Patent Description:
Tube heat exchangers are very common in industry and have a very long history.

The basic concept has remained substantially unchanged over many years. However, as compared to other types of heat exchangers, tube heat exchangers are comparatively expensive, space requiring and not specifically efficient for heat recovery.

Two fluids, of different starting temperatures, flow through the heat exchanger. One flows through the tubes (the tube side) and the other flows outside the tubes but inside the tubular shell (the shell side). Heat is transferred from one fluid to the other through the tube walls, either from tube side to shell side or vice versa. The fluids can be either liquids or gases on either the shell or the tube side. If energy transferred to the cooling fluid should be utilized it is an advantage if flow paths are long and a flow arrangement is counter current flow. In this way, waste heat can be used efficiently.

In order to obtain an efficient utilization of the energy in the cooling fluid heat exchangers must have a long thermal length. For current types of tube heat exchangers this means the length of the tubes has to be very long.

Presently, tube heat exchangers are big, normally bigger than many other types of heat exchangers designed for the same load. Most tube heat exchangers are mounted with the tubular shell extending horizontally which will make them occupy a considerable area. Furthermore, they will require a service area almost as large as the tube heat exchanger. If a tube inside the tubular shell has to be exchanged it has to be withdrawn in an axial direction, which implicates that there needs to be an open space in the longitudinal extension of the tube heat exchanger, the length of the open space corresponding to the length of the tubes.

The structure of tube heat exchangers makes them sensitive to quick temperature changes, specifically heat exchangers using U-tubes. Several parts of the structure will be affected by an incoming as well an outgoing flow, one of which is hot and one cold. Such conditions can create tensions that may lead to defects or fractures in material during cyclic journal operation.

In a basic structure of a tube heat exchanger cooling of high pressure gas, the gas is directed through a bundle of tubes with a circular cross section. The bundle is provided within a tubular shell or a sheet casing. A circular cross section is optimal regarding the pressure. A flow of a cooling fluid circulates within the tubular shell. Different parts of the heat exchanger, such as tube plates, are exposed to the same pressure as the tubes. Therefore, the tube plates must be thick or as an alternative, the heat exchanger must be designed with a small diameter and have an extended length. Normally, the heat exchangers are designed with a small diameter and extended length which is a cost-effective solution. A working pressure of the cooling fluid within the tubular shell is considerably lower than the pressure of the gas. The tubular shell thickness normally is dimensioned based on the pressure of the cooling fluid, so as to keep costs as low as possible.

Should one or more tubes burst gas will enter a space inside the tubular shell. The pressure in this area will increase and if no outlets are provided also the tubular shell will burst. Since this course of events must be considered the tubular shell is provided with large openings to prevent that very high-pressure conditions arise within the tubular shell. During normal conditions, the large openings are closed by lids. The lids are designed to open or burst at a pressure level somewhat higher than the highest working pressure normally occurring within the tubular shell. This way bursting of the tubular shell can be prevented. As the tube heat exchangers normally are extended in length and have a small diameter they must be provided with a plurality of openings. As a result, the costs will increase. The openings are arranged to allow the gas to exit horizontally which call for a safety area around the heat exchanger where specific restrictions apply. Thus, the area that needs to be reserved for prior art tube heat exchangers is around five to ten times as large as the area of the tube heat exchanger as projected on the underlying ground. Since a normal length of an industrial tube heat exchanger can be <NUM>-<NUM>, the total required area will become very large.

From the above it is understood that there is room for improvements and the invention aims to solve or at least mitigate the above and other problems.

Additional features and advantages of the concepts disclosed herein are set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the described technologies. The features and advantages of the concepts may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the described technologies will become more fully apparent from the following description and appended claims, or may be learned by the practice of the disclosed concepts as set forth herein.

A tube heat exchanger disclosed herein is suitable for cooling and heating of gas at high pressures. In various embodiments, it can be designed with a compact footprint. In various embodiments, the thermal length of the disclosed tube heat exchanger is long, and the thermal fatigue resistance is high. It is possible to design the heat exchanger with comparatively thin tube plates and closing covers.

One application of the disclosed tube heat exchanger is cooling of gas at very high pressures. In industrial applications, large heat exchangers can be produced at reasonable costs without lower standards of safety.

In various embodiments, the disclosed tube heat exchanger is provided with an annular heat exchange space with a tube package arranged as an annular bundle of tubes. A tubular shell encloses the tubes, and a central chamber is provided in a space within the annular heat exchange space. The central chamber is connected to an outlet tube at one end of tubular shell for outlet of gas at high pressures. The annular shape of the bundle of tubes and an inner wall that enables leaking gas to flow radially from a cracked tube into the central chamber provide for a short distance from a tube fracture to the chamber. As a result, even at a large gas leak gas can be evacuated from the heat exchanger without a substantial risk of a gas pressure that is large enough to cause a rupture of the tubular shell.

The annular heat exchange shape also results in annular tube plates with a width that is much smaller than the tube plate diameter of a tube heat exchanger with circular tube plates having the same tube plate area which further decreases the requirements on the thickness of the tube plates. In the case of a rupture, gas will be directed out from the tube heat exchanger through said outlet tube. In various embodiments, the tube heat exchanger is mounted with the tubular shell oriented vertically. As a result, gas will flow straight upwards. The disclosed tube heat exchanger does not require a safety zone, and there is no need for a specific service area, because the tubes that are used are comparatively short and normally can be pulled out upwards. The area that must be reserved for the disclosed tube heat exchanger corresponds to the area that is projected on the underlying ground.

Another advantage with a heat exchange space with the annular tube package in accordance with the disclosed tube heat exchanger is that the tube plates and closing covers can be made considerably thinner than the tube plates and closing covers of conventional tube heat exchangers with the same cross sectional area of the tube package. One reason for this is that the width of the tube package will be much smaller than the diameter of a traditional tube package. Another reason is that it is possible to use a larger number of, but considerably smaller bolts arranged in one inner circle of bolts and one outer circle of bolts. Using smaller bolts will result in a shorter distance between the inner circle of bolts and the outer circle of bolts, and consequently in a lower bending moment in tube plates and closing covers. If the same cross sectional area of the tube package is maintained the thickness of an annular tube plate can be approximately one fourth of the thickness of a traditional tube heat exchanger.

A traditional tube heat exchanger that can be used for cooling down gas at high pressure, such as several hundreds of bars or tenths of megapascals, can be designed with a diameter of the tube package of up to <NUM>, and a thickness of the tube plates of several hundreds of millimeters. In a disclosed type of a tube heat exchanger, the width of the annular tube package of less than one third of said diameter.

By using an annular tube package, it is possible to obtain a heat exchanger with large thermal length without using extremely long tubes. This structure will allow a tube package divided into several sectors with tubes connected in series. As a result, an annular tube heat exchanger can have a very compact design even though it will provide a long thermal length.

In various embodiments, the sectors are divided by baffles into axially displaced segments. A flow path of the cooling fluid will be directed by the baffles and will extend radially in opposite directions in adjacent heat exchange segments.

In various embodiments, the flow of at least one fluid is divided into two separate flows that are directed through two flow paths from an inlet to an outlet. Preferably, the flows of both fluids are divided into two separate flows that are directed through two flow paths from an inlet to an outlet. As a result, there will be a more gradual variation in temperature in the material, and stress in the material can be limited.

The invention defines a tube heat exchanger for exchanging heat from a first fluid to a second fluid, comprising.

In order to best describe the manner in which the above-described embodiments are implemented, as well as define other advantages and features of the disclosure, a more particular description is provided below and is illustrated in the appended drawings. Understanding that these drawings depict only exemplary embodiments of the invention and are not therefore to be considered to be limiting in scope, the examples will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:.

Further, in the figures like reference characters designate like or corresponding parts throughout the several figures.

The embodiment shown in the figures relates to a heat exchanger <NUM> for a gaseous first fluid at high pressure using a liquid cooling fluid at low pressure.

<FIG> shows the tube heat exchanger from one side with a tubular shell <NUM> extending in a vertical direction. This is a preferred orientation of the tube heat exchanger <NUM> in use. All references to "upper" and "lower" are made in view of this orientation. In other orientations, "upper" and "lower" refer to opposite axial ends of tube heat exchanger. The tubular shell <NUM> is provided at a first end with a first annular tube plate <NUM> and at a second end with a second annular tube plate <NUM>. In various embodiments the first tube plate <NUM> is a lower annular tube plate and the second tube plate <NUM> is an upper annular tube plate. A first or lower annular closing cover <NUM> is attached to the first tube plate <NUM> and a second or upper annular closing cover <NUM> is attached to the second tube plate <NUM> with an outer screw joint 13a and inner screw joint 13b, c. also <FIG>. The upper closing cover <NUM> is provided with a first connection <NUM> for an inlet of a first fluid, such as gas, and a second connection <NUM> for an outlet of the first fluid. The tubular shell <NUM> is provided with a third connection <NUM> for an inlet of a second fluid, such as a cooling media, and a fourth connection <NUM> for an outlet of the second fluid. An upper section of the heat exchanger <NUM> is provided with an outlet tube <NUM> through which gas can exit, should a tube break. A lid <NUM> with lid screw joints 14a closes the outlet tube <NUM> during normal operation.

As shown in <FIG>, a curved section of the lid <NUM> is formed with embossed indications of fracture 12a that will cause the lid <NUM> to break at a predetermined pressure. In various embodiments, safety valves are used instead. All connections are symmetrically arranged in an imaginary plane P extending through a center line C of the tubular shell <NUM>.

<FIG> and <FIG> show schematically the basic structure of a heat exchange space <NUM> in which the heat exchange takes place, and flow paths of the two fluids. The heat exchange space <NUM> is enclosed by the lower tube plate <NUM>, the upper tube plate <NUM>, the tubular shell <NUM> and a tubular inner wall <NUM> extending around the center line C. Thus, the heat exchange space <NUM> is an annular gap between the inner tubular wall <NUM> the tubular shell <NUM>. The heat exchange space <NUM> is divided into six circular shaped heat exchange sectors <NUM>. The inlet and outlet, respectively, of the fluids are provided at diametrically opposed heat exchange sectors <NUM>. Each of these diametrically opposed heat exchange sectors <NUM> are considerably bigger than other sectors, so as to allow considerably higher flow rates. In various embodiments, these sectors <NUM> have a double size as compared to other sectors.

<FIG> shows six radially extending separating walls <NUM> forming six sectors, S1, S2A, S2B, S3A, S3B and S4, c. also <FIG>. The gas flow will enter the heat exchange space <NUM> through the inlet of the first connection <NUM> at an upper part of the sector S1 and will flow downwards. When the gas reaches a lower part of S1, it will be directed into the lower closing cover <NUM> where it is divided into two flow parts that are directed into the sectors S2A and S2B, respectively. The flow parts are substantially equal, and in various embodiments the flow parts have the same flow rate. The gas flows upwards as indicated in <FIG> through sectors S2A and S2B and then downwards through S3A and S3B, respectively, and finally through S4 and out through a first outlet duct <NUM> in the second connection <NUM> for outlet of gas. Arrows in <FIG> show the flow directions.

<FIG> shows how the cooling fluid flows through the sectors in opposite directions as compared to the gas. The cooling fluid enters the heat exchange space <NUM> in an upper area of S4 and flows downwards. In various embodiments, the flow of the cooling fluid is directed by baffles <NUM> in a crosscurrent flow to the flow of gas in a plurality of flow tubes <NUM>. In this way, the transfer of heat between the gas and the cooling fluid will be very efficient. The baffles <NUM> and the flow path are shown more in detail in sector S3B. This sector is shown with four baffles <NUM> that direct the cooling fluid to flow radially between the flow tubes <NUM>. The baffles <NUM> divide the sector S3B into five axially displaced segments SE1-SE5. Baffles <NUM> provided in each of the other sectors will divide the sector into axially displaced segments correspondingly. An arrow indicates the actual flow path. As shown in <FIG>, the flow path of the cooling fluid will extend radially in opposite directions in adjacent heat exchange segments. A flow passage is provided between adjacent heat exchange segments to provide a flow path of the second fluid in a vertical direction between the adjacent heat exchange segments.

The cooling fluid will enter the sector S3B from the sector S4 through a first opening <NUM> in the radially extending separating wall <NUM> below a lower one of the baffles <NUM>. There is a second opening <NUM> between the baffle <NUM> and the tubular shell <NUM> extending along the periphery of the tubular shell <NUM>. The cooling fluid will be directed through the second opening <NUM> up into a space between the lower baffle and an adjacent baffle above the lower baffle. Between the following baffle and the inner wall <NUM> there is a third opening <NUM> extending along the periphery of the inner wall <NUM>. The cooling fluid will be directed through the third opening <NUM> up into a space between the following baffle and a further adjacent baffle above. The second opening <NUM>, the third opening <NUM> and optionally further openings will provide the flow path of the second fluid in a vertical direction between the adjacent heat exchange segments.

In a corresponding process, the cooling fluid flows further upwards to a space between an uppermost baffle <NUM> and the upper tube plate <NUM>. The radially extending separating wall <NUM> is provided with a fourth opening <NUM> through which the cooling fluid will flow into the sector S2B. The main flow direction of the cooling fluid is from the bottom to the top in the sector S3B which is opposite to the main direction of the flow of the gas, c. <FIG>, and from the top to the bottom in sector S2B. There are provided also further openings (not shown) in other radially extending separating walls <NUM>, so as to allow the cooling fluid to flow into an adjacent heat exchange sector <NUM>. The flow of the cooling fluid enters the heat exchange space <NUM> in an upper area of S4 and is separated into two flow paths as indicated by arrow FC1. The two flow paths will be united in sector S1, where the flow of the cooling fluid will exit from the heat exchange space <NUM> as indicated by arrow FC2. Other sectors are provided with baffles <NUM> similar to how they are provided in sector S3B, and the gas and the cooling fluid flow in opposite directions in all sectors. This is advantageous with respect to efficiency, should the energy in the heated cooling fluid be taken advantage of. At least one baffle <NUM> is used in the disclosed tube heat exchanger. The positioning and number of openings <NUM>-<NUM> and optionally further openings are chosen with respect to the number of baffles <NUM> to obtain a preferred flow path of the cooling fluid through the different segments.

The cross sectional view in <FIG> from line I-I <FIG> coincides with the plane P. A first gas inlet duct <NUM> at the first connection <NUM> for inlet of gas directs the gas to a first chamber <NUM> in the upper closing cover <NUM> and further through the plurality of flow tubes <NUM> in the heat exchange sector S1 down to a first distributing chamber <NUM> in the lower closing cover <NUM> where the flow of gas is separated into two flows of gas. In various embodiments, the two flows of gas are equal. After passing through flow tubes of the sectors S2A and S3A and S2B and S3B, respectively, the two flows of gas will enter a second chamber <NUM>. A common flow of gas then will flow through the flow tubes of heat exchange sector S4 to a third chamber <NUM> and further out through the first outlet duct <NUM> in the second connection <NUM> for outlet of gas.

A second inlet duct <NUM> in the third connection <NUM> for inlet of cooling fluid directs the cooling fluid into a fluid distributing chamber <NUM> and further through inlet openings <NUM> in the tubular shell <NUM> and into an uppermost and first heat segment of sector S4. As shown in <FIG>, each sector is divided by six baffles <NUM> into seven segments. The cooling fluid will flow through the third opening <NUM> down into a lower segment and the radially towards the tubular shell <NUM>. The cooling fluid will flow down through different segments of sector S4 and then through different sectors and out of the disclosed heat exchanger through a second outlet duct <NUM> at the fourth connection <NUM> for outlet of cooling fluid as described above with reference to <FIG>.

In the center of the disclosed heat exchanger there is provided a central chamber <NUM> that is connected to a lower opening <NUM> and an upper opening <NUM>' of the lower tube plate <NUM> and the upper tube plate <NUM>, respectively. The lower opening <NUM> is closed with a bottom lid <NUM>. An outlet tube <NUM> for the gas is provided at the upper opening <NUM>'. The outlet tube <NUM> is connected to the upper tube plate <NUM> with a set of tube screw joints 14b. The inner wall <NUM> is provided with an aperture <NUM> at an inlet area <NUM> for the cooling fluid. As a result, the central chamber <NUM> will be filled with cooling fluid and the pressure inside the central chamber <NUM> will be the same or higher than the pressure outside the central chamber <NUM>.

<FIG> shows a cross section III-III in <FIG>. The disclosed heat exchanger is symmetrically arranged around the plane P that cuts through all connections. As disclosed above, the heat exchanger is provided with six radially extending walls <NUM> forming the six sectors, S1, S2A, S2B, S3A, S3B and S4. In this embodiment, there are three radially extending walls <NUM> on either side of the plane P. Thus, the medias will pass through four sectors. In the embodiment shown in <FIG>, the inner wall <NUM> comprises eight panels <NUM> that are retained by screws <NUM> or stud bolts <NUM> and nuts <NUM>. The area depicted V in <FIG> is shown enlarged in <FIG>. The number of panels <NUM> can be more or less than in the shown embodiment, such as ten or six panels <NUM>, and the panels <NUM> can be flat, or curved as indicated in <FIG>.

In the embodiment shown in <FIG>, the panels <NUM> are attached by the screws <NUM> along edges thereof to flanges <NUM> that are welded to the radially extending separating walls and to inner edges of connecting baffles <NUM>. In various embodiments, other attachment means, such as stud bolts, rivets or other connections are used. Since there is a higher pressure in the central chamber <NUM> than in the heat exchange space <NUM> due to a pressure drop in the heat exchange space <NUM> there will be pressure load on the panels <NUM>. In various embodiments, the panels <NUM> are curved and the load will cause only membrane stress during normal conditions. As a result, comparatively thin material can be used. Tangential forces will be carried by a strip <NUM> that is fixedly mounted to the edges of the curved panels, such as by welding. The screws <NUM> will secure the curved panels and compress a gasket <NUM>, so as to minimize leakage between the central chamber <NUM> and the heat exchange space <NUM>. Should there be tube breakage causing a major leakage of gas, the pressure in the heat exchange space <NUM> will increase over a level where the curved panels will burst or come loose and release gas into the central chamber <NUM>. A required differential pressure for the release of gas can be predetermined by adjusting the breaking load and number of screws <NUM>.

In the embodiment shown in <FIG>, the screws are replaced by the stud bolts <NUM> and the nuts <NUM>. In this embodiment, the nuts have a comparatively low strength limit. When there is a leakage of gas, there will be a shear failure in the threads of the nuts <NUM> and the panels will come loose allowing the gas to exit from the tube heat exchanger. Still, the panels <NUM> as well as the stud bolts <NUM> will remain intact and can be use again. In this embodiment, the panels <NUM> are thicker which will provide in a higher bending strength. As a result, the panels will be sufficiently rigid to carry the pressure load. Thus, no further arrangements are required to absorb any membrane stresses.

<FIG> is a cross sectional view through the complete heat exchanger as seen perpendicularly to line IV-IV of <FIG>. The flow path of the cooling fluid is depicted by arrows C and circles with either a cross or a dot. A cross indicates that the flow direction is towards the center while a dot indicates that the flow direction is out from the center. The flow direction of the gas is marked at the first gas inlet duct <NUM> and the first outlet duct <NUM>, and the first chamber <NUM>, the first gas distributing chamber <NUM>, the second gas distributing chamber <NUM>, a third gas distributing chamber <NUM> and the second chamber <NUM> of the lower closing cover <NUM> and the upper closing cover <NUM>.

<FIG> is a cross section of an upper part from line II-II of <FIG>. The figure shows that threaded pins of the outer screw joints 13a, the inner screw joints 13b and the tube screw joints 14b of the outlet tube <NUM> are mounted in threaded dead end holes in the upper tube plate <NUM> and extend up through the upper closing cover <NUM> and a tube flange <NUM>. The cross section II-II cuts through a partition <NUM> between the first chamber <NUM> and the third gas distributing chamber <NUM> in the upper closing cover <NUM> and the radially extending separating wall <NUM> between the sectors S1 and S2B, c. Gas sealing rings <NUM> and <NUM> seals off the gas, and a fluid sealing ring <NUM> forms a barrier for the cooling fluid.

The number of radially extending separating walls <NUM> and the number of baffles <NUM> will determine how different connections are arranged in relation to each other. <FIG> and <FIG> disclose alternative embodiments for inlets and outlets of the gas and the cooling fluid. If the number of radially extending separating walls <NUM> on each side of the imaginary plane P is uneven the first connection <NUM> for inlet of gas and the second connection <NUM> for outlet of gas will be located at the same end of the heat exchanger, as shown in <FIG>. The embodiment of the heat exchanger <NUM> shown in <FIG> comprises four radially extending separating walls <NUM> and six baffles <NUM> in each heat exchange sector <NUM>. This is the same number of baffles <NUM> as in the embodiment shown in <FIG>, and as a result, the cooling fluid is directed into the heat exchange sector <NUM> through a fifth opening <NUM> in the inner wall <NUM>. In this embodiment, the cooling fluid is conveyed into the heat exchanger <NUM> through a third connection inlet <NUM>' in the bottom lid <NUM>. The cooling fluid is directed from the third connection inlet <NUM>', and through the central chamber <NUM> and the fifth opening <NUM> into one of the heat exchange sectors <NUM>, as indicated by arrow CI.

In the embodiment shown in <FIG>, there are provided only five baffles <NUM> in the heat exchange sector S4 where the cooling fluid is entering the heat exchanger <NUM>. A fourth connection inlet <NUM>" is provided in the tubular shell <NUM> to secure a consistent flow of cooling fluid throughout the heat exchange sector S4.

Claim 1:
A tube heat exchanger (<NUM>) for exchanging heat from a first fluid to a second fluid, comprising
a tubular shell (<NUM>);
an inner wall (<NUM>) extending around a center axis of said tubular shell (<NUM>) and forming a central chamber (<NUM>) internally of said inner wall (<NUM>), and an annular heat exchange space extending externally of said inner wall (<NUM>) and enclosed by said tubular shell (<NUM>), wherein the heat exchange space comprises a plurality of axially extending heat exchange sectors (<NUM>) separated by radially extending separating walls (<NUM>), and flow paths of the first fluid and the second fluid extend in the heat exchange space, wherein adjacent heat exchange sectors (<NUM>) communicate;
a set of flow tubes (<NUM>) extending axially in each of said heat exchange sectors (<NUM>) in said heat exchange space;
a first connection (<NUM>) for inlet of the first fluid to a first set of flow tubes (<NUM>), and a second connection (<NUM>) for outlet of said first fluid;
at least one radially extending baffle (<NUM>) dividing said heat exchange sectors (<NUM>) into at least two axially displaced heat exchange segments, wherein the central chamber (<NUM>) communicates with at least one opening in a tubeplate, and wherein a flow passage is provided between adjacent heat exchange segments to provide a flow path of the second fluid in a vertical direction between the adjacent heat exchange segments;
a third connection (<NUM>) for inlet of the second fluid to a first heat segment of a heat exchange sector, and a fourth connection (<NUM>) for outlet of said second fluid;
wherein a first flow path of said first fluid and a second flow path of said second fluid are divided to flow by a first portion clockwise and a second portion anti-clockwise through the axially extending heat exchange sectors (<NUM>),
wherein a flow path of the second fluid extends radially in opposite directions in adjacent heat exchange segments in the heat exchange sectors (<NUM>), and a flow path of the first fluid extends perpendicular to the flow path of the second fluid.