A local ventilation system (a hood and duct system) is used to remove air and contaminants produced by a welding operation (Fig. P 14-55E). The inner diameter (ID) of the duct is D = 9.06 in, its average roughness is 0.0059 in, and its total length is L = 34.0 ft. There are three elbows along the duct, each with a minor loss coefficient of 0.21. Literature from the hood manufacturer lists the hood entry loss coefficient as 4.6 based on duct velocity. When the damper is fully open, its loss coefficient is 1.8. A squirrel cage centrifugal fan with a 9.0-in inlet is available. Its performance data fit a parabolic curve of the form
The volume flow rate.
Answer to Problem 55EP
The volume flow rate is
Explanation of Solution
Given Information:
The inner diameter of the duct is
Expression for steady energy equation from point 1 in the stagnant air region to point 2 at the duct outlet
Here, the required head for the fan is
Expression for the total head loss
Here, the velocity of the air is
Expression for Reynold's number
Here, the kinematic viscosity is
Expression for relative roughness
Here, the roughness of the pipe is
Expression for the friction factor
Expression for the volume flow rate
Here, the area of the pipe is
Expression for the area of the pipe
Substitute
Expression to convert the shutoff head from inches of water column to inches of air column
Here, the density of the water is
Expression to convert
Calculation:
Refer to the Table-A-9E, "Properties of air at 1 atm pressure" to obtain the density of the air as
Substitute
Substitute
Substitute
Substitute
Substitute
Substitute
Substitute
Substitute
Substitute
Substitute
Since at the operating point the available head and the required head are equal, therefore equate equation (XII) and (XIII).
Solve Equation (XII) and Equation (XIV) to obtain the value of velocity as
Substitute
Conclusion:
The volume flow rate is
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Chapter 14 Solutions
EBK FLUID MECHANICS: FUNDAMENTALS AND A
- As an engineer, you are setting up an experiment to measure the airflow rate in a duct. Choose a technique and devices for the measurement. You are required to design/draw the set-up and demonstrate the calculation for themeasurement of flow rate. Please discuss the relevant principle involved and reason for selectingthe technique.arrow_forwardPUMP SYSTEM – SYSTEM CURVE AND NPSH The pumping system shown below consists of a suction pipe of length 3m and diameter 80mm; delivery pipe of length 6m and diameter 80mm; 4 elbows, each with a loss coefficient of k = 0.3; total static lift = 6m; tank entry and exit loss coefficients 0.5 and 1.0, respectively; suction and delivery pipe friction factor f = 0.007Darcy. A Robuschi 150-500 pump rotates at 1470 rpm and the desired flow rate is a minimum of 200 m3/h. SUCTION PIPE Complete the following tasks: 1. Draw the system curve as described above on the Roubuschi pump curve data sheet supplied. Work in increments of Q 50m3/h starting at 0 (7-point curve) 2. Would you advise the client to select the p400 or ¢460 impeller? Give two reasons for your answer. If the 400 impeller is used: Assume: the gauge pressure in the suction tank at 115 kPa, the vapour pressure of the water at its average operating temperature at 20C suction height as 1.5 m. 3. Is the pump likely to cavitate? Support…arrow_forwardBA4s6nknAPkVXhnUEg rmResponse Good Luck... PROBLEM 1 Determine the following: a. Enclosed Area b. Perimeter of the thin walled tube Given is a thin-walled tube with the following data: Wall thickness-2mm ABC is a sector with a radius of 50 mm AOD & COD is a triangle C. Shear flow d. Shear stress e. Angle of twist Torque is 1000 N.m Length of the thin walled tube is 0.5 m Use G=24 GPa for aluminium A 90 B D 3R PROBLEM 2 Determine the following: a. Enclosed Area b. Perimeter of the thin walled tube c. Shear flow d. Shear stress Given is a thin-walled tube with the following data: Wall thickness- 3mm Torque is 900 N.m Length of the thin walled tube is 1.2 m. Use G=24 GPa for aluminium e. Angle of twist Ps Xd étv Warrow_forward
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- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning