THERMONANO

LOW-TEMPERATURE HEAT EXCHANGERS BASED ON THERMALLY-CONDUCTING POLYMER NANOCOMPOSITES

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 Obiettivo del progetto (Objective)

'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,…); iii) design flexibility for an intensive volume exploitation; iv) superior corrosion resistance; v) promotion of the highly effective drop condensation with hydrophobic polymers. Three main application areas are devised: 1. Intercoolers increasing the efficiency of large diesel engines, where heat conductive plastics can provide a cheaper alternative to Cu-alloys when seawater is used as the cooling media (e.g. large naval engines or power plants close to sea side). 2. Heat recovery systems from combustion flue gases acting below 300°C, where commercial metal-based systems loose cost-effectiveness. 3. Application in the chemical and process industries where harsh chemicals or corrosive environments have to be faced. The project is divided into three main work lines: i) development of compounds in which a range of polymers (nylon, PET,…) and fillers (carbon fibres, carbon nanotubes, metal coated nanoparticles, …) will be considered; ii) tailoring of plastic forming techniques (injection moulding, pressing, extrusion); iii) manufacturing & testing of up to two proof-of-concept heat exchangers. The partnership includes two Universities (POLITO-I, TUBAF-D), two research centres (CEA-F, PISAS-SK), three SMEs (Astrarefrigeranti-I, Nanocyl-B, Starom-RO) and two large companies (Simona-D, SGL Carbon-D) selected for their specific expertise to undertake the above challenges.'

Introduzione (Teaser)

Heat exchange is critical to efficient production in most industrial processes. Scientists are developing novel cost-effective and high-performance materials for heat exchangers well suited to low temperature differences.

Descrizione progetto (Article)

Heat exchangers literally move heat from one substance to another. They are used to add or remove heat from processes. Heat exchangers come in many forms but most consist of a solid separating two fluid media. When the temperature difference between the two media is low, ever larger exchange surface areas are required for efficient heat exchange. However, large surfaces are often not feasible either economically or technically, or both.

Employing novel nanomaterials, scientists working on the EU-funded project 'Low-temperature heat exchangers based on thermally-conducting polymer nanocomposites' (Thermonano) are solving this problem, which limits process efficiency. Exchange materials made from nanomaterial-filled polymers are being designed for effective heat conductivity (more conductivity per unit area means less area for the same conduction) and cost reduction compared to conventional metals. Additional expected benefits include design flexibility for volume exploitation, excellent corrosion resistance and highly effective drop condensation.

Scientists developed and selected a number of polymer materials and nanofillers during the first year, including carbon nanotubes (CNTs) and metal-coated nanoparticles (NPs). Scientists experimented with modifying CNTs to determine the effects of certain parameters. Silver metallisation (build up of a blanket layer of metal) of substrates including glass flakes, nanofibres (wollastonite), polyamide flakes and cellulose fibres was also performed to produce metal-coated NPs for fillers.

Selected conductive particles including both CNTs and metal-coated NPs were incorporated into thermoplastic polymers (those that can be remelted and reprocessed over and over again). Detailed characterisation studies led to a deeper understanding of the effects of metal NPs and their concentration within polymers. Contact resistance between adjacent NPs leading to a drop in temperature at every contact point was found to be the main factor impeding efficient thermal exchange.

Thermonano has developed novel designs for polymer nanocomposite-based heat exchangers suited to low temperature difference-exchange. Commercial exploitation of Thermonano concepts may help increase the process efficiency of a number of relevant industrial applications. These include intercoolers for large diesel engines, heat recovery from combustion flue gases, and chemical processes with harsh chemicals or corrosive environments.