Manometers and Pressure Calculation

Identify the units systems for common quantities used in Fluid Mechanics

Define Pressure

Fluid Properties: Compressibility, Density, Specific weight, Specific gravity, ________

Dynamic (absolute) viscosity, Kinematic viscosity, ________

Identify the units for the basic quantities of time, force and mass in SI System (metric)

SI unit Prefixes

Identify the units for the basic quantities of time, force and mass in U.S.Customary System

S.I. and U.S.

Using Fig. 3.10, calculate the pressure at point A.◼ The only point for which the pressure is known is the surface of the mercury in the right leg of the manometer, point 1.◼ p1 = p______ = 0 _ Pa ( gage) p2 = p1 +  m  0.25m 1/31/2022 p2 = p3 Cristina Toma 23 Pressure: Types and measurement Objective 3 ◼ Manometers(U-tube)

Using Fig. 3.10, calculate the pressure at point A.◼ p = p3 − p4 =  w  h =  w  0.40m p3 = p4 +  w  0.40m sg = s  w@ 4C =  w = 9.81 1/31/2022 s  w@ 4C kN m3 W    s g  V s  = = g W   w@ 4C    V  w @ 4C  m = (sg ) m  9.81 kN kN kN = 13. 54  9. 81 = 132. 8 m3 m3 m3 Cristina Toma 24 Pressure: Types and measurement Objective 3 ◼ Manometers (U-tube)

This can also be read “28.2 kPa below atmospheric pressure” or “28.2 kPa ______.”

The change in pressure in a homogeneous liquid at rest due to a change in elevation can be calculated from: Δp = γ ⋅ h Δp = change _ in _ pressure γ = specific _ weight _ of _ liquid h = change _ in _ elevation 1/31/2022 Cristina Toma w γ = V Where: w=weight V=volume 7 Pressure: Types and measurement Objective 2 ◼ Relationship between Pressure and Elevation ◼ ◼ The term elevation means the vertical distance from some reference level to a point of interest and is called z.A change in elevation between two points is called h.Elevation will always be ______ positively in the upward direction.◼ ◼ In other words, a higher point has a larger elevation than a lower point.Fig 3.2 shows the illustration of reference level for elevation 1/31/2022 Cristina Toma 8 Pressure: Types and measurement Objective 2 Relationship between Pressure and Elevation Problems 1) Calculate the change in water pressure from the surface to a depth of 5 m.Use Appendix A: Properties of water.◼ A: Δp = 49.05kPa 1/31/2022 Cristina Toma 9 Pressure: Types and measurement Objective 2 Relationship between Pressure and Elevation Problems 2) Calculate the change in water pressure from the surface to a depth of 15 ft.Use Appendix A: Properties of water.

The change in water pressure from the surface to a depth of 5 m.Use Appendix A: Properties of water.◼ A: Δp = 49.05kPa 1/31/2022 Cristina Toma 9 Pressure: Types and measurement Objective 2 Relationship between Pressure and Elevation Problems 2) ______ the change in water pressure from the surface to a depth of 15 ft.Use Appendix A: Properties of water.

1. Calculate the change in water pressure from the surface to a depth of 5 m.Use Appendix A: Properties of water.◼ A: Δp = ______ 1/31/2022 Cristina Toma 9 Pressure: Types and measurement Objective 2 Relationship between Pressure and Elevation Problems 2) Calculate the change in water pressure from the surface to a depth of 15 ft.Use Appendix A: Properties of water.

Calculate the ______ in water pressure from the surface to a depth of 15 ft.Use Appendix A: Properties of water.

A: Δp = 49.05kPa 1/31/2022 Cristina Toma 9 Pressure: Types and measurement Objective 2 Relationship between Pressure and Elevation Problems 2) Calculate the change in water pressure from the surface to a depth of 15 ft.Use ______ A: Properties of water.

The term elevation means the vertical distance from some reference level to a point of interest and is called z.A change in elevation between two points is called h.Elevation will always be ______ positively in the upward direction.

In other words, a higher point has a larger elevation than a lower point.Fig 3.2 shows the illustration of reference level for elevation 1/31/2022 Cristina Toma 8 Pressure: Types and measurement Objective 2 Relationship between Pressure and Elevation Problems 1) Calculate the ______ in water pressure from the surface to a depth of 5 m.Use Appendix A: Properties of water.

The change in elevation between two points is called h.Elevation will always be measured ______ in the upward direction.

In other cases there is a need to measure ______ at one point and display the value at another.

The general term for such a device is pressure ______, meaning that the sensed pressure causes an electrical signal to be generated that can be transmitted to a remote location such as a central control station where it is displayed digitally.

For those situations where only a visual indication is needed at the site where the pressure is being measured, a pressure ______ is used.

The pressure to be measured is applied to the inside of a flattened tube, which is normally shaped as a segment of a circle or a ______.

The pressure to be measured is introduced through the pressure port and acts on a diaphragm to which foil strain gages are bonded. As the strain gages sense the deformation of the diaphragm, their resistance changes. The readout device is typically a digital voltmeter, calibrated in pressure ______.

Using Fig. 3.10, calculate the pressure at point A. The only point for which the pressure is known is the surface of the mercury in the right leg of the manometer, point 1. p1 = p______ = 0 _ Pa ( gage) p2 = p1 +  m  0.25m 1/31/2022 p2 = p3 Cristina Toma 23 Pressure: Types and measurement Objective 3 ◼ Manometers(U-tube)

Using Fig. 3.10, ______ the pressure at point A. p = p3 − p4 =  w  h =  w  0.40m p3 = p4 +  w  0.40m sg = s  w@ 4C =  w = 9.81 1/31/2022 s  w@ 4C kN m3 W    s g  V s  = = g W   w@ 4C    V  w @ 4C  m = (sg ) m  9.81 kN kN kN = 13. 54  9. 81 = 132. 8 m3 m3 m3 Cristina Toma 24 Pressure: Types and measurement Objective 3 ◼ Manometers (U-tube)

Dynamic (absolute) viscosity, Kinematic viscosity, ______