Circular fins are employed around the cylinder of a lawn mower engine to dissipate heat. The fins are made of aluminum are 0.3-m
thick, and extend 2 cm from base to tip. The outside diameter of the engine cylinder is 0.3 m. Design operating conditions are Tai 30°C and h-12 Wm2.K. The maximum allowable cylinder temperature is 300°C. Estimate the amount of heat transfer from a single fin. How many fins are required to cool a 3-kw engine operating at 30% thermal efficiency, if 50% of the total heat given off is transferred by the fins?
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Answer:
oxygen deficit = 3.851 mg/L
Explanation:
given data
flow rate of the river= 165 × gal/d
saturation value of dissolved oxygen = 9.17 mg/L
to find out
oxygen deficit he two flows
solution
we will apply here formula for dissolved oxygen content after dilution is
Do mix = ..........................1
here Qw is rate of flow of waste water i.e 26 × gal/d
(Do)w is Do of waste waster i.e 1 mg/L
Qr is aret of flow of river i.e 165 × gal/d
(Do)r is do of river water i.e 6 mg/L
so put all value in equation 1 we get
Do mix =
solve we get
Do mix = 5.319 mg/L
so
oxygen deficit = saturation oxygen - (Do) mix ..............2
oxygen deficit = 9.17 - 5.319
oxygen deficit = 3.851 mg/L