Consider hydrogen-oxygen fuel cell operating at 80 degree C and with a rated pow

Question

Consider hydrogen-oxygen fuel cell operating at 80 degree C and with a rated power output of 80 kW. Assume cell efficiency of 50%, E_r = 1.18 V and E_tn = 1.47 V. Calculate a. the mass flow rate of hydrogen consumption b. the mass flow rate of oxygen consumption c. the mass flow rate of air supply if oxygen is supplied as air d. the mass flow rate of hydrogen supply rate, if the hydrogen fuel utilization coefficient is 60% e. Water mass production rate f. The mass and volume of water produced in 1 hr of operation of the fuel cell g. The rate of heat generation.

Explanation / Answer

Given that -

T = 80 deg C, Prated = 80 kW, Cell efficiency, eta = 50%, Er = 1.18 V, Etn = 1.47 V.

(a) Mass flow rate of hydrogen consumption = 1.05x10^-8 x Pr/Er = 1.05x10^-8 x 80x1000/1.18

= 7.11 x 10^-4 kg/s

(b) Flow rate of oxygen consumption = 8.29x10^-8 x Pr/Er = 5.61 x 10^-6 kg/s

(c) Mass flow rate of air supply if oxygen is supplied as air = 3.57 x 10^-7 x Pr/Er = 2.42 x 10^-5 Kg/s

(d) Hydrogen supply rate:

Here, eta (fuel) = 1 / lemda(fuel)

=> 0.60 = 1 / lemda(fuel)

=> lemda(fuel) = 1/0.60 = 1.66

Again, H2 usage = 1.05 x 10^-8 x lemda(fuel)xPr/Er = 1.18 x 10^-3 kg/s

(e) Water mass production rate = 9.34x10^-8 x Pr/Er = 6.33 x 10^-6 kg/s

(f) Mass of water produced in 1 hour = (9.34x10^-8 x Pr/Er) x 60x60 = 0.022 kg

(g) Rate of heat generation = Pr (1.25/Er - 1)

= 80X1000x(1.25/1.18 - 1) = 4745.76 Watt.

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