Liquid-liquid direct contact heat exchange using a perfluorocarbon liquid for waste heat recovery: (Heat transfer characteristics obtained with perfluorocarbon droplets descending in a hot water medium)

This paper has dealt with the heat transfer characteristics of a liquid-liquid direct contact operation in which a Perfluorocarbon (PFC) liquid was released in a hot water stream, which was a low-grade heat source such as urban sewage, for the purpose of heat recovery from it. The paper reported on a set of experiments in which a PFC liquid (1 800 kg/m³ at 20°C) was continuously injected from a downward-facing single nozzle into a slow and upward flow of hot water and it was disintegrated into a lot of droplets and then they were heated from the ascending hot water. The experimental results revealed that the size distribution and flow behavior of the droplet ensembles exerted an influence on the coefficient of overall heat transfer between the droplet ensembles and hot water and also the temperature effectiveness for the droplet ensembles.