Advanced project on study of system hahumna
- 1. VOID FRACTION AND BUBBLE DISTRIBUTION MEASUREMENT IN BUBBLE COLUMN REACTOR BY PRANESH KUMAR SAHA BME-IV 001511201113 UNDER GUIDANCE OF: SOURAV SARKAR
- 2. BUBBLE COLUMN REACTOR •A two phase reactor operating with liquid in bulk and gas bubbles •Used widely in fields like biochemical, metallurgical and petrochemical •Design parameters: Specific gas-liquid interfacial area, Sauter mean bubble diameter, heat transfer coefficient, physio-chemical properties and gas hold-up •Gas bubble sizes and their holdups, among other parameters, is required for proper operation, modeling and optimization of multiphase reactors
- 3. WHY A NEW ALGORITHM & EXPERIMENTAL SETUP •Past experiments have used high speed camera which are expensive •Expensive setups are not portable and reproducible easily •Main motive was to develop a fast and computationally inxpensive algorithm that can work on images from ordinary digital camera •Setup consists 2 rotometers, one glass tube ,an open air circuit and closed water circuit •Only the air circuit is used in the experiment •LED Light and paper diffuser
- 4. FLOW REGIMES
- 5. ALGORITHM Input Conversion to grey Image segmentation Morphological Opening Image Thinning Branch Removal & Marking End Point Extraction Image Compression Convexity Calculation Distance Based Grouping Fitting and Output Main steps in the algorithm are: 1. Resonace based segmentation with adaptive threshold 2. Thinning By Zhang Suen algorithm 3. Unwanted Branch Removal 4. Marking of separate branches 5. Convexity based grouping and distance based selection 6. Curve fitting
- 6. Images
- 7. RESULTS & DISCUSSION • Starting from bottom clockwise the volume flow-rates are .256 and .446 lit/min • Equally distributed in low volume flow rate of .25 • As volume flow rate increases number of smaller bubbles increase • The maximum bubble diameter also increases • The flow is
- 8. RESULTS & DISCUSSION(cont.) The flow rates are .566, .633, .737 and 1.030 l/mim The first three are tranisent and 1.03 has reached heterogenous flow
- 9. Results & Discussion(cont.) • The top graph shows flow rate of 1.4 while the bottom one shows 3.11 l/min • It is very evident from the images that the flow has entered churn-turbulen or heterogenous flow regime
- 10. RESULTS & DISCUSSION(cont.) • The number of bubbles first increase to a maxima and then start decreasing • Void fraction shows a general increasing trend with a local minima at 1.4 l/min and also number of bubbles decrease at 1.4l/min • This is very important as it marks the onset of churn turbulent zone. • The values of void fraction are not accurate as only bubble rich zones were analysed and total cylinder volume was not considered
- 11. CONCLUSION • The project aimed at developing a new algorithm for bubble detection and quantification from low quality images(as compared to others). • The results conform suitably with existing literature showing that the algorithm works accurately with room for improvements. • A distinct trasient flow region can be seen by the presence of few large sized bubbles formed by coallesence of smaller ones