E!10531 Flexible Capillary Heat Exchangers (FLEXIHEAT) 7D16008, 600329

Project within Eurostars-2 with financial support of Ministry od Education, Youth and Sports of the Czech Republic


What we want to do

Mechanically flexible polymer capillaries with a small diameter, usually below 1.0 mm, show an exceptionally high heat transfer coefficients if used as the heat transfer elements. Several hundreds or even thousands capillaries are used to form an equivalent of a shell or tube meal based heat exchanger. These polymeric heat exchangers give realistic promise for a novel product with much reduced cost and weight when compared to traditional aluminium or copper based heat exchangers.

Why we want to do it

Our feasibility study demonstrated plastic fibre-based materials used in heat exchange surfaces with 85% weight reduction and potentially at least 30% cost saving when compared with the metal heat exchangers. Our current development reached technology demonstration level TRL 6-7. We now aim to bring the technology to pre-production level (TRL 8-9) in the HVAC industry (HVAC – heating, ventilating and air conditioning).


The plastic heat exchanger with hollow fibres is a breakthrough new product enabling new applications and opening potentially new industries. To our knowledge, there is no similar product currently available on the market. Expected development is well supported by 8 years of research and prototyping of these heat transfer surfaces at the university level (Brno University of Technology). The envisioned development is related to reliability of production, higher internal pressures of the cooling liquids and quality testing.

The product principal difference is in the use of newly found principles of heat transfer on micro-surfaces. Similarly, the use of wall thickness smaller than hundred microns eliminates the wall thermal resistance. It should be stressed that for example polypropylene fiber (outer diameter of 0.8 mm and wall thickness of 0.1 mm) withstands internal pressure of 70 bar without rupture (!).

There are some differences caused by the use of plastic material: This elasticity and flexibility can be used in several ways, for example:

  • Bundles connected to input/output pipes can be submerged into stationary of slow moving liquid. This type of bundle application is suitable for example for extracting of low potential heat from warm waste water.
  • Bundles can be put into a tube (housing) and form counter flow heat exchangers. This configuration is suitable for both gases and liquids.
  • Bundles can be put into a box or duct of any shape.
  • Elasticity of chaotized bundles can be used to form heat exchangers of atypical shapes.

 The heat exchangers can be used in both modes with no modifications:

  • Forced Convection
  • Natural Convection

Details about polymeric heat exchangers


What is the main goal

The project goal is to develop technology for production of novel plastic heat exchangers for HVAC, refrigeration, and energy-recovery applications and introduce it to the market within two years after the end of this project.

The main result will be tested and verified product competitive with the specific metal heat exchangers in market segment of low cost, low weight, corrosion resistance and recyclability

Information on the BUT websites