Centrifugal Fans
Table of Contents
A. Objective 2 B. Theory and Analysis 2 C. List of Apparatus 3 D. Procedure 4 E. Set-up of Apparatus 4 F. Final Data Sheet 6 G. Sample Computation 6 H. Test Data Analysis 7 I. Related Studies 8 J. Conclusion 18 K. Recommendation 19 L. References 19
A. Objective
1. To be familiar with the operating procedure and principle as well as the efficiency of centrifugal fans.
B. Theory and Analysis
Tests of ventilating fans or blowers are made frequently by a very simple method, that is, by determining the necessary data for a calculating efficiency by measuring the work done by the fan “on the air” in giving velocity, and the horsepower required to drive the fan alone, excluding bearing friction. The fan is preferably operated by an electric motor, of which the efficiency can be readily determined by a Prony Brake Test. The power required to overcome the bearing friction of the shaft of the fan may well be first determined by measuring the power input or a series of speeds when the keys fastening the fan to its shaft have been removed and the fan itself has been “blocked” in its casing or still better, has been removed from the shaft. After the fan is attached again to the shaft, the input to the motor and the work done by the fan “on the air” should be determined for various speeds. Then, obviously, the ratio of the work done by the fan divided by the power required to drive it after correction for the efficiency of the motor and bearing friction is the actual efficiency of the fan. In general terms this may be started as follows: f = input to motor to drive motor and shaft of fan in bearings i = input to motor to drive motor and fan, in kW e = efficiency of motor for motor input of 1kW and at speed of test e’ = efficiency of motor for motor input of 1kW and at speed of test
Then if in is the net work in
A. Objective 2 B. Theory and Analysis 2 C. List of Apparatus 3 D. Procedure 4 E. Set-up of Apparatus 4 F. Final Data Sheet 6 G. Sample Computation 6 H. Test Data Analysis 7 I. Related Studies 8 J. Conclusion 18 K. Recommendation 19 L. References 19
A. Objective
1. To be familiar with the operating procedure and principle as well as the efficiency of centrifugal fans.
B. Theory and Analysis
Tests of ventilating fans or blowers are made frequently by a very simple method, that is, by determining the necessary data for a calculating efficiency by measuring the work done by the fan “on the air” in giving velocity, and the horsepower required to drive the fan alone, excluding bearing friction. The fan is preferably operated by an electric motor, of which the efficiency can be readily determined by a Prony Brake Test. The power required to overcome the bearing friction of the shaft of the fan may well be first determined by measuring the power input or a series of speeds when the keys fastening the fan to its shaft have been removed and the fan itself has been “blocked” in its casing or still better, has been removed from the shaft. After the fan is attached again to the shaft, the input to the motor and the work done by the fan “on the air” should be determined for various speeds. Then, obviously, the ratio of the work done by the fan divided by the power required to drive it after correction for the efficiency of the motor and bearing friction is the actual efficiency of the fan. In general terms this may be started as follows: f = input to motor to drive motor and shaft of fan in bearings i = input to motor to drive motor and fan, in kW e = efficiency of motor for motor input of 1kW and at speed of test e’ = efficiency of motor for motor input of 1kW and at speed of test
Then if in is the net work in
References: * http://www.beeindia.in/energy_managers_auditors/documents/guide_books/3Ch5.pdf * http://www.energyefficiencyasia.org/docs/ee_modules/Chapter-Fans%20and%20Blowers.pdf * http://en.wikipedia.org/wiki/Mechanical_fan * http://www.engineeringtoolbox.com/pumps-compressors-fans-blowers-d_675.html