A plastics plant manufactures larges pieces of plastic by continuously extruding thin sheets. As the sheets flow out of the extruder, they are cooled via forced convection and radiation. The plastic sheets are 1 mm thick, 1 m wide, and leave the extruder at a rate of 9 m/min. A fan blows air over the top and bottom surface of the sheet during the first meter after the sheet leaves the extruder. The fan accelerates the air to 3 m/s and the air is known to be at 27°C at the fan outlet. At the exit of the extruder, the plastic is at 90°C. The plastic is estimated to have an emissivity of ? = 0.9 and the general surroundings are at 20°C. A) Determine the rate of heat transfer via convection and radiation from the 1-m-long section of the plastic sheet that is being force cooled. take the surface temperature to be 90°C over the entire section of interest. B) The density-specific heat product of the plastic is ?? = 1920 kJ m3– K⁄ . What is the temperature of the plastic at the end of the cooling section
A plastics plant manufactures larges pieces of plastic by continuously extruding thin sheets. As the sheets flow out of the extruder, they are cooled via forced convection and radiation. The plastic sheets are 1 mm thick, 1 m wide, and leave the extruder at a rate of 9 m/min. A fan blows air over the top and bottom surface of the sheet during the first meter after the sheet leaves the extruder. The fan accelerates the air to 3 m/s and the air is known to be at 27°C at the fan outlet. At the exit of the extruder, the plastic is at 90°C. The plastic is estimated to have an emissivity of ? = 0.9 and the general surroundings are at 20°C. A) Determine the rate of heat transfer via convection and radiation from the 1-m-long section of the plastic sheet that is being force cooled. take the surface temperature to be 90°C over the entire section of interest. B) The density-specific heat product of the plastic is ?? = 1920 kJ m3– K⁄ . What is the temperature of the plastic at the end of the cooling section
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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Question
A plastics plant manufactures larges pieces of plastic by continuously extruding thin sheets.
As the sheets flow out of the extruder, they are cooled via forced convection and radiation.
The plastic sheets are 1 mm thick, 1 m wide, and leave the extruder at a rate of 9 m/min.
A fan blows air over the top and bottom surface of the sheet during the first meter after the
sheet leaves the extruder. The fan accelerates the air to 3 m/s and the air is known to be at
27°C at the fan outlet. At the exit of the extruder, the plastic is at 90°C. The plastic is
estimated to have an emissivity of ? = 0.9 and the general surroundings are at 20°C.
A) Determine the rate of heat transfer via convection and radiation from the 1-m-long
section of the plastic sheet that is being force cooled. take the surface temperature to be 90°C over
the entire section of interest.
B) The density-specific heat product of the plastic is ?? = 1920 kJ m3– K⁄ . What is the
temperature of the plastic at the end of the cooling section
Transcribed Image Text:90°C
Air
27°C, 3 m/s
-1 m
Plastic sheet
1 mm
1m
9 m/min
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VIEWStep 2: Determine the mean tempearture and write the air properties at the mean temperature:
VIEWStep 3: Determine the Nusselt number to calculate the convection heat transfer coefficient associated:
VIEWStep 4: Calculate the rate of heat transfer through convection and radiation:
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