Heat exchanger conversion bundle with semi-circumferential seal

Abstract

An E-to-F conversion assembly is configured to be positioned inside an E-type heat exchanger shell to facilitate two passes of heat exchange fluid through the E-type heat exchanger shell. The conversion assembly includes: a stationary tube sheet; multiple tubes coupled to the tube sheet; baffles or supports through which one or more tubes of the multiple tubes extend; a hollow cylindrical shroud coupled to the tube sheet, wherein the shroud encompasses the tubes and baffles or supports; and a semi-circumferential seal coupled to an external surface of the shroud and extending halfway around the shroud in a circumferential direction.

Description

HEAT EXCHANGER CONVERSION BUNDLE WITHSEMI-CIRCUMFERENTIAL SEALBACKGROUND

[0001] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

[0002] Shell and tube heat exchangers are commonly used in industrial applications. Shell and tube heat exchangers include an outer shell and tubes located inside the outer shell. Heat exchange occurs between a first fluid communicated through the shell and a second fluid communicated through the tubes. Baffles are often located in the shell and attached to the tubes to augment the heat transfer between the two fluids.

[0003] Heat exchanger performance (i.e., heat transfer) is directly related to the temperature difference of the fluids moving through the heat exchanger. Other factors that contribute to heat exchanger performance include heat transfer coefficient and effective heat transfer area. However, as the temperature difference through the heat exchanger approaches zero, improving the heat transfer coefficient (e.g., through anti-fouling coatings or baffling / tube design) or increasing the effective area have little or no impact on heat exchanger performance. As such, it is desirable to regain some temperature difference through the heat exchanger to improve performance. This can be accomplished by replacing an E-type shell and tube heat exchanger with an F-type shell and tube heat exchanger. However, the shell nozzle layout is different between these two types of heat exchangers. The E-type shell and tube heat exchanger has an inlet nozzle at one end of the shell and an outlet nozzle at the opposite end of the shell, while the F-type shell and tube heat exchanger has both inlet and outlet nozzles located at the same end of the shell. Since the shell nozzle layouts differ, replacing an E-type shell and tube heat exchanger with an F-type shell and tube heat exchanger significantly impacts the piping at a plant and involves extra cost for the design and purchase of a new heat exchanger.

[0004] It may be desirable to increase the temperature difference through a shell and tube heat exchanger without changing the relative locations of the shell nozzles and / or replacing the entire heat exchanger.BRIEF DESCRIPTION OF DRAWINGS

[0005] The drawings illustrate only example embodiments and are therefore not to be considered limiting in scope, as the example embodiments may admit to other equally effective embodiments. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Additionally, certain dimensions or positions may be exaggerated to help visually convey such principles. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements.

[0006] FIG. l is a schematic diagram illustrating the replacement of an E-type bundle with an E-to-F conversion assembly inside an E-type shell of a heat exchanger, in accordance with an embodiment of this disclosure.

[0007] FIG. 2 is a perspective view of an example E-to-F conversion assembly not showing heat exchanger tubes, in accordance with an embodiment of this disclosure.

[0008] FIGS. 3A and 3B are perspective cutaway views of a heat exchanger shell with the E- to-F conversion assembly of FIG. 2 (including heat exchanger tubes) installed therein, in accordance with an embodiment of this disclosure.

[0009] FIGS. 4A and 4B are perspective views of the E-to-F conversion assembly of FIG. 2 showing in greater detail an example circumferential seal assembly, in accordance with an embodiment of this disclosure.

[0010] FIG. 5 is a perspective view of another example E-to-F conversion assembly, in accordance with an embodiment of this disclosure.

[0011] FIG. 6 is a perspective cutaway view of the E-to-F conversion assembly of FIG. 5 showing a sealing location between a shroud and a tube sheet, in accordance with an embodiment of this disclosure.

[0012] FIG. 7 is a perspective view of the E-to-F conversion assembly (including heat exchanger tubes) of FIG. 5, in accordance with an embodiment of this disclosure.

[0013] FIG. 8 is a perspective cutaway view of the E-to-F conversion assembly (including heat exchanger tubes) of FIG. 5, in accordance with an embodiment of this disclosure.

[0014] FIG. 9 is a perspective view of an example semi-circumferential seal assembly for use with an E-to-F conversion assembly, in accordance with an embodiment of this disclosure.

[0015] FIG. 10 is a perspective view of another example semi -circumferential seal assembly for use with an E-to-F conversion assembly, in accordance with an embodiment of this disclosure.

[0016] FIG. 11 is a cutaway view of the semi-circumferential seal assembly of FIG. 10, in accordance with an embodiment of this disclosure.

[0017] FIGS. 12A and 12B are cross-sectional block diagrams illustrating another example semi-circumferential seal assembly for use with an E-to-F conversion assembly, in accordance with an embodiment of this disclosure.

[0018] FIG. 13 is a schematic illustration showing an arrangement of springs in a semi- circumferential seal assembly for use with an E-to-F conversion assembly, in accordance with an embodiment of this disclosure.

[0019] FIG. 14 is a process flow diagram illustrating a method for changing an E-type heat exchanger into an F-type heat exchanger without changing the shell of the heat exchanger, in accordance with an embodiment of this disclosure.DETAILED DESCRIPTION OF THE INVENTION

[0020] There are different types of shell and tube heat exchangers having different configurations. An E-type shell and tube heat exchanger provides a single pass for the shell fluid through the shell (from one end to the other) while the internal tubes have two passes. In this configuration, shell fluid is not affected by both passes of the tube fluid through the tubes. As such, both fluids’ outlet temperatures are more likely to approach one another and have a zero or very low temperature difference. This is known as the heat exchanger being “temperature pinched.” As mentioned above, an E-type shell and tube heat exchanger has shell nozzles located at opposite ends of the shell to provide the single pass of shell fluid. E-type shell and tube heat exchangers are the most commonly used types of heat exchangers in many industrial applications.

[0021] An F-type shell and tube heat exchanger provides two passes for the shell fluid through the shell (from one end to the other, then back) while the internal tubes also have two passes. This allows the fluids to remain in counterflow throughout, thus maximizing the temperature difference of the heat exchanger. For example, when heating a cold fluid in an F-type shell and tube heat exchanger, the maximum outlet temperature of the fluid being heated is no longer limited by the hot fluid’s outlet temperature, but by the hot fluid’s inlet temperature, i.e., alarger temperature difference and more heat transfer. An F-type shell and tube heat exchanger has shell nozzles located at the same end of the shell to provide the two passes of shell fluid.

[0022] The cost and effort associated with replacing an E-type shell and tube heat exchanger with an F-type shell and tube heat exchanger is quite high, since this replacement would require replacing the large heat exchanger shell as well as the piping connected to and immediately surrounding the shell. Most plants are unable to support this type of shell and tube heat exchanger replacement to improve heat exchanger performance. It is now recognized that a need exists for systems and methods to increase the temperature difference through a shell and tube heat exchanger without changing the shell, changing the relative locations of the shell nozzles, and / or replacing the entire heat exchanger.

[0023] Embodiments of the present disclosure address this need by providing an E-to-F type shell and tube conversion assembly (an easily replaceable component) that converts an existing temperature-pinched E-type heat exchanger into behaving like an F-type heat exchanger to maximize temperature difference and duty. Increasing the temperature difference allows for the application of other technology to improve temperature coefficients and effective area, further increasing thermal performance of the heat exchanger.

[0024] The disclosed E-to-F conversion assembly replaces an existing bundle of tubes, baffles, and tube sheet of the E-type heat exchanger. The E-to-F conversion assembly is made by encasing a two-pass tube bundle inside a shroud (e.g., a removable cover) that will then be placed inside the original E-type shell. The E-to-F conversion assembly can provide F-type heat exchanger functionality within an E-type shell. That way, the E-type heat exchanger can essentially be converted to an F-type heat exchanger, without replacing the entire heat exchanger or changing the locations of the shell nozzles. The E-to-F conversion assembly may be easily and readily positioned into an existing E-type shell after removal of a pre-existing E- type heat exchanger bundle from the shell. Pulling the old bundle and replacing it with the E- to-F conversion assembly is straightforward and can be performed using a conventional bundle extractor. This replacement may provide an immediately improved temperature profile in the heat exchanger, allowing the operator to recoup energy savings, cost savings, production, and other benefits that would not be possible using the pre-existing E-type heat exchanger bundle.

[0025] While the figures depict the E-to-F conversion assembly including a tube assembly of multiple U-shaped tubes (“U-tubes”) to provide two passes for the tube heat exchanger fluid, the disclosed E-to-F conversion assembly is equally applicable with a tube assembly including straight tubes connected to a floating head type rear closure at the opposite end from the stationary tube sheet.

[0026] Turning now to the drawings, FIG. 1 is a schematic illustration showing a bundle replacement within a heat exchanger 100 in accordance with presently disclosed techniques. In a first configuration, the heat exchanger 100 has an E-type shell 102 and a conventional E- type bundle 104 located inside the shell 102. In a second configuration, after the replacement, the heat exchanger 100 still has the E-type shell 102 but with an E-to-F conversion assembly 106 located inside the shell 102. The replacement of the internal components of the heat exchanger 100 changes the heat exchanger 100 from operating as an E-type heat exchanger in the first configuration to operating as an F-type heat exchanger in the second configuration. The shell 102 does not change through the replacement; only the internal components inside the shell 102 are changed.

[0027] As illustrated, the shell 102 includes a fluid inlet nozzle 108 at a first longitudinal end 110 of the shell 102 and a fluid outlet nozzle 112 at a second longitudinal end 114 of the shell 102 opposite the first longitudinal end 110. The conventional E-type bundle 104 is configured to facilitate a single pass of heat exchange fluid through the heat exchanger 100 between the fluid inlet nozzle 108 and the fluid outlet nozzle 112. This fluid flow is illustrated as a dotted line 116 traveling in one pass (from right to left) through the bundle 104 at the top of FIG. 1. The E-to-F conversion assembly 106 positioned inside the shell 102 is configured to facilitate two passes of heat exchange fluid through the conversion assembly 106 between the fluid inlet nozzle 108 and the fluid outlet nozzle 112. This fluid flow is illustrated as a dotted line 118 traveling in two passes (from left to right, then from right to left) through the E-to-F conversion assembly 106 at the bottom of FIG. 1. The dotted line 118 shows the fluid entering the shell 102 at the fluid inlet nozzle 108, traveling from right to left in the shell 102 (outside the E-to- F conversion assembly 106), and then entering the E-to-F conversion assembly 106 at an inlet 120 on the left side of the assembly, allowing for two passes to be made through the E-to-F conversion assembly 106. As such, the E-to-F conversion assembly 106 allows shell side fluid to enter the conversion assembly 106 at the same end of the shell as the fluid outlet nozzle 112, causing the heat exchanger 100 to function as an F-type heat exchanger with two shell fluid passes.

[0028] The illustrated E-type bundle 104 includes a stationary tube sheet 122 to which a plurality of tubes (not shown) are coupled. The tubes may be U-shaped tubes or straight tubes coupled to a distal floating head type closure to provide two passes of tube fluid. The tubeside fluid flows into a tube fluid inlet 124 of a channel 125, passes through the tube sheet 122 into the connected tubes, flows through the tubes in two passes, and then exits a tube fluid outlet 126 from the channel 125 during operation of the heat exchanger. The E-type bundle104 also includes a plurality of baffles 128 through which the tubes extend. The shell fluid is routed around the baffles 128, as shown, during its single pass from right to left through the heat exchanger 100.

[0029] The illustrated E-to-F conversion assembly 106 includes a stationary tube sheet 130 to which a plurality of tubes (not shown) are coupled. The tubes may be U-shaped tubes or straight tubes coupled to a distal floating head type closure to provide two passes of tube fluid. The tube-side fluid flows into the tube fluid inlet 124, passes through the tube sheet 130 into the connected tubes, flows through the tubes in two passes, and then exits the tube fluid outlet 126 during operation of the heat exchanger. The E-to-F conversion assembly 106 also includes a plurality of baffles 132 through which the tubes extend. The shell fluid is routed around the baffles 132 and around a larger horizontal baffle 202, as shown, during its two passes through the E-to-F conversion assembly 106.

[0030] The E-type bundle 104, including the tube sheet 122, the connected tubes, and the connected baffles 128, may be removed from the shell 102 in a single extraction operation after removing the channel 125. The E-to-F conversion assembly 106 may include the tube sheet 130, the connected tubes, the connected baffles 132 or other supports, and a shroud 134, 500 surrounding the tubes and baffles 132. The shroud 134, 500 may define the inlet 120 into the E-to-F conversion assembly 106. The E-to-F conversion assembly 106 may be inserted into the shell 102 in a single insertion operation after removing the channel 125 and extracting the E-type bundle 104. As such, the disclosed E-to-F conversion assembly 106 may allow for pulling the internal components of the E-type heat exchanger and replacing them with F-type internal components without changing any of the existing external piping (e.g., shell fluid inlet nozzle 108, shell fluid outlet nozzle 112, tube fluid inlet 124, and tube fluid outlet 126). As a result, no altering of external piping is needed to perform the reconfiguration of the heat exchanger 100 from an E-type exchanger to an F-type exchanger.

[0031] It should be noted that the direction of fluid flow (for both shell and tube fluids) through the heat exchanger 100 are not limited to the directions shown in FIG. 1. For example, the tube fluid may be input at the bottom of the channel 125 and output at the top of the channel 125. As another example, the shell fluid inlet nozzle 108 may be located at the top of the shell 102 and the shell fluid outlet nozzle 112 may be located at the bottom of the shell 102. Additionally or alternatively, the shell fluid inlet nozzle 108 may be located on the left side of the shell 102 (closer to the channel 125) and the shell fluid outlet may be located on the right side of the shell 102 (further from the channel 125). Any combination of these positions of different fluid inlets and outlets may be possible without departing from the scope of the present disclosure,as long as the inlet and outlet fluid nozzles 108 and 112 are located proximate opposite longitudinal ends of the shell 102.

[0032] In general, the disclosed E-to-F conversion assembly 106 includes: a stationary tube sheet 130; multiple tubes coupled to the tube sheet 130; baffles or supports through which one or more tubes of the multiple tubes extend a hollow cylindrical shroud coupled to the tube sheet, wherein the shroud encompasses the tubes and baffles or supports; and a semi- circumferential seal coupled to an external surface of the shroud and extending halfway around the shroud in a circumferential direction. FIGS. 2-8 illustrate two example embodiments of the disclosed E-to-F conversion assembly 106, which will now be described.

[0033] FIG. 2 is a perspective view of an example E-to-F conversion assembly 106. A heat exchanger 100 having the E-to-F conversion assembly 106 installed in the E-type shell 102 is shown in FIGS. 3A and 3B. FIG. 3A shows a first end 110 of the tube and shell heat exchanger 100, while FIG. 3B shows a second end 114 opposite the first end 110. As illustrated, the shell 102 has the fluid inlet nozzle 108 proximate the first end 110 and a fluid outlet nozzle 112 proximate the second end 114. FIG. 3B includes arrows demonstrating the flow of shell fluid through the shell portion of the heat exchanger 100.

[0034] In the embodiment of FIGS. 2-3B, the E-to-F conversion assembly 106 includes the tube sheet 130 and a plurality of heat exchanger tubes (tubes) 200 coupled to the tube sheet 130. In the illustrated embodiment, each tube 200 extends in a first direction away from the tube sheet 130 before turning and extending in a second direction back to the tube sheet 130. As such, the tubes 200 are “U-tubes.” The heat exchanger tubes 200 may bend around the distal end of a longitudinal baffle 202 of the E-to-F conversion assembly 106. In other embodiments, the tubes 200 coupled to the tube sheet 130 may include multiple straight tubes coupled to the top part of the tube sheet 130 (at upper portion of the channel 125) and multiple straight tubes coupled to the lower part of the tube sheet 130 (at lower portion of the channel 125), with the straight tubes being connected at an opposite end to a floating head type closure that facilitates flow of tube fluid from a first set of tubes (on one side of the longitudinal baffle 202) to a second set of tubes (on the opposite side of the longitudinal baffle 202). In either configuration defined above, the tube fluid flows through multiple tubes in two passes (one pass above the longitudinal baffle in a first direction and another pass below the longitudinal baffle in a second direction).

[0035] The E-to-F conversion assembly 106 also includes a hollow, cylindrical shroud 134 disposed around the plurality of heat exchanger tubes 200 and coupled to the tube sheet 130. A plurality of baffles 132 or other supports may be coupled to the shroud 134 and located insidethe shroud 134, with one or more tubes of the heat exchanger tubes 200 passing through the baffles 132. The E-to-F conversion assembly 106 also includes a semi -circumferential seal assembly 204 coupled to an external surface of the shroud 134 and extending halfway around the shroud 134 in a circumferential direction. For example, the semi-circumferential seal assembly 204 may extend around the bottom half of the shroud 134, as shown. The semi- circumferential seal assembly 204 may generally extend around the half of the shroud 134 (e.g., bottom half, top half) that corresponds to the circumferential location of the shell fluid outlet nozzle 112.

[0036] The shroud 134 of the E-to-F conversion assembly 106 forces the incoming shell side fluid to flow into an annular region 206 between the shell 102 and the E-to-F conversion assembly 106, where it travels the length of the E-to-F conversion assembly 106 (e.g., from the first end 110 to the second end 114). Fluid traveling in the shell annular region 206 may encounter the semi-circumferential seal assembly 204 located around one half (e.g., lower half) of the shroud 134, which together with an adjacent longitudinal seal may force the fluid into the other half (e.g., upper half) of the shell annular region 206. As shown in FIG. 3B, the shroud 134 may terminate before the tube sheet 130 so that the shell fluid enters the shroud 134 proximate the second end 114 of the heat exchanger 100 and can contact the tubes 200 in the upper half of the shell 102. At this point, the shell fluid behaves as it would in a conventional F-type shell. That is, the shell fluid flows in the upper half of the shell 102 (inside the shroud 134), contacting the tubes 200, from the second end 114 of the shell 102 toward the first end 110 of the shell 102, then passes a second time through the lower half of the shell 102 (inside the shroud 134), contacting the tubes 200, from the first end 110 of the shell 102 back to the second end 114 of the shell 102. Thus, shell and tube fluids remain in counterflow throughout both tube passes. In essence, the E-to-F conversion assembly 106 properly locates the inlet shell fluid inside the shell 102 (as opposed to changing the exterior shell nozzle location(s)) to create a second shell fluid pass in the heat exchanger 100.

[0037] As illustrated most clearly in FIG. 2, the shroud 134 has a generally cylindrical shape, with a circular outer shape along its length. As shown in FIG. 3A, the cross section of the shroud 134 along most of its length has a radially outer surface 208 that is circular and a radially inner surface 210 (surrounding the heat exchanger tubes 200 and baffles 132) that is also circular. The radial thickness of the shroud 134 between the outer surface 208 and the inner surface 210 may be substantially uniform around the circumference and / or along the length of the shroud 134. This cylindrical construction of the shroud 134 is desirable because it enables a simpler construction of the shroud 134 than would be possible using other shroud shapes.

[0038] As shown most clearly in FIGS. 3A and 3B, the E-to-F conversion assembly 106 may include a longitudinal baffle 202 extending longitudinally through the shroud 134 (e.g., from the second end 114 of the E-to-F conversion assembly 106 toward the first end 110). The longitudinal baffle 202 may be coupled to and / or formed integrally with the tube sheet 130, as shown in FIG. 3A. The longitudinal baffle 202 may be planar and may generally bisect the shroud 134 along part of the length of the shroud 134 (from the second end 114 in a direction toward but not all the way reaching the first end 110). In the illustrated embodiment, the longitudinal baffle 202 divides the shell fluid section of the E-to-F conversion assembly 106 into two sections (e.g., an upper and a lower section) defining the two shell fluid “passes.” As illustrated, each heat exchanger tube 200 of the exchanger 100 may extend in a first direction away from the tube sheet 130 on a first (e.g., lower) side of the longitudinal baffle 202, and then turn around the end of the longitudinal baffle 202 at the second end 114 and extend in a second direction back to the tube sheet 130 on a second (e.g., upper) side of the longitudinal baffle 202. In other embodiments, a first group of multiple straight tubes 200 may extend in a first direction away from the tube sheet 130 on a first (e.g., lower) side of the longitudinal baffle 202 and connect to a floating head type closure at the end of the longitudinal baffle 202 at the second end 114, and a second group of multiple straight tubes 200 may extend in a second direction from the floating head type closure back to the tube sheet 130 on a second (e.g., upper) side of the longitudinal baffle 202.

[0039] In the embodiment of FIGS. 2-3B, the shroud 134 of the E-to-F conversion assembly 106 is constructed from two components (upper component 212 and lower component 214) that are connected along a length of the shroud 134. In other embodiments, e.g., as described below with reference to FIGS. 5-8, the shroud 134 may have a single component construction. As shown in FIG. 2, the two components 212 and 214 may be bolted, welded, or connected in some other manner together to form the cylindrical shroud 134. In the illustrated embodiment, the two components 212 and 214 are bolted (or otherwise attached) to a central piece of material 250, which may be the same as and / or coupled to the longitudinal baffle 202. Other methods of attaching the two components 212 and 214 may be used without departing from the scope of the present disclosure.

[0040] The shroud 134 may not extend all the way to the tube sheet 130. As illustrated, the shroud may have an open end located proximate the tube sheet 130 and a closed end 252 located distal from the tube sheet 130. There may be one or more openings formed in the shroud 134 (e.g., at the second end 114) for allowing shell fluid to flow to an appropriate location. These openings and / or the open end of the shroud 134 may function as the inlet 120 for shell fluid toflow into the shroud 134. The shroud 134 may similarly feature one or more openings and / or an open end on the opposite side (e.g., bottom side) of a longitudinal seal of the shroud 134 that functions as an exit for the shell fluid to flow from the shroud 134 to the shell outlet nozzle.

[0041] In some embodiments the shroud 134 may include one or more longitudinally oriented fins 254 coupled to the outer diameter of the main shroud body. The fins 254 may help to centralize the shroud 134 within the shell 102 as it is positioned inside and / or withdrawn from the shell 102. The fins 254 may also help direct fluid flowing through the annulus 206 to flow in the longitudinal direction from the first end 110 of the shell 102 to the second end 114 of the shell 102 for entering the shroud 134. As illustrated in FIGS. 2 and 3A, the fins 254 may be absent at a location along the length of the shroud 134 corresponding to a longitudinal location of the shell inlet nozzle 108. Similarly, the fins 254 may be absent at a location along the length of the shroud 134 proximate the circumferential seal assembly 204 and the opening / open end of the shroud 134 defining the inlet 120 (and exit) of the shroud 134.

[0042] As mentioned above, the E-to-F conversion assembly 106 may include additional baffles 132 inside the shroud 134. As shown in FIGS. 3A and 3B, for example, the E-to-F conversion assembly 106 includes a plurality of baffles 132 each extending in a plane that is perpendicular to a plane of the longitudinal baffle 202 and perpendicular to the longitudinal directions in which the heat exchanger tubes 200 extend. The baffles 132 create a tortuous path through which the shell fluid must flow within the shroud 134, forcing the shell fluid to contact the tubes 200 in a perpendicular direction several times during each pass, thereby improving heat exchange. The shroud 134 provides structural support for the baffles 132 used to direct the flow of shell fluid through the E-to-F conversion assembly 106.

[0043] Arrows drawn in FIG. 3B illustrate the direction of shell fluid flowing around two baffles 132 in the E-to-F conversion assembly 106. As illustrated, baffles 132 may be coupled to and extend inward from the radially inner surface 210 of the shroud 134. The baffles 132 may also be coupled at their opposite ends to the longitudinal baffle 202. The baffles 132 include holes formed therein through which heat exchanger tubes 200 extend.

[0044] Not all heat exchanger tubes 200 are illustrated in FIGS. 3 A and 3B, to provide visibility of the baffles 132 and other internal parts of the heat exchanger 100. As a person of ordinary skill in the art would recognize, the various holes shown in the tube sheet 130 in FIG. 3B would all connect to a corresponding heat exchanger tube 200. In some embodiments (e.g., having U-tubes), each heat exchanger tube 200 is connected to the tube sheet 130 at two locations (one location at the upper portion of the tube sheet 130 and the other at the lower portion of the tube sheet 130). In other embodiments (e.g., having a floating head type closure), each heatexchanger tube 200 is connected to the tube sheet 130 at a single location (either at the upper portion of the tube sheet 130 or at the lower portion of the tube sheet 130). The tube sheet 130 acts as a manifold between the upper and lower parts of the channel 125 and the heat exchanger tubes 200 directing tube fluid into and out of the shroud 134.

[0045] As mentioned above, the E-to-F conversion assembly 106 includes a semi- circumferential seal assembly 204. FIGS. 4A and 4B illustrate an example semi- circumferential seal assembly 204, which may be used with either of the E-to-F conversion assemblies 106 described with reference to FIGS. 2-3B or FIGS. 5-8.

[0046] As shown in FIGS. 4A and 4B, the circumferential seal assembly 204 may include a first semicircular shaped seal plate 400, a second semicircular shaped seal plate 402, two semicircular shaped seal elements 404 positioned between the first and second seal plates 400, 402, and a plurality of tie rods 406 positioned around the outer diameter of the shroud 134 and extending in a longitudinal direction of the shroud 134. Although two semicircular shaped seal elements 404 are shown in FIGS. 4A and 4B, other embodiments of the seal assembly 204 may include other numbers (e.g., 1, 3, 4, 5, 6, or more) of semicircular shaped seal elements 404. The first seal plate 400 may be connected (e.g., welded, bolted, etc.) to a circular outer diameter of the shroud 134. The second seal plate 402 is disposed around the outer diameter of the shroud 134. The second seal plate 402, however, is loose (not welded, bolted, etc.) with respect to the shroud 134. Each of the tie rods 406 is coupled to the second seal plate 402, and the tie rods 406 are configured to activate the circumferential seal by compressing the seal elements 404 between the first and second seal plates 400, 402. The tie rods 406 may be threaded rods that are double nutted at each end and threaded completely through the tube sheet 130. Spacer bars 408 (e.g., tubes) may be run over the threaded tie rods 406 from the shell side of the tube sheet 130 to the first seal plate 400.

[0047] The seal elements 404 may include trapezoidal shaped packing that is wedged between the first seal plate 400 and the second seal plate 402. Both seal plates’ circular edges that are in contact with the packing (404) may be chamfered at the same angle as the trapezoid-shaped packing. As the double-nutted tie rod 406 is turned by hand from the channel side of the tube sheet 130 (opposite the shell side of the tube sheet 130), the second seal plate 402 may be pulled against the packing (404), wedging it in a radially outward direction to seal against an inner diameter of the shell (e.g., 102 of FIGS. 3A and 3B) and upwards to seal against a short stretch of a longitudinal seal 410 extending from the tube sheet 130.

[0048] Multiple longitudinal seals 410 may be coupled to either side of the piece of material 250 between the two halves of the shroud 134. One such longitudinal seal 410 is shown inFIG. 4A, while two longitudinal seals 410 are shown in FIG. 4B. The longitudinal seals 410 may form fluid tight seals between the radially inner surface of the surrounding shell and the shroud 134 along a length of the shroud 134 extending from the tube sheet 130 to a location at or beyond the semi-circumferential seal assembly 204.

[0049] As shown in FIG. 4B, the tube sheet 130 may be counterbored at the threaded tie rod holes, and a hollow plug forging 412 may be threaded to seal a plug gasket (not shown) against the tube sheet 130. The hollow interior of the plug gasket is long enough to accommodate the travel required for the threaded rod 406 to seat the packing (404).

[0050] FIGS. 5-8 provide another example of an E-to-F conversion assembly 106. FIG. 5 is a perspective view of an example E-to-F conversion assembly 106 without any of the heat exchanger tubes shown. A heat exchanger 100 having the E-to-F conversion assembly 106 installed in the E-type shell 102 is shown in FIG. 8. A cutaway view of the heat exchanger 100 in FIG. 6 shows a sealing interface between the shroud 500 and the tube sheet 130. FIG. 7 shows a more detailed view of the second end of the E-to-F conversion assembly (with heat exchanger tubes 200 shown). As illustrated in FIG. 8, the shell 102 has the fluid inlet nozzle 108 proximate the first end 110 and the fluid outlet nozzle 112 proximate the second end 114. Although no arrows are shown, the flow of shell fluid through the shell portion of the heat exchanger 100 of FIGS. 5-8 will be similar to that shown and described above with reference to FIGS. 2-3B.

[0051] The E-to-F conversion assembly 106 of FIGS. 5-8 is similar to the E-to-F conversion assembly 106 of FIGS. 2-3B. Like elements indicated in FIGS. 5-8 have the same structure and function as those described at length above with respect to FIGS. 2-3B. As illustrated in FIGS. 7 and 8, the E-to-F conversion assembly 106 includes the tube sheet 130 and a plurality of heat exchanger tubes (tubes) 200 coupled to the tube sheet 130. In the illustrated embodiment, each heat exchanger tube 200 extends in a first direction away from the tube sheet 130 before turning and extending in a second direction back to the tube sheet 130. As such, the tubes 200 are “U-tubes.” The heat exchanger tubes 200 may bend around the distal end of the longitudinal baffle 202 of the E-to-F conversion assembly 106. In other embodiments, the tubes 200 coupled to the tube sheet 130 may include multiple straight tubes coupled to the top part of the tube sheet 130 (at upper portion of the channel 125) and multiple straight tubes coupled to the lower part of the tube sheet 130 (at lower portion of the channel 125), with the straight tubes being connected at an opposite end to a floating head type closure that facilitates flow of tube fluid from a first set of tubes (on one side of the longitudinal baffle 202) to a second set of tubes (on the opposite side of the longitudinal baffle 202). In either configurationdefined above, the tube fluid flows through multiple tubes in two passes (one pass above the longitudinal baffle in a first direction and another pass below the longitudinal baffle in a second direction).

[0052] The E-to-F conversion assembly 106 also includes a hollow, cylindrical shroud 500 (similar to shroud 134 described above) disposed around the plurality of heat exchanger tubes 200 and coupled to the tube sheet 130. A plurality of baffles 132 or other supports may be coupled to the shroud 500 and located inside the shroud 500, with one or more tubes of the multiple tubes 200 passing through the baffles 132. The E-to-F conversion assembly 106 also includes a semi-circumferential seal assembly 204 coupled to an external surface of the shroud 500 and extending halfway around the shroud 500 in a circumferential direction. For example, the semi-circumferential seal assembly 204 may extend around the bottom half of the shroud 500, as shown.

[0053] As illustrated most clearly in FIG. 5, the shroud 500 has a generally cylindrical shape, with a circular outer shape along its length. As shown in FIG. 8, the cross section of the shroud 500 along most of its length has a radially outer surface 502 that is circular and a radially inner surface 504 (surrounding the heat exchanger tubes 200 and baffles 132) that is also circular. The radial thickness of the shroud 500 between the outer surface 502 and the inner surface 504 may be substantially uniform around the circumference and / or along the length of the shroud 500. This cylindrical construction of the shroud 500 is desirable because it enables a simpler construction of the shroud 500 than would be possible using other shroud shapes.

[0054] The shroud 500 of FIGS. 5-8 has a similar structure to the shroud 134 described above with reference to FIGS. 2-3B except for the following. In FIGS. 5-8, the shroud 500 is formed of a single cylindrical piece of material having cutouts 506 formed therein. This may improve the ease of manufacturing the shroud 500 compared to the shroud 134 of FIGS. 2-3B, since the cylinder does not need to be manufactured then split in half and connected back together again, etc. The cutouts 506 may include one or more openings on one side (e.g., top) of the shroud 500 for allowing shell fluid to enter the shroud 500, as well as one or more cutouts 506 at the opposite side (e.g., bottom) of the shroud 500 for allowing shell fluid to exit the shroud 500. The shroud 500 has an open end located proximate the tube sheet 130 and a closed end located distal from the tube sheet 130. As illustrated in FIG. 6, the shroud 500 includes a flange 508 at its open end, and the flange 508 is configured to be sealingly engaged with a surface of the tube sheet 130. Sealing a flange 508 of the shroud 500 to the tube sheet 130 may prevent any shell fluid from unintentionally flowing around the circumference of the tube sheet 130 and bypassing the shroud 500.

[0055] To sealingly engage the flange 508 with the tube sheet 130, a circumferential gasket type seal 510 may be positioned between the flange 508 of the shroud 500 and the surface of the tube sheet 130. This gasket type seal 510 may be similar to another larger diameter gasket type seal 512 that is used to seal between a flange 514 of the shell 102 and a surface of the tube sheet 130. Using a similar seal 510 for the shroud 500 as the seal 512 used for the shell 102 may facilitate a simple installation process, since heat exchanger operators will already be familiar with how to position and activate this type and arrangement of seal against the tube sheet 130.

[0056] Assembling the E-to-F conversion assembly 106 of FIGS. 5-8 may include manufacturing the single piece, cylindrical shroud 500, connecting the heat exchanger tubes 200, the tube sheet 130, the baffles 132 or other supports, and longitudinal baffle 202, then sliding the tubes 200, tube sheet 130, and baffles into the cylindrical shroud 500 before sealingly coupling the shroud 500 to the tube sheet 130.

[0057] The shroud 500 of FIGS. 5-8 may include a semi-circumferential seal attachment component 516 and a longitudinal seal attachment component 518 formed along an outer surface of the shroud 500. These attachments components 516, 518 may be integrally formed with the rest of the one-piece shroud 500. The semi -circumferential seal attachment component 516 may be used to attach the semi-circumferential seal assembly 204 to the shroud 500, while the longitudinal seal attachment component 518 may be used to attach one or more longitudinal seals 410 to the shroud 500.

[0058] In some embodiments the shroud 500 may include one or more longitudinally oriented fins 520 coupled to the outer diameter of the main shroud body. The fins 520 may help to centralize the shroud 500 within the shell 102 as it is positioned inside and / or withdrawn from the shell 102. The fins 520 may also help direct fluid flowing through the annulus 206 to flow in the longitudinal direction from the first end 110 of the shell 102 to the second end 114 of the shell 102 for entering the shroud 500. As illustrated in FIG. 5, the fins 520 may be absent at a location along the length of the shroud 500 corresponding to a longitudinal location of the shell inlet nozzle 108. Similarly, the fins 520 may be absent at a location along the length of the shroud 500 proximate the circumferential seal assembly 204 and the openings 506 of the shroud 500 defining the inlet 120 and / or exit for the shroud 500.

[0059] The shroud 500 of FIGS. 5-8 has a similar function to the shroud 134 described above with reference to FIGS. 2-3B. For example, the shroud 500 forces incoming shell side fluid to flow into an annular region 206 between the shell 102 and the E-to-F conversion assembly 106, where it travels the length of the E-to-F conversion assembly 106 (e.g., from the first end 110to the second end 114). Fluid traveling in the shell annular region 206 may encounter the semi- circumferential seal assembly 204 and / or the longitudinal seal(s) 410, which force the fluid into the other half (e.g., upper half) of the shell annular region 206. The shell fluid may enter the shroud 500 via the one or more openings 506 so that the shell fluid enters the shroud 500 proximate the second end 114 of the heat exchanger 100 and can contact the tubes 200 in the upper half of the shell 102. At this point, the shell fluid behaves as it would in a conventional F-type shell. That is, the shell fluid flows in the upper half of the shell 102 (inside the shroud 500), contacting the tubes 200, from the second end 114 of the shell 102 toward the first end 110 of the shell 102, then passes a second time through the lower half of the shell 102 (inside the shroud 500), contacting the tubes 200, from the first end 110 of the shell 102 back to the second end 114 of the shell 102. Thus, shell and tube fluids remain in counterflow throughout both tube passes. In essence, the E-to-F conversion assembly 106 properly locates the inlet shell fluid inside the shell 102 (as opposed to changing the exterior shell nozzle location(s)) to create a second shell fluid pass in the heat exchanger 100.

[0060] The E-to-F conversion assembly 106 of FIGS. 5-8 may include a longitudinal baffle 202 extending longitudinally through the shroud 500 (e.g., from the second end 114 of the E- to-F conversion assembly 106 toward the first end 110). The longitudinal baffle 202 may be coupled to and / or formed integrally with the tube sheet 130, as shown in FIG. 8. The longitudinal baffle 202 may be planar and may generally bisect the shroud 500 along part of the length of the shroud 500 (from the first end 110 in a direction toward but not all the way reaching the second end 114). In the illustrated embodiment, the longitudinal baffle 202 divides the shell fluid section of the E-to-F conversion assembly 106 into two sections (e.g., an upper and a lower section) defining the two shell fluid “passes.” As illustrated, each heat exchanger tube 200 of the exchanger 100 may extend in a first direction away from the tube sheet 130 on a first (e.g., lower) side of the longitudinal baffle 202, and then turn around the end of the longitudinal baffle 202 at the second end 114 and extend in a second direction back to the tube sheet 130 on a second (e.g., upper) side of the longitudinal baffle 202. In other embodiments, a first group of multiple straight tubes 200 may extend in a first direction away from the tube sheet 130 on a first (e.g., lower) side of the longitudinal baffle 202 and connect to a floating head type closure at the end of the longitudinal baffle 202 at the second end 114, and a second group of multiple straight tubes 200 may extend in a second direction from the floating head type closure back to the tube sheet 130 on a second (e.g., upper) side of the longitudinal baffle 202.

[0061] The E-to-F conversion assembly 106 may include additional baffles 132 inside the shroud 500. As shown in FIG. 8, for example, the E-to-F conversion assembly 106 includes a plurality of baffles 132 each extending in a plane that is perpendicular to a plane of the longitudinal baffle 202 and perpendicular to the longitudinal directions in which the heat exchanger tubes 200 extend. The baffles 132 create a tortuous path through which the shell fluid must flow within the shroud 500, forcing the shell fluid to contact the tubes 200 in a perpendicular direction several times over the course of each pass, thereby improving heat exchange. The baffles 132 of FIG. 8 may have a similar shape and / or arrangement as the baffles 132 described above with reference to FIGS. 3A and 3B. The shroud 500 provides structural support for the baffles 132 used to direct the flow of shell fluid through the E-to-F conversion assembly 106.

[0062] Not all heat exchanger tubes 200 are illustrated in FIGS. 7 and 8, to provide visibility of the baffles 132 and other internal parts of the heat exchanger 100. As a person of ordinary skill in the art would recognize, the various holes shown in the tube sheet 130 in FIG. 8 would all connect to a corresponding heat exchanger tube 200. In some embodiments (e.g., having U-tubes), each heat exchanger tube 200 is connected to the tube sheet 130 at two locations (one location at the lower portion of the tube sheet 130 and the other at the upper portion of the tube sheet 130). In other embodiments (e.g., having a floating head type closure), each heat exchanger tube 200 is connected to the tube sheet 130 at a single location (either at the upper portion of the tube sheet 130 or at the lower portion of the tube sheet 130). The tube sheet 130 acts as a manifold between the upper and lower parts of the channel (e.g., 125 of FIG. 1) and the heat exchanger tubes 200.

[0063] Different examples of semi-circumferential seal assemblies 204 are shown in FIGS. 9- 13. Although these seal assemblies 204 are shown positioned on a one-piece shroud 500 as described with reference to FIGS. 5-8, similar seal assemblies 204 may be used with the two- piece shroud 134 of FIGS. 2-3B as well.

[0064] FIG. 9 illustrates an example semi-circumferential seal assembly 204 that includes a semicircular shaped seal element 900 held between two semicircular shaped seal plates 902 connected to an outer diameter of the shroud 500. The semicircular shaped seal plates 902 may form part of the shroud 500. The semicircular shaped seal element 900 may include a traditional packing seal element. Although only one semicircular shaped seal element 900 is shown in FIG. 9, in other embodiments more than one seal element 900 may be positioned between the seal plates 902 and used to seal a circumferential space between the shroud 900 and a shell. If the semi -circumferential seal assembly 204 is disposed on the bottom portion ofthe shroud 900 (e.g., as shown in FIGS. 2-8 above), the weight of the overall E-to-F conversion assembly 106 may provide an additional force to engage and activate the seal element(s) 900 so they can effectively seal against the shell.

[0065] FIGS. 10 and 11 illustrate another example semi-circumferential seal assembly 204, which includes: a first semicircular shaped seal plate 1000 connected to an outer diameter of the shroud 500, a second semicircular shaped seal plate 1002 disposed around the outer diameter of the shroud 500, one or more semicircular shaped seal elements 1004 positioned between the seal plates 1000 and 1002, and one or more bolts and / or tie rods (not shown) coupled to the second seal plate 1002. The bolts and / or tie rods are configured to activate the circumferential seal by compressing the seal element(s) 1004 between the first and second seal plates 1000, 1002. This semi-circumferential seal assembly 204 is similar to the assembly shown and described with reference to FIGS. 4A and 4B, although the bolts and / or tie rods are not shown in FIGS. 10 and 11. The bolts and / or tie rods are meant to bring at least a portion of the second seal plate 1002 toward the first seal plate 1000 to activate the seal element(s) 1004 into sealing contact with the shell inner diameter. The first semicircular shaped seal plate 1000, as shown, may provide a relatively flat surface against which the seal element 1004 can be squeezed. The semicircular shaped seal plate 1000 may form part of the shroud 500. As illustrated, the second semicircular shaped seal plate 1002 may be a two-part component with a tapered interface between the components. For example, the second seal plate 1002 may include both a driving wedge 1002 A (not directly attached to the seal element(s) 1004) and a seal activating wedge 1002B (attached to the seal element(s) 1004). Movement of the driving wedge 1002 A in the longitudinal direction toward the first seal plate 1000 causes the seal activating wedge 1002B to move toward the first seal plate 1000, land on a shoulder of the first seal plate 1000, and then expand radially outward to activate the seal element(s) 1004.

[0066] FIGS. 12A-13 illustrate another example semi-circumferential seal assembly 204, which is a spring-loaded seal assembly. The seal assembly 204 of FIGS. 12A and 12B may include a self-energizing spring 1200, a thrust block assembly 1202, a primary seal 1204, and a secondary seal 1206. The thrust block assembly 1202, as shown, may include two components 1202 A, 1202B with a tapered interface 1208 between the components. The primary seal 1204 may be coupled to a radially outward facing surface of the first component 1202A of the thrust block assembly 1202. The secondary seal 1206 may be coupled to a radially outward facing surface of the second component 1202B of the thrust block assembly 1202. The spring 1200 may be positioned against a side of the second component 1202B opposite the tapered interface 1208. The tapered interface 1208 is configured to translate alongitudinal force on the first thrust block component 1202 A (from the self-energizing spring 1200) into a radially outward force on the second thrust block component 1202B (to compress / engage the primary seal 1204). The spring 1200 and thrust block assembly 1202 may be held between two circumferential seal plates (together referred to as element 1210). A portion of one of the circumferential seal plates may maintain the second component 1202B in a consistent radial position between the shroud 500 and the shell 102. FIG. 13 illustrates an arrangement of multiple self-energizing springs 1200 against the semicircular shaped thrust block assembly 1202, in accordance with certain embodiments.

[0067] FIG. 12A shows the shroud 500 (along with the rest of the E-to-F conversion assembly located in the shroud 500) being inserted into the shell 102, and FIG 12B shows the shroud 500 (and internal components) being extracted from the shell 102. During the insertion (FIG. 12A), the spring 1200 exerts a longitudinal force on the thrust block assembly 1202, which translates to a radially outward force on the primary seal 1204 to engage the primary seal 1204 against the inner diameter of the shell 102. The spring 1200 may be configured to provide a minimum amount of force required to provide engagement of the primary seal 1204 with the shell 102. The secondary seal 1206 may be proud relative to the primary seal 1204 while unengaged. With the semi-circumferential seal assembly 204 positioned at the lower half of the shroud 500, as shown, the weight of the E-to-F conversion assembly bears down on the secondary seal 1206. As a result, as the E-to-F conversion assembly is pushed into the shell 102 (FIG. 12A), the friction of the secondary seal 1206 may also engage the primary seal 1204 and help to push it down. During the extraction of the shroud 500 from the shell 102 (FIG. 12B), the reverse would happen in that the secondary seal 1206 would take some relief off the primary seal 1204 for easier extraction. Upon relieving the thrust block force, the rest of the seal assembly 204 can break free such that both seals 1204 and 1206 would only be slightly engaged with the shell 102.

[0068] Although not shown, in some embodiments, the semi-circumferential seal assembly 204 of FIGS. 12A and 12B may include a locking system (e.g., a bolt lock system) to lock the primary seal 1204, the secondary seal 1206, or both out of contact with the shell inner diameter while the shroud 500 (and internal components of the bundle) are being initially inserted into the shell 102. The locking system may then provide a means by which an operator can “unlock” the system from outside the shell 102 so that the seal assembly can be self-energized using the spring 1200 and the thrust block assembly 1202.

[0069] FIG. 14 is a process flow diagram illustrating a method 1400 for changing an E-type heat exchanger into an F-type heat exchanger without changing the shell of the heat exchanger,in accordance with presently disclosed techniques. At block 1402, the method 1400 includes removing a heat exchanger bundle from a heat exchanger shell. The heat exchanger shell includes a fluid inlet nozzle at a first longitudinal end of the shell and a fluid outlet nozzle at a second longitudinal end of the shell opposite the first longitudinal end. At block 1404, the method 1400 includes replacing the heat exchanger bundle with an E-to-F conversion assembly inserted into the heat exchanger shell. The E-to-F conversion assembly is configured to facilitate two passes of heat exchange fluid through the heat exchanger between the fluid inlet nozzle and the fluid outlet nozzle. The E-to-F conversion assembly includes: a tube sheet, heat exchanger tubes coupled to the tube sheet and arranged in a two-pass configuration, baffles or supports coupled to the tubes, a hollow cylindrical shroud coupled to the tube sheet and enclosing the plurality of heat exchanger tubes and the baffles or supports, and a semi- circumferential seal coupled to an external surface of the shroud and extending halfway around the shroud in a circumferential direction. The E-to-F conversion assembly may include additional heat exchanger technology features such as improved coatings, tube arrangements, baffle arrangements, etc. to improve the heat transfer available through the newly configured heat exchanger. Regular bundle extraction equipment (e.g., a bundle puller) may be used to perform the removal of the original heat exchanger bundle at block 1402. Regular bundle insertion equipment may be used to perform the insertion of the E-to-F conversion assembly at block 1404. At block 1406, the method 1400 may include activating the semi-circumferential seal to engage the seal with an inner diameter of the heat exchanger shell.

[0070] It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of example embodiments. For example, the functions described above and implemented as the best mode for operating the present invention are for illustration purposes only. Other arrangements and methods may be implemented by those skilled in the art without departing from the scope and spirit of this invention. Moreover, those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims

CLAIMSWhat is claimed is:

1. An E-to-F conversion assembly configured to be positioned inside an E-type heat exchanger shell to facilitate two passes of heat exchange fluid through the E-type heat exchanger shell, the conversion assembly comprising: a stationary tube sheet; multiple tubes coupled to the tube sheet; baffles or supports through which one or more tubes of the multiple tubes extend; a hollow cylindrical shroud coupled to the tube sheet, wherein the shroud encompasses the tubes and baffles or supports; and a semi-circumferential seal coupled to an external surface of the shroud and extending halfway around the shroud in a circumferential direction.

2. The conversion assembly of claim 1, wherein a cross section of the shroud along at least a portion of its length has a radially outer surface that is circular and a radially inner surface that is circular, wherein the radially inner surface surrounds the multiple tubes.

3. The conversion assembly of claim 1, further comprising a longitudinal baffle extending longitudinally through the shroud, wherein one or more tubes of the multiple tubes extend in a first direction away from the tube sheet on a first side of the longitudinal baffle, and wherein one or more tubes of the multiple tubes extend in a second direction back to the tube sheet on a second side of the longitudinal baffle opposite the first side.

4. The conversion assembly of claim 3, further comprising wherein the baffles each extend in a plane that is perpendicular to a plane of the longitudinal baffle and perpendicular to the first and second directions of the plurality of heat exchanger tubes.

5. The conversion assembly of claim 1, wherein the shroud comprises a single cylindrical shaped piece of material having one or more cutouts formed therein.

6. The conversion assembly of claim 1, wherein the shroud has an open end located proximate the tube sheet and a closed end located distal from the tube sheet, wherein theshroud comprises a flange at its open end that is sealingly engaged with a surface of the tube sheet.

7. The conversion assembly of claim 1, wherein the semi-circumferential seal comprises one or more semicircular shaped seal elements held between two semicircular shaped seal plates connected to an outer diameter of the shroud.

8. The conversion assembly of claim 1, wherein the semi-circumferential seal comprises: a first semicircular shaped seal plate connected to an outer diameter of the shroud; a second semicircular shaped seal plate disposed around the outer diameter of the shroud; one or more semicircular shaped seal elements positioned between the first and second seal plates; and one or more tie rods and / or bolts coupled to the second seal plate, wherein the tie rods and / or bolts are configured to activate a circumferential seal by compressing the seal elements between the first and second seal plates.

9. The conversion assembly of claim 1, wherein the semi-circumferential seal comprises a spring-loaded seal assembly.

10. A heat exchanger comprising: a shell comprising a fluid inlet nozzle at a first longitudinal end of the shell and a fluid outlet nozzle at a second longitudinal end of the shell opposite the first longitudinal end; an E-to-F conversion assembly positioned inside the shell and configured to facilitate two passes of heat exchange fluid through the heat exchanger between the fluid inlet nozzle and the fluid outlet nozzle, the conversion assembly comprising: a stationary tube sheet; multiple tubes coupled to the tube sheet; baffles or supports through which one or more tubes of the multiple tubes extend; a hollow cylindrical shroud coupled to the tube sheet, wherein the shroud encompasses the tubes and baffles or supports; anda semi-circumferential seal coupled to an external surface of the shroud and extending halfway around the shroud in a circumferential direction.

11. The heat exchanger of claim 10, wherein a cross section of the shroud along at least a portion of its length has a radially outer surface that is circular and a radially inner surface that is circular, wherein the radially inner surface surrounds the multiple tubes.

12. The heat exchanger of claim 10, wherein the conversion assembly further comprises a longitudinal baffle extending longitudinally through the shroud, wherein one or more tubes of the multiple tubes extend in a first direction away from the tube sheet on a first side of the longitudinal baffle, and wherein one or more tubes of the multiple tubes extend in the second direction back to the tube sheet on a second side of the longitudinal baffle opposite the first side.

13. The heat exchanger of claim 12, wherein the baffles each extend in a plane that is perpendicular to a plane of the longitudinal baffle and perpendicular to the first and second directions of the plurality of heat exchanger tubes.

14. The heat exchanger of claim 10, wherein the shroud comprises a single cylindrical shaped piece of material having one or more cutouts formed therein.

15. The heat exchanger of claim 10, wherein the shroud has an open end located proximate the tube sheet and a closed end located distal from the tube sheet, wherein the shroud comprises a flange at its open end that is sealingly engaged with a surface of the tube sheet.

16. The heat exchanger of claim 10, wherein the semi-circumferential seal comprises one or more semicircular shaped seal elements held between two semicircular shaped seal plates connected to an outer diameter of the shroud.

17. The heat exchanger of claim 10, wherein the semi-circumferential seal comprises: a first semicircular shaped seal plate connected to an outer diameter of the shroud; a second semicircular shaped seal plate disposed around the outer diameter of the shroud;one or more semicircular shaped seal elements positioned between the first and second seal plates; and one or more tie rods and / or bolts coupled to the second seal plate, wherein the tie rods and / or bolts are configured to activate a circumferential seal by compressing the seal elements between the first and second seal plates.

18. The heat exchanger of claim 10, wherein the semi-circumferential seal comprises a spring-loaded seal assembly.

19. A method, comprising: removing a heat exchanger bundle from a heat exchanger shell comprising a fluid inlet nozzle at a first longitudinal end of the shell and a fluid outlet nozzle at a second longitudinal end of the shell opposite the first longitudinal end; and replacing the heat exchanger bundle with an E-to-F conversion assembly inserted into the heat exchanger shell, the conversion assembly configured to facilitate two passes of heat exchange fluid through the heat exchanger between the fluid inlet nozzle and the fluid outlet nozzle, the conversion assembly comprising: a stationary tube sheet; multiple tubes coupled to the tube sheet; baffles or supports through which one or more tubes of the multiple tubes extend; a hollow cylindrical shroud coupled to the tube sheet, wherein the shroud encompasses the tubes and baffles or supports; and a semi-circumferential seal coupled to an external surface of the shroud and extending halfway around the shroud in a circumferential direction.

20. The method of claim 19, further comprising activating the semi-circumferential seal to engage the seal with an inner diameter of the heat exchanger shell.

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