Patent Description:
Documents <CIT>, <CIT>, <CIT> and <CIT> disclose a flow-through heater assembly. The statements in this section merely provide background information related to the present invention and may not constitute prior art.

Referring to <FIG>, a typical flow-through heater assembly <NUM> includes a tubular flow body <NUM>, an external heater <NUM> installed onto the outside of the tubular flow body <NUM>, and a baffle <NUM> located within a flow path "F" within the tubular flow body <NUM>. Heat is transferred from the external heater <NUM> through the tubular flow body <NUM> and into a fluid <NUM> flowing therein. The baffle <NUM> is designed to increase the turbulence of the fluid <NUM> and thus increase the heat transfer efficiency between an inner surface of the tubular flow body <NUM> and the fluid <NUM>.

With this conventional design, the external heater <NUM> provides advantages in terms of electrical integration, chemical compatibility, and cleanliness of a given application, such as by way of example semiconductor processing environments (e.g., forelines and exhaust lines). However, these existing flow-through heater assemblies are difficult to maintain when, for example, the internal baffle <NUM> or interior of the tubular flow body <NUM> needs to be cleaned or serviced. Additionally, thermal transfer from the external heater <NUM>, through the wall of the tubular flow body <NUM>, and ultimately into the fluid <NUM> is relatively inefficient.

These issues related to flow-through heaters are addressed by the present invention.

This section provides a general summary of the invention and is not a comprehensive disclosure of its full scope or all of its features.

In one form of the present invention, a flow-through heater assembly comprises a housing having an inlet, an outlet, and a bore extending between the inlet and the outlet. A heater is disposed within the housing and extends between the inlet and the outlet, the heater comprising at least one opening proximate the inlet and at least one opening proximate the outlet, the heater further defining an anfractuous path from the inlet to the outlet. The openings in the heater are in fluid communication with the bore of the housing.

In variations of this flow-through heater assembly, which may be implemented individually or in any combination: the housing comprises two pieces; the two pieces comprise an upper body half and a lower body half, each of the upper body half and the lower body half comprising adjacent perimeter edges following the anfractuous path; each of the adjacent perimeter edges comprise a circuitous groove and the flow-through heater further comprises an upper o-ring disposed within the circuitous groove of the upper body half and a lower o-ring disposed within the circuitous groove of the lower body half; the heater is disposed against the upper o-ring and the lower o-ring; the upper body half and the lower body half are secured together with mechanical fasteners; the mechanical fasteners extend through the heater; each of the upper body half and the lower body half comprise one of the inlet and the outlet; the upper body half and the lower body half are identical in shape; the heater further comprises integral termination pads; the integral termination pads extend laterally from a mid-section of the heater and through a sidewall of the housing; the housing comprises internal grooves configured to receive the heater, the internal grooves following the anfractuous path of the heater; the anfractuous path defines a sine-wave shape; a plurality of heaters extend between the inlet and the outlet; the heater comprises a variable watt density; the heater comprises a material having a sufficient TCR such that the heater functions as a heater and a temperature sensor; at least one temperature sensor is disposed within the housing; the temperature sensor comprises a ribbon extending along a surface of the heater with a junction disposed at a predetermined location; the heater is selected from the group consisting of a polyimide heater, a layered heater, a heat trace heater, a tubular heater, a cartridge heater, and a cable heater; and the flow-through heater assembly is formed by an additive manufacturing process.

In another form of the present invention, a flow-through heater assembly comprises a two-piece housing comprising an inlet, an outlet, and a bore extending between the inlet and the outlet. A heater is disposed within the two-piece housing and extending between the inlet and the outlet, the heater comprising at least one opening proximate the inlet and at least one opening proximate the outlet, the heater further defining an anfractuous path from the inlet to the outlet, wherein the openings in the heater are in fluid communication with the bore of the housing.

In yet another form of the present invention, a flow-through heater assembly comprises a two-piece housing comprising an inlet, an outlet, and a bore extending between the inlet and the outlet, the two-piece housing defining an upper body half and a lower body half, each of the upper body half and the lower body half comprising adjacent perimeter edges having a circuitous groove. An upper o-ring is disposed within the circuitous groove of the upper body half, a lower o-ring is disposed within the circuitous groove of the lower body half, and a heater is disposed within the two-piece housing and extends between the inlet and the outlet against each of the upper o-ring and the lower o-ring. The heater comprises at least one opening proximate the inlet and at least one opening proximate the outlet, the heater further defining an anfractuous path from the inlet to the outlet. The openings in the heater are in fluid communication with the bore of the housing, and the adjacent perimeter edges of the upper body half and the lower body half follow the anfractuous path of the heater.

In still another form, a flow-through heater assembly comprises a housing having an inlet, an outlet, and a bore extending between the inlet and the outlet. A heater is disposed within the housing and extends between the inlet and the outlet, the heater comprising distal end portions disposed across each of the inlet and the outlet. The heater further defines an anfractuous path from the inlet to the outlet.

It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present invention.

In order that the invention may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:.

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present invention in any way.

The following description is merely exemplary in nature and is not intended to limit the present invention, application, or uses.

Referring to <FIG>, a flow-through heater assembly according to the present invention is illustrated and generally indicated by reference numeral <NUM>. The flow-through heater assembly <NUM> includes a housing <NUM> having an inlet <NUM>, an outlet <NUM>, and a bore <NUM> extending between the inlet <NUM> and the outlet <NUM>. The flow-through heater assembly further includes a heater <NUM> disposed within the housing <NUM> and extending between the inlet <NUM> and the outlet <NUM>.

As best shown in <FIG>, the heater <NUM> comprises at least one opening <NUM> proximate the inlet <NUM> and at least one opening <NUM> proximate the outlet <NUM>. As described in greater detail below, the heater <NUM> defines an anfractuous path from the inlet <NUM> to the outlet <NUM>, and the openings <NUM> and <NUM> are in fluid communication with the bore <NUM> of the housing <NUM>. In operation, fluid generally flows into the inlet <NUM> and opening <NUM>, through the bore <NUM> and along the heater <NUM>, and out through the other opening <NUM> and outlet <NUM>, as indicated by the fluid flow "F" (<FIG>).

In one alternative form not specifically shown, such as one with a different number of sinuations along the anfractuous path, a first portion of the fluid flow F does not flow through the opening <NUM> and remains on the one side of the heater <NUM> before exiting the housing <NUM> via the outlet <NUM> while the remainder of the fluid flow F may flow through the opening <NUM> and remain on the opposite side of the heater <NUM> before flowing through another opening (i.e., similar to opening <NUM>) proximate the outlet <NUM> to rejoin the first portion of the fluid flow F to exit through the outlet <NUM>. Alternately, the ends of the heater <NUM> may be disposed across each of the inlet <NUM> and the outlet <NUM> and split the fluid flow F without having openings <NUM>/<NUM>. These and other variations of the flow-through heater assembly <NUM> should be construed as falling within the scope of the present invention.

In one form as shown, the housing <NUM> includes two pieces, an upper body half <NUM> and a lower body half <NUM>. Each of the upper body half <NUM> and the lower body half <NUM> includes an opening that forms either the inlet <NUM> or the outlet <NUM>. Advantageously, in one form, the upper body half <NUM> and the lower body half <NUM> define the same geometry such that only one unique part number is used for the housing <NUM> assembly. It should be understood, however, that the housing <NUM> may be provided as a unitized component (set forth in greater detail below) or in multiple pieces that are not necessarily identical halves while remaining within the scope of the present invention. Additionally, while the exterior profile of the housing <NUM> is illustrated herein as square, other geometries such as rectangular or circular, among others and combinations thereof, are to be understood as being within the teachings of the present invention.

As shown, the heater <NUM> defines an anfractuous path from the inlet <NUM> to the outlet <NUM>. As used herein, the term "anfractuous path" should be construed to mean a curved (but not straight) path that twists and/or turns in multiple directions, such as by way of example an S-shaped or sine-wave shaped path, along which fluid is forced to flow from the inlet <NUM> to the outlet <NUM>. Thus, with its anfractuous path, the heater <NUM> is configured to function as a baffle, taking on multiple directions in 3D space. This innovative anfractuous path of the heater <NUM> increases turbulence of the fluid flow F through the flow-through heater assembly <NUM>, thereby improving heat transfer from the heater <NUM> to the fluid F. Thus, a desired fluid temperature of the flowing fluid F is reached more readily with less power provided to the heater <NUM> than an external heater <NUM> disposed outside the tubular flow body <NUM> (<FIG>). It should also be understood that the anfractuous path may be over a portion of the length of the heater <NUM> and does not have to necessarily extend all the way from the inlet to the outlet while remaining within the scope of the present invention. Further, the anfractuous path may be over a portion of the length of the heater <NUM>, or be arranged in zones along the length of the heater <NUM>, while remaining within the scope of the teachings herein.

Referring also to <FIG>, the upper and lower body halves <NUM>, <NUM> are similarly shaped with an anfractuous interior profile as shown to accommodate assembly with the heater <NUM>. Each of the upper body half <NUM> and the lower body half <NUM> include adjacent perimeter surfaces <NUM>/<NUM> following the anfractuous path. More specifically, in this form, both the upper body half <NUM> and the lower body half <NUM> include the adjacent perimeter surfaces <NUM>/<NUM> having a circuitous groove <NUM> (<FIG>) extending around an interior perimeter as shown. The circuitous grooves <NUM> are arranged to receive a seal, such as an o-ring <NUM>, to seal an interface between the upper and lower body halves <NUM>/<NUM> and the heater <NUM>. Thus, the heater <NUM> is disposed against the upper and lower o-rings <NUM> in this form of the present invention.

In one form, the upper body half <NUM> is secured to the lower body half <NUM> by mechanical fasteners <NUM> (<FIG>), such by way of example, screws, bolts, and/or dowels, among others, that extend through holes <NUM> in the upper and lower body halves <NUM>, <NUM>. Tightening the upper and lower body halves <NUM>, <NUM> together with the mechanical fasteners <NUM> thus compresses the o-rings <NUM> to seal the interface between the heater <NUM> and the upper and lower body halves <NUM>/<NUM> from fluid flow within the housing <NUM>. It should be understood, however, that the upper and lower body halves <NUM>/<NUM> may be secured to each other using other means, such as by way of example, adhesives, welding or mechanical latches, among others, and may include other features such as hinges for ease of maintenance while remaining within the scope of the present invention. Further, in this form, the mechanical fasteners <NUM> also extend through the heater <NUM> as shown. Accordingly, the heater <NUM> includes a plurality of peripheral openings <NUM> configured to receive the mechanical fasteners <NUM>. It should be understood, however, that these peripheral openings <NUM> are optional and the heater <NUM> may be secured between the upper and lower body halves <NUM>/<NUM> by other means.

As further shown, the heater <NUM> includes integral termination pads <NUM> extending laterally from a mid-section <NUM> of the heater <NUM>. The termination pads <NUM> are configured to receive power leads (shown below) to supply power to the heater <NUM>. In this form, the termination pads <NUM> extend through a sidewall <NUM> of the housing <NUM> where the upper body half <NUM> meets the lower body half <NUM>. The termination pads <NUM> in this form are integral with the mid-section <NUM> of the heater <NUM>. However, it should be understood that the termination pads <NUM> may be a separate component rather than integral, and/or may exit the housing <NUM> at a different location besides the mid-section <NUM> of the heater <NUM> while remaining within the scope of the present invention.

Referring to <FIG>, one form of the heater <NUM> and integral termination pads <NUM> are illustrated in greater detail. In this form, the heater <NUM> comprises a resistive heating element <NUM> encapsulated in a polyimide material <NUM>. Power leads <NUM> and <NUM> are connected to the termination pads <NUM>, for example by way of soldering. The entire heater <NUM> in this form is thus flexible, thus allowing it to conform to the shapes of the upper and lower body halves <NUM>/<NUM> during assembly. However, the heater <NUM> may instead be preformed into the anfractuous shape while remaining within the scope of the present invention.

The heater <NUM> may be any of a variety of heaters to provide the requisite power to reach a specified fluid temperature. For example, the heater <NUM> may be a polyimide heater as illustrated and described herein, a layered heater (thick film, thin film, thermal spray, sol-gel), a heat trace, a tubular heater, a cartridge heater, or a cable heater, among others. Further, the heater <NUM> may comprise a plurality of individual heaters arranged in zones (not shown) rather than a single heating element as shown. An example of such a heater system with a plurality of individual heaters is illustrated and described in <CIT>, and its related family of patents and applications, which are commonly owned with the present application and are incorporated herein by reference in their entirety.

In another form, the heater <NUM> has a variable watt density. In this context, a "watt density" is an amount of wattage of power output by the heater <NUM> per unit area, and a "variable watt density" means that the watt density of at least one portion of the heater <NUM> differs from the watt density of another portion of the heater <NUM>. Such a variable watt density is illustrated and described in <CIT> and its related family of patents and applications, which are commonly owned with the present application and are incorporated herein by reference in their entirety. By way of example, in one form, the watt density of a center portion of the heater <NUM> is greater than the watt density of an edge portion of the heater <NUM>, increasing heat generated by the center portion relative to the edge portion. The variable watt density of the heater <NUM> can also be configured to cause thermal gradients in the fluid flow F between the portions of the heater <NUM> with higher watt densities and lower watt densities, further increasing turbulence of the fluid flow F and thus moving colder fluid toward the portions of the heater <NUM> with higher watt densities.

In another form, the heater <NUM> is made of a material having a thermal coefficient of resistance (TCR) sufficient such that the heater <NUM> functions to heat the fluid and as a temperature sensor to detect the fluid temperature. By measuring the change in electrical resistance of the heater <NUM>, the temperature of the fluid is determined based on the TCR. Thus, sensing the change in electrical resistance of the heater <NUM> acts as a correlative measure of the fluid temperature, and the heater <NUM> thus serves a dual function and also acts as a temperature sensor.

Alternatively, or additionally, the flow-through heater assembly <NUM> includes a temperature sensor <NUM> (<FIG>) disposed within the housing <NUM>. In one form, the temperature sensor <NUM> is a ribbon <NUM>' extending along a surface of the heater <NUM> with a junction disposed at a predetermined location. The temperature sensor <NUM>/<NUM>' detects the fluid temperature at the predetermined location, providing data to determine whether the fluid is heated to a specified temperature prior to exiting the outlet <NUM>. Based on the data, a power controller (not shown) adjusts power to the heater <NUM> to attain the desired temperature. The temperature sensor <NUM>/<NUM>' is a suitable type, such as a thermocouple, a thermistor, or a material with a specified TCR as described above, among others.

In one form, the flow-through heater assembly <NUM> is formed by an additive manufacturing process, such as by way of example, laser sintering, binder jetting, or sheet lamination. In such processes, layers of material are deposited to form each of the halves of the housing (<NUM>/<NUM>), as well as the heater <NUM>, including the anfractuous profiles. In one form, metallic powder is deposited onto a substrate and a laser fuses the powder into a solid metal layer. Then, additional metallic powder is deposited onto the solidified layer and fused by the laser into another layer. The fused layers are successively built to form some or all of the components of the flow-through heater assembly <NUM>, thereby eliminating the need for the mechanical fasteners <NUM> and the seals <NUM> as illustrated and described above. By using an additive manufacturing process, complex geometries, such as the anfractuous path, can be more easily achieved to improve heating of the fluid in the flow-through heater assembly <NUM>.

Referring now to <FIG>, the flow-through heater assembly <NUM> increases turbulence in fluid F flowing through the bore <NUM>, thus improving heat transfer from the heater <NUM> to the fluid F. The fluid flows into the inlet <NUM> of the flow-through heater assembly <NUM> and contacts the heater <NUM>. Because the path of the heater <NUM> is anfractuous, the heater <NUM> more efficiently disrupts the flow of the fluid. The increased turbulence causes more fluid to deflect against the interior surfaces of the housing <NUM> and to contact the heater <NUM> directly, transferring heat from the heater <NUM> to the fluid. Then, the more evenly and efficiently heated fluid exits the flow-through heater assembly <NUM> through the outlet <NUM>.

The shape of the heater <NUM>, and more specifically its anfractuous path, is predetermined to attain a specified thermal time constant to heat the fluid flowing through the flow-through heater assembly <NUM>. In this context, a "thermal time constant" (or "time constant" herein) is a time for a temperature gradient between a current temperature of the fluid and the temperature of the heater to reach a specified percentage (usually <NUM>%) of an initial temperature gradient. The "initial temperature gradient" is defined by a fluid temperature prior to the inlet and the temperature of the heater. A heater with a lower thermal time constant means that the fluid reaches a target temperature faster than a heater with a higher thermal constant. Reducing the thermal time constant of the flow-through heater assembly <NUM> results in heating the fluid more efficiently than a conventional heater, and by replacing a traditional baffle (which acts as a heat sink) with the heater <NUM> having the anfractuous path, the thermal time constant is reduced.

Referring now to <FIG>, another form of a "stacked" flow-through heater assembly is illustrated and generally indicated by reference numeral <NUM>. The flow-through heater <NUM> includes a plurality of individual heaters <NUM> disposed in a multi-chambered housing <NUM>. The housing <NUM> includes a lower piece <NUM>, an upper piece <NUM>, and two (<NUM>) intermediate pieces <NUM> and <NUM>. A continuous fluid conduit <NUM> is formed across all pieces in the housing <NUM> as shown, and the fluid F flows from the lower piece <NUM> through the intermediate pieces <NUM> and <NUM> across and then through the upper piece <NUM>.

The lower piece <NUM> includes an inlet <NUM>, and the upper piece <NUM> includes an outlet <NUM>, as described above. Each intermediate piece <NUM> and <NUM> includes an opening through which fluid flows from the lower piece <NUM> to the upper piece <NUM> or between two adjacent intermediate pieces <NUM> and <NUM>. The heaters <NUM> may be connected in electrical series, or each heater <NUM> may have its own termination pads and power supply as described above. With each heater <NUM> having its own termination pads, a zoned heater assembly can be provided to provide different amounts of power for each layer of the stack. By stacking the heaters <NUM> and in the anfractuous path, the flow-through heater assembly <NUM> provides a longer fluid flow path without increasing a length of the housing <NUM>. It should be understood that two adjacent intermediate pieces <NUM> and <NUM> is merely exemplary, and thus one or more than two adjacent intermediate pieces <NUM> and <NUM> may be employed while remaining within the scope of the present invention. These and other variations of the innovative flow-through heater assembly should be construed as falling within the scope of the present invention.

Unless otherwise expressly indicated herein, all numerical values indicating mechanical/thermal properties, compositional percentages, dimensions and/or tolerances, or other characteristics are to be understood as modified by the word "about" or "approximately" in describing the scope of the present invention. This modification is desired for various reasons including industrial practice, material, manufacturing, and assembly tolerances, and testing capability.

Claim 1:
A flow-through heater assembly (<NUM>, <NUM>) comprising:
a housing (<NUM>, <NUM>) comprising an inlet (<NUM>, <NUM>), an outlet (<NUM>, <NUM>), and a bore (<NUM>, <NUM>) extending between the inlet (<NUM>, <NUM>) and the outlet (<NUM>, <NUM>); and
a heater (<NUM>, <NUM>) disposed within the housing (<NUM>, <NUM>) and extending between the inlet (<NUM>, <NUM>) and the outlet (<NUM>, <NUM>), the heater (<NUM>, <NUM>) comprising at least one opening (<NUM>) proximate the inlet (<NUM>, <NUM>) and at least one opening (<NUM>) proximate the outlet (<NUM>, <NUM>), the heater further defining an anfractuous path from the inlet (<NUM>, <NUM>) to the outlet (<NUM>, <NUM>),
wherein the at least one opening (<NUM>, <NUM>) in the heater (<NUM>, <NUM>) is in fluid communication with the bore (<NUM>, <NUM>) of the housing (<NUM>, <NUM>), the flow-through heater assembly (<NUM>, <NUM>) being characterized in that:
the housing (<NUM>, <NUM>) comprises a first piece (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and a second piece (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), each of the first piece (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and the second piece (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprising adjacent perimeter edges following the anfractuous path.