TITLE:
A method of humidification of reactant gases using cylindrical candle for PEM Fuel cell stacks
FIELD OF THE INVENTION
The present invention generally relates to humidification of reactant gases (hydrogen and air) for proton exchange membrane fuel cells (PEMFC) which convert chemical energy directly into electrical energy. Precisely, the present invention relates to humidification of gases external to the fuel cell stack using porous honeycomb and mist nozzle sprayer. More particularly, the invention relates to a method to humidify the reactant gases of hydrogen and air/oxygen external to proton exchange membrane fuel cell (PEMFC) stacks.
BACKGROUND OF THE INVENTION
Ionic conductivity of the membrane is known to be of critical importance to obtain better performance of PEM fuel cell.

In practice, gas streams are humidified by flowing the reactants through a humidity exchanger which is an additional subsystem to stack. The exchanger and its associated control system (WO 00/25377, 2000), in their invention the membrane humidification is used to humidify the reactant gases and it is maintained under humidified condition by liquid water injection into the anode side gas, the gas transfers water to the membrane surface through hydrophilic wicks connected between the membrane surface and gas diffusion porous media. In recent times, the gases are humidified using the micro-porous bipolar plates where reactant gases are humidified with the water transferred from cooling side liquid water to gas flow grooves by pervapouration. In their invention (US 7638235B2, 2009), unipolar plate is of micro porous structure wherein pores extended between cooling fluid flow channels and reactant gas flow channels which are filled with hydrophilic material which carries the water from one side to the other side, where gases are humidified. Such unipolar plates are laminated to for bipolar plate, having gas grooves on both the sides and provision for liquid water circulation in between plates for cooling purpose.
In practice, nozzle sprays are widely used for environmental humidification and cooling purpose in various applications where the water is sprayed in the form of mist using ultrasonic spray nozzles to obtain atomized water. In case of cooling and humidification, atomized spray of water subsystem is being assembled prior to suction of cooling fans (US 4042016,1977).

In conventional proton exchange membrane (PEM) fuel cell system as shown in Figure 1, consists of fuel cell stack (1) assisted with various subsystems like air (2), hydrogen(3), cooling(4), humidification(5), power control unit(6) and control unit(7), reactant gases of hydrogen(8) and air(9) are supplied to stack as inlet feed gases and the unreacted gases of hydrogen (10), air (11) and product water (12) exits from stack outlets through their respective outlets and the same liquid water is being collected in the reservoir (13) through a common drain. The controller is central unit to ensure the functioning of the subsystems using the control signals for power conditioning (14), cooling of stack (15), supply cathode air blower (16) of supply of oxygen and humidification of reactant gases (17) for varying the water content present in the feed reactant gases.
Significant work has been carried in the area of gases humidification wherein the gases are humidified external to the stack assembly using various humidifiers. In present invention, a candle of cylindrical in shape is used as the type humidification device which possess highest surface area structure (18) to interact with maximum surface area for the reactant gases to interact with the device surface Hydrogen and Air / oxygen. The device would enable the process

of humidification by humidifying the dry reactant gases one side utilizing the water content available on the high surface area of candle and it is maintained hydrated condition with the use of periodical liquid water circulation arrangement made to spray the water in the form of atomization in the way of fluid flow. In this case, two such devices are assembled one in the line of hydrogen flow and the other in the line of air flow to ensure proper humidification of gases prior to feed them at stack inlets.
OBJECTS OF THE INVENTION
An object of the present invention is to propose a system for humidification of reactant gases of hydrogen and air/oxygen for use in proton exchange membrane fuel cells (PEMFC) in which geometry of the modular humidifier has geometry identical to cylindrical tube place external to fuel cell stack.
Another object of the present invention is to propose for humidifying reactant gases of hydrogen and air/oxygen using modular humidifiers are assembled within the fuel cell system assembly as two additional modules, one in air supply side and the other in Hydrogen supply side.

A still another object of the present invention is to propose for humidifying reactant gases of hydrogen and air/oxygen using modular humidifier exit connected to the inlet of fuel cell stack reactant Hydrogen feed.
Yet another object of the present invention is to propose for humidifying reactant gases of hydrogen and air/oxygen in modular humidifier Air/ oxygen exiting from cathode side humidifier connected to the inlet fuel cell stack reactant air/oxygen feed.
A further object of the present invention is to propose humidity reactant gases of hydrogen and air/oxygen in modular proton exchange membrane fuel cells (PEMFC) in which the humidifier modules placed at reactant feed gases of Hydrogen and Air/ Oxygen maintained under hydrated condition by periodical spraying of water in the form atomization in line of fluid flow during which gases are humidified and excess water is retained in the high surface area available in the candle and humidification of gases continues further in absence of water spray by diffusion of water from the surface of candle to the gases passing over the candle surface area.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: Proton exchange membrane (PEM) fuel cell system with its subsystems.
Figure 2: Cross section of the humidifier candle assembled in the humidification
subsystem.
Figure 3: Schematic of candle humidifier subsystem
BRIEF DESCRIPTION OF THE INVENTION:
A subsystem for humidification of reactant gases, comprising a cylindrical candle consisting of multiple number of through holes over the candle length with high internal surface area, enclosed in a hollow metal/ polymer cylindrical pipe whose inner diameter and length is equal or higher than the candle diameter and length having means for reactant gas inlet and exit for the enclosed pipe, wherein the enclosed candle has means for integration of humidification chamber in which atomized spraying nozzle attachment is provided prior to the gas inlet of candle enclosure.

DETAILED DESCRIPTION OF THE INVENTION
According to the invention, the reactant gases of humidified hydrogen or air reactants are fed at the stack inlets of cathode (2) and anode (4) which is in-line with the fluid communication of the humidifier exit gases of hydrogen or air. In present case, the dry reactant gases of hydrogen or air (19) are passes through an expander (20) having higher diameter than the size of inlet gas (19) which is in fluid communication with the humidification chamber (21) wherein the dry gas is in contact with the atomized water pool (22) which generated by the nozzle (23) assembled in the humidifier chamber (21) which is connected to high pressure water line (24) it is being pressurized by the pressure pump (25) whose inlet is connected with water reservoir (13) of the fuel cell system. The amount of humidification is governed by the duration of nozzle (23) spraying time which is controlled by the controller (7) through its feed forward signals (17). In case of the excess water being carried away by the reactant gases would be absorbed in the cylindrical candle (26) having high surface area whose cross section (18) area is shown in Figure. 2. The candle is encapsulated in cylindrical hard wall tube (27) whose inner diameter is equivalent to the outer diameter of cylindrical candle. The length of candle (L) and diameter (D) are varied with reference to the stack capacity requirements.

The water absorbed over the surface of the candle over a length (L) would help in humidifying the reactants gases in absence of atomized water pool while the dry gas is interacting with the surface of the candle having multiple through holes from one end to the other end of the candle (26). Finally, the humidified dry reactant gas exits from the candle humidifier subsystem through its exit section (28) and same is fluid connection with the reactant feed inlet connection of air (2) and Hydrogen (4) of fuel cell stack (1).

WE CLAIM:
1. A subsystem for humidification of reactant gases, comprising a cylindrical candle consisting of multiple number of through holes over the candle length with high internal surface area, enclosed in a hollow metal/ polymer cylindrical pipe whose inner diameter and length is equal or higher than the candle diameter and length having means for reactant gas inlet and exit for the enclosed pipe, wherein the enclosed candle has means for integration of humidification chamber in which atomized spraying nozzle attachment is provided prior to the gas inlet of candle enclosure.
2. The subsystem as claimed in claim 1, wherein the humidification chamber is integrated with the pipe having variable cross section area whose inlet is provisioned to receive the feed of dry reactant gas of air/ oxygen or Hydrogen available from their respective feed reactant supply subsystem for supply of fluid flow.

3. The subsystem as claimed in claim 1, wherein the nozzle is in fluid communication with the high pressure water supply line, the water pressure being maintained by a pressure pump whose inlet is in fluid communication with the water reservoir including the fuel cell system controller.
4. The subsystem as claimed in claim 1, wherein the Controller controls the humidity requirements of reactant gas air/oxygen or Hydrogen which are supplied from its subsystems prior to be fed at the fuel cell stack inlets.