where h0 is enthalpy of rivet layer inlet, Cf is the pressure loss coefficient determined from the result of present experiment as shown in Fig.6 for the rivet of 6.2 mm and Fig.7 for the mixed layer.
The measured pressure difference of the rivet layer was obtained from the experiments of several initial conditions. The predicted pressure difference is strongly affected with the pressure loss coefficient Cf. The Cf is determining to obtain the agreement between the prediction and the measurement. The Cf is 2.60 for the rivet of 6.2 ram and 4.54 for the mixed rivet layer. In the present calculation, rivet layer was divided into 20 nodings. The above equations (1), (2) and (3) are the basic equation to give local condition in the nodings of rivet layer. Shown in Fig.8 is the noding of rivet layer and the calculation procedure. The calculation starts at the rivet layer inlet condition. This calculation procedure assuming isoenthalpic and the saturated steam and water condition. The following Figs. 9 and 10 are the relation among predicted of pressure, quality, temperature, momentum and the distance from the rivet layer inlet for the rivet of 6.2 mm. The rivet layer inlet condition was following. The inlet hot water temperature was 81.5℃, the inlet pressure was 0.018 MPa and the flow rate of hot water was 4.5 kg/s. The quality and the momentum increase, the pressure and the temperature decrease toward to the rivet layer outlet. In the end of rivet layer, these changes were large. It is considered that the de-oiling and washing effect were done by the scrubbing effect of steam molecules. The scrubbing effect was strongly affected with the average momentum of the mixture of liquid and steam. It is considered that the better de-oiling and washing effect obtain at the large amount of momentum specially in the end side of rivet layer. Shown in Fig.11 is the map of the de-oiling condition in the relation of the average two-phase momentum and average hot water temperature in the rivet layer, rearranged from Fig.3. If the rivet layer de-oiling is made by the physical method due to the flowing mixture of water and steam in the rivet layer, the larger average momentum means the better de-oiling capability.
