Yushan Luo

Experimental Investigation of Two-Phase Flow Instabilities in Low-Mass-Flux Water Wall Tubes of Supercritical Circular Fluidized Bed Boilers

For the purpose of disclosing the hydrodynamic flow characteristics, under the low mass velocity conditions of the 600-MW supercritical circular fluidized beds boilers, experimental studies on instability of two-phase flow in parallel vertical internally ribbed tubes were conducted. Two kinds of oscillations, pressure-drop oscillation and density-wave oscillation, have been observed. In the range of test parameters the effects of pressure, mass flux, inlet subcooling, compressible volume, exit throttle, and asymmetric heat flux to the two-phase instability were explored and analyzed. Indications from experiment data are: To increase system pressure, mass flux and inlet subcooling will intensify the stability of water wall tubes. To increase exit throttle will intensify the instability of water wall tubes. The bounding pressure and bounding mass flux of density-wave oscillations and the bounding pressure of pressure-drop oscillation have been obtained. Based on the results of testing and using a homogeneous model, the threshold relational expressions of instability were obtained. The results may be used for the design and safe operation of parallel vertical rifled water wall tubes of supercritical circular fluidized beds boilers.

Experimental study on boiling heat transfer and two-phase frictional pressure drop characteristics of glycol-water solution in a vertical porous surface tube

Although much research has been conducted on investigating the flow boiling heat transfer of low saturation temperature refrigerants, there are few experimental data and theory about the flow boiling heat transfer of high saturation temperature organic mixture which exists widely in the petrochemical industry. To investigate the characteristics of flow boiling heat transfer of high saturation temperature organic mixture, experiments of glycol-water solution flow boiling in a vertical porous surface tube and a vertical smooth tube are conducted. Test tubes are uniformly heated by electrical current with a heated length of 2,000 mm. The mass flux in the experiment ranges from 500 to 1,500t⋅h−1 and the heat flux on test tubes ranges from 10 to 40 kW⋅m−2. The flow boiling heat transfer coefficients and two-phase frictional pressure drops of the two types of tubes are obtained and compared. The results indicate that: the flow boiling heat transfer coefficient in the porous surface tube is 3.8∼5.7 times of that...

Experimental investigation of two‐phase flow pressure‐drop type instabilities in parallel vertical internally ribbed pipes at low mass flow rate

The research covers the experimental investigation of two‐phase flow instabilities in parallel vertical internally ribbed pipes at low mass flow rate in the high‐pressure steam‐water test loop. The tested tube is an outlet diameter of 28.6 mm and a wall thinkness of 5.8 mm. The pressure‐drop type oscillations are found in the experiments. The effects of pressure, mass flow rate and inlet subcooling on instabilities are studied. The results show that the boundary heat flux of pressure‐drop type oscillations increase with increase of inlet pressure, mass flow rate and inlet subcooling. It is found that sysetem pressure, inlet subcooling and mass flow rate have great effects on amplitudes and periods of two‐phase flow instabilities. In addition, it is found that the effects of pressure on periods of pressure‐drop type oscillations represent two different trends in the test. When pressure is lower then 4 Mpa, the periods of pressure‐drop type oscillation increase with pressure increasing, but when pressure is...