FIELD OF THE INVENTION
The present invention relates to heating, ventilation, and air-conditioning (“HVAC”) systems, and more particularly to evaporators and evaporation methods applicable for use in HVAC and similarly associated systems.
BACKGROUND
Flooded and falling-film evaporators are typically used in HVAC chillers to cool a process fluid (e.g., water) which, in turn, is typically used in connection with a heat exchanger coil or air-handling unit to cool air moving through the coil or air-handling unit. Due to the interstitial spacing between the tubes within the evaporator through which the process fluid flows, a relatively large quantity of liquid refrigerant is often required to immerse a sufficient number of the tubes to achieve a high working efficiency of the evaporator. Operationally, excess liquid refrigerant between the tubes may contribute relatively little to the overall efficiency of the HVAC chillers, and can be an additional burden on the cost of the operating and maintaining she chillers.
SUMMARY
The present application provides, in one aspect, a refrigerant evaporator including a shell having a refrigerant inlet and a refrigerant outlet, and a plurality of tubes disposed within the shell and carrying a process fluid. The refrigerant evaporator also includes a baffle positioned adjacent at least some of the plurality of tubes and immersed in the liquid refrigerant to displace the liquid refrigerant.
Other features and aspects of the application will become apparent by consideration of the following detailed description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of a flooded refrigerant evaporator in accordance with a first embodiment of the application, taken along line 1-1 in FIG. 2.
FIG. 2 is a cross-sectional view of the flooded refrigerant evaporator of FIG. 1, taken along line 2-2 in FIG. 1.
FIG. 3 is an enlarged view of a portion of the flooded refrigerant evaporator of FIG. 1.
FIG. 4 is a cross-sectional view of a flooded refrigerant evaporator in accordance with a second embodiment of the application, taken along line 4-4 in FIG. 5.
FIG. 5 is a cross-sectional view of the flooded refrigerant evaporator of FIG. 4, taken along line 5-5 in FIG. 4.
FIG. 6 is a cross-sectional view of a falling-film refrigerant evaporator in accordance with a third embodiment of the application, taken along line 6-6 in FIG. 7.
FIG. 7 is a cross-sectional view of the filling-film refrigerant evaporator of FIG. 6, taken along line 7-7 in FIG. 6.
FIG. 8 is an enlarged view of a portion of the falling film refrigerant evaporator of FIG. 6.
FIG. 9 is a cross-sectional view of a falling-film refrigerant evaporator in accordance with a fourth embodiment of the application, taken along line 9-9 in FIG 10.
FIG. 10 is a cross-sectional view of the falling-film refrigerant evaporator of FIG. 9, taken along line 10-10 in FIG. 9.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
DETAILED DESCRIPTION
FIGS. 1 and 2 illustrate a flooded refrigerant evaporator 10 used in connection with an HVAC chiller to cool a process fluid (e.g., water). Such a process fluid may be used with a heat exchanger coil or air-handling unit to cool air moving through the coil or air-handling unit. The evaporator 10 includes a shell 14 having an inlet 18 through which liquid refrigerant enters the shell 14, an outlet 22 through which gaseous refrigerant exits the shell 14, and a plurality of tubes 26 disposed within the shell 14 for carrying the process fluid. In the illustrated construction of the evaporator 10, the shell 14 includes a cylindrical shape (FIG. 1) though such shape is not a limitation of the present application or embodiment given that other shapes are also contemplated. The refrigerant inlet 18 and the refrigerant outlet 22 are located below and above the tubes 26, respectively, to flood the shell 14 with liquid refrigerant by introducing the liquid refrigerant below the tubes 26.
The tubes 26 are oriented substantially horizontally relative to a support surface of the refrigerant evaporator 10 in a series of rows (FIGS. 1 and 2) though such orientation is not a limitation of the present application or embodiment. The tubes 26 depicted in the illustrated embodiment are spaced relative to each other by a triangular pitch (FIG. 1). Alternatively, the tubes could have a rectangular pitch as shown in FIGS. 6 and 9. The liquid refrigerant has a top surface 30, and a first plurality of the tubes 26 are immersed in the liquid refrigerant and located entirely below the top surface 30 of the liquid refrigerant (FIG. 1). A second plurality of the tubes 26 are located at least partially above the fop surface 30 of the liquid refrigerant, and are at least partially immersed in liquid refrigerant and at least partially surrounded by gaseous refrigerant. A third plurality of the tubes 26 are surrounded by gaseous refrigerant and located entirely above the top surface 30 of the liquid refrigerant.
With reference to FIGS. 1 and 2, the refrigerant evaporator 10 also includes a baffle 34 immersed in the liquid refrigerant and positioned adjacent to the tubes 26 that are immersed in the liquid refrigerant. The baffle 34 includes a plurality of apertures 38 through which the tubes 26 are received (FIG. 1). The tubes 26 include an outer diameter less than that of the apertures 38 in which the tubes 26 are received, thereby forming an annular gap 42 between each of the tubes 26 and the baffle 34 through which liquid refrigerant may flow (FIGS. 1 and 3). In an alternative construction, the baffle 34 may be positioned between adjacent tubes 26 that are immersed in the liquid refrigerant and include an outer peripheral surface containing a plurality of grooves in which the tubes are received. Alternatively, the baffle 34 may have a smooth outer peripheral surface without any grooves and be located toward the bottom of the shell 14 below the tubes 26. In the illustrated construction of the evaporator 10 at least a portion of the baffle 34 is located between the lower-most tubes 26 and the shell 14 (FIGS. 1 and 2). Also, in the illustrated construction of the evaporator 10, the shell 14 includes a first length L0 and the baffle 34 includes a second length L1 such that L1 is about 50% of the length L0 (FIG. 2). Alternatively, the baffle 34 may include a length L1 that is at least about 75% or about 95% of the length L0.
In operation of the flooded refrigerant evaporator 10, liquid refrigerant flows into the shell 14 via the refrigerant inlet 18. Near the refrigerant inlet 18, the shell 14 is occupied by nearly pure liquid refrigerant because the liquid refrigerant in this region has yet to exchange heat with the tubes 26 to cause it to evaporate. Accordingly, it is considered that liquid refrigerant in this region of the shell 14 has a low void fraction. As the baffle 34 occupies some of the internal volume of the shell 14, the baffle 34 displaces incoming liquid refrigerant relative to the condition if the baffle 34 were not provided. In other words, by displacing the liquid refrigerant, the presence of the baffle 34 can act to effectively raise the top surface 30 of liquid refrigerant in the shell 14. Liquid refrigerant flows through each of the annular gaps 42 and contacts the outer periphery of the tubes 26. Contact between the tubes 26 and the liquid refrigerant allows heat to be transferred from the process fluid to the liquid refrigerant. This causes the liquid refrigerant to evaporate into gaseous refrigerant (e.g., phase change), which increases the void fraction of the surrounding liquid refrigerant. It should be understood that in one aspect the refrigerant passing through each of the annular gaps 42 around the periphery of the tubes 26 is locally isolated for a period of time from the rest of the refrigerant in the shell and absorbs the heat from the process fluid and evaporates into gaseous refrigerant. The gaseous refrigerant bubbles through the annular gaps 42 before exiting the baffle 34 and then exits the shelf 14 via the refrigerant outlet 22. The void fraction within the shell 14 progressively increases from where liquid refrigerant enters the shell 14 via the refrigerant inlet 18 towards the top surface 30 of liquid refrigerant. By displacing liquid refrigerant in the shell 14 toward regions within the shell 14 which would otherwise have a high void traction of liquid refrigerant in absence of the baffle 34, the inclusion of the baffle 34 reduces the amount of liquid refrigerant that is used compared to a typical flooded refrigerant evaporator without reducing the working efficiency of the evaporator.
The present application contemplates that the baffles may have a length less than the length of the Shell. A plurality of baffles may be used to obtain the desired balance of refrigerant and thermal performance. Further, in one form of the present application the baffle(s) may extend the substantial length of the shell.
FIGS. 4 and 5 illustrate a second construction of a flooded refrigerant evaporator 46 used in connection with an HVAC chiller to cool a process fluid. Like components are identified with like reference numerals with the letter “a,” and will not be described again in detail. Rather than incorporating only a single baffle 34 like that shown in FIGS. 1 and 2 and described above, the evaporator 46 includes a plurality of baffles located in different positions throughout the shell 14a. Particularly, the flooded refrigerant evaporator 46 includes a first baffle 50 positioned adjacent the lower-most tubes 26a, a second and third baffle 54, 58 located above the first baffle 50 and axially spaced from each other, and a forth baffle 62 located above and axially spaced between the second and third baffles 54, 58. Alternatively, the evaporator 46 may include more or fewer baffles that may be distributed throughout the shell 14a in various combinations and configuration. In the illustrated construction of the evaporator 46, the first, second, and third baffles 50, 54, 58 are immersed in liquid refrigerant and positioned adjacent to the tubes 26a that are immersed in the liquid refrigerant (FIG. 4). The fourth baffle 62 is not entirely immersed in liquid refrigerant and is positioned adjacent to the tubes 26a that are at least partially immersed in liquid refrigerant and at least partially surrounded by gaseous refrigerant.
The baffles 50, 54, 58, 62 each include a plurality of apertures 38a through which the tubes 26a are received. The tubes 26a include an outer diameter less than that of the apertures 38a in which the tubes 26a are received, thereby forming an annular gap 42a between each of the tubes 26a and the baffles 50, 54, 58, 62 through which liquid refrigerant may flow. Each of the baffles 50, 54, 58, 62 also includes a plurality of grooves 66 in which only a portion of some of the tubes 26a is received. As such, the grooves 66 in adjacent baffles (e.g., the first and second baffles 50, 54, or the first and third baffles 50, 58) collectively define an annular gap 68 through which liquid refrigerant may flow. In the illustrated construction of the evaporator 46, at least a portion of the lower-most baffle 50 is located between the lower-most tubes 26a and the shell 14a (FIGS. 4 and 5). Also, in the illustrated construction of the evaporator 46, the shell 14a includes a first length L0 and the first baffle 50 includes a second length L1 such that L1 is about 95% of the length L0 (FIG. 5). The second, third, and fourth baffles 54, 58, 62 include a third, fourth, and fifth length L2, L3, L4, respectively, such that the lengths L2, L3, and L4 are each about 25% of the length L0 (FIG. 5). Alternatively, each of the baffles 54, 58, 62 may include a length that is at least about 25% to at least about 95% of the length L0.
The flooded refrigerant evaporator 46 operates in an identical fashion as the evaporator 10 shown in FIGS. 1 and 2 and described above. However, each of the baffles 50, 54, 58, 62 contributes to the displacement of the liquid refrigerant within the shell 14a an amount commensurate with the volume with the respective baffles 50, 54, 58, 62.
FIGS. 6 and 7 illustrate a falling-film refrigerant evaporator 70 used in connection with an HVAC chiller to cool a process fluid (e.g., water). Such a process fluid may be used with a heat exchanger coil or air-handling unit to cool air moving through the coil or air-handling unit. The evaporator 70 includes a shell 74 having an inlet 78 through which liquid refrigerant enters the shell 74, an outlet 82 through which gaseous refrigerant exits the shell 74, and a plurality of tubes 86 disposed within the shell 74 for carrying a process fluid. In the illustrated construction of the evaporator 70, the shell 74 includes a cylindrical shape (FIG. 6). Alternatively, the shell may include a non-cylindrical shape. The refrigerant inlet 78 and outlet 82 are located above the tubes 86 to fill the shell 74 with liquid refrigerant by introducing the liquid refrigerant above the tubes 86.
The tubes 86 are oriented substantially horizontally relative to a support surface of the refrigerant evaporator 70 in a series of rows (FIGS. 6 and 7) though such orientation is only a non-limiting example of various possible orientations. The tubes 86 in the illustrated embodiment are spaced relative to each other by a rectangular pitch (FIG. 6). Alternatively, the tubes could have a triangular pitch as shown in FIGS. 1 and 4. The liquid refrigerant has a top surface 90, and a first plurality of the tubes 86 are immersed in the liquid refrigerant and located entirely below the top surface 90 of the liquid refrigerant (FIG. 6). A second plurality of the tubes 86 are located at least partially above the top surface 90 of the liquid refrigerant, and are at least partially immersed in liquid refrigerant and at least partially surrounded by gaseous refrigerant. A third plurality of the tubes 86 are located entirely above the top surface 90 of the liquid refrigerant and are surrounded by gaseous refrigerant (FIG. 6).
With reference to FIGS. 6 and 7, the falling-film refrigerant evaporator 70 also includes a baffle 94 immersed in the liquid refrigerant and positioned adjacent to the tubes 86 that are immersed in the liquid refrigerant. The baffle 94 includes a plurality of apertures 98 through which the tubes 86 are received. The tubes 86 include an outer diameter less than that of the apertures 98 in which the tubes 86 are received, thereby forming an annular gap 102 between each of the tubes 86 and the baffle 94 through which liquid refrigerant may flow (FIGS. 6 and 8). In an alternative construction, the baffle 94 may be positioned between adjacent tubes 86 that are immersed in the liquid refrigerant and include an outer peripheral surface containing a plurality of grooves in which the tubes 86 are received. Alternatively, the baffle 94 may have a smooth other peripheral surface without airy grooves and be located toward the bottom and sides of the shell 74 below and adjacent the tubes 86, respectively. In the illustrated construction of the evaporator 70 at least a portion of the baffle 94 is located between the lower-most tubes 86 and the shell 74 (FIGS. 6 and 7). Also, in the illustrated construction of the evaporator 70, the shell 74 includes a first length L0 and the baffle 94 includes a second length L1 such that L1 is about 50% of the length of L0. Alternatively, the baffle 94 may include a length L1 that is at least about 75% or about 95% of the length L0.
In operation of the falling-film evaporator 70, liquid refrigerant falls from the refrigerant inlet 78 down through the tubes 86 generally row by row. Near the region of the bottom portion of the shell 74, the shell 74 is occupied by nearly pure liquid refrigerant because the liquid refrigerant in this region has yet to exchange heat with the tubes 86 to cause it to evaporate. Accordingly, it is considered that liquid refrigerant in this region of the shell 74 has a low void fraction. As the baffle 94 occupies some of the internal volume of the shell 74, the baffle 94 displaces incoming liquid refrigerant upwardly in the shell 74 toward the tubes 86 above the top surface 90 of liquid refrigerant relative to the condition if the baffle 94 were not provided. In other words, by displacing the liquid refrigerant, the presence of the baffle 94 can act to effectively raise the top surface 90 of liquid refrigerant in the shell 74. Liquid refrigerant flows through each of the annular gaps 102 and contacts the outer periphery of the tubes 86. Contact between the tubes 86 and the liquid refrigerant allows heat to be transferred from the process fluid to the liquid refrigerant. This causes the liquid refrigerant to evaporate into gaseous refrigerant, which increases the void fraction of the surrounding liquid refrigerant. The gaseous refrigerant bubbles through the annular gaps 102 before exiting the baffle 94 and then exits the shell 74 via the refrigerant outlet 82. The void fraction within the shell 74 progressively increases from the bottom of the shell 74 towards the top surface 90 of liquid refrigerant. By displacing liquid refrigerant in the shell 74 toward regions within the shell 74 which would otherwise have a high void fraction of liquid refrigerant in absence of the baffle 94, the baffle 94 reduces the amount of liquid refrigerant that is used compared to a typical falling-film evaporator without reducing the working efficiency of the evaporator.
FIGS. 9 and 10 illustrate a second construction of a falling-film refrigerant evaporator 106 used in connection with an HVAC chiller to cool a process fluid. Like components are identified with like reference numerals with the letter “a,” and will not be described again in detail. Rather than incorporating only a single baffle 94 like that shown in FIGS. 6 and 7 and described above, the evaporator 106 includes a plurality of baffles located in different positions throughout the shell 74a. Particularly, the falling-film refrigerant evaporator 106 includes a first baffle 110 positioned adjacent the lower-most tubes 86a, a second and third baffle 114, 118 located above the first baffle 110 and axially spaced from each other, and a fourth baffle 122 located above and axially spaced between the second and third baffles 114, 118. Alternatively, the evaporator 106 may include more or fewer baffles that may be distributed throughout the shell 74a in various combinations. In the illustrated construction of the evaporator 106, the first, second, and third baffles 110, 114, 118 are immersed in liquid refrigerant and positioned adjacent to the tubes 86a that are immersed in the liquid refrigerant (FIG. 9). The fourth baffle 122 is not entirely immersed in liquid refrigerant and is positioned adjacent to the tubes 86a that are at least partially immersed in liquid refrigerant and at least partially surrounded by gaseous refrigerant. The fourth baffle 122 is also positioned adjacent to the tubes 86a that are surrounded by gaseous refrigerant.
The baffles 110, 114, 118, 122 each include a plurality of apertures 98a through which the tubes 86a are received. The tubes 86a include an outer diameter less than that of the apertures 98a in which the tubes 86a are received, thereby forming an annular gap 102a between each of the tubes 86a and the baffles 110, 114, 118, 122 through which liquid refrigerant may flow. In the illustrated construction of the evaporator 106 at least a portion of the lower-most baffle 110 is located between the lower-most tubes 86a and the shell 74a (FIGS. 9 and 10). Also, in the illustrated construction of the evaporator 106, the shell 74a includes a first length L0 and the first baffle 110 includes a second length L1 such that L1 is about 95% of the length L0 (FIG. 10). The second, third, and fourth baffles 114, 118, 122 include a third, fourth, and fifth length L2, L3, L4, respectively, such that the lengths L2, L3, and L4 are each about 25% of the length L0 (FIG. 10). Alternatively, each of the baffles 114, 118, 122 may include a length that is at least about 25% to at least about 95% of the length L0.
The falling-film refrigerant evaporator 106 operates in an identical fashion as the evaporator 70 shown in FIGS. 6 and 7 and described above. However, each of the baffles 110, 114, 118, 122 contributes to the displacement of the liquid refrigerant within the shell 74a and amount commensurate with the volume with the respective baffles 110, 114, 118, 122.
In operation, embodiments of the present application can systematically control and/or influence the rate of heat exchange by the two phased flow of refrigerant in a multi-dimensional environment while utilizing a static baffle, in a lower portion of the shell, for liquid refrigerant displacement. The present application can be modified in one or more variants to one or more of its elements to enable an improved apparatus and method for improving the heat exchange (i.e., maximizing the reduction of heat) while optimizing the use of lesser refrigerant. It will be further appreciated that instructions of operation and/or assembly of various embodiments of the present application can take the form of a kit, a retrofit assembly, or general method for operation and that such instructions may be available in a variety of formats including but not limited to print, electronic, oral, and/or visual medium. Similarly, embodiments of the present application may be modified in one or more variants to one or more of the characteristics of its operation (e.g., variation in process fluid temperature, vapor velocity, etc.) to enable an improved apparatus and method for improving the heat exchange (i.e., maximizing the reduction of heat) while optimizing the use of lesser refrigerant. In one embodiment the liquid refrigerant is displaced by the physical structure of the baffle and by the refrigerant vapor generated within the gaps 42 between the outer surface of the tubes and the baffle.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the inventions are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred utilized in the description above indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacing the same may be contemplated as within the scope of the invention, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary.
Patent Application
20140202203
