Heat Transfer HW8a

1. Award: 2.43 out of 2.56 points You received credit for this question in a previous attempt 2. Award: 2.43 out of 2.56 points You received credit for this question in a previous attempt 3. Award: 2.43 out of 2.56 points Which fluid at room temperature requires a larger pump to move at a specified velocity in a given tube? Water Castor oil Coconut oil Engine oil Engine oil requires a larger pump because of its much larger density. Hint #1 References Multiple Choice Difficulty: Easy Previous attempt In fluid flow, which of the following is convenient to work with? V initial , T final V final , T initial V avg , T m V avg, T final In fluid flow, it is convenient to work with an average or mean velocity V avg and an average or mean temperature T m which remain constant in incompressible flow when the cross-sectional area of the tube is constant. Hint #1 References Multiple Choice Difficulty: Easy Previous attempt The V avg and T m represent the velocity and temperature, respectively, at a cross section if all the particles were at the same velocity and different temperature. True False The V avg and T m represent the velocity and temperature, respectively, at a cross section if all the particles were at the same velocity and temperature. References True / False Difficulty: Easy Previous attempt    ✓    ✓    ✓  Hints Hints

4. Award: 2.43 out of 2.56 points You received credit for this question in a previous attempt 5. Award: 2.43 out of 2.56 points You received credit for this question in a previous attempt Given are the values of Reynolds number Re of various flows. Identify the flow which is turbulent. Re = 2100 Re = 1100 Re = 3990 Re = 4010 Flow in a smooth pipe is turbulent when the Reynolds number is above 4000. Hint #1 References Multiple Choice Difficulty: Easy Previous attempt Define hydraulic diameter. References Section Break Difficulty: Easy The hydraulic diameter is defined such that it reduces to ordinary diameter D for non-circular tubes. True False The hydraulic diameter is defined such that it reduces to ordinary diameter D for circular tubes since Nu = hD h k = 0.023Re 0.8 Pr 0.4 . Hint #1 References True / False Difficulty: Easy Previous attempt    ✓   ✓  Hints Hints

6. Award: 2.43 out of 2.56 points You did not receive full credit for this question in a previous attempt 7. Award: 2.43 out of 2.56 points You received credit for this question in a previous attempt 8. Award: 2.43 out of 2.56 points You did not receive full credit for this question in a previous attempt How is hydraulic diameter defined in non-circular tubes? D h = 4 A c / p Hint #1 References Numeric Response Difficulty: Easy Previous attempt How is hydraulic diameter defined in non-circular tubes? D h = 4 A c / p Explanation: For flow-through non-circular tubes, the Reynolds number, as well as the Nusselt number and the friction factor, are based on the hydraulic diameter D h defined as D h = 4 A c / p , where A c is the cross-sectional area of the tube and p is its perimeter. Identify the fluid property responsible for the development of the velocity boundary layer and the kinds of fluids. References Section Break Difficulty: Easy What fluid property is responsible for the development of the velocity boundary layer? Viscosity of a fluid Mass density of a fluid Specific weight of a fluid Volume of a fluid The fluid viscosity is responsible for the development of the velocity boundary layer. Hint #1 References Multiple Choice Difficulty: Easy Previous attempt For the idealized inviscid fluids, there is no velocity boundary layer . True False The fluid viscosity is responsible for the development of the velocity boundary layer. For the idealized inviscid fluids(fluids with zero viscosity), there will be no velocity boundary layer. Hint #1 References True / False Difficulty: Easy Previous attempt ✓     ✓   Hints Hints Hints