Refrigeration – Refrigeration producer – Sorbent type
Reexamination Certificate
2001-10-22
2003-08-05
Jones, Melvin (Department: 3744)
Refrigeration
Refrigeration producer
Sorbent type
Reexamination Certificate
active
06601405
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a generator for an absorption cooling system. More particularly, the present invention relates to fluid flow patterns in a direct-fired generator of an absorption chiller.
2. Description of Related Art
Typical absorption chillers have a refrigerant or working fluid consisting of at least a two-part solution, such as a solution of lithium bromide and water or ammonia and water. Varying the solution's concentration by cyclically vaporizing and reabsorbing of the solution's two components allows for the use of a pump or multiple pumps to circulate the solution through the chiller to create a cooling effect.
In operation, one or more so-called generators add heat the solution to raise its absolute pressure and to vaporize one solution part. The vaporized part will be referred to hereinbelow as a weak or less concentrated solution and for a solution of lithium bromide and water, the term “weak solution” refers to pure or nearly pure water which may be found in a liquid or vaporous state downstream of the generator. For systems using a solution of ammonia and water, the weak solution is pure or nearly pure ammonia. The unvaporized portion of the solution in the generator is referred to as a more concentrated or strong solution.
Weak solution flows from the generator of an absorption chiller to a condenser where it is cooled and condensed to liquid form. From the condenser, the solution flows to and functions as a refrigerant within a relatively lower-pressure evaporator component. The lower pressure found in the evaporator causes the solution to expand. That expansion further lowers the solution's temperature and permits that solution to be used as a refrigerant to cool still another liquid, most typically water. That cooled liquid is then used as needed, such as to cool rooms or other areas of a building or in an industrial process application.
After performing its cooling function in the evaporator and vaporizing in the process, the weak solution migrates, in vaporous form, to the absorber component where it is reabsorbed resulting in the creation of a liquid solution of intermediate concentration. That solution is delivered to the generator component to repeat and gain the effect of the solution separation process.
A generator is referred to as being direct-fired if its source of heat is from direct combustion instead of from steam or waste heat delivered to the chiller from another process and/or location. In direct-fired generators, hot combustion gas is typically directed across the exterior of a tube set through which solution of intermediate concentration flows so as to heat the solution and cause the vaporization of a portion of it.
The heating of solution in a direct-fired generator often involves multiple passes of combustion gas across the tube set so as to extract as much heat from the combustion gas as possible. While efficient in that regard, multi-pass designs typically add significantly to the cost and complexity of a generator for the reason that such designs generally have more parts including, but not limited to, a turn box which redirects the flow of combustion gas from one pass across the tube set to another.
In so-called single-pass direct-fired generator designs, combustion gas makes only one pass across the tube set. In such designs, an outer shell often surrounds an inner combustion chamber. Combustion gas heats some of the solution as it travels vertically upward through the tube set and heats the rest of the solution as it travels upward between the inner and outer shells of the generator.
In practice, it can be very challenging to manufacture shell-within-shell units. Further, once the shells are assembled and welded together, it can be very difficult to find and repair any leaks between the two that might exist. Even a slight leak can dramatically affect an absorption chiller, not only from a performance standpoint, but from a reliability standpoint. In that regard, the leakage of air into an absorption chiller can lead to rapid and extensive corrosion inside the unit.
Other concerns with existing single-pass generator designs exist. For example, rapid upward flow and discharge of solution from the vertical tubes or from between the sides of inner and outer generator shells in such designs can create a geyser-like effect at the surface of the solution pool which is found just above the combustion chamber. Such disruption of the solution pool surface tends to cause the vaporous solution above that pool surface to entrain and carry liquid out of the generator and into the system condenser, evaporator, and, eventually, absorber. Any such liquid carryover reduces an absorption chiller's capacity.
The need continues to exist for a readily manufacturable single-pass direct-fired generator for an absorption chiller wherein the generator can be leak tested before final assembly and in which provision is made to minimize the carryover of liquid entrained in the vapor that flows out of the generator's interior.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an absorption chiller with a single-pass, direct-fired generator the inner shell of which can be fabricated and completely leak checked before fabricating the outer shell.
Yet another object of the present invention is to apportion liquid solution flow within a direct-fired generator between a first path, through the generator's tube bundle, and a second path, which bypasses the tube bundle, such that most of the heat transfer between combustion gas and solution occurs within the tube bundle.
A further object of the present invention is to provide a direct-fired generator having an inner shell in which less than half of the shell volume is taken up by a tube bundle.
A still further object of the present invention is to provide a single-pass, direct-fired generator with a vapor separator situated an appreciable distance away from the location of liquid solution discharged from the generator's tube bundle.
Yet another object of the present invention is to provide a vapor separator for a direct-fired generator having a geometry which inhibits the entry of liquid solution into the interior thereof yet out of which any liquid solution that does enter may readily drain.
Another object of the present invention is to provide a vapor separator for a direct-fired generator having flow deflectors that direct vapor-entrained liquid droplets away from the generator's vapor outlet and which assist in creating a vapor flow pattern that facilitates liquid disentrainment during the course of vapor flow therethrough.
Another object of the present invention is to provide a single-pass, direct-fired generator whose combustion gas inlet and vapor outlet are found in a common end plate.
These and other objects of the present invention are provided by a direct-fired generator for an absorption chiller that includes inner and outer shells having lower, generally U-shaped half-shells welded to inverted, generally U-shaped upper half-shells. The inner shell defines a combustion chamber and supports a tube bundle such that the combustion gas makes a single pass across the tube bundle. The majority of liquid solution flow within the generator is vertically upward through the tube bundle while a lesser liquid portion flows between the shells. A vapor separator is disclosed and is disposed within the generator so as to significantly limit the carryover of liquid solution out of the generator.
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patent: 6279343 (2001
Cosby, II Ronald M.
Harms Jeffrey D.
Stewart Gordon C.
American Standard Inc.
Beres William J.
O'Driscoll William
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