Patent Application
20080317447
The invention relates to humidification systems. More particularly, the invention relates to steam humidifier systems and the detection of deposits and accumulations within a humidifier.
The interior spaces of buildings are often at a lower than desired level of humidity. This situation occurs commonly in arid climates and during the heating season in cold climates. There are also instances in which special requirements exist for the humidity of interior spaces, such as in an art gallery or where other delicate items are stored, where it is desired that the interior humidity levels be increased above naturally occurring levels. Therefore, humidifier systems are often installed in buildings to increase the humidity of an interior space.
Humidification systems may take the form of free-standing units located within individual rooms of a building. More preferably, humidification systems are used with building heating, ventilation, and air conditioning (HVAC) systems to increase the humidity of air within ducts that is being supplied to interior building spaces. In this way, humidity can be added to the air stream at a centralized location, as opposed to having multiple devices that increase humidity at multiple points within the building interior. Additionally, because the air within ducts may be warmer than the interior space air during a heating cycle, the additional air temperature can help prevent water vapor from condensing in the vicinity of the humidifier, such as on the inside of the duct.
An issue associated with humidification system is that they should only discharge water vapor into a duct and not liquid water. Liquid water within a duct can create a number of serious problems. For example, liquid water that remains stagnant within a duct can promote the growth of mold or organisms that can release harmful substances into the air flow, potentially causing unhealthy conditions in the building. Liquid water can also cause rusting of a duct which can lead to duct failure, and can create leaks from the duct to the building interior spaces which are unsightly, can cause a slipping hazard, and can lead to water damage to the structure.
One known humidification method involves direct steam injection into an air duct of a building. This approach is most commonly used in commercial buildings where a steam boiler is present to provide a ready supply of pressurized steam. Steam humidification has the advantage of having a relatively low risk of liquid moisture entering a duct or other building space. However, pressurized steam injection systems are associated with a risk of explosion of the steam pressure vessels, as well as a risk of possibly burning nearby people, both of which are very serious safety concerns. In residential applications, there are usually no readily available sources of pressurized steam. An open bath humidifier system may be used, however these are difficult to install because they require a large hole in the duct and can only be used with horizontal or upflow ducts. Alternatively, a residential application may use direct steam injection, but this requires a separate unit to generate pressurized steam and this separate unit is costly. Moreover, the system would suffer from the same disadvantages as are present in commercial direct steam injection systems.
One type of humidifier that is commonly used in residential applications that has the advantages of steam humidification without the need for a separate source of pressurized steam is a tank heater type humidifier. In this type of humidifier, heat is generated within a tank of water, causing the water to boil and steam to be generated. The heat input may be any of a number of different sources, however, commonly an electrical heating element is used. One problem associated with this type of humidifier is that as water is boiled off as steam, the impurities in the water remain in the tank. These impurities generally include minerals that are naturally occurring in most sources of water. Over time, the concentration of these impurities will tend to increase in the tank, leading to greater amounts of impurities that solidify and deposit on the surfaces inside the tank. These deposits can accumulate to the point of creating numerous problems. For example, deposits on a heating coil reduce the heat transfer rate to the water, resulting in lower steam production and possibly causing overheating and failure of the coil. Deposits in the tank can clog passages where water or steam flows in or out, resulting in the failure of the humidifier.
Improved humidification systems are desired. In particular, improved techniques for detecting accumulation of deposits and obstructions within a humidifier are needed.
An aspect of the present disclosure relates to a humidifier configured to determine when the humidifier requires manual cleaning. The humidifier includes a tank for containing water, a heater for heating the water in the tank to generate steam, and one or more water level sensors for detecting the level of water in the tank, including detecting water at a first level and a second level, where the first level is lower than the second level. The humidifier further includes a drain valve for draining water from the tank and a controller. The controller is configured to open the drain valve to drain water from the tank, measure a time interval required for the water to drain from the second level to the first level, and compare the time interval against a threshold value. If the time interval exceeds the threshold value, then the controller is configured to provide an indication to clean the humidifier.
Another aspect of the invention relates to a method for determining whether a tank heater humidifier requires cleaning. The method includes providing a tank having a fill valve for filling the tank with water, a drain valve for draining water from the tank, and a heater for heating water in the tank to produce steam. The method further includes providing one or more sensors configured to detect the level of water in the tank at a first level and a second level, where the first level is lower than the second level. The method also includes the steps of determining whether water is at the second level in the tank of the humidifier, and if not, opening a fill valve until water is at the second level, opening the drain valve, and starting a timer measurement when the water falls below the second level in the tank and stopping the timer measurement when the water falls below the first level in the tank. Lastly, the method includes the step of determining whether the humidifier requires cleaning based on the timer measurement.
The invention may be more completely understood by considering the detailed description of various embodiments of the invention that follows in connection with the accompanying drawings.
While the invention may be modified in many ways, specifics have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives following within the scope and spirit of the invention as defined by the claims.
As described above, minerals, sediments, and other impurities present in water tend to deposit in the tank of a tank heater type humidifier over the course of its operation. These deposits can build up and cause damage and interfere with the proper functioning of the humidifier. However, the rate at which these deposits form depend on a number of variables, including the mineral content of the water (hardness) and the amount of time that the humidifier is operated. In some cases, it is recommended that the user of a humidifier disassemble and manually clean the tank and associated parts at a regular interval, such as every year. This strategy, however, fails to account for the variability in the rate at which deposits form, such that in some cases the tank is cleaned more often than it needs to be, and in others, the tank is not cleaned often enough and consequently the humidifier fails. This strategy also is dependent upon the user actually cleaning the tank, which in many cases is not a reliable assumption, particularly if the user finds it difficult to predict when the tank needs to be cleaned.
One approach used to minimize the amount of cleaning required or to extend the intervals between cleanings is to utilize a regular flush and fill cycle. For example, in one embodiment, the humidifier may be configured to drain the tank once every 30 hours and then refill with fresh water. This technique helps to remove the relatively greater concentration of contaminants that will be present in the tank after a period of operation, and thereby slows down the rate of impurity deposition on the internal surface. Other time intervals may also be used.
Regardless, though, of whether the tank is drained and filled at regular intervals, deposits will still form on internal surfaces of the humidifier. One of the problems with this is that these deposits can clog the drain, either reducing the efficiency of the drain or preventing the tank from draining all together. When this occurs, cascading failures tend to occur where the concentration of contaminants increases in the tank by virtue of the fact that the tank drain is obstructed, thereby increasing the rate of deposit on the surfaces within the tank and ultimately causing functional failure, such as failure of the heating coil. Furthermore, deposits can also form in the inlet to the tank, which tend to increase the fill time and therefore decrease the capacity of the humidifier to satisfy a demand for humidification. Furthermore, if the deposits prevent the tank from being adequately replenished with water, the water level may drop below the level of the heating element. If the heating element is energized without being submerged in water, typically the heating element will overheat and burn out. It is therefore desirable to be able to detect when the accumulated deposits are interfering with the ability of the tank drain and inlet to function properly.
An embodiment of a tank heater type humidifier is depicted in
Tank 22 is shown in
Humidifier 20 includes a fill valve 42 and a drain valve 44. Fill valve 42 is in fluid communication through conduit 54 with a water supply 46, such as a municipal water supply system or a well pump system. Drain valve 44 is in fluid communication through a conduit 56 with a water receiving system 48, such as a municipal water treatment system, a septic system, or a drain field. Humidifier 20 further includes a controller 52 that is in communication with water level sensors 34, 36 and has the ability to control the fill and drain valves 42, 44. Controller 52 also includes one or more timers configured to measure elapsed times.
A typical heating, ventilation, and air conditioning (HVAC) installation that includes a humidifier is depicted in
In operation of humidifier 20, when there is a call for humidification, humidifier 20 is filled by opening fill valve 42 to allow water from supply 46 to flow through conduit 54 into main chamber 30 of tank 22 and to isolated chamber 26. Fill valve 42 will remain open until water is detected at high water sensor 34, at which point fill valve 42 is closed. Heating coil 24 is then energized, causing the temperature of the water in tank 22 to increase in temperature. In some embodiments, water tank 22 is filled prior to there being a demand for humidification, such as at installation or system start-up, and then waits for a call for humidification to energize the heating coil 24. As the water in tank 22 is heated, the water in tank 22 will begin to boil and steam will form at the top 50 of tank 22. A very slight pressure will be established in the top area 50 of tank 22, driving steam through tube 38 and into duct 40. Tube 38 is configured to allow sufficient steam to flow into duct 40 that very little pressure will build in tank 22. In other embodiments, no pressure builds in tank 22 and steam is carried by convection into duct 40. The steam enters the air in duct 40 where it is carried to conditioned spaces within a building.
As water is converted to steam, the water level in tank 22 will decrease. With sufficient operation, the water level will drop below the height of low water sensor 36. So long as there is still a demand for humidification, when water falls below the height of low level sensor 36, fill valve 42 will be opened and remain open until water reaches high level sensor 34.
Controller 52 also includes settings to control a regular drain cycle. For example, controller 52 may have a drain cycle time setting, TDC, that is configured to initiate a drain cycle every 24 or 48 hours of elapsed time, or alternatively, could be configured to initiate a drain cycle every 10, 15, or 20 hours of operating time. Elapsed time is a measurement of real time since the tank 22 has been filled, and operating time is a measurement of the amount of time that the heating coil 24 is energized to create steam. Other time intervals are equally usable and are set according to the desired performance of the humidifier 20, the quality of the water being used, or other considerations. When a drain cycle is initiated, heating coil 24 is de-energized and drain valve 44 is opened to allow water from tank 22 to flow under the force of gravity through drain valve 44 and conduit 56 to water receiving system 48. In some embodiments, before drain valve 44 is opened, fill valve 42 is opened to fill tank 22 to high level sensor 34. Then the fill valve 42 is turned off after water level reaches the high level sensor 34. This allows the drain cycle to start from a known water level in tank 22.
In some embodiments, the drain valve is kept open a set amount of time (estimated complete drain time, TECD) that would ordinarily be expected to allow all of the water in tank 22 to drain completely. For example, a setting such as 3.5 minutes may be programmed into controller 52 based on the expected drainage of tank 22, where the amount of time is a function of the tank size, the restriction in drain valve 44 and conduit 56, and any other factors affecting the amount of time for the tank to drain under normal circumstances. In other embodiments, TECD may be estimated by controller 52 based on how long it takes the water to drop from the high level sensor to the low level sensor. In some embodiments, the fill valve 42 is kept open while drain valve 44 is open to provide additional flushing and cleaning of the valve and tank. However, generally water will flow at a greater rate through drain valve 44 than through fill valve 42, and therefore the tank 22 will typically drain despite fill valve 42 being open.
After TECD elapses, drain valve 44 is closed and, if fill valve 42 is not open, then fill valve 42 is opened. In some embodiments, there is no water sensor at the bottom of tank 22, such that it is not possible to determine whether tank 22 drains completely, so TECD is used to determine when to refill. In some embodiments, TECD may be approximately 1 to 3 minutes, and in other embodiments TECD may be 1 to 6 minutes. However, other time intervals are equally usable and are based on the design and configuration of the particular humidifier. Then water enters tank 22 and fill valve 42 is kept open until water reaches high level sensor 34.
Deposits, sediment, and other obstructions present in the tank 22 or drain valve 44 can be detected by measuring time intervals when the tank 22 is being filled. One time that can be measured is the time TFL from when the drain valve 44 is closed and the fill valve 42 is open to the time that the water reaches the low level sensor 36, or alternatively, the time that the water reaches the high level sensor 34. If this time is too short, it indicates that the tank 22 did not drain completely during the drain cycle, such that when the fill valve 42 was opened the tank was already partially filled. This situation is likely the result of the accumulation of deposits within the tank drain. It should be noted, however, that a predictable fill rate of water increases the accuracy of methods that use filling times to indicate the need for cleaning.
The condition of the drain can also be determined by measuring the time interval during a draining cycle between the high level sensor 34 being uncovered to the time of the low level sensor 36 being uncovered. If this time is too long, this is an indication that the drain is clogged or partially clogged. In addition, if after drain valve 44 is opened and estimated complete drain time TECD has elapsed there is still water in contact with low level sensor 36 (or high level sensor 34), then this is an indication that the drain is clogged or partially clogged.
An embodiment of the components of a control system of humidifier 20 are depicted in
The controller 52 is configured to determine whether the humidifier needs to be cleaned according to the procedure set forth above. However, in order to determine if the drain time or fill time measurements indicate a need to clean the humidifier, it is necessary to define one or more threshold values, such that measurements that deviate from the threshold are judged to be indicative of the need to clean the humidifier. For example, a threshold may be established for the tank drain time, TDC, where drain times in excess of the threshold are used to indicate the need to clean the humidifier. Similarly, a threshold may be established for the tank fill time, TFL, where a fill time that is less than the threshold is used to indicate the need to clean the humidifier. In some cases, the threshold value or values can be set by testing in a controlled environment, such as a laboratory, where a range of anticipated operating conditions can be varied, such as inlet water pressure and outlet flow restrictions. The normal range of fill and drain times can be determined, and then reasonable judgment can be exercised to determine a threshold value for the amount of time that is indicative of a need to clean the humidifier. In some other cases, a reference or baseline value may be established at the time that the humidifier is installed. This technique has the advantage that it takes into account variables unique to the particular installation, such as the supply water pressure and any outlet flow restrictions. The humidifier may be configured with a special switch or protocol for the installer to cycle the humidifier through a fill and drain cycle. Because the humidifier is new at this point and there are no deposits in it, the fill and drain cycle time measurements made during this test cycle are representative of the operation of the humidifier in a state where it does not need to be cleaned. The controller 52 may then include an algorithm or a value for modifying the measured fill and drain cycle times to produce a threshold value or values. For example, the controller 52 may take the measured drain cycle time and add a set time to determine a threshold value, and may take the measured fill cycle time and subtract a set time to determine a threshold value. Alternatively, the controller 52 may take the measured drain cycle time and increase it a certain percentage to determine a threshold value and may take the measured fill cycle time and decrease it a certain percentage to determine a threshold value. Other techniques are usable to determine threshold values.
In use, a measured drain cycle time, fill cycle time, or various combinations thereof, are compared against the corresponding threshold values to determine if there is a problem such that the humidifier requires cleaning. Generally, measured drain cycle times that exceed a corresponding threshold value and measured fill cycle times that are less than a corresponding threshold value are each indicative of the need to clean the humidifier.
The controller may be programmed to initiate a response if a threshold value is met or exceeded. For example, the controller 52 may initiate an audible signal that is indicative of the need to clean the humidifier. Likewise, the controller 52 may initiate a visual signal such as a light or a message that is indicative of the need to clean the humidifier. There are many other usable embodiments for indicating the need to clean the humidifier. In some embodiments, the controller 52 is configured to turn off, or otherwise not utilize the humidifier, until the humidifier has been cleaned. In this case, the controller 52 needs to have some way to receive input that the humidifier has been cleaned. An example is a button or a switch 60 or other form of input that allows the user to provide an indication that the humidifier has been cleaned and is ready for continued operation. In other embodiments, the controller 52 is configured to continue to operate the humidifier after providing an indication of the need to clean the humidifier.
A flow chart of an embodiment of an algorithm for detecting an obstructed drain in a tank heater type humidifier is depicted in
Alternative embodiments of the algorithm depicted in
The present invention should not be considered limited to the particular examples described above, but rather should be understood to cover all aspects of the invention as fairly set out in the attached claims. Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable will be readily apparent to those of skill in the art to which the present invention is directed upon review of the present specification. The claims are intended to cover such modifications and devices.
The above specification provides a complete description of the structure and use of the invention. Since many of the embodiments of the invention can be made without parting from the spirit and scope of the invention, the invention resides in the claims.
