US3817319A - Conduction of heat exchange fluids - Google Patents

Conduction of heat exchange fluids Download PDF

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Publication number
US3817319A
US3817319A US00306181A US30618172A US3817319A US 3817319 A US3817319 A US 3817319A US 00306181 A US00306181 A US 00306181A US 30618172 A US30618172 A US 30618172A US 3817319 A US3817319 A US 3817319A
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Prior art keywords
tube
corrugation
crest
fluid
flow
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Expired - Lifetime
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US00306181A
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English (en)
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K Kauder
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Kabelmetal Electro GmbH
KM Kabelmetal AG
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KM Kabelmetal AG
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Assigned to KABELMETAL ELECTRO GMBH, KABELKAMP 20, 3000 HANNOVER 1, GERMANY reassignment KABELMETAL ELECTRO GMBH, KABELKAMP 20, 3000 HANNOVER 1, GERMANY ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: KABEL- UND METALLWERKE GUTEHOFFNUNGSHUTTE AG
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15D—FLUID DYNAMICS, i.e. METHODS OR MEANS FOR INFLUENCING THE FLOW OF GASES OR LIQUIDS
    • F15D1/00—Influencing flow of fluids
    • F15D1/02—Influencing flow of fluids in pipes or conduits
    • F15D1/06—Influencing flow of fluids in pipes or conduits by influencing the boundary layer
    • F15D1/065—Whereby an element is dispersed in a pipe over the whole length or whereby several elements are regularly distributed in a pipe
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L11/00—Hoses, i.e. flexible pipes
    • F16L11/14—Hoses, i.e. flexible pipes made of rigid material, e.g. metal or hard plastics
    • F16L11/15—Hoses, i.e. flexible pipes made of rigid material, e.g. metal or hard plastics corrugated
    • 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
    • F28F1/08—Tubular elements crimped or corrugated in longitudinal section

Definitions

  • the present invention relates to the conduction of fluid through flexible tubes, particularly for purposes of heat exchange. More particularly, the invention relates to improvements involving particulars of helical corrugation for such tubes, with regard to flow characteristics in relation to the tubes wall.
  • tubes which can be described as having wall structure of a regularly repeated geometric contour and configuration pattern. Depending on various factors, including particulars of the pattern, such tubes can be stiff or flexible. However, the tube will be quite flexible where its corrugation crests and valleys loop around the axis and the wall of the tube is not too thick. Tubing with corrugation that loops around the axis along the periphery of the tube, is quite flexible and can be reeled on drums. In fact, the tubing can be installed just like a cable. Such tubes are used as conduit for fluids, either for transporting fluid as such or for using the fluid medium as carrier for thermal energy.
  • Short, metal hose, as well as tubes of medium length are used particularly in case of heat exchange between the fluid in the tube and the environment, e.g. over the length of the tubing or at the destination point.
  • Long corrugated tubing is used as conduit for fresh or waste water or as conduit for hot water or steam in a central heating system, or for many other purposes.
  • the demand for tubing of this type has steadily increased in recent years.
  • corrugated tubes have not always been found satisfactory as carrier for a fluid in a heat exchange device.
  • tubes are used for heat transfer from one fluid to another one, which tubes maintain physical separation of the fluids but permit heat transfer over short distances of flow.
  • a concentric tube system establishes a flow path for one fluid in an inner tube, while the other fluid passes through the ring space between inner and outer tube. Heat is transferred through the wall of the inner tube.
  • heat exchange process involves basically three steps. (1) heat is transferred from the warmer fluid to the surface of the wall separating the fluids, (2) heat is conducted through the wall, (3) heat is transferred from the other wall surface to the cooler fluid. If the wall is made, for example, of copper or any other material having a high coefficient of thermal conductance, the thermal conductance through the wall can be disregarded in the consideration of the overall heat transmission between the two fluids.
  • K is the particular coefficient of heat transmission
  • A is defined by A 1r L (do di)/(lognat do/di) 2 The fraction in the equation being the logarithmic median value for the tube s diameter.
  • Equation l teaches that the heat transmission coefficient is always smaller than the smallest heat transfer coefficient a of the system because the equation can be written so that such smallest coefficient (a,- or 04,) appears as being multiplied by a factor that is necessarily smaller than unity.
  • the heat transfer coefficients include the thermal properties of the materials involved.
  • the coefficients a are composite parameters which in each system: fluid-wall surface, combine all physical processes that transfer thermal energy from the fluid to the wall (or vice versa). Such processes include molecular conduction, convection, radiation and evaporation or condensation. Evaporation and condensation occur only in special cases. Molecular conduction and radiation are usually determined by the physical properties of the materials involved.
  • the variable parameter in the process is convection, whereby convection is to be understood generally as any flow in any of the fluids which contribute to heat transfer.
  • baffles In analogy to the known expedient of increasing the effective heat exchange surface, it is, for example, known to place baffles into a smooth wall tube.
  • the baffles differ as to cross section.
  • the baffles so placed in smooth wall tubes may even have rectangular contour, or are discs or rings, or have propeller-like or helical configuration.
  • Reynolds number one can increase heat transfer to about the eightfold value, but up to a ten-thousandfold increase in pressure loss is suffered under such conditions.
  • the advantage of a better heat transmission process is at least partially offset by high pressure losses requiring increased pumping output.
  • helically corrugated tubing wherein the ratio of corrugation crest-to-valley height (radial) and corrugation crest-to-crest (axial) distance is from 0.01 to 0.5, preferably from 0.1 to 0.2; the ratio of the crest-to-valley height to smallest inner diameter of the tube is to be about 0.01 to 1.0 and the angle of the corrugation helix is to be between 5 to 20.
  • the known devices for improving convection are essentially devices which induce and enhance tubulent flow; the more turbulent flow the higher is the heat transfer across the flow into the boundary surface.
  • the penalty is pressure loss because turbulence enhances both, transfer of momentum and transfer of thermal energy.
  • helical flow adjacent the boundary tends to impart rotation upon the cylindrical, straight axial center flow.
  • the flow has two components, axial and circumferential.
  • the intensity of the latter component depends upon the configuration of the helical channel as it induces, ultimately, the circumferential velocity component.
  • the intensity of the induction of that rotational flow will be higher for larger crest-to-valley height of the corrugation (channel depth).
  • the rotational flow will be lower, the larger is the axial spacing of corrugation crests.
  • rotational flow will be determined by the ratio of these geometric values as defining the corrugation as well as by the relative channel depth and the pitch of the helix.
  • FIG. 1 is a three-dimensional velocity profile diagram in a tube to be produced for heat exchange enhancement
  • FIGS. 2a and 2b are longitudinal and cross-sectional views through a corrugated tube
  • FIGS. 3 and 4 are diagrams for showing kinetic energy of rotational flow and axial flow plotted against corrugation defining tube parameters
  • FIG. 5 shows a tube to be used as fluid conduit
  • FIG. 6 is a schematic section diagram through a corrugation valley and adjoining crests to define contour of helical channel flow along a tubes wall.
  • FIG. 1 illustrates the velocity profile 15 to be attained.
  • the profile is plotted in three-dimensional diagram.
  • the horizontal plane shown in perspective view is taken in a cross section through a tube, using the same plane to plot azimuthal velocity C along a diameter 10, including circumferential velocity component C,,,,*.
  • the resulting profile curve is denoted with 11.
  • the axial velocity is plotted along a vertical axis of the drawing, using said diameter 10 as base for each velocity vector.
  • the end points of the vectors follow a profile 12 for the axial component of fluid velocity.
  • the character c denotes a vector on that diameter as foot point of the actual composite velocity resulting in a profile curve 15.
  • the fluid flow in a tube according to the profile 15 causes transportation of kinetic energy and momentum in accordance with density and velocity. That energy transport can be divided into an axial component and an azimuthal or rotational component.
  • the relative energy inherent in the axial component of flow and integrated over the cross section of the conduit, may be designated E and the rotational component, integrated analogously, may be called E Fluid increments carrying this kinetic energy of flow are also the carrier of the thermal energy.
  • E The relative energy inherent in the axial component of flow and integrated over the cross section of the conduit, may be designated E and the rotational component, integrated analogously, may be called E Fluid increments carrying this kinetic energy of flow are also the carrier of the thermal energy.
  • a high energy component for the rotational (kinetic) flow inherently enhances the heat transfer into the wall. Therefore, the fluid flows in axial direction pursuant to the regular axial extension of the conduit; a rotational velocity field is superimposed upon the axial component, circulating around the circumference and imparting its thermal energy to (or receiving thermal energy from) the wall
  • FIG. 2 shows a tube made, for example, from thin metal strip.
  • the strip has been folded longitudinally into a split tube, the joint being established by and along the previously opposite edges of the strip which now abut or overlap.
  • the joint is closed through longitudinal seam welding, and the resulting tube is provided with helical corrugation.
  • the corrugation in cross section appears as a wave-like pattern of alternating crests and grooves or valleys.
  • Corrugated tubing is, of course, known per se, but the corrugation is provided under observation of specific rules so that the rotational component of flow is obtained by forcing the fluid to follow particular channels as defined by the corrugation grooves or valleys as seen from the interior of the tube.
  • the (axial) crest-to-crest distance T and the (internal, radial) crest-to-valley height I define the corrugation pattern.
  • the smallest inner diameter d which is the diameter of a cylinder 20 that is tangent to all inwardly directed crests.
  • T/n'd defines the tangent function of the helix angle 5 of the corrugation.
  • the largest outer diameter D of the tube is tangent to the outer apeces of the radially outwardly directed crests. If the tubes wall has thickness S, one can also define a cylinder that is tangent to the apex of the inner valleys, that cylinder has diameter D-2S.
  • the parameters are selected as follows. For t/T to range from 0.01 to 0.5 (preferably 0.1 to 0.2); t/d to be within the range from 0.01 to 1.0 (preferably 0.03 to 0.3); and helix angle 8 5 to 20. It can readily be seen that these corrugation parameters define the intensity of compelling a peripheral portion of the fluid to flow in a helical channel, and viscosity causes the fluid outside of the helical channel, closer to the interior of the tube, to still have a rotational component. The parameters determine also the number of loops in the flow path per axial unit length.
  • FIG. 3 illustrates the relationship between corrugation helix angle 8 and the ratio of the two kinetic energies E and E as defined above.
  • the angle 8 has to be varied through variation of T, and curve 30 has been calculated.
  • FIG. 4 illustrates the energy ratio E /E, plotted against t/d for T/d 0.3 which is between 5 and 6.
  • E /E energy ratio
  • FIG. 5 The preferred form of constructing a heat exchange tube is actually shown in FIG. 5.
  • FIG. 2 has served primarily for defining the relevant parameters.
  • the grooves or valleys in FIG. 5 are rather shallow, followed in each instance by a pronounced crest.
  • the selection of tube corrugation is preferably tightened additionally as follows.
  • FIG. 6 shows particularly a variety of curves, each outlining the corrugation for the same set of parameters T, t and d, including even an asymmetric pattern as shown-in dotted lines. Not all of these contours give equally favorable results. It can readily be seen that, for example, trace a outlines a corrugation which, in fact, establishes a deep, narrow channel separated by crests with rather shallow apex as extending into the flow, so that a predominant portion of the inner surface is defined by almost cylindrical sections, separated by the narrow spiral channel. On the other hand, trace b outlines a contour of a rather wide channel separated axially by steep ridges (such as shown in FIG. 5).
  • wavelength T/2 and corrugation depths t define a rectangle. Part of this rectangle is occupied by two subareas, each being half of a cross section area of an inwardly directed corrugation crest (e.g., as hatched), the remainder being the channel cross section area. That area is to be about two-thirds less of the rectangle T/2-t.
  • half of the cross section of the helical channel as defined by the corrugation is at most twice as large as half of the cross section of the helical ridge that separates the loops of the spiral channel. Under these conditions, optimum heat transfer coeffi cients are obtained as between fluid and the tubes wall. This is approximately curve c in FIG. 6.
  • Tubes meeting these requirements are well suited as fluid conductors in long paths for heat exchange such as required, for example, in desalination plants. It may be desirable here to provide stretches of the tube with smooth wall to facilitate installation in heat exchange planes.
  • helical corrugation having the stated parameters do, in fact, provide for rotational flow at optimum heat transfer characteristics as been fluid and wall.
  • Tubes having annular corrugation at similar parameters provide baffles in the flow resulting in backwater zones adjacent the annular corrugation ridges with no rotational flow and provide for considerably inferior heat transfer.
  • Method for conducting fluids through a tube for heat transfer as between tube and fluid comprising the step of:
  • the corrugation having axially alternating crests and valleys
  • t/T is from 0.01 to 0.5, t/d from 0.01 to 1.0; and 8 from 5 to 20.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Geometry (AREA)
  • Thermal Sciences (AREA)
  • Fluid Mechanics (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
  • Rigid Pipes And Flexible Pipes (AREA)
US00306181A 1971-11-15 1972-11-14 Conduction of heat exchange fluids Expired - Lifetime US3817319A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2156578A DE2156578B2 (de) 1971-11-15 1971-11-15 Flexible Wärmetauscher-Rohrleitung

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US3817319A true US3817319A (en) 1974-06-18

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US00306181A Expired - Lifetime US3817319A (en) 1971-11-15 1972-11-14 Conduction of heat exchange fluids

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US (1) US3817319A (enrdf_load_stackoverflow)
JP (1) JPS5517920B2 (enrdf_load_stackoverflow)
DE (1) DE2156578B2 (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0795710A1 (de) * 1996-03-15 1997-09-17 Witzenmann GmbH Metallschlauch-Fabrik Pforzheim Druckdichte und mit Wellungen versehene Rohrleitung
WO2003036212A1 (en) * 2001-10-26 2003-05-01 Valeo Termico, S.A. Heat exchanger, especially for the cooling of gases in an exhaust gas recycling system
US20070017588A1 (en) * 2003-07-22 2007-01-25 Aloys Wobben Flow channel for liquids
US20110056653A1 (en) * 2009-09-08 2011-03-10 Krones Ag Shell-and-Tube Heat Exchanger

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AR205405A1 (es) * 1974-12-20 1976-04-30 Ecodyne Corp Un tubo intercambiador de calor realizado de un material plastico
US4648093A (en) * 1984-09-06 1987-03-03 Coherent, Inc. Power supply for gas discharge lasers

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3612175A (en) * 1969-07-01 1971-10-12 Olin Corp Corrugated metal tubing

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4844055U (enrdf_load_stackoverflow) * 1971-09-23 1973-06-08

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3612175A (en) * 1969-07-01 1971-10-12 Olin Corp Corrugated metal tubing

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0795710A1 (de) * 1996-03-15 1997-09-17 Witzenmann GmbH Metallschlauch-Fabrik Pforzheim Druckdichte und mit Wellungen versehene Rohrleitung
WO2003036212A1 (en) * 2001-10-26 2003-05-01 Valeo Termico, S.A. Heat exchanger, especially for the cooling of gases in an exhaust gas recycling system
ES2199036A1 (es) * 2001-10-26 2004-02-01 Valeo Termico Sa Intercambiador de calor, especialmente para el enfriamiento de gases en un sistema de recirculacion de gases de escape.
ES2199036B1 (es) * 2001-10-26 2004-11-16 Valeo Termico, S.A. Intercambiador de calor, especialmente para el enfriamiento de gases en un sistema de recirculacion de gases de escape.
US20070017588A1 (en) * 2003-07-22 2007-01-25 Aloys Wobben Flow channel for liquids
US7487799B2 (en) 2003-07-22 2009-02-10 Aloys Wobben Flow channel for liquids
US20110056653A1 (en) * 2009-09-08 2011-03-10 Krones Ag Shell-and-Tube Heat Exchanger
EP2299226A3 (de) * 2009-09-08 2016-12-07 Krones AG Röhrenwärmetauscher mit Faltenbalg-Kompensator

Also Published As

Publication number Publication date
JPS5517920B2 (enrdf_load_stackoverflow) 1980-05-15
DE2156578B2 (de) 1980-12-11
DE2156578A1 (de) 1973-05-24
JPS4862006A (enrdf_load_stackoverflow) 1973-08-30

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Owner name: KABELMETAL ELECTRO GMBH, KABELKAMP 20, 3000 HANNOV

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:KABEL- UND METALLWERKE GUTEHOFFNUNGSHUTTE AG;REEL/FRAME:004284/0182