# Chapter 3.2 Notes - PowerPoint PPT Presentation

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Chapter 3.2 Notes. Rate in Fluids. Rates in fluid systems describe the motion of liquids and gases . Fluids in motion have speed and acceleration; however we use two different rates to describe how quickly fluids flow – volume flow rate and mass flow rate.

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Chapter 3.2 Notes

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## Chapter 3.2 Notes

Rate in Fluids

• Rates in fluid systems describe the motion of liquids and gases.

• Fluids in motion have speed and acceleration; however we use two different rates to describe how quickly fluids flow – volume flow rate and mass flow rate.

• V represents the volume of fluid in a container.

• The volume flow rate is the change in volume per unit time.

• represents volume flow rate

• Equation for volume flow rate = change in volume / time

• If the volume flow rate of the oxygen in the shuttle is 16,800 gallons per minute and the tank can hold 143,000 gallons, how long can the shuttle supply oxygen?

• Vfr = rV / t

• 16,800 gal/min = 143,000 gal / t

• t = 143,000 gal/min /16,800 gal

• t = 8.51 min

### STOP!

Algebra Lesson

• The mass flow rate is the mass of fluid moved per unit time.

• represents the mass flow rate

• The equation for mass flow rate = change in mass/time

• If the shuttle’s fuel tank can hold 7000 grams of hydrogen and is consumed during the first 7 minutes of flight, what is the mass flow rate?

• Mfr = mass / time

• Mfr = 7000 grams / 7 min

• Mfr = 1000 grams/min

• Methods for measuring volume and mass flow rates vary, depending on the situation.

• The simplest, most direct method to find average flow rate is to collect fluid and measure the amount of fluid collected over time.

• Flowmeters measure the average flow rate of fluids by measuring pressure and velocity and calculating the flow rate.

• Flowmeters use indirect methods to measure flow rates so that they do not interrupt the flow.

### Flow Meter Demo

• Volume flow rate equation using speed = area x speed

• Mass flow rate equation using speed = density x area x speed

• To find cross sectional area of a pipe use this equation = pi x r2

• If the pipe is 18 meters in diameter and the speed of the liquid is 24 m/s, what is the volume flow rate?

• A = pi x r2

• r = d/2 = 18/2 = 9 m

• A = 3.14 x 92 = 254.34 m2

• Vfr = Area x speed

• Vfr = 254.34 m2 x 24 m/s

• Vfr = 6104.16 m3/s

• If the mass density is .5 g/L, the diameter of the pipe is 10 meters, and the speed is 190 m/s, what is the mass flow rate?

• A = pi x r2

• r = d/2 = 10/2 = 5 m

• A = 3.14 x 52 = 78.5 m2

• Vfr = Area x speed x density

• Vfr = 78.5 m2 x 190 m/s x .5 g/L

• Vfr = 7457.50 g/s