1. If we desire a fast response from a thermocouple to measure temperature, which of the following should we do?
a) Make the thermocouple junction large
b) Make the thermocouple junction small
c) Use a heavier metal alloy
d) Use a metal alloy with large heat capacity
2. A fluid with a very small Prandtl number (Pr <<1) flows over a flat plate. Which of the following diagrams is the best representation of the velocity boundary layer (δ) and the thermal boundary layer (θ) developing from the leading edge?
(a)
(b)
(c)
(d)
3. The thermal boundary layer of a fluid over a flat plate is shown in the diagram. Ta, Tb, and Tc are the fluid temperatures at the boundary layer edge at three locations along the plate. What can be said about the relationship of the temperatures?
T1 = 25°C
Outer edge
(a) Ta > Tb > Tc
(b) Ta = Tb = Tc
(c) Ta < Tb < Tc
(d) None of the above is correct.
T2 = 100°C
4. A fluid at T flows over a flat plate at Ts. The thermal boundary layer grows from the leading edge, which is shown in the diagram to the right. What can be said about the local heat transfer coefficient hx at four different locations labeled A), B), C), and D)?
(a) The value of hx at the location A) is the largest.
(b) The value of hx at the location D) is the largest.
(c) The values of hx for all the four locations are the same.
(d) None of the above is correct.
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5. Consider Flow 1 and Flow 2 of the same fluid over diamond-shaped objects. The only differences between the two flows are the flow velocity and the object size, i.e. Flow 1 has a velocity twice that of Flow 2, but half of the characteristic length. Which of the following statements are true about these two flows?
(a) The Nusselt number for Flow 1 is twice that for Flow 2.
(b) The averaged heat transfer coefficient for Flow 1 is twice that for Flow 2.
(c) The Nusselt numbers for the two flows are the same.
(d) The averaged heat transfer coefficients h for the two flows are the same.
6. Generally speaking, what can be said about turbulent flow vs. laminar flow for a convection heat transfer process?
(a) Turbulent flow provides a higher convection heat transfer coefficient.
(b) Turbulent flow provides a lower convection heat transfer coefficient.
(c) Turbulent flow generally provides the same convection heat transfer coefficient as laminar flow.
(d) None of the above is correct.
