Hollow Fiber Heat Exchangers with Reduced Permeability for Smart Cities

© EIG Concert Japan
  • Dr. Frantisek Miksik - Nagoya University - Japan
  • Dr. Erik Bartuli - Brno University of Technology - Czech Republic
  • Dr. Jaroslav Longauer - Slovak Academy of Sciences - Slovakia
  • Dr. Kyaw Thu - Kyushu University - Japan

Heat exchangers are crucial in all heat transfer processes including cooling and heating, which directly impacts carbon footprint. Polymeric hollow fiber heat exchangers have approximately seven times lower CO2 footprint than aluminum heat exchangers making them indisputably more environmentally preferable. Furthermore, due to lower density and more flexible design the exchangers made of hollow fibers can dramatically reduce the weight of the system, typically more than 50%, making them more efficient, energy and fuel-saving in automotive and aerospace as well in buildings as wall cooling and heating radiant systems for advanced air conditioning applications. Therefore, in relation to electric vehicles, smart urban mobility, and smart cities, this technology is an important upgrade that strongly supports the aim of the Solutions for Carbon-Neutral Cities joint call. This project follows the objectives of two major applications and aims to develop highly innovative heat exchangers using polymeric hollow fibers for electric vehicles, and radiant space cooling/heating systems in modern buildings.

Our design uses bundles of polymeric hollow tubes with a diameter of about 1 mm and a wall thickness of roughly 10% of the diameter. Thanks to our special manufacturing process, the hollow fibers can withstand high pressures (>4MPa), however, the very thin polymer wall presents a challenge of increased cooling medium permeation (leak) through the fiber’s walls. Because, effective deployment of the new advanced heat exchangers requires long and reliable operational conditions, this project aims to find innovative solutions to address this issue by various methods such as post-process surface treatments and co-extrusion manufacturing techniques.  They key will be to find a sustainable way, keep the advantages of low CO2 footprint and high efficiency while allowing for a long operational time and high durability. The goal is to reduce the permeability of the fiber walls below 5×10-6 m3m-2year-1 at a 2 bar pressure and an operational temperature of 80 °C. Such rate would represent about 0.5% loss of the cooling fluid in a regular car cooling system per annum making it comparable to current systems. The development of a new modular system for advanced high-area space heating/cooling, as the second major application, will be developed in parallel as a brand-new application expanding the usage of the newly formulated advance polymeric hollow fibers.

In this project, we will focus on measuring permeability, assessing heat transfer efficiency, and reevaluating CO2 emissions compared to traditional aluminum heat exchangers with a necessary discussion about end-of-life treatment and recycling. Because hollow fibers are used also in water treatment for water filtration and freshwater production (the second aim of the Joint Call), the results of this project in terms of adjusting the permeability of hollow fibers will provide additional knowledge for a variety of applications far beyond the scope of this project.

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