A run-around heat exchanger system to improve the energy efficiency of a home appliance using hot water

Jae Sung Park, Anthony M. Jacobi

Research output: Contribution to journalArticlepeer-review


A significant portion of the energy consumed by many home appliances using hot water is used to heat cold supply water. Such home appliances generally are supplied water at a temperature lower than the ambient temperature, and the supply water is normally heated to its maximum operating temperature, often using natural gas or an electrical heater. In some cases, it is possible to pre-heat the supply water and save energy that would normally be consumed by the natural gas or electrical heater. In order to save the energy consumed by an appliance using water heater, a run-around heat exchanger system is used to transfer heat from the ambient to the water before an electrical heater is energized. A simple model to predict the performance of this system is developed and validated, and the model is used to explore design and operating issues relevant to the run-around heat exchanger system. Despite the additional power consumption by the fan and pump of the run-around heat exchanger system, the experimental data and analysis show that for some systems the overall energy efficiency of the appliance can be improved, saving about 6% of the energy used by the baseline machine.

Original languageEnglish (US)
Pages (from-to)3110-3117
Number of pages8
JournalApplied Thermal Engineering
Issue number14-15
StatePublished - Oct 2009


  • Energy efficiency
  • Heat exchanger
  • Home appliance
  • Water heater

ASJC Scopus subject areas

  • Mechanical Engineering
  • Energy Engineering and Power Technology
  • Fluid Flow and Transfer Processes
  • Industrial and Manufacturing Engineering


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