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CHE3040 Operations Laboratory Assignment

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Operations Laboratory (CHE3040)

   

Added on  2019-10-18

CHE3040 Operations Laboratory Assignment

   

Operations Laboratory (CHE3040)

   Added on 2019-10-18

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abpppWnBHP2CHE 3040 UNIT OPERATIONS LABORATORY ICentrifugal Pump CharacteristicsPurposeThe purpose of this experiment is to determine the effect of flow rate and speed on the head, efficiency, and brake horsepower requirement of a centrifugal pump. Background/TheoryMcCabe, Smith, and Harriott, 5th edition1 (Eqn. 8.1, p. 190), gives the following modifiedBernoulli equation (Equation 1) for systems with a pump: (1)Figure 1 illustrates the terms in this equation. For a system with no elevation change across the pump, Za = Zb. If the pipe diameter is the same for the suction and discharge lines, Va = Vb. Canceling the elevation and kinetic energy terms yields Equation 2:(2)where:pa= pump suction pressure [lbf/ft2]pb= pump discharge pressure [lbf/ft2]= density of fluid [lbm/ft3] (Figure 2 shows water density versus temperature)Wp= ideal pump work per unit mass flowrate [lbf-ft/lbm]= overall mechanical efficiency of the pumpMultiplying the right hand side of Equation 2 by gc/g gives the head (hp) for this pump in feet. The shaft work or brake horsepower (BHP) for the pump can be calculated from the shaft torque and rpm readings using Equation 3.(3)where:= shaft torque [lbf-ft]n= shaft speed [min-1]BHP= shaft work [lbf-ft/min]Multiply BHP by 3.0303 x 10-5 to get shaft work in horsepower [hp]. Divide BHP by the mass flowrate [lbm/min] to get Wp. Once Wp is known, Equation 2 can be used to solve for the pump efficiency .McCabe, Smith, and Harriott, 5th edition1 (Eqn. 8.7, p. 191), gives the following equation (Equation 4) for available net positive suction head (NPSH) in feet:Page 1 of 5as of August 4, 2016cbbcbbpcaacaagVggZpWgVggZp2222
CHE3040 Operations Laboratory Assignment_1
Figure 1. An illustration of the terms in Equations 1, 2, and 4 (Figure 8.5, p. 190,McCabe et al1).Figure 2. Density of water versus temperaturePage 2 of 5as of August 4, 2016
CHE3040 Operations Laboratory Assignment_2

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