Patent Application
20090056645
The invention is a liquid heater which heats a reservoir of aqueous liquid by inducing flux stress within the liquid. A flux stress inducing device, which may be a cavitration device, including its electric motor in one version, is immersed in the liquid in the vessel. Hot water, steam, vapor and blowdown are readily removed from the reservoir in a conventional manner.
It is known that turbulence, shear, and cavitation within a liquid will elevate its temperature. For many purposes, the generation of shear, turbulence and cavitation is considered to be a waste of energy, and much attention in pump design, for example, has been devoted to avoiding or suppressing these effects. Some workers, however, have sought to take advantage of the fact that the temperature of the liquid may be elevated without the use of flame or even a heat transfer surface of any kind, and have designed machines deliberately to subject the fluid in them to such tortuous flow. Typically, the liquid passes through the machine for heating and flows to a different location for heat transfer or other use, and is continuously recycled to the machine. See, for example, Pope U.S. Pat. No. 5,341,768.
While the art has used such machines for heating flowing liquids, to our knowledge it has not successfully designed an apparatus to elevate the temperature of a body of water within a vessel, tank, boiler, or other reservoir by turbulence, shear, and/or cavitation
We have invented a water heater using a flux stress device to supply heat. The flux stress device is immersed within the water heater reservoir. Placing the flux stress device within the reservoir enables excellent circulation of hot liquid within the vessel (reservoir) and excellent control of the heating process. The flux stress device can heat a wide variety of solutions and slurries.
It is known to convert mechanical energy into thermal energy in a fluid by causing the fluid to follow a tortuous or stressful path to create shear, turbulence, cavitation or a combination of one or more of these. A tortuous path may be one featuring diversions, obstacles or protuberances which induce significant turbulence. An example of a stressful path for generating shear is one passing between two closely opposing surfaces, one of which is advantageously moving with respect to the other. A paradigm of a cavitation path is a path including cavities capable of alternately creating and imploding low-pressure vacuities in the fluid. We use the term “flux stress” to describe generically all three of these effects, and a flux stress device to mean any device which will elevate the temperature of a fluid by flux stress. It is immaterial for our purposes whether the flux stress causes an alteration or physical degradation of a component of the fluid, such as a viscosity-imparting polymer. We define “flux stress” as shearing (sometimes called “shear stress,” or simply “shear”), turbulence, or cavitation, or a combination of more than one of these, resulting in the heating of a fluid, wherein thermal energy is induced in the fluid by the stress of the shearing, turbulence, or cavitation. In addition, some devices of the prior art recognize friction within a device as an effect which will heat fluid in it. In many such prior art cases, friction implies primarily a form of stress caused by flowing against solid parts which may or may not be designed deliberately to cause a tortuous flow, and may even in some cases imply the generation of heat due to the motion or resistance of solid particles suspended in the fluid. Because turbulence-induced heat is the primary result in either case, we do not intend to exclude friction, so defined, as a phenomenon which elevates the temperature of the fluid in a flux stress device.
The substantially parallel surfaces frequently used to create shearing and/or turbulence need not be planar or cylindrical surfaces—for example, a conical surface may be nested within and close to another conical surface, and the fluid caused to flow between the two surfaces, one or both of which may be turning; if both are turning, they will advantageously turn in opposite directions. Turbulence and shearing between two closely aligned surfaces or within a conduit or passage induces thermal energy within the fluid from the mechanical energy of the fluid flux, without dependence on a heat transfer surface, and the generation of thermal energy may be enhanced by rotating or otherwise moving one surface with respect to the other while the fluid is caused to pass between them.
Cavitation devices are designed deliberately to generate heat by cavitation. Cavitation occurs in a fluid when the fluid flows in an environment conducive to the formation of partial-vacuum spaces or bubbles within the fluid. Since the spaces or bubbles are partial vacuum, they almost immediately implode, causing the mechanical or kinetic energy of the fluid to be converted into thermal energy. In many devices, such as most pumps, cavitation is an occurrence to be avoided for many reasons, not least because of convulsions and disruption to the normal flow in the pump, but also because of the loss of energy when the mechanical energy of the pump is converted to undesired heat instead of being used to propel the fluid on a desired path. There are, however, certain devices designed deliberately to achieve cavitation in order to increase the temperature of the fluid treated. Such cavitation devices are manufactured and sold by Hydro Dynamics, Inc., of Rome, Ga., most relevantly the devices described in U.S. Pat. Nos. 5,385,298, 5,957,122 6,627,784 and particularly 5,188,090, all of which are hereby specifically incorporated herein by reference in their entireties. These patents may be referred to below as the HDI patents.
The basic design of the cavitation devices described in the HDI patents comprises a cylindrical rotor having a plurality of cavities bored or otherwise placed on its cylindrical surface. The rotor turns within a closely proximate cylindrical housing, permitting a specified, relatively small, space or gap between the rotor and the housing. Fluid usually enters at the face or end of the rotor, flows toward the outer surface, and enters the space between the concentric cylindrical surfaces of the rotor and the housing. While the rotor is turning, the fluid continues to flow within its confined space toward the exit at the other side of the rotor, but it encounters the cavities as it goes. Flowing fluid tends to fill the cavities, but is immediately expelled from them by the centrifugal force of the spinning rotor. This creates a small volume of very low pressure within the cavities, again drawing the fluid into them, to implode or cavitate. This controlled, semi-violent action of micro cavitation brings about a desired conversion of kinetic and mechanical energy to thermal energy, elevating the temperature of the fluid without the use of a conventional heat transfer surface.
Benefits of the HDI cavitation devices include that they can handle slurries as well as many different types of solutions, they can be used to concentrate such slurries and solutions by facilitating the removal of steam and vapor from the fluid being treated, and the heating of the fluid occurs within the fluid itself rather than on a heat exchange surface which might be vulnerable to scale formation and ultimately to a significant reduction in heat transfer.
Definition: We use the term “cavitation device” to mean and include any device designed to impart thermal energy to flowing liquid by causing bubbles or pockets of partial vacuum to form within the liquid it processes, the bubbles or pockets of partial vacuum being quickly imploded and filled by the flowing liquid. The bubbles or pockets of partial vacuum have also been described as areas within the liquid which have reached the vapor pressure of the liquid. The turbulence and/or impact, sometimes called a shock wave, caused by the implosion imparts thermal energy to the liquid, which, in the case of water, may readily reach boiling temperatures. The bubbles or pockets of partial vacuum are typically created by flowing the liquid through narrow passages which present side depressions, cavities, pockets, apertures, or dead-end holes to the flowing liquid; hence the term “cavitation effect” is frequently applied, and devices known as “cavitation pumps” or “cavitation regenerators” are included in our definition. Steam generated in the cavitation device can be separated from the remaining, now concentrated, water and/or other liquid which frequently will include significant quantities of solids small enough to pass through the device. The term “cavitation device” includes not only all the devices described in the above itemized HDI U.S. Pat. Nos. 5,385,298, 5,957,122 6,627,784 and 5,188,090 but also any of the devices described by Sajewski in U.S. Pat. Nos. 5,183,513, 5,184,576, and 5,239,948, Wyszomirski in U.S. Pat. No. 3,198,191, Selivanov in U.S. Pat. No. 6,016,798, Thoma in U.S. Pat. Nos. 7,089,886, 6,976,486, 6,959,669, 6,910,448, and 6,823,820, Crosta et al in U.S. Pat. No. 6,595,759, Giebeler et al in U.S. Pat. Nos. 5,931,153 and 6,164,274, Huffman in U.S. Pat. No. 5,419,306, Archibald et al in U.S. Pat. No. 6,596,178 and other similar devices which employ or include a shearing effect between two close surfaces, at least one of which is moving, such as a rotor, and/or at least one of which has cavities of various designs in its surface (a cavitation zone) as explained above. Shearing and turbulence commonly occurs in cavitation devices, and possibly should not be ignored in considering their heat generating abilities, but most of the thermal energy imparted to the liquid in a cavitation device is by way of cavitation, by definition.
As a means for heating or boiling water or other aqueous fluids, the existing designs of cavitation devices exhibit many benefits, but there remains a need for improvement. It is difficult to control the separation of steam and vapor from the remaining concentrated liquid at the exit of the device. As one approach to this problem, at least a portion of the heated throughput of the cavitation device may be sent to a flash tank, for the separation of liquid and gaseous or vapor phases, thus necessitating a whole set of additional equipment, valves and controls. Also, the typical cavitation device would benefit from a practical method of maintaining pressure on the cavitation zone, to enhance the cavitating effect.
Our invention includes a boiler using a cavitation device to supply heat. The cavitation device is within the boiler vessel and may be totally immersed. Placing the cavitation device within the vessel enables excellent circulation of hot fluid within the vessel and recycling of the fluid through the (desirably) immersed cavitation device to provide excellent control of the heating process entirely within the vessel. The cavitation device can heat a wide variety of solutions and slurries.
While we describe our invention as in many instances using a cavitation device, we may also use various flux stress devices which do not provide heating by cavitation. Such devices include, broadly, dynamometers (some of which have come to acquire that name in spite of the fact they may not measure anything) and water brakes. Water brakes and other types of absorbing dynamometers convert the energy of a rotor on a turning shaft into thermal energy due to the turbulence and/or shear stress generated in the fluid passed by it in proximity to another surface, some of which may include protuberances to cause local turbulence but not cavitation.
Our invention includes a method of making steam comprising causing flux stress by a flux stress device at least partially submerged in a body of aqueous fluid within a reservoir, which may be called a boiler or boiler vessel.
Our invention includes a method of making steam comprising causing cavitation by a cavitation device at least partially submerged in a body of aqueous fluid within a boiler. By “aqueous fluid” we mean liquid water such as would normally occupy a significant portion of a boiler vessel. But because of the ability of our invention to handle a wide variety of solutions and slurries, we intend for the term “aqueous fluid” to include solutions and slurries of water including up to and even in excess of 50% non-water materials by weight, either dissolved, particulate (if the particulates are suspended in the liquid, they will desirably be of a size able to pass through the cavitation device), or both, and including the possibility of organic liquids and/or other non-aqueous liquids. For example, the term aqueous fluid thus includes many types of industrial fluids, including used oilfield fluids. The cavitation device will normally be immersed in the aqueous fluid, but can operate when it is only partially submerged. Our invention thus includes a boiler or boiler vessel having a cavitation device within the boiler or boiler vessel as a source of heat. Our invention is useful for heating or boiling any aqueous fluid as defined above.
Any such aqueous fluid is introduced to a reservoir and removed as heated fluid, either as a liquid, steam, or vapor. This process may be substantially continuous, as is frequently the case with a boiler, or it may be intermittent, as is commonly the case with a water heater. Our objective is to heat the body of water in the reservoir where it is utilized as a source or supply of steam, vapor, or heated liquid. To further describe this process, we use the term “makeup liquid” for the aqueous fluid which is continuously or intermittently introduced to the reservoir, which may be a boiler vessel. Makeup liquid is fresh incoming liquid in the sense that it is not recycled from the reservoir.
We use the word “reservoir” for its dictionary meaning, “a receptacle or chamber for storing a fluid.” We use it to include the term “vessel.” “Reservoir” is used in the context of our invention to emphasize that the flux stress device is immersed in aqueous fluid within the receptacle or chamber, sometimes herein called a vessel, capable of “storing” as that term is used in the definition of “reservoir.” That is, the reservoir serves as a more or less continuously available source of hot water, steam or vapor, which may be continuously or intermittently removed from it while the source is continuously or intermittently replenished by makeup liquid. While the aqueous fluid will pass through the cavitation device or other flux stress device, and therefore may circulate substantially continuously within the reservoir so that it will circulate through the flux stress device to attain higher temperatures, once the heated aqueous fluid is removed from the reservoir either as hot fluid or steam, it does not return, as it normally will be consumed or expended in any of many possible ways. The reservoir containing the flux stress device may be called either a water heater (aqueous fluid, or liquid, heater) or a boiler, depending on the temperatures and pressures achieved, and the purpose of the apparatus. However, the definition of “boiler” includes a vessel used to heat liquid broadly—that is, it applies to reservoirs, containers, and tanks wherein liquid is heated, whether or not the liquid actually boils and/or whether or not steam is generated. Further, the objective that the heated or gasified liquid will be consumed or expended either continuously or intermittently should not be read to mean that we rule out that some portion of the fluid may be recycled after the fluid has left the reservoir. And, we use the term “boiler vessel” to mean a vessel for holding a liquid which may be boiled, but need not be. Boiler vessels generally are constructed to provide for a specified liquid level or range of levels, and a free space above the liquid in which steam and vapor is contained, generally under pressure. For many purposes, it will be desirable for the boiler vessel to be a reservoir capable of handling pressures of up to 250 pounds per square inch, and desirably at least 500 pounds per square inch.
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As explained above, rapid turning of the rotor 4 will cause cavitation within the fluid, thereby elevating the temperature of the fluid, ultimately to the boiling point. Pressure and temperature regulators not shown may, at the operator's discretion, establish boiling conditions other than atmospheric. Increasing the pressure within the vessel 1 above atmospheric may beneficially affect the cavitation process by enhancing the violence of the mini-implosions taking place in the cavities, but the viscosity of the fluid and the velocity of the outer surface of the rotor are also important factors which the operator should consider. Reducing the pressure below atmospheric (as by a vacuum pump for inducing subatmospheric pressure) may help increase throughput and reduce the energy requirements of the cavitation device. Other variables of interest are the number and depth of the cavities and the flow paths of the fluid in the particular construction of the boiler vessel. Our basic invention, however, heats the fluid directly, while immersed in the vessel, without flame or heat exchange surfaces, and boils water in it for direct delivery of steam or vapor. The vessel is able to contain and handle both the hot or boiling water 20 and, in a free space above the water, steam 21.
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a is an outline perspective of a rotor useful in our invention, and
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Each of the apertures 43 may have an opening 44 leading to a radial channel 45; thus in this variation, there are six such radial channels, as there are six apertures. We do not intend to be limited to six apertures or six radial channels. Any convenient number of each may be used, and it should be understood that the apertures, or some of them, need not pass completely through the rotor 41. And, while the channels should pass from an opening near the axis of the cylindrical rotor through the interior of the rotor to exits on its cylindrical surface, they need not be oriented as radii of a circular section of the rotor—that is, they may be oriented at an angle, as will be shown in
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Therefore, it is seen that our invention comprises a reservoir including a flux stress device, which may be a cavitation device, within the reservoir, which may be a boiler vessel. The cavitation device may comprise a rotor for immersion in liquid, the rotor comprising a body having a substantially cylindrical surface and two faces, the body having a central opening on at least one face for receiving a rotatable shaft for rotating the rotor and a plurality of channels for admitting liquid when the rotor is immersed in the liquid and transporting it to the substantially cylindrical surface, and a plurality of cavities on the substantially cylindrical surface. A submersible electric motor may be used, to place the entire flux stress device, including the motor, in the reservoir. In a particular variation, our invention is a boiler apparatus comprising a substantially cylindrical vessel having a substantially cylindrical interior surface, and a substantially cylindrical cavitation rotor within the vessel, the substantially cylindrical rotor also having a substantially cylindrical surface, the cylindrical rotor surface having a diameter slightly smaller than the interior surface of the substantially cylindrical vessel, the rotor surface and the interior surface being substantially concentric. And, our invention includes a method of substantially continuously or intermittently heating an aqueous fluid comprising placing the aqueous fluid in a reservoir such as a boiler vessel and causing cavitation or other flux stress within the aqueous fluid in the reservoir, which may be substantially continuously or intermittently replenished. The reservoir may be a tank and the aqueous fluid may be an oilfield fluid such as a fracturing fluid.
