Air (C p = 1.005 kJ/kg times degrees C) is to bepreheated by hot exhaust gases i

Question

Air (Cp = 1.005 kJ/kg times degrees C) is to bepreheated by hot exhaust gases in a cross-flow heat exchangerbefore it enters the furnace. Air enters the heat exchanger at 95kPa and 20 degrees C at a rate of 0.8 cubic meters persecond. The combustion gases (Cp = 1.10 kJ/kg timesdegrees C) enter at a rate of 1.1 kilograms per second at180 degrees C and leave at 95 degrees C. Determine the rate of heattransfer to the air and it's outlet temperature. Please show all steps. This is a lifesaver question. Thank you. Air (Cp = 1.005 kJ/kg times degrees C) is to bepreheated by hot exhaust gases in a cross-flow heat exchangerbefore it enters the furnace. Air enters the heat exchanger at 95kPa and 20 degrees C at a rate of 0.8 cubic meters persecond. The combustion gases (Cp = 1.10 kJ/kg timesdegrees C) enter at a rate of 1.1 kilograms per second at180 degrees C and leave at 95 degrees C. Determine the rate of heattransfer to the air and it's outlet temperature. Please show all steps. This is a lifesaver question. Thank you.

Explanation / Answer

Hi,you should be able to understand the rate oh heattransfer homework problem you are asking about by followingthe steps below: mass flow rate of airma=P1V1/RT1                                      =95*0.8/0.287*293                                     =0.903kg/s rate of heat transfer to the air is equal to the amount ofheat loss by combustion gases Qa=mgcpg(T1g-T2g)      =1.1*1.1(180-95) Qa=102.85kW air outlet temperature T2a is macpa(T2a-T1a)=102.85 0.903*1.005(T2a-20)=102.85 T2a=133.330C                                      =95*0.8/0.287*293                                     =0.903kg/s rate of heat transfer to the air is equal to the amount ofheat loss by combustion gases Qa=mgcpg(T1g-T2g)      =1.1*1.1(180-95) Qa=102.85kW air outlet temperature T2a is macpa(T2a-T1a)=102.85 0.903*1.005(T2a-20)=102.85 T2a=133.330C I hope this helps best of luck with rest of your coursework I hope this helps best of luck with rest of your coursework

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