Refrigeration – Processes – Accumulating holdover ice in situ
Reexamination Certificate
1999-06-15
2001-04-17
Doerrler, William (Department: 3744)
Refrigeration
Processes
Accumulating holdover ice in situ
C062S064000, C062S135000, C062S373000, C062S434000, C165S171000
Reexamination Certificate
active
06216469
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to devices and processes for cooling objects in a tank containing a chilled agent, and more particularly to those for quick chilling products such as perishable food and medical products.
BACKGROUND OF THE INVENTION
A number of different systems and methods for quickly chilling food, beverages, and other goods are in commercial use today. Chilling devices include those with refrigerant coils which directly chill liquid water to a set temperature which is then circulated in a tank to chill product, ice builders which harvest ice to chill water which is then pumped into a separate chill tank; slush ice builders where the slush formed is pumped into a separate chill tank; antifreeze systems using chilling agents such as brines, glycols or eutectic salts in a direct chill system; and air chill systems where the product is either chilled or frozen by contact with high-volume cold air.
Chilling or cooling systems using antifreeze, eutectics, brines, glycol and other additives have inherent sanitation and corrosion problems. Use of such additives which may be toxic is inappropriate for direct contact with food products. Disposal of tank fluids containing such chemicals can also create environmental problems and additional expense for proper disposal.
Thermal energy storage (or cool storage) is a process by which heat is extracted from a thermal reservoir (e.g., a chilling agent, such as water, to form frozen chilling agent or a slurry of frozen and liquid chilling agent, such as ice or slush) at one time, and at a later time to use the thermal reservoir (e.g., the ice or slush) to extract heat from an environment. Ice-building and harvesting systems are used to provide chilled water for air conditioning of buildings. Ice is built on refrigerator coils and later harvested into a separate storage tank to chill water that is then available for cooling. A significant benefit of such systems is their use of off-period ice building to reduce power costs. Typically, ice harvesting is done in these systems by application of external mechanically or thermal energy decreasing the overall efficiency of the cooling process. Exemplary systems using thermal energy storage for building air conditioning are discussed in U.S. Pat. Nos. 4,656,836; 4,928,493; and 5,168,724.
External ice builders (e.g., not within the chill tank) with heat exchangers are in common use in food manufacture and commissary kitchens. Ice is built on refrigerator coils and harvested to chill water. External energy is most often added to harvest the ice. In many applications, water chilled in the external ice builder is pumped at high volume into a chill tank containing product to be chilled. The product may be contained in bags or similar individual container which may be tumbled or agitated mechanically to speed chilling. Tumblers are expensive to build and can be dangerous for those personnel who operate, clean, load and unload them. Chill times can be relatively long in such systems (up to several hours) at least in part because the temperature of the near-freezing water in the ice builder is typically several degrees higher in temperature after it is transferred to the chill tank for cooling the product. Furthermore, the capacity of chilled water to remove heat with concomitant temperature rise is only a small fraction of that of an equal volume of ice to remove heat with concomitant melting of the ice. Additionally, while refrigeration units are typically light enough to be placed on the roof of a building to conserve floor space, ice builders with a water/ice storage tanks are generally too heavy to put on a roof of a building and thus can require allocation of more floor space or ground space than a chill tank alone. Further, it is more efficient and less costly to run refrigerant supply and return lines than it is to run supply and return lines for high volumes of liquid chilling agent or slush. The distance that chilling agent or slush is transported is a limiting factor on system efficiency.
In slush ice chilling systems, slush ice is made in a separate tank and either scraped off mechanically or removed by running high-pressure water through polished large diameter tubes and then transported to a chill tank. Slush ice systems consume energy in harvesting and transferring the slush ice to chill the product. Solid ice is generally preferred to slush for storage of cooling thermal energy, because slush ice has a significantly lower latent heat of fusion than an equal volume of solid ice.
All of these systems for chilling goods introduce energy needlessly, waste space, or create other avoidable expenses. The present invention is directed to a quick chilling device that employs thermal energy storage to improve chilling efficiency and speed, but avoids additional energy input to harvest ice or slush.
SUMMARY OF THE INVENTION
The present invention provides devices and methods for rapid chilling of various products, articles and devices, including both perishable and non-perishable goods. In preferred, embodiments the invention relates to rapid chilling of products that include, among others, foodstuffs, medicinals, blood products, and other perishable goods. Embodiments of this invention include rapid chilling devices for products which are detrimentally affected by freezing. These devices and methods store thermal energy by ice and/or slush formation and employ the heat of the product to be chilled to perform useful work, i.e., to help harvest the ice. Solid ice harvesting generally occurs any time a warm or hot product is introduced into the device of this invention. Harvesting allows a higher volume of the water to freeze, expands cooling capacity and generally accelerates cooling by enhancing the thermal and radiative conduction between the liquid chilling agent and the working surface and the refrigerant and the chilling agent. Congested facilities (e.g., restaurants, hospitals, or blood banks) needing high-volume chilling of a perishable product will benefit especially from the present invention. The combination of the chilling device of this invention with a remote refrigeration unit, e.g., a refrigeration compressor on the building roof, results in a particularly space-efficient quick chilling device.
The devices and methods of this invention which typically cool with a mixture of liquid and frozen chilling agent (water and ice) provide more rapid chilling than conventional quick chill devices that cool with chilled liquid chilling agent alone.
More generally, the inventive chilling devices have a chill tank containing a freezable liquid chilling agent (preferably water and more preferably potable water) for thermal storage and transfer, a heat exchanger, comprising a thermally conductive layer, submerged, surrounded and in contact with the liquid chilling agent, a selectively controlled source of refrigerant to the heat exchanger, and a control system for controlling the introduction of refrigerant into the heat exchangers. Warm or hot product is directly inserted into the chill tank in contact with the liquid chilling agent. Refrigerant provided by any standard refrigeration unit or plant to the heat exchanger chills the liquid chilling agent and ultimately a mass of frozen chilling agent forms on surfaces of the heat exchanger. The heat exchanger surface at which the frozen layer forms is designated the working surface. An important feature of this invention is that the heat exchanger comprises two surfaces: a working surface for building frozen coolant and a heat-absorbing surface which always remains free of frozen chilling agent (e.g., that remain ice-free). The working surface is substantially in direct thermal and/or close radiative contact with the refrigerant and the heat-absorbing surface is, in turn, in direct thermal and/or close radiative contact with the working surface, but is only indirectly in thermal and radiative contact with the refrigerant. The heat-absorbing surface is kept free of frozen chilling agent to facilitate absorption of heat g
Doerrler William
Greenlee Winner & Sullivan, P.C.
Miller Bruce
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