US20120103009A1

US20120103009A1 - Hybrid serial counterflow dual refrigerant circuit chiller

Info

Publication number: US20120103009A1
Application number: US13/256,753
Authority: US
Inventors: Haiping Ding; Songtao Li; Michael A. Stark
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2009-05-15
Filing date: 2009-05-15
Publication date: 2012-05-03
Also published as: CN102428325B; WO2010130064A1; CN102428325A

Abstract

A dual refrigerant circuit chiller (10) has a first refrigerant circuit (100) including a first condenser (130) and a first evaporator (140), a second refrigerant circuit (200) including a second condenser (230) and a second evaporator (240), a condenser assembly (30) including the first condenser (130) and the second condenser (230) interconnected in a series cooling fluid circuit, and an evaporator assembly (40) including the first evaporator (140) and the second evaporator (240) interconnected in a series fluid circuit with a waterbox (50) disposed intermediate the first evaporator (140) and the second evaporator (240). The evaporator assembly (40) has a chilled fluid inlet (45) and a chilled fluid outlet (43) that are disposed at opposite longitudinal ends of the evaporator assembly (40). Each of the first and second evaporators (140, 240) embodies a multiple pass circuit fluid-to-refrigerant heat exchanger.

Description

FIELD OF THE INVENTION

This invention relates generally to dual circuit chillers and, more particularly, to the improvement in the waterside performance of a dual refrigerant circuit chiller.

BACKGROUND OF THE INVENTION

Chillers are well known for use in providing chilled fluid, commonly water or brine, for use in air conditioning systems for buildings, especially large commercial buildings. A common type of chiller includes a tube-in-shell heat exchanger that functions as a refrigerant vapor condenser, a tube-in-shell heat exchanger that functions as a refrigerant liquid evaporator, and a centrifugal compressor that has an inlet in refrigerant flow communication with the evaporator and an outlet in refrigerant flow communication with the condenser. In the condenser, cooling fluid, most commonly, water is passed through the heat exchange tubes in heat exchange relationship with hot refrigerant vapor discharged from the compressor into the shell of the condenser and flowing over the heat exchange tubes. In doing so, the refrigerant vapor is condensed and the water flowing through the heat exchange tubes is heated. The condensed liquid refrigerant is passed through an expansion device and thereby expanded to form a lower pressure, lower temperature refrigerant liquid/vapor mixture. The refrigerant liquid/vapor mixture is delivered into the shell of the evaporator and dispersed to flow over the heat exchange tubes therein. In the evaporator, water passing through the heat exchange tubes is cooled and the refrigerant liquid/vapor mixture is heated and the liquid refrigerant evaporated. The refrigerant vapor exits the shell of the evaporator and passes back the inlet of the compressor, thereby completing the refrigerant flow circuit. The chilled water having traversed the evaporator heat exchange tubes is delivered to the building air conditioning system for cooling air to be supplied to a climate-controlled space or spaces within the building.
In one-type of chiller, commonly termed a single pass, single circuit chiller, a single water-cooled condenser, a single centrifugal compressor and single water-chilling evaporator are connected in a single refrigerant circuit as described above. In the condenser, a plurality of parallel water-conveying tubes extends longitudinally in parallel to the axis of the condenser shell in a single-pass arrangement. Similarly, in the evaporator, a plurality of parallel water-conveying tubes extends longitudinally in parallel to the axis of the condenser shell in a single-pass arrangement. Typically, the water to chilled passing through the single-pass tubes of the evaporator passes in counterflow relationship to the cooling water passing through the single-pass tubes of the condenser. However, the water-chilling capability that can be obtained with a single-pass, single-circuit chiller is limited.
One approach to increasing water-chilling capacity is to provide a dual circuit chiller consisting of two single pass, single circuit chillers arranged with their respective refrigerant circuits in parallel arrangement and the water passes of the respective condensers and of the respective evaporators connected in series relationship. Again the water to be chilled passing through the single pass tubes of the evaporators passes in counterflow relationship to the cooling water passing through the single-pass tubes of the condensers. Thus, the water to be chilled passes first through the condenser associated with the first refrigerant circuit and thence through the condenser associated with the second refrigerant circuit, but the cooling water passes first through the evaporator associated with the second refrigerant circuit and thence through the evaporator associated with the first refrigerant circuit.

SUMMARY OF THE INVENTION

In an aspect of the invention, a dual refrigerant circuit chiller is provided having a first refrigerant circuit including a first condenser and a first evaporator; a second refrigerant circuit including a second condenser and a second evaporator, a condenser assembly including the first condenser and the second condenser interconnected in a series cooling fluid circuit, and an evaporator assembly including the first evaporator and the second evaporator interconnected in a series fluid circuit and a waterbox disposed intermediate the first evaporator and the second evaporator. The condenser assembly has a cooling fluid inlet in fluid communication with the second condenser and a cooling fluid outlet in fluid communication with the first condenser. The evaporator assembly has a circuit fluid inlet in fluid communication with the first evaporator and a circuit fluid outlet in fluid communication with the second evaporator. The circuit fluid inlet and the circuit fluid outlet are disposed at opposite longitudinal ends of the evaporator assembly. In an embodiment the first evaporator has a multiple pass circuit fluid-to-refrigerant heat exchanger having an outlet in fluid communication with the waterbox and an inlet in fluid communication with the circuit fluid inlet of the evaporator assembly, and the second evaporator has a multiple pass circuit fluid-to-refrigerant heat exchanger having an inlet in fluid communication with the waterbox and an outlet in fluid communication with the circuit fluid outlet of the evaporator assembly. In an embodiment, the circuit fluid-to-refrigerant heat exchanger of the first evaporator and the circuit fluid-to-refrigerant heat exchanger of the second evaporator each comprise a three pass tube bundle heat exchanger.
In an aspect of the invention, a dual circuit chiller is provided having a first refrigerant circuit including a first condenser and a first evaporator; a second refrigerant circuit including a second condenser and a second evaporator, a condenser assembly including the first condenser and the second condenser interconnected in a series cooling fluid circuit with a cooling fluid inlet in fluid communication with the second condenser and a cooling fluid outlet in fluid communication with the first condenser; and an evaporator assembly including the first evaporator and the second evaporator interconnected in a series fluid circuit and a waterbox disposed intermediate the first evaporator and the second evaporator, the waterbox having a first chamber, a second chamber and a third chamber. The evaporator assembly has a circuit fluid inlet and the circuit fluid outlet disposed at opposite longitudinal ends of the evaporator assembly, a first bypass conduit having an inlet in fluid communication with the circuit fluid inlet of the evaporator assembly and an outlet in fluid communication with the first chamber of the waterbox; a first multiple pass circuit fluid-to-refrigerant heat exchanger disposed in the first evaporator having an inlet in fluid communication with the first chamber of the waterbox and an outlet in fluid communication with the second chamber of the waterbox; a second bypass conduit having an outlet in fluid communication with the circuit fluid outlet of the evaporator assembly and an inlet in fluid communication with the third chamber of the waterbox; and a second multiple pass circuit fluid-to-refrigerant heat exchanger of the second evaporator having an inlet in fluid communication with the second chamber of the waterbox and an outlet in fluid communication with the third chamber of the waterbox.
In any embodiment, the cooling fluid may be cooling water and the circuit fluid may be chiller water. In any embodiment, the cooling fluid may be cooling water and the circuit fluid may be chiller brine. Additionally, in any embodiment, the condenser assembly may also be a include a waterbox disposed intermediate the first condenser and the second condenser, a multiple pass cooling fluid-to-refrigerant heat exchanger in the second condenser having an outlet in fluid communication with the waterbox and an inlet in fluid communication with the cooling fluid inlet of the condenser assembly, and a multiple pass cooling fluid-to-refrigerant heat exchanger in the first condenser having an inlet in fluid communication with the waterbox and an outlet in fluid communication with the cooling fluid outlet of the condenser assembly, with the cooling fluid inlet and the cooling fluid outlet disposed at opposite longitudinal ends of the condenser assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the disclosure, reference will be made to the following detailed description which is to be read in connection with the accompanying drawing, where:

FIG. 1 is a plan view, in perspective, of an exemplary embodiment of a dual circuit chiller in accordance with one aspect of the present invention applied to the evaporator water circuit;

FIG. 2 is an elevation view, in perspective, of the dual circuit chiller of FIG. 1;

FIG. 3 is a schematic illustration of the refrigerant circuits of the embodiment of the dual circuit chiller shown in FIG. 1;

FIG. 4 is a schematic illustration of the condenser waterside and evaporator waterside circuits of the embodiment of the dual circuit chiller shown in FIG. 1;

FIG. 5 is a elevation view, in cross-section, taken along line 5-5 of FIG. 4;

FIG. 6 is a elevation view, in cross-section, taken along line 6-6 of FIG. 4;

FIG. 7 is a schematic illustration of the condenser waterside and the evaporator waterside circuits in another exemplary embodiment of a dual circuit chiller in accordance with an aspect of the invention;

FIG. 8 is a elevation view, in cross-section, taken along line 8-8 of FIG. 7;

FIGS. 9A and 9B are elevation views, in cross-section, taken along line 9A-9A and 9B-9B, respectively, of FIG. 7;

FIG. 10 is a schematic illustration of the condenser waterside and the evaporator waterside circuits in another exemplary embodiment of a dual circuit chiller in accordance with an aspect of the invention;

FIG. 11 is a elevation view, in cross-section, taken along line 11-11 of FIG. 7;

FIG. 12 is a schematic illustration of the evaporator waterside circuit in another exemplary embodiment of a dual circuit chiller in accordance with an aspect of the invention;

FIG. 13 is a elevation view, in cross-section, taken along line 13-13 of FIG. 12;

FIG. 14 is a elevation view, in cross-section, taken along line 14-14 of FIG. 12;

FIG. 15 is a elevation view, in cross-section, taken along line 15-15 of FIG. 12;

FIG. 16 is a elevation view, in cross-section, taken along line 16-16 of FIG. 12;

FIG. 17 is a plan view of the embodiment of the intermediate waterbox depicted in FIG. 12;

FIG. 18 is a perspective illustrating an alternate embodiment of the intermediate waterbox of the embodiment of the dual refrigerant circuit chiller depicted in FIG. 12;

FIG. 19 is a schematic illustration of the evaporator waterside circuit in another exemplary embodiment of a dual circuit chiller in accordance with an aspect of the invention;

FIG. 20 is a plan view of the embodiment of the intermediate waterbox depicted in FIG. 19;

FIG. 21 is a elevation view, in cross-section, taken along line 21-21 of FIG. 19;

FIG. 22 is a elevation view, in cross-section, taken along line 21-21 of FIG. 19;

FIG. 23 is a elevation view, in cross-section, taken along line 21-21 of FIG. 19;

FIG. 24 is a elevation view, in cross-section, taken along line 24-24 of FIG. 19;

FIG. 25 is a perspective illustrating the intermediate waterbox of the embodiment of the dual refrigerant circuit chiller depicted in FIG. 19;

DETAILED DESCRIPTION

Referring initially to FIGS. 1-4, 7 and 10 of the drawing, in particular, there is depicted an exemplary embodiment of a compression machine 10 having two independent refrigerant circuits 100, 200 disposed in parallel refrigerant flow relationship, commonly referred to and referred to herein as a dual circuit chiller. The chiller 10 includes a water-cooled condenser 30, a water-chilling evaporator 40, and a pair of refrigerant vapor compressors 120, 220. The refrigerant vapor compressors 120, 220 may be centrifugal compressors. Separate drive motors 122, 222 may be provided in operative association with the first compressor 120 and the second compressor 220, respectively. The first drive motor 122 drives only the first compressor 120. The second drive motor 222 drives only the second compressor 220.
The condenser 30 comprises a first condenser 130 and a second condenser 230 disposed in serial water flow relationship. Each of the first condenser 130 and the second condenser 230 comprises a cooling fluid-to-refrigerant, tube-in-shell heat exchanger having a plurality of heat exchange tubes disposed within a longitudinally extending, closed cylindrical shell. The distal ends of the first and second condensers 130, 230 are closed by end caps 134, 234, respectively, which are mounted to the tube sheets 136, 236, respectively. In the embodiment of the chiller 10 depicted in FIGS. 1-4, the respective proximal ends of the first condenser 130 and the second condenser 230 are interconnected at respective tube sheets 32. However, in the embodiment of the chiller 10 depicted in FIGS. 7 and 10, the respective proximal ends of the first condenser 130 and the second condenser 230 are interconnected to a water box 60 disposed between the respective tube sheets 32 of the first and second condensers 130, 230.
The evaporator 40 comprises a first evaporator 140 and a second evaporator 240 disposed in serial water flow relationship. Each of the first evaporator 140 and the second evaporator 240 comprises a circuit fluid-to-refrigerant, tube-in-shell heat exchanger having a plurality of heat exchange tubes disposed within a longitudinally extending, closed cylindrical shell. The distal ends of the first and second evaporators 140, 240 are closed by end caps 144, 244, respectively, which are mounted to the tube sheets 146, 246, respectively. The respective proximal ends of the first evaporator 140 and the second evaporator 240 are interconnected to a water box 50 disposed between the respective tube sheets 42 of the first and second evaporators 140, 240.
As noted previously, the dual circuit chiller 10 has two independent refrigerant circuits 100, 200 disposed in parallel relationship. The first refrigerant circuit 100 includes the first compressor 120, the first condenser 130 and the first evaporator 140. In operation, high pressure, high temperature refrigerant vapor discharges from the first compressor 120 through discharge line 124 into the shell of the first condenser 130. The high pressure, high temperature refrigerant vapor introduced into the shell of the first condenser 130 passes over the exterior of the heat exchange tubes therein in heat exchange relationship with the cooling water passing through the heat exchange tubes, whereby the refrigerant vapor is cooled and condensed to a high pressure refrigerant liquid and the cooling water is heated. The high pressure, condensed refrigerant liquid passes from the first condenser 130 to the first evaporator 140 through a refrigerant passage 111 in which is disposed an expansion device 125.
As the high pressure refrigerant liquid traverses the expansion device 125, the refrigerant liquid expands to a lower pressure and a lower temperature to form, most typically, a saturated mixture of refrigerant liquid and refrigerant vapor at the lower pressure and the lower temperature. The lower pressure, lower temperature liquid/vapor mixture is delivered via the passage 111 to and introduced into the shell of the first evaporator 140. The lower temperature refrigerant liquid collects in the shell at least partially immersing the heat exchange tubes of the first evaporator 140. Thus, the chiller water passing through the tubes of the first evaporator 140 passes in heat exchange relationship with the refrigerant introduced into the shell of the first evaporator 140, whereby the refrigerant liquid is heated and evaporated to a refrigerant vapor and the chilled water is cooled. The low pressure, low temperature refrigerant vapor passes from the first evaporator through suction line 126 to return to the suction inlet of the first compressor 120.
The second refrigerant circuit 200 includes the second compressor 220, the second condenser 230 and the second evaporator 240. In operation, high pressure, high temperature refrigerant vapor discharges from the second compressor 220 through discharge line 224 into the shell of the second condenser 230. The high pressure, high temperature refrigerant vapor introduced into the shell of the second condenser 230 passes over the exterior of the heat exchange tubes therein in heat exchange relationship with the cooling water passing through the heat exchange tubes, whereby the refrigerant vapor is cooled and condensed to a high pressure refrigerant liquid and the cooling water is heated. The high pressure, condensed refrigerant liquid passes from the second condenser 230 to the second evaporator 240 through a refrigerant passage 211 in which is disposed an expansion device 225.
As the high pressure refrigerant liquid traverses the expansion device 225, the refrigerant liquid expands to a lower pressure and a lower temperature to form, most typically, a saturated mixture of refrigerant liquid and refrigerant vapor at the lower pressure and the lower temperature. The lower pressure, lower temperature liquid/vapor mixture is delivered via the refrigerant passage 211 to and introduced into the shell of the second evaporator 240. The lower temperature refrigerant liquid collects in the shell at least partially immersing the heat exchange tubes of the second evaporator 240. Thus, the chiller water passing through the tubes of the second evaporator 240 passes in heat exchange relationship with the refrigerant introduced into the shell of the second evaporator 240, whereby the refrigerant liquid is heated and evaporated to a refrigerant vapor and the chilled water is cooled. The low pressure, low temperature refrigerant vapor passes from the second evaporator 240 through suction line 226 to return to the suction inlet of the second compressor 220.
In the embodiment depicted in FIG. 4, the heat exchange tubes of the first condenser 130 and of the second condenser 230 are arrayed in a single pass arrangement. Condenser cooling water enters the condenser 230 through the cooling water inlet 33 into an inlet chamber 31 defined within the end cap 234, thence passes serially first through the tubes of the second condenser 230 and thence through the tubes of the first condenser 130 into an outlet chamber 37 defined within the end cap 134 of the first condenser 130. The cooling water passes out of the outlet chamber 37 through the cooling water outlet 35. Thus, with respect to cooling water flow, the second condenser 230, which is part of the second refrigerant circuit 200, constitutes the upstream condenser, and the first condenser 130, which is part of the first refrigerant circuit 100, constitutes the downstream condenser.
The chiller water, that is the water to be chilled, enters the evaporator 40 through the chiller water inlet 45 of the first evaporator 140 and exits the evaporator 40 through the chiller water outlet 43 of the second evaporator 240. Thus with respect to chiller water flow, the first evaporator 140, which is part of the first refrigerant circuit 100, constitutes the upstream evaporator, and the second evaporator 240, which is part of the second refrigerant circuit 200, constitutes the downstream evaporator. Therefore, the chiller water passes through the evaporator 40 in counter flow relationship to the condenser water passing through the condenser 30. In passing from the inlet chamber 41 defined within the end cap 144 of the first evaporator 140 to the outlet chamber 47 defined within the end cap 244 of the second evaporator 240, the chiller water does not traverse a single pass path as in a typical conventional dual circuit chiller.
Rather in the chiller 10 of the invention, the chiller water flowing through the heat exchange tubes of the evaporator 40 traverses a multiple pass path in heat exchange relationship with the refrigerant within the evaporator 40. As depicted in FIGS. 4, 7 and 10, in the chiller 10, a waterbox 50 is provided between the respective tube sheets 42 of the first and second evaporators 140, 240. The waterbox 50 is partitioned by interior walls 52, 54 into three chambers, a first chamber 51, a second chamber 53 and a third chamber 55.
In the embodiments depicted in FIGS. 4 and 10, the heat exchange tubes of the first pass tube bundle 171 of the first evaporator 140 connect the inlet chamber 41 of the evaporator 40 in fluid flow communication with the first chamber 51 of the waterbox 50. The heat exchange tubes of the second pass tube bundle 172 of the first evaporator 140 connect the first chamber 51 of the waterbox 50 in fluid communication with the intermediate chamber 141 of the first evaporator 140. The heat exchange tubes of the third pass tube bundle 173 of the first evaporator 140 connect the intermediate chamber 141 in fluid communication with the second chamber 53 of the waterbox 50. The heat exchange tubes of the first pass tube bundle 271 of the second evaporator 240 connect the intermediate chamber 53 of the waterbox 50 in fluid flow communication with the intermediate chamber 247 of the second evaporator 240. The heat exchange tubes of the second pass tube bundle 272 of the second evaporator 240 connect the intermediate chamber 247 of the second evaporator 140 in fluid communication with the third chamber 55 of the waterbox 50. The heat exchange tubes of the third pass tube bundle 273 of the second evaporator 240 connect the third chamber 55 of the waterbox 50 in fluid communication with the outlet chamber 47 of the second evaporator 240. Thus, in the embodiment depicted in FIGS. 4 and 10, the chiller water passing through the evaporator 40 traverses multiple passes in each of the first and second evaporators 140, 240 in heat exchange relationship with the refrigerant therein.
In the embodiments of the chiller 10 as depicted in FIGS. 7 and 10, a waterbox 60 is also provided between the respective tube sheets 32 of the first and second condensers 130, 230. The waterbox 60 is partitioned by interior walls 62, 64 into three chambers, a first chamber 61, a second chamber 63 and a third chamber 65. Condenser cooling water enters the condenser 30 through the cooling water inlet 33 of the second condenser 230 and exits through the cooling water outlet 35 of the first condenser 130, and traverses a multiple pass path as the cooling water flows through the condenser 30 in heat exchange relationship with the refrigerant.
In this multiple pass arrangement of the condenser 30, as depicted in FIGS. 7 and 10, the heat exchange tubes of the first pass tube bundle 281 of the second condenser 230 connect the inlet chamber 31 of the condenser 30 in fluid flow communication with the first chamber 61 of the waterbox 60. The heat exchange tubes of the second pass tube bundle 282 of the second condenser 230 connect the first chamber 61 of the waterbox 60 in fluid communication with the intermediate chamber 231 of the second condenser 230. The heat exchange tubes of the third pass tube bundle 283 of the second condenser 230 connect the intermediate chamber 231 in fluid communication with the second chamber 63 of the waterbox 60. The heat exchange tubes of the first pass tube bundle 181 of the first condenser 130 connect the intermediate chamber 63 of the waterbox 60 in fluid flow communication with the intermediate chamber 137 of the first condenser 130. The heat exchange tubes of the second pass tube bundle 182 of the first condenser 130 connect the intermediate chamber 137 of the first condenser 130 in fluid communication with the third chamber 65 of the waterbox 60. The heat exchange tubes of the third pass tube bundle 183 of the first condenser 130 connect the third chamber 65 of the waterbox 60 in fluid communication with the outlet chamber 37 of the first condenser 130. Thus, in the embodiment depicted in FIGS. 4 and 8, the cooling water passing through the condenser 30 traverses multiple passes in each of the first and second condensers 130, 230 in heat exchange relationship with the refrigerant therein.
Referring now to FIGS. 7, 9A and 9B, in particular, in the embodiment of the chiller 10 depicted therein, the chiller water enters the evaporator 40 through a first bypass conduit 190 which extends longitudinally from the chiller water inlet through the first evaporator 140 to open in fluid communication with the first chamber 51 of the waterbox 50. The chiller water exits the evaporator 40 through a second bypass conduit 290 which extends longitudinally through the second evaporator 240 in fluid communication with the third chamber 55 of the waterbox 50 to the chiller water outlet. Between the first chamber 51 of the waterbox 50 and the third chamber of the waterbox 50, the chiller water flows through a two-pass heat exchanger in the first evaporator 140, through the second chamber 53 of the waterbox 50, and thence through a two-pass heat exchanger in the second evaporator 240. The heat exchange tubes of the second pass tube bundle 172 of the first evaporator 140 connect the first chamber 51 of the waterbox 50 in fluid communication with the intermediate chamber 141 of the first evaporator 140. The heat exchange tubes of the third pass tube bundle 173 of the first evaporator 140 connect the intermediate chamber 141 in fluid communication with the second chamber 53 of the waterbox 50. The heat exchange tubes of the first pass tube bundle 271 of the second evaporator 240 connect the intermediate chamber 53 of the waterbox 50 in fluid flow communication with the intermediate chamber 247 of the second evaporator 240. The heat exchange tubes of the second pass tube bundle 272 of the second evaporator 240 connect the intermediate chamber 247 of the second evaporator 240 in fluid communication with the third chamber 55 of the waterbox 50.
Thus, in the embodiment depicted in FIG. 7, the chiller water passing through the evaporator 40 traverses two passes in each of the first and second evaporators 140, 240 in heat exchange relationship with the refrigerant therein, rather than three passes as in the embodiments depicted in FIGS. 4 and 10. Therefore, the chiller water in passing through the first evaporator 140 upon entering the evaporator 40 by way of the bypass conduit 190 in effect bypasses a tube bundle prior to entering the first chamber 51 of the waterbox 50 and in passing through the second evaporator 240 by way of bypass conduit 290 in effect bypasses another tube bundle after leaving the third chamber 55 of the waterbox 50 upon exiting the evaporator 40. Since the bypass conduits 190, 290, provide a direct water flow path, respectively, between the chiller water inlet 45 and the first chamber 51 of the waterbox 50 and between the third chamber 55 of the waterbox 50 and the chiller water outlet 43, and since the bypass conduits 190, 290 have a very large inside diameter as compared to the inside diameters of the individual heat exchange tubes of a tube bundle, the waterside pressure drop through the evaporator 40 of the FIG. 7 embodiment is significantly reduced as compared to the waterside pressure drop associated with passing through three tube bundle passes as in the evaporator 40 of the embodiments depicted in FIGS. 7 and 10. The use of bypass conduits 190, 290 for receiving chiller water directly into the evaporator waterbox 50 and for discharging chiller water directly from the evaporator water box 50, respectively, enables the bypass conduit 190 to be connected directly to a customer's chiller water retune pipe (not shown) and the bypass conduit 290 to be connected directly to a customer's chilled water supply pipe (not shown). In this embodiment, because the bypass conduits 190 and 290 do not open into or pass through the respective end waterboxes 48, the heat exchanger tubes of the tube bundles 172, 173, 271, 272 may be accessed for servicing and removal, if necessary, simply by removing the cover of the appropriate end waterbox, without disconnecting the evaporator from the customer's chiller water system.
In the embodiment of the dual refrigerant circuit chiller 10 depicted in FIG. 4, each of the condensers 130, 140 has a single pass cooling waterside circuit and each of the evaporators 140, 240 has a three pass chiller waterside circuit. In the embodiment of the dual refrigerant circuit chiller 10 depicted in FIG. 7, each of the condensers 130, 230 has a three pass cooling waterside circuit and each of the evaporators 140, 240 has a two pass chiller waterside circuit. In the embodiment of the dual refrigerant circuit chiller 10 depicted in FIG. 10, each of the condensers 130, 230 has a three pass cooling waterside circuit and each of the evaporators 140, 240 has a three pass chiller waterside circuit. In each of these configurations, the cooling water enters the condenser 30 through one end cap and leaves the condenser 30 through its other end cap. Similarly, the chiller water enters the evaporator 40 through one end cap and leaves the evaporator 40 through its other end cap. In this manner, the series counterflow relationship between the condensing water flow and the chiller water flow is maintained, even though the chiller water circuit arrangement in the evaporator is multiple pass. Additionally, on the condenser side, the cooling waterside circuit may be single pass or multiple pass while still maintaining a series flow arrangement through the condenser.
Referring now to FIGS. 12-18, in particular, in the embodiment of the evaporator 40 of chiller 10 depicted therein, the heat exchange tubes of the first pass tube bundle 371 of the first evaporator 140 connect the inlet chamber 341 of the first evaporator 140 in fluid flow communication with the first chamber 151 of the waterbox 150. The heat exchange tubes of the second pass tube bundle 372 of the first evaporator 140 connect the first chamber 151 of the waterbox 150 in fluid communication with the intermediate chamber 343 of the end cap of first evaporator 140. The heat exchange tubes of the bypass tube 390 of the first evaporator 140 connects the intermediate chamber 343 in fluid communication with the second chamber 153 of the waterbox 150. The heat exchange tubes of the first pass tube bundle 274 of the second evaporator 240 connect the second chamber 153 of the waterbox 150 in fluid flow communication with the intermediate chamber 345 of the end cap of the second evaporator 240. The heat exchange tubes of the second pass tube bundle 375 of the second evaporator 240 connect the intermediate chamber 345 of the second evaporator 240 in fluid communication with the third chamber 155 of the waterbox 150. The heat exchange tubes of the bypass conduit 690 of the second evaporator 240 connect the third chamber 155 of the waterbox 150 in fluid communication with the outlet chamber 347 of the second evaporator 240.
In this embodiment, the waterbox 150, as illustrated in FIGS. 12 and 17, provides for passage of the chiller water through the second chamber 153 in a generally vertical flow. Thus, the chiller water enters an upper region of the second chamber 153 from the bypass conduit 390 of the first evaporator 140 and leaves the waterbox 150 at a lower region of the second chamber 153 to enter the first pass tube bundle 374 of the second evaporator 240. Therefore, in transitioning through the waterbox 150 from the first evaporator 140 to the second evaporator 240, the chiller water is delivered to the lower pass tube bundle 374 of the second evaporator 240. An alternate embodiment of the waterbox 150 providing for vertical passage of the chiller water in transitioning from the first evaporator 140 to the second evaporator 240 is depicted in FIG. 18. As depicted, a pair of internal walls 152 sections the interior of the water box 150 into a first chamber 151, a second chamber 153 and a third chamber 155. The respective tube bundle passes 371, 372, 374, 375 and bypass conduits 390, 690 open into the waterbox 150 as described above with respect to FIG. 12, with the second chamber 153 providing the for the vertical transition.
Referring now to FIGS. 19-25, in particular, in the embodiment of the evaporator of chiller 10 depicted therein, the chiller water enters the evaporator 40 through a first bypass conduit 490 which extends longitudinally from the chiller water inlet through the first evaporator 140 to open in fluid communication with the first chamber 251 of the waterbox 250. The chiller water exits the evaporator 40 through a second bypass conduit 590 which extends longitudinally through the second evaporator 240 in fluid communication with the third chamber 255 of the waterbox 250 to the chiller water outlet. Between the first chamber 251 of the waterbox 250 and the third chamber 255 of the waterbox 250, the chiller water flows through a two-pass heat exchanger in the first evaporator 140, through the second chamber 253 of the waterbox 250, and thence through a two-pass heat exchanger in the second evaporator 240. The heat exchange tubes of the second pass tube bundle 472 of the first evaporator 140 connect the first chamber 251 of the waterbox 250 in fluid communication with the end waterbox 448 of the first evaporator 140. The heat exchange tubes of the third pass tube bundle 473 of the first evaporator 140 connect the end waterbox 448 in fluid communication with the second chamber 253 of the waterbox 250. The heat exchange tubes of the first pass tube bundle 474 of the second evaporator 240 connect the intermediate chamber 253 of the waterbox 250 in fluid flow communication with the end waterbox 448 of the second evaporator 240. The heat exchange tubes of the second pass tube bundle 475 of the second evaporator 240 connect the end waterbox 448 of the second evaporator 240 in fluid communication with the third chamber 255 of the waterbox 250.
In the embodiment of the evaporator of chiller 10 depicted in FIG. 19, the bypass conduits 490, 590 do not open into or pass through the respective end waterboxes 448, but rather pass from the evaporator 40 externally of the end waterboxes 448 in like manner to the bypass conduits 190, 290 shown in the FIG. 7 embodiment of the chiller 10. Thus, as discussed hereinbefore with respect to the FIG. 7 embodiment, the heat exchange tubes of the various tube bundles within the evaporator 40 may be serviced and removed, if necessary, simply by removing the cover to the appropriate end waterbox 448, without disconnecting the evaporator 40 from the customer's chiller water system. It is to be understood that the condenser 30 may also be constructed in similar manner as discussed with reference to the evaporators 40 as depicted in FIG. 12 and FIG. 19.
It is to be understood that for purposes of simplifying the drawings, each of the tube bundles of the tube-in-shell heat exchangers in the condensers and evaporator are represented in FIGS. 4, 7, 10, 12 and 19 as a single tube to illustrate the flow path of the water and are illustrated in outline in the cross-sections shown in FIGS. 5, 6, 8, 13, 14, 15, 16, 21, 22, 23 and 24. In reality, each tube bundle 171, 172, 173, 271, 272, 273, 281, 282, 283, 371, 372, 374, 375, 472, 473, 474, 475, comprises a large number of individual heat exchange tubes, typically numbering in the hundreds, extending in parallel relationship between the tube sheets of each condenser and each evaporator, for example as depicted with respect to tube bundles 172, 173, 271, 272 in FIGS. 9A and 9B. Each bypass conduit 190, 290, 390, 490, 590, 690 defines a large flow area fluid passages relative to the flow area defined by an individual tube of the tube bundles.
Although the chiller 10 has been described herein with reference to water as the condenser cooling fluid and water as the circuit fluid to be chilled, it is to be recognized by those skilled in the art that fluids other than water may be used as the circuit fluid and/or the cooling fluid in the dual refrigerant circuit chiller described hereinabove and in the appended claims. As an example, in an embodiment, the circuit fluid may be chiller brine.
The terminology used herein is for the purpose of description, not limitation. Specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as basis for teaching one skilled in the art to employ the present invention. While the present invention has been particularly shown and described with reference to the exemplary embodiments as illustrated in the drawing, it will be recognized by those skilled in the art that various modifications may be made without departing from the spirit and scope of the invention. Those skilled in the art will also recognize the equivalents that may be substituted for elements described with reference to the exemplary embodiments disclosed herein without departing from the scope of the present invention.
Therefore, it is intended that the present disclosure not be limited to the particular embodiment(s) disclosed as, but that the disclosure will include all embodiments falling within the scope of the appended claims.

Claims

1. A dual refrigerant circuit chiller comprising:

a first refrigerant circuit including a first condenser and a first evaporator;

a second refrigerant circuit including a second condenser and a second evaporator,

a condenser assembly including the first condenser and the second condenser interconnected in a series cooling fluid circuit, the condenser assembly having a cooling fluid inlet in fluid communication with the second condenser and a cooling fluid outlet in fluid communication with the first condenser; and

an evaporator assembly including the first evaporator and the second evaporator interconnected in a series fluid circuit and a waterbox disposed intermediate the first evaporator and the second evaporator, the evaporator assembly having a circuit fluid inlet in fluid communication with the first evaporator and a circuit fluid outlet in fluid communication with the second evaporator, the first evaporator having a multiple pass circuit fluid-to-refrigerant heat exchanger having an outlet in fluid communication with the waterbox and an inlet in fluid communication with the circuit fluid inlet of the evaporator assembly, the second evaporator having a multiple pass circuit fluid-to-refrigerant heat exchanger having an inlet in fluid communication with the waterbox and an outlet in fluid communication with the circuit fluid outlet of the evaporator assembly, the circuit fluid inlet and the circuit fluid outlet disposed at opposite longitudinal ends of the evaporator assembly.

2. The dual refrigerant circuit chiller as recited in claim 1 wherein the circuit fluid-to-refrigerant heat exchanger of the first evaporator and the circuit fluid-to-refrigerant heat exchanger of the second evaporator each comprise a three pass tube bundle heat exchanger.

3. The dual refrigerant circuit chiller as recited in claim 1 wherein the cooling fluid is cooling water and the circuit fluid is chiller water.

4. The dual refrigerant circuit chiller as recited in claim 1 wherein the condenser assembly includes a waterbox disposed intermediate the first condenser and the second condenser, a multiple pass cooling fluid-to-refrigerant heat exchanger in the second condenser having an outlet in fluid communication with the waterbox and an inlet in fluid communication with the cooling fluid inlet of the condenser assembly, and a multiple pass cooling fluid-to-refrigerant heat exchanger in the first condenser having an inlet in fluid communication with the waterbox and an outlet in fluid communication with the cooling fluid outlet of the condenser assembly, the cooling fluid inlet and the cooling fluid outlet disposed at opposite longitudinal ends of the condenser assembly.

5. The dual refrigerant circuit chiller as recited in claim 1 wherein the evaporator assembly further includes a first bypass conduit having an inlet in fluid communication with the circuit fluid inlet of the evaporator assembly and an outlet in fluid communication with a first chamber of the waterbox, and wherein the multiple pass circuit fluid-to-refrigerant heat exchanger of the first evaporator has an inlet in fluid communication with the first chamber of the waterbox and an outlet in fluid communication with a second chamber of the waterbox.

6. The dual refrigerant circuit chiller as recited in claim 5 wherein the evaporator assembly further includes a second bypass conduit having an outlet in fluid communication with the circuit fluid outlet of the evaporator assembly and an inlet in fluid communication with a third chamber of the waterbox, and wherein the multiple pass circuit fluid-to-refrigerant heat exchanger of the second evaporator has an inlet in fluid communication with the second chamber of the waterbox and an outlet in fluid communication with a third chamber of the waterbox.

7. A dual refrigerant circuit chiller comprising:

a first refrigerant circuit including a first condenser and a first evaporator;

an evaporator assembly including the first evaporator and the second evaporator interconnected in a series fluid circuit and a waterbox disposed intermediate the first evaporator and the second evaporator, the waterbox having a first chamber, a second chamber and a third chamber, the evaporator assembly having:

a circuit fluid inlet and the circuit fluid outlet disposed at opposite longitudinal ends of the evaporator assembly;

a first bypass conduit having an inlet in fluid communication with the circuit fluid inlet of the evaporator assembly and an outlet in fluid communication with the first chamber of the waterbox;

a first multiple pass circuit fluid-to-refrigerant heat exchanger disposed in the first evaporator having an inlet in fluid communication with the first chamber of the waterbox and an outlet in fluid communication with the second chamber of the waterbox;

a second bypass conduit having an outlet in fluid communication with the circuit fluid outlet of the evaporator assembly and an inlet in fluid communication with the third chamber of the waterbox;

a second multiple pass circuit fluid-to-refrigerant heat exchanger of the second evaporator has an inlet in fluid communication with the second chamber of the waterbox and an outlet in fluid communication with the third chamber of the waterbox.

8. The dual refrigerant circuit chiller as recited in claim 7 wherein the circuit fluid-to-refrigerant heat exchanger of the first evaporator and the circuit fluid-to-refrigerant heat exchanger of the second evaporator each comprise a two pass tube bundle heat exchanger.

9. The dual refrigerant circuit chiller as recited in claim 7 wherein the cooling fluid is cooling water and the circuit fluid is water.

10. The dual refrigerant circuit chiller as recited in claim 7 wherein the cooling fluid is cooling water and the circuit fluid is brine.

11. The dual refrigerant circuit chiller as recited in claim 7 wherein the condenser assembly includes a waterbox disposed intermediate the first condenser and the second condenser, a multiple pass cooling fluid-to-refrigerant heat exchanger in the second condenser having an outlet in fluid communication with the waterbox and an inlet in fluid communication with the cooling fluid inlet of the condenser assembly, and a multiple pass cooling fluid-to-refrigerant heat exchanger in the first condenser having an inlet in fluid communication with the waterbox and an outlet in fluid communication with the cooling fluid outlet of the condenser assembly, the cooling fluid inlet and the cooling fluid outlet disposed at opposite longitudinal ends of the condenser assembly.

12. The dual refrigerant circuit chiller as recited in claim 7 wherein the cooling fluid is cooling water and the circuit fluid is brine.

13. The dual refrigerant circuit chiller as recited in claim 1 wherein the intermediate waterbox is sectioned into a first chamber, a second chamber, and a third chamber.

14. The dual refrigerant circuit chiller as recited in claim 1 wherein the second chamber of the intermediate waterbox provides a generally vertical flow passage through the waterbox.

15. The dual refrigerant circuit chiller as recited in claim 7 wherein the first bypass conduit extends externally of the evaporator assembly at a first end of the evaporator assembly for connection to a fluid line for receiving circuit fluid and the second bypass conduit extends externally of the evaporator assembly at a second end of the evaporator assembly for connection to a fluid line for discharging circuit fluid.

16. The dual refrigerant circuit chiller as recited in claim 7 wherein the condenser assembly includes:

a waterbox disposed intermediate the first condenser and the second condenser, the waterbox having a first chamber, a second chamber, and a third chamber;

a first bypass conduit having an inlet in fluid communication with the cooling fluid inlet of the condenser assembly and an outlet in fluid communication with the first chamber of the waterbox;

a first multiple pass cooling fluid-to-refrigerant heat exchanger disposed in the second condenser having an inlet in fluid communication with the first chamber of the waterbox and an outlet in fluid communication with the second chamber of the waterbox;

a second bypass conduit having an outlet in fluid communication with the cooling fluid outlet of the condenser assembly and an inlet in fluid communication with the third chamber of the waterbox;

a second multiple pass cooling fluid-to-refrigerant heat exchanger disposed in the first condenser having an inlet in fluid communication with the second chamber of the waterbox and an outlet in fluid communication with the third chamber of the waterbox.

17. The dual refrigerant circuit chiller as recited in claim 16 wherein the first bypass conduit extends externally of the condenser assembly at a first end of the condenser assembly for receiving cooling fluid and the second bypass conduit extends externally of the condenser assembly at a second end of the condenser assembly for discharging cooling fluid.