CFD Simulation of the Slot Jet Impingement Heat Transfer Process and Application to a Temperature Control System for Galvanizing Line of Metal Band

Wang²,

et al. 2021

JMSE

The instability of the no-load working condition of the pump turbine directly affects the grid connection of the unit, and will cause vibration and damage to the components of the unit in severe cases. In this paper, a three-dimensional full flow numerical model including the runner gap and the pressure-balance pipe was established. The method SST k-ω model was used to predict the internal flow characteristics of the pump turbine. The pressure pulsation of the runner under different operating conditions during the no-load process was compared. Because the rotation speed, flow rate, and guide vane opening of the unit change in a small range during the no-load process, the pressure pulsation characteristics of the runner are basically the same. Therefore, a working condition was selected to analyze the transient characteristics of the flow field, and it was found that there was a high-speed ring in the vaneless zone, and a stable channel vortex was generated in the runner flow passage. Analyzing the axial water thrust of each part of the runner, it was found that the axial water thrust of the runner gap was much larger than the axial water thrust of the runner blades, and it changed with time periodically. It was affected by rotor stator interaction. The main frequency was expressed as a multiple of the number of guide vanes, that is, vanes passing frequency, 22fn. During the entire no-load process, the axial water thrust of the runner changed slowly with time and fluctuated slightly.

Section: ∂(ρK) ∂Tmentioning

confidence: 99%

Analysis of Internal Flow Characteristics of a Startup Pump Turbine at the Lowest Head under No-Load Conditions

Wang²,

et al. 2021

JMSE

“…Flow patterns play a vital role in the transport properties (heat and mass transfer) in non-reactive and reactive systems. Conventional equipments like agitated vessels, rotating discs, impinging jets (for mass transfer) [1] and jet impinge heat exchange mechanisms used for cooling gas turbine components, heat treatments, [2] preheating in glass manufacturing [3] and many other conventional heat transfer equipments [4] have order of magnitude lower transport properties than those offered by microchannels. Flow patterns are formed due to interplay between inertial and surface tension forces.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamics of Liquid-Liquid Flows in Micro Channels and Its Influence on Transport Properties: A Review

Ganguli

Pandit

2021

Energies

Hydrodynamics plays a major role in transport of heat and mass transfer in microchannels. This includes flow patterns and flow regimes in which the micro-channels are operated. The flow patterns have a major impact the transport properties. Another important aspect is the pressure drop in micro-channels. In the present review, the experimental and Computational Fluid Dynamics (CFD) studies covering all the above aspects have been covered. The effect of geometrical parameters like shape of channel, channel size, material of construction of channels; operating parameters like flow velocity, flow ratio and fluid properties have been presented and analyzed. Experimental and analytical work of different pressure drop models has also been presented. All the literature related to influence of flow patterns on transport properties like volumetric mass transfer coefficients (VMTC) and heat transfer coefficients (HTC) have been presented and analyzed. It is found that most works in Liquid-Liquid Extraction (LLE) systems have been carried out in slug flow and T-junctions. Models for coupled systems of flow and mass transfer have been presented and works carried out for different coupled systems have been listed. CFD simulations match experimental results within 20% deviations in quantitative and qualitative predictions of flow phenomena for most research articles referred in this review. There is a disparity in prediction of a generalized regime map and a generalized regime map for prediction of flow patterns for various systems would need the help of Artificial Intelligence.

“…Bubbles and droplets and complex emulsions have a wide range of applications in the fields of drug delivery, tissue engineering, and oil extraction. Today, CFD simulation plays a prominent role in modeling [23][24][25][26][27][28][29][30][31][32][33][34][35]. Due to the importance of understanding the multi-phase process in different industries that use microstructures, the need for the correct prediction of flow regimes and reducing the risks of phase changes, modeling multi-phase flows, and understanding their performance in micro-devices is very important.…”

Section: Introduction To Microstructuresmentioning

confidence: 99%

A Review of the Methods of Modeling Multi-Phase Flows within Different Microchannels Shapes and Their Applications

et al. 2021

In industrial processes, the microtechnology concept refers to the operation of small devices that integrate the elements of operational and reaction units to save energy and space. The advancement of knowledge in the field of microfluidics has resulted in fabricating devices with different applications in micro and nanoscales. Micro- and nano-devices can provide energy-efficient systems due to their high thermal performance. Fluid flow in microchannels and microstructures has been widely considered by researchers in the last two decades. In this paper, a review study on fluid flow within microstructures is performed. The present study aims to present the results obtained in previous studies on this type of system. First, different types of flows in microchannels are examined. The present article will then review previous articles and present a general summary in each section. Then, the multi-phase flows inside the microchannels are discussed, and the flows inside the micropumps, microturbines, and micromixers are evaluated. According to the literature review, it is found that the use of microstructures enhances energy efficiency. The results of previous investigations revealed that the use of nanofluids as a working fluid in microstructures improves energy efficiency. Previous studies have demonstrated special attention to the design aspects of microchannels and micro-devices compared to other design strategies to improve their performance. Finally, general concluding remarks are presented, and the existing challenges in the use of these devices and suggestions for future investigations are presented.