- #1

KevinO

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**the question states exactly:**

Air passes over an electric heater at a steady rate of 2500 cubic centimeters per second. the steady inlet flow temperature of the air is 20 degree celcius and the steady outlet temperature is 40 degree celcius.

part a. what is the heat absorbed by the air passsing over the heater in 2 hours

part b. obtain an estimate power rating of the heater. is this too high or too low? explain.

[density of air = 1.2kg/cm^3; specific heat capacity of air= 1000Jkgcm^-3]

Air passes over an electric heater at a steady rate of 2500 cubic centimeters per second. the steady inlet flow temperature of the air is 20 degree celcius and the steady outlet temperature is 40 degree celcius.

part a. what is the heat absorbed by the air passsing over the heater in 2 hours

part b. obtain an estimate power rating of the heater. is this too high or too low? explain.

[density of air = 1.2kg/cm^3; specific heat capacity of air= 1000Jkgcm^-3]

the equations i used were P=E/t; E=mcΔθ; ρ=m/V

for part a: After some substitutions i said P= (ρVcΔθ)/(t) where V/t = 2500cm^3s^-1

then i multiply my answer from that by 7200seconds and said that was the heat absorbed.

for part b: i just took the answer from P= (ρVcΔθ)/(t) and said that was the estimated power rating. my answers were P= 60MW and E=4.32 × 10^11 J

the text however says the answer was P= 60W and E=4.32×10^5 J. i assumed my answer was correct and the book had a mistake. when i showed my teacher however she said it was wrong to try again but i stuck.