Midterm32006soln

# Midterm32006soln - ENGR 225 Recitation 8:30-9:45 Sears 435...

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ENGR 225 Name ____________________________________ Recitation Midterm 3, November 28, 2004 _____ 8:30-9:45 Sears 435 _____ 10:00-11:15 Sears 435 _____ 1:15-2:30 Bingham 304 _____ 1:15-2:30 Olin 314 Short answer (2 pts. Each, for T/F and multiple choice circle the best answer of the choices given, fill in the blank must be completed with a meaningful word or phrase) 1. T F Mechanical energy can be defined as the form of energy that can be converted to mechanical work completely and directly by a mechanical device. 2. If a pump is being used to increase the mechanical energy of the fluid, the ratio of the mechanical energy increase to the energy used to power the pump is termed the pump’s ____ efficiency ___ and it is always less than or equal to one. 3. The Bernoulli Equation is a) an approximation b) a relation between pressure velocity and elevation c) assumes viscous effects are small d) all of the above e) none of the above 4 T F The Bernoulli Equation can be written is different forms such that the units on the terms are either pressure, energy per unit mass, or length. 5. In mechanical energy balance the conversion of mechanical energy to heat is considered a ___ loss ____ of energy. 6. The complete mechanical energy balance is a) P 1 / ρ + α V 1 2 /2 + gz 1 + w turbine = P 2 / ρ + α V 2 2 /2 + gz 2 + w pump + e mech,loss b) P 1 / ρ + α V 1 2 /2 + gz 1 + w pump = P 2 / ρ + α V 2 2 /2 + gz 2 + w turbine – e mech,loss c) P 1 / ρ α V 1 2 /2 + gz 1 + w pump = P 2 / ρ α V 2 2 /2 + gz 2 + w turbine + e mech,loss d) P 1 / ρ + α V 1 2 /2 + gz 1 + w pump = P 2 / ρ + α V 2 2 /2 + gz 2 + w turbine + e mech,loss 7. T F The kinetic correction factor, α , in the mechanical energy balance is equal to 2 for laminar flow and 1 for turbulent flow. 8. In the context of fluid flow, the ratio of inertial forces to viscous forces is termed the ___ Reynolds __ number. 9. The Reynolds number, Re, is a) hL/k b) ρ VL/ µ c) α t/x 2 10. T F When there is no pump in a piping system there must be a pressure difference between two points for the fluid to move. 11. The fluid immediately adjacent to a stationary wall has a velocity of ____ zero ____.

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12. Friction factor, f, is used to quantify one type of mechanical energy loss, it is a) equal to zero for laminar flow b) suddenly drops in value when flow goes from laminar to turbulent c) larger for smooth pipes than for rough ones when flow is turbulent d) all of the above e) none of the above 13. T F The added mechanical energy losses that occur due to bends on the pipe or the presence of valves, etc. are called “minor losses” and can be thought of accurately as effectively longer pipes.
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Midterm32006soln - ENGR 225 Recitation 8:30-9:45 Sears 435...

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