Thermodynamic apparatus and methods

Abstract

A thermodynamic method employs a refrigerant liquid that is immiscible to a motive liquid. The refrigerant vapor is compressed and condensed by the action of the motive liquid that comes in contact with the refrigerant vapor directly. Since the two liquids are immiscible to each other and have different specific gravity, they can be separated for recirculation.

Description

This application claims priority from U.S. Provisional Application Ser. No. 60/676,715 filed May 2, 2005. The entirety of that provisional application is incorporated herein by reference.

The present invention relates generally to thermodynamic processes and, in particular, to methods and apparatus for cooling and refrigeration using vapor.

SUMMARY

One aspect of the present invention relates to a thermodynamic system comprising an evaporator, a hydrokinetic compressor, and a separator. The evaporator produces a refrigerant vapor, which is compressed and condensed to refrigerant liquid by the action of a motive liquid that comes into direct contact with the vapor in the hydrokinetic compressor. The refrigerant liquid and the motive liquid are substantially immiscible. The separator receives a blend of the refrigerant liquid and the motive liquid from the hydrokinetic compressor and allows separation of the refrigerant liquid and the motive fluid. The refrigerant liquid is then re-circulated to the evaporator.

Another aspect of the present invention relates to a thermodynamic method. Refrigerant vapor is generated from a refrigerant liquid. The refrigerant vapor is compressed and condensed into refrigerant liquid by the action of a motive liquid that comes into direct contact with the refrigerant vapor, wherein the refrigerant liquid and the motive liquid are substantially immiscible. Heat is rejected from the refrigerant liquid and the motive liquid. The refrigerant liquid and the motive liquid are separated. The refrigerant liquid and the motive liquid are then re-circulated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic showing the main components of the cooling system of the present invention.

FIG. 2 is a T-S diagram of a reversed Carnot cycle

FIG. 3 is a T-S diagram of an ideal non-adiabatic compression cooling (NACC) cycle.

FIG. 4 is a T-S diagram of a modified NACC cycle.

FIG. 5 is schematic showing an embodiment of a cooling system.

FIG. 6 depicts the actual performance of a test system.

FIG. 7 depicts projected performance of a test system.

FIG. 8 is a schematic showing a simplified heat driven cooling system.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

FIG. 1 shows an embodiment of a non-adiabatic compression cooling (NACC) system 100. In this embodiment, the system 100 comprises an expander 110, an evaporator 120, a hydrokinetic compressor (HC) 130, a pump 140, a heat exchanger 150, and a separator 160. The expander 110 and the evaporator 120 can be any expander and evaporator that allow efficient evaporation of the refrigerant liquid. In one embodiment, the expander 110 contains an expansion valve that controls the flow of refrigerant liquid to the evaporator 120. The refrigerant liquid then vaporizes into a gaseous state inside the evaporator 120, extracting heat from the surrounding environment (e.g., room air or food items in a refrigerator) in the process.

The HC 130 is a passive injector style device in which the refrigerant vapor is compressed and condensed by the action of motive liquid that comes in direct contact with the refrigerant vapor. In one embodiment, the HC 130 can be a hydrokinetic amplifier described in U.S. Pat. No. 4,569,635 (hereinafter '635 patent), herein incorporated by reference in its entirety. In this embodiment, HC 130 comprises two inlets, refrigerant vapor enters through the inlet for condensable vapor, and motive liquid enters through the liquid inlet. In the embodiment shown in FIG. 1, the motive liquid is pumped into the HC 130 by the pump 140, at a pressure sufficient to convert to high velocity within the HC, thereby entraining the low-pressure refrigerant vapor, compressing and simultaneously condensing the refrigerant vapor in an integral diffuser section of the HC 130.

The refrigerant/motive liquid pair is selected on the basis that they are substantially immiscible and have different densities in the liquid phase. The term “substantially immiscible” used hereinafter means less than 3 wt. %. The refrigerant liquid and motive liquid should be non-reactive, i.e., blending the refrigerant liquid with the motive liquid should result in very little (if any) chemical reaction or instability. The refrigerant liquid and motive liquid should also have differences in their respective vapor pressures, so that the refrigerant vapor feeding into the HC 130 is not opposed by high backpressure of the motive liquid.

Examples of the refrigerant fluids include, but are not limited to, low pressure refrigerant fluids (i.e., fluids with relatively high boiling points) such as hydrocarbon, hydrofluorocarbon, chlorinated hydrofluorocarbon, or halogenated hydrocarbon capable of being liquefied under conditions present within the hydrokinetic compressor. The examples include but not limited to butane (R600), R123, R245fa, R30, R11, R134a, R236fa, R404a, R407c, R153a methylene chloride and a mixture thereof.

Examples of the motive liquid include, but are not limited to, water, glycol, or triethylene glycol and a mixture thereof.

Any ratio is feasible, though one driving factor will be determining the miscibility of the motive solution with the refrigerant. For example, Glycols (anti-freeze) may be useful because they prevent the water from freezing under certain conditions and they also lower the vapor pressure of the motive liquid considerably.

In one embodiment, the refrigerant liquid and the motive liquid pair is butane/water. The two liquids are immiscible and have different densities (0.583 vs. 1). Moreover, water is characterized by very low vapor pressure, i.e. <1 psia at or near typical ambient temperatures, while butane has a vapor pressure well over 15 psia at normal chiller temperatures of 35-55F. This pressure difference allows the butane vapor to have unfettered access into the HC 130. It also provides a ‘suction’ on the evaporator 120 which causes the refrigerant fluid to vaporize. Other examples of the refrigerant/motive liquid pair include, but are not limited to, butane/water and glycol, R134a/water, and methylene chloride/ethylene glycol, isobutane/water, R123/water, virtually any hydrofluorocarbon (HFC) and water or a water/glycol (ethylene, diethylene, triethylene, or tetraethylene glycol) solution. Also R153a/water or certain other hydrocarbon refrigerants and water (propane, for example). Regarding the motive liquid, any of the glycols without water could be the motive fluid, provided they pass the immiscibility requirement.

Within the HC 130, the refrigerant fluid and the motive fluid are intimately blended. The refrigerant fluid undergoes a phase change from vapor (preferably at saturation) to sub-cooled liquid as together the motive liquid and entrained refrigerant fluid move from a high velocity low pressure state to a low velocity high pressure state. In one embodiment, the HC 130 comprises a central liquid nozzle, a constricted throat, and a diffuser. The motive liquid passes through the central liquid nozzle and is then surrounded by entering refrigerant vapor. The two fluids combine into a single stream, which moves in an axial direction through the constricted throat section and then through the diffuser, prior to discharging from the HC 130.

After leaving the HC 130, the blend of the refrigerant liquid and the motive liquid passes through the heat exchanger 150 (which dissipates heat energy to, for example, ambient air or water) and enters the separator 160.

Since the refrigerant liquid and the motive liquid are immiscible, they do not form a solution. Having different specific gravities given adequate time, the liquids naturally separate from each other in the separator 160. The refrigerant liquid then is ready to re-circulate on to the expander 110 and continue its cycle. The natural separation of the refrigerant liquid and motive liquid does not require any added energy such as heat, therefore reducing the complexity of the system while significantly improving the efficiency of the cooling cycle. Alternatively, any type of separator can be employed.

The cooling system of the present invention also takes the advantage that a vapor can be condensed into some other liquid compound and result in a blend or solution with a temperature significantly higher than either of the fluids comprising the mixture. The relationship of the vapor pressure of the first fluid (the liquid), and subsequently the blend at any given time, to the pressure of the vapor being condensed allows this phenomenon to occur. As the condensing vapor gives up its latent heat to the blend, the temperature of the blend will rise and can exceed the temperature of the condensing vapor itself. Provided that the vapor pressure of the liquid blend remains low, the refrigerant vapor will continue to feed in and condense, giving up more latent heat and causing a further temperature rise. This disparity in the pressures provides the access required for the vapor to continue to feed into the blend. In an embodiment of the present invention, this phenomenon occurs as the refrigerant fluid condenses within the HC 130, therefore allows the HC 130 to suck in the refrigerant vapor from the evaporator 120.

Regarding the components of the cooling system 100, aside from incidental valves and controls, the only moving (rotary) component is the pump 140. The pump motor represents all of the work input into the system 100. Its purpose is to raise the pressure of the motive liquid (e.g., water or a water/glycol mix) exiting the separator 160 and thereby creating the velocity required at the HC 130s liquid nozzle.

The system 100 can be constructed using readily available equipment at low cost. The separator 160 is merely a pressurized tank, sized as to provide the required dwell time for the refrigerant liquid and the motive liquid (e.g., butane/water or R1134a/water) to separate. The HC 130, which compresses and condenses the refrigerant vapor, and provides the suction on the evaporator 120, can be the hydrokinetic amplifier described in the U.S. Pat. No. 4,569,635 (e.g., a HelioPAC™ hydrokinetic amplifier). Heat acquisition and rejection occur via conventional plate-and-frame or shell-and-tube heat exchangers, or fan coils. Heat transfer can be either to circulating water or air.

The Coefficient of Performance (COP) of the system 100 can be very high because the theoretical work requirement to condense the refrigerant vapor is much lower than even that of an ideal fuctionless and adiabatic (isentropic) compression process. The system 100 uses the high velocity of the motive liquid to first entrain the vapor and secondly to compress and condense it, as it absorbs its latent heat of condensation. This is a non-adiabatic process and more resembles an isothermal compression, i.e. heat of compression is rejected. The entropy of the vapor decreases as it undergoes compression and condensation whilst the latent heat is transferred to the motive liquid. As mentioned previously, the only work input in the basic design is power to run the pump motor. For the modified heat driven designs, only a condensable vapor is needed and no rotary components are required, except for equipment to accomplish heat rejection to atmosphere (fans or circulating pumps).

In one embodiment, the cooling system 100 is driven by electricity. For example, the pump 140 may be an electric pump. However, the system 100 can also be a heat driven system without the aid of the mechanical pump 140. FIG. 8 provides a schematic of a heat driven cooling system 200. In this embodiment, the motive liquid from the separator 260 is divided into two flows. The first flow (Stream A) passes through a heat exchanger 252 and feeds into an acceleration chamber 232 of a modified hydrokinetic compressor (HC 230). The modified hydrokinetic compressor is described in the U.S. Pat. No. 4,781,537 (the '537 patent), herein incorporated by reference in its entirety. In this embodiment, Stream A enters the primary liquid inlet described in the '537 patent. The second flow (Stream B) passes through a control valve 244 and enters a boiler 242, which produces a low or intermediate pressure vapor which converts to high velocity vapor in the HC 230. Stream B enters the vapor inlet described in the '537 patent. Vapor can be generated using solar power or other heat source, such as waste heat. The vapor is then fed into the acceleration chamber 232 of the HC 230 and transfers its kinetic energy to the motive liquid from Stream A. The acceleration that the motive vapor gives to the motive liquid allows the refrigerant vapor to be entrained in a condensation chamber 234 of the HC 230, where the refrigerant vapor is compressed, condensed and blended with the motive liquid. The refrigerant enters the HC 230 through the secondary fluid inlet described in the '537 patent. The liquid blend is then discharged from the HC 230 at a pressure suitable for continuing the cycle. The heat contained in the refrigerant liquid is released in a heat exchanger 254 before the refrigerant liquid re-enters the expander 210. One skilled in the art would understand that the heat exchanger 252 and 254 can be a single unit with separate fluid paths for the motive liquid and refrigerant liquid, respectively.

Thermodynamic Analysis

While the HC 130 is an adiabatic blending device, the compression and condensation of the vapor itself is not adiabatic due to its transfer of heat (latent heat of condensation) to the companion, motive fluid. Isothermal compression/condensation would occur in the HC 130 under various conditions. Accordingly, the compression cooling cycle employed in the present invention is a non-adiabatic compression cooling (NACC) cycle.

As shown in FIG. 2, the reversed Carnot Cycle represents the ideal vapor compression refrigeration cycle. In the T-S diagram, the four reversible processes of the cycle form a rectangular configuration. The area of the rectangle indicates work input into the cycle. In the reversed Carnot Cycle, the COP is a function of the two temperatures (refrigerated space and heat sink) and is expressed as follows:
COP=T_RΔS/(T_OΔAS−T_RΔS)  (1)

where, T_R=temperature of refrigerated space, degrees absolute

T_O=temperature of heat sink (ambient), degrees absolute

ΔS=entropy change

As shown in FIG. 3, an ideal NACC cycle, utilizing the HC 130 as the compressor/condenser, creates a triangular configuration on the T-S diagram. In this cycle, the compression, condensation and heat rejection of the refrigerant fluid occur simultaneously as one process. To wit, in the diffuser section of the HC 130, the motive liquid (e.g., water) pressurizes the refrigerant vapor (e.g., butane) while absorbing its latent heat of condensation. Accordingly, the cycle now contains three steps: (1) isentropic expansion 2-3; (2) isothermal heat acquisition 3-1; (3) non-adiabatic compression and condensation 1-2. Referring again to the T-S diagrams of FIGS. 2 and 3, the area of the triangle in FIG. 3 is exactly half that of the rectangle of the reversed Carnot cycle in FIG. 2, all else being equal. The COP of the ideal NACC cycle can be expressed as follows:
COP=(T_R ΔS)/[(ΔT ΔS)/2]  (2)

Accordingly, the COP of an ideal NACC cycle of the present invention is twice the COP of a reversed Camot Cycle operating between the same two temperatures.

In practice, the HC 130 will allow the temperature of the motive liquid/condensed refrigerant fluid blend to rise somewhat above ambient temperature. As shown in FIG. 4, this temperature increase will create a four step cycle on the T-S diagram, with heat rejection occurring at constant pressure external to the HC 130 (step 2-3). This four step cycle requires some additional work input and departs slightly from the ideal triangular shaped cycle. However, the potential improvement over any other actual cycle is still very significant.

Referring to FIG. 4, this cycle will be termed the Modified Ideal NACC Cycle and, the COP may be expressed as follows: $\begin{array}{cc}\mathrm{COP}=\frac{\begin{array}{c}\left[T_1\left(S_1-S_4\right)\right]/\left[\left(T_2-T_1\right)+\left(T_3-T_1\right)\right]\times \\ \left(S_2-S_4\right)+\left[\left(T_2-T_1\right)\times \left(S_1-S_2\right)\right]\end{array}}{2}& \left(3\right)\end{array}$

where T₃ is equal to the motive liquid temperature in the HA. T2 is the warmed condensed refrigerant fluid (and motive liquid) exiting the HC diffuser.

Equation (3) indicates that maintaining a low T₂ will allow for the least amount of work input to the cycle. However, this will occur at the expense of higher motive liquid flows through the HC, i.e. a higher ratio of motive liquid to refrigerant fluid. It is necessary to find a balance between economic practicalities regarding flow rates, pumping requirements, heat exchange surface and the highest achievable COP. The NACC system can be characterized as having two (2) distinct cycles with two different fluids. The two cycles operate in parallel and interact with each other. The primary work is done upon the first fluid (i.e., the motive liquid), which then does work upon the second fluid (i.e., the refrigerant fluid). As shown in the Examples, the test unit of the NACC system produced COP values quite competitive with conventional equipment in the marketplace.

The present invention is further illustrated by the following examples which should not be construed as limiting. The contents of all references, patents and published patent applications cited throughout this application, as well as the Figures and Tables are incorporated herein by reference.

EXAMPLE

Performance of the NACC System

FIG. 5 depicts the basic configuration and projected heat balance of a NACC system using n-butane as the refrigerant fluid and water as the motive liquid. In some preliminary tests, this un-optimized test system produced cooling at rates of about ±½ to ¾ Ton. Significant, cooling has been accomplished such as chilling ambient temperature water by 30° F. or more, e.g. 78° F. to 45° F. EER values over 7 were achieved at the boundary temperatures shown and increased to greater than 11 when expansion valve exit is raised to 55° F. sat.

In the subsequent tests, this unit typically accomplishes cooling at a rate of about 1.7 to 2.6 KW (0.5 to 0.75 Ton) and net EER values have exceeded 10.9 (COP>3.2) at customary boundary temperatures, i.e. about 50° F.-55° F. on the low side and 95F at the high end. FIG. 6 depicts the actual performance of the test system from real test data (Case 1). Importantly, this particular sample is not the best performance the unit has achieved, yet is typical of actual operation within a group of the better performing runs to date.

It is possible to move from a hydrocarbon refrigerant fluid to a more commercially acceptable product, e.g. environmentally benign and ASHRAE Safety Rating A1. However, from a technical standpoint not every fluid meeting these commercial criteria is automatically suited for NACC use. R134a appears to be an excellent candidate for this application. FIG. 7 depicts projected performance of the NACC when utilizing R134a as the refrigerant fluid (Case 2) and adhering very closely to the proven capabilities of the system as documented in FIG. 6 (Case 1). Note that the COP has more than doubled when replacing the hydrocarbon with HFC R134a. A comparison of the key parameters of the two systems is described below. In both cases, overall efficiencies of 75% are assumed for all electrically driven devices with high efficiency motors set at 0.92 and pumps or other ‘prime movers’ at 0.82, i.e. 0.92×0.82=0.754=75% eff.

Of primary importance in accurately predicting how HFC 134a should perform relative to the existing hydrocarbon is to maintain volumetric flow rates exiting the Evaporator essentially the same for both cases, while also maintaining the same pressure ratio (Pr) with respect to the high and low side of the system. This ensures that the ‘compressor’ component of the design is called upon to perform equivalent work in each case. This projection reflects that constraint, though of significance is the fact that for Case 2, using R134a, the Pr actually only need be 1.98 at the specified temperatures, rather than 2.34. Nonetheless, to achieve a fully valid comparison the Pr has been held equal to that of Case 1, providing in Case 2 a level of downstream subcooling not necessary. In addition, in the interest of being conservative in the projections, the power input at the “Electric Motor Driver” is increased and the actual cubic feet per minute (ACFM) is reduced by about 3%. The exit temperature of the cooling water of Case 2 is higher than Case 1, indicating (when allowing for a 1° F. terminal difference within the NACC) that Case 2 is operating at higher ambient temperature, which is normally a detriment for a cooling system. All else being equal, these changes might be expected to decrease system EER from Case 1. However, because the HFC vapor is significantly more dense (lbs./ft³) than the refrigerant fluid in Case 1, mass flow rate increases proportionately and therefore the cooling also increases dramatically at the Evaporator. Again, the net result is a COP over twice that for Case 1. Nothing else of material significance has changed in the two designs.

Refrigerant Fluids

Various refrigerant fluids have potential utility in the NACC cycle. The search for the optimum one(s) can be quickly narrowed down by eliminating those products being phased out for environmental reasons and those which have potential health and safety risks (flammability, toxicity, etc.).

As indicated above, Case 2, employing R134a, allows for about 4½ times more refrigerant fluid by mass to circulate at equivalent volumetric flow rates of Case 1 (exiting the Evaporator en route to the re-compression step). This enables proportionately greater cooling to occur over and above the capacity of the hydrocarbon presently used, allowing of course for latent heat differences of the fluids. The question arises whether more work is needed downstream to compress the refrigerant fluid substitute. All else being equal, in an isothermal compression process, higher molecular weight (MW) gases will compress with less effort per unit mass than those of lower MW. Significantly, R134a (MW 102.03) is nearly 1.8 times heavier than the hydrocarbon in use. Non-adiabatic compression bears similarities to isothermal compression and it can be expected that compression, i.e. work input, demands per pound fluid will be decreased roughly proportional, i.e. by that same factor of 1.8. With this in mind, it is evident that R134a is beneficial in this regard (as opposed to moving to a lighter MW fluid).

The above description is for the purpose of teaching the person of ordinary skill in the art how to practice the present invention, and it is not intended to detail all those obvious modifications and variations of it which will become apparent to the skilled worker upon reading the description. For example, although the embodiments above relate to a cooling system and method, the system can also be employed as a heating system and method by capturing heat from the heat exchange in the surrounding environment (e.g. room air). In fact, the embodiments may be employed in any heat transfer application. It is intended, however, that all such obvious modifications and variations be included within the scope of the present invention, which is defined by the following claims. The claims are intended to cover the claimed components and steps in any sequence which is effective to meet the objectives there intended, unless the context specifically indicates the contrary.

Claims

1. A thermodynamic system comprising:

an evaporator that produces a refrigerant vapor;

a hydrokinetic compressor connected to said evaporator, wherein said refrigerant vapor is compressed and condensed to refrigerant liquid by the action of a motive liquid that comes into direct contact with said refrigerant vapor, wherein said refrigerant liquid and said motive liquid are substantially immiscible; and

a separator, connected to said evaporator and said hydrokinetic compressor, wherein said separator receives a blend of said refrigerant liquid and said motive liquid from said hydrokinetic compressor and enables separation of said refrigerant liquid and said motive fluid, wherein said refrigerant liquid is re-circulated to said evaporator.

2. The thermodynamic system of claim 1, wherein said separator enables a natural separation of said refrigerant liquid and said motive fluid by gravity.

3. The thermodynamic system of claim 1, wherein said thermodynamic system is a cooling system.

4. The thermodynamic system of claim 1, further comprising an expander connected to said separator and said evaporator, wherein said expander controls the flow of said refrigerant liquid from said separator to said evaporator.

5. The thermodynamic system of claim 4, wherein said expander includes an expansion valve which controls the flow of said refrigerant liquid.

6. The thermodynamic system of claim 1, further comprising a mechanical pump that pumps said motive liquid into said hydrokinetic compressor.

7. The thermodynamic system of claim 1, further comprising a heat exchanger that receives a blend of said refrigerant liquid and said motive liquid from said hydrokinetic compressor, dissipates heat from said blend, and returns cooled blend to said separator.

8. The thermodynamic system of claim 1, wherein said refrigerant liquid includes a hydrocarbon, hydrofluorocarbon, chlorinated hydrofluorocarbon, or halogenated hydrocarbon, or a mixture of two or more thereof, and wherein said motive liquid includes water, glycol, triethylene glycol or a mixture thereof.

9. The thermodynamic system of claim 8, wherein said refrigerant liquid includes butane and said motive liquid includes water or a mixture of water and glycol.

10. The thermodynamic system of claim 1, further including a heat-driven vaporizer that receives said motive liquid from said separator and generates the action of said motive liquid by heating and vaporizing a portion of said motive liquid.

11. The thermodynamic system of claim 10, wherein said heat-driven vaporizer uses waste heat.

12. The thermodynamic system of claim 1, further comprising a solar powered device that receives said motive liquid from said separator and generates the action of said motive liquid by heating and vaporizing a portion of said motive liquid.

13. The thermodynamic system of claim 1, wherein said hydrokinetic compressor comprises a central liquid nozzle, a constricted throat, and a diffuser.

14. The thermodynamic system of claim 1, wherein said motive liquid is re-circulated from said separator to said hydrokinetic compressor via a power device.

15. The thermodynamic system of claim 1, wherein said power device is powered by electricity, heat or solar power.

16. A thermodynamic method comprising:

generating a refrigerant vapor from a refrigerant liquid;

compressing and condensing said refrigerant vapor into refrigerant liquid by the action of a motive liquid that comes into direct contact with said refrigerant vapor, wherein said refrigerant liquid and said motive liquid are substantially immiscible;

releasing heat from said refrigerant liquid and said motive liquid;

separating said refrigerant liquid and said motive liquid; and

re-circulating said refrigerant liquid and said motive liquid to complete a cooling cycle.

17. The method claim 16, wherein said refrigerant liquid includes a hydrocarbon, hydrofluorocarbon, chlorinated hydrofluorocarbon, or halogenated hydrocarbon, or a mixture of two or more thereof, and wherein said motive liquid includes water, glycol, triethylene glycol or a mixture thereof.

18. The method claim 17, wherein said refrigerant liquid includes butane and said motive liquid includes water or a mixture of water and glycol.

19. The method claim 16, wherein said refrigerant liquid and said motive liquid are separated naturally by gravity

20. The method claim 16, wherein the action of the motive liquid is generated by mechanical force.

21. The method claim 16, wherein the action of the motive liquid is generated by waste heat or solar power.

22. A thermodynamic method comprising:

generating a refrigerant vapor from a refrigerant liquid;

compressing and condensing said refrigerant vapor into refrigerant liquid by the action of a motive liquid that comes into direct contact with said refrigerant vapor, wherein said refrigerant liquid and said motive liquid are substantially immiscible; wherein the heat of condensing of said refrigerant increases the temperature of the motive liquid;

separating said refrigerant liquid and said motive liquid; and

re-circulating said refrigerant liquid and said motive liquid to complete a cooling cycle.

23. A method of vapor compression refrigeration comprising:

transferring part of the kinetic energy of a motive fluid to a refrigerant vapor in a passive blending device, the energy transfer thereby resulting in compression and liquification of the vapor within the blending device, wherein mechanical work is performed upon the motive liquid to impart kinetic energy on the motive liquid, but no mechanical work is performed on the vapor refrigerant.