Liquid Metal Heat Exchanger

Abstract

A liquid metal heat exchanger providing for a single pass of primary liquid metal and two passes of secondary liquid metal consisting of a removable core suspended at the top by an annular tube sheet clamped by a bolted ring for convenient removal. A funnel leading into a central downcomer separates cold incoming secondary liquid metal from the relatively hot outgoing secondary liquid metal.

Description

BACKGROUND OF THE INVENTION

The invention described herein was made in the course of, or under, a contract with the United States Atomic Energy Commission.

In the development of liquid metal fast breeder reactors, it is necessary to produce effective and reliable heat exchange apparatus for the transfer of heat from the primary liquid metal reactor coolant to suitable secondary liquid metal. A typical liquid metal suitable for this application is molten sodium.

Among the difficulties involved in the design and development of suitable heat exchange apparatus are those having to do with conducting maintenance operations in a liquid sodium environment, absorbing stresses induced by thermal gradients, and others which will become apparent from the description of this invention.

SUMMARY OF THE INVENTION

The present invention overcomes drawbacks in the prior art, such as the difficulties mentioned above by providing heat exchange apparatus in which the tubes are readily accessible for maintenance and repair, and incorporating a thermal barrier to reduce thermal stresses as a result of temperature differences between the cold incoming secondary liquid metal and the remaining sodium in the apparatus.

It is thus one of the objects of this invention to provide an improved heat exchanger with improved maintenance and repair features and reduced thermal stresses.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an elevation view in section of a heat exchanger made in accordance with this invention;

FIG. 2 is a view along 2--2 of FIG. 1;

FIG. 3 is a sectional view showing in detail a portion of the heat exchanger of FIG. 1; and

FIG. 4 is a sectional view showing in detail another portion of the heat exchanger of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the figures, heat exchanger 10 consists of an outer cylindrical shell 12 forming a lower section of the heat exchanger 10 and having a curved bottom 14 having a primary outlet 16. Adjacent to the upper end of the shell 12 is a primary inlet 18 above which is a cylindrical upper section 22 which is provided on one side with a secondary outlet 24 in the lower portion thereof. The upper section 22 is of larger diameter than the shell 12. A secondary inlet 26 is located in section 22 at a location above that of secondary outlet 24. The top of upper section 22 is closed off with an inverted hemispherical head 28 having a flange 32 which is bolted to a flange 34 of upper section 22. Inverted head 28 reduces the liquid metal content on the secondary side.

It will be seen that at the top of the lower section 12 is a flange 34 which forms the lower end of the upper section 22. The flange 34 forms the support for a removable core 35 which is positioned within the section 22. Clamping ring 36 holds in place an annular tube sheet 38 while bolts 42 spaced along ring 36 threaded into flange 34 hold the former in place.

Extending down into lower section 12 is a downcomer tube 44 which at the lower end thereof supports a lower annular tube sheet 46 from which extends an elliptical head 48 forming a collection compartment 52. Spacer brackets 54 are provided for centering purposes.

The upper end 55 of downcomer tube 44 attaches to the lower face of the upper tube sheet 38 which in turn rests on flange 34. A welded omega seal 56 is provided between the upper tube sheet 38 and the flange 36.

A funnel-like member 58 having a lower cylindrical portion which extends down into downcomer tube 44 and an upper portion which flares upwardly and outwardly is bolted at its peripheral marginal portion to a support ring 59 which is mounted on the inside wall of the upper section 22. The lower portion of the funnel-like member 58 extends down into downcomer tube 44 to serve as a thermal barrier to reduce the thermal stresses in tube sheet 38 and also to reduce leakage of incoming cold secondary sodium into outgoing hot secondary sodium chambers. A thin sleeve 60 (FIG. 3) made of stainless steel in its upper portion and of a material having a lower coefficient of expansion than stainless steel in its lower portion is positioned snugly between the upper tube sheet 38 and the lower portion of member 58 to reduce further the leakage of secondary sodium.

A second flared member 61 located below the funnel member 58 is connected with that section through a cylindrical member 62 which extends from the outer edge of the section 61 upwardly to the funnel member 58 as shown best perhaps in FIG. 4.

The upper funnel member 58 is thick enough to withstand the pressure of the secondary fluid and the lower flared member 61 is made thin enough to serve as a thermal barrier for the upper funnel 58. Metallic thermal insulation 63 reduces the thermal gradient in the portion of the upper section 22 located between the secondary fluid outlet nozzle 24 and the support ring 59.

Connecting upper and lower tube sheets 38 and 46, respectively, is an annular assembly of tubes referred to as tube bundle 66, welded at both ends to their respective tube sheets. Flow baffles 68 also serve a tube supports. The baffle arrangement is not a part of this invention, being part of an invention covered by U.S. application Ser. No. 8501, entitled "Liquid Metal Heat Exchanger," filed Feb. 4, 1970 in the name of Walter Wolowodiuk, one of the inventors herein. A plurality of inner and outer spaced tie rods 72 and 74 respectively, having sleeves interconnect the flow baffles by welding and bolting as shown in FIG. 2 to obtain a more rigid structure.

In the operation of heat exchanger 10, hot primary sodium enters through inlet 18, circulates around the tubes in bundle 66, filling the annular space around downcomer 44 and leaves through outlet 16 at the bottom of shell 12. Single marked arrows show primary flow while double headed arrows show secondary flow. Relatively cold secondary sodium enters through upper nozzle 26, flows downward through funnel-like member 58, downcomer tube 44, and into lower compartment 52. The sodium then passes up through tube sheet 46 into the tubes of bundle 66, through tube sheet 38 and out through nozzle 24.

In the arrangement described, the construction permits tube plugging without removing the tube bundle 66. This is accomplished by removing inverted hemispherical head 28 and the upper funnel-like member 58 with its associated lower member 64 which exposes upper tube sheet 38 for maintenance work. For the removal of bundle 66, ring 36 is unbolted and lifted out, omega seal 56 is cut and bundle 66 is lifted out of shell 12.

Claims

What is claimed is:

1. A liquid metal heat exchanger comprising:

a cylindrical shell having an upper section and a lower section;

a funnel-shaped member in said upper section, said member being removably attached at the periphery thereof to said upper section;

an axially disposed removable core means extending down into the lower section of said shell; said core means comprising a cylindrical tube extending down into said lower section and positioned so that the narrow part of said funnel communicates with said tube; a lower annular tube sheet mounted on the bottom of and surrounding said tube; a closure enclosing the bottom of said tube and lower tube sheet forming a lower compartment; an upper annular tube sheet encircling said tube and removably attached at its periphery to said shell; and a bundle of tubes extending between said upper and lower tube sheets to complete a flow path of secondary coolant flowing down through said funnel-shaped member, tube, lower compartment, and up through said bundle of tubes;

means in said upper section for suspending and clamping the top of said removable core means at the periphery of said upper tube sheet;

a secondary sodium inlet and a secondary sodium outlet in said upper section, said inlet and outlet both being in the side wall of said upper section of said shell at a location laterally beyond the peripheries of said upper and lower annular tube sheets, said inlet being laterally beyond the periphery of said funnel-shaped member, said inlet directing fluid over said funnel-shaped member to flow downward through said tube, said outlet being disposed below said funnel-shaped member but above said upper tube sheet to direct secondary fluid coming out of said tube bundle out of said exchanger; and

a primary sodium inlet in the upper portion of said lower section said primary sodium inlet being laterally beyond said bundle of tubes and said lower tube sheet, and a primary sodium outlet below said lower chamber.

2. The liquid metal heat exchanger defined in claim 1 wherein said means for suspending and clamping the top of said removable core means comprises an annular flange, said upper tube sheet being removably connected with said flange.

3. The liquid metal heat exchanger defined in claim 2 wherein said means for suspending and securing the top of said removable core means further comprises a clamping ring bolted to said flange, said clamping ring clamping said upper tube sheet between said ring and said flange.

4. The liquid metal heat exchanger defined in claim 3 wherein said upper tube sheet is supported upon the top of said cylindrical tube.

5. The liquid metal heat exchanger defined in claim 4 further comprising a head, said head closing the top of said upper section and being bolted about its periphery to the top of said upper section.

6. A heat exchanger for placing two fluids in indirect heat exchange comprising: a shell; an intake in the side wall of said shell for a first of said fluids; an exhaust for said fluid positioned below said intake; a tube; a first annular tube sheet and a second annular tube sheet, said tube sheets encircling and being axially positioned with respect to said tube, said first tube sheet being closer to said intake than said second tube sheet; a tube bundle extending between said tube sheets; a chamber contiguous to said second tube sheet whereby said first fluid comes in through said intake, flows over said tube bundle outside of said chamber and exits at said exhaust, an inlet for a second of said fluids, said inlet being positioned laterally of said tube sheets, a funnel-like member for directing said second fluid from said inlet to said tube; an outlet for the second of said fluids, said outlet being between said first tube sheet and said funnel-like member, whereby said second fluid comes in through said inlet, passes through said funnel and said tube to said chamber, then passes through said tube bundle and out said outlet, said funnel-like member and said first tube sheet being removably secured at their peripheries to said shell to permit access to said tube bundle by moving said funnel and then said first tube sheet and attached tube bundle axially out of said shell.

7. The heat exchanger defined in claim 6 further comprising a support ring, the peripheral marginal portion of said funnel-like member being bolted to said ring.

8. The heat exchanger defined in claim 6 further comprising a clamping ring, said clamping ring being positioned over the outer peripheral marginal portion of said first tube sheet and bolted to said heat exchanger.

9. The heat exchanger defined in claim 8 wherein said tube and said tube bundle are substantially vertically disposed with said first tube sheet at a higher elevation than said second tube sheet, said funnel-shaped member having a lower cylindrical portion extending down into said tube, said first tube sheet having an inner marginal portion resting on the top of said tube.