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\"font-family:TimesTenLTStd;\">Figure P4.86 provides steady-state operating data

ID: 1858673 • Letter: #

Question

"font-family:TimesTenLTStd;">Figure P4.86 provides steady-state

operating data for a

"font-family:TimesTenLTStd;font-style:italic;">parallel flow

heat exchanger in which

there are separate streams of air and carbon dioxide

(CO

"font-family:TimesTenLTStd;vertical-align:-2pt;">2

).

Stray heat transfer with the surroundings of the heat exchanger and

kinetic and potential energy effects can be ignored. The ideal gas

model applies to each gas. A constraint on heat exchanger size

requires the temperature of the exiting air to be 20 degrees

greater than the temperature of the exiting CO

"font-family:TimesTenLTStd;vertical-align:-2pt;">2

.

Determine the exit temperature of each stream, in

degrees

"font-family:TimesTenLTStd;">R.

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alt="media/c9b/c9b4cdac-dbfd-4b26-8b82-84" />

"font-family:TimesTenLTStd;">

Explanation / Answer

specific heat capacity for air = 1.04 KJ/Kg-K

specific heat capacity for CO2 = 0.85 KJ/Kg-K

convert all the temperature to Kelvin scale

energy must be conserved

m*C*(dT) air = m*c*(dT) CO2

50*1.04*(577.78-T2-11.11) = 73.7*0.85*(T2-311.11)

T2 = 427.04K = 768.67 R