US20200340748A1

US20200340748A1 - Ultra narrow channel ultra low refrigerant charge evaporative condenser

Info

Publication number: US20200340748A1
Application number: US16/840,843
Authority: US
Inventors: Thomas Bugler; Trevor Hegg
Original assignee: Evapco Inc
Current assignee: Evapco Inc
Priority date: 2016-07-22
Filing date: 2020-04-06
Publication date: 2020-10-29

Abstract

A tube bundle for an evaporative refrigerant condenser having a plurality of straight single pass tubes extending between a refrigerant inlet header and a refrigerant outlet header, said tubes having a cross-sectional shape in the form of an ellipse having a major axis and a minor axis, wherein said major axis is longer than said minor axis by a factor of 3 to 7, wherein the amount of required refrigerant charge for a particular heat exchange capacity is substantially and unexpectedly reduced resulting in a substantial and unexpected increase in efficiency.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to evaporative condensers and coolers.

Description of the Background

In certain cooling/refrigeration system, evaporative condensers receive superheated refrigerant gas from a cooling/refrigeration system compressor and cool/condense it to refrigerant liquid, which condensed refrigerant liquid is then return to a cooling/refrigeration system evaporator for cooling/refrigeration of a desired space. The evaporative condensers include a series of round or slightly elliptical serpentine tubes through which the refrigerant passes. Water is flowed over the tubes containing the refrigerant, allowing heat to be transferred from the refrigerant to the water via indirect heat exchange and causing the superheated refrigerant gas to condense to liquid. The heated water in turn is cooled by direct heat exchange with ambient air as the water and ambient air pass over the tubes and/or through fill material.

SUMMARY OF THE INVENTION

The present invention is a new design for evaporative refrigerant condensers including an indirect refrigerant condensing tube bundle heat exchanger with single pass (no serpentine) extremely narrow elliptical tubes (ratios of tube height to tube width of 3:1 to 16:1) to increase the refrigerant velocity (void fraction). For example, for a nominal tube diameter 1″ round tube, the preferred tube width of the tubes of the invention is approximately 0.1 inches to 0.5 inches, outside diameter, with tube height about 1.4 inches to 1.6 inches, outside diameter (vertical axis of ellipse). Similarly, at the other end of nominal tube diameter spectrum, for a nominal diameter ¼″ round tube, the preferred tube width of the tubes of the invention is approximately 0.025 inches to 0.125 inches, outside diameter, with tube height about 0.3 inches to 0.4 inches, outside diameter (vertical axis of ellipse).
Each single pass tube terminates at one end at an inlet refrigerant header and at the other end at an outlet refrigerant header. The tubes may be galvanized or stainless steel. The tubes may be provided with a flared inlet to reduce inlet refrigerant pressure loss. According to a preferred embodiment, tube spacing may be approximately 0.5 inches to 0.75 inches, center to center. According to another embodiment, each tube may be offset vertically relative to adjacent tubes to reduce air dP loss so that adjacent tubes nest into one-another.
This design reduces the cross sectional refrigerant flow area significantly, thus significantly reducing the required refrigerant charge, while maintaining the external heat exchange surface and thus heat exchange capacity, resulting in an unexpected increase in efficiency of more than 20% relative to the same device with serpentine elliptical tubes.
According to a first embodiment of the invention, the refrigerant condensing tube bundle of the invention may be substituted for the serpentine coil from a standard evaporative closed circuit cooler/condenser.
According to another embodiment of the invention, the refrigerant condensing tube bundle described above may be combined with (placed into) an otherwise standard counterflow direct evaporative cooling tower to create a new type of evaporative refrigerant condenser/cooling tower. According to various alternative embodiments, the tube bundle may be used as the structural support for fill, supporting various amounts of fill height, for example, but not limited to, 6 inches, 1′, 1.5′, 2′, 2.5′, 3′, 3.5′, 4′ or more of film fill height, or any amounts in between. According to these tube-bundle-as-fill-support embodiments, the bottom fill bundles should preferably be run perpendicular to the condenser tubes for best water distributions on the tubes. Standard cooling tower nozzle arrangements may be used with water flow rates as low as 2 gpm/sf, with preferable amounts of 4 gpm/sf to 10 gpm/sf, and more preferably from around 5 gpm/sf to 7 gpm/sf.
According to some embodiments, the tubes in the tube bundle may have a slight slope from horizontal to allow for drainage of liquid refrigerant.
According to various different embodiments of lengths of the tubes of the tube bundle may run either long or short way across the tower depending on thermal and refrigerant load.
According to an alternative embodiment, the tube bundle of the invention may be used in a counterflow closed circuit cooler arrangement in which the fan, water distribution nozzles, heat and mass exchange fill and air inlets are all positioned above a water redistribution basin, which in turn is positioned above a closed circuit cooler coil of the invention. This embodiment produces a substantial reduction in height due to the lack of serpentine tube bends in the tube bundle of the invention. The tube spacing of the present invention used in a counterflow closed circuit cooler can be much tighter with less space between tubes, since only water and no air needs to flow between tubes.
According to further alternative counterflow embodiments, the coil bundle of the invention may be located just above the fill and below the spray nozzles.
According to further embodiments, the tube bundle of the invention may be used with various crossflow arrangements. According to one such embodiment, the tube bundle is located above the crossflow fill and below the nozzle distribution system and air flows downward through the tubes before exiting to the fan plenum. According to another such embodiment, the tube bundles of the invention may be located above, below and in the middle of the crossflow fill. According to this embodiment, no air passes over the tubes, only water, as the cooled water flows from one fill section down to the next.
A more detailed description of the invention is set forth below with reference to the following figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a tube according to an embodiment of the invention.

FIG. 2 is a cross-sectional view of a tube according to another embodiment of the invention.

FIG. 3 is a perspective view of a tube bundle according to an embodiment of the invention

FIG. 4 is a top/overhead view of the embodiment shown in FIG. 3.

FIG. 5 is a side view of the embodiment shown in FIGS. 3 and 4.

FIG. 6 is an end view of the embodiment shown in FIGS. 3-5.

FIG. 7A is a representation of a prior art closed circuit cooler/condenser with serpentine coil.

FIG. 7B is a representation of a closed circuit cooler/condenser with an ultra-narrow elliptical tube bundle according to an embodiment of the invention.

FIG. 8A is a representation of a prior art counterflow direct evaporative cooling tower.

FIG. 8B is a representation of a counterflow indirect evaporative refrigerant condenser/cooling tower according to an embodiment of the invention.

FIG. 8C is a representation of different counterflow indirect evaporative refrigerant condenser/cooling tower according to an embodiment of the invention.

FIG. 9A is a representation of a prior art closed circuit cooler.

FIG. 9B is a representation of closed circuit cooler according to an embodiment of the invention.

FIG. 10A is a representation of a prior art induced draft evaporative condenser/cooler.

FIG. 10B is a representation of an induced draft evaporative condenser/cooler according to an embodiment of the invention.

FIG. 10C is a representation of another embodiment according to the invention.

FIG. 10D is a representation of a further embodiment according to the invention.

FIG. 10E is a representation of yet another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a cross-section of a condenser tube according to an embodiment of the invention. As shown in FIG. 1, the tubes of the invention are formed in the shape of an extreme ellipse, with the major axis of the tube at least 3× the minor axis. According to preferred embodiments, the height of the tube (major axis) is at least 1.4 inches (outer diameter), and the width of the tube (minor axis) is no greater than 0.5 inches (outer diameter). A preferred embodiment is shown in FIG. 2, in which the ratio of the major axis to the minor axis is 6.4:1. According to further preferred embodiments, the minor axis may be 0.1 inches to 0.25 inches, and the major axis may be 1.4 inches to 1.6 inches with ratios of major axis to minor axis of 3:1 to 16:1.
Referring to FIGS. 3-6, the tubes of the invention may be arranged in rows of parallel single pass tubes, each tube running from an inlet header to an outlet header. The embodiment shown in FIGS. 3-6 shows multiple inlet and outlet headers, with each row of tubes having its own set of headers. According to an alternative embodiment, a single header may be provided at each end of the bundle, with all tubes from all rows terminating at one end at a single inlet header, and terminating at the other end at a single outlet header.
In either case, the lack of return bends as in the prior art serpentine tubes substantially reduces the height of the tube bundle for the same capacity. Horizontal tube spacing is preferably 0.5 inches to 0.75 inches, center to center. The spacing between adjacent tube sides is preferably 0.25 to 0.65 inches. Vertical tube spacing is preferably 0.5 inches to 2.0 inches, center to center.
FIG. 7B shows a closed circuit cooler/condenser in which the prior art serpentine coil has been replaced with an ultra-narrow elliptical tube bundle according to to embodiment of the invention. Standard cooling tower nozzles distribute water over the ultra-narrow elliptical tube bundle of the invention, and the water collects in a basin at the bottom of the device from which it is pumped back to the nozzles. Ambient air is drawn into the plenum of the device at the bottom under the action of a fan and is drawn up through the tube bundle to exit the device from the top.
FIG. 8B shows a counterflow indirect evaporative refrigerant condenser/cooling tower according to an embodiment of the invention in which a refrigerant condensing tube bundle according to the invention has been placed into a standard counterflow direct evaporative cooling tower. As shown in FIG. 8B, the tube bundle can act as the structural support for the fill, the sheets of which run perpendicular to the condenser tubes. Standard cooling tower nozzles distribute water over the fill, and the water collects in a basin at the bottom of the device from which it is pumped back to the nozzles. Ambient air is drawn into the plenum of the device at the bottom under the action of a fan and is drawn up through the tube bundle and the fill to exit the device from the top. According to the embodiment shown in FIG. 8B, the tubes run parallel to the longitudinal axis of the tower. FIG. 8C shows an embodiment in which the tubes run perpendicular to the longitudinal axis of the tower.
FIG. 9B shows the tube bundle of the invention in an open cooling tower embodiment having a closed circuit water-to-fluid heat exchanger below. As shown in FIG. 9B, the tube bundle is located at the bottom of the device, and air is drawn into a plenum of the device through side openings located above the tube bundle. Air is drawn through the fill and forced out through the top of the device. Spray nozzles from a water distribution system spray water over the fill. The water is collected in a tray and then redistributed over the tube bundle, cooling the fluid therein via indirect heat exchange. The water collects in a basin at the bottom of the devices and is then pumped back to the spray nozzles. Since no air is directed over the tubes, the tube spacing can be much tighter, and the tube bundle of the present invention allows for much tighter spacing with the extreme elliptical shape and the lack of return bends.
FIG. 10B shows a tube bundle according to the invention in an induced draft evaporative condenser unit with crossflow fill. The tube bundle is located directly beneath the spray nozzles of the water distribution system, and the fill is located below the tube bundle. Air enters the device through the sides at the bottom, adjacent the fill, as well as through the top above the tube bundle. Air flows downward through the tubes before exiting to the fan plenum. Water flows over the tube bundle and then over the fill to collect in the basin, from which it is pumped back to the water distribution system.
According to further embodiments, the tube bundles of the invention may be located above (FIG. 10C), below (FIG. 10D) and/or in the middle (FIG. 10E) of the crossflow fill. According to these embodiments, only water is directed over the tubes, and no air flow is directed over the tubes.
Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It should be understood, therefore, that the invention may be practiced otherwise than as specifically set forth herein.

Claims

1. A tube bundle for an evaporative refrigerant condenser comprising a refrigerant inlet header, a refrigerant outlet header, and a plurality of straight single pass tubes extending between said refrigerant inlet header and said refrigerant outlet header, said tubes having a cross-sectional shape in the form of an ellipse having a major axis and a minor axis, wherein said major axis has a length of 1.4 inches to 1.7 inches, measured at an outside surface of the tubes, and wherein said minor axis has a width of 0.1 inches to 0.25 inches, measured at an outside surface of the tubes.

2. (canceled)

3. (canceled)

4. (canceled)

5. The tube bundle according to claim 1, wherein each tube is spaced from each horizontally adjacent tube by 0.5 inches to 0.75 inches, measured from the center of each tube.

6. The tube bundle according to claim 1, wherein each tube is spaced from each vertically adjacent tube by 0.5 inches to 2.0 inches, measured from the center of each tube.

7. An evaporative refrigerant condenser or closed circuit fluid cooler comprising:

a housing;

a fan located near a top of said housing to draw air into said housing and force it through said top of said housing;

a water distribution system, including a pump and water distribution nozzles, said water distribution nozzles located beneath said fan;

a tube bundle located beneath said fan, said tube bundle comprising a refrigerant inlet header, a refrigerant outlet heater, and a plurality of straight single pass tubes extending between said refrigerant inlet header and said refrigerant outlet header, said tubes having a cross-sectional shape in the form of an ellipse having a major axis and a minor axis, wherein said major axis has a length of 1.4 inches to 1.7 inches, measured at an outside surface of the tubes and wherein said minor axis has a width of 0.1 inches to 0.25 inches, measured at an outside surface of the tubes;

a plenum located beneath said tube bundle,

a water basin located at a bottom of said plenum for collecting water distributed from said water distribution system;

said pump configured to draw water from said water basin and force it through said water distribution nozzles;

an air inlet on at least one side of said housing adjacent said plenum to allow entry of air drawn by said fan.

8. The evaporative refrigerant condenser or closed circuit fluid cooler according to claim 7, further comprising a direct heat exchange fill located between said water distribution nozzles for facilitating direct heat exchange between said air and said water.

9. The evaporative refrigerant condenser or closed circuit fluid cooler according to claim 7, wherein said direct heat exchange fill rests directly on said tube bundle, and said tube bundle provides structural support for said direct heat exchange fill.

10. A counterflow closed circuit cooler or refrigerant condenser comprising:

a housing;

a direct heat exchange fill located beneath said water distribution nozzles for facilitating direct heat exchange between said air and said water;

a plenum located beneath said direct heat exchange fill,

a redistribution basin located beneath said plenum and configured to collect water distributed from said water distribution nozzles and redistributed it to a lower portion of said housing;

a tube bundle located beneath said redistribution basin, said tube bundle comprising a refrigerant inlet header, a refrigerant outlet heater, and a plurality of straight single pass tubes extending between said refrigerant inlet header and said refrigerant outlet header, said tubes having a cross-sectional shape in the form of an ellipse having a major axis and a minor axis, wherein said major axis is longer than said minor axis by a factor of 3 to 10;

a water basin located at a bottom of said housing for collecting water distributed from said water distribution system;

an air inlet on a side of said housing adjacent said plenum to allow entry of air drawn by said fan.

11. An induced draft evaporative condenser or closed circuit cooler comprising:

a housing;

a water distribution system, including a pump and water distribution nozzles, said water distribution nozzles located adjacent said fan;

a tube bundle located beneath said water distribution nozzles, said tube bundle comprising a refrigerant inlet header, a refrigerant outlet heater, and a plurality of straight single pass tubes extending between said refrigerant inlet header and said refrigerant outlet header, said tubes having a cross-sectional shape in the form of an ellipse having a major axis and a minor axis, wherein said major axis is longer than said minor axis by a factor of 3 to 10;

a direct heat exchange fill located beneath said tube bundle for facilitating direct heat exchange between said air and said water;

a plenum located beneath said fan,

an air inlet on a bottom side of said housing adjacent said fill to allow entry of air drawn by said fan.