Compositions – Frost-preventing – ice-thawing – thermostatic – thermophoric,...
Reexamination Certificate
2000-11-22
2002-08-13
Green, Anthony (Department: 1755)
Compositions
Frost-preventing, ice-thawing, thermostatic, thermophoric,...
C252S071000, C165S010000, C165S104150, C165S104190
Reexamination Certificate
active
06432320
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to additives for heat transfer media and refrigerants, and in particular to the use of stabilized nano-particle size metal powders to enhance the thermal capacity and thermal conductivity of refrigerant and heat transfer media.
2. Description of the Prior Art
Heat transfer media have applications in both heating and cooling, including refrigeration, air conditioning, computer processors, thermal storage systems, heating pipes, fuel cells, and hot water and steam systems. Heat transfer media include a wide range of liquid or phase change materials, including water, aqueous brines, alcohols, glycols, ammonia, hydrocarbons, ethers, and various halogen derivatives of these materials, such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and the like. These have been used alone or in combination with additives, such as refrigerant oil additives for lubrication and composites of fluids to affect boiling or freezing temperature. Such media are used to transfer heat from one body to another, typically from a heat source (e.g., an vehicle engine, boiler, computer chip, or refrigerator), to a heat sink, to effect cooling of the heat source, heating of the heat sink, or to remove unwanted heat generated by the heat source. The heat transfer medium provides a thermal path between the heat source and the heat sink, and may be circulated through a loop system or other flow system to improve heat flow.
Several criteria have been used for selecting heat transfer media for specific applications. Exemplary criteria include the influence of temperature on heat transfer capacity and viscosity, and the energy required to pump the medium through a heat transfer system. Specific parameters describing the comparative performance of a heat transfer medium are density, thermal conductivity, specific heat, and kinematic viscosity. The maximization of the heat transfer capability of any heat transfer system is important to the overall energy efficiency, material resource minimization, and system costs. There are numerous improvements in heat transfer systems that are further enhanced by increased thermal capacity. One example is the utilization of secondary loop or multiple stage refrigeration systems. A secondary loop refrigeration system is more compact in design, has a reduced charge of refrigerant, requires a reduced system horsepower, and has lower implementation costs.
Other factors that affect the feasibility and performance of heat transfer media include environmental impact, toxicity, flammability, physical state at normal operating temperature, and corrosive nature.
A variety of liquids can be use d as heat transfer media in systems where heat transfer efficiency is to be maximized and fluid transport energy minimized. Such media can benefit from enhanced thermal conductivity. The heat transfer media may include a filler material that is thermally conductive to enhance the thermal conductivity of the heat transfer medium. Nanoparticle size copper oxide has been used in a water heat transfer fluid in a secondary loop. However, high surface area metal powders in an aqueous environment tend to experience corrosion, even so-called inert metals.
The present invention provides a new and improved additive for heat transfer media and method of use.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a heat transfer composition is provided. The composition includes a heat transfer medium, and an additive comprising a powder, the powder having a corrosion inhibitive coating or dispersion enhancing coating thereon.
In accordance with another aspect of the present invention, an additive for a heat transfer medium is provided. The additive includes a nano-particle size powder formed from one of the group consisting of a metal, an alloy, a metal compound, and carbon, the powder being chemically stabilized with an azole.
In accordance with another aspect of the present invention, a process for transferring heat between a heat source and a heat sink is provided. The process includes transferring heat between the heat source and the heat sink with a heat transfer composition which includes a powder. The powder has a surface thereof coated with a chemical agent which provides the powder with improved corrosion resistance or dispersion characteristics as compared with an uncoated powder.
As used herein, the term heat transfer is used to imply the transfer of heat from a heat source to a heat sink, and applies to both heating and cooling (e.g., refrigeration) systems.
The term “primary loop” refers to the heat transfer method used in a primary refrigeration system, boiler system, or any other system that is directly affected by an energy transfer mechanism. This includes a compressor in a refrigeration system, combustion source in a boiler system, or a heat transfer fluid in an absorption system.
The term “secondary loop” refers to the path over which a heat transfer medium travels while it is being cycled between a heat source and a primary system, boiler system, or any other system that is indirectly affected by an energy transfer mechanism. This includes a shell and tube or plate heat exchanger in a refrigeration system or in a boiler system. The loop refers to the path over which the heat transfer medium travels while it is being cycled between the heat source and the primary system. Thus, for example, a secondary loop refrigeration system uses a heat transfer medium to transport energy from a heat source to a primary refrigeration system.
The term “heat transfer fluid,” or “heat transfer medium,” as used herein, includes liquids, viscous materials, vapor and gaseous heat transfer materials which flow at the operating temperature of a heat transfer system, and includes materials which may be solid at room temperature, but that are flowable at the operating temperature of the system.
The term “nano-sized particle,” or similar terms, as used herein, includes particles which have an average size of up to 2000 nm.
One advantage of the present invention is that the thermal conductivity, thermal capacity, and energy efficiency of a host heat transfer medium are increased.
Another advantage of the present invention is that pump energy requirements may be reduced.
Yet another advantage of the present invention is that the additive is readily dispersed in the heat transfer medium.
A further advantage of the present invention derives from stabilization and passivation of the additive, enabling direct immersion into corrosive environments.
A yet further advantage of the invention is that the additive may maintain a mobile colloidal dispersion within the heat transfer fluid, enabling the additive to be utilized without the use of dispersion enhancement devices in a host heat transfer system.
A still further advantage of the present invention is that effects on the boiling and freezing temperatures of the host heat transfer fluid are minimized.
Other advantages of the present invention derive from the enhanced thermal capacity of the heat transfer composition, which results in energy consumption reductions by reducing the incoming fluid temperature (in a cooling system) needed to achieve a targeted fluid leaving temperature. Reductions in fluid velocities may also be achieved, thereby reducing friction losses and pressure losses within a circulation pump.
A further advantage of the present invention is that by enabling stabilizing pure metals or their alloys to be used in a heat transfer system, heat transfer compositions with higher thermal transfer properties may be achieved as compared with compositions using oxidized forms of the metals or alloys.
Yet another advantage of the present invention is that the heat transfer additive is compatible with a wide range of heat transfer media, including, but not limited to media for applications ranging from engine cooling, heating, air conditioning, refrigeration, thermal storage, and in heat pipes, fuel cells, battery systems, hot water and steam sys
Bonsignore Patrick
Gurin Michael H.
Fay Sharpe Fagan Minnich & McKee LLP
Green Anthony
LandOfFree
Refrigerant and heat transfer fluid additive does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Refrigerant and heat transfer fluid additive, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Refrigerant and heat transfer fluid additive will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2882934