Textile Heat Exchanger - Development of a heat exchanger with a new cleaning concept, compact design, flexible shaping and improved acoustics based on tufted structures
To save heating energy, buildings are being built ever more airtight. Therefore, controlled ventilation is often used to ensure a sufficient supply of fresh air. It is possible to integrate a heat exchanger for heat recovery. The heat exchanger transfers the heat of the exhaust air to the cold fresh air, so that ventilation losses are reduced. In most designs, the heat is transferred through plate heat exchangers, which are difficult to clean. The aim of the project is the cost-effective production of air-to-air heat exchangers with a new cleaning concept, compact design, flexible shaping and improved acoustics.
Our solution approach is to use a textile structure made of thermally conductive yarns or thin wires to produce the heat exchanger element, which has a pile structure on both sides of a separating plane.
With the textile heat exchanger, the number of necessary sections can be reduced compared to a plate heat exchanger. This is achieved by increasing the effective area using "cooling fins" in the form of pole loops. The small number of sections means that the heat exchanger elements can be dismantled. This enables simple and effective cleaning. In addition, the use of textile structures implies further advantages in terms of acoustics and design. The yarns, which are formed as loops, transport the heat in the textile heat exchanger via an airtight textile separating plane. Due to the direct connection of the yarn between the upper and lower side of the separation plane, the tufting technique has economic and constructive advantages for this application compared to other textile manufacturing processes.
Within the scope of the project, questions regarding material selection as well as machine, textile and thermal engineering challenges in the production of a textile heat exchanger will be clarified.
The textile properties of the heat exchanger element result in new possibilities for the design of heat exchangers for living space ventilation. One example of this is the integration of the heat exchanger into roller shutter boxes.
Figure: Textile heat exchanger element for heat recovery in controlled residential ventilation
The double loop structure was successfully realised by developing a back stitch lift. There is the possibility of scaling up this approach to a working width of industrial tufting machines of 5 m. In addition to the production of textile heat exchanger elements for decentralised residential ventilation, possible areas of application for this technology are other applications for heat transfer. If adapted base materials and structures are used, other areas of application for tufted double loops are possible, for example in the field of geotextiles.
The basic effect of textile heat exchanger elements made of metallic yarns was demonstrated based on the measured heat quantities transferred. The need for further research is derived from the analysis of the results. The aim of this work should be to improve the ratio between the mass of yarn used and the amount of heat transferred and thus reduce the manufacturing costs.