University of Arkansas - AgriScience Project

AGRISCIENCE EXERCISE

PHYSICAL SCIENCES IN AGRICULTURE

Key Concept: Energy & Power Systems

Sub-Concept: Power Transmission

Agricultural Application: The agricultural industry relies on the efficient transmission of power in mechanical systems.

Exercise: Determining Horsepower Developed by a Fluid System

Applied Principle(s): Work & Power in Mechanical Systems

Goals:

  1. Calculate fluid pressure.
  2. Determine the volume of fluid moved by a pump.
  3. Use fluid pressure and volume values to determine the horsepower output of a pump.


Materials:

Procedures for Conducting the Activity:

  1. Divide the class into pairs of students, and provide each with a data sheet and the necessary materials for this exercise.
  2. Instruct the students to complete the activity as directed on their data sheets. You may wish to monitor their progress as they work; however, it is suggested that the students be left to follow the instructions and complete the activity on their own.
  3. Once all groups have completed the exercise, discuss the answers to the discussion questions as a class. Be sure to make note of the practical agricultural applications of the principles demonstrated.


AGRISCIENCE EXERCISE

- Determining the Horsepower Developed by a Fluid System -

Student Data/Instruction Sheet

1. Gather the following materials:

2. Assemble the materials as shown in the schematic below:























Note: The use of electricity around water can be hazardous. Observe all safety precautions as outlined by your instructor.

3. Place the bucket from the work table onto the platform scale. Set the scale to read zero. Return the bucket to the work table.

4. Fill the bucket on the floor with water.

5. Measure the vertical distance indicated in the schematic. Record this distance below:

elevation = __________ ft.

6. Start the pump and transfer the water from the bucket on the floor to the bucket on the work table. Record the amount of time required to transfer all of the water.

Time = __________ min.

Note: Do NOT allow the pump to run dry; turn the pump "off" just as the water level reaches the top of the pump inlet.

7. Place the bucket from the work table onto the platform scale. Determine the weight of water moved, and record below.

Weight of water = __________lbs.

8. Determine the amount of horsepower developed by the pump, as follows:

a. Calculate the pressure difference in the column of water at the pump inlet and outlet.

Pressure = 0.433 x sg x elev. = __________psi

b. Calculate the pump's flow rate (gpm).

Volume (ft.3) = Weight of water (lbs.)

62.4-lbs./ft.3 = __________ft.3

Volume (gal) = Volume (ft.3) x 7.48 gal/ft.3 = __________gal.

Flow rate (gpm) = Volume (gal.)

Time (min.) = __________gpm

c. Calculate the fluid horsepower (FHP) developed by the pump.

FHP = Pressure, psi x Flow Rate, gpm

1714 = __________FHP

d. Check your answer by comparing your results to results obtained using the formula for linear horsepower.

HP = Force, lbs. x Distance, ft.

Time, min. x 33,000 = __________HP



9. Answer the following questions. Be prepared to discuss your answers with the class.

a. What is the difference between fluid horsepower and mechanical horsepower?









b. What is the "generic" definition of power?









How is this definition applied to calculating horsepower in a fluid power system?







c. What values must you determine in order to calculate horsepower in a fluid system? How are these values usually measured?











d. Describe how you could determine the efficiency of the pumping operation just completed.

















e. Assume a pump delivers 350 gpm at a pressure of 30 psi. How much fluid horsepower is being developed?













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