Heat exchange – Flow passages for two confined fluids
Reexamination Certificate
2001-04-24
2002-05-14
Flanigan, Allen (Department: 3743)
Heat exchange
Flow passages for two confined fluids
C165S175000, C062S513000
Reexamination Certificate
active
06386277
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a headering system for heat exchangers, and more particularly, to a headering system for a suction line heat exchanger for use in refrigeration systems.
BACKGROUND OF THE INVENTION
As is well known, discharge of refrigerants into the atmosphere is considered to be a major cause of the degradation of the ozone layer. While refrigerants such as HFC's are certainly more environmentally friendly than refrigerants such as CFC's which they replaced, they nonetheless are undesirable in that they may contribute to the so-called greenhouse effect.
Both CFC's and HFC's have been used largely in vehicular applications where weight and bulk are substantial concerns. If a heat exchanger in an automotive air conditioning system is too heavy, fuel economy of the vehicle will suffer. Similarly, if it is too bulky, not only may a weight penalty be involved, but the size of the heat exchanger may inhibit the designer of the vehicle in achieving an aerodynamically “slippery” design that would also improve fuel economy.
Much refrigerant leakage to the atmosphere occurs from vehicular air-conditioning systems because the compressor cannot be hermetically sealed as in stationary systems, typically requiring rotary power via a belt or the like from the engine of the vehicle. Consequently, it would be desirable to provide a refrigeration system for use in vehicular applications wherein any refrigerant that escapes to the atmosphere would not be as potentially damaging to the environment and wherein system components remain small and lightweight so as to not have adverse consequences on fuel economy.
These concerns have led to consideration of transcritical CO
2
systems for potential use in vehicular applications. For one, the CO
2
utilized as a refrigerant in such systems could be claimed from the atmosphere at the outset with the result that if it were to leak from the system in which it was used back to the atmosphere, there would be no net increase in atmospheric CO
2
content. Moreover, while CO
2
is undesirable from the standpoint of the greenhouse effect, it does not affect the ozone layer and would not cause an increase in the greenhouse effect since there would be no net increase in atmospheric CO
2
as a result of leakage.
Such systems, however, require the use of a suction line heat exchanger to increase the refrigerating effect of the evaporator due to thermodynamic property relationships. If not used, an unusually high mass-flow rate of CO
2
and correspondingly high compressor input power levels are required to meet typical loads found in automotive air conditioning systems. Through the use of a suction line heat exchanger, the CO
2
mass-flow rate and compressor input power may be lowered with the expectation that a reduction in the size of the system compressor may be achieved. At the same time, the addition of a suction line heat exchanger to the vehicle has the potential for increasing weight as well as to consume more of the already limited space in the engine compartment of a typical vehicle. Thus, there is real need for a highly compact suction line heat exchanger.
Heretofore, suction line heat exchangers have been utilized only in relatively large refrigeration systems where the refrigerant, including conventional Freons discharged from the evaporator must be passed as a super-heated vapor to the compressor to assure that no liquid enters the compressor. This is necessary as compressors conventionally employed in refrigeration systems are positive displacement devices. As such, if any liquid refrigerant, coexisting within gaseous refrigerant in a saturated state, were drawn into the compressor, severe damage would be likely to result.
Suction line heat exchangers avoid the difficulty by bringing relatively hot, condensed refrigerant from the outlet of the system condenser or gas cooler into heat exchange relation with the refrigerant being discharged from the evaporator at a location between the evaporator and the compressor. As a consequence, the refrigerant stream exiting the evaporator will be heated. The suction line heat exchanger is sized so that the stream ultimately passed to the compressor from the suction line heat exchanger is a super-heated vapor at a temperature typically several degrees above the saturation temperature of the refrigerant at the pressure at that point in the system. Thus, no refrigerant will be in the liquid phase and the compressor will receive only a gaseous refrigerant. A typical system of this sort is shown schematically in FIG.
1
.
Over the years, various counter-flow or cross-flow types of heat exchangers have been employed in any of a variety of heat exchange operations. One type of counter-flow heat exchanger employs generally concentric tubes with one heat exchange fluid flowing in the inner tube in a given direction and the other heat exchange fluid flowing in a space between the inner tube and the inner wall of the outer tube and in the opposite direction. Another type of counter-flow heat exchanger includes flexible tubing wound in a continuous length on a conduit with header fittings applied to either end.
While these constructions work well for their intended purposes, the use of concentric tubes requires headering systems which are generally labor intensive in terms of fabrication and assembly such that the product is expensive.
The present invention is directed to overcoming one or more of the above problems.
SUMMARY OF THE INVENTION
It is the principal object of the invention to provide a new and improved header construction for a heat exchanger. More specifically, it is an object of the invention to provide a header system allowing fabrication of a heat exchanger that is compact, highly efficient, and of simple construction.
An exemplary embodiment of the invention achieves the foregoing objects in a heat exchanger comprising an elongated tube structure including at least three flow conduits, each having multiple ports and with a first and third flow conduit sandwiching a second flow conduit and in heat exchange relation therewith, the second conduit being shorter than the first and third conduits and having second conduit opposite ends, at least one of the second conduit opposite ends provided with a second conduit inlet/outlet fitting. The first and third conduits each have parts extending past at least one of the second conduit opposite ends to opposite sides of and around the second conduit inlet/outlet fitting to terminate in first and third conduit opposite ends, with corresponding ones of the first and third conduit opposite ends being adjacent to one another and at least one first and third conduit inlet/outlet fitting connected to both the adjacent corresponding ones of said first and third conduit opposite ends.
In a preferred embodiment each of the conduits is formed of an individual piece of tubing having flat sidewalls, the pieces being assembled with their sidewalls in abutment and bonded together in heat exchange relation.
In a preferred embodiment the parts of the first and first and third conduits are generally concave about the at least one second conduit inlet/outlet fitting and terminate in the first and third conduit opposite ends.
In a preferred embodiment two first and third conduit inlet/outlet fittings each connect to the adjacent corresponding ones of the first and third conduit opposite ends.
Preferably the first and third conduits each have an arc shaped portion extending about the second row inlet/outlet fittings and converging with corresponding ones of the first and third conduit opposite ends, the first and third conduits being longitudinally symmetrical about the second conduit, and first and third conduit inlet/outlet fittings each connecting to the corresponding adjacent first and third conduit opposite ends thereby forming a closed loop around the second conduit.
In a preferred embodiment each end of the first, second, and third conduits connect to a one piece inlet/outlet header, the header including a first port in fluid c
Logic Jeffrey A.
Memory Stephen B.
Voss Mark G.
Wattelet Jonathan P.
Flanigan Allen
Modine Manufacturing Company
Wood Phillips VanSanten Clark & Mortimer
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