31 of conduits 29a and 37 is then opened. Since the pressure within the interior of holding tank 32, after being subjected to flash evaporation, is reduced to a value below that of condenser 30, condensate is forced to flow to holding tank 32 by means of the pressure differential between condenser 30 and holding tank 32. Valves 38 and 46 are closed after the liquid level within holding tank reaches a predetermined level. In this fashion, condensate may be advantageously delivered to vaporizer 22 without use of a pump.

Alternatively, the pressure of the interior of holding tank 32 may be reduced to a pressure substantially equal to, or even slightly greater than, the pressure of the condensate; yet due a height differential between condenser 30 and holding tank 32, condensate is forced to flow to holding tank 32 when valve 38 is open.

One way valve 34 allows liquid working fluid to flow from holding tank 32 towards vapor generator 22 while preventing backflow from vaporizer 22. One way valve 36 allows working fluid to flow from vapor generator 22 towards compressing unit 40 and not in the opposite direction. It will be appreciated that one-way valves 34 and 36 may be replaced by solenoid valves. As said, Fig. 2 shows only the essential components of system 20. In other embodiments, the system may comprise additional valves, numerous sensors to measure pressure, temperature, and other system parameters at different locations in the circuits. The output from the sensors is sent to control unit 48 that synchronizes the opening and closing of the valves and controls the heat fluxes 24 and 42 in order to maintain the flow of working fluid within the circuits to provide maximum power output. The choice of working fluid and the exact design details of vaporizer 22, condenser 30, liquid holding tank 32, compressing unit 40, the conduits that connect the components to form the closed circuits, and the other components of system 20 can easily be determined by skilled persons depending on factors such as the type and output of the power-producing unit and the characteristics of the available sources of heat. As an example of the invention, for a system such as shown in Fig. 2 using the sun as the source of heat fluxes 24 and 42 a good choice of working fluid would be R134. In this system, achievable values of temperature and pressure would be 81°C and 27 bar in the vaporizer 22 and 87°C and 30 bar in the high pressure compressing unit 40.

Fig. 3 illustrates a power generating system 50 similar to system 20 illustrated in Fig. 2, with the addition of a superheater 55 to main circuit 57 for heating the vaporized working fluid produced by vaporizer 22 to a level above saturation temperature, to avoid erosion of the turbine blades and to maximize the turbine power output. Superheater 55 is in fluid communication with conduit 29c, being interposed between vaporizer 22 and turbine 56. The medium that applies heat flux Qs to superheater 55 may be identical to that which applies heat flux Qv to vaporizer 22 or which applies heat flux Qp to vapor compressor 40, or may be a different medium, e.g. the gaseous products of combustion resulting from the burning of wood or methane. The temperature to which the working fluid is superheated is dependent upon the magnitude of the heat influx, the type of working fluid employed, and the turbine requirements. A control valve 51 is operatively connected to conduit 29b and a control valve 52 is operatively connected to conduit 59 extending between vaporizer 22 and vapor compressor 40. Valves 51 and 52 are independently closed by control unit 48 following the cyclic flow of working fluid therethrough, to prevent backflow.

In the embodiment of Fig. 4 is illustrated a power generating system 60 having a main circuit 58 and a sub-circuit 65 interfacing therewith that do not require a compressing unit to propel the liquid from liquid accumulator 32 to vaporizer 22. As shown, superheater 55 interposed between vaporizer 22 and turbine 56 serves to propel the accumulated liquid within accumulator 32 to vaporizer 22. Sub-circuit 65 comprises, in addition to conduit 37 extending from liquid accumulator 32 to junction 31 at conduit 29a, conduit 66 extending from junction 68 at conduit 29c and downstream from superheater 55 to liquid accumulator 32.

A control valve 63 is operatively connected to conduit 66 and will allow, when opened, superheated working fluid to be delivered to liquid accumulator 32. The superheated working fluid is at a sufficiently high pressure that will propel the incompressible liquid contained within accumulator 32 via conduit 29b and through control valve 51 to vaporizer 22. Even though liquid is cyclically delivered from accumulator 32 to vaporizer 22, vaporizer 22 and superheater 55 generate working fluid that flows at a sufficiently high pressure and flow rate to produce a continuous amount of work by means of turbine 56. The supply of superheated working fluid to turbine 56 will not be substantially reduced even though a portion thereof is diverted to accumulator 32 via conduit 66 since the diameter of the sub-circuit conduits is substantially less than the main circuit conduits. Alternatively, control valve 69 operatively connected to conduit 29c between junction 68 and turbine 56 may be regulated to compensate for the reduction in mass flow rate of the superheated working fluid to turbine 56, as well as to cut off flow to turbine 56 if its backpressure is excessively low. The flow of working fluid through sub-circuit 65 is controlled by control unit 48 in a similar fashion as with respect to sub-circuit 35 of Fig. 2, and therefore need not be repeated for sake of brevity. The flow of superheated working fluid may be terminated when control unit 48 receives a signal from a sensor, e.g. a limit switch, indicating that the liquid level within accumulator 32 has a reached a predetermined low level.

Power generating system 70 illustrated in Fig. 5 is identical to system 60 of Fig. 4, with the exception that sub-circuit 75 comprises a conduit 72 to which control valve 46 is operatively connected and which extends from liquid accumulator 32 to junction 74 at conduit 29d.. Thus the flash evaporate will be in fluid communication with the gaseous discharge exiting turbine 56 via conduit 29d.

The gas propelled condensate delivery method of the present invention may be implemented in many different power generating systems to avoid the capital and operating costs of a condensate pump.

Fig. 6 illustrates a power generating system 80 which comprises an ejector refrigeration cycle loop 85 in addition to main circuit 88 and sub-circuit 75.

In a conventional closed vapor-compression refrigeration cycle, relatively high pressure liquid refrigerant recirculates from a condenser to a throttling expansion valve by which its pressure and temperature are reduced, and then flows to an evaporator in which the reduced-pressure liquid refrigerant evaporates as a result of heat transfer from the cooled space. An energy intensive compressor raises the refrigerant vapor to a higher pressure and temperature so that it will liquefy while transferring heat to the surroundings or to a cooling medium at the condenser. In refrigeration cycle loop 85 of the present invention, an ejector 87 is used in lieu of an energy intensive compressor. Ejector 87 is placed in fluid communication with both conduit 29c of main circuit 88 through which superheated working fluid flows and with conduit 96 of refrigeration loop 85. A conduit 29e of the main circuit extends from ejector 87 to turbine 56.

At junction 91 between conduit 29a of main circuit 88 and conduit 94 of refrigeration loop 85, a portion of the condensate is diverted to the refrigeration loop. The pressure and temperature of the liquid working fluid are reduced by expansion valve 83 so that its temperature will be below ambient temperature. The pressure differential between condenser 30 and the exit of expansion valve 83 provides the driving force which causes the condensate to circulate within refrigeration loop 85. The reduced-pressure liquid or mixed phase working fluid flows through conduit 95 from expansion valve 83 to evaporator 86. The working fluid achieves a vapor phase at evaporator 86 to produce a cooling effect with respect to a desired volume, from which heat QE is transferred in order to evaporate the working fluid. The working fluid vapor flowing through conduit 96 is drawn into ejector 87 even though it is at a lower pressure than the superheated working fluid. It will be appreciated that the ejector may be replaced by a Venturi tube.

The superheated working fluid flowing in conduit 29c and the working fluid vapor flowing in conduit 96 are mixed in the diffuser section of ejector 87, causing the mixed stream to become pressurized. The ejector discharge flows through conduit 29e to turbine 56, whereat it is expanded to produce power. The working fluid is then condensed at condenser 30 to complete the refrigeration cycle.

Thus system 80 can advantageously perform two functions simultaneously with the same working fluid. That is, main circuit 88 is used to generate power by means of turbine 56 at the same time that refrigeration loop 85 is being used to cool a desired volume. A significant reduction in power consumption with respect to prior art power generating systems is realized as a condensate pump is rendered unnecessary and with respect to prior art refrigeration cycles is realized as a compressor is not needed.

Fig. 7 illustrates a refrigeration system 90 that comprises a refrigeration loop 85 of Fig. 6 which does not interface with a power cycle. Working fluid circulates through main circuit 98 from condenser 30 to accumulator 32 and from accumulator 32 to vaporizer 22 by means of sub-circuit 75, and passes consecutively through vaporizer 22, superheater 55, and ejector 87. The ejector discharge, after the superheated working fluid flowing in conduit 29c and the working fluid vapor flowing in conduit 96 have been mixed together, flows via conduit 29f to condenser 30. Refrigeration system 90 is economically viable since the working fluid flowing in main circuit 98 is heated and pressurized, in order to provide a means for compressing the working fluid for use in refrigeration loop 85, in vaporizer 22 and superheater 55 by waste heat or by a renewable energy source. It will be appreciated that refrigeration loop 85 will also provide a good cooling effect even if main circuit 98 is not provided with a superheater. Likewise, any of the combined power generating and refrigeration systems described hereinafter may be implemented as a refrigeration system only.

Fig. 8 illustrates a power generating system 100 which comprises ejector refrigeration cycle loop 85, in addition to main circuit 88 and a sub -circuit 105.

In this embodiment, accumulator 32 is capable of being in fluid communication with the exit of expansion valve 83, in order to induce a more intensive flash evaporation process since the exit of expansion valve 83 is at a lower pressure than the exit of condenser 30. In order to achieve the more intensive flash evaporation process, sub-circuit 105 is provided with a conduit 102 that extends from control valve 106 to conduit 95 of refrigeration loop 85.

Control valve 106 may be a three-way valve, regulating the flow of working fluid through each of three conduits 72, 101, and 102 with which it is in fluid communication. Conduit 101 extends from accumulator 32 to valve 106. Thus control valve 106 is operable, in conjunction with control unit 48, to occlude conduit 101 while control valve 63 is opened so that the accumulated liquid will be propelled by diverted superheated working fluid to vaporizer 22 when control valves 51 and 63 are opened. At the conclusion of the gas propelled step, control valves 51 and 63 are closed and control valve 106 is operable to occlude conduit 103 while conduits 101 and 102 remain unobstructed, in order to initiate the flash evaporation step. When the interior of accumulator 32 is sufficiently flash evaporated, e.g. after a first predetermined period of time, conduit 102 is occluded and conduit 72 is opened so that the evaporated working fluid will be released, being urged to flow towards conduit 29d. When the accumulator interior is at a lower pressure that that of condenser 30, e.g. after a second predetermined period of time, control valve 106 is operable to also occlude conduits 72 and 101. Control valve 38 is then opened, causing relatively high pressure condensate to flow from condenser 30 to the liquid region of accumulator 32. Upon conclusion of the condensate transfer step, control valve 38 is closed.

Alternatively, control valve 106 may be a two-way valve or a conventional open/close valve, thereby obviating the need for conduit 72. Control valve 106 is closed during the gas propelled step and is opened during the flash evaporation step. Fig. 9 illustrates a power generating system 120 which comprises main circuit 88, refrigeration cycle loop 85, and a sub-circuit 130 that interfaces with the refrigeration loop.

In this embodiment, sub-circuit 130 comprises a conduit 133 extending from control valve 106 to junction 136 at conduit 96 of the refrigeration loop, which extends from the exit of evaporator 86 to ejector 87. Thus when control valve 106 is opened, the relatively high pressurized liquid contained within accumulator 32 is exposed to the relatively low pressure at the exit of evaporator 86, to cause intensive flash evaporation. The flash evaporated working fluid will then be urged to flow towards conduit 96 as a result of the pressure differential between the accumulator interior and the working fluid exiting evaporator 86. The mixed pressurized stream flowing in conduit 96 will combine at ejector 87 with the superheated working fluid flowing in conduit 29c, and will then be delivered to turbine 56 in order to produce power.

While prior art closed circuit refrigeration cycles require a compression step to ensure that the working fluid will be sufficiently condensed to provide a cooling effect during a subsequent cycle of refrigerant flow, refrigeration loop 85 of the present invention advantageously provides a good cooling effect by means of expansion valve 83 and evaporator 86 without requiring a compression step. The reason that refrigeration loop 85 does not require a compression step is that the mixed pressurized stream flowing downstream from junction 136 combines with the superheated working fluid and receives condensed working fluid at junction 91. The refrigeration cycle benefits from the condensate that is produced in any case during the power cycle of main circuit 88, and therefore is not required to raise the pressure of the working fluid before being introduced to condenser 30. Fig. 10 illustrates a power generating system 140 which comprises a combined sub-circuit and refrigeration loop 145 and a main circuit 148 for additional reduction in capital costs.

Main circuit 148 is similar to main circuit 58 of Fig. 4; however, expansion valve 141 for reducing the pressure of condensed working fluid being delivered to refrigeration loop 145 is operatively connected to conduit 29a of the main circuit. The holding tank is an evaporative liquid accumulator 150 and is in heat exchanger relation with duct 153 through which warm air from the volume to be cooled circulates. The expanded condensate received in accumulator 150 becomes evaporated by the warm air, while the latter becomes cooled as a result of the latent heat of evaporation. The evaporated working fluid is then released to conduit 29d via conduit 72 after control valve 46 is opened.

In this embodiment, liquid accumulator 150 serves the two functions of contributing to the transfer of working fluid from condenser 30 to vaporizer 22 and participatin in the refrigeration cycle. Control unit 48 synchronizes the actuation of the various control valves to ensure that each pulse of condensate received by accumulator 150 will alternately be used for the refrigeration cycle and then for the gas propelled condensate delivery cycle.

While a pulse of condensate is being received in accumulator 150 and the liquid level therein is greater than a first predetermined value, valve 63 is opened to introduce superheated working fluid for propelling the accumulated condensate to vaporizer 22 before the warm air circulating in duct 153 evaporates the condensate. Valves 38 and 46 are closed following a predetermined time after being initially opened or after a predetermined amount of condensate has been delivered from condensate 30 to accumulator 150. Alternatively, a control valve 157 may be operatively connected to duct 153 to prevent the passage of warm air during the gas propelled condensate delivery cycle. When the liquid level within accumulator 150 becomes less than a second predetermined value, valve 63 is closed to terminate the flow of superheated working fluid to the accumulator. Valve 46 is then opened to expose the accumulator interior to the reduced pressure downstream to expansion valve 141, causing the remaining liquid in accumulator 150 to be flash evaporated. The flash evaporated working fluid is released to conduit 29d during a predetermined period of time and then valve 46 is once again closed.

Since the pressure within the accumulator interior is below that of condenser 30 as a result of the flash evaporation, the subsequent opening of valve 38 causes condensate to be transferred to accumulator 150 due to the pressure differential between the condenser interior and the accumulator interior. The pulse of transferred condensate, after valve 38 is closed, becomes evaporated by the warm air introduced via duct 153. Valve 46 of the sub-circuit is then opened, causing the evaporated fluid to flash and then to be released to conduit 29d. When valve 46 is closed again, accumulator 150 is ready to participate in a gas propelled condensate delivery cycle. If so desired, valve 46 may remain open throughout the refrigeration cycle and following the transfer of condensate to accumulator 150 in order to induce a constant flow of working fluid from the accumulator to conduit 29d and to thereby improve the cooling effect.

In the embodiment of power generating system 210 shown in Fig. 11 which comprises main circuit 215, refrigeration cycle loop 85, and sub-circuit 75, turbine 56 is positioned upstream to ejector 87, to maximize the amount of power that can be produced from the gaseous working fluid, whether saturated vapor or superheated gas, flowing via conduit E from gas generator 22. The heat depleted working fluid discharged from turbine 56 and flowing through conduit F is mixed together with the working fluid vapor flowing in conduit J in the diffuser section of ejector 87, causing the mixed stream to become pressurized. The ejector discharge flows through conduit G to condenser 30, whereat it liquefies.

A controlled amount of the condensed working fluid is transferred via conduit A to flasher 12 by means of a pressure differential between condenser 30 and flasher 12, as described above, and is then propelled by means of gaseous working fluid diverted via conduit B from the flasher to gas generator 22 via conduit C. The liquid working fluid remaining in flasher 12, after gaseous working fluid ceases to be diverted thereto, is then exposed via conduit D with the working fluid at a pressure level significantly below the vapor pressure of the liquid remaining in flasher 12, at the condenser 30, or as illustrated, slightly upstream to the condenser. A flash evaporation occurs and the small amount of the remaining working fluid in flasher 12 evaporates, allowing the condensate to be subsequently transferred to flasher 12.

In refrigeration loop 85, a portion of the condensate is diverted from conduit A of main circuit 215 downstream from condenser 30 to conduit H. The pressure and temperature of the liquid working fluid are reduced by expansion valve 83 operatively connected to conduit H so that the reduced- pressure working fluid temperature will be below ambient temperature. The pressure differential between condenser 30 and the exit of expansion valve 83 provides the driving force which causes the condensate to circulate within refrigeration loop 85. The reduced-pressure liquid or mixed phase working fluid flows through conduit I from expansion valve 33 to evaporator 86. The working fluid achieves a vapor phase at evaporator 86 to produce a cooling effect with respect to a desired volume.

Alternatively, as shown in Fig. 12, the discharge of gas generator 22 is split into parallel flows to conduits E and K, allowing both turbine 56 and ejector 87 to be fed by the highest available pressure of gaseous working fluid flowing through conduits E and K, respectively. A maximum amount of power can therefore be produced by means of turbine 56, and is unaffected by the ejector performance. That is, gas generator 22 may be customized to supply gaseous working fluid at a sufficiently high pressure to produce power by means of turbine 56, but need not be oversized so as to enable entrainment of the working fluid exiting the refrigeration cycle by the turbine discharge. Main circuit 216 of this coupled-cycle power generating system 220 has a conduit F that extends from turbine 56 directly to condenser 30. In refrigeration loop 85, conduit K diverted from conduit E extends to ejector 87, and the mixed stream discharged from ejector 87 flows through conduit G' and is combined with conduit F. Since ejector 87 is fed by the high-pressure gaseous working fluid produced by gas generator 22, the ejector performance is increased, thereby improving the cooling effect that may be achieved by means of refrigeration loop 85.

If so desired, as shown in Fig. 24, the working fluid fed to ejector 87 of coupled-cycle power generating system 225 may be produced by a second gas generator 23 at a different pressure and temperature than the working fluid produced by gas generator 22. The temperature and pressure of the working fluid produced by second gas generator 23 and flowing through conduit K' may be customized such that they are sufficiently high to enable entrainment of the working fluid exiting refrigeration loop 85 but not sufficiently high to produce an optimum power level by means of turbine 56. The ejector effluent and the turbine discharge are both delivered to condenser 30. The condenser discharge branches to three conduits leading to first gas generator 22, second gas generator 23, and to refrigeration loop 85, respectively. The condensate is transferred to first flasher 12 through conduit A and is then propelled to first gas generator 22 via conduit C, as described hereinabove. The condensate is also transferred to second flasher 13 via conduit A' branching from conduit A. Some of the gaseous working fluid produced by second gas generator 23 is diverted via conduit B' to second flasher 13 in order to propel the transferred liquid from second flasher 13 via conduit C to second gas generator 23. The liquid remaining in second flasher 13 is subjected to flash evaporation via conduit D' by means of the working fluid slightly upstream to condenser 30.

Alternatively, a single flasher may be employed, and the condensate transferred thereto may be propelled in parallel via conduits C and C to gas generators 22 and 23, respectively. The transferred condensate may be propelled by means of the gaseous fluid produced by one of the gas generators, or alternatively, the two diverting lines B and B' may both extend to the single flasher so that the condensate will be propelled alternately and controllably by the fluid produced by first gas generator 22 and then by the fluid produced by second gas generator 23.

In the embodiment illustrated in Fig. 13, the thermal efficiency of power generating system 240 is increased by reducing the temperature of the condensate. The working fluid in condenser 260 is subjected to flash evaporation by means of conduit L extending between the condenser and evaporator 266. A control valve 263 operatively connected to conduit L is periodically opened for a plurality of instances each hour to allow the condensed working fluid to be exposed to the working fluid at evaporator 266. The condensate flashes when it is exposed to the evaporate which is maintained at a significantly lower pressure than that of the condensate, causing the temperature of the condensate to drop. Although evaporator 266 is in periodic fluid communication with condenser 260, the operation of refrigeration loop 115 and the ejector performance are not disrupted or impaired since the volumetric flow rate of flash evaporate that flows to evaporator 266 is negligible with respect to the flow rate of working fluid that flows through expansion valve 83 to refrigeration loop 85 . The condensate is transferred to gas generator 22 via main circuit 265 by means of sub-circuit 75 and flasher 12, as described hereinabove.

A refrigeration system 242 illustrated in Fig. 14 may also be provided wherein the working fluid in condenser 260 is subjected to flash evaporation by means of conduit L extending between the condenser and evaporator 266. Ejector 87 is fed by the gaseous working fluid flowing through conduit K of main circuit 267 from gas generator 22, and also by the working fluid exiting evaporator 266 of refrigeration cycle 85.

Alternatively, as shown in Fig. 23, the condensate of combined power generating and refrigeration system 245, which may be subjected to flash evaporation by means of conduit L and control valve 263, is delivered to gas generator 22 via conduit T of main circuit 275 by means of pump 272. It will be appreciated that any other embodiment described herein may employ a condensate pump in lieu of the flasher based sub-circuit.

In power generating system 250 shown in Fig. 25, the temperature of the condensate is reduced by discharging a portion of the fluid received by condenser 262 before is it fully condensed via conduit Q to ejector 87. The suction pressure of ejector 87 provided by the fluid discharged from condenser 262 via conduit Q is less than the pressure of the ejector effluent flowing through conduit G to condenser 262, and therefore will reduce the temperature of the condensate. The pressure of the ejector effluent can be controlled by means of control valve 264, which is operatively connected to conduit L" extending from condenser 262 to conduit Q.

In power generating system 280 shown in Fig. 15, flash evaporated condensate can also be produced in condenser 260, which is fed from two parallel flows of main circuit 285 branching from gas generator 22. In power generating system 281 shown in Fig. 16, which is identical to power generating system 280 shown in Fig. 15 with the exception of the type of condenser, a direct contact heat transfer condenser 261 is employed .

Conventional condensers are of the shell and tube heat exchanger type wherein liquid of an external cooling system flows through the tubes and the turbine discharge is introduced through the shell side, to flow over the tubes and to be consequently condensed. Due to the thermal resistance of the tubes and the temperature level of the liquid flowing through the external cooling system, the temperature reduction of the working fluid by means of the external cooling system is limited. By employing a two-phase direct contact heat transfer condenser 261 by which the cooling liquid is the same medium as the working fluid and the turbine discharge vapor is in direct contact with the liquid condensate, whereby condensation of the turbine discharge takes place while in contact with the condensate rather than on the tubes, the temperature and pressure reduction of the working fluid within the condenser may be increased .

During a flash evaporation process when the reduced-pressure interior of condenser 261 is in communication with the interior of evaporator 266, the temperature of the condensate can be additionally reduced. Also, the efficiency of ejector 87 which is adapted to compress the vapor exiting evaporator 266 will be increased since it is in fluid communication with the reduced-pressure interior of condenser 261.

If so desired, a cooling stream flowing through the condenser can also be subjected to a flash evaporation process, in order to additionally reduce the temperature of the condensate.

It will be appreciated that any other embodiment described herein may employ a direct transfer condenser. In another embodiment illustrated in Fig. 17, the thermal efficiency of power generating system 290 is increased by reducing the pressure and temperature of the turbine discharge in a flash evaporation process. In main circuit 295, a pulse absorber 292 receives all of the two-phase discharge from turbine 306. The working fluid exiting pulse absorber 292 flows via conduit M to ejector 87. The working fluid vapor exiting evaporator 86 of refrigeration loop 300 via conduit J' mixes with the two-phase fluid discharged from pulse absorber 292 .

A conduit N extends from pulse absorber 292 to evaporator discharge conduit J'. Pulse absorber 292 is therefore in intermittent fluid communication with conduit J' by means of control valve 293 operatively connected to conduit N. Control valve 293 is periodically opened for a plurality of instances each hour to allow the turbine discharge to be exposed to the evaporator discharge which has a significantly lower pressure than that of the turbine discharge. The turbine discharge accordingly flashes when it is exposed to the evaporator discharge, resulting in an immediately decreased temperature and pressure as a result of the latent heat of evaporation. Control valve 293 is then closed after the turbine discharge flashes. The ejector effluent flows through conduit G to condenser 30. Since the turbine discharge is at a reduced temperature, a correspondingly reduced amount of work has to be applied to condenser 30 in order to suitably condense the working fluid.

Gas generator 22 is adapted to generate superheated working fluid at those conditions so that when the working fluid is expanded by turbine 306, the turbine discharge will have a quality of no more than 3-4%. Thus when the turbine discharge is subsequently subjected to flash evaporation, whereby all of the liquid phase portion flashes but not the vapor phase portion, the working fluid will remain saturated so that the evaporator discharge will be able to be entrained therein without resulting in flow choking conditions within ejector 87 that would reduce the performance thereof.. Despite the pulsatile nature of the flash process whereby the turbine discharge is intermittently subjected to pulses of low pressure evaporate and therefore periodically flashes, the flow within conduit M to ejector 87 and within conduit G to condenser 30 is nevertheless advantageously continuous. The volume of pulse absorber 292 is significantly greater, e.g. twice as great, than the designed volume of the turbine discharge that is received therewithin at any given moment so that the temporal flashing of a portion of the received turbine discharge within pulse absorber 292 will not affect the continuity of flow within conduit M

Fig. 18 illustrates a power generating system 310 that employs a pulse absorber 292 in conjunction with a main circuit 315 provided with two parallel conduits E and K branching from gas generator 22. Gaseous working fluid flows through conduit E to turbine 306 and through conduit K to ejector 87, whereat working fluid vapor exiting evaporator 86 of refrigeration loop 300 via conduit J' mixes with the gaseous working fluid. Pulse absorber 292 receives all of the discharge from turbine 306 and delivers the same, after having been subjected to flash evaporation by means of conduit N and control valve 293, via conduit M' to condenser 30 .

Fig. 19 illustrates a power generating system 320 that employs a pulse absorber 292 for reducing the temperature of the turbine discharge by means of flash evaporation as well as a conduit L extending between condenser 260 and evaporator 266 for reducing the temperature of the condensate by means of flash evaporation.

In power plant 321 shown in Fig. 20, both the turbine discharge and the condensate can be subjected to flash evaporation by means of flasher 12. Conduit D' extends from flasher 12 to conduit J through which working fluid exits evaporator 266. A conduit N' to which control valve 293 is operatively connected extends from pulse absorber 292 to conduit D'. A conduit L' to which control valve 263 is operatively connected extends from condenser 260 to conduit D'. Once flasher 12 has been exposed to the lowest pressure of the system at evaporator 266, one or both of pulse absorber 292 and condenser 260 can be exposed to flasher 12, to initiate a flash evaporation process.

In Fig. 21 is illustrated a power generating system 330 identical to power generating system 320 shown in Fig. 19, with the exception that pulse absorber 292 is in intermittent fluid communication with the condenser 260 by means of conduit P and control valve 333 operatively connected to conduit P. The turbine discharge is therefore subjected to flash evaporation since the condensate is at a significantly lower temperature than the turbine discharge.

As shown in Fig. 22, the flash evaporation processes may be initiated by means of a low pressure (LP) source 336 generated by a suitable component such as a vacuum pump, or by means of a plurality of low pressure sources, without need of a refrigeration loop. The thermal efficiency of power generating system 340 is therefore able to be dramatically reduced with respect to prior art power plants. Gaseous working fluid may be produced by means of waste heat or solar energy in generator 22 and delivered to turbine 306 via conduit E of main circuit 345. The turbine discharge is received in pulse absorber 292. When control valve 293 operatively connected to conduit N' extending between pulse absorber 292 and LP source 336 is opened, the temperature of the received turbine discharge is reduced by means of flash evaporation. The reduced temperature turbine discharge is delivered to condenser 260 via conduit V, and its temperature is further reduced when control valve 263 operatively connected to conduit L extending between condenser 260 and LP source 336 is opened to initiate an additional flash evaporation step. The condensate is transferred to gas generator 22 by means of a third flash evaporation step initiated by sub-circuit 338. Sub- circuit 338 is identical to sub-circuit 75 illustrated in Fig. 11, with the exception that a conduit D" extending from flasher 12 to LP source 336 is opened by means of control valve 343 operatively connected thereto, in order to cause flasher 12 to be exposed to LP source 336 and to thereby reduce the pressure of the liquid working fluid remaining in flasher 12 to a level below that of condenser 260 .

It will be appreciated that any other embodiment described herein may employ LP source 336 in lieu of the evaporator of a refrigeration loop.

The concept of liquid circulation by means of a heat source and flash evaporation may be utilized with respect to many different liquid circulation systems. Rather than using a pump or any other electrically powered device, the liquid is delivered from a low pressure source to a high pressure source by means of a flash evaporation process.

Example 1

The apparatus layout shown in Fig. 26 was used to demonstrate the operability of the liquid circulation method of the present invention.

Three reservoirs 401-403 were used to circulate the R134 working fluid. High pressure reservoir (HPR) 401 was maintained at a pressure of 22 bar and at a temperature of 71°C. Intermediate pressure reservoir (IPR) 402 was maintained at a pressure of 21 bar and at a temperature of 69°C, and low pressure reservoir (LPR) 403 was maintained at a fixed pressure ranging from 8-13 bar and at a corresponding fixed temperature ranging from 32-50°C.

A liquid accumulator 405 was placed in intermittent fluid communication with the three reservoirs 401-403 by means of a plurality of valves operatively connected to a fluid circuit. A conduit 421 was placed in fluid communication with the vapor region side of the accumulator interior and a conduit 422 was placed in fluid communication with the liquid region side of the accumulator interior. Conduit 426 with which control valve Gl was operatively connected extended from HPR 401 to junction 432 with conduit 421. Conduit 427 with which control valve G2 was operatively connected extended from junction 432 with conduit 421 to the vapor region side of LPR 403. Conduit 428 with which control valve LI was operatively connected extended from IPR 402 to junction 433 with conduit 422. Conduit 429 with which control valve L2 was operatively connected extended from junction 433 with conduit 422 to the liquid region side of LPR 403.

Each of reservoirs 401-403 was provided with a level sensor 411. Accumulator 405 was provided with a high level sensor 415 and a low level sensor 416. A controller was in electrical communication with the three level sensors 411, high level sensor 415 and low level sensor 416 of accumulator 405, and valves Gl-2 and Ll-2, to provide a predetermined control sequence.

When the liquid contained in accumulator 405 was greater than a predetermined low level as sensed by sensor 416, valves G2 and L2 were closed and valves Gl and LI were opened. Pressurized gas from HPR 401 propelled the liquid from accumulator 405 to IPR 402 until the liquid level in accumulator 405 was less than the predetermined value, the liquid level in HPR 401 was less than a predetermined value, or the liquid level in IPR 402 was greater than a predetermined level. Valves Gl and LI were closed when one of these three events was sensed.

Valve G2 was then opened, causing the high pressure liquid at 22 bar contained in accumulator 405 to be exposed to the low pressure liquid contained in LPR 403. The liquid contained within accumulator 405 became flash evaporated and was released to condenser 403. The pressure within accumulator 405 decreased below the fixed pressure level of LPR 403. Valve G2 was closed and valve L2 was opened. Due to the pressure differential- between LPR 403 and accumulator 405, liquid flowed from LPR 403 to accumulator 405 until sensor 415 sensed that its liquid level reach a predetermined high level. Valve L2 was then closed and valves Gl and LI were opened to start another liquid circulation cycle.

This layout clearly demonstrated that a controlled amount of liquid is repeatedly and reliably transferable from LPR 403 to IPR 402 without use of a pump.

Example 2

Fig. 27 illustrates liquid circulation system 420 for circulating liquid through a closed fluid circuit comprising conduits AA-FF from LPR 403 to HPR 401 .

HPR 401 is heated by heat source Q, e.g. at a pressure of 22 bar and at a temperature of 71°C, and LPR 403 is at a fixed pressure, e.g. ranging from 8-13 bar and at a corresponding fixed temperature ranging from 32-50°C. The type of heat source Q and the type of liquid that are employed determine the pressure level of HPR 401 and the pressure ratio between HPR 401 and LPR 403.

Flasher 405 is placed in intermittent fluid communication with the two reservoirs 401-403 by means of a plurality of valves operatively connected to the fluid circuit. A conduit EE is placed in fluid communication with the vapor region side of the flasher interior and a conduit FF is placed in fluid communication with the liquid region side of the flasher interior. Conduit AA with which control valve Gl is operatively connected extends from HPR 401 to junction 432 with conduit EE. Conduit BB with which control valve G2 is operatively connected extends from junction 432 to the vapor region side of LPR 403. Conduit DD with which control valve LI is operatively connected extends from junction 433 with conduit FF to HPR 401. Conduit CC with which control valve L2 is operatively connected extends from junction 433 with conduit FF to the liquid region side of LPR 403 .

Each of reservoirs 401-402 is provided with a level sensor 411. Flasher 405 is provided with a high level sensor 415 and a low level sensor 416. A controller is in electrical communication with the two level sensors 411, high level sensor 415 and low level sensor 416 of flasher 405, and valves Gl-2 and Ll-2, to provide a predetermined control sequence.

When the liquid contained in flasher 405 is greater than a predetermined low level as sensed by sensor 416, valves G2 and L2 are closed and valves Gl and LI are opened. Pressurized liquid from HPR 401 propels the liquid from flasher 405 to HPR 401 until the liquid level in flasher 405 is less than the predetermined value, the liquid level in HPR 401 is greater than a predetermined value, or the liquid level in LPR 403 is less than a predetermined level. Valves Gl and LI are then closed when one of these three events is sensed .

Valve G2 is then opened, causing the high pressure liquid at 22 bar contained in flasher 405 to be exposed to the low pressure liquid contained in LPR 403. The liquid contained within flasher 405 becomes flash evaporated and is released to LPR 403. The pressure within flasher 405 is reduced below the fixed pressure level of LPR 403. Valve G2 is closed and valve L2 is opened. Due to the pressure differential between LPR 403 and flasher 405, liquid flows from LPR 403 to flasher 405 until sensor 415 senses that its liquid level reaches a predetermined high level. Valve L2 is then closed and valves Gl and LI are opened to start another liquid circulation cycle. Example 3

In a power generating system 50 of Fig. 3, the vaporizer is heated by means of a single solar heated absorber reaching a maximum temperature of 90- 95°C, and is maintained at a temperature of 70°C and a corresponding saturation pressure of 21 bar for a R134 working fluid. The generated vapor is isobarically superheated to a temperature of 95°C by means of a second similar solar heated absorber. The superheated working fluid is delivered to the turbine and is discharged therefrom at a pressure of 8 bar. The turbine discharge is condensed at a temperature of 32°C. Higher temperatures at the vaporizer or superheater may be achieved when two or more solar absorbers are connected in series.

Example 4

In a combined power generating and refrigeration system 80 of Fig. 6, the vaporizer is heated by means of a single solar heated absorber reaching a maximum temperature of 90-95°C, and is maintained at a temperature of 70°C and a corresponding saturation pressure of 21 bar for a R134 working fluid. The generated vapor is isobarically superheated to a temperature of 95°C by means of a second similar solar heated absorber. The superheated working fluid is delivered to the turbine and is discharged therefrom at a pressure of 7-8 bar. The turbine discharge is condensed at a temperature of 32°C, and is delivered to a refrigeration loop. In the refrigeration loop, the liquid working fluid is expanded by the expansion valve to a pressure of 4-6 bar and is used for air conditioning.

While some embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried out with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of persons skilled in the art, without departing from the spirit of the invention or exceeding the scope of the claims.

Claims

1. A liquid circulation system, comprising a flasher having a plurality of controllably openable and closable ports by which said flasher is intermittently in fluid communication with- i. a low pressure reservoir (LPR), from which a controlled amount of liquid is transferable to said flasher by means of a pressure differential or a height differential between said LPR and said flasher; and

ii. a high pressure reservoir (HPR), from which is dischargeable a fluid at a sufficiently high pressure which will propel said controlled amount of liquid from said flasher to said HPR.

2. The liquid circulation system according to claim 1, wherein the flasher is also intermittently in fluid communication with one or more low pressure sources having a pressure less than the pressure of the LPR, for initiating flash evaporation of liquid contained within the flasher.

3. The liquid circulation system according to claim 1, wherein the liquid contained within the flasher is subjected to flash evaporation when the flasher is caused to be in fluid communication with the LPR, the pressure of evaporate immediately decreasing to a level below that or equal to of the liquid contained within the LPR.

4. The liquid circulation system according to claim 1, wherein the HPR is a gas generator and the LPR is a condenser.

5. The liquid circulation system according to claim 4, further comprising a closed, main conduit circuit through which the fluid for propelling the controlled amount of liquid sequentially circulates from the gas generator to the condenser, from the condenser to the flasher, and from the flasher to the gas generator.

6. The liquid circulation system according to claim 5, further comprising a sub -circuit comprising a first conduit through which the fluid is divertable from said main-circuit and downstream to the gas generator to the flasher.

7. The liquid circulation system according to claim 6, wherein the sub- circuit further comprises a second conduit extending from the flasher to a low pressure source having a pressure less than the pressure of the liquid contained within the flasher, for initiating a flash evaporation process.

8. The liquid circulation system according to claim 7, wherein the sub- circuit further comprises a controller and a plurality of control valves in electrical communication with said controller for opening the first conduit while the second conduit is occluded in order to propel the controlled amount of liquid from the flasher to the gas generator, for closing the first conduit and opening the second conduit in order to initiate a flash evaporation process with respect to liquid remaining within the flasher, and for closing the first and second conduits while the flasher is in liquid communication with the condenser so that the controlled amount of liquid will be transferred to the flasher.

9. The liquid circulation system according to claim 5, which is a power generating system, wherein the main circuit further comprises a turbine for producing power from gaseous fluid exiting the gas generator.

10. The liquid circulation system according to claim 5, which is a refrigeration system, wherein the main circuit further comprises an ejector which also receives fluid exiting a refrigeration loop.

11. The liquid circulation system according to claim 9, which is a combined power generating and refrigeration system, wherein a closed refrigeration loop is in communication with an expansion valve for sufficiently reducing the pressure of the fluid exiting the condenser so as to cool a desired volume when said reduced pressure fluid is evaporated.

12. The liquid circulation system according to claim 11, wherein the fluid exiting the refrigeration loop combines with the fluid in the main circuit flowing towards the turbine.

13. The liquid circulation system according to claim 11, wherein fluid discharged from the refrigeration loop is delivered to the turbine.

14. The liquid circulation system according to claim 11, wherein a conduit of the main circuit extends from the gas generator directly to the turbine.

15. The liquid circulation system according to claim 14, wherein an additional conduit branches from the conduit extending from the gas generator directly to the turbine, said additional conduit extending to an ejector which also receives fluid exiting the refrigeration loop.

16. The liquid circulation system according to claim 14, wherein all fluid discharged from the turbine is delivered to an ejector which also receives working fluid exiting a refrigeration loop.

17. The liquid circulation system according to claim 14, further comprising a first gas generator for delivering fluid to the turbine and a second gas generator for delivering fluid to an ejector which also receives fluid exiting the refrigeration loop.

18. The liquid circulation system according to claim 4, wherein the gas generator comprises a vaporizer.

19. The liquid circulation system according to claim 4, wherein the gas generator comprises a superheater.

20. The liquid circulation system according to claim 4, wherein the gas generator comprises a vaporizer and a superheater.

21. The liquid circulation system according to claim 5, further comprising a sub-circuit which comprises a compressing unit which is connected to the gas generator by means of one-way valve that permits the fluid to flow only from the gas generator to said compressing unit, and a conduit extending from said compressing unit to the flasher,

wherein said sub-circuit operates in a pulsate manner to maintain continuous flow of the fluid within the main circuit by raising the pressure of the liquid in the flasher to a sufficiently high level which is required in the main circuit.

22. The liquid circulation system according to claim 4, wherein a heat source associated with the gas generator is solar energy.

23. The liquid circulation system according to claim 4, wherein a heat source associated with the gas generator is waste heat.

24. The liquid circulation system according to claim 5, further comprising a controller which is adapted to command to propel the controlled amount of liquid from the flasher to the gas generator when a liquid level in the flasher approaches a full capacity and to command to open a control valve operative connected with a conduit extending between the condenser and flasher when a liquid level in the flasher approaches a predetermined low capacity.

25. The liquid circulation system according to claim 11, wherein the fluid exiting the refrigeration loop combines with the main circuit downstream from the condenser.

26. The liquid circulation system according to claim 2, wherein the one or more low pressure sources comprises an evaporator of a refrigeration loop.

27. The liquid circulation system according to claim 2, wherein the one or more low pressure sources is an external low pressure source.

28. The liquid circulation system according to claim 27, wherein the external low pressure source is generated by means of a vacuum pump.

29. The liquid circulation system according to claim 11, wherein the expansion valve is operatively connected to the main circuit and the flasher is an evaporative liquid accumulator which is in heat exchanger relation with a duct through which warm air from a volume to be cooled circulates.

30. The liquid circulation system according to claim 4, wherein the condenser is of a direct transfer type.

31. The liquid circulation system according to claim 2, which is a power generating system, wherein the HPR is a gas generator and the LPR is a condenser and a main circuit comprises a turbine for producing power from gaseous fluid exiting the gas generator, wherein the one or more low pressure sources is also used to subject heat depleted working fluid to flash evaporation and to thereby reduce the pressure and temperature of said heat depleted working fluid.

32. The liquid circulation system according to claim 31, wherein the heat depleted working fluid is condensate contained within the condenser.

33. The liquid circulation system according to claim 31, wherein the heat depleted working fluid is turbine discharge, said heat depleted working fluid being contained within a pulse absorber connected to a discharge end of the turbine.

34. The liquid circulation system according to claim 33, wherein the volume of the pulse absorber is significantly greater than the instantaneous volume of the turbine discharge that is received within the pulse absorber.

35. The liquid circulation system according to claim 34, wherein the turbine discharge has a quality of no more than 5%.

36. The liquid circulation system according to claim 1, which is a power generating system, wherein the HPR is a gas generator and the LPR is a condenser, further comprising a main circuit which comprises a turbine for producing power from gaseous fluid exiting said gas generator and an ejector for compressing fluid discharged from said turbine, wherein an ejector suction conduit extends from said condenser to said ejector, thereby reducing the pressure and temperature of condensate.

37. A liquid circulation method, comprising the sequential steps of: a) providing a liquid having a first pressure at a low pressure reservoir;

b) subjecting a flasher, while its interior is at a second pressure greater than said first pressure, to flash evaporation, whereby the pressure within said flasher interior decreases to a third pressure which is less than or equal to said first pressure;

c) opening a first conduit extending between said low pressure reservoir and said flasher, thereby causing a controlled amount of said liquid to be transferred to said flasher by means of a pressure differential or a height differential between said low pressure reservoir and said flasher;

d) occluding said first conduit;

e) opening a second conduit extending from a high pressure reservoir at a fourth pressure greater than said second pressure to said flasher and a third conduit extending from said flasher to said high pressure reservoir, thereby causing fluid from said high pressure reservoir to propel said transferred liquid to said high pressure reservoir via said third conduit until said flasher interior achieves said second pressure; and

f) occluding said second and third conduits.

38. The liquid circulation method according to claim 37, wherein the flasher is subjected to flash evaporation by opening a sub-circuit conduit extending between the flasher and a low pressure source having a pressure less than the first pressure.

39. The liquid circulation method according to claim 37, wherein the flasher is subjected to flash evaporation by causing the flasher to be in fluid communication with the low pressure reservoir.

40. The liquid circulation method according to claim 37, wherein the high pressure reservoir is a gas generator, the low pressure reservoir is a condenser, and the fluid which is not diverted via the second conduit to the flasher circulates from said gas generator to said condenser via a main circuit.

41. A system for increasing the thermal efficiency of a working fluid circulation system, comprising means for subjecting heat depleted working fluid to flash evaporation.

42. The system according to claim 41, wherein the means for subjecting heat depleted working fluid to flash evaporation comprises a low pressure source, a conduit extending from a pressure vessel containing said heat depleted working fluid at a pressure above the pressure of said low pressure source to said low pressure source, a control valve operatively connected to said conduit, and an actuator associated with said control valve for opening said control valve for a predetermined duration and for thereby exposing said heat depleted working fluid to said low pressure source so as to initiate a flash evaporation process and to reduce the pressure and temperature of said heat depleted working fluid.

43. The system according to claim 42, wherein the pressure vessel containing said heat depleted working fluid is a condenser.

44. The system according to claim 42, wherein the pressure vessel containing said heat depleted working fluid is a pulse absorber connected to a discharge end of a turbine.

45. The system according to claim 44, wherein the volume of the pulse absorber is significantly greater than the instantaneous volume of the turbine discharge that is received within the pulse absorber.

46. The system according to claim 44, wherein the turbine discharge has a quality of no more than 5%.

47. The system according to claim 42, wherein the low pressure source is an evaporator of a refrigeration loop.

48. The system according to claim 42, wherein the low pressure source is an external low pressure source.

49. The system according to claim 48, wherein the external low pressure source is generated by means of a vacuum pump.

50. The system according to claim 42, wherein the low pressure source is a condenser.

51. The system according to claim 41, wherein the working fluid circulation system is selected from the group consisting of a power plant, a refrigeration cycle, and a coupled power-refrigeration system.

52. The system according to claim 43, wherein the condenser is of a direct transfer type.

53. The system according to claim 42, wherein the low pressure source is a flasher intermittently in fluid communication with an evaporator of a refrigeration loop and with a gas generator.