Required information Heat dissipated from an engine in operation can cause hot spots on its surface. If the outer surface of an engine is situated in a place where oil leakage is possible, then when leaked oil comes in contact with hot spots above the oil's autoignition temperature, it can ignite spontaneously. Consider an engine cover that is made of a stainless-steel plate with a thickness of 1 cm and a thermal conductivity of 14 W/m.K. The stainless-steel plate is covered with a 5-mm-thick insulation (k= 0.5 W/m-K). The inner surface of the engine cover is exposed to hot air at 350°C with a convection heat transfer coefficient of 5 W/m².K as shown in the figure. The 2-m-long engine outer surface is cooled by air blowing in parallel over it at 7 m/s in an environment where the ambient air is at 60°C. To prevent fire hazard in the event of oil leak on the engine cover, the engine cover surface should be kept below 180°C. It has been determined that the 5- mm-thick insulation layer is not sufficient to keep the engine cover surface below 180°C. To solve this problem, one of the plant supervisors suggested adjusting the blower capacity to provide an increase in the cooling air velocity by 10%. Airflow 60°C Yes Engine cover 350°C Insulation Another method that could be explored to keep the engine outer surface temperature below the fire hazard limit of 180°C is to increase the insulation thickness. Increase the insulation thickness by threefold and verify if this method would keep the temperature below the required limit for the safe operation of the engine. Compare the effectiveness of this method with the previous method. It is given that the properties of air at 120°C are k = 0.03235 W/m-K, v= 2.522 x 10-5 m²/s, and Pr = 0.7073 (Table A-15). The surface temperature is 152.56 °C. the suggested method is a viable method. By comparison the effectiveness of this method is more than the previous method.
Required information Heat dissipated from an engine in operation can cause hot spots on its surface. If the outer surface of an engine is situated in a place where oil leakage is possible, then when leaked oil comes in contact with hot spots above the oil's autoignition temperature, it can ignite spontaneously. Consider an engine cover that is made of a stainless-steel plate with a thickness of 1 cm and a thermal conductivity of 14 W/m.K. The stainless-steel plate is covered with a 5-mm-thick insulation (k= 0.5 W/m-K). The inner surface of the engine cover is exposed to hot air at 350°C with a convection heat transfer coefficient of 5 W/m².K as shown in the figure. The 2-m-long engine outer surface is cooled by air blowing in parallel over it at 7 m/s in an environment where the ambient air is at 60°C. To prevent fire hazard in the event of oil leak on the engine cover, the engine cover surface should be kept below 180°C. It has been determined that the 5- mm-thick insulation layer is not sufficient to keep the engine cover surface below 180°C. To solve this problem, one of the plant supervisors suggested adjusting the blower capacity to provide an increase in the cooling air velocity by 10%. Airflow 60°C Yes Engine cover 350°C Insulation Another method that could be explored to keep the engine outer surface temperature below the fire hazard limit of 180°C is to increase the insulation thickness. Increase the insulation thickness by threefold and verify if this method would keep the temperature below the required limit for the safe operation of the engine. Compare the effectiveness of this method with the previous method. It is given that the properties of air at 120°C are k = 0.03235 W/m-K, v= 2.522 x 10-5 m²/s, and Pr = 0.7073 (Table A-15). The surface temperature is 152.56 °C. the suggested method is a viable method. By comparison the effectiveness of this method is more than the previous method.
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
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Transcribed Image Text:Required information
Heat dissipated from an engine in operation can cause hot spots on its surface. If the outer surface of an
engine is situated in a place where oil leakage is possible, then when leaked oil comes in contact with
hot spots above the oil's autoignition temperature, it can ignite spontaneously. Consider an engine cover
that is made of a stainless-steel plate with a thickness of 1 cm and a thermal conductivity of 14 W/m.K. The
stainless-steel plate is covered with a 5-mm-thick insulation (k=0.5 W/m.K). The inner surface of the
engine cover is exposed to hot air at 350°C with a convection heat transfer coefficient of 5 W/m².K as
shown in the figure. The 2-m-long engine outer surface is cooled by air blowing in parallel over it at 7 m/s
in an environment where the ambient air is at 60°C. To prevent fire hazard in the event of oil leak on the
engine cover, the engine cover surface should be kept below 180°C. It has been determined that the 5-
mm-thick insulation layer is not sufficient to keep the engine cover surface below 180°C. To solve this
problem, one of the plant supervisors suggested adjusting the blower capacity to provide an increase in
the cooling air velocity by 10%.
Airflow
60°C
Yes
Engine cover
350°C
Insulation
Another method that could be explored to keep the engine outer surface temperature below the fire hazard limit of 180°C is
to increase the insulation thickness. Increase the insulation thickness by threefold and verify if this method would keep the
temperature below the required limit for the safe operation of the engine. Compare the effectiveness of this method with
the previous method. It is given that the properties of air at 120°C are k = 0.03235 W/m-K, v= 2.522 x 10-5 m²/s, and Pr=
0.7073 (Table A-15).
The surface temperature is 152.56
°C.
, the suggested method is
a viable method.
By comparison the effectiveness of this method is more than the previous method.
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