# US 10,480,872 B2 · Turbulators in enhanced tubes

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- Number: US 10,480,872 B2
- Document ID: US10480872B2
- Status: Granted
- Kind: B2
- Application number: 14/852,893
- Filed: 2015-09-14
- Published: 2016-03-17
- Granted: 2019-11-19
- Earliest claimed: 2014-09-12
- Assignees: Trane International Inc.
- Applicants: Trane International Inc.
- Inventors: H. Kenneth Ring, Jr.; Jon P. Hartfield; Todd A. Michael
- Web page: https://patentgrep.com/patent/US10480872B2

## CPC

- F28F 13/12: by creating turbulence, e.g. by stirring, by increasing the force of circulation (F28F13/08 takes precedence)
- F25B 39/02: Evaporators
- F28F 1/405: {and being formed of wires}
- F28F 1/422: {with outside means integral with the tubular element and inside means integral with the tubular element (F28F1/424 takes precedence)}
- F28F 13/187: {especially adapted for evaporator surfaces or condenser surfaces, e.g. with nucleation sites}
- F25B 2339/0242: having tubular elements
- F25B 2339/047: Water-cooled condensers
- F25B 2500/09: Improving heat transfers
- F28D 2021/0071: {Evaporators}
- F28F 2001/428: {Particular methods for manufacturing outside or inside fins}
- F28F: DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION (water and air traps, air venting F16)
- F25B: REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F28D: HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT (fluid heaters having heat generating means and heat transferring means F24H; furnaces F27; details of heat-exchange apparatus of general)

## Abstract

A heat exchange tube combines an external surface feature, for example having crushed fins and cavities, which can have very high boiling enhancement characteristics, with an internal surface feature, for example having high performing intersecting helices, e.g. “cross hatched” with an intersecting helix angle. The new tube can provide a high performing tube in a shell and tube evaporator that can be relatively smaller, more efficient, and that can use relatively lower refrigerant charge.

## Claims

### Claim 1

A heat exchange tube comprising:
inner surface features on an inner surface of the heat exchange tube including a rib structure that is rifled and includes two or more helices that cross over each other; and
a turbulator that extends in a longitudinal direction inside the heat exchange tube,
at least a portion of the turbulator is positioned on the inner surface features,
the inner surface features and the turbulator have a relative structure and arrangement to synergistically improve a heat transfer coefficient relative to a heat exchange tube without both the inner surface features and the turbulator, and in an operation condition where the working fluid flow is in an intermediate regime, and
the intermediate regime is defined as including Reynolds numbers including lower than a transition point before a turbulent flow regime, including the transition point, and including a relatively smaller portion of the turbulent flow regime,
wherein a ratio of turbulator pitch P1 to a tube inner diameter Dt, P1/Dt, is from 1 to 2.5, and
a ratio of a turbulator diameter Dw to the tube inner diameter Dt, Dw/Dt, is from 0.04 to 0.1.

### Claim 2 (depends on 1)

The heat exchange tube of claim 1, wherein the operation condition includes temperature applications at or below 32° F., and the transition point is a Reynolds number of 8000.

### Claim 3 (depends on 1)

The heat exchange tube of claim 1, further comprising a ratio of turbulator pitch P1 to a pitch P2, the pitch P2 being a distance between two neighboring surface features in a longitudinal direction of the heat exchange tube, where the ratio P1/P2 is about 2 or 3.

### Claim 4 (depends on 1)

The heat exchange tube of claim 1, further comprising outer surface features on an outer surface of the heat exchange tube.

### Claim 5 (depends on 1)

The heat exchange tube of claim 1, wherein the turbulator is made of metal, is non-corrosive, is compatible with a material of the heat exchange tube, and is non-dissolvable with the working fluid.

### Claim 6 (depends on 1)

The heat exchange tube of claim 1, wherein the turbulator is made of copper.

### Claim 7

A fluid chiller comprising:
a heat exchanger including a shell with an internal volume; and
multiple heat exchange tubes disposed within the internal volume of the shell,
one or more of the multiple heat exchange tubes comprise
inner surface features on an inner surface of the heat exchange tube including a rib structure that is rifled and includes two or more helices that cross over each other; and
a turbulator that extends in a longitudinal direction inside the heat exchange tube,
at least a portion of the turbulator is positioned on the inner surface features,
the inner surface features and the turbulator have a relative structure and arrangement to synergistically improve a heat transfer coefficient relative to a heat exchange tube without both the inner surface features and the turbulator, and in an operation condition where the working fluid flow is in an intermediate regime, and
the intermediate regime is defined as including Reynolds numbers including lower than a transition point before a turbulent flow regime, including the transition point, and including a relatively smaller portion of the turbulent flow regime,
wherein a ratio of turbulator pitch P1 to a tube inner diameter Dt, P1/Dt, is from 1 to 2.5, and
a ratio of a turbulator diameter Dw to the tube inner diameter Dt, Dw/Dt, is from 0.04 to 0.1.

### Claim 8 (depends on 7)

The fluid chiller of claim 7, wherein the heat exchanger is structured and arranged as a single pass shell and tube heat exchanger.

### Claim 9

A method of making a heat exchange tube comprising:
providing inner surface features on an inner surface of the heat exchange tube including a rib structure that is rifled and includes two or more helices that cross over each other; and
providing a turbulator that extends in a longitudinal direction inside the heat exchange tube,
positioning at least a portion of the turbulator on the inner surface features; and
arranging the inner surface features and the turbulator to synergistically improve a heat transfer coefficient relative to a heat exchange tube without both the inner surface features and the turbulator, and in an operation condition where the working fluid flow is in an intermediate regime,
the intermediate regime is defined as including Reynolds numbers including lower than a transition point before a turbulent flow regime, including the transition point, and including a relatively smaller portion of the turbulent flow regime,
wherein a ratio of turbulator pitch P1 to a tube inner diameter Dt, P1/Dt, is from 1 to 2.5, and
a ratio of a turbulator diameter Dw to the tube inner diameter Dt, Dw/Dt, is from 0.04 to 0.1.

### Claim 10 (depends on 9)

The method of claim 9, wherein the operation condition includes temperature applications at or below 32° F., and the transition point is a Reynolds number of 8000.

### Claim 11 (depends on 9)

The method of claim 9, further comprising providing a ratio of turbulator pitch P1 to a pitch P2, the pitch P2 being a distance between two neighboring surface features in a longitudinal direction of the heat exchange tube, where the ratio P1/P2 is about 2 or 3.

### Claim 12 (depends on 9)

The method of claim 9, further comprising providing outer surface features on an outer surface of the heat exchange tube.

### Claim 13 (depends on 9)

The method of claim 9, wherein the turbulator is copper.

### Claim 14 (depends on 9)

The method of claim 9, further comprising fixing a first end of the turbulator on a first end of the heat exchange tube; and
extending a second end of the turbulator to a second end of the heat exchange tube.

### Claim 15 (depends on 9)

The method of claim 9, wherein the turbulator includes a diameter larger than an inner diameter of the heat exchange tube, such that extending the turbulator within the heat exchange tube and then releasing the heat exchange tube, a retraction tendency of the turbulator pushes the turbulator against the inner surface of the heat exchange tube to retain the turbulator within the heat exchange tube.