Application of a Two-Phase Closed Thermosyphon To Improve Refrigerator Efficiency


  • Electricity consumption: Conventional residential refrigerators takes a large part( over 50% ) in kitchen appliance electricity consumption of U.S. households.
  • Cost: At a national average electrical cost of $0.12/kWh, more than 150 billion kWh of electricity consumption represents an annual cost of $18 Billion.

Two-Phase Thermosyphon

A thermosyphon is simple in construct and design (Picture on left), consisting of a hollow tube that has been evacuated and filled with a working fluid. It consists of three sections:

  • Condenser section
  • Adiabatic section
  • Evaporator section


  • Low temperature drop: latent heat evaporation reduce the temperature drop between refrigerated space and environment.
  • Less external power: The condensed fluids flow down to the evaporator only by gravity, thus no pump is needed.
  • Reliability: self-contained, no moving parts.


  • Our idea is to place a thermosyphon inside of a refrigerated space, e.g., a residential refrigerator, then extend the top of the thermosyphon vertically or through a wall until it passes through the building envelope to the outside. (Picture on left)
  • The device would be fitted with heat sinks on both the evaporator and condenser ends.
  • The thermosyphon behaves like a thermal diode, thus reducing the need to operate the electrically powered refrigeration system in the refrigerator.

Research Goal

  • Find candidate working fluids to get the smallest temperature drop by testing several working fluids in the simulation of refrigeration process.
  • Improve heat transfer coefficient outside the thermosyphon by adding annular fins.

  • The right side picture shows our expreiment devices