Analytical Modeling of Hydrogen–Air Mixture in a Catalytic Microchannel

Abstract

In the present study, the surface catalytic reaction in a microchannel with nonreactive hydrogen-air flow is investigated. Here, the microchannel wall is coated with a catalyst. A solution to the catalytic microchannel flow is gained by applying an iterative method to solve the energy, mole fraction, and catalytic reaction equations. To validate the model, the results of fuel conversion are compared with the results of experimental studies available in the literature, and a good agreement between them is achieved. Moreover, the results show that increasing the hydraulic diameter of the microchannel decreases normalized temperature of the mixture and catalyst heat transfer. Steeper variations are observed in the case of d h ∕L < 0.2. Furthermore, when the wall-to-inlet-temperature ratio is smaller than 2.5, the fuel conversion is very small; and for T W ∕T i > 3.5, the fuel is fully converted.rate constant of catalytic reaction, m · s −1 L = channel length, m M = molecular weight of species _ m = mass flow rate, kg · s −1 Nu = Nusselt number; hd h ∕k P = static pressure, atm Pe = Péclet number; υd h ∕α Pr = Prandtl number; υ∕α Pe m = mass Péclet number; υd h ∕D AB p = wetted perimeter of microchannel, m Q = catalyst heat transfer to flow, W Q = normalized catalyst heat transfer R = gas constant, J · kg −1 K −1 Re = Reynolds number; vd h ∕υ S = ratio of convection mass transfer to reaction rate Sc = Schmidt number; υ∕D AB Sh = Sherwood number; h m d h ∕D AB S = normalized sensitivity analysis parameter T = temperature, K v = flow velocity, m · s −1 W C = rate of fuel consumption, mole · m −2 s −1 X = axial location, m X = normalized axial location Y = bulk mole fraction of fuel Y = mole fraction of fuel θ = normalized temperature μ = dynamic viscosity, ns · m −1 υ = diffusion volumes of samples; Eq. (11) ρ = density, kg · m −3 Φ = model response parameter Subscripts c = conversion, catalytic reaction i = inlet, samples m = mass S = surface W = wall 0 = nominal value

Experimental Research on Flow and Heat Transfer in Microchannel with Refrigerant HFO1234yf

“…In microchannel problems, investigations of fluid-solid interactions and surface effects are very important. Esfhani and Fanaee [21] and Fanaee [22] studied the catalytic reaction of hydrogen and oxygen in microchannels, where the inner wall of the microchannels is covered with catalyst, and the results showed that increasing the hydraulic diameter of the microchannel will decrease the normalized temperature of the mixture and catalyst heat transfer.…”