This disclosure relates generally to temperature management. More specifically, this disclosure relates to systems and methods for measuring and compensating for heat transfer differences and other environmental heat transfer related aspects of thermal systems.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Heat flux is a useful measure for predicting relative heater element performance, including temperature, transfer efficiency, and life-time. The flux density exhibited by a heater element is defined as Watt density (watts/mm2), which represents a measure of the magnitude of the power that can be concentrated per square millimeter of an element's surface area. A heater element that exhibits a high Watt density will generally provide a fast temperature rise and a lower overall manufacturing cost due to the reduced amount of surface area that is required. However, these advantages are often off-set by the risk of reduced lifetime due to the higher surface temperatures that are encountered, as well as the potential for lower reliability (e.g., over-shooting the desired temperature condition, etc.).
During manufacturing, variances encountered in processing conditions and heater construction can result in differences in the heat flux that are exhibited within different portions of a single heater element or between the various heater elements that are produced. In order to compensate for this manufacturing variability, and ensure reliability at the expense of maximizing performance (e.g., rate of heating) and minimize cost (e.g., lowering the element's surface area), the industry conventionally applies a safety factor, which results in a reduction in the Watt density exhibited by the heater element.
In overcoming the enumerated drawbacks and other limitations of the related art, the present invention provides a smart heating system. The smart heating system generally comprises at least one heater element, a set of predetermined or predictable performance information used to control the heating system, and optionally an electronic conditioning module (ECU) capable of storing and processing the performance information. Alternatively, the smart heating system may further comprise at least one temperature sensor. The performance information may be stored as written text, a bar code, a data matrix, or a radio frequency identification (RFID) tag. The smart heating system heating system may further comprises a LIN or a CAN bus capable of providing a communication pathway between at least two system components.
According to one aspect of the present disclosure, the smart heating system may further comprise at least one support bracket in contact with the at least one heater element and optionally with the at least one temperature sensor. The performance information may include only heater information or a combination of both heater and sensor information. The heater performance information may include the rate of heating that occurs at a desired voltage or under a specified flow condition.
According to another aspect of the present disclosure, the heating system may further comprise a power switch that receives signals from the ECU. In this case, the performance information may also include switch information. The power switch can be controlled by a switch control unit that is in communication with the ECU and uses the switch information. The switch information may include a measurement of the current and/or voltage, as well as the rate of heating associated with the solid state components of the switch as a function of the amount of electrical current that is being switched.
According to yet another aspect of the present disclosure, the smart heating system includes multiple heater elements and temperature sensors, the temperature sensors being a combination of individual sensors or a junction sensor capable of providing more than one temperature measurement. The temperature sensor may be selected as a thermocouple, a thermistor, or a resistance temperature device. The heater element may be selected as a cable heater, a tubular heater, a cartridge heater, a flexible heater, a layered heater, a metal foil, or a metal fleece heater.
The smart heating system may be used to compensate for a thermal gradient present in a diesel oxidation catalyst (DOC), diesel particle filter (DPF), selectic catalytic reducer (SCR), lean NOx traps, or another exhaust component that includes an after-treatment catalyst. Thus diesel exhaust system may be constructed to comprise the smart heating system as described above and hereafter.
A method of providing thermal control in a predetermined application by compensating for a thermal gradient is provided herein. This method comprises providing a smart heating system and establishing thermal control by creating a desired temperature profile. The desired temperature profile can be created by providing power to all or some of the heater elements in the smart heating system simultaneously or alternatingly. Alternatively, the power may be applied to the heater elements in the smart heating system at either the same level or at different levels. The thermal control may be established by using a closed loop control mechanism or open loop control mechanism.
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.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is in no way intended to limit the present disclosure or its application or uses. It should be understood that throughout the description, corresponding reference numerals indicate like or corresponding parts and features.
The present disclosure generally relates to a smart heating system and a method of use associated therewith. The smart heating system made and used according to the teachings contained herein is described throughout the present disclosure in conjunction with diesel exhaust applications in order to more fully illustrate the concept. The incorporation and use of smart heating system in conjunction with other types of thermal management applications is contemplated to be within the scope of the disclosure.
The following specific embodiments are given to illustrate the design and use of smart heating systems according to the teachings of the present disclosure and should not be construed to limit the scope of the disclosure. Those skilled-in-the-art, in light of the present disclosure, will appreciate that many changes can be made in the specific embodiments which are disclosed herein and still obtain alike or similar result without departing from or exceeding the spirit or scope of the disclosure. One skilled in the art will further understand that any properties reported herein represent properties that are routinely measured and can be obtained by multiple different methods. The methods described herein represent one such method and other methods may be utilized without exceeding the scope of the present disclosure.
A smart heating system general comprises at least one heater element with predetermined (e.g., measured) or predictable performance characteristics. One example of such performance characteristics includes the rate of heating for the heater element when it is exposed to a preselected voltage or under a specified process flow condition. Although the average performance for multiple heater elements of the same or substantially similar design that are manufactured by the same process under similar process conditions represents valuable information, the measurement or knowledge of how each individual heater element in the system performs allows one to control the system's overall performance with respect to fast heating without sacrificing overall reliability. One specific example of a performance characteristic for a heater element that can be used to control a system's overall performance includes, without limitation, the locations associated with any non-uniformity in sheath temperature as shown by the temperature profile exhibited by the heating element under a known or predetermined flow/process condition.
A smart heating system provides the benefits of enhanced diagnostic capability in addition to maximizing heat flux and lowering manufacturing cost. A robust diagnostic capability often depends on the variation exhibited from heater element to heater element. A system that is capable of using performance characteristics or information for specific heater elements provides for enhanced diagnostic capability by allowing at least a portion of the random variation that arises from manufacturing variances to be corrected or compensated for.
The specific characteristics or information can be stored in any known format that is desirable, including but not limited to written text, bar codes, data matrix, and radio frequency identification (RFID), as well as being communicated on a digital bus or any other information or communication method known to one skilled in the art.
According to one aspect of the present disclosure, the smart heating system may comprise at least one heater element or alternatively, a combination of at least one heater element and at least one temperature sensor. The sensor may be in contact with the sheath of the heater element (see
Referring to
Since the signal conditioning module 115 may comprise an input and output (I/O), an analog to digital converter (ADC), and a microprocessor, it is possible to use said module to make or communicate other measurements, including but not limited to, the magnitude of current leakage to ground, as well as the voltage and/or current applied to the heater. The measurement of current leakage is useful for determining if the heater insulation resistance (IR) is low and can be used to adjust the rate of applying voltage to the heater in order to remove moisture and/or extend the lifetime of the heater. The measurement of the applied voltage and/or current can be used to determine Power and heat flux associated with the smart heating system 100, as well as to detect the occurrence of any defects or faults.
Still referring to
According to another aspect of the present disclosure, the types of information collected and/or communicated may be utilized to enhance control of the heater system with respect to performance. For example, the information may be used to calculate (a) control parameters to avoid over temperature conditions associated with the heater; (b) a slow ramp for voltage at low current (I)-resistance (R) conditions in order to allow moisture to be evaporated; or (c) a diagnostic limit designed to prolong the lifetime of the heater system. An example of such a diagnostic limit (DL), may include the calculation of the change in temperature (ΔT) per unit time (Δt) per a predetermined variable (x) as shown in Equation 1. This predetermined variable (x) is selected based upon the specific application in which the smart heating system is being used. In certain applications, this variable (x) may be the applied voltage, the amount of fuel used, or the mass flow of an exhaust, among others.
DL=[(ΔT/Δt)/x] Eq. 1
According to another aspect of the present disclosure, the smart heating system may comprise more than one temperature sensor. Referring now to
In many applications, thermal gradients will exist in the environment to which the smart heating system is exposed. For example, thermal gradients may exist within a diesel oxidation catalyst (DOC) that can vary as a function of time and/or engine condition. Thermal gradients may also exist in other after treatment components, such as diesel particle filters (DPF), selective catalytic reducers (SCR), or lean NOx traps, among other components present in the exhaust stream that include an after-treatment catalyst. At least part of the function of an after-treatment catalyst is to facilitate a chemical reaction with the exhaust gases in order to reduce pollutants to comply with emission regulations. Since such chemical reactions have a dependency on temperature, a variation or gradient in temperature will affect the rate at which these reactions proceed. The use of a smart heating system 200 can improve the performance of the after-treatment component by effectively controlling the temperature at a level that facilitates the occurrence of the chemical reaction.
Still referring to
According to another aspect of the present disclosure, the smart heating system may further comprise a support bracket. In some applications, such as in a diesel exhaust system, among others, the vibrations arising from the application may be to such a degree that at least one support bracket is necessary to mount the smart heating system. Referring now to
Alternatively, a multiple junction sensor 311 may be utilized (
In general, a smart heating system 300 that has multiple sensors 310, 311 measuring temperature commands better performance, lower heater cost, greater reliability and enhanced diagnostic capability than a similar sensor comprising a single sensor 310. The use of a multiple junction sensor 311 may become a lower cost alternative as compared to the use of multiple individual sensors 310.
Referring now to
Similar to the use of multiple heaters, the use of multiple sensors located in predetermined places based on their ability to add value in measuring the thermal gradient. The temperature sensors can be thermocouples, thermistors, resistance temperature devices, and any other known means of measuring or detecting temperature. A heater element having a resistance that varies with temperature may be used as a 2-wire heater/sensor combination. The heater element may include without limitation cable heaters, tubular heaters, cartridge heaters, flexible heaters, layered heaters, metal foils, metal fleece heaters, or any other type of heater known to one skilled in the art.
Referring now to
During the construction of a smart heating system, the heater may be mounted with the information related to the heater attached to the heater assembly via a barcode, data matrix, RFID tag, or any other known method. Such heater information may include, among others, rating of heating, resistance, maximum voltage as a function of time, etc. Referring now to
Alternatively, a smart heating system can be utilized that includes information about both the heater and temperature sensor(s). Referring now to
Referring now to
Still referring to
The foregoing description of various forms of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Numerous modifications or variations are possible in light of the above teachings. The forms discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various forms and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.
This application claims the benefit of U.S. Provisional Application No. 61/816,346, entitled “Smart Heating System”, filed on Apr. 26, 2013.
Number | Date | Country | |
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61816346 | Apr 2013 | US |