System and method for control of a fluid heating apparatus

A fluid heating apparatus for heating fluid on a fluid path may comprise a fluid pump, a fluid heater, a temperature sensor to sense fluid temperature and generate a temperature signal, and a temperature control assembly configured to control the temperature of the fluid. The control assembly may comprise a target temperature input to receive a target temperature, a pump control to control operation of the fluid pump to control a flow rate of the fluid, and a heater control to control operation of the fluid heater to control a degree of heat output by the fluid heater. The temperature control assembly may be configured to increase and decrease fluid flow along the fluid path and to increase and decrease heat output of the fluid heater to control the temperature of the fluid at the fluid outlet.

BACKGROUND

Field

The present disclosure relates to fluid heaters and more particularly pertains to a new system and method for control of a fluid heating apparatus for enhancing the control possible for heating fluid.

SUMMARY

In one aspect, the present disclosure relates to a fluid heating apparatus for heating fluid moving along a fluid path between a fluid inlet and a fluid outlet. The fluid heating apparatus may comprise a fluid pump configured to pump fluid along the fluid path, a fluid heater configured to heat fluid moving along the fluid path, the fluid heater comprising a heat generator, and a temperature sensor configured to sense temperature of fluid on the fluid path and generate a temperature signal representative of the temperature of the fluid. The fluid heating apparatus may also comprise a temperature control assembly configured to control the temperature of fluid on the fluid path at the fluid outlet, with the temperature control assembly being in communication with the temperature sensor to receive the temperature signal. The temperature control assembly may comprise a target temperature input configured to receive designation of a target temperature for the fluid on the fluid path at the fluid outlet, a pump control configured to control operation of the fluid pump to control a flow rate of fluid through the fluid path at the fluid pump, and a heater control configured to control operation of the fluid heater to control a degree of heat output by the heat generator of the fluid heater. The temperature control assembly is configured to increase and decrease fluid flow along the fluid path and to increase and decrease heat output of the fluid heater to control the temperature of the fluid at the fluid outlet.

In another aspect, the disclosure relates to a fluid heating apparatus for heating fluid moving along a fluid path between a fluid inlet and a fluid outlet. The fluid heating apparatus may comprise a fluid pump configured to pump fluid along the fluid path, a fluid heater configured to heat fluid moving along the fluid path, the fluid heater comprising a heat generator, and a temperature sensor configured to sense temperature of fluid on the fluid path and generate a temperature signal representative of the temperature of the fluid. The fluid heating apparatus may also comprise a temperature control assembly configured to control the temperature of fluid on the fluid path at the fluid outlet, with the temperature control assembly being in communication with the temperature sensor to receive the temperature signal. The temperature control assembly may comprise a target temperature input configured to receive designation of a target temperature for the fluid on the fluid path at the fluid outlet, a pump control configured to control operation of the fluid pump to control a flow rate of fluid through the fluid path at the fluid pump, and a heater control configured to control operation of the fluid heater to control a degree of heat output by the heat generator of the fluid heater. The temperature control assembly is configured to increase and decrease fluid flow along the fluid path and to increase and decrease heat output of the fluid heater to control the temperature of the fluid at the fluid outlet. The apparatus may further include a fluid holding tank for receiving heated fluid from the fluid heater, with the fluid holding tank having a tank interior. The apparatus may also have a fluid mixing valve configured to re-circulate fluid from the fluid holding tank into the fluid path, with the fluid mixing valve being in communication with the fluid path and being in fluid communication with the interior of the fluid holding tank through a secondary fluid path connecting the fluid mixing valve and the fluid holding tank. The apparatus may also include a fluid level sensor configured to detect a fluid level in the fluid holding tank and generate a fluid level signal representative of the fluid level in the fluid holding tank. The apparatus may also include a fluid level control configured to control a level of fluid in the fluid holding tank, with the fluid level control being in communication with the fluid level sensor to receive the fluid level signal and the fluid level control being in communication with the fluid mixing valve and configured to control the fluid mixing valve and an amount of fluid being drawn through the secondary fluid path and mixed with the fluid on the fluid path.

In yet another aspect, the disclosure relates to a temperature control assembly for a fluid heating apparatus for heating fluid moving along a fluid path between a fluid inlet and a fluid outlet, with the fluid heating apparatus being characterized by including a fluid pump for moving fluid along the fluid path, a fluid heater for heating fluid moving along the fluid path, and a temperature sensor configured to sense temperature of fluid on the fluid path and generate a temperature signal representative of the temperature of the fluid. The temperature control assembly may comprise a pump control configured to control operation of the fluid pump to control a flow rate of fluid through the fluid path at the fluid pump, a heater control configured to control operation of the fluid heater to control a degree of heat output by the heat generator of the fluid heater, and a target temperature input configured to receive designation of a target temperature for the fluid on the fluid path at the fluid outlet. The temperature control assembly may also include a comparator configured to compare the target temperature and a temperature represented by the temperature signal from the temperature sensor. The temperature control assembly may be configured to increase and decrease fluid flow along the fluid path and to increase and decrease heat output of the fluid heater to control the temperature of the fluid at the fluid outlet.

DETAILED DESCRIPTION

With reference now to the drawings, and in particular toFIGS. 1 through 3thereof, a new system and method for control of a fluid heating apparatus embodying the principles and concepts of the disclosed subject matter will be described.

Applicants have recognized that the control of fluid temperature has conventionally occurred in one of two different approaches to vary the amount of heat being transferred to the fluid. One approach to controlling the temperature of the fluid output has been to vary the amount of heat output of the heat source to the fluid. Systems using this approach typically move fluid through a heat exchanger at a constant and unvarying fluid flow rate, while increasing (or decreasing) the amount of heat supplied to the fluid through the heat exchanger, to thereby increase (or decrease) the temperature of the fluid output.

Another approach to controlling the temperature of the fluid output is to vary the flow rate of the fluid flowing through the system. Systems using this approach typically supply a constant and unvarying amount of heat provided by the heat exchanger, while increasing (or decreasing) the flow rate of the fluid through the heat exchanger, to thereby decrease (or increase) the temperature of the fluid output.

Applicants have realized that systems utilizing one of these two approaches are limited in the range of maximum and minimum possible temperatures of the fluid output, and have recognized that a new system utilizing both types of control would extend the range of maximum and minimum fluid output temperatures that are possible to be produced by the system.

More specifically, the flow rate of the fluid and the heat produced by the heat source may be varied to adjust the temperature of the fluid output. The lowest outgoing fluid temperature may be produced when the heat source is at a minimum heat output and the fluid flow rate is at a maximum. Conversely, the maximum outgoing fluid temperature may be produced when the heat source is at its maximum heat output and the fluid flow rate is at a minimum. Between the minimum and maximum fluid temperatures, a broad range of temperatures can be achieved. A control system controls both the heat source and the fluid flow substantially simultaneously and automatically.

In some aspects, the disclosure relates to a fluid heating apparatus10suitable for heating fluid moving along a fluid path12between a fluid inlet14and a fluid output16(seeFIG. 1). Illustratively, the fluid inlet may be in communication with a fluid source such as a municipal water supply, and the fluid outlet may be in communication with a spray gun or other devices or applications for utilizing heated fluid. In the fluid path12, the fluid inlet14is located relatively upstream of the fluid outlet16, and conversely the fluid outlet is located relatively downstream of the fluid inlet. The fluid path12generally defines a path of fluid movement through various elements of the apparatus.

In greater detail, the fluid heating apparatus10may include a fluid pump20which is configured to pump fluid along the fluid path, and thus the fluid pump may be in fluid communication with the path12. Although the fluid pump may be located at various suitable positions along the fluid path between the fluid inlet and outlet, in the illustrative embodiments the fluid pump is connected to the fluid input14in a configuration that pumps or pushes the fluid through the remainder of the fluid path towards the fluid outlet16. Optionally, other positions relative to the fluid path may be utilized. In some of the most preferable embodiments, the fluid pump is operated by a motor, and the motor is electrically operated, although other means of actuating the pump may be utilized.

The apparatus10may also include a fluid heater22which is configured to heat fluid moving along the fluid path through the apparatus. The fluid heater may have a fluid input24and a fluid output26, and in an illustrative embodiment the fluid input is connected to the fluid pump20such that the fluid pump pumps or pushes the fluid through the heater22. Various manners of heating the fluid by the fluid heater may be utilized, and suitable heating technologies are disclosed, for example, in U.S. Pat. Nos. 3,970,048; 4,007,712; 4,095,563; 4,552,162; 4,678,892; 6,006,398; 6,056,207; 6,164,557; and 8,857,736, each of which is hereby incorporated by reference in their respective entireties. A heat generator may be employed to heat the fluid passing through the fluid heater, and in some embodiments the heat generator may include an electrical heating element which is configured to convert electrical power to heat (e.g., through resistance) in order to heat the fluid passing along the fluid path. In other embodiments, the heat generator may comprise a burner which is configured to combust a fuel to generate heat to heat the fluid on the fluid path.

The fluid heating apparatus10may also include a temperature sensor30which is configured to sense the temperature of the fluid on the fluid path, and typically at a position on the fluid path that is downstream of the fluid heater22. The temperature sensor30may generate a temperature signal32which is representative of the temperature of the fluid on the fluid path at the location of the temperature sensor. The temperature sensor may be in fluid communication with the fluid path and may be located just upstream of the fluid outlet16of the apparatus10, although such a position is not critical. The temperature sensor may comprise any suitable type of temperature sensing device including, but not limited to, a thermocouple or thermistor.

The fluid heating apparatus10may also include a temperature control assembly40which is configured to control the temperature of fluid on the fluid path, such as, for example, the temperature at the fluid outlet16. The temperature control assembly40may be in communication with the temperature sensor30to receive the temperature signal32generated by the temperature sensor. In some embodiments, the temperature control assembly40may include a target temperature input42which is configured to receive a designation of a target temperature for the fluid on the fluid path, and generally the fluid temperature at the fluid outlet16. The target temperature input42may comprise a target temperature signal44, which may be manually set by a control or may be set by automatic controls based upon factors internal or external to the fluid heating apparatus10. The temperature control assembly may include a comparator or comparison capability for comparing the target temperature signal44to the temperature signal32to determine, for example, whether the temperature sensed by the temperature sensor is greater than, equals, or is less than the target temperature. Based upon the comparison, the assembly40may act to reduce any deviation of the sensed temperature of the fluid from the target temperature. The assembly may include a processor or other automated control to act on the results of the comparison to tend to reduce the deviation. As described below, the actions of the assembly40may increase or decrease the fluid flow rate and/or increase or decrease the heat applied to the fluid. Relatively small changes or adjustments in these factors may be made until a stable temperature equal or approximately equal to the target temperature is reached.

The temperature control assembly40may also include a pump control46which is configured to control operation of the fluid pump20in order to control the flow rate of fluid through the fluid path at the fluid pump, and thus generally through the fluid heater22. In some embodiments, and in particular those embodiments in which the fluid pump is electrically operated, the pump control46may be configured to control a characteristic of the electrical power being supplied to the motor of the fluid pump in order to cause the motor to operate relatively faster or slower and thereby correspondingly increase or decrease the flow rate through the pump. It will be recognized that fluid pumps employing other types of means of operating the pump may utilize other means for controlling the flow rate produced by the pump.

Additionally the temperature control assembly may include a heater control48which is configured to control operation of the fluid heater22. The heater control48may be configured to control the degree of heat output generated by the heat generator which is transferred to the fluid moving along the fluid path through the fluid heater. In embodiments in which the heat generator comprises an electrical heating element, the heater control48may be configured to control a characteristic of the electrical power being supplied to the electrical heating element of the heat generator. In embodiments in which the heat generator comprises a burner burning a fuel, the heater control48may be configured to control the supply of fuel to the burner.

In some embodiments, the fluid heating apparatus10may include a fluid holding tank50which is configured for receiving heated fluid from the fluid heater (seeFIG. 2). Utilization of the fluid holding tank50may be suitable in applications in which a continuous flow of heated fluid is not required, or in which a large volume of heated fluid may be periodically required. The fluid holding tank50may have a tank interior52which is configured to receive fluid from the fluid path12, and the tank may have a tank fluid inlet54and a tank fluid outlet56. The tank fluid inlet may be in communication with the fluid path from the fluid output26of the fluid heater, and the tank interior may form a portion of the fluid path. In embodiments of the apparatus10employing the holding tank50, the temperature sensor30may be configured to detect temperature of fluid in the fluid holding tank, and the temperature sensor may be located in the interior52of the tank, although this positioning, while beneficial, is not critical. As the tank fluid outlet56may form the fluid outlet16of the apparatus10, the temperature of fluid in the tank50may reflect the temperature of fluid that is produced by the apparatus at the fluid outlet16. Embodiments with the fluid holding tank50may also include a fluid level sensor58which is configured to detect a level of the fluid in the holding tank, and the fluid level sensor may generate a fluid level signal59which is representative of the fluid level in the fluid holding tank at a particular time. The fluid level sensor58may be located in the interior of the fluid holding tank, or at least a portion thereof may be positioned in the interior. Embodiments of the fluid heating apparatus10that employ the fluid holding tank may also utilize a system for recirculating fluid from the tank through the fluid heater22in order to maintain a desired or target temperature of the fluid in the tank50. In such embodiments, a fluid mixing valve60may be configured to recirculate fluid from the interior of the fluid holding tank into the fluid path. The fluid mixing valve60may be in communication with the fluid path, and may be located relatively upstream of the fluid heater22in the path, and may also be located upstream of the fluid pump20in the path. The fluid mixing valve60may be in fluid communication with the interior of the tank50through a secondary fluid path62and the secondary fluid path may connect the fluid mixing valve to the fluid holding tank for drawing fluid from the tank to the mixing valve upon operation of the fluid pump20. The fluid mixing valve may be of a type that may normally be completely open or completely closed, or may be of the type that has varying degrees of an open condition. The fluid mixing valve60may also be in communication with the fluid input14, so that fluid exiting the valve60may include various degrees of “new” fluid and recirculated fluid depending upon the degree to which the mixing valve is open to these two sources of fluid.

A fluid level control64may be provided which is configured to control the level of fluid in the fluid holding tank. The fluid level control may be in communication with the fluid level sensor58to receive the fluid level signal representing the current fluid level in the tank50. The fluid level control may also be in communication with the fluid mixing valve, and may be configured to control the condition of the fluid mixing valve to thereby control the amount (if any) of fluid that is being drawn through the secondary fluid path62and mixed with the fluid on the fluid path12. By this configuration, the fluid mixing valve may be caused to reduce or stop the supply of “new” fluid from the fluid input if the fluid level sensor is detecting that the fluid level in the tank50is acceptable, such that the fluid moving along the fluid path through the heating assembly is primarily recirculated fluid from the tank to achieve or maintain the target temperature in the tank. Conversely, when the fluid level sensor detects that the fluid level in the tank50is lower than desired, the fluid mixing valve60may be caused by the level control64to provide a greater amount or degree of fluid from the fluid input rather than utilizing recirculated fluid from the secondary fluid path62.

In another aspect, the disclosure relates to a method of heating a fluid using a fluid heating apparatus having some or all of the features and elements of the aforementioned fluid heating apparatus10. An illustrative implementation of the method100(seeFIG. 3) may include providing a fluid heating apparatus, such as an apparatus including a fluid pump, a fluid heater, a temperature sensor, a temperature control assembly including a pump control and a heater control.

The system may detect a current temperature of the fluid on the fluid path at a temperature sensor (block102), and may compare the current fluid temperature to a temperature control setting for the target temperature in the fluid (block104). If the comparison of the current fluid temperature and the target temperature determines that the current temperature is equal or approximately equal to the temperature setting (block106), then the system continues to detect or sense the current fluid temperature (block102) and compare it to the target temperature (block104). If it is determined that the current temperature is not equal or substantially equal to the target temperature (block106), then a determination is made whether the current temperature is greater or lesser than the target temperature (block108).

If the current temperature is greater than the target temperature, and thus the fluid temperature is relatively too high with respect to the target temperature, then a sub-process may be utilized to reduce the temperature of the fluid on the fluid path. A determination may be made whether the fluid pump is operating at a maximum flow rate (block110), and if not, then the pump speed may be increased to increase the fluid flow rate through the pump (block112) and thus through the fluid path through the fluid heater. If it is determined that the pump is operating at the maximum flow rate for the pump (block110), then a determination may be made whether the fluid heater is operating at a minimum heating level (block114). In the case of a heater employing combustion, this may be determined by determining if the burner is operating at its minimum fuel burning rate. In the case of an electrically powered heater, this may include a determination of whether the heating element is operating at its minimum power setting, or if power is completely cut off to the element. If it is determined that the heater is operating at its minimum level (block114), then a determination may be made that the temperature being produced by the heating apparatus is the minimum temperature possible (block116) which may lead to other steps being taken that will not be detailed here. If it is determined that the heater is not operating at the minimum level (block114), then the heat level produced by the heater assembly may be decreased in order to decrease the heat being transferred to the fluid moving along the fluid path (block118). At this point, the current fluid temperature of the fluid is detected (block102) and based upon the current fluid temperature then the process may be repeated to determine if further adjustments need to be made.

If a determination is made that the current temperature of the fluid on a fluid path is less than the target temperature (block108), a sub-process may be initiated for increasing the temperature of the fluid because the current temperature is below the target temperature. A determination may be made whether the pump is operating at its minimum flow rate (block120) and if the pump is not operating at its minimum flow rate, then the pump speed may be decreased in order to decrease the fluid flow rate on the fluid path and through the heating assembly (block122). If it is determined that the pump is currently operating at its minimum flow rate (block120) then a determination may be made whether the heater is operating at the maximum heating level (e.g., maximum fuel burning or maximum current being supplied) (block124), and if the heater is operating at its maximum heating level, then a determination may be made that the temperature of the fluid is at the maximum that can be produced by the fluid heating apparatus (block126) and additional steps may be taken that will not be detailed here. If it is determined that the fluid heater is not operating at its maximum level (block124), then the heat output of the fluid heater may be increased (block128) by some increment and the current temperature may again be detected (block102) and compared (block104) to determine if further adjustments need to be made.

It should be appreciated that in the foregoing description and appended claims, that the terms “substantially” and “approximately,” when used to modify another term, mean “for the most part” or “being largely but not wholly or completely that which is specified” by the modified term.

It should also be appreciated from the foregoing description that, except when mutually exclusive, the features of the various embodiments described herein may be combined with features of other embodiments as desired while remaining within the intended scope of the disclosure.

Further, those skilled in the art will appreciate that the steps shown in the drawing figures may be altered in a variety of ways. For example, the order of the steps may be rearranged, substeps may be performed in parallel, shown steps may be omitted, or other steps may be included, etc.