# Fuel Cells

928 Words 4 Pages
Polarization curve Fuel cell creates 1.16 V of equilibrium potential between hydrogen and oxygen. However, the actual open circuit voltage is around 1 V due to temperature, pressure, and the concentration of the reactant. The ohmic loss is the resistance loss induced by the unique resistances of the component of fuel cell. And the concentration loss occurs when reaction rates of hydrogen and oxygen are faster than their supply rates. (1) The diffusion flux created according to this linear concentration gradient in the steady-state balances accurately in the catalyst layer. (2) Here, j is the current density in the fuel cell and is the diffusion flux …show more content…
In order to obtain the flow distribution in fuel cells, the following assumptions are applied to establish a flow network model. 1) The reactant ges in consid to be steady flow in impervious channels and the temperature is uniform. 2) A fluid network is comprised of straight pipe, intake, exhaust duct and T-shape connection. 3) The influence of inertia is ultralow in contrast to the viscosity due to the low Reynolds number. Furthermore, in the straight pipe, a fully developed laminar assumption is satisfied under the condition that shape change is negligible. Numerical analysis technique the numerical analysis is performed by combining the governing equations related to the conservation of energy, conservation of mass and conservation of electrical charge to examine fluid distributions, heat transfers, mass transfers and electrochemical reactions. The assumptions used in developing the model are as follow: 1) Ideal gas law was employed for gaseous species. 2) The fluid flow in the fuel cell was laminar due to the low flow velocities and the small size of gas flow …show more content…
Therefore, the following equation is shown when the Darcy equation allowing viscous resistance for the porous structure is applied to the NaviereStoke equation for the steady-state. (5) (6)
In Eq. (6), ε is the porosity of the gas diffusion layers and K is the permeability of the gas diffusion layers. u is the surface velocity of the gas diffusion layer.
3.3. Conditions for single-cell numerical analysis Numerical analysis for a single-cell was ﬁrst performed before the ﬂow ﬁeld was analyzed to evaluate the effects of the waveform shape. The results were compared to the references. The sizes of the channel were calculated from the straight sections of the 25 unit cell channel. The width of the cathode was 0.5 mm and its length was 1 mm. The width of anode was 0.5 mm and its length was 0.6 mm. The ribs were structured every 0.5 mm on both sides of the channels. The thickness of the gas diffusion layers was 0.2 mm, that of the catalyst layers was 0.2 mm and that of the membranes was 0.05 mm.
Table 1- Physical Parameters in a PEMFC model.
Parameter Expression
Channel height 1 mm, 1.5 mm, 2 mm
Channel width 5

• ## Principle Components Of Rankine Cycle

In the Carnot cycle all the heat transfer is at constant temperature, and therefore the vapor is superheated in process 3–3. Note, however, that during this process the pressure is dropping, which means that the heat must be transferred to the vapor as it undergoes an expansion process in which work is done. This heat transfer is also very difficult to achieve in practice. Thus, the Rankine cycle is the ideal cycle that can be approximated in practice. In the following sections, we will consider some variations on the Rankine cycle that enable it to approach more closely the efficiency of the Carnot…

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• ## Heat Release Rate Model

The gross heat release rate is synthesized with an equation (3) having two separate Wiebe efficiency factors ap and ad in the two Wiebe functions often referred to as double Wiebe function [25, 33]. The direct experimental measurement of heat release rate is difficult. Therefore, a net apparent heat release rate calculated from the experimentally measured pressure-time profile and computationally calculated piston displacement profile along with heat loss to the cylinder wall using equation (1) is applied for validation. The diesel and DME oxidation reaction equations assuming complete…

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• ## The Effect Of The Fluidized Bed Model: Model Equations

4.1.2. Model Equations 4.1.2.1. Mass and Energy Balances on Solids The moisture content of solids is a function of time only due to perfect mixing and negligible diffusion resistance as stated in assumptions 1 and 2. Following assumption 3, air at the solid-air interface is saturated. The driving force of mass transfer is the difference between the vapor pressure of water vapor at the interface temperature and the partial pressure of water vapor in the air bulk at the bulk temperature.…

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• ## Fick's First Law Of Diffusion And The Penetration Of Polymers

(2.26) When, , , then the above equation can be rewritten as and when p1 = 1 atm (2.27) Where, c1 is the concentration in the sample when the equilibrium is reached. The solubility S is expressed in cm3 of gas at STP per cm3 of the solid at a pressure of 1 atm. (cm3 STP/cm3 atm). Equation (permeability) obeys Henry’s law when S is independent of p (Mangaraj et al., 2009). Effect of temperature on permeability The permeability of the packaging films with respect to oxygen and carbon dioxide is temperature dependent and its dependence is usually described by an exponential equation, i.e.…

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• ## Disadvantages Of Syngas

The transfer of oxygen through the membrane was modelled with the aid of user defined functions (UDF). Synthetic gas in addition to CO2, which serves as diluent, is used as sweep gas in the oxygen transport reactor. CO2 is used as the diluent as it is proved to be very effective in syngas combustion . The simulations were performed under laminar, steady state conditions considering Newtonian working fluids. Mass flow inlet conditions have been specified at feed and permeate sides while pressure outlet boundary conditions are specified at the exit sections of the feed and sweep sides.…

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• ## Enthalpy Lab Report

Temperature was measured during the reaction, allowing the amount of heat absorbed by the solution and the calorimeter to be measured. When added together, those values the enthalpy of the reaction. If the system loses no heat, this equation is true: “q_rxn=-q_soln-q_cal” (French et al, 105). This equation is equal to this one: “q_rxn=-m_soln s∆T-C_cal ∆T” (French et al, 105). For this reaction, s will be the specific heat of water because the experiment involves aqueous solutions.…

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• ## Molar Volume Of Gas Lab Report

This ideal gas law is essential to the lab as it explains the relationships between the different measurements of a gas and reduces into the combined gas law. The combined gas law is a relation where the number of moles of gas is constant, thus leaving the variables of pressure, volume, and temperature. When comparing the same substance under different conditions, the combined gas law can be mathematically written as (P"1" V"1" )/T"1" = (P"2" V"2" )/T"2" . Since the conditions of the experiment were not at standard temperature and pressure, the combined gas law is required in order to calculate the corresponding volume of hydrogen gas at STP. Single displacement reactions were also…

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• ## Lab Report: Moolar Volume Of A Gas At STP

Dalton’s Law was relevant in this experiment because it can be used to find the partial pressure exerted by the hydrogen by itself. It was hypothesized that if a gas is created through the reaction Mg + HCl → MgCl2 + H2 at a constant pressure and temperature, then the molar volume can be found out using gas laws because gases have direct and indirect relationships that can be used to find the unknown characteristic of said…

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• ## Slip Phenomenon In Couette Flow

The results can well predict the fluid flow behaviors on a solid substrate, but has to be proved by experiment. PACS: 23.40.-s, 21.60.Cs, 23.40.Hc, 27.40.+z The “no-slip” boundary condition, i.e., zero…

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• ## Compare And Contrast The Determination Of The Crystal Structure Of M3 (Xo4) 2

Hence, as a result, we can conclude that the lower the crystal symmetry of a crystal structure is, the higher the proton transport efficiency. This increase in proton transport efficiency results in more efficient conversions from chemical energy to electric energy. This technology can be implemented in a fuel cell. No extra energy needs to be wasted in assisting in the breaking and reformation of hydrogen bonds in the Cs3H(SeO4)2 crystal. This makes Phase II of the entire process sit in a suitable temperature range for a fuel cell to conduct electricity efficiently.…

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