Experimental analysis of direct contact condensation during vertical injection of steam on subcooled water pool

Experiments have examined the phenomenon of direct contact condensation when steam is injected vertically into the subcooled water pool. The investigation is carried out by varying the steam mass flow rate and submergence depth of the steam injection pipe in the range of 10-50 kg/hr and 1-13 cm, respectively. The behavior of the bubble that appeared at the pipe outlet, transient heat transfer coefficient, pressure variation in the steam injection pipe, and its associated frequency have been analyzed. The images captured by high speed-camera showed different bubble shapes. The overall cycle time of bubble evolution has decreased with an increase in the mass flow rate and increased with an increase in the pipe submergence depth. The time averaged heat transfer coefficient increased with an increase in the mass flow rate and decreased with the rise of the pipe submergence depth. The pressure drop within the steam injection pipe shows the parabolic variation with an increase in the mass flow rate and is slightly influenced by the submergence depth due to changes in interfacial structures within the pipe. The peak frequency associated with the pressure has increased with an increase in the mass flow rate and decreased with an increase in the pipe submergence depth at higher mass flow rates. The FFT (Fast Fourier Transform) of interfacial area of the larger bubble at the pipe outlet shows that the first peak frequency lies between 0.5-5 Hz, and the second peak frequency lies in the range of 25-30 Hz.