Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F1/00—Tubular elements; Assemblies of tubular elements
  • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
  • F28F1/12—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F1/00—Tubular elements; Assemblies of tubular elements
  • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
  • F28F1/12—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element
  • F28F1/24—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element and extending transversely
  • F28F1/32—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element and extending transversely the means having portions engaging further tubular elements
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F1/00—Tubular elements; Assemblies of tubular elements
  • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
  • F28F1/40—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only inside the tubular element
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
  • F28F21/08—Constructions of heat-exchange apparatus characterised by the selection of particular materials of metal

Definitions

• the subject matter disclosed herein relates to heat exchangers. More specifically, the subject disclosure relates to improved tube structures for a heat exchanger.
• a simplified typical vapor compression refrigeration cycle includes an evaporator, a compressor, a condenser and an expansion device.
• Refrigerant flow is such that low pressure refrigerant vapor passes through a suction line to the compressor.
• the compressed refrigerant vapor is pumped to a discharge line that connects to the condenser.
• a liquid line receives liquid refrigerant exiting the condenser and directs it to the expansion device.
• a two-phase refrigerant is returned to the evaporator, thereby completing the cycle.
• RTPF round tube plate fin
• the tubes were made of copper while the fins were typically made of aluminum in such heat exchangers.
• the thermal performance of a heat exchanger is inversely proportional to the sum of its thermal resistances.
• HVAC&R heating, ventilation, air conditioning and refrigeration
• the airside thermal resistance contributes 50-70% while refrigerant side thermal resistance is 20-40% and the metal resistance is relatively small and represents only 6-10%. Due to the continuous market pressure and regulatory requirements to make HVAC&R units more compact and cost effective, a lot of effort has been devoted to improving the heat exchanger performance on the refrigerant side as well as the airside.
• a fluid-carrying tube for a heat exchanger includes an outer perimeter, an inner perimeter, and a plurality of ridges extending from the inner perimeter inwardly into an interior of the tube.
• Each ridge includes a ridge height, a base width and a tip width.
• a ratio of the ridge height to the base width is between about 0.2 and about 4.0, and a ratio of the tip width to the base width is between about 0.015 and about 0.965.
• a heat exchanger includes a plurality of fins and a plurality of tubes passing a fluid therethrough and extending through the plurality of fins.
• At least one tube of the plurality of tubes includes an outer perimeter, an inner perimeter, and a plurality of ridges extending from the inner perimeter inwardly into an interior of the at least one tube.
• Each ridge has a ridge height, a base width, and a tip width.
• a ratio of the ridge height to the base width is between about 0.2 and about 4.0, and a ratio of the tip width to the base width is between about 0.015 and about 0.965.
• Figure 1 is a schematic view of an embodiment of a heat exchanger
• Figure 2 is a partial cross-sectional view of an embodiment of a heat exchanger tube
• Figure 3 is a cross-sectional view of an embodiment of a heat exchanger tube.
• FIG. 1 Shown in Figure 1 is an embodiment of a round tube plate fin (RTPF) heat exchanger 10, such as one utilized as an evaporator or condenser.
• the RTPF heat exchanger 10 includes a plurality of tubes 12 and a plurality of fins 14.
• the plurality of tubes 12 carry a fluid, for example, a refrigerant. Thermal energy is exchanged between the fluid and air flowing past the plurality of fins 14.
• the tubes 12 may be formed of an aluminum or aluminum alloy by, for example, an extrusion process, while in other embodiments, the tubes 12 maybe formed of other materials, for example, copper, Cu-Ni, steel or plastic.
• FIG. 2 illustrates a partial cross-sectional view of a tube 12 of a heat exchanger 10.
• the tube 12 includes a plurality of enhancements, or ridges 16 extending into an interior 18 of the tube 12.
• the tube 12 has an outer perimeter 32 and an inner perimeter 34, with the ridges 16 extending inwardly from the inner perimeter 34 into the interior 18 of the tube 12.
• the ridges 16 extend along a length 20 of the tube 12.
• the ridges 16 extend substantially axially, while in other embodiments, the ridges 16 extend helically along the tube 12 at a helix angle a with respect to a tube axis 24.
• Ridges 16 such as those described herein, improve the heat transfer characteristics of the tubes 12 while maintaining a balance with pressure drop requirements to achieve a desired refrigerant flow through the tubes 12.
• Specific geometric configurations of the ridges 16, enhancing both the pre-expansion and post-expansion tube 12 surface geometry, are described below by way of example.
• the ridges 16 have a number of characteristics to define their shape and arrangement in the interior 18 of the tube 12.
• Each ridge 16 has a ridge 16 height h, a base 26 width w, and a tip 28 width b. Sides 30 of the ridge 16 extend from the base 26 to the tip 28 at an apex angle Y. Adjacent ridges 16 are spaced by a ridge 16 pitch P r .
• Each tube 12 has a tube diameter D, and a baseline tube 12 wall thickness between adjacent ridges 16.
• the increased internal surface area of the tube 12 including ridges 16 compared to the smooth-walled tube increases the effectiveness of thermal energy transfer between fluid in the tube 12 and an external environment.
• the effect of the increased surface area can be expressed as an enhancement ratio R x as in equation (2) below:
• R x (2 *h*N r *((l-sin(Y/2)/ ⁇ *(D-2*(tb+h))*cos(Y/2)))+l)/cos a
• the enhancement ratio Rx is a strong linear function of 1 ⁇ /( ⁇ *( D-2*(t b +h))/N r ), which is a ratio of the ridge height h, to the ridge pitch P r .
• the ridges 16 may extend substantially axially along the length 20, or may extend at helix angle a of between about 18 degrees and about 35 degrees. Further, a ratio of the number of ridges Nr to a maximum internal diameter of the tube 12, or N/D imax may be between about 5.4 and about 10.1, where D imax is specified in millimeters. In some embodiments, a ratio of the ridge height, h, to the ridge pitch, P r , is between about 0.17 and about 1.36. R X; as shown in equation 1, is between about 1.28 and about 3.49 in some embodiments, for example, those where the ridges 16 extend substantially axially along the tube 12.
• R x is between about 1.34 and about 4.26.
• a ratio ridge height h to maximum internal diameter of the tube 12, or h/D imax is between about 0.0008 and about 0.0870.
• the apex angle Y is between about 10 degrees and 25 degrees.
• the ridge height h and base width w are related such that a ratio of the ridge height to the base width, or h/w is between about 0.2 and about 4.0.
• the tip width b and the base width w, or b/w is between about 0.015 and about 0.965.
• N r /Di max may be between about 5.4 and about 9.25.
• h/ P r is between about 0.17 and about 1.22.
• R x is between about 1.28 and about 3.23 in embodiments where the ridges 16 extend substantially axially along the tube 12 and where the helix angle a is not zero, R x is between about 1.34 and about 3.94.
• h/Di max is between about 0.0008 and about 0.035.
• N r /Di max where Dj max is expressed in millimeters, may be between about 5.8 and about 10.1.
• h/ P r is between about 0.19 and about 1.36.
• R x is between about 1.30 and about 3.49 in embodiments where the ridges 16 extend substantially axially along the tube 12 and where the helix angle a is not zero, R x is between about 1.37 and about 4.26.
• h/Dj max is between about 0.0117 and about 0.0488.
• N/D imax may be between about 5.4 and about 9.5, where D imax is specified in millimeters.
• h/P r is between about 0.18 and about 1.30.
• R x is between about 1.28 and about 3.37 in embodiments where the ridges 16 extend substantially axially along the tube 12 and where the helix angle a is not zero, R x is between about 1.35 and about 4.12.
• h/D imax is between about 0.021 and about 0.087.
• N r /Di max may be between about 5.5 and about 9.4, where Dj max is specified in millimeters.
• h/P r is between about 0.18 and about 1.30.
• R x is between about 1.29 and about 3.39 in embodiments where the ridges 16 extend substantially axially along the tube 12 and where the helix angle a is not zero, R x is between about 1.36 and about 4.14.
• h/Dj max is between about 0.021 and about 0.087.
• tubes 12 illustrated herein are substantially circular, it is to be appreciated that, in other embodiments, the tubes 12 may be noncircular in cross-section having, for example, an oval, an elliptical, or a race-track cross-section.
• an equivalent to tube 12 diameter D would be a circular cross-section tube diameter that would have identical mass or material content in the cross-section as the particular non-circular cross-section. All geometrical ratios described hereabove are equally applicable to such non- circular tube configurations allowing achieving substantially improved in-tube thermal and hydraulic performance.
• tubes 12 including such ridges 16 that conform to the exemplary ranges of these ratios exhibit substantially improved thermo-hydraulic performance over prior art tubes.
• the ratios, and described ranges for the ratios, are not obvious and have been developed via extensive simulation and experimentation on the component and sub-component level, while specifically focusing on the two-phase refrigerant flows.

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• 2012
  • 2012-01-26 CN CN201280006657.8A patent/CN103339460B/zh active Active
  • 2012-01-26 WO PCT/US2012/022641 patent/WO2012103278A1/en active Application Filing
  • 2012-01-26 EP EP12702387.7A patent/EP2668460A1/de not_active Withdrawn
  • 2012-01-26 US US13/981,364 patent/US20130306288A1/en not_active Abandoned

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