Patent Application
20200352359
The present disclosure relates generally to refrigerated display cabinets, and more specifically to a microchannel heat exchanger configuration for the medium-temperature refrigerated merchandisers.
In practice, the grocery stores and supermarkets use refrigerated merchandisers of different types, which may be open or with doors, for displaying and presenting fresh food and beverages to the customers while maintaining a temperature of the products below a predefined threshold. In order to maintain the low temperature, cold air is circulated to the product display area of the cabinet by passing airflow over a heat exchanger surface of an evaporator. A cold refrigerant is pumped through the internal passages of the tubes which absorb the heat from the air via fins and tube surfaces and changes from a liquid phase to a vapor phase in the process. As a result the temperature of the air passing through the evaporator is lowered. One or more fans are typically included in the base of the refrigerated display cabinet and drive cold air through the heat exchanger and into the product display area of the merchandiser.
In one exemplary embodiment a refrigerated merchandiser includes a product display area comprising a plurality of shelves, an air return passage defined below the plurality of shelves, a first fan disposed at a downstream end of the air return passage, an air distribution passage connected to an outlet of the fan and disposed behind the plurality of shelves and a top passage disposed above the plurality of shelves, and at least one microchannel evaporator at least partially surrounding the first fan, wherein the at least one microchannel evaporator includes at least one bend.
In another example of the above described refrigerated merchandiser the at least one microchannel evaporator comprises a single continuous bend.
In another example of any of the above described refrigerated merchandisers the at least one microchannel evaporator comprises a first straight portion and a second straight portion, the first straight portion being connected to the second straight portion via a bend.
Another example of any of the above described refrigerated merchandisers further includes a second fan at the downstream end of the air return passage, wherein the at least one microchannel evaporator at least partially surrounds the second fan.
In another example of any of the above described refrigerated merchandisers the at least one microchannel evaporator includes a first microchannel evaporator partially surrounding the first fan and a second microchannel evaporator partially surrounding the second fan.
In another example of any of the above described refrigerated merchandisers an outlet of the first microchannel evaporator is connected to an inlet of the second microchannel evaporator such that the first and second microchannel evaporators are arranged in series.
In another example of any of the above described refrigerated merchandisers each of the first and second microchannel evaporators are A-coil microchannel heat exchangers.
In another example of any of the above described refrigerated merchandisers each of the first and second microchannel evaporators are defined by a single bend portion and a lack of straight portions.
In another example of any of the above described refrigerated merchandisers the at least one microchannel evaporator includes a single microchannel evaporator including a first bend defining a first peak, a second bend defining a second peak, and a third bend defining a valley between the first bend and the second bend.
In another example of any of the above described refrigerated merchandisers further includes a first straight portion connecting the first bend to the third bend and a second straight portion connecting the third bend to the second bend.
In another example of any of the above described refrigerated merchandisers the first bend is connected directly to the third bend and the third bend is connected directly to the second bend.
In another example of any of the above described refrigerated merchandisers the at least one microchannel evaporator is positioned relative to the first fan such that a physical orientation of the at least one microchannel evaporator matches localized airflows generated by the first fan.
In another example of any of the above described refrigerated merchandisers the first fan is an axial flow fan.
In another example of any of the above described refrigerated merchandisers the microchannel evaporator is configured to operate at a temperature of no less than 30° F. such that formation of frost on the evaporator is substantially prevented.
An exemplary method for cooling a refrigerated merchandiser includes driving air through at least one microchannel evaporator using at least one axial flow fan, wherein the microchannel evaporator at least partially surrounds the at least one axial flow fan.
In another example of the above described method for cooling a refrigerated merchandiser the microchannel evaporator defines a profile at least partially matching a localized airflow generated by the at least one axial flow fan.
In another example of any of the above described methods for cooling a refrigerated merchandiser the at least one axial flow fan comprises a plurality of axial flow fans, and the at least one microchannel evaporator comprises a number of microchannel evaporators at least equal to the number of axial flow fans.
In another example of any of the above described methods for cooling a refrigerated merchandiser rein each of the microchannel evaporators in the plurality of microchannel heat exchangers is series connected to at least one other microchannel evaporators in the plurality of microchannel evaporators.
Another example of any of the above described methods for cooling a refrigerated merchandiser further includes providing an output of the microchannel evaporator to an air distribution passage.
In another example of any of the above described methods for cooling a refrigerated merchandiser the microchannel evaporator is configured to operate at a temperature of no less than 30° F. such that formation of frost on the evaporator is substantially prevented.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
Also included within the passage 30 is a round-tube plate-fin heat exchanger 50 for cooling the air being provided to the shelves 12. A fan 52 is positioned immediately upstream of the heat exchanger 50 at an aft end of a return cavity 54 below the bottom most shelf 12. The fan 52 drives all of the air from the return cavity 54 to pass through the heat exchanger 50, thereby causing all of the air to be cooled. A downstream end 51 of the heat exchanger 50 expels cooled air into the passage 30. A portion of the air flows upward through the vertical passage 30 to the top passage 40 and the top shelves 12. A redirection feature 32 alters a flow direction of another portion of the cooled air by 180 degrees such that the redirected cooled air is provided to the lower shelves 12. While it is appreciated that the coolant cycle described with regards to a refrigerated cabinet such as the prior art cabinet, or any of the illustrated embodiments of the invention, is a circular cycle the description herein utilizes the upstream end of the air return cavity 54 as the “beginning” or “upstream most” end of the cycle, and the downstream portion of the air curtain as the “end” or “downstream most” end of the cycle.
The size of the gap 30 is dictated by the size of the heat exchanger 50, and the space between the heat exchanger 50 and the distribution plate 20 required to allow sufficient air to be provided to each shelf 12. Further, as all of the air is cooled by the single heat exchanger 50, the heat exchanger 50 must be sufficiently sized to cool all of the air to a temperature that remains below the required temperature until it reaches the farthest shelf 12 from the heat exchanger 50. This can result in overcooling the middle shelves in order to achieve the desired cooling at the top and/or bottom shelves 12. Even further still, the travel from the output of the heat exchanger 50 to each of the shelves 12 where the cooling is required causes the temperature of the air provided to the shelves 12 to be higher than the outlet temperature of the heat exchanger 50.
With reference to
The exemplary modified display case 100 utilizes a ribbon-bend formed flat-tube evaporator 102 in conjunction with an axial flow fan 152 positioned in such manner to minimize pressure losses and allow highly uniform air velocity pattern on the evaporator 100 face which in turn maximizes thermal performance. A flat tube heat exchanger 100 includes an inlet manifold and an outlet manifold fluidly connected by a plurality of flat tubes. The flat tubes may be formed to include a plurality of channels, or internal passageways that are much smaller than the internal passageways of the tubes in the conventional round-tube plate-fin heat exchanger 50.
As used herein, the flat tubes may also comprise mini size multi-port channels, or micro size multi-port channels (otherwise known as microchannel tubes). Hence the flat tube heat exchangers using small size multi-port channels are alternately known as microchannel heat exchangers 102. In other constructions, the flat tubes may include one channel, or internal passageway. The microchannel heat exchanger 102 includes a plurality of secondary heat transfer surfaces in the form of serpentine-shape fins with louvers. The fins encompasses the width of the tube which also defines the minor dimension of the microchannel heat exchanger 102 and through which the air flows. The fins are positioned along the flat tubes and solidly coupled to two adjacent flat tubes by a brazing or welding process.
The cooling cycle of the refrigerated display cabinet 100 includes drawing air in through an air return cavity 154 using an axial flow fan 152. The output of the axial flow fan 152 is provided to the microchannel heat exchanger 102 which is positioned immediately downstream of, and partially surrounds, the axial flow fan 152. As air from the axial flow fan 152 passes through the microchannel heat exchanger 102, the air is cooled. The cooled air is expelled into an air distribution passage 130 defined behind the shelves 112. A portion of the cooled air passes through a distribution plate 120 to cool the corresponding shelves 112. The remainder of the air is provided to a top duct 140, and is directed downward by an air curtain fan 142 to create an air curtain in front of the shelves 112. The air from the shelves 112 and the air curtain is provided to the air return 154, and the cycle repeats.
One negative aspect of some microchannel heat exchangers is a requirement that airflow across the microchannel heat exchanger have a relatively even distribution to provide efficient cooling. The utilization of a fan, such as the axial flow fan 152 localizes airflows, resulting in uneven airflow across a given airflow path. The uneven airflow can result in inefficient microchannel heat exchanger operation if a flat microchannel heat exchanger is utilized immediately downstream of the fan.
With continued reference to
Each of the fans is partially surrounded by a corresponding microchannel heat exchanger 102, with the microchannel heat exchanger 102 including an inlet 103 connected to a bend 105 via a straight portion 107. The bend 105 is connected to an outlet 109 via a second straight portion 107. This configuration is referred to as an A-coil shape and utilizes unfinned tubes folded over to form the A shape. By placing multiple A-coils in series, as in the example of
With reference to the microchannel heat exchanger 102 of
With continued reference to
In yet another microchannel configuration, the flat portions of the microchannel heat exchangers can be omitted entirely by utilizing a larger curvature on the bend portion.
With reference to all of
With continued reference to
It is further understood that any of the above described concepts can be used alone or in combination with any or all of the other above described concepts. Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
