Project details



Energy efficient heat exchangers for HVAC applications

Start date: 01.10.2012

Duration: 36 months

Coordinator: Jacob ask Hansen

Budget: 4.1 M€


The objective of the EnE-HVAC project has been to develop novel nanotechnological approaches to achieve a significant reduction of the energy requirements for HVAC (heating, ventilation and airconditioning) systems. To achieve these savings, the EnE-HVAC project approaches all aspects of the HVAC system, developing solutions for improving heat transfer and transport throughout the whole system.

During the project, three technological approaches have been brought into play to enhance the overall energy efficiency of the complete HVAC systems.

Nanotechnological coatings limiting ice formation on HVAC systems

Frost formation on the surface of heat exchangers is a great challenge for the energy efficiency. Periodic defrosting by heating is required, but that consumes energy. A heat pump requires app. 13% of the total energy consumption of the heat pump for periodic defrosting at ambient temperatures below +7°C. Even if frost formation is not prevented completely, longer cycles between de-icing intervals would save energy significantly.

Through this project, super hydrophobic coating systems have been developed to slow the formation and spreading of ice on cooled surfaces. These systems have been developed through extensive laboratory development at Danish Technological Institute (DTI) and Tekniker IK 4, in close collaboration with Luve S.p.A., EXHAUSTO A/S and DVI A/S. Further testing of these surfaces in full-scale heat exchanger systems at EXHAUSTO and Luve have shown a significant delay of ice formation.

Nanostructured surfaces for increased heat transfer in refrigeration systems

When improving heat exchanger efficiencies of evaporators and condensers, it is important to look at how the boiling behaviour of these systems can be optimised in order to give a decreased energy consumption.

Through this project, nano- and microstructured surfaces as well as sol-gel based surface coatings have been developed to increase the boiling efficiency of refrigerant-based heat exchanger systems, and the overall performance and energy efficiency of these systems has been increased. Through laboratory development at DTI and Tekniker IK4, surfaces showing a significant improvement in boiling heat transfer for both CO2 and NH3 was developed. These systems were scaled for application on full-size heat exchangers at Vahterus Oy and an increased efficiency of 8% was shown for NH3 systems.

Development of nanofluids for increased efficiency of brine systems

The objective of this work was to develop nanofluids to improve the heat transfer across heat exchanging surfaces. Nanofluids are nanoscale colloidal suspensions containing condensed nanomaterial in a fluid. The potential of doping refrigerants with nanoparticles to increase the heat transfer from a heat exchanger surface to the refrigerant has been investigated. Development on nanodiamonds from Carbodeon Oy have been made to enable suspension of these in the refrigerants CO2 and NH3. For NH3 surface modifications were found to enable this suspension, but unfortunately no significant effects were observed for the boiling behaviour. In addition, nanoparticle doped brine systems were investigated but had no significant effect on the heat transfer.

To support the approaches above, ESI software Germany GmbH has developed simulation models for prediction of performance on heat exchanger systems with improved surfaces and/or refrigerants.

List of achievements

Lessons learnt


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