ME 495 Lab Final

Laser Vibrometry 2 1. Rise Time 2. Settling time

1. By definition it is the time required for the system to achieve a value of 90% of the step input. The rise time is decreased by decreasing the damping (see figure 3.13 above). Obviously there is a tradeoff between fast response and ringing (noise) in a second order system. 2. The settling time is defined as the time required for the system to settle to within ±10% of the steady state value. A damping ratio, , of 0.7 offers a good compromise between rise time and settling time. Most dynamic response measurement systems are designed such that the damping ratio is between 0.6 and 0.8

Rankine Cycle (See diagrams) -- > Propane used as gas 1. The 4 process's 2. Efficiency 3. Is a steam turbine larger or smaller than a gas turbine?

1. -Saturated liquid compressed to higher pressure (q = 0) COMPRESSOR h2 - h1 - Compressed liquid heated to super heated steam (w = 0) BOILER h3 - h2 - Super heated steam expands through TURBINE (q = 0) h3 - h4 - steam returned to saturated liquid (w = 0) CONDENSER h4 - h1 2. = Wnet/Qin 3. Smaller

Laser Vibrometry 2 1. Rise Time

1. By definition it is the time required for the system to achieve a value of 90% of the step input. The rise time is decreased by decreasing the damping (see figure 3.13 above). Obviously there is a tradeoff between fast response and ringing in a second order system.

Plate Heat Exchange (INDIRECT) 1. Parallel or counter flow? 2. What makes it indirect? -Each stream passes 3 times in series across the plate -The temperature difference across the plate causes the heat transfer between the streams. 3. What does LMTD stand for and how is it related to Heat Transfer? AS COLD STREAM FLOW DECREASED SO DID EFFICIENCY.

1. Counter flow --> streams flow in opposite directions 2. Because the fluid streams are separated by a thin wall 3. Log Mean Temperature Difference ---> It is the maximum temperature difference that can be achieved in any geometry of the heat exchanger

Vibration Analysis 1. Why do we measure vibration? 2. What do the vertical, horizontal and axial measurements detect? 3. Cause of vibration

1. The vibration meter can be used to measure the condition of the belt drive and correct problems before deficiencies cause failure. **Predictive maintenance 2. vertical/horizontal --> Detect worn or stretched belts Axial --> Belt or sheave misalignment 3. Misaligned shafts, worn bearings, unbalanced rotating elements

Brayton Cycle (See diagrams on paper) 1. 4 process's 2. Cold - air assumption

1. The working fluid (air) is an ideal gas throughout the cycle. 2. The combustion process is constant-pressure heat addition. 3. The exhaust process is constant-pressure heat rejection. 4. The specific heat is constant at the lowest temperature in the cycle. 2. Air is considered and ideal gas - All process's are ideal and reversible - specific heat is constant k = 1.4 http://www.sfu.ca/~mbahrami/ENSC%20461/Notes/Internal%20Combustion%20Engine.pdf

Bomb Calorimeter 1. What is the point? 2. What was measured? 3. What is used to calculate? 4. what does m* denote? 5. If the student used a liquid with cp = 2 instead of water, with cp = 4.184, what happens to the temperature change? Larger or smaller?

1. To determine the heating value of a solid and liquid fuel sample using a bomb calorimeter 2. Measured the burned mass and water temperature change during the allotted time 3. HV = [(m*cvT)water - (mass changeHV)wire]/mass of fuel 4. m* is the theoretical mass - the mass of the water needed to absorb the heat released by the reaction . IT ACCOUNTS FOR ALL MATERIAL ---> Solve for m* from HV equation 5. I would assume the HV to go down if everything stays the same

Tubular Heat Exchange (DIRECT) 1. Describe the system 2. Which is preferred, counter or parallel flow? Draw counter and parallel flow 3. KNOW ALL OF THE EQUATIONS 4. Did the heat exchange remove more or less heat from the hot stream as the flow rate of the cold water decreased? 5. What about efficiency? 6. what does the HT coefficient represent?

1. Two coaxial tubes, inner = hot and metal, outer = cold and acrylic 2. Counter flow -> temperatures remain constant along full length of the exchange which eliminates extreme temperature difference that would cause damage from thermal stress 4. Less ---> Lower overall heat transfer coefficient (U) 5. Efficiency decreased as cold water flow decreased 6. It indicates the how effectively the system is transferring heat Or How well heat is conducted through a series of mediums

Hydrostatic Pressure 1. Objective 2. Describe the hydro static force on the object produced by the water 3. As the depth increases, so does the...? 4.

1. determine hydrostatic thrust on plane surface and the line of action 2. The force is constant, however varies at different depths - For fluids at rest we know that the force must be perpendicular to the surface since there are no shearing stresses present. - The pressure varies linearly with depth if the fluid is incompressible. 3. - The turning moment - the hydro static force - the depth of pressure

Laser Vibrometry 1. What is it? 2. What was measured? What kind of force? 3. What are vibrations characterized by? 4. What is the natural frequency? 5. What is the damping ratio (zeta) ? how is the damping coefficient (c) related? 6. under, Critically & Overdamped. Draw this What is Zeta equal to?

1. quantitatively characterizing surface vibrations in a mechanical system 2. Displacement, velocity, and acceleration of mechanical vibrations in a speaker cone when harmonically excited. 3. the natural frequency, which is dependent on mass on the spring constant and the damping ratio 4. The natural frequency is the frequency at which the material is oscillating at indefinitely once set in motion, granted that there is no damping. However, if damping is put into the system, the oscillations will eventually die out, and the materials will experience less vibration over time 5. zeta = actual damping / critical damping zeta = c / 2*sqrt(km) zeta < 1 --> Underdamped zeta = 1 --> Critically damped zeta > 1 --> Overdamped