Heat transfer of bubbly flow on inner wall of annular channel

Experimental investigations of heat transfer from the heated wall to the two-phase bubbly flow were performed in vertical annular channel using air-water system. The IR-thermography and miniature temperature sensors were used to measure heat transfer coefficients. The influence of bubbles on heat transfer is shown in comparison with the case of single phase flow. The presence of bubbles in the flow leads to heat transfer intensification in the annular channel even for low void fractions

FORMATION OF PROTECTIVE FILMS OF OCTADECYLAMINE ON THE SURFACE OF CONSTRUCTION MATERIALS IN THE WATER-STEAM CYCLE AT FOSSIL POWER PLANTS

ABSTRACT One of the reasons of the degradation of operational efficiency of fossil power plants is corrosion that takes place in the water-steam cycle during operation or downtime. Filming amine octadecylamine (ODA) is one of the chemicals used for reduction of corrosion rate of construction materials during downtime. This chemical not only reduces corrosion rate, but also helps to remove deposits. The data on the ODA effect on the efficiency of removal of deposits from heat exchange surfaces during equipment layup are presented. After ODA application a change in distribution of impurities along the height of deposits was found. In particular, chlorides move from the metal surface to the upper deposit layer, resulting in decrease of the corrosion rate. Results of field tests at cogeneration fossil power plant indicate that the use of ODA for the equipment layup reduced tube failures and deposition rate in district water heaters and hot water boilers

Development, validation, and utilization of a competitive enzyme-linked immunosorbent assay for the detection of antibodies against Brucella species in marine mammals

A competitive enzyme-linked immunosorbent assay (cELISA) was developed by using a whole-cell antigen from a marine Brucella sp. isolated from a harbor seal (Phoca vitulina). The assay was designed to screen sera from multiple marine mammal species for the presence of antibodies against marine-origin Brucella. Based on comparisons with culture-confirmed cases, specificity and sensitivity for cetacean samples tested were 73% and 100%, respectively. For pinniped samples, specificity and sensitivity values were 77% and 67%, respectively. Hawaiian monk seal (Monachus schauinslandi; n = 28) and bottlenose dolphin (Tursiops truncatus; n = 48) serum samples were tested, and the results were compared with several other assays designed to detect Brucella abortus antibodies. The comparison testing revealed the marine-origin cELISA to be more sensitive than the B. abortus tests by the detection of additional positive serum samples. The newly developed cELISA is an effective serologic method for detection of the presence of antibodies against marine-origin Brucella sp. in marine mammals

Multiphase turbulence in bubbly flows: RANS simulations

The ability of a two-fluid Eulerian–Eulerian computational multiphase fluid dynamic model to predict bubbly air–water flows is studied. Upward and downward pipe flows are considered and a database of 19 experiments from 6 different literature sources is used to assess the accuracy of the model, with the aim of evaluating our ability to predict these kinds of flows and to contribute to ongoing efforts to develop more advanced simulation tools. The particular focus in the work described is on the prediction of multiphase turbulence due to its relevance in the modelling of bubbly flows in general, including bubble coalescence and break-up, and boiling at a wall. Overall, a satisfactory accuracy is obtained in the prediction of liquid velocities and void fraction distributions in all conditions, including upward and downward flows, and wall-peaked and core-peaked void profiles, when values of the bubble diameter are specified from experimental data. Due to its importance for the correct prediction of the turbulence level in these flows, a bubble-induced turbulence model is introduced, starting from an existing formulation. Source terms due to drag are included in the turbulence kinetic energy and the turbulence energy dissipation rate equations of the k-ε turbulence model, and optimisation of the turbulence source gives velocity fluctuation predictions in agreement with data. After comparisons with data, improvement in the predictions of other turbulence models is also demonstrated, with a Reynolds stress formulation based on the SSG (Speziale et al., 1991) pressure–strain model and the same bubble-induced turbulence model accurately predicting the two-phase flows and the anisotropy of the turbulence field. The same database is also exploited to evaluate different drag models and the advantages of including the effect of the bubble aspect ratio. Following experimental evidence, the model of Tomiyama et al. (2002) is used which assumes that the bubble shape is closer to spherical near a wall and employs a correlation to calculate the aspect ratio. An increase in the drag coefficient due to the higher aspect ratio increases the accuracy of calculated velocity profiles in the near-wall region, even if additional validation is still required due to the possible loss of accuracy in the pipe centre

LOCAL HYDRODYNAMIC CHARACTERISTICS OF TWO-PHASE GAS LIQUID FLOWS

Two-phase gas liquid flows in channels are investigated in the paper aiming at the obtaininig of main laws for the local hydrodynamics of gas liquid flows in tubes in a wide range of geometrical and regime parameters of a flow. As a result the complex of investigations of the local hydrodynamics of two-phase gas liquid flows in a wide range of conditions and regimes of a flow with the use of united methodologies of the investigation has been represented for the first time. The set of basic experimental data of the structure of a gas liquid flow has been obtained. This set may be used for the development of theoretical and engineering models of two-phase flows. The paper results may be used for the development of technological processesAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

The distribution of the gas phase in the bubble flow in the vertical assembly of 3×3 rods with gas injection from a single source

The work is devoted to an experimental study of the distribution of gas along the channel cross-section in the form of an assembly of vertical rods 3×3 in a square arrangement. The gas was introduced into the channel from the corner rod through a single capillary. Upstream, a local gas content sensor was attached to the the central fuel element simulator. The position of the sensor was changed by rotating the rod around its axis. The experiment was carried out at Reynolds numbers Re = 4500 - 9000 and flow rate gas contents of 2 - 4%

The distribution of the gas phase in the bubble flow in the vertical assembly of 3×3 rods with gas injection from a single source

The work is devoted to an experimental study of the distribution of gas along the channel cross-section in the form of an assembly of vertical rods 3×3 in a square arrangement. The gas was introduced into the channel from the corner rod through a single capillary. Upstream, a local gas content sensor was attached to the the central fuel element simulator. The position of the sensor was changed by rotating the rod around its axis. The experiment was carried out at Reynolds numbers Re = 4500 - 9000 and flow rate gas contents of 2 - 4%