CN115087157A

CN115087157A - Heater bundle for thermal gradient compensation

Info

Publication number: CN115087157A
Application number: CN202210233590.7A
Authority: CN
Inventors: 马克·埃弗利
Original assignee: Watlow Electric Manufacturing Co
Current assignee: Watlow Electric Manufacturing Co
Priority date: 2021-03-10
Filing date: 2022-03-10
Publication date: 2022-09-20
Also published as: EP4057773A2; KR20220127170A; EP4057773A3; MX2022002936A; CA3151354A1; JP2022140400A

Abstract

A heater bundle comprising a plurality of heater assemblies, at least one of the heater assemblies comprising a plurality of heater units, at least one of the heater units defining at least one independently controlled heating zone. The heat supply is configured to vary the thermal conductivity along the length of the at least one heater assembly to compensate for non-uniform temperatures within the at least one heater unit. The heater bundle includes a power supply arrangement including a controller configured to modulate power through the power supply leads to the independently controlled heating zones based on the determined temperature to provide a desired power output along the length of the at least one heater assembly.

Description

Heater bundle for thermal gradient compensation

Cross Reference to Related Applications

This application is a continuation-in-part application of U.S. application No. 16/272,668 entitled "Heater Bundle for Adaptive Control," filed on day 2, month 11, 2019, which is a continuation of U.S. application No. 15/058,838 filed on day 2, month 3, 2016 (now U.S. patent No.10,247,445). The above disclosure is incorporated by reference herein in its entirety.

Technical Field

The present invention relates to electric heaters and more particularly to heaters for heating fluids, such as fluids within heat exchangers.

Background

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

The fluid heater may be in the form of a cartridge heater having a rod arrangement to heat fluid flowing along or past the outer surface of the cartridge heater. The cartridge heater may be arranged inside the heat exchanger for heating the fluid flowing through the heat exchanger. If the cartridge heater is not completely sealed, moisture and fluids can enter the cartridge heater, thereby contaminating the insulation material that electrically isolates the resistive heating element from the metal sheath of the cartridge heater, resulting in dielectric breakdown and thus heater failure. Moisture can also cause a short circuit between the power supply leads and the outer metal sheath. Failure of the cartridge heater can result in costly downtime of the equipment in which the cartridge heater is used.

Disclosure of 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.

The present invention provides a heater system comprising a heater bundle, wherein the heater bundle comprises a plurality of heater assemblies, at least one heater assembly comprises a plurality of heater units, and at least one heater unit is an independently controlled heating zone. The at least one heat providing member is configured to vary the thermal conductivity along the length of the at least one heater assembly to compensate for the non-uniform temperature. A plurality of power conductors are electrically connected to the heater unit and provide a means for determining temperature. The power supply apparatus includes a controller configured to modulate power through the power supply leads to the independently controlled heating zones based on the determined temperature to provide a desired power output along the length of the at least one heater assembly.

In a variant of this heater system, it can be implemented alone or in any combination: the at least one heater unit is an end heater unit disposed at an end of the at least one heater assembly; the heat supply member increases the coefficient of thermal conductivity within the at least one heater unit; at least one heat supply member comprising a thermally conductive sleeve proximate to the resistive heating element of the at least one heater unit, the thermally conductive sleeve having a thermal conductivity higher than a thermal conductivity of a material surrounding the resistive heating element; each heater unit comprises an outer sheath, and wherein at least one heat supply comprises the at least one heater unit with an outer sheath having a greater thickness than the outer sheath of an adjacent heater unit; each heater unit comprises an outer sheath, and wherein at least one heat supply comprises the at least one heater unit with an outer sheath having a greater thermal conductivity than the outer sheath of an adjacent heater unit; the at least one heat supply member comprises at least two power supply leads operatively connected to the at least one heater unit, and wherein at least one of the two power supply leads has a greater thickness proximate the at least one heater unit; the at least one heat supply comprises at least two electrically energizable conductors operatively connected to the at least one heater unit, and wherein at least one of the two electrically energizable conductors has a higher thermal conductivity than the at least one heater unit in close proximity; the at least one heat supplying member includes a length of the at least one heater unit being shorter than a length of an adjacent heater unit; the at least one heater assembly defines a spacing between adjacent heater units and the at least one heat supply includes at least one of a different spacing between heater units; the spacers are disposed between adjacent heater units, and the at least one heat supply member includes a thicker spacer between the at least one heater unit and the adjacent heater unit than other spacers; at least one of the heat supply members includes a plurality of power supply conductors having a cross-sectional area between adjacent heater units that is less than their nominal cross-sectional area; at least one heater assembly comprises a resistive heating element, wherein the at least one resistive heating element functions as a sensor; more than one heater unit defines at least one independently controlled heating zone.

In another embodiment of the invention, a heater system includes a heater bundle including a plurality of heater assemblies, at least one heater assembly including a plurality of heater units, at least one heater unit being an independently controlled heating zone, at least one heat delivery member configured to vary a thermal conductivity along a length of the at least one heater assembly to compensate for non-uniform temperature, and a plurality of power conductors electrically connected to the heater units. Means for determining at least one of heating conditions and heating requirements is provided, and the power supply means comprises a controller configured to modulate power to the independently controlled heating zones via the supply conductors based on the at least one of heating conditions and heating requirements to provide a desired power output along the length of more than one heater assembly.

In a variant of this heater system, it can be implemented alone or in any combination: the at least one heater unit is an end heater unit disposed at an end of the at least one heater assembly; the heat supply member increases the coefficient of thermal conductivity within the at least one heater unit; at least one of heating conditions and heating requirements is selected from the group consisting of a lifetime of the heater unit, a reliability of the heater unit, a size of the heater unit, a cost of the heater unit, a local heater flux, characteristics and operation of the heater unit, and an overall power output; more than one heater unit defines at least one independently controlled heating zone.

In yet another embodiment, a heater system is provided that includes a heater assembly including a plurality of heater units, at least one heater unit being an independently controlled heating zone, at least one heat supply configured to vary a thermal conductivity along a length of the heater assembly to compensate for an uneven temperature, a plurality of power conductors electrically connected to the plurality of heater units, and a power supply device including a controller configured to modulate power through the power conductors to the independently controlled heating zone based on at least one of a heating condition and a heating requirement to provide a desired power output along the length of the heater assembly.

In a variant of this heater system, it can be implemented alone or in any combination: the at least one heater unit is an end heater unit disposed at an end of the heater assembly; means for determining a temperature are provided; means for determining heating conditions or heating requirements are provided; more than one heater unit defines at least one independently controlled heating zone; and the heater assembly includes resistive heating elements, wherein at least one of the resistive heating elements functions as a sensor.

In yet another variation, the heater system is included in an apparatus for heating a fluid. The apparatus includes a sealed housing defining an interior cavity and having a fluid inlet and a fluid outlet, and a heater assembly disposed within the interior cavity of the housing. The heater assembly is adapted to provide a responsive thermal profile to the fluid within the housing. The thermal profile is based on the response of the implementation of the heat supplies as shown and described herein.

Further areas of applicability will become apparent from the description provided herein. 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 disclosure.

Drawings

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

FIG. 1 is a perspective view of a heater bundle constructed in accordance with the teachings of the present invention;

FIG. 2 is a perspective view of a heater assembly of the heater bundle of FIG. 1 in accordance with the teachings of the present invention;

FIG. 3 is a perspective view of a variation of the heater assembly of the heater bundle of FIG. 1 in accordance with the teachings of the present invention;

FIG. 4 is a perspective view of the heater assembly of FIG. 3 with the outer jacket of the heater assembly removed for clarity in accordance with the teachings of the present invention;

FIG. 5 is a perspective view of a core of the heater assembly of FIG. 3 in accordance with the teachings of the present invention;

FIG. 6 is a perspective view of a heat exchanger including the heater bundle of FIG. 1, with the heater bundle partially detached from the heat exchanger to expose the heater bundle for illustration purposes, in accordance with the teachings of the present invention;

FIG. 7 is a block diagram of a method of operating a heater system including a heater bundle constructed in accordance with the teachings of the present invention;

FIG. 8 is a perspective view of a heater assembly including a heat supply in accordance with the teachings of the present invention;

FIG. 9 is a cross-sectional view of the heater assembly along line 9-9 of FIG. 8 in accordance with the teachings of the present invention;

FIG. 10 is a cross-sectional view of the heater assembly taken along line 10-10 of FIG. 8 in accordance with the teachings of the present invention;

FIG. 11 is a perspective view of a heater assembly including another heat delivery component according to the teachings of the present invention;

FIG. 12 is a cross-sectional view of the heater assembly taken along line 12-12 of FIG. 11 in accordance with the teachings of the present invention;

FIG. 13 is a cross-sectional view of the heater assembly taken along line 13-13 of FIG. 11 in accordance with the teachings of the present invention;

FIG. 14 is a perspective view of a heater assembly including another heat sink in accordance with the teachings of the present invention;

FIG. 15 is a side view of the heat supply of the heater assembly of FIG. 14 according to the teachings of the present invention;

FIG. 16 is a perspective view of a heater assembly including a heat sink in accordance with the teachings of the present invention;

FIG. 17 is a perspective view of a heater assembly including a heat supply in accordance with the teachings of the present invention;

FIG. 18 is a cross-sectional view of the heater assembly taken along line 18-18 of FIG. 17 in accordance with the teachings of the present invention;

FIG. 19 is a cross-sectional view of the heater assembly taken along line 19-19 of FIG. 17 in accordance with the teachings of the present invention; and

figure 20 is a perspective view of a heater assembly including a heat supply in accordance with the teachings of the present invention.

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

Detailed Description

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

Referring to FIG. 1, a heater system constructed in accordance with the teachings of the present invention is generally indicated by reference numeral 10. The heater system 10 includes a heater bundle 12 and a power supply device 14 electrically connected to the heater bundle 12. The power supply device 14 includes a controller 15 for controlling the supply of energy to the heater bundle 12. As used in the present invention, "heater bundle" refers to a heater apparatus comprising two or more physically distinct heating devices that can be independently controlled. Thus, when one of the heating devices in the heater bundle fails or deteriorates, the remaining heating devices in the heater bundle 12 may continue to operate.

In one embodiment, the heater bundle 12 includes a mounting flange 16 and a plurality of heater assemblies 18 secured to the mounting flange 16. The mounting flange 16 includes a plurality of apertures 20 through which the heater assembly 18 extends. Although the heater assemblies 18 are arranged in parallel in this embodiment, it should be understood that alternative locations/arrangements of the heater assemblies 18 are also within the scope of the present invention.

As further shown, the mounting flange 16 includes a plurality of mounting holes 22. The mounting flange 16 may be fitted to the wall of a vessel or pipe (not shown) carrying the fluid to be heated by the use of screws or bolts (not shown) passing through the mounting holes 22. In this embodiment of the invention, at least a portion of the heater assembly 18 is immersed in the fluid inside the vessel or pipe to heat the fluid.

Referring to fig. 2, the heater assembly 18 according to one embodiment may be in the form of a cartridge heater 30. The cartridge heater 30 is a tubular heater that generally includes a core 32, an electrical resistance heater wire 34 wrapped around the core 32, a metal sheath 36 encasing the core 32 and electrical resistance heater wire 34, and an insulating material 38. An insulating material 38 fills the space in the metal sheath 36 to electrically isolate the resistance heating wire 34 from the metal sheath 36 and thermally conduct heat from the resistance heating wire 34 to the metal sheath 36. The core 32 may be made of ceramic. The insulating material 38 may be compacted magnesium oxide (MgO). A plurality of power supply wires 42 extend through the core 32 in the longitudinal direction and are electrically connected to the resistance heating wire 34. The power conductor 42 also extends through an end piece 44 of the sealed metal sheath 36. The power supply lead 42 is connected to the power supply device 14 (shown in fig. 1) to supply power from the power supply device 14 to the resistance heating wire 34. Although fig. 2 shows only two power supply wires 42 extending through the end piece 44, more than two power supply wires 42 may extend through the end piece 44. The power supply leads 42 may be in the form of thermally conductive pins. Various configurations and additional structural and electrical details of cartridge heaters are set forth in more detail in U.S. patent nos. 2,831,951 and 3,970,822, which are commonly assigned with the present application and the contents of which are incorporated herein by reference in their entirety. Accordingly, it should be understood that the forms described herein are illustrative only and are not to be construed as limiting the scope of the invention.

Alternatively, a plurality of resistance heating wires 34 and pairs of power supply leads 42 may be used to form a plurality of heating circuits that can be independently controlled to improve the reliability of the cartridge heater 30. Thus, when one of the resistance heating wires 34 fails, the remaining resistance heating wires 34 can continue to generate heat without causing the entire cartridge heater 30 to fail and without causing costly downtime.

Referring to fig. 3 to 5, the heater assembly 50 may be in the form of a cartridge heater having a similar configuration to that of fig. 2 except that the number of cores and the number of power supply leads used are different. More specifically, each heater assembly 50 includes a plurality of heater cells 52 and an outer metal sheath 54 enclosing the plurality of heater cells 52 and a plurality of power conductors 56 therein. An insulating material (not shown in fig. 3-5) is disposed between the plurality of heater cells 52 and the outer metal sheath 54 to electrically isolate the heater cells 52 from the outer metal sheath 54. Each heater unit 52 includes a core 58 and a resistive heating element 60 surrounding the core 58. The resistive heating elements 60 of each heater unit 52 may define one or more heating circuits to define one or more heating zones 62.

In the present embodiment, each heater unit 52 defines one heating zone 62, and the plurality of heater units 52 in each heater assembly 50 are aligned along the longitudinal direction X. Accordingly, each heater assembly 50 defines a plurality of heating zones 62 aligned along the longitudinal direction. The core 58 of each heater unit 52 defines a plurality of through holes 64 to allow the electrical supply leads 56 to extend through the through holes 64. The resistive heating element 60 of the heater unit 52 is connected to the power supply lead 56, which power supply lead 56 is in turn connected to the power supply device 14. The power supply leads 56 provide power from the power supply 14 to the plurality of heaters 52. By properly connecting the power supply leads 56 to the resistive heating elements 60, the resistive heating elements 60 of the plurality of heater units 52 may be independently controlled by the controller 15 of the power supply device 14. Thus, failure of one resistive heating element 60 for a particular heating zone 62 will not affect the proper operation of the remaining resistive heating elements 60 for the remaining heating zones 62. In addition, the heater unit 52 and the heater assembly 50 may be interchanged to facilitate maintenance or assembly.

In this embodiment, six power conductors 56 are used for each heater assembly 50 to power five separate electrical heating circuits on five heater units 52. Alternatively, six power supply leads 56 may be connected to the resistive heating element 60 in a manner to define three completely independent circuits on the five heater units 52. There may be any number of power conductors 56 to form any number of independently controlled heating circuits and independently controlled heating zones 62. For example, seven power supply leads 56 may be used to provide six heating zones 62. Eight power supply wires 56 may be used to provide seven heating zones 62.

The power conductor 56 may include multiple power and return conductors, multiple return conductors and a single power conductor, or multiple power conductors and a single return conductor. If the number of heating zones is n, the number of supply and return electrical leads is n + 1.

Alternatively, a greater number of electrically different heating zones 62 are created by multiplexing, polarity sensing switches and other circuit topologies by the controller 15 of the power supply device 14. Cartridge heaters having six power supply leads for a given number of power supply leads (e.g., for 15 or 30 zones) are disclosed in U.S. patent nos. 9,123,755, 9,123,756, 9,177,840, 9,196,513 and related applications, which are commonly assigned with the present application and the contents of which are incorporated herein by reference in their entirety.

With this configuration, each heater assembly 50 includes multiple heating zones 62, which heating zones 62 can be independently controlled to vary the power output or thermal profile along the length of the heater assembly 50. The heater bundle 12 includes a plurality of such heater assemblies 50. Thus, the heater bundle 12 provides multiple heating zones 62 and tailored heat profiles for heating the fluid flowing through the heater bundle 12 to suit a particular application. The power supply device 14 may be configured to modulate power to each of the independently controlled heating zones 62.

For example, the heater assembly 50 may define "m" heating zones, and the heater beam may include "k" heater assemblies 50. Thus, the heater beam 12 may define m × k heating zones. The multiple heating zones 62 in the heater bundle 12 may be individually and dynamically controlled in response to heating conditions and/or heating requirements, including but not limited to the service life and reliability of the individual heater units 52, the size and cost of the heater units 52, the local heater flux, characteristics and operation of the heater units 52, and the overall power output.

Each circuit or selected heating zone is individually controlled at a desired temperature or a desired power level such that the temperature and/or power profile accommodates changes in system parameters (e.g., manufacturing variations/tolerances, changing environmental conditions, changing inlet flow conditions, e.g., inlet temperature profile, flow rate, velocity profile, fluid composition, fluid heat capacity, etc.). More specifically, due to manufacturing variations and varying degrees of heater degradation over time, the heater units 52 do not produce the same heat output when operated at the same power level. The heater units 52 may be independently controlled to adjust the heat output according to a desired heat profile. The individual manufacturing tolerances of the components of the heater system and the assembly tolerances of the heater system increase with the modulated power of the power supply, or in other words, the manufacturing tolerances of the individual components do not have to be as tight/narrow due to the high fidelity of the heater control.

Each heater cell 52 may include a temperature sensor (not shown) for measuring the temperature of the heater cell 52. When a hot spot in a heater unit 52 is detected, the power supply device 14 may reduce or shut off the power to the heater unit 52 on which the hot spot was detected to avoid overheating or failure of the particular heater unit 52. The power supply device 14 may modulate the energy supply to heater cells 52 adjacent to the disabled heater cell 52 to compensate for the reduced heat output from the particular heater cell 52.

The power supply device 14 may include a multi-zone algorithm to turn off or reduce the power level delivered to any particular zone and increase the power to the heating zones adjacent to the particular heating zone that is disabled and has reduced heat output. By carefully modulating the power to each heating zone, the overall reliability of the system can be improved. By detecting hot spots and controlling the energy supply accordingly, the heater system 10 has improved safety.

Improved heating may be achieved with a heater bundle 12 having multiple independently controlled heating zones 62. For example, some circuits on the heater unit 52 may operate at a nominal (or "typical") duty cycle that is less than 100% (or at an average power level that is a fraction of the heater-generated energy that is applied to the line voltage). The lower duty cycle allows the use of larger diameter resistance heating wires, thereby improving reliability.

Generally, smaller areas will use thinner wire sizes to achieve a given resistance. Variable power control allows for the use of larger wire sizes and can accommodate lower resistance values while protecting the heater from overload by duty cycle limitations associated with the power dissipation capability of the heater.

The use of a scaling factor may be associated with the capacity of the heater unit 52 or the heating zone 62. The multiple heating zones 62 allow for more accurate determination and control of the heater beam 12. A particular heating circuit/zone will allow for more aggressive (i.e., higher) temperatures (or power levels) at nearly all zones, which in turn results in a smaller, less costly design of the heater bundle 12. Such a scale factor and method is disclosed in U.S. patent No.7,257,464, which is commonly assigned with the present application and the contents of which are incorporated herein by reference in its entirety.

The size of the heating zones controlled by the individual circuits can be made equal or different to reduce the total number of zones required to control the distribution of temperature or power to the required accuracy.

Referring to fig. 1, the heater assembly 18 is shown as a single-ended heater, i.e., a heat transfer pin extends through only one longitudinal end of the heater assembly 18. The heater assembly 18 may extend through a mounting flange 16 or bulkhead (not shown) and seal to the flange 16 or bulkhead. Thus, the heater assembly 18 may be removed and replaced separately without removing the mounting flange 16 from the vessel or pipe.

Alternatively, the heater assembly 18 may be a "double ended" heater. In the double-ended heater, the metal sheath is bent into a hairpin shape, and the power supply leads are passed through both longitudinal ends of the metal sheath, so that both longitudinal ends of the metal sheath are passed through and sealed to the flange or the partition. In such a configuration, the flange or baffle would need to be removed from the housing or vessel before the individual heater assemblies 18 could be replaced.

Referring to fig. 6, the heater bundle 12 is incorporated into a heat exchanger 70. The heat exchanger 70 includes a sealed housing 72 defining an interior cavity (not shown), the heater bundle 12 being disposed within the interior cavity of the housing 72. The sealed housing 72 includes a fluid inlet 76 and a fluid outlet 78, and fluid flows into the interior of the sealed housing 72 and out of the interior of the sealed housing 72 through the fluid inlet 76 and the fluid outlet 78. The fluid is heated by the heater bundle 12 disposed in the sealed enclosure 72. The heater bundle 12 may be arranged for cross flow or flow parallel to its length.

The heater bundle 12 is connected to a power supply means 14, which power supply means 14 may comprise means for modulating the power, such as switching means or variable transformers, to modulate the power supplied to the individual zones. The power modulation may be performed as a function of time or based on the detected temperature of each heating zone.

The resistance heating wire may also function as a sensor, using the resistance of the resistance wire to measure the temperature of the resistance wire, and using the same power supply leads to send the temperature measurement information to the power supply device 14. The means of sensing the temperature of each zone will allow the temperature to be controlled along the length (down to the resolution of the individual zones) of each heater assembly 18 in the heater bundle 12. Therefore, an additional temperature sensing circuit and sensing device can be omitted, thereby reducing manufacturing costs. Directly measuring heater circuit temperature is a significant advantage when attempting to maximize heat flux in a given circuit while maintaining the required level of reliability of the system, as it eliminates or minimizes many of the measurement errors associated with using separate sensors. The heating element temperature is the characteristic that has the greatest influence on the reliability of the heater. The use of a resistive element to function as both a heater and a sensor is disclosed in U.S. patent No.7,196,295, which is commonly assigned with the present application and the contents of which are incorporated herein by reference in its entirety.

Alternatively, the power supply leads 56 may be made of different kinds of metals, so that the different kinds of metal power supply leads 56 may produce a thermocouple for measuring the temperature of the resistance heating element. For example, at least one set of power and return leads may comprise different materials such that a junction is formed between the different materials and the resistive heating element of the heater unit and used to determine the temperature of one or more zones. The use of "integrated" and "highly thermally coupled" sensing, e.g., using different metals for the heater, results in the generation of a thermocouple-like signal. The use of integrated and coupled power conductors for temperature measurement is disclosed in U.S. application No.14/725,537, which is commonly assigned with the present application and the contents of which are incorporated herein by reference in its entirety.

The controller 15 for modulating the electrical power delivered to each zone may be a closed loop automatic control system. A closed loop automatic control system receives temperature feedback from each zone and automatically and dynamically controls the delivery of power to each zone, thereby automatically and dynamically controlling the power distribution and temperature along the length of each heater assembly 18 in the heater bundle 12 without the need for continuous or frequent manual monitoring and adjustment.

The heater units 52 as disclosed herein may also be calibrated using a variety of methods including, but not limited to, energizing and sampling each heater unit 52 to calculate its resistance. The calculated resistance may then be compared to a calibrated resistance to determine a resistance ratio, or to a value and then the actual heater unit temperature determined. Exemplary methods are disclosed in U.S. patent nos. 5,280,422 and 5,552,998, which are commonly assigned with the present application and the contents of which are incorporated herein by reference in their entirety.

One form of calibration includes operating the heater system 10 in at least one mode of operation, controlling the heater system 10 to produce a desired temperature for at least one of the independently controlled heating zones 62, collecting and recording the at least one independently controlled heating zone 62 for the mode of operation, then accessing the recorded data to determine operating specifications for the heating system having a reduced number of independently controlled heating zones, and then using the heating system having a reduced number of independently controlled heating zones. For example, the data may include power level and/or temperature information, as well as other operational data from the heater system 10 for which data is collected and recorded.

In variations of the present invention, the heater system may include a single heater assembly 18 rather than a plurality of heater assemblies in the heater bundle 12. The unitary heater assembly 18 includes a plurality of heater units 52, each heater unit 52 defining at least one independently controlled heating zone. Similarly, the power supply lead 56 is electrically connected to each independently controlled heating zone 62 in each heater unit 52, and the power supply device is configured to modulate power to each independently controlled heating zone 62 of the heater unit via the power supply lead 56.

Referring to fig. 7, a method 100 of controlling a heater system includes providing a heater bundle including a plurality of heater assemblies in step 102. Each heater assembly includes a plurality of heater cells. Each heater unit defines at least one independently controlled heating circuit (and thus heating zone). In step 104, power is supplied to each heater unit through power supply leads electrically connected to each independently controlled heating zone in each heater unit. In step 106, the temperature within each zone is detected. The temperature may be determined using a change in resistance of the resistive heating element of the at least one heater unit. The zone temperature may be determined initially by measuring the zone resistance (or, if a suitable material is used, by measuring the circuit voltage).

The temperature values may be digitized. The signal may be communicated to a microprocessor. In step 108, the measured (detected) temperature values may be compared to a target (desired) temperature for each zone. Based on the measured temperatures, the power supplied to each heater unit may be modulated to achieve a target temperature in step 110.

Optionally, the method may further comprise adjusting the modulation power using a scaling factor. The scaling factor may be a function of the heating capacity of each heating zone. The controller 15 may include an algorithm, potentially including a scaling factor and/or mathematical model of the dynamic behavior of the system (including knowledge of the system update time) to determine the amount of power to be provided (by duty cycle, phase angle triggering (ringing), voltage modulation, or similar techniques) to each zone until the next update. The desired power may be converted to a signal that is sent to a switch or other power modulation device to control the power output to the individual heating zones.

In this embodiment, when at least one heating zone is turned off due to an abnormal condition, the remaining zones continue to supply the required power (watts) without failure. When an abnormal condition is detected in at least one of the heating zones, power is modulated to the functional heating zone to provide the desired power. When at least one of the heating zones is turned off based on the determined temperature, the remaining zones continue to provide the required power. Power is modulated to each heating zone according to the received signal, the model, and according to time.

For safety or process control reasons, a typical heater is typically operated below a maximum allowable temperature to prevent a particular location of the heater from undesirable chemical or physical reactions (e.g., combustion/fire/oxidation, coker boil, etc.) occurring at the particular location. Thus, this is typically accommodated by a conservative heater design (e.g., a large heater with a low power density and a large portion of its surface area loaded with a much lower heat flux than would otherwise be possible).

However, with the heater bundle of the present invention, the temperature can be measured and limited anywhere within the heater, and limited to a resolution on the order of the size of the individual heating zones. Hot spots large enough to affect the temperature of the individual circuits can be detected.

Since the temperature of the individual heating zones can be automatically adjusted and therefore limited, the dynamic and automatic limiting of the temperature of each zone will keep that zone and all other zones operating at the optimum power/heat flux level without fear of exceeding the temperature limit required at any zone. This provides the advantage of high upper temperature measurement accuracy compared to the current practice of clamping individual thermocouples to the sheath of one element in the bundle. The reduced margin and the ability to modulate power to individual zones may be selectively and individually applied to the heating zones, selectively and individually, rather than to the entire heater assembly, thereby reducing the risk of exceeding a predetermined upper temperature limit.

The characteristics of the cartridge heater may change over time. In addition, such time-varying characteristics would require cartridge heaters to be designed for a single selected (worse case) flow regime, and thus, the cartridge heater would operate at a sub-optimal state for the other flow regime.

However, due to the provision of multiple heating units in the heater assembly, by dynamically controlling the power distribution across the bundle up to the resolution of the core size, it is possible to achieve an optimized power distribution for various flow conditions, rather than just one power distribution corresponding to just one flow condition in a typical cartridge heater. Thus, the heater bundle of the present application allows for an increase in the total heat flux for all other flow conditions.

In addition, variable power control may increase flexibility in heater design. In heater design, the voltage can be (largely) decoupled from the resistance and the heater can be designed to have the largest wire diameter that can fit into the heater. It allows for increased power dissipation capability for a given heater size and reliability level (or heater life) and allows for a reduced beam size at a given total power level. The power in such an arrangement may be modulated by a variable duty cycle that is part of a currently available or developing variable power controller. The heater bundle can be protected by a programmable (or preprogrammed, if desired) upper limit on the duty cycle of a given zone to prevent "overloading" of the heater bundle.

Referring to fig. 8, a perspective view of a heater assembly 50 having a heat provider is shown. Typically, the heat supply is configured to vary the thermal conductivity along the length of the at least one heater assembly to compensate for the non-uniform temperature. The non-uniform temperature may be within at least one heater unit, such as an end heater unit described below. Alternatively, the non-uniform temperature may be between adjacent heater cells of the heater assembly. Such heating elements may take various forms as set forth in more detail below, and may be implemented in one or more heater units.

As described above, each heater assembly 50 includes a plurality of heater cells 52. Each heater cell 52 defines an end heater cell 52-1 and one of the adjacent heater cells 52-2. As shown in fig. 9-10, each of the end heater unit 52-1 and the adjacent heater unit 52-2 includes a core 58 and a resistive heating element 60 surrounding the core 58. The resistive heating element 60 of each end heater unit 52-1 defines one or more end heating zones 62-1 and the resistive heating element 60 of each adjacent heater unit 52-2 defines one or more adjacent heating zones 62-2. The resistive heating elements 60 of the end heater unit 52-1 and the adjacent heater unit 52-2 are connected to the power conductors 56, which power conductors 56 are in turn connected to the power supply unit 14. Power supply lead 56 supplies power from power supply 14 to end heater unit 52-1 and adjacent heater unit 52-2. By selectively connecting the power conductors 56 to the resistive heating elements 60, the resistive heating elements 60 of the end heater unit 52-1 and the adjacent heater unit 52-2 may be independently controlled by the controller 15 of the power supply device 14.

In one embodiment, the heat supply of the heater assembly 50 is implemented by a thermally conductive sleeve 120. By way of example, referring to FIG. 10, a thermally conductive sleeve 120 is disposed proximate to the resistive heating element 60 of the end heater unit 52-1. In one embodiment, a thermally conductive sleeve 120 surrounds resistive heating element 60 and core 58, and thermally conductive sleeve 120 is disposed between outer metal sheath 54 and resistive heating element 60. It should be understood that in other embodiments, the thermally conductive sleeve 120 may not completely surround the resistive heating element 60 and the core 58. It should also be understood that in other embodiments, the thermally conductive sleeve 120 may not be disposed between the outer metal sheath 54 and the resistive heating element 60.

In one embodiment, the thermally conductive sleeve 120 has a thermal conductivity greater than that of the outer metal sheath 54. Thus, the thermally conductive sleeve 120 is configured to increase the thermal conductivity of the end heater unit 52-1 relative to the adjacent heater unit 52-2, thereby inhibiting undesirable temperature gradients along the heater assembly 50.

Referring to FIG. 11, a perspective view of a heater assembly 50 having another example heat supply is shown. In one embodiment, the heat supply of the heater assembly 50 is implemented by an outer jacket heat supply 130. More specifically, referring to fig. 12-13, the heater assembly 50 includes an end outer metal sheath 54-1 and an adjacent outer metal sheath 54-2, respectively. The end outer metal jacket 54-1 and the adjacent outer metal jacket 54-2 collectively form the outer metal jacket 54, and in one embodiment, the outer jacket heat sink 130 is implemented by the end outer metal jacket 54-2. However, it should be understood that the outer jacket heater 130 may be implemented with any heater unit and is therefore not limited to the end heater unit 52-1.

In one embodiment, the end outer metal sheath 54-1 and the adjacent outer metal sheath 54-2 have different thicknesses and/or thermal conductivities. By way of example, the end outer metal sheath 54-1 has a greater thickness and a higher thermal conductivity relative to the adjacent outer metal sheath 54-2. Thus, end outer metal jacket 54-1 is configured to increase the conductivity of end heater unit 52-1 relative to adjacent heater units 52-2, thereby inhibiting undesirable temperature gradients along heater assembly 50. It should be understood that the end outer metal jacket 54-1 and the adjacent outer metal jacket 54-2 may have different thicknesses and/or thermal conductivities in other variations to selectively control the thermal gradient along the heater assembly 50.

Referring to FIG. 14, a perspective view of a heater assembly 50 having another example heat sink is shown. In this embodiment, the heat supplying part of the heater assembly 50 is implemented by the power supply wire heat supplying part 140. The power conductor heater 140 is implemented by a power conductor 56-1 (which may be at an end as shown in one embodiment, or at any other location along the heater assembly 50) and an adjacent power conductor 56-2. In one embodiment, the power conductor 56-1 and the adjacent power conductor 56-2 collectively form a plurality of power conductors 56. The power conductor 56-1 is connected to the resistive heating element 60 of the end heater unit 52-1 and the adjacent power conductor 56-2 is connected to the resistive heating element 60 of the adjacent heater unit 52-2.

In some embodiments, referring to fig. 14-15, the power conductor 56-1 and the adjacent power conductor 56-2 have different thicknesses, cross-sectional areas, and/or thermal conductivities. As an example, the thickness (T) of the power supply lead 56-2 adjacent thereto ₂ ) And cross-sectional area (which in this embodiment is related to thickness T) ₂ Proportional), the power supply lead 56-1 has a greater thickness (T) than the power supply lead ₁ ) And cross-sectional area (in this embodiment with thickness T) ₁ Proportional ratio). Accordingly, power conductor 56-1 is configured to increase the conductivity of end heater unit 52-1 relative to adjacent heater units 52-2, thereby inhibiting undesirable temperature gradients along heater assembly 50. It should be appreciated that the end power conductor 56-1 and the adjacent power conductor 56-2 may have different thicknesses, cross-sectional areas, and/or other forms of thermal conductivity to selectively control the thermal gradient along the heater assembly 50.

Referring to FIG. 16, a perspective view of a heater assembly 50 having another example heat sink is shown. At one isIn an embodiment, heater assembly 50 includes a space 150 and an adjacent space 152, and the heat supply of heater assembly 50 is defined by space 150 (which may be at an end as shown in one embodiment, or at any other location along heater assembly 50). As used herein, "spacing" refers to the gap between successive heater units 52. By way of example, spacing 150 refers to the gap between end heater cell 52-1 and adjacent heater cell 52-2, and adjacent spacing 152 refers to the gap between adjacent heater cells 52-2. In one embodiment, end spacers 150 (W) ₁ ) The width in the longitudinal direction X is greater than the adjacent spacing 152 (W) ₂ ) Width in the longitudinal direction X.

Although the width (W) of the space 150 is shown in FIG. 16 ₁ ) Equal, but it should be understood that in other embodiments, the width (W) of the space 150 ₁ ) May not be equal. Likewise, although the width (W) of adjacent spaces 152 is shown in FIG. 15 ₂ ) May be equal, but it is understood that in other embodiments, the width (W) of adjacent spaces 152 ₂ ) May not be equal. In one embodiment, the width (W) of the end spaces 150 ₁ ) Less than or equal to the width (W) of adjacent spaces 152 ₂ ). By selectively designating the width (W) of the spaces 150 ₁ ) And the width (W) of adjacent spaces 152 ₂ ) The thermal conductivity of the end heater unit 52-1 (or any other heater unit along the length of the heater assembly 50) relative to the adjacent heater unit 52-2 may be increased to inhibit undesirable temperature gradients along the heater assembly 50.

Referring to FIG. 17, a perspective view of a heater assembly 50 having another example heat sink is shown. In some embodiments, heater assembly 50 includes a space 160 (which may be at an end as shown in one embodiment, or at any other location along heater assembly 50) and an adjacent space 162, and the heat supply of heater assembly 50 is implemented by space 160. Spacing 160 is disposed between end heater unit 52-1 and adjacent heater unit 52-2, and adjacent spacing 162 is disposed between adjacent heater units 52-2. The spacers 160 and adjacent spacers 162 may be implemented from various materials having a relatively low thermal conductivity, such as ceramic materials (e.g., aluminum nitride, boron nitride, polyurethane, and glass-based materials, such as borosilicate glass, acrylic glass, fiberglass, etc.).

In some embodiments, the width (W) of the space 160 in the longitudinal direction X ₃ ) Is larger than the width (W) of the adjacent space 162 in the longitudinal direction X ₄ ) And the width (W) of the space 160 shown in fig. 17 ₃ ) Are equal, it should be understood that in other embodiments, the width (W) of the space 160 ₃ ) May not be equal. Likewise, although the width (W) of adjacent spaces 162 is shown in FIG. 15 ₄ ) Equal, but it is understood that in other embodiments, the width (W) of adjacent spaces 162 ₄ ) May not be equal. In one embodiment, the width (W) of the space 160 ₃ ) Less than or equal to the width (W) of adjacent spaces 162 ₄ ). By selectively designating the width (W) of the space 160 ₃ ) And the width (W) of adjacent spaces 162 ₄ ) The thermal conductivity of end heater unit 52-1, or any other heater unit along the length of heater assembly 50, may be increased relative to the adjacent heater unit 52-2 to inhibit undesirable temperature gradients along heater assembly 50.

In one embodiment, the power conductor heat supplies 140 and the spacers 160 described above with reference to fig. 14 and 15 combine to form a heat supply. As one example, as shown in FIGS. 18-19, the power conductors 56-1 extend along the heater assembly 50 in the longitudinal direction X such that the power conductors 56-1 are disposed within the corresponding spaces 160 and within the corresponding end heater units 52-1 (not shown). Likewise, adjacent power conductors 56-2 extend along heater assembly 50 in longitudinal direction X such that adjacent power conductors 56-2 are disposed within corresponding adjacent spaces 162 and within corresponding adjacent heater cells 52-2 (not shown). In some embodiments, the power conductor 56-1 disposed within a space 160 has a larger cross-sectional area than an adjacent power conductor 56-2 disposed within an adjacent space 162. It should be appreciated that in other embodiments, the power conductor 56-1 disposed within a space 160 may have a cross-sectional area that is less than or equal to the cross-sectional area of an adjacent power conductor 56-2 disposed within an adjacent space 162.

Referring to FIG. 20, a perspective view of a heater assembly 50 having another example heat sink is shown. In one embodiment, the heat supplying elements of the heater assembly 50 are implemented by a variable width heat supplying element 170. Variable width heat supply 170 includes at least one of end heater units 52-1 (or any other heater unit along the length of heater assembly 50). In some embodiments, the width (W) of the end heater unit 52-1 in the longitudinal direction X ₅ ) Is greater than the width (W) of the adjacent heater unit 52-2 in the longitudinal direction X ₆ ). It should be understood that in other embodiments, the width (W) of the end heater unit 52-1 ₅ ) May be less than or equal to the width (W) of the adjacent heater unit 52-2 ₆ ). By selectively designating the width (W) of the end heater unit 52-1 ₅ ) And width (W) of adjacent heater unit 52-2 ₆ ) The conductivity of end heater unit 52-1 relative to adjacent heater units 52-2 may be increased to inhibit undesirable temperature gradients along heater assembly 50. Although not shown, it should be readily understood that the power conductors for the heater units 52 extend between the end heater units 52-1 through the adjacent heater units 52-2.

Referring to fig. 8-20, controller 15 is configured to calculate a temperature within end heater unit 52-1 based on a predefined model (e.g., a mathematical model representing various components and/or dynamic behavior, etc. of heater system 10) and at least one input. In one embodiment, the at least one input includes, but is not limited to, a temperature at another location within the heater bundle 12, an average temperature of the heater units 52, an average temperature of any of the independently controlled heating zones 62 located on the heater assembly 18, a power consumption of the heater bundle 12 and/or any of the heater units 52, and/or an average power consumption of the heater bundle 12 and/or any of the heater units 52 over a predetermined period of time. In one embodiment, the at least one input includes, but is not limited to, a voltage of the heater bundle 12 and/or any one of the heater cells 52, a current leakage of the heater bundle 12 and/or any one of the heater cells 52, and/or an insulation resistance of the heater bundle 12. To perform the functions described herein, the controller 15 includes one or more circuits/components to obtain at least one input (e.g., one or more sensing circuits for measuring the power of the heater unit 52).

As an example, controller 15 is configured to calculate the temperature within end heater unit 52-1 by initially providing a known current to end heater unit 52-1 and measuring the voltage of end heater unit 52-1. The controller 15 then compares the measured voltage to a nominal voltage associated with the known current to identify a voltage deviation and/or a corresponding resistance deviation. Subsequently, using a predetermined model, the controller 15 calculates the temperature of the end heater unit 52-1 based on the voltage deviation and/or the corresponding resistance deviation. As described above, the controller 15 then modulates the power to the independently controlled heating zones 62 through the power conductors 56 based on the temperature of the end heater unit 52-1. To perform the functions described herein, the controller 15 includes one or more processors configured to execute instructions stored in a non-transitory computer-readable medium, such as a Random Access Memory (RAM) and/or a Read Only Memory (ROM).

Unless otherwise expressly stated herein, all numbers 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. Such modifications are desirable for a variety of reasons, including industrial practice, materials, manufacturing and assembly tolerances, and testing capabilities.

Various terms (including "connected," "engaged," "coupled," "adjacent," "immediately adjacent," "on top of … …," "above … …," "below … …," and "disposed") are used to describe spatial and functional relationships between elements. Unless explicitly described as "direct," when a relationship between a first element and a second element is described in the present invention, the relationship may be a direct relationship in which no other intermediate element exists between the first element and the second element, and may also be an indirect relationship in which one or more intermediate elements (spatially or functionally) exist between the first element and the second element. As used herein, at least one of the phrases A, B and C should be construed to mean logic (a or B or C) using a non-exclusive logical or and should not be construed to mean "at least one of a, at least one of B, and at least one of C.

The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention. Furthermore, various omissions, substitutions, combinations, and changes in the form of the systems, devices, and methods described herein may be made without departing from the spirit and scope of the inventions even if the omissions, substitutions, combinations, and changes are not explicitly depicted or described in the drawings of the inventions.

Claims

1. A heater system, comprising:

a heater bundle comprising:

a plurality of heater assemblies, at least one heater assembly comprising a plurality of heater units, at least one heater unit being an independently controlled heating zone;

at least one heat supply configured to vary a thermal conductivity along a length of the at least one heater assembly to compensate for non-uniform temperature;

a plurality of power supply leads electrically connected to the plurality of heater units;

means for determining a temperature; and

a power supply device including a controller configured to modulate power through the power supply leads to the independently controlled heating zones based on the determined temperature to provide a desired power output along the length of the at least one heater assembly.

2. The heater system according to claim 1, wherein the at least one heater unit is an end heater unit disposed at an end of the at least one heater assembly.

3. The heater system according to claim 1, wherein the heat supply increases a thermal conductivity within the at least one heater unit.

4. The heater system according to claim 3, wherein the at least one heat sink comprises a thermally conductive sleeve proximate to the resistive heating element of the at least one heater unit, the thermally conductive sleeve having a thermal conductivity higher than a thermal conductivity of a material surrounding the resistive heating element.

5. The heater system according to claim 3, wherein each heater unit includes an outer jacket, and wherein the at least one heat supply comprises the at least one heater unit having an outer jacket with a thickness greater than an outer jacket of an adjacent heater unit.

6. The heater system according to claim 3, wherein each of the heater units includes an outer jacket, and wherein the at least one heat supply includes the at least one heater unit having an outer jacket with a greater thermal conductivity than an adjacent heater unit outer jacket.

7. The heater system according to claim 3, wherein the at least one heat supply comprises at least two power supply leads operatively connected to the at least one heater unit, and wherein at least one of the two power supply leads has a greater thickness than the at least one heater unit that is proximate.

8. The heater system according to claim 3, wherein the at least one heat supply comprises at least two electrically energizable conductors operatively connected to the at least one heater unit, and wherein at least one of the two electrically energizable conductors has a higher thermal conductivity than the at least one heater unit in close proximity.

9. The heater system according to claim 3, wherein the at least one heat sink comprises a length of the at least one heater unit that is shorter than a length of an adjacent heater unit.

10. The heater system according to claim 1, wherein the at least one heater assembly defines a spacing between adjacent heater units, and the at least one heat supply includes at least one of different spacings between heater units.

11. The heater system according to claim 1, wherein a spacer is disposed between adjacent heater units, and the at least one heat supply member comprises a thicker spacer between the at least one heater unit and an adjacent heater unit than other spacers.

12. The heater system according to claim 1, wherein the at least one heat supply comprises a plurality of power supply conductors having a cross-sectional area between adjacent heater units that is less than a nominal cross-sectional area thereof.

13. The heater system according to claim 1, wherein the at least one heater assembly comprises resistive heating elements, wherein at least one of the resistive heating elements functions as a sensor.

14. The heater system according to claim 1, wherein more than one heater unit defines at least one independently controlled heating zone.

15. A heater system, comprising:

a heater bundle comprising:

means for determining at least one of heating conditions and heating requirements; and

a power supply device comprising a controller configured to modulate power to the independently controlled heating zones via supply conductors based on at least one of heating conditions and heating requirements to provide a desired power output along a length of the at least one heater assembly.

16. The heater system according to claim 15, wherein the at least one heater unit is an end heater unit disposed at an end of the at least one heater assembly.

17. The heater system according to claim 15, wherein the heat supply increases a thermal conductivity within the at least one heater unit.

18. The heater assembly according to claim 15, wherein at least one of the heating conditions and heating requirements is selected from a service life of the heater unit, a reliability of the heater unit, a size of the heater unit, a cost of the heater, a local heater flux, characteristics and operation of the heater unit, and an overall power output.

19. The heater system according to claim 15, wherein more than one heater unit defines at least one independently controlled heating zone.

20. A heater system, comprising:

a heater assembly comprising a plurality of heater units, at least one heater unit being an independently controlled heating zone;

at least one heat supply configured to vary thermal conductivity along a length of the heater assembly to compensate for non-uniform temperature;

a plurality of power supply leads electrically connected to the plurality of heater units; and

a power supply arrangement comprising a controller configured to modulate power to independently controlled heating zones via supply leads based on at least one of heating conditions and heating requirements to provide a desired power output along a length of the heater assembly.

21. The heater system according to claim 20, wherein the at least one heater unit is an end heater unit disposed at an end of the heater assembly.

22. The heater system according to claim 20, further comprising means for determining a temperature.

23. The heater system according to claim 20, further comprising means for determining heating conditions or heating requirements.

24. The heater system according to claim 20, wherein more than one heater unit defines at least one independently controlled heating zone.

25. An apparatus for heating a fluid, comprising:

a sealed housing defining an internal cavity and having a fluid inlet and a fluid outlet; and

the heater system according to claim 20, the heater assembly being disposed within the internal cavity of the housing,

wherein the heater assembly is adapted to provide a responsive thermal profile to the fluid within the enclosure.

26. The heater system according to claim 20, wherein the heater assembly comprises resistive heating elements, wherein at least one of the resistive heating elements functions as a sensor.