A handle on a cooking pot can be modeled as a rod fin with an adiabatic tip at the farthest section from the attachment points. For the handle shown in the sketch, determine the temperature distribution and the heat transfer through the handle if the pot surface is 190ºF, the surrounding air temperature is 90ºF, and the convective heat transfer coefficient is 160 Btu/hr?ft^2 ?ºF.
What will be an ideal response?
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Life on Earth remained single celled for ________ years, according to the microfossil record
Fill in the blank(s) with correct word
Intensity of Sound: What is the intensity level in decibels of a sound with intensity 10-3 W/m2? The threshold of human hearing is 1.0 × 10-12 W/m2.
A. 30 dB B. 60 dB C. 90 dB D. 96 dB
Consider the electrical space heater, where the electric resistance heating coil is enclosed in a straight horizontal polished metallic cylinder that has an outer diameter of 1 cm and an emissivity of 0.9. If its surface temperature is at 110°C and the room air temperature is at 20°C, calculate the total heat loss per unit length of the cylinder due to both convection and radiation. For the purpose of this calculation, assume that the reflector is so designed that it “collects” all of the radiant heat from the back half of the horizontal heater and that it reflects 95% of the incident radiation.
GIVEN
• An electric resistance heating coil enclosed in horizontal metallic cylinder.
• Emissivity (?) = 0.9
• Diameter of cylinder (D) = 1 cm= 0.01 m
• Surface temperature (Ts) = 110°C= 383 K
• Ambient air temperature (T?) = 20°C= 293 K
• Reflects 95% of incident radiation.
FIND
Total heat loss per unit length of cylinder due to convection and radiation.
ASSUMPTIONS
• Air is still
• Surface temperature is uniform and constant
PROPERTIES AND CONSTANTS
for dry air at the mean temperature of 65°C
Thermal expansion coefficient (?) = 0.00296 1/K
Thermal conductivity (k) = 0.02825 W/(m K)
Kinematic viscosity (?) = 19.92 × 10–6 m2/s
Prandtl number (Pr) = 0.71
Why do scientists say that evolution is a "theory"?
A) because it explains a great deal about life and is supported by an enormous body of evidence B) because they are not very confident that it really happened C) because it's really just a guess about how life developed on Earth D) because it is supported by only a small amount of evidence