Study on the deposition characteristics of crystallization fouling in rib channel based on CFD 3D dynamic mesh technology

Study on the growth characteristics of local particulate fouling in heat transfer channel based on dynamic mesh technology

The subject of this paper is mainly focused on the development and control of the double folium and trifolium lobe pump profiles by using the principle of involute engagement and use CAD to get an accurate involute profile. We use the standard k-ε turbulence model and PISO algorithm based on CFD software FLUENT. The dynamic mesh and UDF technology is introduced to simulate the interior flow field inside a lobe pump, and the variation of interior flow field under the condition of the lobe rotating is analyzed. We also analyse the influence produced by the difference in lobes, and then reveal which lobe is best. The results show that dynamic variation of the interior flow field is easily obtained by dynamic mesh technology and the distribution of its pressure and velocity. Because of the small gaps existing between the rotors and pump case, the higher pressure area will flow into the lower area though the small gaps which cause the working area keep with higher pressure all the time. Both of the double folium and trifolium are existing the vortex during the rotting time and its position, size and shape changes all the time. The vortexes even disappear in a circle period and there are more vortexes in double folium lobe pump. The velocity and pressure pulsation of trifolium pump are lower than that of the double folium.

Numerical simulation of CaSO4 crystallization fouling in a rectangular channel with vortex generators

Ash deposition characteristics of flue gas across a tube using the Eulerian multiphase model with dynamic mesh technique

Characterization of natural organic matters using flow field-flow fractionation and its implication to membrane fouling

Fouling characteristics analysis and morphology prediction of heat exchangers with a particulate fouling model considering deposition and removal mechanisms

Enhanced heat transfer tubes are widely used in heat exchangers, and the characteristics of heat transfer and fouling are focused.Four kinds of tubes were tested at different temperature, initial concentration and velocity to study heat transfer and fouling characteristics.The results show that: the initial growth rate and final fouling resistance of fouling resistance decreases as velocity increases.But the influence of velocity gradually reduces when velocity is higher than some certain value.The fouling layer is compact and thin at high velocity, but thick and fluffy at low one.The fouling resistance does not always increase when concentration increases.Although the initial concentration is different, the concentration is similar after 8 hours.The final fouling resistance is similar at different concentration, but the morphology is different.The fouling resistance increases as the temperature increases.There is no fouling on the groove of ribs at low temperature, but opposite at high temperature.There is most fouling on the SOFT, more than PT.The scale inhibition performance of WSOFT is best and lest fouling.The NSOFT has a similar fouling resistance with PT.

In present study, the characteristics of particulate fouling, crystallization fouling and their composite fouling for the convergent-divergent tube were investigated. The comparative fouling experiments were carried out between the convergent-divergent tube and its corresponding plain tube. The experimental results show that the convergent-divergent tube has an advantage both in heat transfer performance and in antifouling performance over the plain tube.

The comparative experiments on CaCO3 crystallization fouling on brass, copper and stainless steel 304 and 316 at different pH at 35°C were carried out. The growing curves of fouling were got by direct weighing after static reaction experiments, and the morphology of crystals at different conditions was obtained by scanning electron microscope (SEM) and the parameters such as polymorphism, crystal size and so on were got, so the growing characteristics of CaCO3 crystallization fouling were known. The experimental results show the mass of crystallization fouling on stainless steeSubscript textl surfaces are almost equal and increasing a little when pH increased, but the mass of fouling on brass and copper surfaces are close and far less than on stainless steel and increasing a lot when pH increased; not only the homogeneous nucleation rate in bulk solution and heterogeneous nucleation rate on metal surface are increased to generate more new crystal nuclear but also square aragonite and calcite are formed more by higher pH, so the mass of metal surfaces is more and the phenomenon is more obvious that single crystal has a size extremum by higher pH.

Parametric study on fouling mechanism and heat transfer characteristics of tube bundle heat exchangers for reducing fouling considering the deposition and removal mechanisms

Rate-distortion-optimized predictive compression of dynamic 3D mesh sequences

For analysis of the flow field of torque converter's start operating performance, the paper established a mathematical model and simulated the numerical value of YJ series hydrodynamic torque converter. In view of the partial impact fluid and cavitation phenomenon in processes such as multiple flow area coupling algorithms the sliding mesh method cannot achieve the flow parameters real-time transfer problems between the impellers. The model, established by dynamic mesh technology, set pump wheel and turbine blade for the rotating part of dynamic mesh, pick up each iterative step of pump wheel and turbine by the size of moment through the function, and deposited it into the text file. Through calculating the changes of text data, we can judge whether the result is stable. Take the comprehensive consideration of the stability, accuracy and efficiency during the calculation, set pressure-velocity coupling algorithm as the SIMPLE algorithm, set spatial discrete format as the first order up stream format, set turbulence model as the RNG K-ε model, and realize the turbulence flow transient calculation of the hydrodynamic torque converter. Numerical simulation by the calculation was compared with the moment data from the experiments, the results show that the model established by dynamic mesh technology is more accurate and reliable. Thereafter, the pump wheel's start-up rotate speed increased from 0 to 1000r/min gradually, then remained constant. Through the analysis, we concluded as follows: the pump wheel 's moment increased gradually, the value of the turbine's moment was small, the flow increased slowly from the positive value in the early stage. Then the turbine's moment increased gradually, the flow changed into negative value until stable.

A waste heat exchanger fly ash particle deposition model with dynamic mesh and random function method

DEM simulation and fractal analysis of particulate fouling on coal-fired utility boilers' heating surfaces

Hybrid high-temperature fouling and erosion characteristics of gas-particle flow around heating tube via CFD-DEM