The present invention generally relates to convection heating and/or cooling systems and, more specifically, to enhancing convection at a working element of a heat exchanger.
Baseboard heating and/or cooling units (hereinafter “baseboard units”) are commonly used as components of heating and/or cooling systems, particularly for residential household applications. Baseboard units typically have low, wide shapes. Referring to
The exemplary baseboard unit 2 includes a housing 12 that is fitted to run along the base of the wall 4. As shown, the conventional housing 12 is substantially rectangular and has side panels 14, a bottom surface 16, a rear surface 18, a top surface 20 and a front surface 22. The housing 12 may also include input ports 24 disposed in one or both of the side panels 14. The input ports 24 may include an electrical connection, a control signal input, and/or a supply and/or return connections for heating and/or cooling fluid (working fluid). Alternatively, working fluid may be supplied and returned through floor cuts made under the housing 12. Or the baseboard unit 2 may be electrically powered. The baseboard unit 2 typically is secured to the wall by fasteners 26, such as screws or the like, that are inserted through mounting holes defined in the rear surface 18 of the housing 12 and into a wall of the room.
As shown in
A working element 34 is mounted in the housing 12, within and across the connecting passage(s) between the upper and lower openings 28, 30, on a supporting structure 36. The working element typically is a finned tube through which a working fluid flows. Alternatively, the working element 34 may include one or more resistive heaters that are supplied with electricity via the electrical connection of the input ports 24.
In a heating mode, for example, the working element 34 is maintained hotter than room temperature by electric current, or by an external working fluid source (not shown). The thermal difference causes heat transfer from the working element 34 to air in the housing 12. As the air is heated, its density decreases so that the heated air rises from the inlet opening 30 through the working element 34 and out the upper outlet opening 28, as indicated by the arrows in
When the working element 34 is operated at full capacity, with a large temperature differential between the ambient temperature of the room and element 34 (i.e., when the working element is maintained at about 160-220° F.), the baseboard unit 2 can operate effectively. For instance, air flows through the housing 12 and upward along the wall 4 at a sufficient flow rate to initiate a larger convection cycle throughout the room. As a result, the heat transfers evenly throughout the room and there is a small temperature gradient. Even heat transfer is generally desired because it produces a more comfortable environment. The required flow rate through the working element 34 varies based on the dimensions of the room and of the working element, according to equations and tables known to those of skill.
Yet, operating the element 34 at full capacity is often inefficient from an energy consumption perspective and may not be required for more than a few days of the year depending on regional weather patterns. In addition, it may take 30-minutes or longer for the element 34 to reach full capacity (i.e., thermal equilibrium with the working fluid and with the air flowing through the housing 12) and for the larger convection cycle to form.
Operation of the baseboard unit 2 is very inefficient as it is ramped up to full capacity. Further, when the temperature differential is relatively small (e.g., when the element 34 is set at low capacity, such as below 160° F.; or, when the working element 34 is disposed at the end of a series of similar working elements supplied with a working fluid that approaches room temperature as it flows through the elements), the convection cycle within the housing 12 has difficulty forming due to lesser density difference between the room air and the air within the housing. As a result, the desired larger convection cycle throughout the room is not formed such that, even if some air does flow through the housing 12 and upward along the wall 4, the rate of upward air flow is not sufficient to induce air turnover throughout the room. This results in uneven heat transfer (i.e., a large temperature gradient across the room) and a less comfortable environment.
These problems exist in both heating- and cooling-modes of operation, but are exacerbated in cooling-mode operation because cooling-mode operation often has greater difficulty forming a convection cycle through the housing 12 as the outlet air must flow across the floor 6, rather than up the wall 4. Across-the-floor flow often tends to produce thermal layering, rather than convective mixing.
Forced or artificial convection, generically, has been well known for enhancing heat transfer through a heat exchanger. However, forced convection has not been implemented in a baseboard unit at least in part because known designs impose an either-or trade off between natural convection and forced convection. Since baseboard units are designed and installed so as to render natural convection sufficient during steady state operation, it is neither efficient, economical, nor desirable to utilize forced convection in existing baseboard units.
Thus, there has been a long-standing need for a baseboard unit that is capable of operating more efficiently, responding more rapidly to changes in demand, at smaller temperature differentials, and, particularly, in a manner that improves cooling-mode operation, without detracting from the well-known benefits of natural convective flow.
Referring to
The element 34 can be connected to an external heat and/or cold source 50, via a connection 51 that is controllable by the control unit 38. The external heat and/or cold source 50 can include a steam boiler, a geothermal heating and/or cooling system or any other source of heat and/or cold including an electrical power supply. The connection 51 can be any of a valve, a switch, a clutch, or any other automatically controllable device commonly used for selectively supplying fluid, electricity, or power to a powered apparatus.
The external heat and/or cold source 50 can be chosen based on energy prices, regional temperature patterns and other available resources. However, the external heat and/or cold source 50 may be inflexible or slow to respond to changing demands. For instance, a steam heat source works well for high temperature differential operation, but is a less effective option at low temperature differential ranges. To operate in a low temperature differential range, a steam-based element might operate at full-on then full-off intervals. This style of operation provides the desired room temperature when averaged over time, but is not necessarily comfortable or efficient.
In addition, existing or already-installed baseboard units may utilize an element 34 that does not effectively service the entire room of the household. For example, a household may only utilize a single type of baseboard unit that is a fixed five feet (5′) in length. Most rooms in the household may have walls with over ten feet (10′) of available space for heating units and, therefore, can be provided with two or more baseboard units. However, some rooms may be oddly configured, have a doorway break up the wall space or have a wall with under ten feet (10′) of available space for a heating unit and, therefore, be limited to only one baseboard unit that is, for instance, located in a remote corner of the room. As a result, the room may be underserved or unevenly served unless expense is incurred for upgrading, replacing or modifying the baseboard unit.
Thus, there is a long-standing need for a baseboard unit with an expanded functional range of the element 34, smooth average output of the element 34, and increased versatility and area of effect.
There is also a need for a wider range of baseboard unit designs that can be applied in a wider range of installations and applications.
There is also a need for an economical means of addressing the deficiencies of the conventional baseboard unit.
An object of the present invention is, therefore, to provide a baseboard unit that overcomes the above-mentioned deficiencies of prior baseboard units.
Accordingly, embodiments of the present invention provide a pilot or priming air flow across a working element of a heat exchanger, thereby disrupting a static boundary layer or aerodynamic surface film adjacent to the heat transfer surfaces of the working element. Disruption of the boundary layer enhances conductive heat transfer from the working element to adjacent air, while also introducing turbulent flow within the adjacent air. In some embodiments of the invention, diminished flow resistance in the turbulent flow regime enhances the rate of natural convective flow driven by air density differences within the baseboard unit housing. In other embodiments, diminished flow resistance enhances forced convection flow driven by a main fan. Accordingly, provision of a pilot air flow, according to an embodiment of the present invention, enhances convective heat transfer between the working element and a main flow of air.
In some embodiments of the present invention, an apparatus for enhancing convection of air through a heat exchanger includes a first means for producing, within a housing of the heat exchanger, a priming flow of pressurized air that impinges upon a working element of the heat exchanger to disrupt a stagnant boundary layer adjacent the working element. Such an apparatus also includes a second means for providing, into the housing, a main flow of air directed toward the working element.
In some embodiments of the present invention, an apparatus is provided for enhancing natural convection of ambient air at a working element of a heat exchanger. Such an apparatus includes a substantially closed and elongated plenum extending generally parallel to and proximate the working element. The plenum of the apparatus is filled with pressurized air and has at least one opening disposed such that a first quantity of the pressurized air exits the opening as a priming air flow, which induces a second quantity of ambient air to flow as a main air flow onto and across a surface of the working element.
In an aspect of the present invention, convection of ambient air at working element of a heat exchanger is enhanced by supplying a pressurized priming air flow onto a the working element of the heat exchanger, substantially without obstructing access of ambient a main air flow to the working element; and by adjusting supply of the pressurized priming air flow to induce impingement of the ambient main air flow onto the working element.
In some embodiments of the present invention, one or more fans are provided for producing the pressurized priming air flow.
In select embodiments of the present invention, at least one of the fans is movably mounted to the heat exchanger and is automatically movable in response to a sensed parameter.
In some embodiments of the present invention, the plenum is provided as a tube, the at least one opening is provided as a slot in the wall of the tube, and a fan is mounted to an open end of the tube for filling the plenum with pressurized air,
In selected embodiments of the present invention, the plenum is disposed below and generally coextensive with the working element.
In some embodiments of the present invention, the plenum is formed by a generally cylindrical first semi-tube of a first diameter and by a generally cylindrical second semi-tube of a diameter smaller than the first diameter. Each of the first and second semi-tubes has a capped end and an open end. The capped ends of the first and second semi-tubes are fastened together. The second semi-tube is nested within and generally radially opposed to the first semi-tube, so that the at least one opening is formed between the two semi-tubes as at least two slots along the length of the generally cylindrical plenum.
In selected embodiments of the present invention, the first and second semi-tubes are additionally fastened together at intervals along the length of the plenum to form a plurality of slots along the length of the plenum.
In selected embodiments of the present invention, the capped ends of the first and second semi-tubes are pivotally fastened together.
In some embodiments of the present invention, the plenum is provided within a portion of a housing generally enclosing the working element. The portion of the housing enclosing the plenum is separated from the remainder of the housing by at least one gap. The gap provides access of ambient air to the working element. The at least one opening of the plenum is disposed adjacent to the at least one gap.
In selected embodiments of the present invention, a fan is mounted in a wall of the plenum facing outward from the working element for producing pressurized air in the plenum.
In other embodiments of the present invention, a baseboard unit is provided with one or more fans mounted along the length of the housing for enhancing natural convection through a heating ventilation and air conditioning unit.
In other embodiments of the present invention, a stacked baseboard system is provided that includes stacked, horizontally-oriented heating and cooling elements and fans for enhancing and/or redirecting natural convective flow within the system.
In select embodiments of the present invention, at least one fan is operatively connected to a fan control unit that regulates the fan in response to sensed parameters.
In select embodiments of the present invention, filters are mounted to the housing of the baseboard unit to reduce the likelihood that foreign objects and/or dirt are inserted or deposited in the housing.
Some embodiments of the present invention provide a fan control unit that monitors operation of the fans to detect when the filter, a specific fan or the heating and/or cooling unit needs to be serviced.
One aspect of the present invention is that, in some embodiments, a baseboard unit can be effectively operated even at smaller-than-conventional temperature differentials between the working element and the room air.
Another aspect of the present invention is that, in some embodiments, cooling-mode operation of a baseboard unit is enhanced.
Another aspect of the present invention is that, in some embodiments, a baseboard unit may be operated with smoothed average output.
Another aspect of the present invention is that, in some embodiments, enhancement of natural convective flow improves the energy efficiency of a baseboard unit.
Another aspect of the present invention is that, in some embodiments, enhancement of natural convective flow improves the response time of a baseboard unit.
Another aspect of the present invention is that, in some embodiments, natural convective flow through a baseboard unit is adjustable so as to increase the versatility and area of effect of a working element within the baseboard unit.
These and other features of the present invention are described with reference to drawings of preferred embodiments of a forced convection baseboard unit. The illustrated embodiments of a forced convection baseboard unit are intended to illustrate selected embodiments of the present invention, without thereby limiting the claims appended hereto.
As used in context of the embodiments described below, the terms “substantially” or “about” are meant to indicate a shape or condition within reasonably achievable manufacturing and assembly tolerances, relative to an ideal desired condition suitable for achieving the functional purpose of a component or assembly. The term “significant” is meant to indicate a shape, condition, feature, or quality that one of ordinary skill would appreciate as measurably affecting desired function or operation of the described embodiment. The term “generally” is meant to indicate a shape or condition inclusive of deviations consequent to normal manufacturing practice, and also includes intentional features that do not significantly deviate from the general shape or condition.
In the improved baseboard unit 2a, one or more fans 52 are mounted to the housing 12 for entrainment of ambient air as further discussed below. In select embodiments, the fans 52 are small electric fans, such as the fans used in a computer or other electronic device for transferring heat away from the processor and/or motherboard. In other embodiments, the fans 52 may be centrifugal (squirrel cage) fans.
When activated, the fans 52 inject small quantities of air across the working element 34. The injected air has dynamic or Bernoulli pressure higher than that of the room air. When the injected air impinges on surfaces of the working element 34, an insulative boundary layer of stagnant air adjacent the working element surfaces becomes entrained with the injected air (similar to the Coanda effect). Air proximate but not adjacent to the working element also becomes entrained by the injected air, and is thus brought directly into contact with the surfaces of the working element. Therefore, the injected air induces air flow across the surfaces of the working element 34 by an amount significantly greater than the rated air flow of the fans 52. Entrainment by the injected air is particularly pronounced in embodiments where the fans 52 inject air through restricted passages, such as between fins of a finned-tube working element 34 (e.g., as shown in
In select embodiments, the priming flow may be enhanced by thermal effects, in particular, by an increase of the priming air temperature across the working element 34. This increase of temperature and consequent expansion may produce standing pressure waves across the working element, so that the priming flow can to some extent act as an acoustic pump driving the main flow through the heat exchanger.
As a result of the incorporation of the fans 52 to the baseboard unit 2a, heat transfer from the element 34 can occur at significantly lower temperatures. For instance, without the fans 52, the element 34 would need to be heated to between 160-220° F. in order to generate a sufficient density difference so as to generate natural convection air flow adequate to provide the proper heating action. In contrast, by substantially lowering flow resistance across the working element 34, the fans 52 enable smaller-than-normal density differences, produced by the element 34 operating at lower-than-normal temperatures, to establish convection currents that move blankets of air around the room, such as across the floor or ceiling or up/down the wall. The blankets of air not only circulate around the room in convection currents, but the blankets of air also radiate heat (or absorb heat) throughout the room. Thus, with the fans 52, the element 34 only needs to be heated to around 120-140° F. Therefore, water flowing through the element 34 can be returned to the heat source 50 at a lower temperature, while still providing effective heating of a room. The lower return temperature enhances efficiency of heat transfer from the heat source 50 to the water.
In an embodiment of the invention as shown in
The fans 52 can be mounted to the walls of the housing 12 using known mounting means, including fasteners or screws, mounting brackets, adhesives, magnets and the like. Fasteners are ideal for simple installations, whereas mounting brackets are preferable for more complex installations. In particular, mounting brackets can be utilized to position the fans 52 in a variety of positions (i.e., away from the walls of the housing 12), orientations (i.e., angled relative to the adjacent wall of the housing 12, like the second fan 52b and the fourth fan 52d, as shown in
In some embodiments, means for actuating one or more of the mounting brackets may be operably connected to a fan control unit as further discussed below with reference to
In cold-mode operation, the fan 52e can direct air in the same direction and, thus, reverse the convection cycle of the element 34. Or, alternatively, the fan 52e can change direction (i.e., have its flow-direction reversed) to supplement the convection cycle of the element 34. The direction of the fan 52e can be set based on monitored operational efficiencies.
It should be appreciated that the fan 52e can alternatively be positioned in register with the upper opening 28, or fans 52 can be positioned at both of the openings 28, 30. Preferably, at least one fan 52 is positioned upstream in the dominant flow path in order to improve the efficiency of the fan 52 with respect to moving the air.
Referring to
The fans 52 can be connected in a daisy-chain manner to the common power and control supply 54. Four fans 52 are shown in
Referring to
The fan control sub-unit 62 shares the input and output devices of the control unit 38, such as the user interface 44, the temperature sensor 46 and the time sensor 48 through the control unit 38. The fan control sub-unit 62 can share the input and output devices of other equipment, such as an external thermometer. The fan control sub-unit 62 can also accept additional inputs, including flow feedback sensors 66 and energy sensors 68. The flow feedback sensors 66 are connected to the fans 52 and monitor feedback from the fans 52. The energy sensors 68 are connected between the power supply 40 and the element 34 and the fans 52 and monitor energy consumption of each of the element 34 and the fans 52, respectively.
By leveraging additional inputs, the fan control sub-unit 62 can further increase the energy efficiency and responsiveness of the improved baseboard units. For example, the fan control sub-unit 62 can implement an algorithm for regulating the fan(s) 52 according to inputs including the room temperature and the outdoor temperature.
The fan control sub-unit 62 can also include a learning module 70 for intelligently regulating the fans 52 based on data collected from the inputs of the control unit 38 and the fan control sub-unit 62. For example, the learning module 70 compares the energy consumption of the element 34 to that of the fans 52 using the input from the energy sensors 68 and regulates the use of the element 34 and the fans 52 based on the comparison. The learning module 70 also analyzes the other inputs and combinations of inputs and, based on the analysis, performs a variety of functions including: providing recommendations of alternative user settings and positions, orientations and directions of flow of the fans 52 that might improve energy efficiency or reduce energy use; and indicating when the element 34 and the fans 52 require service.
As an exemplary embodiment of the learning module 70, the learning module 70 can monitor and analyze the performance of the baseboard unit 2 and fans 52 and, based on the analysis, the fan control sub-unit 62 can control the position, orientation and direction of flow of the fans 52 using electronically-controlled gyroscopic mounting brackets.
As discussed above with reference to
Referring to
The filters 72 clean the air as the air passes through the baseboard unit 2. One advantage of filtering the air is that it reduces the likelihood that dust will be deposited on the element 34 as the air passes through the housing 12. The depositing of dust on the element 34 can act to insulate the element 34 and reduce the efficiency of the baseboard unit 2.
Referring to
The fans 52 can be powered by an alternative power source, such as solar, thermoelectric, hydraulic, pneumatic, piezoelectric or any other available energy source. For example, as shown in
In selected embodiments of the present invention, the duct or plenum 74 may be movably connected to the housing 12. Means for actuating the plenum 74 within the housing 12 may be operably connected for control by the fan control sub-unit 62 in response to one or more sensed parameters. Acceptable actuating means may include a toothed rack driven by a pinion of a DC stepper motor, or a pneumatic piston actuator driven by actuation of air valves. Those of ordinary skill can realize other acceptable means for actuating the plenum 74.
The present invention is easily incorporated into new baseboard units, but is equally adaptable for retrofitting already installed baseboard units of conventional design (see, e.g.,
For instance, referring to
The fans 52 also enable the production of different designs of HVAC units 80. Referring to
Referring to
It should be understood that the foregoing description is only illustrative of the invention. Those skilled in the art can devise various alternatives and modifications without departing from the broader aspects of the present invention.
For instance, it should be appreciated that the baseboard units shown in
It should also be appreciated that the exact configuration of the fans mounted to a particular baseboard unit is dependent upon the overall configuration of heating and/or cooling devices within each room within the household; the size and shape of the room in which the baseboard unit(s) is installed; the size, shape, type and configuration of baseboard unit(s); and the data collected by the learning module from the operation of the baseboard unit having the fans.
In an alternative embodiment of the present invention, a priming air flow may be drawn at a position downstream in the convection cycle, rather than being supplied at a position upstream in the convection cycle.
In an alternative embodiment of the present invention, any or each fan can be replaced by other conventional or after-developed means for supplying a pressurized priming air flow, for example, a compressor, a vacuum, or other air pump. For example, in each embodiment shown as including an air tube, duct cover, or similar plenum for directing pressurized air to induce the movement of ambient air, air within the plenum may be pressurized by any conventional or after-developed means without departing from the scope of the invention. Alternatively, means for providing a priming air flow may include a structure for diverting or siphoning off a portion of a forced air flow supplied by a main fan. Generally, an apparatus according to the present invention may include various means for inducing a priming air flow toward or onto the surfaces of the working element within the baseboard unit, so long as a main natural convective flow, or a main forced flow, is not thereby obstructed. For example, while the illustrated embodiments are limited to natural convective flow, the invention is not meant to be so limited; in particular, embodiments of the invention are contemplated in which the priming flow enhances forced convection by a main fan.
In an alternative embodiment of the present invention, the energy generated by the alternative power source, such as the solar panels, can be diverted to power the control unit, the fan control sub-unit and other electronic devices in the household, or be returned to the electric grid.
This application is a non-provisional of, claims the benefit of, and hereby incorporates herein in its entirety, U.S. Pat. App. No. 61/326,078, filed Apr. 20, 2010.
Number | Date | Country | |
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61326078 | Apr 2010 | US |