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  1. ENTC 303: Announcements • Homework assignment No. 1 • FromMott: 1.45, 1.49, 1.55, 1.83, 1.86, 1.89, 2.19, 2.29, 2.48, 2.58, 2.68. • From Esposito: 2-2, 2-3, 2-27, 2-39. • Due next Tuesday, September 16thbefore 3:35 pm • For more information, go to: • http://etidweb.tamu.edu/classes/entc303/ • We will have labs this week • We will meet at Thompson 008 (DXP Pump Lab)

  2. Manufacturing & Mechanical Engineering Technology Program New and Transfer Student Orientation Meeting You are cordially invited to participate in the MMET New and Transfer Student Orientation Meeting. The purpose of this event is to introduce you to the MMET program faculty and staff as well as to share with you our vision, mission, and expectations during your undergraduate career. DATE: Monday, September 15th, 2014 TIME: 6:00 p.m. to 7:00 p.m. PLACE: Thompson 112D Pizza and refreshments will be served. Include any dietary restrictions you might have in your RSVP. Please respond before 5:00 PM on Thursday, Sep 11th to Linda (ljchandler@tamu.edu)

  3. http://en.wikipedia.org/wiki/SAE_viscosity_number#Grades http://www.liquidcontrol.com/etoolbox/viscosity.aspx

  4. Viscosity Chart m Force Temp. ° F  http://webbook.nist.gov/chemistry/fluid/ Temp. C http://www.klassenhydraulics.com/Reference/viscositychart.htm

  5. Hydraulics Fluids for Fluid Power Systems • Fluid Power • Pneumatics: air-type systems • Hydraulics: liquid-type systems • Hydraulic Fluids: • Petroleum oils • Water-glycol fluids • High water based fluids (HWBF) • Silicone fluids • Synthetic oils http://en.wikipedia.org/wiki/Hydraulic_fluid

  6. Characteristics of Hydraulic Fluids • Adequate viscosity • Lubricating capability • Cleanliness • Chemical stability • Non-corrosiveness • Ability to resist growth of bacteria • Ecologically acceptable • Low compressibility http://www.castrol.com/castrol/sectiongenericarticle.do?categoryId=9045295&contentId=7080615

  7. Hydraulic Fluids • HWBF • Fire resistant • ~40% oil in water • Water-glycol fluids • Fire resistant • 35 to 50% water https://engineering.purdue.edu/Maha/index.html

  8. Hydraulic Fluids • Petroleum Oils • SAE 10 W, SAE 20-20W (W means rated at maximum viscosity and cold temperatures) • Engine oils • Additives are required to avoid growth of bacteria • Silicone Fluids • For high temperature applications http://en.wikipedia.org/wiki/SAE_viscosity_number#Grades

  9. Key Concepts/Properties • Pressure: • Amount of Force exerted on a unit area • P = Force/Area • Pressure acts uniformly in all directions and perpendicular to the boundaries in the container • Example: Piston Force Area= p/4*D2 P Pressure=Force/Area Unit: Psi or Pa (SI)

  10. Pressure • Pressure: • Absolute = Gage + Atmospheric* • psia = psig + 14.7 psia • *14.7 psia at sea level

  11. Pressure Scale http://www.wisc-online.com/objects/ViewObject.aspx?ID=IAU3806

  12. Units of Pressure • 1 bar = 105 Pa = 0.1 MPa = 100 kPa • 1 atm = 101,325 Pa = 101.325 kPa • 1 atm = 1.012325 bars • 1 mm Hg = 0.13333 kPa • 1 atm = 14.696 psi ≈ 14.7 psi • Example: If the pressure is 921 mbars at one point, determine the pressure in atm and in psi. • Determine atmospheric pressure in psi and kPa

  13. Example • Express 155 kPa (gage) as an absolute pressure. Local atmospheric pressure is 98 kPa. • Express 225 kPa (abs) as a gage pressure. The local atmospheric pressure is 101 kPa. • Express a pressure of -6.2 psig as an absolute pressure

  14. Pascal’s Law(Esposito 3.3) • “Pressure applied to a confined fluid is transmitted undiminished in all directions throughout the fluid and acts perpendicular to the surfaces in contact with the fluid” • In a simple hydraulic jack application: http://hyperphysics.phy-astr.gsu.edu/hbase/pasc.html#hpcal

  15. Pressure and Elevation • Change in pressure in homogeneous liquid at rest due to a change in elevation:

  16. Pressure and Elevation • Change in pressure in homogeneous liquid at rest due to a change in elevation: DP = gh DP = Pbottom – Pabove = gh Where, DP = change in pressure, psi or kPa • = specific weight, N/m3, lb/ft3 h = change in elevation, m or ft Note: Pressure increases (+) with depth Pressure decreases (-) with elevation

  17. Pressure-Elevation Relationship • Valid for homogeneous fluids at rest (static) P2 = Patm + rgh Free Surface Free Surface P2 P1 P1 > P2

  18. Static Fluids: Same elevation and same fluid → same pressure P2 = Patm + rgh 1-15

  19. Pascal’s Paradox h

  20. Examples • Compute the change in water pressure from a free surface to a depth of 5m • Tank of oil has one side open and the other one sealed with air. Oil specific gravity is 0.9. Calculate gage pressure at points A, B, C, D, E and F.

  21. D B Example Air Air Air Already in static equilibrium F Open A E Oil C - Vertical distance between A-B and A-D is 3.0 m - Vertical distance between A-C is 6.0 m - Vertical distance difference between A-F is 1.5 m - The oil’s specific gravity is 0.9

  22. Already in static equilibrium too, but different conditions: Both sides are open to the atmosphere Oil B D

  23. Manometers • Used to measure pressure • Takes advantage of DP = gh relationship http://www.efunda.com/formulae/fluids/manometer.cfm