Refrigeration – Processes – Exchanging heat between plural systems – e.g. – disparate
Reexamination Certificate
2002-07-17
2003-07-22
Tapolcai, William E. (Department: 3744)
Refrigeration
Processes
Exchanging heat between plural systems, e.g., disparate
C062S612000, C062S335000
Reexamination Certificate
active
06595009
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to the generation and the provision of refrigeration using a multicomponent refrigerant.
BACKGROUND ART
Refrigeration is used extensively in the freezing of foods, production of pharmaceuticals, liquefaction of natural gas, and in many other applications wherein refrigeration is required to provide cooling duty to a refrigeration load.
A recent significant advancement in the field of refrigeration is the development of refrigeration systems using multicomponent refrigerants which are able to generate refrigeration much more efficiently than conventional systems. These refrigeration systems, also known as mixed gas refrigerant systems or MGR systems, are particularly attractive for providing refrigeration at very low or cryogenic temperatures such as below −80° F.
Typically an MGR system employs a single circuit system. Such systems are uncomplicated from an equipment standpoint, but several operational issues limit their effectiveness. Among these issues is the problem of handling two-phase refrigerant mixtures. In particular, if the point of refrigeration use is substantially separated from the primary compression and heat exchange equipment, liquid stagnation-separation can occur in return piping or in vaporizing exchanger passes. In addition, low temperature partial evaporators may have problems motivating the high boiling constituents to exit the exchanger. This will result in a deterioration of the composite approaches and hence increase power consumption. Both of these issues result in complications to the process including higher design pressure drops and the necessity of cold end phase separators. The equipment and power cost associated with addressing these problems can become significant.
With the phase out of CFC's, a second complication exists for refrigerant systems based upon zeotropic mixtures. Such systems must often rely upon non-conventional refrigerants such as fluoroethers for high boiling service. By high boiling it is meant those refrigerant constituents that under typical system pressures boil or condense near the temperature of the ambient utility (air/water/chilled water). These high boiling refrigerants typically are often costly and/or are somewhat toxic. In distributed refrigeration applications like food processing, this represents a substantial problem. First, remote refrigerant use will necessitate the purchase of substantial quantities for system charge. Secondly, distributed use is often associated with the transit of refrigerants across or near occupied space. As a consequence, there are additional safety precautions that must be made. For instance, when evaporators need servicing they must be safely evacuated. The presence of a semi-toxic high boiler complicates such a procedure.
Accordingly it is an object of this invention to provide a method for providing multicomponent refrigeration which reduces or eliminates problems associated with heretofore available such systems such as cold end phase separation, increased refrigeration charging costs, and potential toxic refrigerant contamination.
SUMMARY OF THE INVENTION
The above and other objects, which will become apparent to those skilled in the art upon a reading of this disclosure, are attained by the present invention which is:
A method for providing refrigeration comprising:
(A) condensing a first multicomponent refrigerant to produce a saturated liquid, expanding the saturated liquid first multicomponent refrigerant, and vaporizing the expanded first multicomponent refrigerant by indirect heat exchange with the condensing first multicomponent refrigerant.
(B) condensing a second multicomponent refrigerant by indirect heat exchange with the vaporizing first multicomponent refrigerant, said second multicomponent refrigerant having a dew point which is less than the dew point of said saturated liquid first multicomponent refrigerant, and said second multicomponent refrigerant having bubble point which is greater than the bubble point of said vaporizing first multicomponent refrigerant; and
(C) vaporizing the condensed second multicomponent refrigerant by passing heat from a refrigeration load into the condensed second multicomponent refrigerant thereby providing refrigeration to the refrigeration load; and
As used herein the term “expansion” means to effect a reduction in pressure.
As used herein the term “expansion device” means apparatus for effecting expansion of a fluid.
As used herein the term “compressor” means apparatus for effecting compression of a fluid.
As used herein the term “multicomponent refrigerant” means a fluid comprising two or more species and capable of generating refrigeration.
As used herein the term “refrigeration” means the capability to absorb heat from a subambient temperature system and to reject it at a superambient temperature.
As used herein the term “refrigerant” means fluid in a refrigeration process which undergoes changes in temperature, pressure and possibly phase to absorb heat at a lower temperature and reject it at a higher temperature.
As used herein the term “subcooling” means cooling a liquid to be at a temperature lower than the saturation temperature of that liquid for the existing pressure.
As used herein the term “superheating” means warming a gas above the saturation/dew point.
As used herein the term “indirect heat exchange” means the bringing of fluids into heat exchange relation without any physical contact or intermixing of the fluids with each other.
As used herein the term “refrigeration load” means a fluid or object that requires a reduction in energy, or removal of heat, to lower its temperature or to keep its temperature from rising.
As used herein the term “saturated liquid” means a liquid that is at a temperature at which the application of heat will initiate vaporization.
As used herein the term “dew point” means the temperature at which condensation of a vapor first commences.
As used herein the term “bubble point” means the temperature at which vaporization of a liquid first commences.
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Howard Henry Edward
Timm Martin Lee
Ktorides Stanley
Praxair Technology Inc.
Tapolcai William E.
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