To estimate an influence of velocity on thermodynamic effect, we conducted experiments, in which inducer rotational speed was changed in liquid nitrogen. The experiments in liquid nitrogen and in cold water allowed us to estimate the amplitude of thermodynamic effect. In the experiment with lower rotational speed, the suction performance was improved in liquid nitrogen. The cavity length at lower rotational speed was shorter than that at higher one at the same cavitation number. Thus, we have confirmed that the degree of thermodynamic effect depends on the rotational speed as a suppression of cavity length. The temperature depression of liquid nitrogen was estimated from the comparison of cavity length between in liquid nitrogen and in cold water. We found that the amplitude of temperature depression became smaller when the rotation speed was lower. In addition, from arrange data using modified non-dimensional thermodynamic parameter Σ^*_<mod>, the effect of nonlinearity of vapor pressure/temperature curve should be considered to evaluate the thermo-dynamic effect especially in the case of higher temperature and rotational speed.
