Thermal Fan

Technology Description

This thermal fan device operates, in principle, similarly to a heat pipe by utilizing the latent heats of vaporization and condensation with the corresponding phase changes to move a fluid like air. A phase change working fluid is contained within a confined volume that is exposed to the low-grade heat. The working fluid is selected with a vaporization temperature compatible with the high temperature of the low-grade heat source. A compliant or flexible bellow is contained within that otherwise rigid volume, and pressure change resulting from the phase change of the working fluid will cause the bellow to expand or contract. Repeated in a cyclic fashion and coordinated with additional units, this can create a continuous flow of air without any mechanical pumping.

Features & Benefits

  • Efficient and inexpensive
  • Mechanically simple
  • Useful over a broad temperature range


  • Anywhere low-grade heat is available near a need for process air flow
  • Renewable energy generation
  • Water treatment and purification

Background of Invention

A large portion of waste energy generated globally is in the form of low-grade heat. Because of the relatively low temperatures and low Carnot efficiency, very few technologies can recover this energy in an economical way. Numerous industrial applications require air flow and are near sources of low grade heat. Examples include power plants; chemical, pharmaceutical, and food processing; water treatment, purification, and desalination; and many others. In all instances, low-grade heat is readily available near process needs for condenser cooling, dehydrating, thermal regulation, etc. In most instances, the low-grade heat is wasted and the necessary process operations are powered separately, increasing costs and reducing overall efficiency. This technology can efficiently utilize low-grade heat to generate the air flow that is needed in many of these applications.


Patent pending, seeking development partners   

The flowchart illustrates how the thermal fan operates through one cycle of moving air. Multiple fans can be operated in coordination to maintain continuous air flow.

Patent Information:
Tech ID:
David Dickson
IP & Licensing Manager
Oregon State University
Bahman Abbasi
Deepak Sharma
air circulation
low-grade heat
thermal fan
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