Performance comparison of energy savings between speed adjustment of seawater cooling pumps

Chien-Hsing Lee, K. M. Ho

Research output: Contribution to journalArticle

Abstract

With basic principles in the design of heat exchangers in a ship's central cooling system, sea water cooling pumps are normally designed to maintain the temperature of inlet seawater at 32°C and outlet freshwater at 36°C based on the average temperature of seawater at 25 °C when the pumps are under full speed to reach the flow nowadays. However, seawater temperatures have ever gone up this high only in limited areas in the seas around the world within certain seasons, and their temperatures are usually below 32°Cand are changeable. Thus, the actual in-take seawater flow can be reduced, resulting in a large reduction of the required amount of electrical energy. This paper compares energy consumption reduction in seawater pumps using a variable frequency drive (VFD) and throttle valve to continuously supply seawater flow to a ship's cooling system. A pump characteristic curve is used in this study to calculate the minimum flow rate of seawater cooling pumps for overcoming the friction losses in the pipe. The actual seawater flow needed is obtained from thermal equilibrium calculation, and then the flows are used to calculate the energy consumption for seawater cooling pumps. In addition, the theoretical results obtained from this paper are validated by an experiment of a small-scale cooling system and this theoretical method is applied to assess the energy-saving benefit of the actual voyage for a practical ship. Hopefully, the study of this paper can be used for ship design for future reference.

Original languageEnglish
Pages (from-to)99-113
Number of pages15
JournalJournal of Taiwan Society of Naval Architects and Marine Engineers
Volume32
Issue number3
Publication statusPublished - 2013 Aug 1

All Science Journal Classification (ASJC) codes

  • Ocean Engineering
  • Mechanical Engineering

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