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HWextracombustion-336 - ME 336 EXTRA EXAMPLES 14.49 In a...

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ME 336 EXTRA EXAMPLES 14.49 In a new high-efficiency furnace, natural gas, assumed to be 90% methane and 10% ethane (by volume) and 110% theoretical air each enter at 25 ° C, 100 kPa, and the products (assumed to be 100% gaseous) exit the furnace at 40 ° C, 100 kPa. What is the heat transfer for this process? Compare this to an older furnace where the products exit at 250 ° C, 100 kPa. Products 40 C 100 kPa 110 % Air 25 C, 100 kPa 0.9 CH + 0.1 C H 25 C, 100 kPa 4 2 2 Heat transfer 0.9 CH 4 + 0.1 C 2 H 6 + 1.1 × 2.15 O 2 + 3.76 × 2.365 N 2 1.1 CO 2 + 2.1 H 2 O + 0.215 O 2 + 8.892 N 2 Fuel values from table A.10 and the rest from Table A.9 H R = 0.9(-74 873) + 0.1(-84 740) = -75860 kJ/kmol fuel H P = 1.1(-393 522 + 562) + 2.1(-241 826 + 504) + 0.215(441) + 8.892(437) = -935 052 kJ/kmol fuel assuming all gas Q CV = H P - H R = -859 192 kJ/kmol fuel b) T P = 250 o C H P = 1.1(-393 522 + 9346) + 2.1(-241 826 + 7740) + 0.215(6808) + 8.892(6597) = -854 050 kJ Q CV = H P - H R = -778 190 kJ/kmol fuel
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