Abstract: The fluid flow of hydraulic turbine inserted heat exchanger is analyzed. According to the moment of momentum theorem, the rotational moment M and the resistant moment Mf of hydraulic turbine are obtained. M equals Mf while the hydraulic turbine rotates with constant speed by permanent flow. As a result, the rotational speed expression of hydraulic turbine is educed. The rotational performance of fifteen hydraulic turbines with different size is studied by experiments, and the result of the experiment is consistent with the theoretical expression. All the results show that the axial velocity vz of the flow and the thread pitch H of the vane are the main influencing factors in the rotational speed n of the hydraulic turbine. The greater the axial velocity is, the higher the rotational speed will be; the greater the thread pitch is, the lower the rotational speed will be. Besides, the dimensionless coefficient Rd , i.e. a token of hydraulic turbine, is put forward. Rd relates n, vz and H.

Key words: Heat exchanger tube, Hydraulic turbine, Rotational speed