Power characteristics of variable frequency speed control-based water pumps in open cooling water systems

Abstract

The operational power characteristics of variable frequency speed control-based water pumps in an open cooling water system were studied experimentally. It was found through this research that before and after frequency conversion, the ratio of the power of a particular frequency to the power of the rated frequency of the water pump system shows a third-power relationship. A data fitting method was used to obtain the equation for the power and frequency ratio of the system under the overall operating conditions. The experiment shows that the system height difference has no effect on the basic form of the characteristic equation. Finally, when unified consideration is given to the pump, motor and frequency converter, the calculated power of the water pump system is very close to the actual value.This power characteristic equation contributes to calculations relating to the water pump operational speed regulation in an open cooling water system.

Practical application: Variable frequency speed-regulating systems for pumps are applied in open loop water systems, such as those supplying cooling towers. However, the standard cube law which is used to determine the power of the water pump system is inappropriate and exaggerates the potential energy-saving. This study determined a new energy model for the water pump system that can more accurately calculate the total power of the variable frequency controlled water pump when used in open loop systems.

Keywords

Open cooling water system system height difference valve opening variable frequency speed control water pump

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References

Europumpand Hydraulic Institute and the US Department of Energy’s Office of Industrial Technologies. Pump Life Cycle Costs: A Guide to LCC Analysis for Pumping Systems. Guide, January 2001.

Jiang

. Control and analysis on variable flow operation of cooling water system. Archit Technol 2015; 46: 167–179.

. Study on variable-frequency water pump unit performance. City Town Water Supply 2010, pp. 60–62.

Cao

. Analysis of frequency conversion-based energy conservation of cooling water and chilled water system of central air conditioning. Var Freq Speed Control Appl 2014; 41: 62–66.

Lin M. Study on energy conservation of cooling water in primary pump system with variable flow rate. Master's Degree Thesis, Xi’an University of Architecture and Technology, China, 2009.

. Optimization of the number of multiple pumps running simultaneously in open cycle cooling water system in power plant. Energy Procedia 2012; 17: 1161–1168.

Yang Z. Energy efficient control of a boosting system with multiple variable-speed pumps in parallel. In: 49th IEEE Conf Decis Control, Atlanta, GA, 15–17 December 2010, pp.2198–2203. Piscataway, NJ: IEEE.

Wang

Chen

. A direct optimal control strategy of variable speed pumps in heat exchanger networks and experimental validations. Energy 2015; 85: 609–619.

Michel

. Pumping energy and variable frequency drives. ASHRAE J 1999; 41: 37–38.

10.

Yang L. Study on simulated optimization of the cooling water system of TRNSYS-based air conditioning. Master's Degree Thesis of South China University of Technology, China, 2013.

11.

Huang Y. Air conditioning water system dynamic optimization simulation research. Guangzhou University, China, 2012.

12.

ASHRAE. ASHRAE handbooks–HVAC systems and equipment, Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., 2008.

13.

Liu

. Water pumps and water pump stations, 4th ed. China: Water & Power Press, 2009.

14.

Zhao

Song

. Experimental study on operation characteristics of variable frequency speed-regulating pump in opening system. Gas Heat 2016; 36: 4–9.

15.

Song Y and Zhao J. Operating characteristics of the variable frequency speed-regulating system for a single pump in a closed system. Build Serv Eng Res Technology 2016; 38: 309–317.

16.

Wan

. Experimental study on relative velocity of water flow in centrifugal pump impellers. Mech Design 2005; 22: 38–40.

17.

Chen Q. Discussion about low-specific-speed centrifugal pump disc loss calculation and the numerical analysis of internal flow characteristics. Master's Degree Thesis, Lanzhou University of Technology, China, 2012.

18.

Stepanoff

. Theory, design and application of centrifugal pumps and axial-flow pumps, China, Beijing: China Machine Press, 1980.