CFD Analysis Of A Double Suction Cooling Water Pump

Lecturepg. 11In 1991, four large double suction cooling pumps were installed at a chemical plant in Texas. Although these pumps met performance specifications on the test stand, they proved to be noisy when installed. Sound power levels greater than 93 dbA were observed. Pumping applications involving cooling water have been especially difficult to solve over the tears, due to the presence of dissolved air inherent in a cooling tower sump. Water that contains large amounts of dissolved air changes the apparent required net positive suction head (NPSH). In such applications, traditional correction techniques failed because the entire system was not analyzed, and the source of the noise generation could not be pinpointed. This paper deals with the steps involved with obtaining a solution to this problem. A computational fluid dynamics (CFD) analysis was performed on the pump and impeller. Initial investigation revealed that the impeller was not the source of the problem. The casing inlet was then analyzed. The model indicated the presence of separation in the suction nozzle, causing a flow distortion at the impeller eye. A unique guide ring was developed to minimize the flow separation. The CFD analysis was revised to reflect the new geometry, and a significant improvement in the flow was predicted. A prototype guide ring was manufactured and installed in one of the four pumps. Pressure profiles were obtained by experiment to validate the analyses. The results are discussed

Perinuclear localization and insulin responsiveness of GLUT4 requires cytoskeletal integrity in 3T3-L1 adipocytes

The GLUT4 glucose transporter resides mostly in perinuclear membranes in unstimulated 3T3-L1 adipocytes and is acutely translocated to the cell surface in response to insulin. Using a novel method to purify intracellular GLUT4-enriched membranes, we identified by mass spectrometry the intermediate filament protein vimentin and the microtubule protein alpha-tubulin as components of these membranes. Immunoelectron microscopy of the GLUT4-containing membranes also revealed their association with these cytoskeletal proteins. Disruption of intermediate filaments and microtubules in 3T3-L1 adipocytes by microinjection of a vimentin-derived peptide of the helix initiation 1A domain caused marked dispersion of perinuclear GLUT4 to peripheral regions of the cells. Inhibition of the microtubule-based motor dynein by brief cytoplasmic acidification of cultured adipocytes also dispersed perinuclear GLUT4 and inhibited insulin-stimulated GLUT4 translocation to the cell surface. Insulin sensitivity was restored as GLUT4 was again concentrated near the nucleus upon recovery of cells in physiological buffer. These data suggest that GLUT4 trafficking to perinuclear membranes of cultured adipocytes is directed by dynein and is required for optimal GLUT4 regulation by insulin