CBE Final questions with correct answers graded A+ 2023/2024

CBE Final The heat conduction equation in a medium is given in the simplest form as: ∂^2T ∂^2T =0 ∂x^2 + ∂y^2 where the parameters have their usual meaning. Which of the following statements is incorrect - correct answer Thermal conductivity is negligible If force, length, and time are selected as the three fundamental dimensions, the units of viscosity in the SI system could be written as - correct answer kg/m*s The thermal conductivity of a substance may be defined as the rate of heat transfer per unit length per unit temperature difference. The primary dimensions of thermal conductivity in the M-L-T-theta-are: - correct answer ML/(T^3)Theta A fluid flows through a truncated conical pipe at steady-state and constant density. The radius at the outlet is half the radius of the inlet. The velocity of the fluid exiting is ___________ the velocity of the fluid entering. - correct answer 4 times greater Which of the following are correct units for heat transfer coefficient? - correct answer kg/(s^3)(K) In a counter-flow heat exchanger, 2 kg/s of hot water flows through the tubes and 8 kg/s of cold water flows on the shell side. Which flow will experience the lowest temperature change? - correct answer Cold Water Water flows through a tube of length L with a mean inlet temperature (Ti). The tube is held at a uniform surface temperature (Ts) greater than Ti. Which temperature profile best represents the mean temperature of the water as if flows through the tube? - correct answer increases sharply then plateus A Newtonian fluid flows under steady, laminar conditions through a circular pipe of diameter 0.16 m at a volumetric rate of 0.05 m 3 /s. Under these conditions, the maximum velocity (in m/s) at a section is most nearly - correct answer 5 Q=VavA Vav pipe=1/2Vmax Vav plate= - correct answer 2/3Vmax Water flows with a velocity of 3 m/s in an 80-cm diameter sewer pipe at a depth of 30 cm. The flow rate is nearest (take 1L=1000 cm3 ): - correct answer 516 L/s Water is placed between two parallel plates. The bottom plate moves to the right at constant velocity V and the top plate is stationary. The water velocity profile shown below is observed at steady-state conditions (you are looking at a side-view of the plates and the water between the plates). Ignoring edge effects in this flow system, water moves in the x-direction only and therefore has only x-momentum. In which direction is the x-momentum being transferred? - correct answer Transfer is in the +y direction (upward in the figure) because momentum is transported from a region of high momentum (near bottom plate) to low momentum (near top plate With increase in the shear rate, the apparent viscosity of dilatant fluids _______ - correct answer increases bingham -viscocity same The velocity profile in a 4-cm-diameter pipe transporting 20 °C water is given by v(r)=10(1- 2500r^2) m/s. If the viscosity of the water is 1 mPa·s and the density is 997 kg/m3 , the shearing stress at the wall is nearest: - correct answer 1 Pa