The principles disclosed herein relate generally to the field of steam dispersion humidification. More particularly, the disclosure relates to a steam dispersion system that controls the amount of steam dispersed in response to a humidity load condition.
In the humidification process, steam is normally discharged from a steam source as a dry gas. As steam mixes with cooler duct air, some condensation takes place in the form of water particles. Within a certain distance, the water particles are absorbed by the air stream within the duct. The distance wherein water particles are completely absorbed by the air stream is called absorption distance. Another term that may be used is a non-wetting distance. This is the distance wherein water particles or droplets no longer form on duct equipment (except high efficiency air filters, e.g.). Past the non-wetting distance, visible wisps of steam (water droplets) may still be visible, for example, saturating high efficiency air filters. However, other structures will not become wet past this distance. Absorption distance is typically longer than the non-wetting distance and occurs when visible wisps have all disappeared and the water vapor passes through high efficiency filters without wetting them. Before the water particles are absorbed into the air within the non-wetting distance and ultimately the absorption distance, the water particles collecting on duct equipment may adversely affect the life of such equipment. Thus, a short non-wetting or absorption distance is desirable.
Steam dispersion systems are configured and sized to accommodate for a design condition, also known as the highest load. The appropriate number of dispersion tubes, number of nozzles, and/or orifice size of the nozzles are chosen to achieve the needed non-wetting or absorption distance and the load at the design condition. Some of the current steam dispersion humidification designs use closely spaced tubes with hundreds, even thousands, of nozzles to achieve a short non-wetting or absorption distance at the highest load. Such designs may undesirably heat the duct air and create significant amounts of unwanted condensate. However, if the number of tubes and/or nozzles is decreased, although the heat gain and condensate is reduced significantly, the non-wetting or the absorption distances are increased dramatically at high humidification loads and steam output may be insufficient when the humidification load is at or near 100%.
It is known that when the humidification loads are at or near 100%, i.e., when the humidification demand is at or near 100%, the non-wetting or the absorption distances are increased greatly. The non-wetting or absorption distances become reduced as the humidification load decreases. Although humidifiers are designed to simultaneously accommodate the highest load and an acceptable short non-wetting or absorption distance, humidifiers spend much of their time at loads significantly below 100%. Therefore, the maximum steam dispersion capacity of a system is not normally required to maintain the desired humidity and the non-wetting or absorption distance. Thus, it would be desirable to control or shut off portions of a dispersion system to reduce the air heat gain and condensate when operating at significantly less than 100% load.
The principles disclosed herein relate to a steam dispersion system that controls the number of active steam dispersion tubes in response to a humidity load condition to ensure acceptable non-wetting or absorption distances and reduced heat gain and condensate when the maximum dispersion capacity of the system is not needed.
In one particular aspect, the disclosure is directed to a steam dispersion system that includes a header which is divided into separate isolated chambers by a divider. The steam dispersion tubes of the system are also divided so as to communicate with only those chambers that they are associated with. The steam dispersion system includes a control system for automatically activating or deactivating, thus supplying or cutting off steam to, a given chamber in response to a humidification demand, so as to only activate dispersion tubes when needed.
A variety of additional inventive aspects will be set forth in the description that follows. The inventive aspects can relate to individual features and combinations of features. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the broad inventive concepts upon which the embodiments disclosed herein are based.
The steam dispersion system having features that are examples of inventive aspects in accordance with the principles of the present disclosure may include at least two independent steam dispersion tubes within a single system wherein each tube may be individually turned on or off to meet a humidity demand. In certain embodiments, wherein the steam dispersion system includes a plurality of steam dispersion tubes, the system selectively allows less than all of its steam dispersion tubes to remain active during light or moderate humidification loads, thus, reducing unwanted heat gain and condensate during these conditions, without sacrificing short non-wetting or absorption distances. The steam dispersion system may include a single control system that regulates all of the tubes, wherein the control system may automatically prevent steam flow into a number of its steam dispersion tubes, inactivating those tubes, when those dispersion tubes are not needed to meet the humidity demands.
A steam dispersion system 10 having features that are examples of inventive aspects in accordance with the principles of the present disclosure is illustrated in
Referring now to
Referring back to
The divider 36 within the header 16 is shaped such that half the tubes 12a communicate only with the first chamber 32 and the other half of the tubes 12b communicate with the second chamber 34, as will be described in further detail below. It should be noted that in other embodiments, the divider may be shaped to divide the header into more than two chambers. It is also contemplated that the total number of tubes do not have to be equally divided with respect to the divided chambers and some chambers may communicate with a larger number of tubes than other chambers.
The divider 36 is shown in closer detail in
The steam dispersion tubes 12 are arranged relative to the header 16 such that half the tubes 12a communicate only with the front passages 44 defined by the divider 36 while half the tubes 12b communicate only with the rear passages 46 defined by the divider 36. The shape of the divider 36 allows the tubes 12a, 12b to align along a length LH of the header 16 and still communicate only with their respective chambers 32, 34. The steam dispersion tubes 12 have lower ends that seat on the top wall 18 (formed by a plate) of the header 16 and above passages 44, 46 with center openings of the tubes 12 in fluid communication with passages 44, 46, wherein each tube 12 aligns with a corresponding opening in top wall 18 of header (please see
Since each chamber 32, 34 in the header 16 includes a separate steam inlet 31, 33, respectively, the amount of the steam flowing into the first and second chambers 32, 34 can be independently controlled. For example, half the steam dispersion tubes 12b, e.g., the tubes communicating with the second chamber 34, may be selectively turned off, while the tubes 12a communicating with the first chamber 32 remain active. The tubes 12 may be selectively or automatically turned on and off via a control system 14 of the steam dispersion system 10, as will be discussed in further detail below.
Referring now to
Referring to
Referring now to
Referring now to
The first and second valves 66, 68 are preferably steam valves that modulate the steam flow rate into the steam dispersion system header 16 based on the difference between a desired humidity value and a measured humidity value. For example, in certain embodiments, the desired humidity value may be a desired relative humidity (RH) and the measured humidity value may be an actual, measured RH in a given environment.
A modulating valve, as used herein, refers to a valve that proportionately controls the steam flow rate according to humidification needs. Since configurations and operations of modulating valves are known in the art, further details thereof will not be provided herein, it being understood that those skilled in the art clearly understand the nature of such valves and how they operate in numerous environments.
It should also be noted that the first and second valves 66, 68 do not necessarily have to be modulating valves and could be any type of a valve that controls the amount of steam flow. The first and second valves 66, 68 may be valves that operate only between an “on” and an “off” position or they may be valves that operate at positions in between a completely “on” and a completely “off” position.
The modulation of the first and second valves 66, 68 may occur automatically via the use of a humidity sensor 70 (such as a humidistat, a humidity transmitter, a dew point sensor, etc.), a controller 74, and steam valve actuators 76, 78 for each of the respective valves, 66, 68. In other embodiments, the steam dispersion system 10 may operate based on conditions other than humidity values, and, thus, other types of sensors 70, such as a thermostat, may be utilized.
When the humidification load is below a predetermined threshold point, the first valve 66 may automatically modulate the steam flow to the first chamber 32. The inactive tubes 12b, those not having steam flowing therethrough, remain inactive and at the duct air temperature, until the predetermined load point is reached.
In a preferred embodiment, when the humidification load is half or less of the design condition load (i.e., when the difference between a desired relative humidity (RH) value and an actual, measured RH value in a given environment is less than a threshold point), the first valve 66 automatically modulates the steam flow to the first chamber 32, to half of the dispersion tubes 12a, based on the difference between a desired RH and the measured RH, as discussed above. The inactive tubes 12b, those not having steam flowing therethrough, remain at the duct air temperature. The inactive tubes 12b do not create condensate or heat the duct air since they are at the duct temperature. Thus, condensate and heat gain can be nearly cut in half when the second steam valve 68 is closed.
The threshold point to activate the second set if tubes 12b may be any predetermined point according to the needs of the system. In certain examples, the threshold point may be defined as a relative humidity demand value that can be met by the maximum capacity of the first valve 66. If the relative humidity demand value (difference between the actual measured humidity value and the predetermined desired humidity value) is great enough such that it cannot be met by the maximum capacity of the first valve 66, then the threshold point of the first valve 66 has been met and the second valve 68 needs to open to meet the demand. As noted above, in certain embodiments, the threshold point may be half of the design condition load.
When the first steam valve 66 is wide open and at its maximum steam flow rate, any additional humidification demand requirements (i.e., increasing the difference between the actual relative humidity value and the predetermined desired relative humidity value to the threshold point) activates the second steam valve 68. Thus, when this demand is reached, the first valve 66 stays wide open while the second steam valve 68 automatically begins to modulate the steam flow rate to the previously inactive tubes 12b, maintaining the desired RH. The steam valve flow rates will be controlled by the control system 14 such that the sum of the flow rates of the first and second valves 66, 68 will be approximately equal to the design condition load.
As RH demand decreases below about half the design condition load (i.e., when the difference between the desired relative humidity (RH) value and the actual, measured RH value in a given environment goes below the threshold point), the second steam valve 68 completely closes, and the first steam valve 66 resumes modulation.
The first and the second valves 66, 68 may, thus, be used to both modulate the steam flow for controlling the RH and to completely turn on and off dispersion tubes 12 as needed. As discussed above, in other embodiments, other types of valves, e.g., non-modulating valves that automatically only turn on or off tubes can be used.
In certain other embodiments, instead of a header divided into two separate valve-regulated chambers, the steam dispersion system may include an on/off valve 11 on each of the tubes 12 or on some of the tubes 12 (please see schematic at
Referring now to
In operating the embodiment of the steam dispersion system 110 illustrated in
It should be noted that, in other embodiments of a steam dispersion system, a single header including separate interior chambers do not have to be used. In other embodiments, the steam dispersion system may include physically separated headers that form physically separate interior chambers, wherein the headers are controlled by and form part of a single steam dispersion system. In such an embodiment, the valves for regulating the steam flow into each of the separate headers may still be controlled by a single control system, operatively connected to a sensor for turning the separate valves on and off to meet the desired humidity demand.
In yet another embodiment of the steam dispersion system, the steam dispersion system may be operated without adding or subtracting steam dispersion tubes as needed in response to the humidification demand. In such an embodiment, the steam dispersion system can be operated by replacing active tubes with another set of differently configured tubes. In such an embodiment, for example, two sets of steam dispersion tubes (each communicating with a separate interior chamber), wherein each set can meet a different demand amount, can be used. For example, each set may include different sized tubes or a different number of tubes than the other set. In such a system, a first plurality of steam dispersion tubes (e.g., smaller sized or smaller number of steam dispersion tubes) communicating with a first chamber may be in the “on” position while a second plurality of steam dispersion tubes (e.g., larger-sized or larger number of steam dispersion tubes) communicating with a second chamber are in the “off” position. When the threshold point is reached, the first plurality of steam dispersion tubes may be completely turned off while the second plurality of steam dispersion tubes are turned on to meet the desired humidification load.
In yet another embodiment of a steam dispersion system, wherein the system includes two chambers, a single valve (e.g., a modulating valve) can be used in combination with a two-position device (e.g., solenoid, gate, damper, etc.) to control steam flow into each of the chambers. In such an embodiment, as illustrated schematically in
Although in the foregoing description of the steam dispersion systems 10, 110, terms such as “top”, “bottom”, “front”, “back”, “right”, and “left” may have been used for ease of description and illustration, no restriction is intended by such use of the terms. The steam dispersion systems 10, 110 described herein can be used in any orientation within a duct.
The above specification, examples and data provide a complete description of the manufacture and use of the composition of the inventive features of the disclosure. Since many embodiments of the inventive aspects of the disclosure can be made without departing from the spirit and scope of the disclosure, the inventive aspects reside in the claims hereinafter appended.
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