Patent Application
20160265814
The present application and the resultant patent relate generally to refrigeration systems and more particularly relate to cascade refrigeration systems with a water cooled, microchannel condenser for use with a high side ammonia based cooling cycle.
Cascade refrigeration systems generally include a first side cooling cycle, or a high side, and a second side cooling cycle, or a low side cooling cycle. The two cooling cycles interface through a common heat exchanger, i.e., a cascade evaporator-condenser. The cascade refrigeration system may provide cooling at very low temperatures in a highly efficient manner.
Current refrigeration trends promote the use of carbon dioxide, ammonia, and other types of natural refrigerants instead of conventional hydrofluorocarbon based refrigerants. Moreover, there is an interest in improving the overall efficiency of such natural refrigerant based refrigeration systems at least as compared to the hydrofluorocarbon based systems. Further, there is a desire in limiting the overall charge of ammonia used therein so as to mitigate costs as well as potential usage risks and the like.
There is thus a desire for an improved refrigeration system such as a cascade refrigeration system that provides cooling with increased efficiency with natural refrigerants. Moreover, there is a desire for such improved cascade refrigeration systems to limit the overall charge of the ammonia based refrigerant therein in a safe and efficient manner.
The present application and the resulting patent thus provide a condenser for a cascade refrigeration system. The condenser may include an outer shell, a microchannel coil, an ammonia refrigerant flowing through the microchannel coil, and a water based coolant flowing through the outer shell for heat exchange with the ammonia refrigerant.
The present application and the resultant patent further provide herein a cascade refrigeration system. The cascade refrigeration system may include a low side cycle and a high side cycle. The high side cycle may include a water cooled, microchannel heat exchanger.
The present application and the resultant patent further provide herein a cascade refrigeration system. The cascade refrigeration system may include a low side cycle with a carbon dioxide refrigerant and a high side cycle with an ammonia refrigerant. The high side cycle may include a water cooled condenser with a microchannel coil therein.
These and other features and improvements of the present application and the resultant patent will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims.
Referring now to the drawings, in which like numerals refer to like elements throughout the several views,
Generally described, the cascade refrigeration system may include a first side or a high side cycle 110 and a second side or a low side cycle 120. The high side cycle 110 may include one or more high side compressors 130, a high side condenser 140, and a high side expansion valve 150. Additional components also may be used herein. The high side cycle 110 may include a flow of a natural refrigerant 160. The natural refrigerant 160 may include a flow of ammonia 170. Other types of refrigerants may be used herein. The high side cycle 110 and the components therein may have any suitable size, shape, configuration, or capacity. Other components and other configurations may be used herein.
In most known cascade refrigeration systems, the high side condenser 140 typically may be a brazed plate heat exchanger, a copper tube and aluminum fin heat exchanger, and the like. The high side condenser 140 may be water cooled via a flow of water 180 and/or glycol based mixtures. Such known condensers may have a limited operating temperature gradient.
The low side cycle 120 may include one or more low side compressors 190, a low side vapor separator tank 200, a medium temperature loop 210, and a low temperature loop 220. The medium temperature loop 210 may include a pump 230 and one or more medium temperature evaporators 240. The low temperature loop 220 may include a low side expansion valve 250 and one or more low temperature evaporators 260. Additional components also may be used herein. The low side cycle 120 may include a natural refrigerant 160 in the form of a flow of carbon dioxide 270 and the like. Other types of refrigerants may be used herein. The components of the low side cycle 120 may have any suitable size, shape, configuration, or capacity. Other components and other configurations may be used herein.
The two cycles 110, 120 may interface through a cascade evaporator/condenser 280. Specifically, the respective flows of refrigerant 170, 270 may exchange heat via the cascade evaporator/condenser 280. The cascade evaporator/condenser 280 may have any suitable size, shape, configuration, or capacity. Other components and other configurations may be used herein.
The flow of ammonia 170 may be compressed by the high side compressor 130 and condensed in the high side condenser 140. The flow of ammonia 170 may pass through the high side expansion valve 150 and exchange heat in the cascade evaporator/condenser 280. Likewise, the carbon dioxide refrigerant 270 may be compressed by the low side compressor 190 and pass through the cascade evaporator/condenser 280 to exchange heat therein. The carbon dioxide refrigerant 270 may be separated in the vapor separator tank 200 and passed through the medium temperature loop 210 and the low temperature loop 220. The respective refrigeration cycles may then repeat herein.
The water cooled, microchannel condenser 300 may include a shell fluid inlet 340 and a shell fluid outlet 350. The shell fluid inlet 340 and the shelf fluid outlet 350 may be in communication with the interior fluid space 320. A number of web flow diverters 360 may be positioned within the interior fluid space 320 so as to promote the agitation of the fluid therein. The water cooled, microchannel condenser 300 may include a microchannel fluid inlet 370 and a microchannel fluid outlet 380. The microchannel fluid inlet 370 and the microchannel fluid outlet 380 may be in communication with the microchannel coil 330. The water cooled, microchannel condenser 300, and the components thereof, may have any suitable size, shape, configuration, or capacity. Other components and other configurations may be used herein.
In use, the flow of ammonia 170 flows to the water cooled, microchannel condenser 300 via the high side compressors 130. The flow of ammonia 170 enters via the microchannel fluid inlet 370, passes through the microchannel coil 330 within the interior fluid space 320, and exits via the microchannel fluid outlet 380. Likewise, the flow of water or other coolant enters the water cooled, microchannel condenser 300 via the shell fluid inlet 340. The water 180 fills the interior fluid space 220 and exchanges heat with the flow of ammonia 170 within the microchannel coil 330. The web flow diverters 360 may cause turbulence therein for enhanced heat transfer. The flow of water 180 then exits the interior fluid space 320 via the microchannel fluid outlet 380. The flow of water 180 may be reused or recycled as appropriate.
The use of the water cooled, microchannel condensers 300, 400 may provide improved efficiency for the overall cascade refrigeration system 100. The use of the microchannel coil 330 provides an ammonia charge reduction as compared to conventional condensers given the reduced cross-sectional area therein. Moreover, the microchannel coil 330 may provide higher overall operating temperature gradients given the use of the aluminum. The improved efficiency with the lower ammonia charge thus may provide for an overall cost advantage herein.
In addition to the flow of ammonia 170, a flow of carbon dioxide or other refrigerants may be used herein. If carbon dioxide is used, the microchannel coil 330 may be used but not called a condenser. Rather, the microchannel coil 330 may be positioned within the outer shell 310 in what may be described as a fluid (carbon dioxide and the like) to fluid (water and the like) heat exchanger. Other components and other configurations may be used herein.
It should be apparent that the foregoing relates only to certain embodiments of the present application and the resultant patent. Numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.
