Patent Description:
Heat exchangers (HX) come in a wide variety of configurations and are used in a wide variety of applications. In one approach, referred to as tubular membrane HX, tubes are inserted in tube sheets and sealed to the tube sheet using a number of methods including welding, rolling, braising and gluing (for plastic tubular membrane HX). Another approach involves potting all of the tubes at once with a tube sheet rather than gluing tubes one by one. In yet another approach, tubes together are bundled and compressed mechanically to seal the assembly Document <CIT>, which is considered as the closest prior art, discloses a tubular membrane heat exchanger employing fittings to connect the tubes to the header plate.

Sealing membrane tubes can be a challenge due to the small size and large number of tubes. Further, potting a membrane tube in a tube sheet can be a challenge due to poor adhesion of the potting to the tube. Additionally, with inconsistent and/or flexible tubes, uneven gaps between tubes and tube sheets can create leaks.

Additionally, water flow rates for tubular membrane HX may be limited by sealant issues resulting in lowering the heat and mass transfer properties for the tubular membrane HX. Membrane tube-to-tube sheet seal strength, not tube and tube sheet strength, may be the limiting factor in working pressure of the heat and mass exchangers for these types of applications which in turn limits the versatility and applicability of the tubular membrane HX.

To enable a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:.

According to a first aspect of the present invention, there is provided a tubular membrane heat exchanger comprising: an inlet header including an inlet header body; an outlet header including an outlet header body; a plurality of tubular membranes; a plurality of inlet fittings connecting the tubular membranes to the inlet header body; potting of the inlet header keeping the tubular membranes connected to the inlet fittings; a plurality of outlet fittings connecting the tubular membranes to the outlet header body; and potting of the outlet header keeping the tubular membranes connected to the outlet fittings.

According to a second aspect of the present invention, there is provided a method of manufacturing a heat exchanger, the method comprising: connecting inlet end portions of tubular membranes to inlet fittings associated with an inlet header so that the inlet end portions are adjacent an outer surface of a body of the inlet header; applying first potting to the outer surface of the inlet header body and the inlet end portions of the tubular membranes; connecting outlet end portions of the tubular membranes to outlet fittings associated with an outlet header so that the outlet end portions are adjacent an outer surface of a body of the outlet header; and applying second potting to the outer surface of the outlet header body and the outlet end portions of the tubular membranes.

Regarding <FIG>, a heat exchanger system <NUM> is provided that includes a heat exchanger <NUM> that receives heat, such as heat from inside of a building, and transfers the heat to a fluid such as water or a water/glycol mixture. The fluid may include liquid and gas, the proportions of which may vary as the working fluid travels throughout the heat exchanger system <NUM>. The heat exchanger system <NUM> includes a pump <NUM> configured to pump the fluid from the heat exchanger <NUM> to a heat exchanger <NUM>. The heat exchanger <NUM> includes one or more heat exchanger cassettes, such as tubular membrane heat exchangers <NUM>. The tubular membrane heat exchanger <NUM> are releasably or permanently connected to an inlet manifold <NUM> and an outlet manifold <NUM>. In another approach, the heat exchanger <NUM> may receive heat and transfer the heat to the fluid, while the heat exchanger <NUM> removes heat from the fluid.

Regarding <FIG>, each tubular membrane heat exchanger <NUM> includes an inlet header <NUM> that receives the fluid from the inlet manifold <NUM>, one or more tubular membranes <NUM> through which the fluid travels, and an outlet header <NUM> that collects the fluid from the tubular membranes <NUM>. The tubular membranes <NUM> facilitate heat and/or mass transfer between a first fluid within the tubular membranes <NUM> and a second fluid outside of the tubular membranes <NUM>. As one example, the tubular membranes <NUM> may be made of a gas-permeable material that is also liquid-impermeable. The tubular membranes <NUM> receive fluid including a mixture of liquid and gas that has been heated by the heat exchanger <NUM>. The tubular membranes <NUM> permit the gas, such as vapor, that has been heated by the heat exchanger <NUM> to travel out of the tubular membranes <NUM>. As an example, the fluid entering the tubular membranes <NUM> may be a mixture of water and water vapor. In another approach, the fluid may be completely gas upon reaching the tubular membranes <NUM> and may exit the outlet header <NUM> as a liquid or a gas/liquid mixture.

The tubular membranes <NUM> may be made of, for example, one or more polymers such as polypropylene (PP), polydimethylsiloxane (PDMS) or polytetrafluoroethylene (PTFE). The tubular membranes <NUM> may be porous and include openings in the nanometer diameter range to facilitate heat and/or mass transfer. The tubular membranes <NUM> may be flexible and relatively flimsy which makes gripping the tubular membranes <NUM> difficult to secure to another component. For example, the tubular membranes <NUM> may be stiff enough to be placed vertically on a surface and retain their shape, but any external pressure makes the tubular membranes <NUM> bend and/or twist.

Regarding <FIG>, the heat exchanger system <NUM> includes a fan assembly <NUM> having one or more fans <NUM> and one or more motors <NUM>. The fan assembly <NUM> is configured to generate airflow relative to the tubular membranes <NUM>, such as in direction <NUM> along the lengths of the tubular membranes <NUM>, and/or in directions transverse to the lengths of the tubular membranes <NUM>. The airflow may assist in removing the gas from outer surfaces <NUM> (see <FIG>) of the tubular membranes <NUM>. The fluid may be water, as mentioned above, and pure water vapor may permeate through the tubular membranes <NUM> while contaminants such as debris, scale, and organisms remain inside of the tubular membranes <NUM>. Further, the tubular membranes <NUM> inhibit exterior contaminants from entering the tubular membranes <NUM>.

Regarding <FIG> and <FIG>, the outlet header <NUM> of each tubular membrane assembly <NUM> directs the fluid to the outlet manifold <NUM>. The heat exchanger system <NUM> includes a pump <NUM> configured to pump the fluid from the outlet manifold <NUM> to the heat exchanger <NUM> and throughout the heat exchanger system <NUM>. The pump <NUM> may generate a gauge pressure of the fluid at the inlet header <NUM> in the range of approximately zero pounds per square inch (psi) to approximately <NUM> psi such as <NUM> psi or higher, <NUM> psi or higher, or <NUM> psi or higher, <NUM> psi or higher, <NUM> psi or higher, or <NUM> psi or higher. The heat exchanger system <NUM> may further include a fluid supply <NUM> that adds fluid, such as liquid, gas, or a liquid/gas mixture, to the system <NUM> to compensate for the gas permeating out of the tubular membranes <NUM>.

Regarding <FIG>, the tubular membranes <NUM> may each include an internal passageway, such as a lumen <NUM>, and a side wall <NUM> extending thereabout. The lumen <NUM> may have an inner diameter in the range of approximately <NUM> inches to approximately <NUM> inches, such as <NUM> inches or <NUM> inches. The side wall <NUM> may have a thickness in the range of <NUM> micron to approximately <NUM> microns, such as approximately <NUM> micron to approximately <NUM> microns, such as approximately <NUM> microns to approximately <NUM> microns, such as approximately <NUM> microns to approximately <NUM> microns, such as approximately <NUM> microns to approximately <NUM> microns, such as approximately <NUM> microns, such as approximately <NUM> microns to approximately <NUM> microns, such as approximately <NUM> microns to approximately <NUM> microns. As further examples, the tubular membranes <NUM> may have an inner diameter less than <NUM> millimeters (mm), approximately <NUM>, or greater than <NUM>.

The tubular membranes <NUM> may be flexible and the tubular membrane heat exchanger <NUM> may include a support for each of the tubular membranes <NUM> that resists lateral movement, bending and ballooning of the tubular membrane <NUM>. The support may extend a majority of, such as greater than <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>% or substantially the entire length of the tubular membrane <NUM>. In one embodiment, the support may include a braided sleeve surrounding the tubular membrane <NUM> and extending substantially the entire length of the tubular membrane <NUM>. The braided sleeve may be made of a woven plastic or metal material that inhibits bending of the tubular membrane <NUM>. An example braided sleeve <NUM> is discussed below with respect to <FIG>. Other embodiments of the supports may include rods or other elongate guides. Yet other embodiments of the supports may include coils about the tubular membranes <NUM>.

Regarding <FIG>, the inlet header <NUM> has a header body <NUM> including a plate portion <NUM> with openings <NUM>. The fluid in the heat exchanger system <NUM> may travel through the openings <NUM> in the plate portion <NUM> of the inlet header <NUM> generally in direction <NUM> and into the lumen <NUM> of the tubular membrane <NUM>. The side wall <NUM> of the tubular membrane <NUM> permits gas of the fluid, such as water vapor in a fluid including water vapor and water, to permeate outward through the side wall <NUM> roughly in direction <NUM> and into contact with the air flow generated by the fan assembly <NUM>. The liquid of the flow, such as the water, travels through the lumen <NUM> of the tubular membrane <NUM> and into the outlet header <NUM> via openings <NUM> in a plate portion <NUM> of the outlet header <NUM>.

Regarding <FIG>, the tubular membrane heat exchanger <NUM> have a modular configuration that permits the tubular membrane heat exchanger <NUM> to be individually connected to and removed from the heat exchanger system <NUM>. The module nature of the tubular membrane heat exchanger <NUM> also permits the capacity of the direct heat exchanger <NUM> to be adjusted by adding or removing tubular membrane heat exchangers <NUM> and making associated changes to the volume of fluid in the system <NUM>, capacity of the heat exchanger <NUM>, and/or flow rate of the pump <NUM> as appropriate.

The tubular membrane heat exchanger <NUM> may include a frame <NUM> supporting the inlet and outlet headers <NUM>, <NUM>, the tubular membranes <NUM>, and the spacers <NUM>. The frame <NUM> has an opening <NUM> that permits air flow along and between the tubular membranes <NUM> to facilitate dissipation of the heated gas that has permeated through the side walls <NUM> of the tubular membranes <NUM>. Regarding <FIG>, the spacers <NUM> include openings <NUM> that receive the tubular membranes <NUM>. The spacers <NUM> resist lateral shifting and bending of the tubular membranes <NUM> upon the tubular membranes <NUM> receiving pressurized fluid. The spacers <NUM> may also keep the tubular membranes <NUM> in a generally straight, parallel orientation while the tubular membranes are potted, as discussed below, which facilitates production of a gap-free connection between the potting material and the tubular membranes <NUM>. The number and thickness of the spacers <NUM> may be selected so that the spacers <NUM> operate as supports in lieu of the sleeves <NUM>.

Regarding <FIG>, the tubular membrane <NUM> has an end portion <NUM> that is connected to the plate portion <NUM> of the inlet header <NUM> via a connector, such as a fitting <NUM>. The tubular membrane <NUM> is connected to the plate portion <NUM> of the outlet header <NUM> via a similar fitting <NUM>. The fitting <NUM> has a nipple portion <NUM>, a base portion <NUM>, and a through opening that permits fluid flow through the fitting.

To assemble the tubular membrane <NUM> with the header plate portion <NUM>, the nipple portion <NUM> is advanced in direction <NUM> into the lumen <NUM> of the tubular membrane <NUM>. The assembled tubular membrane <NUM> and fitting <NUM> are shifted in direction <NUM> to seat the base portion <NUM> of the fitting <NUM> in the opening <NUM> of the plate portion <NUM>. A retainer, such as a rubber band <NUM>, may be secured to the end portion <NUM> of the tubular membrane <NUM> to keep the end portion <NUM> secured to the nipple portion <NUM> of the fitting <NUM>. For example, the rubber band <NUM> may be shifted in direction <NUM> along the tubular membrane <NUM> until reaching the end portion <NUM>. The rubber band <NUM> applies a compressive force on the tubular membrane <NUM> that holds the tubular membrane <NUM> tightly against the nipple portion <NUM> of the fitting <NUM>. In another embodiment, the retainer may include a zip tie or a spring-biased mechanical clamp as some examples. Other examples of the retainer may include a gasket, an expanding-foam material, glue, or a combination thereof.

Regarding <FIG>, the tubular membrane <NUM>, fitting <NUM>, and rubber band <NUM> have been assembled to the plate portion <NUM>. The inlet header <NUM> includes potting <NUM> that has been applied to a surface <NUM> of the header plate portion <NUM>. The potting <NUM> may include an epoxy potting or an ultraviolet-curable silicone potting as some examples. The potting <NUM> embeds the end portion <NUM> of the tubular membrane <NUM> and the rubber band <NUM> within the potting <NUM> and forms a mechanical bond between the components. In some embodiments, the potting <NUM> forms a chemical bond with the tubular membrane <NUM> to further resist movement of the tubular membrane <NUM> relative to the potting <NUM>.

The nipple portion <NUM> forms an interference fit with an inner surface <NUM> of the side wall <NUM> of the tubular membrane <NUM> to form a fluid-tight seal. The fitting <NUM> has a central axis <NUM> and may have a varying width taken transverse to the longitudinal axis <NUM> to facilitate sealing of the tubular membrane <NUM> and mechanical locking of the fitting <NUM> to the plate portion <NUM>. In one example, the nipple portion <NUM> has a frustoconical outer surface <NUM> sized to permit the nipple portion <NUM> to be advanced at least partially into the lumen <NUM> of the tubular membrane <NUM> and form a fluid tight seal with the inner surface <NUM> of the side wall <NUM> of the tubular membrane <NUM>. The fitting base portion <NUM> has a frustoconical surface <NUM> that mates with a corresponding frustoconical surface <NUM> of the opening <NUM> of the plate portion <NUM>. The surfaces <NUM>, <NUM> form a friction fit that inhibits the potting material <NUM> from seeping between the plate portion <NUM> and the fitting <NUM> before the potting <NUM> has cured. The mating engagement between surfaces <NUM>, <NUM> also inhibits pull-though of the fitting <NUM> upon pressurization of the fluid in the system <NUM>.

The potting <NUM> maintains the seal between the tubular membrane <NUM> and the fitting <NUM>. As one example, the potting <NUM> may chemically bond with the material of the tubular membrane <NUM> and, once cured, inhibits movement of the tubular membrane <NUM>. The potting <NUM> may also chemically bond with the bodies <NUM> of the inlet and outlet headers <NUM>, <NUM> such as in embodiments wherein the bodies <NUM> are made of a polymer. In another embodiment, the potting <NUM> may not chemically bond with the tubular membrane <NUM> but the presence of the cured potting inhibits movement and/or expansion of the portion of the tubular membrane <NUM> engaged with the nipple portion <NUM> of the fitting <NUM>. By maintaining the seal between the tubular membrane <NUM> and the fitting <NUM>, the potting <NUM> keeps fluid from seeping between an end <NUM> of the tubular membrane <NUM> and the nipple portion <NUM> and expanding the end <NUM> due to contact with the fluid. In some embodiments, the material of the tubular membrane <NUM> expands when contacted by the fluid such that the contact of the potting <NUM> against the tubular membrane <NUM> keeps the tubular membrane <NUM> sealed to the nipple portion <NUM> upstream of the end <NUM> so the end <NUM> stays free of fluid and secured to the fitting <NUM>. The potting <NUM> thereby keeps fluid within the lumen <NUM> of the tubular membrane <NUM> and away from the end <NUM> of the tubular membrane <NUM>.

Regarding <FIG>, in some embodiments, the tubular membrane heat exchanger assembly <NUM> may be provided without the spacers <NUM>. In this form, the tubular membranes <NUM> extend from the inlet header <NUM> to the outlet header <NUM> without the spacers <NUM>.

Regarding <FIG>, the inlet header <NUM> is shown without the tubular membranes <NUM> attached. Although the following discussion refers to the inlet header <NUM>, the outlet header <NUM> may have a similar construction. The inlet header <NUM> includes a curb <NUM> upstanding from the periphery of the plate portion <NUM>. The curb <NUM> and plate portion <NUM> form a recess <NUM> for receiving liquid potting material and keeping the liquid potting material in contact with the tubular membranes <NUM> until the potting material has cured and solidified.

Regarding <FIG>, a tubular membrane <NUM> is shown advanced into one of the openings <NUM> of the plate portion <NUM>. The inlet header <NUM> includes one or more side wall portions <NUM> that extend in an opposite direction from the curb <NUM> and form an interior compartment of the inlet header <NUM>. The interior compartment <NUM> may be a volume that receives the fluid which the inlet header <NUM> then directs into the tubular membranes <NUM>.

In some embodiments, the headers <NUM>, <NUM> and fittings <NUM> are made of the same or different metallic and/or polymer-based materials. The tubular membrane heat exchanger <NUM> may have one or more components made by additive or subtractive manufacturing approaches, such as 3D printing or milling. As further examples, one or more components of the tubular membrane heat exchanger <NUM> may be molded.

Regarding <FIG>, a portion of another tubular membrane heat exchanger <NUM> is provided that includes tubular membranes <NUM> and a header <NUM>. <FIG> shows the portion of the tubular membrane heat exchanger <NUM> before the potting material is applied to a plate portion <NUM> of the header <NUM>.

The tubular membrane heat exchanger <NUM> includes sleeves <NUM> on the outside of and supporting the tubular membranes <NUM>. The sleeves <NUM> may have a woven structure with openings that permit airflow through sleeves <NUM>. In one example, the sleeves <NUM> include a metallic mesh that resists deformation of the tubular membranes <NUM> while having openings that permit airflow into contact with the tubular membranes <NUM> and removal of the permeated gas near the exterior of the tubular membranes <NUM>.

The tubular membrane heat exchanger <NUM> includes rubber bands <NUM> securing the sleeves <NUM> and tubular membranes <NUM> therein to fittings that connect the tubular membranes <NUM> to the header <NUM>. In one embodiment, the fittings resemble the fittings <NUM> discussed above. The header <NUM> includes a curb <NUM> extending around a periphery of the plate portion <NUM> of the header <NUM>. The header <NUM> further includes a barrier wall <NUM> that separates a recess <NUM> of the header <NUM> into two halves. The barrier wall <NUM> permits one half of the recess <NUM> at a time to be filled with potting material. This may make manufacturing easier because the recess <NUM> to be filled with potting material with a sequence of pours of potting material.

Regarding <FIG>, a tubular membrane <NUM> is provided that connects to a header plate portion <NUM> via a fitting <NUM>. In some embodiments, a sleeve may be provided around the tubular membrane <NUM> to support the tubular membrane <NUM> as discussed above with respect to <FIG>. The fitting <NUM> has an end portion <NUM> that is sized to tightly fit into an end portion <NUM> of the tubular membrane <NUM>. In one embodiment, the fitting <NUM> is a tube having an annular side wall <NUM> and a cylindrical outer surface <NUM> that engages a surface <NUM> of the opening <NUM>. The cylindrical outer surface <NUM> has an outer diameter and the surface <NUM> has an inner diameter that are sized to form a tight fit between the fitting <NUM> and the plate portion <NUM> which inhibits liquid potting from seeping between the fitting <NUM> and the plate portion <NUM> when the potting is poured onto the plate portion <NUM>. Further, the outer diameter of outer surface <NUM> may be within ± <NUM>% of an inner diameter of the tubular membrane <NUM>. The tubular membrane <NUM> and fitting <NUM> may be configured to form a fluid-tight seal therebetween and the potting <NUM> reinforces the fluid-tight seal to resist pressurized fluid. In other embodiments, the tubular membrane <NUM> and fitting <NUM> may form a fluid-tight seal therebetween after the potting <NUM> has cured.

With reference to <FIG> and <FIG>, the tubular membrane <NUM> is connected to the header plate portion <NUM> by advancing the end portion <NUM> of the fitting <NUM> into a lumen <NUM> of the tubular membrane <NUM>. The fitting <NUM> may engage the tubular membrane <NUM> and form a fluid-tight connection therebetween. The connecting may further include advancing an opposite end portion <NUM> of the fitting <NUM> into an opening <NUM> of the header plate portion <NUM>. The end portion <NUM> of the fitting <NUM> is advanced so that the end portion <NUM> protrudes outward from a surface <NUM> of the header plate portion <NUM>. The tubular membrane <NUM> has an end <NUM> that is positioned against or near an opposite surface <NUM> of the header plate portion <NUM>.

To maintain the seal between the tubular membrane <NUM> and fitting <NUM> upon the tubular membrane <NUM> receiving pressurized fluid, potting <NUM> is applied to the surface <NUM> of the header plate portion <NUM> and into contact with the tubular membrane <NUM>. Potting <NUM> is also applied to the surface <NUM> of the header plate portion <NUM>. The potting <NUM> connects to the end portion <NUM> of the fitting <NUM> to resist pull-through of the fitting <NUM> in direction <NUM>. The potting <NUM>, <NUM> may be made of the same or different potting materials. The potting <NUM>, <NUM> may each have a depth in the range of <NUM> inches to <NUM> inch, such as approximately <NUM> inches or less. In one embodiment, the fitting <NUM> includes a thin-walled stainless steel tube.

Regarding <FIG>, a header <NUM> may be provided that includes a header body <NUM> including a fitting <NUM> and a header plate portion <NUM>. The header body <NUM> has a unitary, one-piece construction and may be made of metallic or polymer materials. The fitting <NUM> may include a side wall <NUM> having a circular cross-section such that the side wall <NUM> has a cylindrical outer surface <NUM>.

A tubular membrane <NUM> connects to the fitting <NUM> in a manner similar to the tubular membrane <NUM> being connected to the fitting <NUM> discussed above. The header <NUM> includes potting <NUM> that secures an end portion <NUM> of the tubular membrane <NUM> to the fitting <NUM>. In one embodiment, the tubular membrane <NUM> has an end <NUM> that is contacting or near a surface <NUM> of the header plate portion <NUM>. The fitting <NUM> has an opening <NUM> in communication with a lumen <NUM> of the tubular membrane <NUM> to permit fluid to travel between the tubular membrane <NUM> and the header <NUM>.

The tubular membranes and fittings discussed above may have a circular cross-section in some embodiments. In other embodiments, the tubular membranes and fittings may have a variety of cross-sectional shapes including, but not limited to, obround, elliptical, teardrop, triangular, square, rectangular, or a combination thereof.

Uses of singular terms such as "a," "an," are intended to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" are to be construed as openended terms. It is intended that the phrase "at least one of" as used herein be interpreted in the disjunctive sense. For example, the phrase "at least one of A and B" is intended to encompass A, B, or both A and B.

Claim 1:
A tubular membrane heat exchanger (<NUM>) comprising:
an inlet header (<NUM>) including an inlet header body (<NUM>);
an outlet header (<NUM>) including an outlet header body;
a plurality of tubular membranes (<NUM>);
characterised in that the tubular membrane heat exchanger (<NUM>) further comprises
a plurality of inlet fittings (<NUM>) connecting the tubular membranes (<NUM>) to the inlet header body (<NUM>);
potting (<NUM>) of the inlet header (<NUM>) keeping the tubular membranes (<NUM>) connected to the inlet fittings (<NUM>);
a plurality of outlet fittings (<NUM>) connecting the tubular membranes (<NUM>) to the outlet header body; and
potting (<NUM>) of the outlet header (<NUM>) keeping the tubular membranes (<NUM>) connected to the outlet fittings (<NUM>).