US2943845A - Heat exchanger for viscous fluids - Google Patents

Description

July 5, 1960 F. JAKLITSCH HEAT EXCHANGER Foa vrscous muros Filed oct. 23, 1957 IN V EN TOR.

@HA/Z Jn/Ef# BY WMLM,-fwm v im @im ,United States Patent ce This invention may be manufactured and used by or for the Government of the United States for -governmental purposes without the payment to me of any royalties thereon.

This invention relates to heat transfer devices and in particular to a device for controlling the temperature of viscous fluid systems such as oil systems, by heat exchange between the oil with a hotter or cooler fluid. v

The oil cooling systems, including oil coolers and fans, have always been a critical part of power packages especially in combat or military vehicles where unusual restrictions to cooling air flow are imposed due to the requirement for ballistic protection.

One of the primary reasons for failures in power packages of vehicles is the high heat transfer requirements ofthe power plant system necessitating the use of large oil coolers. based on a multitude of narrow'cross sections of flow and relatively thin thicknesses of walls assembled with brazed connections so that they are not adaptable to high pressures and which are therefore subject to leakage and vibration failures. While the hydraulic pipe system can withstand pressures of 1000 pounds per square inch, present oil coolers can withstand approximately 250 pounds per square inch and then only for short intervals of time.

The high demand of air coolant necessitates llarge fans of high horsepower vinput thereby providing favorable conditions for material and bearing failures yin the fans also.

Accordingly, it is an object of this invention to provide a heat transfer device which is capable of elcient heat exchange between a viscous fluid, such as oil, and

air.

It is also an object of this invention to provide a heat transfer device which prevents formation of a thick adherent layer of the viscous material on the walls of the zdevice as it is cooled.

It is a further object of this invention to provide a heat transfer device in which the coolant quantity is kept to a It is a further object of this invention to provide a heat transfer device having elements capable of withstanding pressures of the same level at the hydraulic pipe system to which the heat transfer device is connected.

It is another object of this invention to provide a heat transfer device in which it is possible to preheat efficiently the viscous uid so that circulation will occur in the low temperature range.

These and other advantages will be apparent from the following description and drawings:

Fig. l is a sectional elevational view of a heat transfer device.

Fig. 2 is a sectional view taken along line II-II of Fig. 1.

Fig. 3 is a sectional elevational view of a modification of the -heat transfer device.

Referring to the drawings, a heat transfer device 4 utilizing air as a coolant comprises a hollow housing 6 The oil cooler systems in use are largely 2 Y having a plurality of longitudinal 8 on the internal surface. Within the housing 6 is a series of cores of' tubes 10 having a plurality of longitudinal fins 12 which intermate with longitudinal fins 8 of housing 6. YThe thickness of these cores from the inner diameter 11 to the roots 13 is sufficient to withstand the pressure eni countered in the hydraulic system of which inlet 24 and outlet 26 is a part. This thickness will vary'in acCbIflance with the pressures to be encountered and the materialU used for the core. 'Fig. 2 shows only two cores within the housing but any number may be used depend.- ent on the requirements of the individual system. The space 14 between the pairs of intermating fins forms a passageway for the cooling air which enters through coll- `duit 16 of inlet manifold 18 and then flows axially through the longitudinal passage formed by space 14. This space has a greater clearance at the roots -13 of the fins 12 than at the tips or peaks 15 resulting in a concentration 0f the maximum flow of coolant past the surfaces of highest temperatures, namely lthe root ofthe respective fins, thereby providing a most effective heat transfer. This also results in keeping the amount of coolant at a minimum, since it is applied at the highest temperature zone thereby eliminating every cross section of flow of low efficiency. The coolant then discharges through outlet v20 of exit manifold 22.

The fluid to be cooled enters the core 10 by intake pipe 24 and exits through outlet pipe 26, each of the pipes being attached to housing 6 in any conventional means. Within core l0 is a free rotating helicoidal screw 32 on central shaft or bar 34 rotatably supported against axial movement by thrust bearing 33 and spider network 35 or any other thrust bearing device which forces the oil to flow along the walls ofthe core in spiral paths thereby increasing the time of contact of the oil with the core l0 `with a tendency toward turbulent flow.

Rotation of screw 32 is generally accomplished by the flow of the oil or other viscous fluid. As the oil is cooled by the'flow of coolant through the counterlins, layers of the oil tend to adhere to the walls of core 10. The rotation of the screw 32 meets with more resistance with decreasing temperature of the oil and by the rotation of screw 32 the layers are then sheared from the core allowing the higher temperature fluid lto come into immediate contact with the walls of the core lll. The behavior of the screw 32 is self-controlling in that the flow of fluid is forced along the spiral in a `greater' number of helices at lower temperatures of the fluid and vice versa for higher temperatures of the fluid.

If desired, the helical screw 32 can be actuated by a gear or hydraulic device. In such a case, rotation of screw 32 is independent of the flow of the fluid and is easily controlled in accordance with the cooling requirements.

The device 4 can also be utilized for facilitating start ing the engine under the low temperature conditions by merely shifting from a coolant to a heating medium (a heated coolant) in order to preheat and thereby liquefy the oil and provid'eran unrestricted circulation. Once the engine is operating cooling air can again be provided. Y

In the modification shown in Fig. 3, the shaft 34 is replaced by a central tube 4i). A similar helicoidal screw 3l is rotatably supported against axialrnovement by thrust bearing 37 and spider network 39 on tube 40 or any other supporting device. At the exit end of tube 40 is a valve 4l normally urged to a closed position by spring 42. This valve is utilized to controlvthe pressure within core 1l?. When the pressure of flow from the intake 24 reaches a given point the valve 41 opens and flow takes place through the central tube 46 rather than through the spiral path within core 10. Under the in- A 2,943,845A Patented July 5,

fflfo spring `42tfhe` Y pressure allowing the` o'ilY tomagain owinrthe mnner valve 41V closesY on t decreasing previouslyl described. Y

" i; If desiredthe-valve 41Vcou1d be operatedby a remote Qontrol '^systei'n`} H(not shown) Ai111 Such Va -a'sevv automatic Yfonti-holslcould-be-used Whichl could be activated bythe ktemperatn'e of the enteringV fluid or the temperature of the discharging uid as Well as the regulation'by the pres.- Y

A 'heat transfer device ofthe' character described comprising a corehavingY anrinne'r uid flow passage and ppluralityjof peripheral ns thereon each extending parallelto therlongitudinal aXis thereof, a housing 'sur- Y Y rounding said core'and having a plurality of longitudinal llstherein vintermating with said core fins and defining `ha ;second 'uidr owpassage positioned in directY heat transferable relation to said core uid ow passage, a t :,shaftarrying a bladed helicoidal screw rotatably mounte'd in VYsaid core inner passage 'and adapted 4to be rotated .uponvow of uid in said core inner passage, said screw jin said core inner passage defining a spiral uid ow passage Vtherein, the blade of said screw during rotation thereof being adapted to prevent adherence of uid in said Y Ycore inner pass-age,V said shaft having inner passage f therethrough'deiining '"a"divertingy fluid ow'passagega'nd .Y uid ow control means regulating fluid ow in saidV divert ing uid ow passage.

2. A heat transfer device as set forth in Yclaim 1 Where- Y, in said fluid ovv control means comprises ak check valve positioned n said diverting fluid iow passage:Y and adapted t0 onenvillenflowY resistance nsaid Spiralpath reahes a predetermined value and to closewhen said ow resistancedecreases,N belowY said predetermined value. Y

References Cited in the le'of thislpatent UNIKTEDYSTATES PATENTS France Mar. 14, 1957

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