Analogously to the formation of nano-cracks in solid matter, the implosion of nano-bubbles in liquid media (water solutions of iron salts) due to cavitation phenomena produces TeraHertz phonons that cause, also in this case, anomalous nuclear reactions. In the present chapter, some calorimetric tests performed at Politecnico di Torino by a hydrodynamic cavitation pilot-plant are described. The diameter of the bubbles produced by hydrodynamic cavitation and the temperature increments are monitored by means of the Phase Doppler Anemometry technique and by thermocouples, respectively. These experiments suggest that the energy emitted per each imploded nano-bubble is approximately constant despite the different bubble geometries, populations, and temperatures. The effect of the different initial concentrations of iron salts on the temperature versus time evolution is thoroughly evaluated. The performed tests show an increment in the final temperature by increasing the initial concentration of iron salts until the optimal concentration of 20 ppm is reached. Beyond that limit, the water solution saturation occurs and a decrement in the final temperature is detected.