Answer:
ºC
Explanation:
First, let's write the energy balance over the duct:
It says that the energy that goes out from the duct (which is in enthalpy of the mass flow) must be equals to the energy that enters in the same way plus the heat that is added to the air. Decompose the enthalpies to the mass flow and specific enthalpies:
The enthalpy change can be calculated as Cp multiplied by the difference of temperature because it is supposed that the pressure drop is not significant.
So, let's isolate 
:
The Cp of the air at 27ºC is 1007
(Taken from Keenan, Chao, Keyes, “Gas Tables”, Wiley, 1985.); and the only two unknown are and Q.
Q can be found knowing that the heat flux is 600W/m2, which is a rate of heat to transfer area; so if we know the transfer area, we could know the heat added.
The heat transfer area is the inner surface area of the duct, which can be found as the perimeter of the cross section multiplied by the length of the duct:
Perimeter:
Surface area:
Then, the heat Q is:
Finally, find the exit temperature:
=27.0000077 ºC
The temperature change so little because:
- The mass flow is so big compared to the heat flux.
- The transfer area is so little, a bigger length would be required.
Kinetic energy:
*the energy of a moving body*
rising water vapor.
the wings of flying hummingbird.
rolling marble.
Potential energy:
*the energy that is stored in a body so that any small change in position or state of the body, will result in this body movement by transforming all this potential energy into kinetic energy*
stone resting.
disconnected battery (the potential energy is what called voltage here)
stretched rubber band.
Hope this helps.
Answer: copper
Explanation: when a spoon is placed in a hot coffee, the coffee will cool off based on the concept of heat transfer.
The coffee is at a higher temperature compared to the spoon, hence there is conduction of heat by the spoon from the coffee.
Heat is now transfered from the coffee to the spoon, the rate of heat transfer ( for this case coffee to spoon) is dependent on some properties but for this case, the thermal conductivity is of the most important.
A material of high thermal conductivity have a very fast rate of heat transfer and a material of low thermal conductivity have a slow rate of heat transfer.
Below is the value of thermal conductivity for copper, aluminum, iron and glass.
Copper (385 w/m.K)
Aluminum (205 W/m.K)
Iron (79.5 W/m.K)
Glass (0.8 W/m.K)
It can been seen that copper has the highest value for thermal conductivity which implies that it will conduct heat faster compared to others thus cooling the coffee faster.
A.) kiloliter. 1 kiloliter = 1,000 liters
c.) megaliter. 1 megaliter = 1,000,000 liters
hope this helps
