Innovation: Low-temperature heat exchangers based on thermally-conducting polymer nanocomposites

Last update: 29.06.2013
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Keywords: 
metal nanoparticles, carbon fibres, polymer, agriculture, heat exchanger, materials technology, surface treatment, carbon nanotubes, nanotechnology research, nanotechnology applications, other energy topics, nanotechnology and nanosciences, polymers
Low temperature heat recovery is often limiting the energy efficiency of industrial processes. Low temperature differences imply large exchange surfaces which are unfeasible from the economic (expensive metal are needed to withstand the presence of condensates) and technical (too large volumes for the specific application contexts) viewpoints. The present project aims at developing nanofilled-polymer-based heat exchangers enabling: i) effective heat conductivity due to the percolation network of carbon or metal fillers; ii) cost reduction compared to metal materials (stainless steel, Cu-alloys,

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The research activities aimed at producing two heat exchanger prototypes for the two end-uses following a progressive three-stage path:
- Development of fillers and compounds in which a wide range of polymers (PP, PVDF, PA66) and fillers (graphite fibres, carbon nanotubes (CNTs), metal coated nanoparticles or fibres) were modified by the compounding of conductive particles and characterised by an intensive testing and characterisation campaign. A fundamental modelling work was also developed for the design of the optimal microstructure of the heat-exchange material.
- Tailoring of polymer processing techniques (injection moulding, compression moulding, extrusion). This experimental and modelling work line was carried out in close contact with the design of innovative heat exchanger.
- Manufacturing and testing of proof-of-concept heat exchangers for the given end-uses.

A virtual platform based on a multi-level model approach (fundamental modelling of heat transfer, computational fluid dynamics (CFD) design of the THERMONANO heat exchangers, system modelling for the virtual implementation of the heat exchangers in various processes) will allow to drive materials developments and evaluate the impact of the developed technologies in various application contexts.

Polymer-filler compounds were developed by NCYL, CEA, Polito, PISAS and SGLC following different strategies, while thermal characterisation of materials have been carried out at TUBAF. Development was completed at the end of the first year, with the development and selection of both CNTs and metal-coated particles. In this task, Nanocyl experimented the possibility to change some of the parameters of the chosen CNTs by modifying the residual content and its nature, the level of defects, the length and the presence of functional groups but also creates other types of CNT materials. Besides CNT, metallisation of different substrates of various shapes was carried out by PISAS. Elected particles included glass flakes, wollastonite nanofibres, polyamide flakes and cellulose fibres. In all the cases, silver was used for metallisation due to many advantages compared to other metals, including high conductivity, stability, reasonable price of the precursor, and simple coating procedure.

As a first activity, selected conductive particles (both CNTs and metal coated particles) were included in thermoplastic polymers (PP, PVDF, PP) as a first screening of thermal conductivity properties obtainable. Detailed studies were performed investigating full concentration range of the filler as well as degree of dispersion of the conductive particles.

Both CNT and metal nanoparticles showed improvements in term of thermal conductivity lower than expected, when used alone at low loading: for instance, conductivity of about 1 W/mK was obtained when using as much as 20 % CNTs. On the other hand, relatively high loading of metal coated particles was needed to reach significant conductivity of polymer composites (e.g. 2 W/Km for composites with filler concentration 60 wt %). Such high loadings were considered to be insufficient taking into account increasing stiffness (resulting in brittle material) and viscosity (leading to higher energy consumption during processing and expected problems regarding final look of the products, especially if injection moulding would be applied as preferred technology). Therefore, after thorough discussion the option of metal coated particles was abandoned and the experiments with the metallised particles did not continue.

The main bottleneck to the efficiency in thermal exchange was identified into the contact resistance between adjacent nanoparticles, which is associated to a drop in temperature at every contact point between two conductive particles. A detailed discussion of this topic is reported in one the scientific publication held in this project (Z. Han, A. Fina: Thermal conductivity of carbon nanotubes and their polymer nanocomposites: A review. Progress in Polymer Science 2011, 36, 914-944).

New designs were developed for the polymer nanocomposites heat exchanger, taking into account the ease of processing of polymers into complex shapes. Details of the designs cannot be given in the public report. These three processing technologies were selected based on a detailed evaluation of cost-effectiveness and performance of the heat exchange surfaces obtainable by several polymer processing technologies. No details about processing conditions can be provided in the public report, due to the intellectual property (IP) policy of the project.

Collaboration sought: N/A

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This innovation is the result of the project

Title: Low-Temperature Heat Exchangers Based On Thermally-Conducting Polymer Nanocomposites

Acronym: 
THERMONANO

Runtime: 
01.01.2009 to 30.06.2012

Status: 
completed project

Organisations and people involved in this eco-innovation.

Please click on an entry to view all contact details.

POLITECNICO DI TORINO

(Italy)

Role in project: Project Coordination

Contact person: Prof. SARACCO Guido

Website: http://www.polito.it

Phone: +39-011-0904618

Contact

A.S.T.R.A. REFRIGERANTI S.P.A.

(Italy)

Contact person: Dr. PAOLI Giovanni

Phone: +39-0131354811

Contact

COMMISSARIAT ENERGIE ATOMIQUE CEA

(France)

Contact person: Mr. HUSSENOT Yves

Website: http://www.cea.fr

Phone: +33-438783226

Contact

NANOCYL SA

(Belgium)

Contact person: Mr. CLAES Michael

Website: http://www.nanocyl.com

Phone: +32-71-750392

Contact

ONNI-STAMP SRL

(Italy)

Contact person: Dr. GORIA Alessio

Website: http://www.onnistamp.com

Phone: +39-0141943110

Contact

SGL CARBON GMBH

(Germany)

Contact person: KESSLER Herbert

Phone: +49-8271832343

Contact

SIMONA AG

(Germany)

Contact person: Dr. FRINGS Wolfgang

Website: http://www.simona.de

Phone: +49-675214381

Contact

STAROM GRUP S.R.L.

(Romania)

Contact person: Mrs. GRAMA Silvia

Website: http://www.starom.ro

Phone: +40-210318057490

Contact

TECHNISCHE UNIVERSITAT BERGAKADEMIE

(Germany)

Contact person: Prof. GROSS Ulrich

Website: http://tu-freiberg.de

Phone: +49-3731393941

Contact

USTAV POLYMEROV - SLOVENSKA AKADEMIA VIED

(Slovakia)

Contact person: Prof. CHODAK Ivan

Website: http://www.polymer.sav.sk

Phone: +421-254771603

Contact