Indirect heat exchanger pressure vessel with controlled wrinkle bending section

Abstract

In one aspect of the disclosure, an indirect heat exchanger pressure vessel is provided that includes an inlet header for receiving a pressurized working fluid, such as water, glycol, ammonia, and / or CO2. The indirect heat exchanger pressure vessel includes an outlet header for collecting the pressurized working fluid and a serpentine tube connecting the inlet header and the outlet header. The serpentine tube allows the pressurized working fluid to flow from the inlet header to the outlet header. The serpentine tube includes a piping section and a return bend connecting the piping sections. The return bend has a controlled corrugation with alternating ridges and grooves. The alternating ridges and grooves strengthen the return bend and allow the indirect heat exchanger pressure vessel to facilitate heat transfer of the working fluid at high internal operating pressures.

Description

[Technical Field]

[0001] Cross-reference of related applications

[0001] This application claims the interests of U.S. Provisional Patent Application No. 63 / 138,655, filed on 18 January 2021, and U.S. Provisional Patent Application No. 63 / 270,953, filed on 22 October 2021, both of which are incorporated herein by reference in their entirety.

[0002]

[0002] The present disclosure relates to an indirect heat exchanger, and more particularly to an indirect heat exchanger having a meandering circuit tube having a plurality of formed bends, which transports a pressurized working fluid through the meandering circuit tube and enables heat transfer between the working fluid inside the meandering circuit tube and the fluid outside the meandering circuit tube. The working fluid and the external fluid may each be a gas, a liquid, or a mixture of a gas and a liquid. [Background technology]

[0003]

[0003] Heat exchangers are known, including direct heat exchangers and indirect heat exchangers. Direct heat exchangers transfer heat between a working fluid and another fluid through fluid-to-fluid contact. Indirect heat exchangers transfer heat between a working fluid and another fluid indirectly through a fluid-separating medium.

[0004]

[0004] Various types of heat exchange devices are known, including direct heat exchangers, indirect heat exchangers, or both. Known heat exchange devices include open-circuit heat exchangers, such as open-circuit cooling towers, and closed-circuit heat exchangers, such as closed-circuit cooling towers. Open-circuit cooling towers can exchange heat between a working fluid, such as water, and an external fluid, such as ambient air, by distributing the working fluid onto a packing material. The working fluid is cooled directly by the ambient air as the working fluid moves along the packing material. In contrast, closed-circuit cooling towers keep the working fluid isolated from the external fluid.

[0005]

[0005] Closed-circuit heat exchanger systems include closed-circuit cooling towers for fluids, evaporative condensers for refrigerants, dry coolers, air-cooled condensers, and ice thermal storage systems. These heat exchangers utilize one or more heat exchangers to transfer heat between a pressurized working fluid and an external fluid such as ambient air, an evaporative liquid, or a combination thereof.

[0006]

[0006] For example, a heat exchanger apparatus may include a closed-circuit cooling tower having an indirect heat exchanger pressure vessel which includes an inlet header that receives a pressurized working fluid, an outlet header, and an indirect heat exchange coil connecting the inlet header and the outlet header. The indirect heat exchange coil may include one or more meandering circuit tubes configured to transfer heat between a pressurized working fluid inside the indirect heat exchange coil and a fluid outside the indirect heat exchange coil, such as an evaporative liquid. The inlet header receives the internal working fluid from the upstream components of the heat exchanger, and the outlet header collects the pressurized working fluid before it is sent to the downstream components of the heat exchanger.

[0007]

[0007] Indirect heat exchanger pressure vessels, including inlet headers, outlet headers, and one or more meandering circuit tubes, must withstand high pressures suitable for specific applications and meet national and international technical standards such as ASME standard B31.5. For example, an indirect heat exchanger pressure vessel for a closed-circuit cooling tower may be rated to withstand an internal pressure of 150 psig for fluids such as water, glycol, and brine. As another example, an indirect heat exchanger pressure vessel for an evaporative condenser may be able to withstand an internal pressure of up to 410 psig or more for typical refrigerants such as ammonia or R-407C. As yet another example, some evaporative condensers have indirect heat exchanger pressure vessels with internal pressure ratings of 1200 psig or more for refrigerants such as CO2.

[0008]

[0008] The meandering circuit tubes of an indirect heat exchanger pressure vessel typically include straight sections and bends connecting the straight sections. The straight sections of the meandering circuit tubes are typically joined by bends of approximately 180 degrees, or by composite bends having multiple bends, such as two 90-degree bends joined by the length of the tube. The meandering circuit tubes can be stacked on top of each other during the assembly of the heat exchanger, typically with the meandering circuit tubes in contact with each other in the area of ​​the return bends, and with the meandering circuit tubes positioned alternately in the vertical direction.

[0009]

[0009] Meandering circuit tubes are often made by first forming elongated tubes from a long, flat piece of metal such as mild steel or stainless steel. The flat piece of metal is roll-formed into a generally circular cross-section, and the longitudinal edges are welded to each other by continuous longitudinal welding to form a straight tube. Another approach is to form a straight tube using a seamless tube forming process. The resulting straight tube can then be bent at spaced intervals along the tube to form a serpentine shape with straight pipe sections connected by bends. Tube bending is a complex process and often utilizes hydraulic, electric, or manual tube bending machines having bending dies, clamping dies, pressure dies, and optionally mandrels and wiper dies. Tube bending machines can be set to form bends with any desired angle of 180 degrees or less, such as 80 degrees, 90 degrees, 100 degrees, or 180 degrees. As described above, the return bend of the meandering circuit pipe may include a composite bend having two or more bends, such as an 80-degree bend and a 100-degree bend, connected by the length of the straight pipe.

[0010]

[0010] To form a bend in the pipe, the pipe is fed into a pipe bending machine, and a portion of the pipe is accommodated in the recess of the bending die. The pressure die and clamp die, which have recesses for the pipe, are moved relative to the opposite side of the pipe, thereby positioning the pressure die to support the pipe and the clamp die to clamp a portion of the pipe between the clamp die and the bending die. The pipe bending machine then rotates or swivels the bending die and clamp die over the desired bending angle. The pressure die moves forward as the bending die and clamp die swivel to support the pipe and ensure that the pipe follows the contour of the bending die. Once a bend is formed in the pipe, the clamp die and pressure die retract from their clamping positions, and the pipe is advanced until the location of the next bend in the pipe is positioned within the pipe bending machine, and the bending die, clamp die, and pressure die all return to their initial positions. The bending process is repeated for each bend formed in the meandering circuit pipe. Some pipes are bent only once to form a single-bend pipe, which is commonly referred to as a hairpin pipe or candy cane pipe, and can later be butt-welded to one another.

[0011]

[0011] Bending a pipe that receives a pressurized working fluid is a process that balances various considerations, including performance, safety, and packaging criteria for a particular application. Unintended deformation of the pipe wall during bending can lead to pipe breakage due to the pressure of the working fluid inside the pipe, pipe corrosion, and / or a higher pressure drop of the working fluid passing through the pipe. In some pipe bending processes, an internal mandrel is advanced inside the pipe to support the pipe wall during bending, and a wiper die may be used to harden the pipe wall at the inner rear end of the bend to prevent unintended deformation of the pipe. The internal mandrel may be a plug mandrel, or it may have one or more balls or rings, in which case the internal mandrel is referred to as a ball mandrel.

[0012]

[0012] Pipe bending generally involves the following parameters:

[0013]

[0013] OD = Outer diameter of the pipe

[0014]

[0014] WT = Wall thickness of the pipe

[0015]

[0015] CLR = Center line radius of the bent part

[0016]

[0016] Dimensions are measured using a common measurement scale such as inches or millimeters. These parameters are used to calculate the ratio of the following two characteristics.

[0017]

[0017]

[0018]

Number

[0018]

[0019] Two other parameters that are noted in bending are the outer radius (OSR) of the bent part, which is usually referred to as the extrados, and the inner radius (ISR) of the bent part, which is usually referred to as the intrados.

[0019]

[0020] The W ratio and the D ratio are further aggregated into a single coefficient that indicates the complexity of the bent part. This coefficient is calculated as follows.

[0020]

[0021]

Number

[0021]

[0022] W, D, and / or C BThe values ​​can be used to determine whether it is possible to form a bend without an internal mandrel, known as an empty bend, or whether an internal mandrel is required. In the latter case, the process is called a mandrel bend. With regard to mandrel bends, these ratios help determine whether the required internal mandrel should be a multi-ball mandrel, a single-ball mandrel, or a simpler plug mandrel. Ultimately, these ratios help determine whether a wiper die is required in combination with the internal mandrel. As an example, the following table shows processing recommendations for various bend complexities.

[0022] [Table 1]

[0023]

[0023] To determine the type of bending required, the W, D, and / or C lines on the industry standard pipe bending chart are used. B A typical approach is to examine the ratios. For example, to determine the processing parameters for bending a pipe with an outer diameter of 1'', a wall thickness of 0.05'', and a centerline radius of 2'', the ratios W and D are as follows:

[0024]

[0024]

[0025]

number

[0025]

[0026] Industry-standard pipe bending charts would recommend that, given a W ratio of 20 and a D ratio of 2, a regularly pitched internal mandrel with one ball should be used, with the addition of a wiper die.

[0026]

[0027] Substituting this, the C of the example bend shown above is B It will be as follows:

[0027]

[0028]

number

[0028]

[0029] Referring to the table above, this C B The values ​​also indicate that an internal mandrel is recommended, but a wiper die may be optional. The small difference in recommendations for mandrels and wipers indicates some flexibility in the configuration of the bend, and the absence of an internal mandrel and / or wiper die may be compensated for by the tool design and choice of pipe material.

[0029]

[0030] Conventional bending charts used in industry and the aforementioned bending complexity value (C B The range is based on the assumption that the contour of the tooling groove formed by the bending die and clamping die that seat the pipe during bending is circular, complementing the shape of the round pipe. However, bending tool design has made several advances in recent years, and bending tooling with a compound radius in the tooling groove is designed to compress and support the pipe during bending, expanding the range of air bending from approximately 5 to approximately 12 C B It is possible to expand this to include values.

[0030]

[0031] In addition to this, especially C B As the ratio approaches and exceeds 20, it becomes increasingly necessary to use internal mandrels and wiper dies to properly bend the pipes. Internal mandrel bending has several drawbacks, including the need for additional tooling and thus increased costs, the potential for increased scrap if the mandrel is not used correctly, the potential for increased cycle time, and the need for lubricants, which increases the time and cost of lubrication and subsequent environmental mitigation.

[0031]

[0032] C BOne problem when approaching and exceeding 20 is that the associated mandrel bending places a limit on the continuous length of the tube. The serpentine circuit tube can be very long and, in some applications, can be up to 400 feet in length. The physical limitations on the length of the mandrel rod and setup mean that an internal mandrel cannot be used to bend a long, continuous serpentine circuit tube with several bends. This forces the manufacturer to form one or two bends in short segments of the tube, sometimes called candy canes, and then butt weld those tube segments together to create a larger circuit. This not only involves additional labor and cost, but the additional butt welding increases the potential for leaks and, in many applications, may not be acceptable due to the high operating pressures the serpentine circuit tube will be subjected to.

[0032]

[0033] C B Another problem that can occur when approaching and exceeding 20 is that the associated internal mandrel bending can move the neutral axis of the bend closer to the inside of the bend, causing excessive thinning of the outer wall portion of the bend. Thinning of the outer wall portion of the bend can weaken the serpentine circuit tube, and then the serpentine circuit tube may not be able to withstand the pressure of the working fluid for a particular application. Excessive thinning of the outer bend wall also results in variations in the processing when forming the bend, reducing the quality of the bend region.

[0033]

[0034] The above issues make it desirable for manufacturers to avoid using internal mandrels for bending pipes. One method to avoid using internal mandrels for pipes with a given OD is to increase the WT or increase the CLR to an appropriate value to bring the bend within the range of an open bend. Increasing the wall thickness (WT) may not be an option for manufacturers of products that do not require such relatively thick walls from an operational standpoint. In certain cases, thicker walls may increase the fluid-side pressure drop, make the product less thermally efficient, increase the weight of the assembly, and increase the material cost of the meandering circuit pipe. Also, increasing the CLR may not be an option if the meandering circuit pipe needs to fit into a given space due to other operational considerations. Increasing the CLR may, in some cases, have adverse effects on the overall thermal and hydraulic efficiency of the coil. [Overview of the Initiative]

[0034]

[0035] In one aspect of the present disclosure, an indirect heat exchanger pressure vessel is provided, comprising an inlet header for receiving a pressurized working fluid, an outlet header for collecting the pressurized working fluid, and a meandering circuit pipe connecting the inlet header and the outlet header, allowing the pressurized working fluid to flow from the inlet header to the outlet header. The pressurized fluid may be, for example, water, glycol, glycol mixtures, ammonia, or CO2. The pressurized fluid may be a liquid such as water, or a liquid / gas combination such as a refrigerant liquid and refrigerant vapor. The meandering circuit pipe comprises a piping section and a return bend section connecting the piping sections. The return bend section comprises a controlled wrinkled portion comprising alternating ridges and grooves. The controlled wrinkled portion of the return bend section provides a rigid structure that resists internal pressure during operation of the indirect heat exchanger pressure vessel. The controlled wrinkled portion also provides a structural bend centerline radius that is larger than the actual bend centerline radius of the return bend section. A larger structural bend centerline radius reduces the bend complexity coefficient of the return bend compared to the return bend of a conventional meandering circuit tube with the same outer diameter and wall thickness. The reduced bend complexity coefficient allows the return bend, with its controlled wrinkled portion, to bend without the use of an internal mandrel, which simplifies the manufacturing process of the meandering circuit tube.

[0035]

[0036] The disclosure also provides an indirect heat exchanger pressure vessel including an inlet header for receiving pressurized working fluid, an outlet header for collecting pressurized working fluid, and a meandering circuit tube connecting the inlet header and the outlet header to allow the flow of pressurized working fluid from the inlet header to the outlet header. The meandering circuit tube includes a piping section, a return bend connecting the piping section, and a contact at the junction between the return bend and the piping section. The return bend includes a bending angle and a controlled wrinkled portion. The controlled wrinkled portion is spaced apart from the contact along the meandering circuit tube and has an angular range smaller than the bending angle around the inside of the return bend. In this way, the controlled wrinkled portion may be formed using a bending die having a corresponding controlled wrinkle-forming feature smaller than the entire inner ring of the return bend, allowing the meandering circuit tube to slide longitudinally out of the bending die and increasing the speed at which the return bend can be formed on the meandering circuit tube. In one embodiment, the controlled wrinkled portion includes a ridge having an amplitude that is smaller near the contact point and increases as the wrinkled portion extends away from the contact point, thereby reducing resistance to the fluid flow through the return bend and reducing the internal fluid pressure drop at the return bend compared to a non-tapered or non-relaxed configuration of the wrinkled ridge.

[0036]

[0037] In another embodiment, an indirect heat exchanger pressure vessel is provided, comprising an inlet header for receiving pressurized working fluid, an outlet header, and a meandering circuit tube connecting the inlet header and the outlet header to facilitate the flow of pressurized working fluid from the inlet header to the outlet header. The meandering circuit tube comprises a pair of piping sections and a return bend connecting the piping sections. The return bend includes an inner portion having a sinusoidal pattern on the inner ring of the return bend, the sinusoidal pattern comprising peaks and valleys. The inner portion of the bend includes an arc pattern intersecting the sinusoidal pattern, the arc pattern comprising a peak arc intersecting the peaks and a valley arc intersecting the valleys. The intersecting sinusoidal and arc patterns provide a smooth, continuously curving side wall of the meandering circuit tube that reinforces the return bend against internal pressure. In one embodiment, the sinusoidal wave pattern has one or more end portions having shallower peaks and troughs and intermediate portions having deeper peaks and troughs, in order to reduce the internal fluid pressure drop across the return bend compared to a sinusoidal wave pattern having constant peak and trough sizes.

[0037]

[0038] The disclosure also provides a closed-circuit cooling tower including an indirect heat exchanger comprising a plurality of meandering circuit tubes having piping sections and return bends connecting the piping sections. The return bends include wrinkle bends having controlled wrinkle portions. The closed-circuit cooling tower comprises a blower operable to generate airflow over the meandering circuit tubes and an evaporative liquid distribution assembly configured to distribute evaporative liquid onto the meandering circuit tubes. The closed-circuit cooling tower further comprises a reservoir to receive evaporative liquid falling from the meandering circuit tubes and a pump operable to pump the evaporative liquid from the reservoir back to the evaporative liquid distribution assembly. The controlled wrinkle bends reinforce the meandering circuit tubes to withstand internal pressure from the working fluid within the meandering circuit tubes during the operation of the cooling tower. The controlled wrinkled bend also provides a structural centerline radius of the wrinkled bend that is larger than the actual centerline radius of the controlled wrinkled bend, providing a reduced bend complexity coefficient compared to the return bend of a conventional meandering circuit tube having the same outer diameter and wall thickness. The reduced bend complexity coefficient allows the controlled wrinkled bend to be bent without the use of an internal mandrel, which simplifies the manufacturing process of the meandering circuit tube. [Brief explanation of the drawing]

[0038] [Figure 1]

[0039] This is a perspective view of an indirect heat exchanger having a meandering circuit pipe, where the piping is connected by the bends in the meandering circuit pipe. [Figure 2]

[0040] This is a schematic diagram of a heat exchanger including a meandering circuit tube. [Figure 3]

[0041] This is a side view of a meandering circuit pipe having a piping section connected by a 180-degree bend. [Figure 4]

[0042] Figure 3 shows an enlarged view of the bent portion indicated within the dashed circle, showing the controlled wrinkled portion on the inside of the bent portion. [Figure 5]

[0043] This is a cross-sectional view taken along line 5-5 in Figure 4, showing the cross-section of the bent portion in the groove of the wrinkled area. [Figure 6]

[0044] This is a cross-sectional view along line 6-6 in Figure 4, showing the cross-section of the bent portion of the ridge in the wrinkled area. [Figure 7]

[0045] This is a cross-sectional view along line 7-7 in Figure 4, showing one cross-section of the piping section of the circuit tube. [Figure 8]

[0046] Figure 4 is a perspective view of the bent section, showing the wrinkled portion on the inside of the bent section and the smooth outer wall portion on the outside of the bent section. [Figure 9A]

[0047] The cross-sectional view of line 9A-9A in Figure 8 shows a sinusoidal pattern of wrinkled portions that are spaced apart from the contact point between the bent portion and the piping portion, such that the wrinkled portions have an angular range smaller than the 180-degree bending angle of the bent portion. [Figure 9B]

[0048] This is a cross-sectional view of another embodiment of a bent section, similar to Figure 9A, having wrinkled portions in which the amplitude of the sinusoidal ridges and valleys fluctuates. [Figure 9C]

[0049] This is a cross-sectional view of another embodiment of a bent section, similar to Figure 9A, having wrinkled portions in which the period and amplitude of the sinusoidal ridges and valleys vary. [Figure 10]

[0050] This shows the process for determining the sinusoidal pattern of the bent section. [Figure 11]

[0050] This shows the process of determining the sinusoidal pattern of the bent portion. [Figure 12]

[0050] This shows the process of determining the sinusoidal pattern of the bent portion. [Figure 13A]

[0050] This shows the process of determining the sinusoidal pattern of the bent portion. [Figure 13B]

[0050] This shows the process of determining the sinusoidal pattern of the bent portion. [Figure 14]

[0051] This is a graphic representation of a portion of the sinusoidal pattern in the wrinkled area of ​​the return bend, showing the peaks and valleys of the sinusoidal pattern. [Figure 15]

[0052] A geometric representation of a portion of the sine pattern of a returning bend that intersects with the arc pattern of the returning bend, wherein the arc pattern includes a peak arc that intersects with the peak of the sine pattern and a valley arc that intersects with the valley of the sine pattern. [Figure 16A]

[0053] Figure 15 is a graphical representation of a mountain arc, showing a mountain arc with a radius of curvature, an angular range, and a center, where the center lies radially inward from the centerline of the meandering circuit tube. [Figure 16B]

[0054] This is a geometric representation similar to Figure 16A of a mountain arc with a compound radius of curvature. [Figure 16C]

[0055] This is a geometric representation similar to Figure 16A of a mountain arc having a shape defined by a portion of an ellipse. [Figure 17A]

[0056] Figure 15 shows a geometric representation of a valley arc, which has the same radius of curvature as a mountain arc, a shorter angular range than a mountain arc, and a center, with the center located radially outward from the centerline of the pipe. [Figure 17B]

[0057] This is a geometric representation similar to Figure 17A of a valley arc with a compound radius of curvature. [Figure 17C]

[0058] This is a geometric representation similar to Figure 17B of a valley arc having a shape defined by a portion of an ellipse. [Figure 18]

[0059] Figure 15 is a perspective view showing a portion of the sine pattern, including the peak and valley arcs, and the continuous curved, wrinkled surface portion connecting the peak and valley arcs. [Figure 19]

[0060] This is a perspective view of a pipe bending machine, showing the bending die, pressure die, and clamp die. [Figure 20]

[0061] Figure 19 is a side view of the bending die, showing the ridges and grooves that form the corresponding ridges and grooves in the wrinkled portion of the pipe. [Figure 21]

[0062] Figure 19 shows the process of forming a bent section of a meandering circuit pipe using the pipe bending machine. [Figure 22]

[0062] Figure 19 shows the process of forming a bent section of a meandering circuit pipe using the pipe bending machine. [Figure 23]

[0062] Figure 19 shows the process of forming a bent section of a meandering circuit pipe using the pipe bending machine. [Figure 24]

[0062] Figure 19 shows the process of forming a bent section of a meandering circuit pipe using the pipe bending machine. [Figure 25]

[0062] Figure 19 shows the process of forming a bent section of a meandering circuit pipe using the pipe bending machine. [Figure 26]

[0062] Figure 19 shows the process of forming a bent section of a meandering circuit pipe using the pipe bending machine. [Figure 27]

[0063] Figure 19 is a plan view of the pipe bent using the pipe bending machine and the lower part of the bending die, showing the meshing engagement between the ridges of the bent, wrinkled portion and the ridges of the bending die. [Figure 28]

[0064] This is an elevation view of a bent section with a bending angle of 90 degrees. [Figure 29]

[0064] This is an elevation view of a bent section having a bending angle of 80 degrees. [Figure 30]

[0064] This is an elevation view of a bent section having a bending angle of 100 degrees. [Figure 31]

[0065] This is a cross-sectional view of a meandering circuit coil having piping whose cross-section gradually becomes flatter. [Figure 32]

[0066] This is an elevation view of a composite bend in a pair of meandering circuit tubes having three contact points in between, with each composite bend including an 80-degree bend and a 100-degree bend. [Figure 33]

[0067] This is an elevation view of a bent section having an asymmetrical wrinkle pattern. [Figure 34]

[0068] Figure 33 is a perspective view of the lower part of the bending die used to form the bent section. [Figure 35]

[0069] Figure 34 is a perspective view of the lower part of the bending die and the corresponding upper part of the bending die. [Figure 36]

[0070] This is a plan view of a pipe having a flattened cross-section, the pipe including a straight section and a return bend section having a wrinkled portion. [Figure 37A]

[0071] Figure 36 is a cross-sectional view along line 37A-37A, showing the elliptical cross-section of the pipe in the valley of the wrinkled portion. [Figure 37B]

[0072] Figure 36 is a cross-sectional view taken along lines 37B-37B, showing the elliptical cross-section of the pipe at the peak of the wrinkled portion. [Figure 37C]

[0073] Figure 36 is a cross-sectional view taken along line 37C-37C, showing the elliptical cross-section of the pipe in one of its straight sections. [Modes for carrying out the invention]

[0039]

[0074] With respect to Figure 1, an indirect heat exchanger pressure vessel such as a coil assembly 10 is provided, which can be used in heat exchange devices such as evaporative condensers, closed-circuit fluid coolers, or ice thermal storage systems. The coil assembly 10 includes an inlet header 12, an outlet header 14, and a meandering circuit pipe 16. Each meandering circuit pipe 16 includes a piping section 18 connected to a composite bend 21 which includes two 90-degree bends 23, 25 separated by a 180-degree bend 20 or a straight-length section 27. The meandering circuit pipe 16 allows the working fluid to flow from the inlet header 12 through the meandering circuit pipe 16 to the outlet header 14.

[0040]

[0075] With respect to Figure 2, a heat exchange device such as a cooling tower 24 is provided, which includes an external structure 26, one or more blowers 28 including blower blades 30 and one or more motors 32, a direct heat exchanger including packing material 34, and an indirect heat exchanger pressure vessel 36. The cooling tower 24 may be, in some examples, an evaporative condenser, a closed-circuit cooling tower, or a dry cooler heat exchanger. The indirect heat exchanger pressure vessel 36 includes an inlet header 38, one or more meandering circuit pipes 37 having circuit piping sections 39 and bends 40, and an outlet header 42. The inlet header 38 and the outlet header 42 may be reversed depending on the application. In some embodiments, the packing material 34 is located above the indirect heat exchanger pressure vessel 36 and / or the packing material 34 is located between the piping sections of the meandering circuit pipes 37.

[0041]

[0076] With respect to Figure 2, the cooling tower 24 includes an evaporative liquid distribution system 43, which includes a spray assembly 44 having spray nozzles or orifices 46 for distributing an evaporative fluid such as water onto the meandering circuit pipe 37 and the packing material 34. The evaporative liquid distribution system 43 includes a reservoir 50 for collecting the evaporative fluid from the packing material 34 and the coil 36, and a pump 52 for pressurizing the collected evaporative fluid through a pipe 54 to the spray assembly 44. The cooling tower 24 further includes one or more air inlets 35, inlet louvers 58 for preventing the evaporative liquid from escaping from the cooling tower 24, an air outlet 59, and an eliminator 56 for collecting water mist from the air before the air exits through the air outlet 59. A blower 28 is operable to generate or induce an upward airflow onto the meandering circuit pipe 37 and the packing material 34. In other embodiments, the cooling tower 24 may have one or more blowers configured to guide airflow in an upward, downward, or cross-flow direction to the indirect and / or direct heat exchangers of the cooling tower 24.

[0042]

[0077] Regarding Figure 3, a meandering circuit tube 70 is provided which can be used with a heat exchanger such as the coil assembly 10 of Figure 1 or the cooling tower 24 described above in Figure 2. The meandering circuit tube 70 includes an internal passage 72 and tubular side walls 74 extending around it. The meandering circuit tube includes an end portion 76 which can be connected to an inlet header and an end portion 78 which can be connected to an outlet header. Depending on the application, the end portion 76 may be connected to an outlet header instead, and the end portion 78 may be connected to an inlet header. The meandering circuit tube 70 includes piping sections 79 such as piping sections 80, 82 and a bend 84. In one embodiment, the piping sections 79 may be parallel. In other embodiments, one or more of the piping sections 80 extend in the short direction, for example, inclined toward each other, in order to allow the discharge of internal fluid. The meandering circuit tube 70 may be self-discharging, so that any liquid in the internal passage 72 moves downward toward the end portion 78 under the influence of gravity. The material of the meandering circuit tube 70, the outer diameter of the meandering circuit tube 70, the wall thickness of the side walls 74, the number of pipe sections 79, the length of the pipe sections 79, the number of bends 84, the angular range of the bends 84, the centerline radius of the bends 84, and the inner / outer rings of the bends 84 may be selected for a particular heat exchanger. As another example in this regard, instead of a single-angle bend 84 connecting a pair of pipe sections 79, the meandering circuit tube may have one or more bends 84, each containing a pair of bends such as 90 degrees connected by straight segments, similar to the composite bend 21 shown in Figure 1. The pipe sections 80 may have a circular cross-section throughout the pipe section 80. In other embodiments, the meandering circuit tube 70 includes one or more pipe sections 80 having a non-circular cross-section, such as an elliptical or obround cross-section.

[0043]

[0078] The meandering circuit tube 70 may be formed from a single straight pipe bent at spaced intervals along the pipe to form a bend 84. The meandering circuit tube 70 may also be formed by gradually rolling a long, slender piece of material into a tubular shape and welding the longitudinal edges of the long, slender piece to each other to form a single weld that extends along the length of the meandering circuit tube 70. Alternatively, the meandering circuit tube 70 may be made from a plurality of separately formed components. For example, the piping section 79 may be a separate component welded to the bend 84. Or, the meandering circuit tube 70 may be formed by welding separate lengths of a pipe to each other and then bending the longer welded pipe. The meandering circuit tube 70 may be made from a metallic material such as carbon steel or stainless steel.

[0044]

[0079] With respect to Figure 4, each bend 84 includes an inner ring 90, an outer ring 92, a controlled wrinkled portion 94 on the inside 96 of the bend 84, and a smooth outer surface 98 on the outside 100 of the bend 84. The controlled wrinkled portion 94 includes a continuously curved controlled wrinkled surface 134 consisting of ridges 114 and grooves 116. The continuously curved controlled wrinkled surface 134 is not interrupted by edges, corners, or flats to avoid areas of local stress. The continuously curved controlled wrinkled surface 134 is formed by the ridges 114 and grooves 116 of the bend 84, which are defined, at least in part, by intersecting sinusoidal patterns 110 and arc patterns 150, respectively, as will be described in more detail below with respect to Figure 15. The bend 84 shown in Figure 4 has a bending angle of 180 degrees. When this disclosure refers to a specific bending angle of a bent portion, that bending angle is intended to be an approximation, such as + / - 5 degrees. In some embodiments, all of the bent portions 84 of the meandering circuit tube 70 have controlled wrinkled portions 94. In other embodiments, fewer than all of the bent portions 84 have controlled wrinkled portions 94.

[0045]

[0080] The meandering circuit pipe 70 has a pipe centerline 102 that passes through the piping sections 80, 82 and extends into the bend 84. The controlled wrinkled section 94 is radially inward from its pipe centerline 102 and is separated from its pipe centerline by the side section 104. The smooth outer section 98 and side section 104 allow the bend 84 to be stacked with the bends of other meandering circuit pipes of a conventional configuration, similar to conventional pipes having smooth inner bends.

[0046]

[0081] Referring to Figure 4, in the inner ring 90 of the bent portion 84, the controlled wrinkled portion 94 has a sinusoidal pattern 110 in the inner ring 90 of the bent portion 84, as described below with respect to Figures 8 and 9A. The wrinkled portion 94 includes a series of alternating ridges 114 and grooves 116. In one embodiment, the bent portion 84 has relief portions 222,224 between the sinusoidal pattern 110 and the contact points 122,124 between the piping portions 80,82 and the bent portion 84. The relief portions 222,224 facilitate the provision of a controlled wrinkled portion angle 240 that is smaller than the bending angle 220, as will be described in more detail below. The relief portions 222,224 extend from the contact points 122,124 to points 216,218. The wrinkled portion 94 further includes tapered introductory portions 140, 142 extending between points 216, 218 and point 400 (see Figure 4) where the sinusoidal wave pattern 110 begins and ends. In one embodiment, the relief portions 222, 224 each have a first radius, and the tapered introductory portions 140, 142 each have a smaller second radius. The sinusoidal wave pattern 110 begins at one point 400 and extends through the peaks 130 of the end ridge 118 until it reaches the other point 400, undulating through the ridges 114 and grooves 116, and extending through the peaks 132 of the end ridge 120.

[0047]

[0082] The ridge 114 includes end ridges 118, 120 which optionally have tapered inlet portions 140, 142. The tapered inlet portions 140, 142 provide a smooth transition between the relief portions 222, 224 and the sinusoidal pattern 110. The tapered inlet portions 140, 142 smooth the flow of the working fluid through the bend 84 and assist the flow of the material in the bend 84 during bending. The tapered inlet portions 140, 142, the ridge 114, and the groove 116 reduce the internal fluid pressure drop caused by the working fluid flowing through the bend 84. Additionally, the tapered tip portion 140 facilitates better discharge of the meandering circuit tube 70. The bend 84 may have both tapered inlet portions 140, 142 if the working fluid can flow through the bend 84 in either direction 143, 145. If the working fluid flows through the bent section 84 in only one direction 143,145, the bent section 84 may have only one tapered introduction section 140,142.

[0048]

[0083] Regarding Figure 9B, a cross-sectional view of the bend 84' is provided, which is similar to the bend 84 and has a sinusoidal pattern 110' along the midline of the bend 84'. The bend 84' has ridges 114' and grooves 116' whose amplitudes vary around the bend 84'. Specifically, the ridges 114' and grooves 116' closer to the piping sections 80', 82' have smaller amplitudes, while the ridges 114' and grooves 116' near the center of the bend 84' have larger amplitudes. For example, ridges 114A', 114B' have larger amplitudes than ridges 114C', 114D'. The more gradual increase in amplitude of the ridges 114' and grooves 116' reduces the resistance to fluid flow through the bend 84', thereby reducing the pressure drop across the bend 84' compared to the bend 84 in some applications. A gentler increase in the amplitude of the ridges 114' and grooves 116' may also reduce the stress in the material of the bend 84' during bending compared to the bend 84 in some applications. In other embodiments, the amplitude of the sinusoidal pattern of the bend 84' may increase from one adjacent pipe section connected to the bend 84' to the other adjacent pipe section connected to the bend 84'.

[0049]

[0084] With respect to Figure 9C, a cross-sectional view of the bent portion 84'' is provided, which is similar to the bent portion 84 and has a controlled wrinkled portion 94'' with a sinusoidal pattern 110'' on the inner ring of the bent portion 84''. The controlled wrinkled portion 94'' includes ridges 114'' and grooves 116''. The controlled wrinkled portion 94'' includes a first portion 115'' having ridges 114''A,B and grooves 116''A,B with a first amplitude and a first period 117''. The controlled wrinkled portion 94'' includes a second portion 119'' having ridges 114''C,D and grooves 116''C,D with a second amplitude greater than the first amplitude. The ridges 114''C,D and grooves 116''C,D have a second period 121'' smaller than the first period 117''. The controlled wrinkled portion 94'' further includes a third portion 123'' having ridges 114''E,F and grooves 116''E,F with a third amplitude substantially the same as the second amplitude of the second portion 119'' and a third period 125'' smaller than the second period 121''. The bent portion 84'' receives fluid in direction 127'', and the ridge 114''A includes a tapered introduction portion 129'' for smoothing the fluid flow through the bent portion 84''. The tapered introduction portion 129'' reduces the pressure drop across the bent portion 84'' and improves the discharge of fluid within the bent portion 84''.

[0050]

[0085] The characteristics of the sinusoidal pattern 110 used in a given return bend can be selected for a specific application. For example, the number of ridges / grooves, amplitude, period, and / or one or more tapered introduction portions can be selected for a specific application. The characteristics of the return bend can vary throughout the return bend, such as the amplitude and period which vary throughout the return bend. The shape of the controlled wrinkled portion 94 is formed, at least in part, by two different intersecting cross-sectional profiles. In relation to Figures 4 and 15, the controlled wrinkled portion 94 includes the sinusoidal portion 110 in the inner ring 90 of the bend 84. Another pattern is an arc pattern 150 including alternating crescent arcs 152 and valley arcs 154. Referring to Figures 16A and 17A, the crescent arc 152 has a crescent radius 152' and a center 182, and the valley arc 154 has a valley radius 158 and a center 172. In this embodiment, the peak arc 152 and the valley arc 154 are substantially the same. As used herein, the term substantially the same refers to dimensions that are virtually identical when considering manufacturing variations, such as within + / - 10% of each other. The peak arc 152 extends over an angle 160 that is greater than the angle 162 over which the valley arc 154 extends.

[0051]

[0086] Returning to Figures 5 and 15, the valley arc 154 forms a semicircular inner wall portion 170 of the valley, having a radius 158 and a center 172. Opposite the semicircular inner wall portion 170 of the valley, the bend 84 includes an outer wall portion 174, which may be semicircular. In some embodiments, the outer wall portion 174 may be curved with a flattened portion resulting from tension being applied to the outer ring 92 (see Figure 4) of the bend 84 during the bending process. The bend 84 includes connecting wall portions 176, 178 that connect the semicircular inner wall portion 170 of the valley to the outer wall portion 174. The connecting wall portions 176, 178 may have curvatures that are dissimilar to the inner and outer wall portions 170, 174. The connecting wall sections 176 and 178 provide a smooth transition between the geometries of the inner wall section 170 and the outer wall section 174, minimizing stress concentration at the joint between the geometries of the inner wall section 170 and the outer wall section 174. By reducing stress concentration at the joint between the geometries of the inner wall section 170 and the outer wall section 174, the connecting wall sections 176 and 178 help the bent section 84 withstand high internal operating pressures.

[0052]

[0087] In Figures 6 and 15, the arc 152 of the peak defines a semicircular inner wall portion 180 of the peak, having a radius 156 of the arc 156 together with the center 182. The bend 84 has an outer wall portion 184 opposite the semicircular inner wall portion 180 of the peak. Similar to the outer wall portion 174 (see Figure 5), the outer wall portion may be semicircular. In some embodiments, the outer wall portion 184 may be curved with a flattened portion resulting from tension being applied to the outer ring 92 (see Figure 4) of the bend 84 during the bending process. The bend 84 further includes connecting wall portions 186, 188 that connect the semicircular inner wall portion 180 of the peak and the outer wall portion 184. Similar to the outer wall portion 174, the outer wall portion 184 may have a semicircular or generally curved shape in some embodiments. Furthermore, the connecting wall sections 186 and 188 provide a smooth transition between the geometries of the inner wall section 180 and the outer wall section 184, minimizing stress concentration at the joint between the geometries of the inner wall section 180 and the outer wall section 184. The connecting wall sections 186 and 188 contribute to the ability of the bent section 84 to withstand high internal operating pressure. The crescent arc 152 and the valley arc 154 may each have a single radius, as shown in Figures 16A and 17A. In another embodiment, the crescent arc 152 and / or the valley arc 154 have a compound or composite radius. For example, referring to Figure 16B, the crescent arc 152' has different radii 156A', 156B'. Each radius of the crescent arc 152' is tangent to the adjacent radius at the point where that radius joins. Similarly, in Figure 17B, the valley arc 154' has different radii 158A', 158B'.

[0053]

[0088] In another embodiment, the peak arc 152 and / or valley arc 154 have shapes that are part of an ellipse. For example, the peak arc 152'' in Figure 16C is an arc defined by an angle 160'', such as 160 degrees, between points 426'',430'' of an ellipse 439 having a major axis 441 and a minor axis 443. Similarly, the valley arc 154'' in Figure 17C has a shape defined by an angle 162'', such as 142 degrees, between points 445,447 of an ellipse 449 having a major axis 451 and a minor axis 453.

[0054]

[0089] In Figure 7, the piping section 82 is shown, and the side wall 74 has a circular cross-section centered on the pipe centerline 102. The side wall 74 may also have a non-circular cross-section, such as an elliptical or oblong cross-section. The side wall 74 of the meandering circuit pipe 70 has a wall thickness 190 that extends around the internal passage 72.

[0055]

[0090] In Figure 8, parts of the piping sections 80 and 82 and the bent section 84 are shown in a perspective view. As described above, the controlled wrinkled portion 94 has a continuously curved controlled wrinkled surface 134, which includes curved ridge surface portions 200 on both sides of each ridge 114 and curved groove surface portions 202 on both sides of each groove 116 connecting the curved ridge surface portions of adjacent ridges 114. The ridge surface portions 200 and groove surface portions 202 form the continuous wavy appearance of the controlled wrinkled portion 94.

[0056]

[0091] With respect to Figure 9A, the meandering circuit pipe 70 has an outer diameter of 210 and a wall thickness of 190. The pipe centerline 102 extends through the piping sections 80, 82 and the bend 84. The meandering circuit pipe has joints 214, 215 between the piping sections 80, 82 and the bend 84. At the joints 214, 215, the pipe 70 includes contact points 122, 124 between the piping sections 80, 82 and the bend 84. The bend 84 includes reliefs 222, 224 extending away from the contact points 122, 124 and tapered introduction portions 140, 142 that incline radially inward toward the peaks 130, 132 of the end ridges 118, 120. The bend 84 has a center 230 and a centerline radius 232 extending from the center 230 to the pipe centerline 102. In the illustrated embodiment, the bent portion 84 has a bending angle 220 of 180 degrees, and the controlled wrinkled portion 94 extends around the center 230 over a controlled wrinkled portion angle 240 that is smaller than the bending angle 220. For example, the controlled wrinkled portion angle 240 may be 5° or less, 10° or less, or 15° or less than the bending angle 220. In one embodiment, the bending angle is 180 degrees, and the wrinkled portion angle 240 is approximately 166 degrees.

[0057]

[0092] Referring again to Figure 9A, the controlled wrinkled portion 94 positions the peaks 250 of the ridge 114 on the inner ring 90 of the bend 84 (see Figure 4) and the valleys 252 of the groove 116 radially outward from the peaks 250. By positioning the valleys 252 outside the inner ring 90 of the bend 84, the wrinkled portion 94 creates a structural bend centerline 254. The structural bend centerline 254 has a structural bend centerline radius 256 that is larger than the centerline radius 232 of the pipe centerline 102. Since the structural bend centerline radius 256 is larger than the bend centerline radius 232, the bend complexity ratio of the bend 84 to a given bend inner and outer ring is smaller than the bend complexity ratio of a conventional bend having the same inner ring, outer ring, outer diameter, and wall thickness. The bent section 84 has a lower bend complexity ratio due to its larger structural bend center radius 256.

[0058]

[0093] For example, a pipe bend for a specific application may have the following ratio of characteristics:

[0059]

[0094]

[0095]

[0096]

number

[0060]

[0097] However, OD refers to the outer diameter of the pipe, WT refers to the wall thickness, and CLR refers to the centerline radius of the bend. The ratios of these values ​​for the pipe bend are assumed to be as follows:

[0061]

[0098] W1=20 and D1=2, therefore C B1 =10

[0062]

[0099] Referring to Table 1 above, these values ​​indicate that internal mandrel bending may be necessary if a conventional pipe bending machine is used.

[0063]

[0100] Here, specific parameters of the bend are modified to exhibit improved meandering pipe characteristics such as a narrower bend radius for the same wall thickness, reduced coil weight, reduced internal fluid-side pressure drop, reduced bend wall stress, increased pipe strength, increased pipe stiffness, and / or increased heat transfer efficiency. These modifications affect the ratio of the characteristics. For example, the new characteristic ratios may be selected as follows:

[0064]

[0101] W2=30 and D1=2, therefore C B2 =15

[0065]

[0102] Consequently, the ratio of the characteristics of the complexity of the bend is now within a range that conventional pipe bending machines can no longer compensate for, and conventionally, an internal mandrel is used to perform this bending.

[0066]

[0103] Internal mandrel bending is often undesirable for various reasons mentioned above, making it impractical for manufacturers producing heat exchanger coils using long, continuous lengths of tubing.

[0067]

[0104] Referring again to Figure 9A, one way to eliminate the need for an internal mandrel is to reduce the complexity of the bend by increasing the CLR of the bend. In this example, if the CLR of the bend can be increased while keeping the outer diameter and wall thickness of the pipe the same, then increase the D of the bend from 2 to 3, and reduce the complexity of the bend as follows (C B ) The ratio can be obtained.

[0068]

[0105] W2=30 and D2=3, therefore C B2 =10

[0069]

[0106] C B2Since the ratio is in the range of 5 to 10, bends can be formed without an internal mandrel. However, simply increasing the bend CLR for a given application may not be acceptable because the new bend will be larger than the original bend and occupy more space. For example, the distance between the centers of the pipe sections will be greater, meaning that fewer pipe sections can fit a particular envelope or coil height. Also, since each bend in the meandering circuit tube will be bulkier, the meandering circuit tube will have fewer pipe sections for a given coil envelope or height, which will reduce the heat exchange capacity of the meandering circuit tube. Reducing the number of pipe sections in a meandering circuit coil to increase the bend CLR is not an acceptable solution for many applications.

[0070]

[0107] Referring again to Figure 9A, the controlled wrinkled portion 94 of the bend 84 provides a structural bend centerline radius 256 that is larger than the actual bend centerline radius 232 without increasing the distance between the pipe sections 80 and 82. The larger structural bend centerline radius 256 increases the CLR of the bend 84, which increases the D of the bend for a given OD, and also C B However, this allows the bending to be kept within a range where mandrel bending is not required.

[0071]

[0108] More specifically, the controlled wrinkled portion 94 provides a structural bend centerline 254 within the available space of the bend 84, thereby allowing sufficient length along the inside of the bend 84 so that the material forms ridges 114 and grooves 116 without buckling in a controlled manner. The wrinkled portion 94 also maintains or improves other coil properties such as internal fluid pressure drop and heat transfer efficiency. Other properties of the curved portion 84 are also improved, such as reduced thinning of the outer ring wall and overall stiffness of the curved portion 84.

[0072]

[0109] Referring to Figure 4, the alternating ridges 114 and grooves 116 of the controlled wrinkled section 94 provide space for the material of the tube 70 to fold when the tube 70 is bent, resulting in a smaller effective arc length. The material of the tube 70 folds into a sinusoidal pattern 110 along the inner ring of the bend 84. Specific variables of the sinusoidal pattern 110, such as the number of peaks / troughs, the depth of the troughs (amplitude of the sine wave), and the total arc length, are calculated for specific applications as described later. This method can be used to calculate variables related to various combinations of material, OD, WT, and CLR, as well as to optimize various properties such as pressure drop and thermal efficiency.

[0073]

[0110] The controlled wrinkled portion 94 offers advantages over conventional pipe bends. For example, compared to other bends with wrinkles, the sinusoidal pattern 110 minimizes stress generated within the material of the pipe 70, allowing for much higher internal fluid pressure. The ridges 114 and grooves 116, including tapered introductory portions 140, 142, can be sized to limit interference with fluid flow within the bend 84 and to minimize the internal fluid pressure drop through the bend 84. The sinusoidal pattern 110 increases the length of material along the inner ring 90, thereby increasing the total surface area of ​​the bend 84 and improving heat transfer efficiency by increasing fluid turbulence within the bend region, compared to conventional bends with the same bend centerline radius. In addition, the ridges 114 and grooves 116 act as corrugated structures that make the bend 84 more rigid compared to smooth, wrinkle-free bends. Furthermore, the controlled wrinkled portion 94 pushes the neutral axis of the bent portion 84 outward toward the outer ring 92 of the bent portion 84, thereby reducing the thinning of the material of the bent portion 84 along the outer ring compared to a smooth, wrinkle-free bent portion.

[0074]

[0111] Figures 10 to 13B provide a process for determining the geometry of the bend 84 of the meandering circuit tube 70 to replace the bend 306 of the conventional meandering circuit tube 300, while simultaneously fitting it within the coil envelope of the conventional meandering circuit tube 300 and utilizing a narrower bend radius for a given wall thickness.

[0075]

[0112] With respect to Figure 10, the conventional meandering circuit pipe 300 has piping sections 302, 304, a bent section 306, an outer diameter 308, and a wall thickness 310. The bent section 306 is a 180° bend and has an inner ring 312 and an outer ring 315 with an arc length 314. Initially, with respect to Figure 11, the meandering circuit pipe 70 has an outer diameter 210, the same as the outer diameter 308, and a wall thickness 190, which is smaller than the wall thickness 310. For example, both the outer diameter 308 and the outer diameter 210 may be 1.05 inches, the wall thickness 310 may be in the range of approximately 0.04 inches to approximately 0.07 inches, such as 0.048 inches, and the wall thickness 190 may be in the range of approximately 0.02 inches to approximately 0.05 inches, such as approximately 0.03 inches to approximately 0.04 inches. Since the outer diameter 210 is selected to be the same as the outer diameter 308, the bends 84 stack with adjacent bends 84, just as when bends 306 are stacked with adjacent bends 306. A narrower bend radius for a given thickness 190 can improve the efficiency of heat transfer between the working fluid inside the meandering circuit pipe 70 and the fluid outside the meandering circuit pipe 70. Also, a narrower bend radius for a given wall thickness 190 can reduce the internal fluid pressure drop within the meandering circuit pipe 70 because it increases the inner diameter of the pipe's piping section.

[0076]

[0113] Referring to Figure 11, the step of determining the geometry of the bend 84 first includes setting the meandering circuit pipe 70 to have an initial bend 316 connecting the pipe sections 80, 82. The initial bend 316 has a bend angle of 180° and a centerline radius 317 that is larger than the centerline radius 313 of the bend 306 shown in Figure 10. Referring to Figures 10 and 11, the initial bend 316 has an inner ring 320 with an arc length 318 that is larger than the arc length 314, due to the centerline radius 317 being larger than the centerline radius 313.

[0077]

[0114] With respect to Figure 12, in order for the bend 84 to fit within the same coil envelope as the conventional bend 306 in Figure 10, i.e., so that the distance between the centers of the pipe sections of the pipe is equal, the bend 84 has an outer ring 92 that matches the outer ring 315 of the bend 306, and the pipe 70 has an outer diameter 210 that matches the outer diameter 308. To provide matching outer rings 92, 315, the process of determining the geometry of the bend 84 includes moving the contact points 122, 124 of the pipe sections 70, 82 toward each other in directions 330, 332 (Figure 11) until 1) the bend 84 has an actual centerline radius 232 equal to the centerline radius 313 of the bend 306, and 2) the arc length of the inner ring 90 of the bend 84 is equal to the inner ring 312 of the bend 306.

[0078]

[0115] To compensate for the reduction in the vertical distance between contacts 122 and 124, the material of the meandering circuit tube 70 inside the bend 84 is shaped to have a sinusoidal pattern 110. The sinusoidal pattern 110 has variables that define the shape of the sinusoidal pattern 110, such as the length of the sinusoidal pattern 110, the number of peaks / troughs, the period, and / or amplitude.

[0079]

[0116] Referring here to Figure 13A, the step of determining the geometry of the bend 84 then includes providing a line 339 having an inner ring arc length 340 that matches the arc length 336 of the inner ring 90 in Figure 12. The arc length 336 of the inner ring 90 extends between the transition points 122,124 in Figure 12.

[0080]

[0117] The sinusoidal wave pattern 110 is offset from the contacts 122,124 of the bend 84 by two parts of the meandering circuit tube 70. The first part is relief sections 222,224 corresponding to offset angles such as 7° on both sides of the sinusoidal wave pattern 110, measured between angles 220,240 (see Figure 4). The second part is tapered introduction sections 140,142. The sinusoidal wave pattern 110 starts and ends at point 400 (see Figure 4). To create the offset of the sinusoidal wave pattern 110 from the contacts 122,124, the process of determining the geometry of the bend 84 includes, as shown in Figure 13A, removing lengths 342,344 from length 340 to give a sinusoidal wave pattern length 346 that is shorter than the inner ring arc length 340. Thus, lengths 342,344 each include the following two length sections: 1) a length portion corresponding to one of the relief portions 222, 224, and 2) a length portion corresponding to one of the tapered introduction portions 140, 142. Lengths 342, 344 are determined, for example, by determining the length portion using the inner ring radius and angular offset.

[0081]

[0118] The difference between the length 340 (see Figure 13A) and the arc length 318 (see Figure 11) of line 339 is incorporated into the total arc length 346 of the sinusoidal pattern 110. Referring to Figure 13A, the total arc length 346 of the sinusoidal pattern 110 can be expressed as follows:

[0082]

[0119] Total arc length of the sine wave pattern 346 = Inner arc length 340 -length 342,344 [Equation 1.1]

[0083]

[0120] If the total arc length 346 of the sinusoidal wave pattern 110 is known, the total arc length 346 can be divided by the number of peaks 250A and troughs 252A, for example, 8 to 12 peaks and troughs, or a range of 6 to 18 peaks and troughs, to determine the arc length 350 of each peak 250A and trough 252A. Each peak 250A and trough 252A has a radius 349 and an arc length 350, given by the following equation.

[0084]

[0121] arc length350 =radius 349 ×θ[Equation 1.2]

[0085]

[0122] However, θ is the angular range of the peaks 250A and valleys 252A. The radius of each peak 250A and valley 252A can be determined using the following calculation.

[0086]

[0123] Referring to Figure 13B, a geometric shape 351 is provided having an arc AD and a triangle formed by ABCD. Since triangle ABC is a right triangle, the following equation can be accepted.

[0087]

[0124]

number

[0088]

[0125] This equation can be reconstructed as follows:

[0089]

[0126]

number

[0090]

[0127] The relationship a = r × θ can be substituted into equation 1.4 and obtained as follows:

[0091]

[0128]

number

[0092]

[0129] At this point, the value of "a" can be determined. That is, it is the value obtained by dividing the total arc length of the sine wave pattern 110, 346, by the number of peaks (250) and troughs (252) (Figure 13A). The value of "c" can be determined (see c / 2 in Figure 13B). That is, it is the value obtained by dividing the length 346 by the number of selected peaks (250) and troughs (252).

[0093]

[0130] The above equation can then be solved for theta using numerical methods such as the Newton-Raphson iteration. Once theta is determined, the radii of the peak section 250A and the valley section 252A can be determined by finding the radius 349 in equation 1.2.

[0094]

[0131] The radius 349 and theta allow the amplitude of the sinusoidal pattern 110 to be determined using the following equation.

[0095]

[0132] amplitude 352 =radius 349 -(radius 349 ×cosθ)

[0096]

[0133] It will be understood that adjustments to the sine wave pattern 110 can be made as needed to tailor the sine wave pattern 110 for specific applications.

[0097]

[0134] Regarding Figure 12, the tapered introduction sections 140 and 142 smooth the bending of the material of the meandering circuit tube 70, reducing stress concentration in the transition area between the reliefs 222 and 224 (see Figure 4) and the sinusoidal pattern 110.

[0098]

[0135] Figures 14 to 18 describe in more detail the intersecting sinusoidal wave patterns 110 and arc patterns 150 of the controlled wrinkled portion 94. The intersecting sinusoidal wave patterns 110 and arc patterns 150 provide a three-dimensional profile of the inner bend. The three-dimensional profile of the inner bend provides a corrugated structure with high strength to resist the internal fluid pressure in the meandering circuit tube 70. The intersecting sinusoidal wave patterns 110 and arc patterns 150 cause the bend 84 to experience low stress even when the bend 84 is under high internal pressure.

[0099]

[0136] Referring to Figure 14, one half of the sinusoidal pattern 110 is described. The other half of the sinusoidal pattern 110 is identical in the embodiment of Figure 9A. The sinusoidal pattern 110 begins at point 400 and is separated from the contact point 122 by the relief 222 and the tapered introduction portion 140. The tapered introduction portion 140 gradually slopes upward toward point 400, which is close to the peak 250 of the end ridge 118. The sinusoidal pattern 110 oscillates around a centerline 406 that intersects the sinusoidal pattern 110 at the transition portion 410 between the concave portion 412 and the convex portion 414 (when viewed from the center 230). In the embodiment of Figure 14, the centerline 406 of the sinusoidal pattern 110 is located on the inner ring 90 of the bend portion 84 (see Figure 12). In another embodiment, the valleys 252 of the sinusoidal pattern 110 are on the inner ring 90 of the bent portion 84, and therefore the inner ring 90 is in contact with the groove 116. In yet another embodiment, the peaks 250 of the sinusoidal pattern 110 are on the inner ring 90 of the bent portion 84, and therefore the inner ring 90 is in contact with the ridge 114.

[0100]

[0137] Referring to Figure 14, the center line 406 of the sinusoidal wave pattern 110 has a radius of 416. In one embodiment, the bent portion 84 has a center line radius 232 (see Figure 12) in the range of approximately 1.5 inches to approximately 2 inches, for example, in the range of approximately 1.7 inches to approximately 2 inches, for example, 1.875 inches. The center line 406 may have a radius in the range of approximately 1 inch to approximately 1.5 inches, for example, in the range of approximately 1.3 inches to approximately 1.4 inches, for example, 1.35 inches.

[0101]

[0138] With respect to Figure 15, the arc pattern 150 includes a peak arc 152 that intersects the sinusoidal pattern 110 at each peak 250, and a valley arc 154 that intersects the sinusoidal pattern 110 at each valley 252. The peak arc 152 and the valley arc 154 are separated by an angle 420 around the bend 84, which can be, for example, in the range of approximately 4° to approximately 14°.

[0102]

[0139] With respect to Figure 16A, the crescent arc 152 has its center 182 radially inward from the pipe centerline 102 of the bend 84. The center 182 is positioned along the midline plane 424 of the meandering circuit pipe 70. The crescent arc 152 extends over an angle 160, which can be in the range of 150° to approximately 170°, such as 160°. The crescent arc 152 has an arc length 427 extending from endpoint 426 to endpoint 430.

[0103]

[0140] In Figure 17A, the valley arc 154 has its center 172 radially outward from the centerline 102 of the meandering circuit tube 70. The valley arc 154 extends over an angle 162 that is smaller than the angle 160 in Figure 16A. In one embodiment, the angle 162 is in the range of approximately 100° to approximately 150°, such as 140°. The valley arc 154 has an arc length 432 between its endpoints 434,436, which is shorter than the arc length 427 of the peak arc 152.

[0104]

[0141] With respect to Figure 18, the continuously curving controlled wrinkled surface 134 of the controlled wrinkled portion 94 (as shown in Figure 8) can be formed, at least in part, by connecting the peak arcs 152 and valley arcs 154 with a surface portion 440 having a convex portion 442, a concave portion 444, and a transition portion 446 that moves between the convex portion 442 and the concave portion 444. The surface portion 440 can be mirrored on the opposite side of the ridge 114 across a vertical plane containing the peak arcs 152.

[0105]

[0142] In one embodiment, the continuously curved wrinkled surface 134 is perpendicular to a vertical plane containing a peak arc 152 and a vertical plane containing a valley arc 154. Referring to Figure 15, the vertical plane containing the peak arc 152 is defined as being perpendicular to a horizontal plane 424 (see Figure 8) and includes the origin or center 230 and the vertex 250. The vertical plane containing the valley arc 154 is defined as being perpendicular to the horizontal plane 424 and includes the center 230 and the valley 252. The vertical planes containing the peak arc 152 and the valley arc 154 are separated by an angle 420. Referring to Figure 18, the concave portion 442 and the convex portion 444 connect the peak and valley arcs 152,154, providing a wavy three-dimensional profile of the continuously curved, controlled wrinkled surface 134 (Figure 8). Each concave and convex portion 442,444 is terminated by two quad-pole splines, one of which begins at the endpoint 426 of the peak arc (Figure 16A) and ends at the endpoint 434 of the valley arc (Figure 17A), while the other quad-pole spline begins at the endpoint 430 of the peak arc (Figure 16A) and ends at the endpoint 436 of the valley arc (Figure 17A).

[0106]

[0143] With respect to Figures 19 and 20, a pipe bending machine 500 is provided for bending a segment of the meandering circuit pipe 70 to form the bend 84 described above. The pipe bending machine 500 includes a bending die 502 and a clamping die 504 pivoting about an axis 506. The pipe bending machine 500 includes a pressure die 508 for supporting the outside of the bend 84 and the rear of the meandering circuit pipe 70. The bending die 502 and the clamping die 504 include recesses 512, 514 with surfaces 516, 518 extending around them, which clamp the pipe as it advances over the gap 522 between the bending die 502 and the clamping die 504 in direction 520. The clamping die 504 and the pressure die 508 may be actuated in direction 524 to fix a portion of the pipe between the clamping die 504 and the bending die 502. The pressure die 508 includes a recess to receive a portion of the pipe, and as the pipe moves, it can shift in direction 526, while the bending die 502 and clamp die 504 pivot in direction 528 about axis 506 to support the outside of the pipe during the bending operation.

[0107]

[0144] With reference to Figures 19 and 20, the bending die 502 includes an upper portion 530, a lower portion 532, and a recess 534 that receives a portion of the pipe when the bending die 502 and the clamp die 504 pivot in direction 528. The bending die 502 has a wrinkled portion 536 which is a mirror image of the wrinkled portion 94 of the pipe, thereby the bending die 502 imparts the wrinkled pattern 94 to the pipe. For example, the wrinkled portion 536 includes a ridge 540 that forms a groove 116 (Figure 8) and a groove 542 that forms a ridge 114 (Figure 8).

[0108]

[0145] Referring to Figure 20, each ridge 540 has an intermediate portion 544 and an opposing end portion 546. The intermediate portion 544 may have a first width around the bending die 502, and the end portions 546, 548 have a width greater than the width of the intermediate portion 544 around the bending die 502, such that the ridge 540 widens outward as it extends away from the midline 550 of the bending die 502. The groove 542 may correspondingly have an intermediate portion 552 and opposing end portions 554, 556, the end portions being narrower than the intermediate portion 552 around the bending die 502 due to the increase in the width of the ridge 540 as it extends away from the midline 550. The ridges 540 and grooves 542 have undulating continuous curved surfaces 560 such that the wrinkled portion 536 forms a continuous wrinkled surface 134 of the tube.

[0109]

[0146] Figures 21 to 25 provide a method for forming a bend 84 using a pipe bending machine 500. The pipe bending machine 500 shown in Figures 21 to 25 has components similar to the pipe bending machine 500 shown in Figure 19, but with different component orientations. For the sake of discussion, the pipe bending machines in Figures 20 and 21 to 25 will be described using similar reference numerals.

[0110]

[0147] With respect to Figures 21 and 22, the pipe 564 is advanced into the pipe bending machine 500, and the pressure die 508 supports the outer surface of the pipe 564. In Figure 22, the bending die 502 and the clamping die 504 engage a portion 505 of the pipe 564 and begin to pivot in the direction 565 in the plane of paper of Figure 22.

[0111]

[0148] With respect to Figures 23 and 24, the bending die 502 and the clamping die 504 are rotated in direction 565 to begin forming the bend 570 in the pipe 564. The pressure die 508 continues to support the outside of the pipe 506 and is shifted in direction 526 to move with the pipe 564 during the bending operation.

[0112]

[0149] In Figure 25, the pipe bending machine 500 has formed a bent section 570 by bending the pipe 564 by 180 degrees.

[0113]

[0150] Figure 26 shows that the upper portion 530 of the bending die 502 is shifted upward in direction 569 from the lower portion 532, the clamp die 504 is shifted away from the pipe 564 (into the plane of the paper), and the pressure die 508 is retracted from the pipe 564. The pipe 564 is then shifted in direction 571 to position the next bending position along the pipe 564 within the pipe bending machine 500.

[0114]

[0151] With respect to Figure 27, the bent portion 570 is shown having a wrinkled portion 572 including a ridge 574 and a groove 576 formed on the inside of the bent portion 570. Figure 27 also shows how the lower portion 532 has a sinusoidal pattern 578 at the midline 550 (see Figure 20) of the bending die 502 that imparts a sinusoidal pattern 580 to the inside of the bent portion 570. More specifically, the lower portion 532 has the lower part of a ridge 540 that forms a groove 576 in the bent portion 570, and the lower portion 532 has the lower part of a groove 542 that receives the ridge 574 of the bent portion 570. In this way, the ridge 574 of the tube 564 and the ridge 540 of the bending die 502 form a tightly interlocked configuration. The ridge 540 and groove 542, which have a wavy continuous surface, support the inside of the tube. The upper portion 530 of the bending die 502 (Figure 26) forms a corresponding meshing engagement with the upper part of the bent portion 570.

[0115]

[0152] With respect to Figure 20, the wrinkled portion 536 of the bending die 502, referring to Figure 27, includes a tapered transition portion 590 and an end ridge 592, which work together to form the end ridge 594 of the bent portion 570. The tapered transition portion 590 provides a smooth introduction to the peak of the end ridge 594, as described above with respect to Figure 9A.

[0116]

[0153] Various types of bends may be provided in accordance with this disclosure. For example, Figure 28 shows a 90-degree bend 600, Figure 29 shows an 80-degree bend 620, and Figure 30 shows a 100-degree bend 640.

[0117]

[0154] Figure 31 provides a cross-sectional view of the meandering circuit pipe 700 taken perpendicular to the length of the meandering circuit pipe 700. The meandering circuit pipe 700 is similar to the meandering circuit pipe 70 and includes a piping section 701. The piping section 701 includes a piping section 702 having a circular cross-section and a piping section 704 having a non-circular cross-section such as an elliptical or oblong shape. The piping section 701 has a cross-section that gradually becomes flatter, and the piping section 706 has a width 707 that is wider than the width 709 of the piping section 708.

[0118]

[0155] With respect to Figure 32, a coil 800 is provided, including assembled meandering circuit tubes 802, 804. Each meandering circuit tube 802, 804 includes a piping section 803, 805 and a composite bend 806, which includes a first bend 808 having a first bending angle 810 of 80 degrees, a second bend 812 having a second bending angle 814 of 100 degrees, and a connecting section 816 connecting the first and second bends 808, 812. The first and second bends 808, 812 have an inner controlled wrinkled portion similar to the controlled wrinkled portion of the bend described above. The meandering circuit tubes 802, 804 have three contact points 820, 822, 824. Each meandering circuit tube 802, 804 has a height or distance 830 between the piping sections 803, 805. The meandering circuit tubes 802 of coil 800 are in contact with each other. In other embodiments, the coil may include meandering circuit tubes that are not in contact with each other.

[0119]

[0156] Referring to Figure 33, a portion of the tube 896 including a straight section 898 and a bent section 900 is shown. A bent section 900 is provided that is similar in many respects to the bent section described above. The bent section 900 includes a wrinkled section 902 having a ridge 904 and a groove 906. The wrinkled section 902 includes a sinusoidal pattern 903 along the inner ring of the bent section 900, which begins and ends at points 903A, 903B. The tube 896 has contact points 911, 913 at the transition between the straight section 898 and the bent section 900.

[0120]

[0157] The wrinkled portion 902 is asymmetrical with respect to the plane 908 that bisects the bent portion 900. Axes 915 and 912 extend perpendicular to the plane 908 and intersect contact points 913 and 911, respectively. Contact points 911 and 913 are offset along the plane 908 by a distance of 910, thereby causing the wrinkled portion 902 to extend further along the tube 896 on one side of the plane 908 than on the other side. The portion of the wrinkled portion 902 on one side of the plane 908 (upper part of Figure 33) has an offset portion 910A that includes at least one more ridge 904 and / or at least one more groove 906 than the portion of the wrinkled portion 902 on the other side of the plane 908.

[0121]

[0158] The wrinkled portion 910 has an end groove 906A and an end ridge 904A. In one implementation configuration, the end ridge 904A does not have a tapered introduction portion. The offset portion 910A may provide a transition for flow within the pipe 896 between the nearby straight portion 898 and the bent portion 900. The end ridge 904B also has a tapered introduction portion 914, similar to the various end ridges described above.

[0122]

[0159] With respect to Figures 34 and 35, a bending die 1000 similar to the bending die 502 described above is provided, so as to highlight the differences. The bending die 1000 is used to form a bend 900 and includes an upper part 1002 and a lower part 1004. The upper part 1002 and the lower part 1004 have ridges 1006 and grooves 1008 that cooperate to form ridges 904 and grooves 906 in the bend 900. The upper part 1002 and the lower part 1004 each have a pair of channels 1010, 1012. The channel 1010 of the upper part 1002 and the lower part 1004 forms an opening 1013 on one side 1014 of the bending die 1000, and the channel 1012 of the upper part 1002 and the lower part 1004 forms another opening 1015 on a second side 1016.

[0123]

[0160] The openings 1013 and 1015 allow the bending die 1000 to have a tube supplied to either of the openings 1013 and 1015 of the bending die 1000, and also allow the bending die 100 to rotate in the corresponding direction to form a bend 900 in the tube. Referring to Figure 35, for example, the first portion of the tube may advance into the channel 1012 of the lower part 1004 of the bending die in direction 1030. The upper part 1002 is shifted downward in direction 1032 to engage with the lower part 1004 of the bending die, forming the opening 1015 around the tube.

[0124]

[0161] Next, the bending die 1000 is rotated in direction 1034 about axis 1036, during which the rear portion of the tube is supported by the pressure die. The bending die 1000 rotates in direction 1034 to give the bend 900 a desired angular range. Once the bend 900 is formed, the upper part 1002 of the bending die is shifted upward in direction 1033, and the tube is shifted relative to the bending die 1000 to position another portion of the tube within the bending die 1000 for bending. Continuing this example, the tube is repositioned to advance a second portion of the tube into the opening 1013, the bending die 1000 is closed, and the bending die 1000 is rotated in the opposite direction to direction 1034. The process of advancing and bending the tube is repeated until the desired number of bends are given to the tube.

[0125]

[0162] Figure 36 provides a pipe 1100 having a return bend 1102 and a straight section 1103. The return bend 1102 has a wrinkled section 1104 similar to the wrinkled section described above. The wrinkled section 1104 has valleys 1106 and peaks 1108. The pipe 1100 has a flattened cross section in the valleys 1106, peaks 1108, and / or the straight section 1103. The flattened cross section of the pipe 1100 can allow the pipe 1100 to be packed tightly with adjacent pipes, such as in a coil assembly for a cooling tower. The flattened cross section of the pipe 1100 can also improve the thermal performance of the pipe 1100.

[0126]

[0163] The flattened cross-section of pipe 1100 may be, for example, an elliptical cross-section. In Figure 37A, the return bend 1102 includes a valley elliptical wall portion 1110 in the valley 1106. The valley elliptical wall portion 1110 has a long dimension 1112 and a short dimension 1114.

[0127]

[0164] In Figure 37B, the return bend 1102 has a peak elliptical wall portion 1116 at the peak 1108, and the peak elliptical wall portion 1116 has a long dimension 1120 and a short dimension 1122. The long dimension 1120 of the peak 1108 is larger than the long dimension 1112 of the valley 1106. In one embodiment, the short dimension 1122 of the peak 1108 is smaller than the short dimension 1114 of the valley 1106.

[0128]

[0165] In Figure 37C, the return bend 1102 has an elliptical wall portion 1126 in the straight section 1103, and the elliptical wall portion 1126 has a long dimension 1128 and a short dimension 1130. In one embodiment, the long dimension 1128 of the straight section 1103 is smaller than the long dimensions 1112 and 1120, and the short dimension 1130 is larger than the short dimensions 1114 and 1122.

[0129]

[0166] The flattened cross-sections of each part of the pipe 1100 can be provided by several different approaches. For example, a pipe bending machine used to bend the pipe and impart a wrinkled portion 1104 may flatten the bent portion 1102 during the bending procedure. In another approach, the pipe originally has an elliptical cross-section, and the bending procedure imparts a wrinkled portion 1104 to the bent portion 1102 without further flattening the pipe. In yet another approach, a pipe bending machine is used to form one or more bends in the pipe, and after the bending procedure, a press is used to flatten the pipe.

[0130]

[0167] The use of singular terms such as "a" and "an" is intended to encompass both singular and plural forms unless otherwise indicated herein or explicitly denied by the context. The terms "comprising," "having," "including," and "containing" should be interpreted as open-ended terms. The phrase "at least one of" as used herein is intended to be interpreted disjunctively. For example, the phrase "at least one of A and B" is intended to encompass A, B, or both A and B.

[0131]

[0168] While specific embodiments of the present invention have been illustrated and described, those skilled in the art will understand that numerous changes and modifications are conceivable, and that the present invention is intended to encompass all changes and modifications that fall within the scope of the appended claims. For example, the bends disclosed herein may be used in various heat exchange devices, such as, as some examples, evaporative condensers, air-cooled condensers, closed-circuit fluid coolers, closed-circuit cooling towers, open-circuit cooling towers, dry coolers, ice thermal storage systems, thermal storage coils, and / or ice-water cooling coils.

Claims

1. An indirect heat exchanger pressure vessel comprising: an inlet header for receiving pressurized working fluid; an outlet header for collecting the pressurized working fluid; and a meandering circuit tube connecting the inlet header and the outlet header, enabling the pressurized working fluid to flow from the inlet header to the outlet header, The meandering circuit pipe comprises a piping section and a return bend section connecting the piping section, The aforementioned return bend portion has an inner ring and an outer ring, The return bend portion has a side portion between the inner ring and the outer ring, and a controlled wrinkled portion between the side portions. The controlled wrinkled portion includes alternating ridges and grooves, The controlled wrinkled portion of the return bending portion includes a sinusoidal pattern in the inner ring of the return bending portion. The sinusoidal pattern includes peaks in the ridges of the return bend and valleys in the grooves. Each ridge extends from the inner ring of the return bend toward the side portion of the return bend, Each ridge widens as it extends from the inner ring of the return bend toward the side portion. An indirect heat exchanger pressure vessel in which each ridge has a first width in the inner ring that is narrower than a second width in the side portion.

2. The inlet header, the outlet header, and the meandering circuit tube are configured to operate at an internal pressure of at least 150 psig, indirect heat exchanger pressure vessel according to claim 1.

3. The inlet header, the outlet header, and the meandering circuit tube are configured to operate at an internal pressure of at least 410 psig, indirect heat exchanger pressure vessel according to claim 1.

4. The inlet header, the outlet header, and the meandering circuit tube are configured to operate at an internal pressure of at least 1200 psig, indirect heat exchanger pressure vessel according to claim 1.

5. The meandering circuit pipe includes a pair of contacts at the joint between the return bend portion and the piping portion of the meandering circuit pipe. The aforementioned return bend portion has a bending angle, The controlled wrinkled portion of the return bend is spaced apart from the contact along the meandering circuit tube, The indirect heat exchanger pressure vessel according to claim 1, wherein the controlled wrinkled portion of the return bend has an angular range smaller than the bending angle around the inside of the return bend.

6. The controlled wrinkled portion of the return bend includes an arc pattern that intersects with the sine pattern of the return bend, The indirect heat exchanger pressure vessel according to claim 1, wherein the arc pattern comprises a mountain arc intersecting the mountain and a valley arc intersecting the valley.

7. At least one of the arcs of the mountain has a first radius of curvature, At least one of the valley arcs has a second radius of curvature, The indirect heat exchanger pressure vessel according to claim 6, wherein the first radius of curvature and the second radius of curvature are substantially the same.

8. The ridge includes an end ridge adjacent to the piping portion of the meandering circuit pipe, The indirect heat exchanger pressure vessel according to claim 1, wherein at least one of the end ridges includes a tapered introduction portion for smoothing the flow of the pressurized working fluid around the ridge and the groove.

9. The return bend portion has a bending radius and includes a tubular side wall extending around the interior of the return bend portion. The tubular side wall includes a first semicircular inner wall portion, a first outer wall portion, and a pair of first connecting wall portions on both sides inside the return bend portion that connect the first semicircular inner wall portion and the outer wall portion. The first semicircular inner wall portion, the outer wall portion, and the first connecting wall portion are aligned in the radial direction. The tubular side wall includes a second semicircular inner wall portion in each groove of the return bend, a second outer wall portion, and a pair of connecting wall portions on both sides inside the return bend that connect the second semicircular inner wall portion and the second outer wall portion. The indirect heat exchanger pressure vessel according to claim 1, wherein the second semicircular inner wall portion, the outer wall portion, and the second connecting wall portion are radially aligned.

10. The first semicircular inner wall portion has a first radius of curvature, The indirect heat exchanger pressure vessel according to claim 9, wherein the second semicircular wall portion has a second radius of curvature substantially the same as the first radius of curvature.

11. An indirect heat exchanger pressure vessel comprising: an inlet header for receiving pressurized working fluid; an outlet header for collecting the pressurized working fluid; and a meandering circuit tube connecting the inlet header and the outlet header, thereby enabling the pressurized working fluid to flow from the inlet header to the outlet header, The meandering circuit pipe has a piping section and a return bend section connecting the piping section, The aforementioned return bend portion has a controlled wrinkled portion, The controlled wrinkled portion has alternating ridges and grooves, The return bend portion has a bending radius and a tubular side wall that extends around the inside of the return bend portion. The tubular side wall has a first semicircular inner wall portion at each ridge of the return bend, a first outer wall portion, and a pair of first connecting wall portions on both sides inside the return bend that connect the first semicircular inner wall portion and the outer wall portion. The first semicircular inner wall portion, the outer wall portion, and the first connecting wall portion are aligned in the radial direction. The tubular side wall has a second semicircular inner wall portion in each groove of the return bend, a second outer wall portion, and a pair of connecting wall portions on both sides inside the return bend that connect the second semicircular inner wall portion and the second outer wall portion. The second semicircular inner wall portion, the outer wall portion, and the second connecting wall portion are aligned in the radial direction. The first semicircular inner wall portion has a first angular range, The second semicircular inner wall portion has a second angular range, An indirect heat exchanger pressure vessel in which the first and second angular ranges are each greater than 90 degrees.

12. The indirect heat exchanger pressure vessel according to claim 11, wherein the first angular range is greater than the second angular range.

13. The piping section of the meandering circuit pipe comprises a plurality of pairs of piping sections, The indirect heat exchanger pressure vessel according to claim 1, wherein the return bend portion comprises a plurality of return bend portions connecting the pair of piping portions.

14. An indirect heat exchanger pressure vessel comprising: an inlet header for receiving pressurized working fluid; an outlet header for collecting the pressurized working fluid; and a meandering circuit tube connecting the inlet header and the outlet header, thereby enabling the pressurized working fluid to flow from the inlet header to the outlet header, The meandering circuit pipe has a piping section and a return bend section connecting the piping section, The aforementioned return bend portion has a controlled wrinkled portion, The controlled wrinkled portion has alternating ridges and grooves, The aforementioned return bend portion is A first bent portion including the first controlled wrinkled portion of the controlled wrinkled portion, A second bent portion including a second controlled wrinkled portion of the controlled wrinkled portion, The straight portion of the meandering circuit tube connecting the first bend and the second bend, An indirect heat exchanger pressure vessel having the following features.

15. The first bent portion has a first bending angle of 90 degrees or more. The indirect heat exchanger pressure vessel according to claim 14, wherein the second bent portion has a second bending angle of 90 degrees or less.

16. The aforementioned return bend portion comprises a plurality of return bend portions, The indirect heat exchanger pressure vessel according to claim 1, wherein all of the return bends of the meandering circuit pipe have centerlines that lie on the same plane.

17. The aforementioned return bend portion has a bending angle of 180 degrees. The indirect heat exchanger pressure vessel according to claim 1, wherein the controlled wrinkled portion of the bent part has an arc length of 180 degrees or less.

18. The indirect heat exchanger pressure vessel according to claim 1, wherein the piping portion of the meandering circuit pipe includes a piping portion having a non-circular cross-sectional shape.

19. The indirect heat exchanger pressure vessel according to claim 1, wherein the controlled wrinkle portion includes at least one tapered introduction portion.

20. An indirect heat exchanger pressure vessel comprising: an inlet header for receiving pressurized working fluid; an outlet header for collecting the pressurized working fluid; and a meandering circuit tube connecting the inlet header and the outlet header, thereby enabling the pressurized working fluid to flow from the inlet header to the outlet header, The meandering circuit pipe has a piping section and a return bend section connecting the piping section, The aforementioned return bend portion has a controlled wrinkled portion, The controlled wrinkled portion has alternating ridges and grooves, The aforementioned meandering circuit tube has an outer diameter (OD), The meandering circuit tube has a wall thickness (WT), The aforementioned return bend portion has a centerline radius (CLR), The aforementioned return bend portion is given by the following equation [Math 1] The complexity coefficient of the bend (C) is given by Ｂ An indirect heat exchanger pressure vessel having (wherein the complexity coefficient of the bent portion is 10 or more).

21. The indirect heat exchanger pressure vessel according to claim 20, wherein the complexity coefficient of the bent portion is 20 or less.

22. The meandering circuit tube includes a plurality of meandering circuit tubes, The meandering circuit tubes are in contact with each other, in the indirect heat exchanger pressure vessel according to claim 1.

23. The meandering circuit tube includes a plurality of meandering circuit tubes, The indirect heat exchanger pressure vessel according to claim 1, wherein the return bends of the meandering circuit pipes do not come into contact with each other.

24. The indirect heat exchanger pressure vessel according to claim 1, wherein the return bend of the meandering circuit tube has a non-circular cross-sectional shape.

25. The indirect heat exchanger pressure vessel according to claim 1, wherein the return bend of the meandering circuit tube has an elliptical cross-sectional shape.

26. The indirect heat exchanger pressure vessel according to claim 1, wherein the controlled wrinkled portion is asymmetrical with respect to a plane that bisects the return bend portion.

27. The aforementioned return bend portion has a bending angle of 180 degrees. The indirect heat exchanger pressure vessel according to claim 1, wherein the controlled wrinkled portion is asymmetrical with respect to a plane that bisects the return bend portion.

28. An indirect heat exchanger pressure vessel comprising: an inlet header for receiving pressurized working fluid; an outlet header for collecting the pressurized working fluid; and a meandering circuit pipe including a piping section and a return bend section connecting the piping section, which connects the inlet header and the outlet header to allow the flow of the pressurized working fluid from the inlet header to the outlet header, wherein The return bend portion has an inner portion having a sinusoidal pattern on the inner ring of the return bend portion, The aforementioned sine wave pattern has peaks and troughs, The inner portion of the bent section has an arc pattern that intersects with the sinusoidal pattern, The aforementioned arc pattern has a mountain arc that intersects the mountain and a valley arc that intersects the valley, An indirect heat exchanger pressure vessel in which the arc of the peak has a larger angular range than the angular range of the arc of the valley.

29. The arc of the mountain has a first radius of curvature, The arc of the valley has a second radius of curvature, The indirect heat exchanger pressure vessel of claim 28, wherein the first radius of curvature of the mountain arc and the second radius of curvature of the valley arc are substantially the same.

30. The meandering circuit tube has a center line along the midline plane of the return bend, Each of the arcs of the mountain has its center radially inward from the center line. The indirect heat exchanger pressure vessel of claim 28, wherein each of the valley arcs has its center radially outward from the center line.

31. The aforementioned return bend portion has a central plane, The aforementioned sinusoidal pattern lies within the median plane, The arc of the mountain is perpendicular to the median plane, The indirect heat exchanger pressure vessel of claim 28, wherein the arc of the valley is perpendicular to the median plane.

32. The sinusoidal pattern includes the end peak portion adjacent to the piping section, The indirect heat exchanger pressure vessel of claim 28, wherein at least one of the end peaks includes a tapered introduction segment.

33. An indirect heat exchanger pressure vessel comprising: an inlet header for receiving pressurized working fluid; an outlet header for collecting the pressurized working fluid; and a meandering circuit pipe including a piping section and a return bend section connecting the piping section, which connects the inlet header and the outlet header to enable the flow of the pressurized working fluid from the inlet header to the outlet header, The return bend portion has an inner portion having a sinusoidal pattern on the inner ring of the return bend portion, The aforementioned sine wave pattern has peaks and troughs, The inner portion of the bent section has an arc pattern that intersects with the sinusoidal pattern, The aforementioned arc pattern has a mountain arc that intersects the mountain and a valley arc that intersects the valley, The sinusoidal pattern has a period and amplitude, An indirect heat exchanger pressure vessel in which at least one of the period and the amplitude fluctuates around the return bend.

34. The indirect heat exchanger pressure vessel of claim 33, wherein the sinusoidal pattern includes a first minimum amplitude adjacent to one of the piping sections, a second minimum amplitude adjacent to another of the piping sections, and a maximum amplitude midway between the first and second minimum amplitudes along the inner ring of the bent section.

35. The indirect heat exchanger pressure vessel according to claim 28, wherein the peaks and valleys each have an angular range of at least 100 degrees.

36. The arc of the mountain includes a first radius of curvature and a second radius of curvature, The aforementioned valley arcs include a third radius of curvature and a fourth radius of curvature, The first radius of curvature and the third radius of curvature are substantially the same, The indirect heat exchanger pressure vessel according to claim 28, wherein the second radius of curvature and the fourth radius of curvature are substantially the same.

37. An indirect heat exchanger pressure vessel comprising: an inlet header for receiving pressurized working fluid; an outlet header for collecting the pressurized working fluid; and a meandering circuit pipe including a piping section and a return bend section connecting the piping section, which connects the inlet header and the outlet header to enable the flow of the pressurized working fluid from the inlet header to the outlet header, The return bend portion has an inner portion having a sinusoidal pattern on the inner ring of the return bend portion, The aforementioned sine wave pattern has peaks and troughs, The inner portion of the bent section has an arc pattern that intersects with the sinusoidal pattern, The aforementioned arc pattern has a mountain arc that intersects the mountain and a valley arc that intersects the valley, The arc of the mountain has a shape defined by a part of the first ellipse, An indirect heat exchanger pressure vessel having a valley arc defined by a portion of a second ellipse.

38. The first ellipse has a first long dimension and a first short dimension, The second ellipse has a second major dimension and a second minor dimension, The first length is substantially the same as the second length, The indirect heat exchanger pressure vessel of claim 37, wherein the first short dimension is substantially the same as the second short dimension.

Images