On the Vortex-l mailing list, Jed Rothwell has posted a link to a paper that was presented at the ICCF23 conference last year (held online due to the coronavirus pandemic) in which the authors report excess heat production in a system employing cavitation in a mechanical heat exchange system.
The title is “Excess Energy from Heat-Exchange Systems”
From the abstract:
In ICCF22, we presented a vapor compression machine (VCS-1) using a 2.75RT freon compressor (Figure 1) which can produce excess energy . The hot refrigerant vapor from the compressor (around 150°C) is used to heat the water flowing through a tiny passage of a triple-pipe heat exchanger. This may cause a violent cavitation of water. The machine was modified furthermore and tested for two years since then. The calorimetric method for COP measurement was improved. The COP inside the steam generator is defined as the heat carried away by water (Qwnet) divided by the net heat input (Wt – QL), denoted as COPx . This is used as the criterion to determine the possibility of excess energy generation. If the measured COPx was greater than 1, then the cavitation-induced low-energy nuclear reaction (LENR) might occur. The test shows that the maximum COPx reaches 1.97 (Figure 1) and COPx increases with decreasing inlet water temperature.
The paper is very short, only one page long, but a video of the presentation by Bin-Juine Huange of the Department of Mechanical Engineering at Taiwan University is here, along with his slide show:
He discusses not only the excess heat production, but also the destructive effects of the cavitation on copper foil. He explains that he believes that a low energy nuclear reaction might occur in the system as a result of large collapsing gas bubbles cause by the cavitation.