Simple method improves HVAC heat exchangers by 500 per cent

Turbulent heat exchangers, which are widely used in heating, ventilation and air conditioning (HVAC) systems are fairly simple devices that use the natural movements of liquid to move heat. They consist of a hot surface, a cold surface and tank of liquid in between. Near the hot surface, the liquid heats up, becomes less dense and forms warm plumes that rise toward the cold side. There, the liquid loses its heat, becomes denser and forms cold plumes that sink back down toward the hot side. The cycling of water serves to regulate the temperatures of each surface.

The latest breakthrough is based on work carried out by Tsinghua professor, Chao Sun, who originally had the idea of using an organic component known as hydrofluoroether (HFE) to speed the cycling of heat inside this kind of exchanger.

HFE is sometimes used as the sole fluid in heat exchangers, but Sun suspected that it might have more interesting properties as an additive in water-based systems. Sun and his team experimented with adding small amounts of HFE and, after three years of work, were able to maximize its effectiveness in speeding heat exchange. The team showed that concentrations of around one per cent HFE created dramatic heat flux enhancements up to 500 per cent.