Patent Application
20180224215
This invention relates to the field of thermal energy capture, transfer, and release in applications, such as thermal treatment for enhanced oil recovery (EOR), heating underground geological deposits, recovering heat from geothermal sources, and efficiently transferring heat in multiple industrial applications. In particular, embodiments of the invention relate to systems and methods of capturing, transferring, and releasing thermal energy from intermittent sources (such as metallurgical operations), continuous sources at high temperature (such as chemical and petro-chemical operations) and continuous sources at low temperature (such as waste heat sources). A key feature of the invention is the ability to transfer heat over short or long distances with minimal heat and temperature losses. The invention also includes methods of manufacturing devices for the capture, transfer and release of heat energy, and methods to install such devices in numerous industrial applications.
In most industrial situations, heat capture involves the transfer of such energy from hot gases, liquids, or solids into other media that either conduct heat away via thermal conductivity, as is the case of heat exchangers, phase-change involving evaporation or melting, as is the case of quenching reactions, or by convection or radiation. However, in many industrial systems heat is mainly dissipated rather than captured by conduction, convection or radiation. For example, melting and quenching operations, such as the quenching of hot metallurgical coke with water, seldom capture the radiation or the steam produced, so the heat is dissipated but not captured. Most heat capture operations in industry rely on the thermal conductivity of a metal or other material that encapsulates the heat producing medium. This metal or other material subsequently transfers the heat away from its source. Therefore, a critical parameter in heat capture is the thermal barrier presented by the encapsulating material. This thermal barrier is also a critical parameter in the eventual release of heat.
When the heat is captured, methods of thermal transfer over distance normally rely on either insulated steam pipelines or the transfer of heat via thermal fluids which may include oil-based fluids, such as DowTherm®, eutectic mixtures such as molten salts, molten metals such as Na, or Pb, or Sn (these may be appropriate for metallurgical applications), or molten alloys. Steam is usually preferred in most industrial applications because it provides a considerable amount of heat upon condensation, it is often the low cost option and is easily pumped over some distance. However, heat losses in moving steam are also quite significant in spite of insulation, and so the distance over which steam can be economically transferred is necessarily limited. The same is true of thermal fluids with the aggravating feature of the additional weight and costs involved. In the case of molten salts, the entire pipeline would require replacement if the salt were allowed to “freeze” in place, a problem that has often occurred.
In addition to the above limitations and parameters, some industrial applications present unique problems to the capture, transfer, and release of heat, and deserve further discussion.
In conventional oil production, oil is recovered from oil bearing salt domes by drilling. Since the typical oil formation is under pressure, initial production is facilitated by the flow of oil to the surface under pressure. Over time, such natural flow decreases as the pressure declines, and production relies on enhanced oil recovery methods. These methods may include pressurization by injecting CO2, water flooding, or heating with steam. Steam injection has become popular, because (a) the increase in temperature caused by the steam decreases the fluid viscosity of the oil, (b) the water that condenses underground also displaces the oil while increasing underground pressure, and (c) the dual phase flow may reduce overall flow viscosity.
As conventional oil deposits are exhausted, oil production is increasingly relying on oil shales and similar formations that are generally less porous and more difficult to access. Such oil sources are generally subjected to hydraulic fracturing, otherwise known as “fracking,” where water pulses at great pressure are used to fracture underground rocks so as to enhance porosity, thus allowing the flow of hydrocarbons (natural gas or oil) to the surface. Over time, a similar decrease in the flow of hydrocarbons occurs as underground pressure declines with production, and similar EOR methods are employed: water, CO2, or steam injection. All such methods are energy intensive and costly. There is a need for EOR methods that are energy efficient and that do not require vast amounts of water for either injection or steam production.
Heat Transfer from Geothermal Fields
Unlike the case of enhanced oil recovery where the problem is to get heat down to the oil below the surface, geothermal fields have thermal energy already below the surface, and therefore heat can flow from the bottom to the top of a heat pipe or thermosyphon, while the working fluid from the top to the bottom either by gravity, through a wick, or by both. Thus, the key impediment to the use of heat pipes in geothermal applications is the distance of the heat transfer, that is, the practical length needed for the heat pipe or thermosyphon.
Most industrial applications involve operating plants where facilities are distributed in a fairly level field sometimes covering several acres and numerous production units. Thermal energy in such facilities is normally available where exothermic reactions take place, in boiler houses, furnaces, and the like, whereas thermal energy may be required at some distance from those facilities. Thus, heat transfer at industrial plants primarily involves horizontal transfer over hundreds or a few thousands of feet, but normally does not entail transfer over a significant vertical distance.
Heat pipes, with their outstanding heat flux rates due to internal mass transfer of vapor, are well suited to horizontal heat transfer because there is no significant limitation of capillary action over distance. Thus, the main practical limitation for this type of application stems from the length of commercially available heat pipes.
Embodiments of the present invention provide novel means for capturing, transferring, and subsequently releasing heat that can be applied to industrial applications, such as thermal treatment for enhanced oil recovery (EOR), heating underground geological deposits, recovering heat from geothermal sources, controlling temperature in chemical processes, capturing and reusing waste heat in plants and factories, and efficiently transferring heat in a wide variety of other industrial applications. In particular, embodiments of the invention relate to systems and methods of capturing, transferring, and releasing thermal energy from intermittent sources (such as metallurgical operations), from continuous sources at high temperature (such as chemical and petro-chemical operations), and from continuous sources at low temperature (such as waste heat sources). A key feature of the invention is the ability to transfer heat over short or long distances with minimal heat and temperature losses. The invention includes methods of manufacturing devices for the capture, transfer and release of heat energy, and methods to install such devices in numerous industrial applications. The invention allows for the rapid transfer of heat at temperatures in the range of −40° C. to 1300° C., or more, from a variety of heat sources, and the subsequent release of such heat at variable or constant temperature for a long period of time. The system includes a novel heat pipe that is thermally insulated over most of its length. In some embodiments, the low end of the temperature range can be 0, 50, 100, 150, 200, and 250 degrees. The upper end of the temperature range can be 1500 or more, 1400, 1300, 1200, 1100, 1000, 900, 800, 700, 600, 500, 400, and 300 degrees. In embodiments of the system, the dimensions of the heat pipe, the type of thermal insulation, the fabrication method, and its placement in the field are determined by the conditions and characteristics of each industrial application, by the demand of heat transfer in terms of heat release, and by the type of thermal energy available.
Some embodiments of the invention provide a heat management system that can include a plurality of heat transfer devices that can include, for example, conventional heat pipes, advanced heat pipes, thermosyphons, heat spreaders, pulsating or loop heat pipes, steam pipes, and the like, assembled into an entity providing continuous thermal communication, adapted to capture, transfer, and release heat at temperatures in the range of −40° C. to 1,300° C. at a distances of from 0.1 m to 14 km, with a temperature loss from capture to release between 0% and 40% of a temperature at a source of the heat to be transferred, wherein the heat thus can be transferred from one or more heat sources, and wherein the heat transfer devices can capture or provide heat for at least one application. In some embodiments of the invention, the distance can be from 0.3 m, 1 m, 3 m, 10 m, 30 m, 100 m, 300 m, 500 m, and 1 km to 2 km, 3 km, 4 km, 5 km, 6 km, 7 km, 8 km, 9 km, 10 km, 11 km, 12 km, 13 km, 14 km, or more Likewise, in some embodiments of the invention, the temperature loss or heat loss can be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, and 9% at a low end and 12%, 15%, 20%, 25%, 30%, 35%, or 40%, or more. Acceptable temperature loss can depend upon the circumstances of the particular use of the system. In some situations, a very low heat loss is particularly advantageous and may be required in order for a particular application to be cost-competitive. In other situations, where the competing technologies are ineffective or inoperable, a larger amount of heat loss or temperature loss can be acceptable and can be highly competitive with any alternative available. Accordingly, the desired or market-required degree of minimization of heat loss can be relative to competitive alternatives.
In other embodiments, the heat management system can include one or more heat transfer devices that can include, for example, conventional heat pipes, advanced heat pipes, thermosyphons, heat spreaders, pulsating or loop heat pipes, steam pipes, or the like, and can also include a combination of such heat transfer devices, assembled into an entity that can provide continuous thermal communication adapted to capture, transfer, and release heat at temperatures in the range of −40° C. to 1,300° C. at a distance of from 500 m to 14 km with a temperature loss from capture to release between 0% and 40% of a temperature at a source of the heat to be transferred, wherein the heat thus can be transported from one or more heat sources, and wherein the heat transfer devices can capture or provide heat for at least one application.
In other embodiments, the heat transfer devices of the system can have one or more wicks. In some embodiments, the heat transfer devices can have no wicks. In some embodiments, the heat transfer devices can include an encapsulating material manufactured from, for example, steel, copper and its alloys, titanium and its alloys, aluminum and its alloys, nickel and chromium alloys, wound metal foils, wire screens, scaffolds, and the like, or any combination thereof. In other embodiments, the heat transfer device can include different metals and alloys that can include varying thermal conductivities.
In other embodiments, the heat transfer devices of the system can include multiple sections such as, for example, evaporators, heat transfer sections, and condensers, or the like. In some embodiments, the sections can include a wick characteristic such as no wicks, full wicks, partial wicks, and the like, or any combination thereof.
In further embodiments, the application of the system can include, for example, power plants, geothermal energy production, enhanced oil recovery, gas recompression, water desalination, metallurgical processing, chemical and petrochemical operations and production, pulp and paper industries, plastic and rubber operations, refractory industry, glassmaking operations, mining operations, plywood and oriented strand board manufacturing, fermentation, fertilizer production, industrial gas production, military applications, solar energy production, rubber manufacturing, oil refineries, and the like.
In additional embodiments, the encapsulating material of the heat transfer devices can include, for example, a metal, plastic, or ceramic composition, or a composition combining such components, that can be non-reactive with respect to the variety of heat sources, non-reactive with respect to a heat transfer medium, and non-reactive with respect to the heat source.
In other embodiments, different individual wicked heat transfer devices can be joined so a joined wick structure can exist, having continuity compatible with capillary action along the length, the continuity can permit thermal communication of internal working materials throughout the length, and the internal working materials include, for example, fluids, solids that sublimate, materials having multiple chemical hydration levels, and the like, as well as any combination thereof.
In other embodiments, the wick structure can include multiple layers having different porosities. In further embodiments, the wick structure can include an internal wick structure that can include an axial wick. In other embodiments, the wick structure can include materials such as,for example, sintered metals, metal screens, grooves, oxides, borates, solids that sublimate, materials with different chemical hydration levels, nano-particles, nanopores, nanotubes, and the like.
In additional embodiments, different materials can be used at different positions along the length, and the materials can be selected to optimize heat capture and release, while minimizing heat loss.
In other embodiments, the wick can be formed, for example, by spraying, painting, baking, PVD, CVD, pyrolysis of organic compounds, or the like. In some embodiments, the wick can be formed by thermally decomposing a slurry of metal particles in a liquid metal precursor and/or by similar processes.
In some embodiments, the encapsulating tube can include a wound strip of foil or the like; the foil can be thin in some embodiments.
In additional embodiments, the wound strip structure can be pre-coated with wick material before being formed into tubular assemblies around, for example, metal scaffolds or the like that can include, for example, mesh screens.
In some embodiments, any gaps in the wound tube can be sealed by a separate wound strip or the like.
In some embodiments, the amount of working material can be in excess of what is needed to saturate the internal wick structure.
In some embodiments, the working material in the heat transfer devices can have a phase change temperature in the range of −40° C. and 1,300° C., or more.
In some embodiments, the heat transfer device can include at least one valve proximate to at least one end in order to control and maintain partial vacuum.
In some embodiments, vertical heat transfer devices of up to 14 km in length can be installed in a manner to prevent the physical degradation or breakage of the heat transfer devices. In such embodiments, the weight of the heat transfer device is neutralized by, for example, at least one buoyant balloon, at least one helicopter, a combination thereof, or the like.
In various embodiments, the heat transfer devices can be installed using at least one installation aid such as a crane, a helicopter, a balloon, a wheel, an oil rig, a tower, or the like. In some embodiments, heat transfer devices of, for example, 3-7 Km in length can be installed without physical degradation or breakage of such heat transfer devices, and the heat transfer device can be wound around a wheel of, for example, 100-500 feet in diameter that minimizes the curvature of the heat transfer device. In some embodiments, the heat transfer devices can be insulated.
In some embodiments, pulsating heat pipes can be made by encapsulating a thin metal or alloy layer in, for example, a strong metal screen or the like, to resist pressure pulses.
Some embodiments of the invention can include a method of heat capture, transfer and release using a heat management system.
Some embodiments include methods for manufacturing a heat management system that can include the steps of: selecting the type of heat transfer device from, for example, conventional heat pipes, advanced heat pipes, thermosyphons, spreader heatpipes, loop heat pipes, pulsating heat pipes, steam pipes, any such combination, or the like; selecting a method of joining heat transfer device elements from, for example, soldering, brazing, welding, threading, foil winding, mechanical fittings, encapsulating thermal fluids, any combination, or the like; selecting a type of wick structure from, for example, sintered metal, axial wick, metal screens, grooves, any combination, or the like, or no wick material; selecting the internal working material from, for example, aqueous solutions, eutectic salt mixtures, organic thermal fluids, or high-temperature metals and alloys that can liquefy at temperatures in the range of −40° C. to 1,300° C., solids that sublimate, or materials with different chemical hydration levels; and additionally the methods can include applying the joining method, wick structure, and working fluid thus selected; and sealing the heat transfer device under vacuum.
Thermal energy or heat (in common usage) represents the thermal energy of molecules, atoms or ions including kinetic, vibrational and rotational forms of energy. Heat also represents the transfer of kinetic energy from one medium or object to another, or from an energy source to a medium or object. Such energy transfer can occur in three ways: radiation, conduction, and convection but here will be used in a general common sense to include available thermal energy content. Some believe heat refers to the transfer of energy between systems (or bodies), not to energy contained within the systems, but this understanding is unnecessarily restrictive. Others define heat as the form of energy that flows between two samples of matter due to their difference in temperature, and that is also restrictive. The following definitions of heat are useful:
“Heat transfer devices” (HTDs), in the context of the current invention, include conventional and novel HP, spreader HP, thermosyphons, steam pipes, and pulsating heat pipes. When heat pipes are mentioned as the method of heat capture, transfer and release, pulsating heat and pipes spreader heat pipes can also be used. In vertical applications, thermosyphons can be used in place of heat pipes. Heat pipes are devices that can capture, transfer, and deliver heat more effectively than heat exchangers, metal surfaces, or thermal fluids because they operate on two physical principles and not just on thermal conductivity. During heat capture and release, heat pipes rely on both thermal conductivity and phase change, but the latter is several times more effective than the former, so the overall thermal performance is many times better than a comparable heat exchanger with similar surface area in the applications under discussion. Furthermore, during heat transfer, the ability of a heat pipe to transfer heat by mass transfer is, again, many times greater than the speed of thermal conductivity alone, even when dealing with highly conductive materials such as copper or silver. The superior performance of heat pipes over thermal fluids in the applications under discussion stems from the difference in specific heats of a common working fluid in heat pipe—water—versus the heat capacity of organic liquids in the case of thermal fluids.
An important feature of HTDs described in the current invention is the superior heat transfer mechanisms of the heat pipes. As shown in subsequent paragraphs, heat pipes provide a means of transferring heat that is near thermodynamically reversible, i.e., a system that transfers enthalpy with almost no losses in efficiency. Furthermore, while conventional heat pipes share these unique mechanisms, the advanced heat pipes described herein are characterized by significantly improved heat capture, transfer, and release performance and, thus, by approaching a thermodynamically reversible process even closer.
There is a need for an inexpensive heat-transfer mechanism that can readily transport heat at elevated temperature from surface operations, that can deliver such heat at constant temperature over a long period of time to underground formations, that requires little or no maintenance, that is reliable, and that requires minimal water or steam for operation.
Commercially available heat pipes come in lengths of a fraction of an inch to several feet, but not in hundreds or thousands of feet, and there is a reason for that. As explained in sections of the detailed description, below, an essential aspect of a heat pipe is its ability to circulate the condensed working fluid back to the hot area of the heat pipe. That ability is quite difficult to accomplish with current manufacturing processes, because a) capillarity forces in the current HP would not be able to lift the liquid hundreds of feet and, b) any interruption in the internal capillary action would also interrupt the internal transfer mechanism. Therefore, there is a need for long heat pipes that can be made to function effectively.
Embodiments of the invention are disclosed herein, in some cases in exemplary form or by reference to one or more Figures. However, any such disclosure of a particular embodiment is exemplary only, and is not indicative of the full scope of the invention.
Industrial heat capture entails: (a) the capture of waste and/or low-grade thermal (heat) energy, such as hot flue gases, (b) cooling of various industrial and chemical processes, such as those that include exothermic reactions, (c) controlling temperature in certain chemical or petrochemical plants, such as controlling the oxidation of propylene oxide at 200° C. during the production of propylene glycol, (d) using heat capture for delivery at remote locations, such as in enhanced oil recovery (EOR), and (e) capturing heat from difficult to access locations, such as tapping geothermal sources. Applicants review these by means of examples that illustrate the broad scope of the invention in various applications.
These industrial applications normally encompass large amounts of heat at temperatures that range from about 60° C. to perhaps as high as 250° C. which hinders the utilization of such energy for other heat consuming applications, such as additional power generation. The industries that generate large amounts of low-grade heat include but are not limited to (a) those that use large amounts of fuel and generate large amounts of flue gases, such as power plants, especially coal-fired plants, metallurgical and cement plants, and that dispose of those flue gases by means of stacks or chimneys (b) those that use industrial kilns, calcination furnaces, or process reactors, such as lime producers, alumina producers, magnesia producers, and many inorganic chemical producers (c) those that generate large amounts of heat without flue gases, such as nuclear power plants, compressors, power transformers, refractory plants, glassmaking plants, or thermal power plants with their large heat producing condensers.
Since fuel combustion constitutes a large fraction of energy generation from industry, capturing heat from flue gases becomes a relevant application for many industries. The recovery of heat from the flue gas of coal-fired power plants is selected to illustrate heat capture methods and mechanism.
Typically in a coal fired power plant, the combustion gases are first subject to catalytic denitrification by means of ammonia or amines, then ash in the flue gases is reduced by either filtration in a baghouse or electrostatic precipitation. Subsequently, the flue gases are conveyed by means of the flue duct into a fan that increases the pressure prior to flue-gas desulfurization (FGD). Following FGD, the flue gases are vented to the atmosphere by means of a stack or chimney, which is another point of potential capture for low-grade heat.
The benefits of these last two configurations—capturing heat at the baghouse or at the electrostatic precipitator—are twofold: first heat is captured at a slightly higher temperature than in the flue-gas duct thus improving thermal efficiency, and second each of these process units can be used to perform dual functions, their original function and the additional heat capture function. Note also that since with the use of HP, the electrostatic precipitator will be kept at a lower temperature than in the conventional mode and as consequence it will attract more and even finer particles driven by thermo-foretic forces thus further enhancing the filtering action.
Industrial operations that generate large amounts of heat intermittently constitute a special case. Those operations occur in such industries as integrated steel plants that utilize oxygen converters, secondary steel plants that use electric furnaces, and non-ferrous plants that produce metals like copper, lead, silicon, or titanium. The processes in these plants all generate large amounts of heat at very high temperatures but not necessarily continuously. The capture of this type of intermittently produced heat is similar to previous examples described above, but the transfer and release of such heat presents restrictions that are not found in continuous heat sources. One option is to capture heat for use in applications that also operate intermittently. Another is to store the intermittent heat in a separate vessel filled with a thermal fluid: DowTherm® or equivalent for medium to low temperatures, molten salts or eutectics for higher temperatures, or advanced heat storage systems, such as “Heat Transfer Interphase,” filed 12 Jan. 2011, with priority date of 12 Jan. 2010, and with the International Application Number of PCT/US2011/021007, and assigned to Sylvan Source, Inc, which is incorporated by reference in its entirety.
Thus, it is clear that there is a dual industrial need: (a) the need for novel heat pipes that capture, transfer, and release thermal energy over long distances, including vertical distance, and (b) the need for storing thermal energy from high-temperature sources that are intermittent. The combination of such dual features opens up multiple industrial applications that are not possible otherwise.
Numerous industrial applications require capturing heat as a means of cooling and refrigeration. Such industries include but are not limited to icemaking, brewing, underground mining, pulp and paper manufacture, food processing, beverage production, dewatering during biofuel production, and the cooling of chemical and petrochemical reactions that are exothermic such as in the production of cellulose acetate, nitrobenzene, polyvinyl-chloride resins, carbon disulfide, cumene (from alkylation of benzene with propylene), ethyl alcohol (from hydration of ethylene), formaldehyde (from methanol using exothermic reactor), phenol (from cumene peroxidation), and propylene glycol (by hydration of propylene oxide at 200° C.), acrylic resins (from catalytic oxidation of methyl methacrylate), aromatic ketone polymers (from condensation polymerization reactions), copolyester-ether elastomers, and polyacetal resins, to name a few.
Many industrial cooling operations employ double walled reactors where the outer vessel contains a circulating coolant, such as water or a thermal fluid, that takes away excess heat from the inner reactor, thus preventing run-away reactions from exothermic operations.
Cooling towers are generally used for cooling excess heat in thermal power plants and are commonly employed throughout the chemical and petrochemical industry. Cooling towers dissipate heat by evaporation and therefore, substantially contribute to water losses in an industrial operation. Heat pipes can be used for the augmentation and replacement of cooling towers because of their superior performance in capturing, transferring, and releasing heat. Thus, heat pipes can capture heat from fluids (gases or liquids) before they enter the cooling tower, thus augmenting the capacity of the cooling tower and, if sufficient heat is captured the cooling tower may be eliminated altogether.
Many chemical and petrochemical industries require precise control of operating temperature. In this invention, the means of controlling temperature are similar to those considered in
Embodiments of the invention include systems, methods, and apparatus for heating underground geological formations, such as oil deposits (e.g., enhanced oil recovery—EOR), without requiring water, CO2, or steam injection. Preferred embodiments provide a broad spectrum of heat pipes that operate within the temperature range of 120° C. and 1,300° C. or higher, and that provide for fully automated heat recovery at temperatures similar to that range over several hours, days or months without user intervention. For example, systems disclosed herein can run without user control or intervention for 1, 2, 4, 6, 8, months, or longer. In preferred embodiments, the systems can run automatically for 1, 2, 3, 4, 5, 6, 7, 8 years, or more.
Once in place, the heat pipe is ready for transferring heat from the surface to the oil formation directly without the need for pumps, external recirculation loops, or other mechanisms. Heat can be provided to the upper portion of the pipe on the surface by direct combustion of fuels (e.g., natural gas, oil), by solar heating through solar concentrators or parabolic troughs, electrical, geothermal sources, steam, waste heat at elevated temperatures, or any other type of energy source. Since heat pipes excel at axial heat transfer at rates that approach the speed of sound, the heat absorbed from surface sources rapidly reaches the oil formation where such heat is released.
An optional configuration entails using a heat pipe as described in the above paragraph together with steam injection. This allows the steam to maintain a high temperature throughout the length of the heat pipe, thus minimizing wall heat losses, while enhancing heat transfer and delivering higher temperature heat at the bottom of the heat pipe. In addition, steam condensation provides liquid water at the oil formation that enhances flow. This type of configuration can prove useful when there is a need for additional heat delivery or when the number of drill holes for EOR is limited.
In other applications, such as the recovery of heat from geothermal fields, preferred embodiments include either heat pipes, thermosyphons, loop heat pipes, or pulsating heat pipes that operate within the temperature range of 250° C. and 1,300° C. and that provide for fully automated heat recovery at temperatures similar to that range over several hours, days or months without user intervention.
Description of Heat Transfer from an Industrial Source
Other embodiments capture heat from industrial plants and transfer it to sites that can use that heat at distances of tens to hundreds to thousands of feet. These systems can operate within the temperature range of 80° C. and 1,300° C. and provide for fully automated heat recovery at temperatures similar to that range over several hours, days or months without user intervention.
The chemical process industry covers many hundreds of chemicals and petrochemicals that either utilize highly exothermic processes, require temperatures of several hundreds of degree centigrade, or produce products that must be cooled or refrigerated rapidly. Examples include but are not limited to the manufacture of acetaldehyde, acetic acid, acetic anhydride, acetone, acetonitrile, acetylene, acrylamide, acrylic acid, acrylonitrile, adipic acid, alkyl amines, alkylbenzene, ammonia, aniline, ketone polymers, benzene, benzylchloride, bisphenol A, beutanediol, butylacetate, caprolactam, carbon disulfide, cellolose acetate, cellulose ethers, chlorinated isocyanurates, chlorinated solvents, chlorobenzenes, chlorinated methanes, cresols, xylenols, cumene, cyclohexane, dimethylformamide, epichlorohydrin, epoxy resins, ethanolamines, ethyl acetate, ethanol, ethyl benzene, ethylchloride, ethylene, ethylene dichloride, ethylene amines, ethylene glycol, ethylene oxide, fluorocarbons, formaldehyde, fumaric acid, furfural, glycol ethers, Hexamethylenediamine, hydrogen cyanide, hydroquinone, isophthalic acid, isopropyl alcohol, ketene, alkylsulfonates, alphaolefins, lignosulfonates, maleic anhydride, melamine, methanol, methylethyl ketone, methyl methacrylate, nitrobenzene, Nylon resins, phenol, phenolic resins, phosgene, phthalic anhydride, polyamide resins, polyacetal resins, polyalkylene glycols, polycarbonate resins, polyesters, polyethylene, polyglycols, polyimides, polypropylene, polystyrene, polyvinyl alcohols, propionic acid, propylene glycol, propylene oxide, pyridine, silicones, sorbitol, styrene, terephthalic acid, urea, vinyl acetate, vinyl chloride, and zeolites.
Another type of industrial application involves power plants, particularly those fueled by coal. These plants generate substantial volumes of combustion gases that require progressive treatment steps to reduce pollutants. Typically nitrogen oxides (NOx) are generated during the combustion process and need to be reduced by adding ammonia or amines which reduce the NOx to nitrogen gas. Next, the fly ash particles need to be captured and removed, which is normally done with electrostatic precipitators or baghouses, or both. The flue gases also contain significant sulfur compounds from the original coal, which is normally handled in a flue gas desulfurization (FGD) system involving scrubbing. In spite of these various treatment steps, the flue gas in a coal-fired power plant contains very large amounts of low-grade heat at temperatures in the range of 330° F. to 400° F. that can be tapped without unduly affecting the normal operation of the plant.
Other examples of heat capture, transfer, and release include:
Since any type of heat pipe is exceedingly effective at heat transfer, the following section focuses on heat pipes, and how to improve their average performance so they can be applied not only to conventional applications, such as stabilizing Alaskan permafrost, but also in a variety of industrial applications including but not limited to desalination, industrial transfer of heat, cooling, refrigeration, and the like.
Clearly, heat pipes allow effective thermal transfer to be done. The heat pipes are driven by the temperature difference between their condensing and boiling ends (the ΔT) which is sufficient to maintain a very high heat flux through the heat pipe. Commercially available heat pipes transfer large amounts of heat (e.g., >200 W) and typically have ΔTs of the order of 8° C. (15° F.), or higher at higher power output, although some have ΔTs as low as 3° C. The ΔT is not critical for EOR or geothermal applications because the difference in temperature between a surface heat source and the geological formation is several hundreds of degrees, but a low ΔT is generally desirable to optimize overall thermal efficiency. It is therefore useful to examine the thermal phenomena in a heat pipe. Insert working fluid here (92)
An important factor in maintaining a low ΔT is limiting the wall heat losses, which are a function of the surface area (and thus on the length) of the pipe and the thermal conductivity of the wall material and the media surrounding the HP. This need is not critical for normal HP pipes but is important for very long HP as claimed in this application.
An improvement in the ability to capture heat is the use of metal oxides and/or pigments that are dark or black and that absorb heat more readily, particularly in the case of radiation heat. One advantage of a heat pipe having a black exterior coating is that such black surface also excels in radiating heat at the cold end of the heat pipe.
Experimentally, the largest barriers to heat transfer in a heat pipe include: first the layer immediately adjacent to the outside of the heat pipe (the boundary layer), second the conduction barrier presented by the material of the heat pipe, and third, the limitation of the wick material to return working fluid to the hot end of the heat pipe. However, in EOR applications, the boundary layer adjacent to the exterior of the heat pipe is minimal for two reasons: first, because if direct heating is used or steam or pressurized hot water are not used, the thermal barrier becomes far less significant, and second because, on the oil formation side, any water tends to be quite saline which can readily collapse the molecular double layer responsible for most of the barrier.
In
During operation, heat enters near the top and traverses the thin metal foil (10). The thinness of the metal foil facilitates heat transfer because thermal conductivity is an inverse function of the thickness of the material through which heat must travel. Upon reaching the internal wick (12), heat rapidly evaporates the working fluid that is present in the wick. The saturated vapor travels rapidly through the internal volume of the heat pipe and reaches the opposite end of the pipe where the slightly lower temperature causes the condensation of the vapor back into the working fluid. In the process, the heat of vaporization has been transferred from the top of the heat pipe to the bottom. The condensed working fluid then flows by capillary action toward the hot end of the pipe through both the surface wick (12) and the central axial wick (14), thus providing the necessary volume of flow for maintaining a large heat transfer.
Internal wick materials include sintered copper spheres, metal groves, metal screens, and other materials that contain a well-defined porosity.
The composition of the working fluid inside a heat pipe generally determines the temperature range of the heat pipe or thermosyphon. Low temperatures involve organic compounds such as ammonia, alcohols, ketones, aldehydes, or aromatic hydrocarbons that boil at temperatures lower than ordinary water or aqueous solutions. For high-temperature ranges, certain metals like sodium, potassium, magnesium, aluminum, lead, zinc, and their alloys provide working fluids that can work at temperatures in excess of 1300° C. Another option is to use salts and mixtures of salt that sublimate as a working fluid for both, high and low temperature heat pipes. Also included are metal oxides, borates having different hydration levels.
Once the tubular scaffold is formed, it is inserted into a furnace (19) that can sinter or weld the finished surface of the heat pipe which is allowed to rotate, as shown in the diagram of
An alternative method for manufacturing a suitable wick is by using a copper or other metal precursor. A metal precursor is a chemical substance that upon heating decomposes into a metal. In the case of sintered copper wicks, the precursor can be copper beta diketonate (CBDK) or copper acetylacetonate (CAA), both of which decompose into micron-sized copper particles upon heating in a reducing atmosphere. In general any organic precursor that can be decomposed, or any ionic precursor that can be electrodeposited can be candidates. A suitable wick can be made by slurrying micron-sized copper particles in CBDK or CAA and spreading the slurry into the inside surface of a copper tube or copper strip. The excess liquid is drained away, so the solid metal particles are subsequently held by surface tension of the funicular rings that form in the contact points of the metal particles. Upon heating in a reducing atmosphere, the CBDK or the CAA decomposes into copper that welds into the contact points of the metal particles, thus cementing them in place. Alternatively, providing a suitable electro-potential, Cu ions can be deposited to provide the desired glue. Numerous metal precursors are available for decomposition into different metals, and normal thermal diffusion will allow such precursors to cement similar and dissimilar metals, as long as the metallic particles and the precursor metal have some solubility with each other. For example, deposition of CU on Cu or Sn on Cu can both provide the good thermal contact via Cu or CuSn alloys bridges.
Following the installation of the axial wick, which is optional but desirable in a long heat pipe, the working fluid is inserted so it can saturate the inner surface of the wick and the volume of the axial wick. The volume of working fluid can be 0% to 25% higher than required for wick saturation, and in cases where the evaporated working fluid can become superheated in its vapor form, the excess working fluid can exceed 25%.
A potential problem may arise with the wick structure in very long vertical heat pipes because of the need to maintain capillary action against the forces of gravity. The height of a capillary rise, h, is defined by:
where γ is the liquid-air surface tension (force/unit length), θ is the contact angle, ρ is the density of liquid (mass/volume), g is local acceleration due to gravity (length/square of time[26]), and r is radius of tube.
For a water-filled glass tube in air at standard laboratory conditions, γ=0.0728 N/m at 20° C., θ=0° (cos(0)=1), ρ is 1000 kg/m3, and g=9.81 m/s2. For these values, the height of the water column is
Thus for r=0.0002 m (0.2 mm), h=0.074 m, and for r=0.000002 m (2 micron), h=7.4 m, and for r=0.000000002 m (2 nm), h=7,400 m. However, in actual industrial practice laboratory conditions do not necessarily apply: the value of surface tension normally decreases with temperature and the contact angle is rarely 0°, although by keeping the wick surface clean and using working fluids that are aqueous such values can be approached. The largest factor in maintaining capillary action, however, remains the radius of the capillary. Therefore, the wick pore size in very long heat pipes needs to be in the range of several nanometers and not in the micron range as it is normal for conventional HP. However, this is not a problem encountered with pulsating heat pipes or thermosyphons that do not have wick structures. The practical implication in terms of manufacturability suggests sintered wicks made of nano-particles or the use of nanotubes or nano-sized structured powders or films of similar size.
The final stages in making a heat pipe involve evacuating it by applying vacuum, and sealing it by crimping or welding.
Once the wick material has been formed onto the foil, a number of metallic scaffolds (13) can be placed between the two thin foils (35), so as to form separate cylindrical surfaces separated by flat foil surfaces, as illustrated in
What distinguishes the present invention from conventional pulsating heat pipes is that the heat pipe can be manufactured according to the principles noted in the previous discussion regarding long-distance heat pipes in
Effective heat transfer that occurs without significant temperature loss is also attractive for thermal power plants that have substantial volumes of waste heat available, but at temperatures that are normally too low for various industrial applications. However, a novel technology has been developed by Sylvan Source, Inc, (U.S. Pat. No. 8,771,477, and patent application No PCT/US2012/054221, with international filing date of 7 Sep. 2012, and priority date of 9 Sep. 2011, incorporated herein by reference in its entirety) that can purify a broad range of contaminated waters using very little heat energy, and that technology can be combined with heat capture to provide useful heat capture with water purification.
However, for such innovation to be effective the capture of heat, its transport to where it can be used, and its subsequent delivery must take effect with a minimum of temperature loses. Heat pipes, thermosyphons, and pulsating heat pipes provide a practical solution, provided that the heat pipe system can fulfill all three functions simultaneously and without intermediate steps. Thus, there is a need for long-distance heat pipes that can capture low-grade as well as higher temperature heat, transfer such heat energy to a larger diameter heat pipe with no temperature loss, and deliver such heat energy to a number of smaller diameter heat pipes for actual utilization, again not suffering significant temperature loss. One way in which this can be accomplished is by having a number of smaller diameter heat pipes (4) seamlessly connected to a larger diameter heat pipe (58), and in turn connected to a heat delivery system consisting of smaller diameter heat pipes (4), as illustrated in
Clearly, for a complex heat pipe to function as a single unit it is essential that the mechanism for returning the working fluid to the hot end of the heat pipe must not be interrupted. That means that the internal wick that functions by capillary action must be inter-connected throughout the various joints between the heat pipe elements. Since joining metallic heat pipes would normally be accomplished by welding the external encapsulating material and such welding cannot be used to join the sintered wick, the question becomes “how to provide for capillary continuity” when joining dissimilar heat pipes.
Another important feature of an advanced heat pipe, particularly one that integrates several small diameter and large diameter heat pipes, is the ability to stop the transfer of heat at will, such as in industrial situations where the main plant must be disconnected from the heat transfer mechanism.
An optional configuration of advanced heat pipes includes hybrids of heat pipes with pulsating heat pipes and/or loop heat pipes that combine the best features of each type of heat pipe into a single entity with superior performance. For example, a combination of a pulsating heat pipe can provide for optimum heat capture and release, while a standard or loop heat pipe that is an integral element provides for optimum heat transfer. Such a hybrid can include thin wall thickness at the heat capture and release ends, and thicker walls with or without thermal insulation to prevent long-distance losses, and a common wick material that ensures continuous fluid communication inside the hybrid pipe due to capillary action. Furthermore, the capillary wick can consist of an axial or spirally wound wick that periodically touches the internal wall, thus maintaining capillary continuity throughout the length of the heat pipe. Such flexible wick can be used to join different heat pipes prior to welding, thus also maintaining capillary continuity. Alternatively, the wick material can be grooved for the long-distance section of the heat pipe, thus providing for different wick structures that optimize each function of the heat pipe: heat capture, transfer, and release. Another option involves the use of metallic screens that can weld onto slightly larger or smaller diameter screens that provide for capillarity.
The release of heat involves the same principles as the capture of heat, except that in the case of heat pipes, particularly in conventional heat pipes, the execution of those principles are in the reverse order. Thus, releasing heat from a conventional heat pipe involves first the condensation of the internal vapor at the cold end of the heat pipe, then the transfer of that heat via thermal conductivity through the wick material and subsequently through the encapsulating tube which is normally a metal or alloy, and ultimately the dissipation of that heat to the medium outside the heat pipe. In the case of advanced heat pipes which may contain multiple wick layers of different porosities, the thermal conductivity will depend on the thickness of each wick layer and the thermal conductance of the wick material. In the case of pulsating heat pipes and thermosyphons, when there is no wick, the thermal conductivity through the encapsulating tube will depend on whether the internal fluid is in liquid or gaseous form, as well as the thermal conductance of the tube and its thickness.
The numerous possible configurations described in the previous paragraphs have distinct advantages for releasing heat efficiently, such as:
The ability of capturing, transferring, and releasing heat more efficiently than heat exchangers, or the so called “economizers” that rely of thermal fluids, or quenching operations based on water sprays confers distinct advantages to the heat pipes described in previous paragraphs in multiple industrial applications, such as:
One skilled in the art will appreciate that these methods and devices are and may be adapted to carry out the objects and obtain the ends and advantages mentioned, as well as various other advantages and benefits. The methods, procedures, and devices described herein are presently representative of preferred embodiments and are exemplary and are not intended as limitations on the scope of the invention. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the disclosure. For example, an inner wick can be sprinkled inside the pipe tube and subsequently sintered at the appropriate temperature, which depends on the sintered material.
All patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference.
The invention illustratively described herein suitably can be practiced in the abs of any element or elements, limitation or limitations which is/are not specifically disclosed herein. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions indicates the exclusion of equivalents of the features shown and described or portions thereof. It is recognized that various modifications are possible within the scope of the invention disclosed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the disclosure.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US15/46737 | 8/25/2015 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62041556 | Aug 2014 | US |
