Field of the invention [0001] The invention relates to a gas humidifier device, and, in particular to an apparatus for accurately controlling the dew point and humidity level of a gas stream.

Background of the invention [0002] In various industrial applications it is desirable to humidify a gas stream. For example, in Proton Exchange Membrane (PEM) fuel cell systems, it is advantageous to provide hydrogen and oxidant input streams with a specific relative humidity and dew point temperature in order to prevent dehydration of membranes included within the fuel cells. However, accurately controlling the dew point temperature and the relative humidity of a humidified gas stream is exceedingly difficult.

[0003] In fact, conventional humidifier devices, such as bubblers and membrane humidifiers, usually function to provide a saturated gas stream and do not have a means for accurately controlling a precise level of relative humidity or dew point temperature. A particular level of relative humidity is typically loosely regulated by a combination of other devices and requires long flow paths that adversely affect dew point temperature control and the amount of condensation from the humidified gas stream. In turn, these factors also contribute to a rather coarse control of the relative humidity level in a gas stream. Moreover, the additional devices and longer flow paths used to control the relative humidity in a gas stream increase the parts count and cost of systems that employ them.

Summary of the invention [0005] According to an aspect of an embodiment of the invention there is provided a gas humidifier including : a humidification portion having a gas inlet, a humidified gas outlet and at least one spray nozzle for emitting a water spray; and a heating jacket surrounding a portion of the humidification portion for regulating the temperature gradient within the humidification portion.

[0006] In some embodiments, the gas humidifier also includes a water storage portion for storing water employed by the humidification portion, wherein the water storage portion includes a water outlet fluidly connectable to at least one of the heating jacket and the at least one spray nozzle. In other related embodiments, a pump is also included, fluidly connecting the water outlet of the water storage portion to at least one of the heating jacket and the at least one spray nozzle, for pumping water from the water storage portion.

[0007] In some embodiments the heating jacket is integrated into the housing of the humidification portion.

[0008] In some embodiments the gas humidifier also includes a reheat portion, connectable to receive a humidified gas stream from the humidified gas outlet of the humidification portion, for further heating of the humidified gas stream. In some related embodiments, the reheat portion includes at least one baffle for separating liquid water droplets from a humidified gas stream during operation.

[0009] Other aspects and features of the present invention will become apparent, to those ordinarily skilled in the art, upon review of the following description of the specific embodiments of the invention.

Brief description of the drawings [0010] For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings that illustrate aspects of embodiments of the present invention and in which: [0011] Figure 1 is a schematic drawing of a gas humidifier according to a first embodiment of the invention; [0012] Figure 2 is a schematic drawing of a gas humidifier according to a second embodiment of the invention; [0013] Figure 3 is a schematic drawing of a gas humidifier according to a third embodiment of the invention; [0014] Figure 4 is a perspective view of the gas humidifier shown in Figure 3; [0015] Figure 5A is an enlarged perspective view of a humidification portion included in the gas humidifier shown in Figure 4; [0016] Figure 5B is a side view of the humidification portion included in the gas humidifier shown in Figure 4; [0017] Figure 6A is an enlarged perspective view of a reheat portion included in the gas humidifier shown in Figure 4; [0018] Figure 6B is a side view of the reheat portion included in the gas humidifier shown in Figure 4; [0019] Figure 6C is a side view of a baffle disk included in the reheat portion shown in Figure 6B; [0020] Figure 6D is an end view of the baffle disk included in the reheat portion shown in Figures 6B and 6C; [0021] Figure 7A is an exploded view of the reheat portion shown in Figure 4 in combination with a heating element ; and

[0022] Figure 7B is an exploded side view of the reheat portion and the heating element shown in Figure 7A.

Detailed description of the invention [0023] Accurately controlling a precise relative humidity level in a humidified gas stream is exceedingly difficult. Conventional humidifiers, such as bubblers and membrane humidifiers, do not include a means for controlling the relative humidity or dew point temperature, and are thus typically operated to simply produce a saturated gas stream. In order to regulate the relative humidity level, the saturated gas stream is further processed through another combination of devices and tubing. Moreover, within conventional humidifiers, there is an inherent temperature gradient that detracts from the control over the dew point temperature of the humidified gas stream and how accurately the relative humidity level of the humidified gas stream exiting the humidifier can be regulated by the additional devices and tubing. The temperature gradient is often a result of the difference in temperature around the top and sides of the humidifier, caused by thermal leaking from these areas to the surrounding environment.

[0024] In contrast to this, in some embodiments of the invention there is provided a gas humidifier device that is arranged to more accurately control the relative humidity and dew point temperature of a humidified gas stream directly exiting the gas humidifier. Such a gas humidifier, according to aspects of an embodiment of the invention, may advantageously be employed without additional devices required to further regulate the relative humidity and the dew point temperature of a humidified gas stream produced by the gas humidifier. Accordingly, in some embodiments, the gas humidifier includes a heating jacket that reduces the overall temperature gradient within the gas humidifier, reducing the amount by which the dew point temperature is changed within the gas humidifier and in turn providing more accurate control of the relative humidity.

[0025] Referring to Figure 1, shown is a schematic drawing of a gas humidifier 100 according to a first embodiment of the invention. The gas humidifier 100 is tubular and includes two portions that can be formed as a single structure or provided as two connectable portions forming a single structure. The first portion is a water storage portion 110 and the second portion is a humidification portion 120. In this particular embodiment, the humidification portion 120 is arranged vertically above the water storage portion 110 so that the two portions form a closed and hollow vessel. In other embodiments, as in Figure 3, the water storage portion 110 and humidification portion 120 are not open to one another and in such cases a return port may be provided to channel excess water collected in the humidification portion 120 to the water storage portion 110.

[0026] The water storage portion 110 includes a heating element 112 and a water outlet 113. In some embodiments the water storage portion 110 also includes a water inlet (not shown) and/or a temperature control means (also not shown) that is included to regulate the operation of the heating element 112. In some embodiments, the temperature control means may include a heat sensor and control circuitry.

[0027] For the sake of clarity, the lower and upper portions of the humidification portion 120 are indicated by 120a and 120b, respectively. The lower portion 120a of the humidification portion is adjacent to the water storage portion 110 in this particular embodiment. The lower portion 120a includes a gas inlet 122 and is open to the water storage portion 110. The upper portion 120b includes a humidified gas outlet 128 positioned at the top of the humidification portion 120, and a number of spray nozzles 126 extending down from the top of the humidification portion 120. It is preferable that the gas inlet 122 and the spray nozzles 126 are arranged in the lower and upper portions 120a and 120b of the humidification portion 120, respectively.

Such an arrangement provides a relatively long flow path for the dry gas stream through which the dry gas stream can become humidified during operation.

[0028] The humidification portion 120 also includes a heating jacket 124 that is arranged around the upper portion 120b thereof. In some embodiments the heating jacket 124 is built into the side-walls of the humidification portion 120 and in other embodiments the heating jacket 124 is a separate component that envelops the upper portion 120b. In this particular embodiment, the heating jacket 124 includes a water inlet 127 and a fluid connection feed to the spray nozzles 126. That is, the water inlet 127 is fluidly connected to the spray nozzles 126 via a flow path through the heating jacket 124. In alternative embodiments, the heating jacket 124 and the spray nozzles 126 may have separate and/or independent water inlets.

[0029] The water outlet 113 is connected to the water inlet 127 through a series combination of supporting elements including a pump 140, a heat exchanger 150, a check valve 144 and a water recirculation line 142, respectively. The heat exchanger 150 is operable to regulate the temperature of the water delivered to the heating jacket 124 so that the temperature in the upper portion 120b is substantially the same as the desired dew point temperature. The check valve 144 is provided to reduce water back flow through the heat exchanger 150 and the pump 140 as well as to reduce the instances of trapped gas pockets in the water flow.

[0030] In operation, a volume of water is held in the water storage portion 110, which serves as a reservoir and heat source within the gas humidifier 100. The water level is preferably maintained at a level that is below the gas inlet 122 and above the top of the heating element 112. The heating element 112 is used to maintain the temperature of the water at a first dew point temperature (e. g. 70°C). The pump 140 directs water from the water storage portion 110 through the heating jacket 124 and out of the spray nozzles 126. Specifically, water drawn from the water outlet 113 is delivered into the water inlet 127-after flowing through heat exchanger 150, the check valve 144 and the water recirculation line 142-by operation of the pump 140.

[0031] Simultaneously, a dry gas stream is delivered into the humidification portion 120 through the gas inlet 122. As the dry gas stream

flows into the humidification portion 120, the dry gas mixes with the fine mist of water emitted from the spray nozzles 126 and becomes humidified as water molecules effectively evaporate into the dry gas. The humidified gas stream that eventually exits through the humidified gas outlet 128 is typically oversaturated (i. e. it has 100% relative humidity) and has the desired first dew point temperature. Some of the sprayed water simply falls down into the water storage portion 110, since not all of the water is evaporated into the gas stream.

[0032] The heating element 112 and the heat exchanger 150 operate to maintain the first dew point temperature within gas humidifier 100 by closely controlling the temperature of the water in the system. It is preferable that the temperature of the oversaturated gas stream produced is substantially the same as the temperature of the water emitted from the spray nozzles 126 and the temperature of the water in the water storage portion 110, which are both regulated to be the same as the first dew point temperature. According to aspects of this embodiment of the invention, the heating jacket 124, which receives heated water, sets up a substantially uniform temperature gradient within the upper portion 120b of the humidification portion 120. Having a substantially uniform temperature gradient in the upper portion 120b of the gas humidifier effectively maintains the desired first dew point temperature of the oversaturated gas stream and reduces condensation. In many embodiments, during operation the sidewalls of the lower portion 120a are coated with a sufficient amount of water (emitted from the spray nozzles 126) to insulate the gas within the lower portion 120a from the ambient temperature outside the gas humidifier 100. However, in some embodiments the heating jacket 124 is arranged to extend down to further insulate the lower portion 120a. This may be advantageous when the overall length of the humidification portion 120 is relatively long permitting ample surface area for thermal leakage through the lower sidewalls of the humidification portion 120.

[0033] The gas humidifier 100 is operable in environments where the ambient temperature is either higher or lower than the first dew point

temperature. The heating jacket 124 effectively insulates the interior of the gas humidifier 100 from the ambient temperature outside the gas humidifier 100 so that the temperature gradient within the gas humidifier 100 is substantially uniform permitting precise control of the relative humidity and dew point temperature of a humidified gas stream produced by the gas humidifier 100.

[0034] By contrast, in a typical prior art humidifier, the walls of the humidifier are initially much cooler than the desired dew point temperature, which in turn leads to a pronounced temperature gradient within the humidifier. This undesired temperature gradient acts to lower the dew point temperature of the humidified gas stream and cause condensation.

[0035] Referring now to Figure 2, shown is a schematic drawing of a gas humidifier 100'according to a second embodiment of the invention. The gas humidifier 100'is a modified version of the gas humidifier 100 shown in Figure 1 and thus includes many of the same features described above.

Accordingly, features common to both of the gas humidifiers 100 and 100'are designated using the same reference numerals.

[0036] The difference between the gas humidifiers 100 and 100'is that the gas humidifier 100'includes a steam injection means for injecting steam into the dry gas stream before it enters the gas inlet 122. The steam injection means includes a steam injection valve 230 connectable to the gas inlet 122, a controller 235 and a temperature sensor 234. The temperature sensor 234 is provided to sense the temperature within the gas humidifier 100'and/or specifically in the heating jacket 124. The controller 235 is connectable to the temperature sensor 234 to receive temperature information and to the steam injection valve 230. Optionally, a steam trap 232 is provided in the steam line 238 for reducing the amount of steam condensate, in addition to dry steam, that is added to the dry gas during operation.

[0037] The steam injection valve 230 includes first and second input ports that are connectable to a steam line 238 and a dry gas line 236,

respectively. An output of the steam injection valve 230 is connected to the gas inlet 122.

[0038] In operation, the steam injection valve 230 can be adjusted to permit steam to be injected into the dry gas stream at different rates and/or amounts. The controller 235 controls the opening of the steam injection valve 230 based on temperature information collected by the temperature sensor 234 so that the desired dew point temperature of the humidified gas stream can be regulated. During start-up and/or sudden and significant ambient temperature fluctuations, this control arrangement provides a means for regulating the amount of steam that is injected so that the desired dew point temperature is quickly stabilized.

[0039] In alternative embodiments, steam can be directly injected into the humidification portion 120 rather than being combined with the gas stream first. Preferably, the steam is injected at a temperature that is higher than the desired dew point temperature. In such embodiments, the steam can be used to reduce the need for the heating element 112, since heat will be transferred from the steam into the gas humidifier 100'permitting control of the dew point temperature using an independent control of the steam temperature. In such embodiments, this may allow the heating element 112 to be excluded altogether. Alternatively, the steam and the heating element 112 may work in combination to regulate the desired dew point temperature.

[0040] Moreover, it will be appreciated by those skilled in the art that other control and/or monitoring devices can be provided at various locations in a gas humidifier according to an embodiment of the invention. For example, the controller 235 may be adapted to receive readings from other temperature sensors at different locations, such as a second temperature sensor (not shown) in the water storage portion 110.

[0041] Referring now to Figures 3 and 4, shown is a schematic drawing of a gas humidifier 100"according to a third embodiment of the invention. The gas humidifier 100"is a modified version of the gas humidifier 100 shown in Figure 1 and thus includes many of the same features described above.

Accordingly, features common to both of the gas humidifiers 100 and 100"are designated using the same reference numerals.

[0042] There are a number of differences between the gas humidifiers 100 and 100". The gas humidifier 100"illustrated in Figures 3 and 4 includes a reheat portion 130 fluidly connected to the humidified gas output 128 of the humidifier portion 120. Subsequently, the heating jacket 124'and the spray nozzles 126'have been adapted as a result. Specifically, since the reheat portion 130 provides additional heat (as will be described in detail below), the heating jacket 124 does not need to envelop the top of the humidification portion 120. Accordingly, the heating jacket 124'is simply arranged around a portion of the humidification portion 120 that advantageously utilizes the insulation from ambient temperature provided by the heating jacket 124'. The spray nozzles 126'have been moved from their former downwardly projecting positions at the top of the humidification portion 120 to positions along the sidewalls of the humidification portion 120. Additionally, the water storage portion 110 is separated from the humidification portion 120 by an interior wall 160 having a return port 161 that fluidly connects the water storage portion 110 to the humidification portion 120.

[0043]. For safety reasons, the water storage portion 110 is provided with a level switch port 114 to which a level switch 220 is connected. During operation, when the water level in the water storage portion 110 is below the level of port 114, an alarm may be triggered. As humidified gas may also flow through the level switch 220, the level switch 220 is provided with a vent 222.

In the present invention, again for safety reasons, the vent 222 is connected to the reheat portion 130. Any gas flow through the level switch 220 may be returned to the humidified gas stream, directly flow to the ambient environment or channeled to another apparatus.

[0044] Referring now to Figures 5A and 5B, and with further reference to Figures 3 and 4, shown are perspective and side views of the humidification portion 120. In this particular embodiment, the heating jacket 124 is built into the housing 125 of the humidification portion 120. Specifically,

the heating jacket 124 includes an exterior sidewall 125a and an interior sidewall 125b that are arranged to form a fluid cavity that envelops the inner space of the humidification portion 120. As described above, the fluid cavity of the heating jacket 124 fluidly connects the water inlet 127 to the spray nozzles 126.

[0045] With continued reference to Figures 3 and 4, the arrangement of the reheat portion 130 in relation to the rest of the gas humidifier 100"is illustrated. The reheat portion 130 is fluidly connected to the humidification portion 120 to accept humidified gas from the humidified gas output 128. The reheat portion 130 also has an output port 132 that is connectable to other devices for delivery of a humidified gas stream. The reheat portion 130 also optionally includes a vent gas inlet 134 in fluid communication with the level switch 220 via the vent 222 such that any vented process gas can be returned to the humidified gas stream. Since the amount of gas vented is typically relatively small, it does not significantly affect the relative humidity of the humidified gas stream flowing out of the gas outlet 132.

[0046] Since, during operation, there may be liquid water droplets traveling along with the humidified gas stream from the humidification portion 120 into the reheat portion 130, the reheat portion 130 is provided with at least one baffle that is provided to separate liquid water droplets from the humidified gas stream. Referring now to Figure 6A to 6D, and with continued reference to Figures 3 and 4, shown are views of the reheat portion 130 and a baffle disk 136 included in the reheat portion 130. Further, the reheat portion 130 is also provided with a baffle plate 138. The baffles disk 136 is arranged in the bottom end of the reheat portion 130 and the baffle plate 138 is arranged centrally along the length of the reheat portion 130. The baffle disk 136 creates a tortuous flow path for the humidified gas stream flowing from the humidification portion 120 into the reheat portion, which effectively separates out any liquid water droplets carried in the humidified gas flow. The baffle plate 138 creates a tortuous flow path through the reheat portion 130 for the same purpose.

[0047] Heating elements can be provided within the reheat portion 130.

For example, as illustrated in Figures 7A and 7B, a single tortuous heating tube 133 is provided. In operation, the heating element 133 further heats the humidified gas stream to a second temperature, higher than the first dew point temperature. By adjusting the first and second temperatures, the relative humidity can be accurately controlled. The applicant's US Patent Application No. 09/628929 discloses a similar method of controlling relative humidity of a gas stream, and is hereby incorporated by reference.

[0048] While the above description provides example embodiments, it will be appreciated that the present invention is susceptible to modification and change without departing from the fair meaning and scope of the accompanying claims. Accordingly, what has been described is merely illustrative of the application of aspects of embodiments of the invention.

Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.