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The packing is the core heat transfer unit in the cooling tower. To improve the heat and mass transfer performance of the counterflow wet cooling tower, a new double S-wave structure packing is proposed in this paper, and its performance in heat-mass exchange is investigated using a combination of numerical simulation and experiment. The flow heat transfer performance of the double S-wave packing with different sheet spacing, tilt angle and inlet area is studied by numerical simulation, and the law of different structural parameters affecting the packing is derived to determine its optimal structure. The thermal and resistance performance of double S-wave packing and conventional double-folded packing under different working conditions were studied in comparison with each other by building an experimental bench. The results show that the cooling efficiency of double S-wave packing is 13.74% higher and the pressure drop is 3.58% lower than that of double-folded packing. The research results can provide important guidance and reference for engineering practice. [ABSTRACT FROM AUTHOR]

The cylindrical slide valve is an essential component of the hydraulic system, which regulates and controls the oil. When hydraulic oil flows through the slide valve port, cavitation often occurs due to a sharp pressure drop, affecting the hydraulic system's stability. Therefore, the study of cavitation phenomena in valves is an important topic. This paper conducts a transient numerical simulation of the three-dimensional multi-physics field in the valve under different inlet pressure and oil temperature conditions and studies the effects of different inlet pressures and oil temperatures on the oil's temperature rise and cavitation phenomenon at the valve port. The results show that under high-pressure differences, the temperature of hydraulic oil rises significantly. In addition, the increase in oil temperature will significantly affect the cavitation intensity in the valve. When the oil temperature is 330 K, the severity of cavitation in the valve under a pressure of 5 MPa is roughly the same as when the oil temperature is 300 K, and the inlet pressure is 15 MPa. Under different inlet pressure and oil temperature conditions, the pressure pulsation in the slide valve is also very different. Under certain working conditions, the peak power spectrum density of the pressure pulsation is close to the hydraulic natural frequency, which may cause the slide valve to self-excited oscillation. Therefore, it is recommended that under actual working conditions, the oil temperature should be lowered in time to reduce the adverse effects of valve port cavitation. • A mathematical model of cavitation coupled with temperature fields was developed. • The high-pressure drop at the valve port causes the hydraulic oil temperature to rise significantly. • As The oil temperature increases, the cavitation phenomenon in the valve increases significantly. • Under certain working conditions, the pressure pulsation frequency caused by cavitation is close to the hydraulic natural frequency. [ABSTRACT FROM AUTHOR]

• A macroscale model is developed to study electrostatic particle filtration. • Multi-layering is proposed as a means of protecting the bipolarly charged fibers. • Unipolar and bipolar charging are considered to lower the pressure drop. • Placing the unipolar layer upstream of the bipolar layer extends filter's life. The deposition of neutral and charged particles inside an electrostatically charged filter can affect its performance by decreasing its ability to capture additional particles and by increasing its pressure drop. The particle-loaded behavior of a composite filter comprised of three fibrous layers is studied in this paper using a macroscale simulation approach. Each of these fibrous layers were assumed to have fibers with the same amount of charge but different charge polarities of only unipolar positive, only unipolar negative, or only bipolar. The charged layers were stacked on top of one another in three different configurations with respect to the flow direction and their filtration efficiency and pressure drop were compared during particle loading with neutralized particles (having the Boltzmann equilibrium charge distribution), singly-charged particles, and neutral particles. Our simulations revealed that placing the bipolarly-charged layer downstream of the unipolarly charged layers helps to lower the negative impact of particle deposition on pressure drop and filtration efficiency of the resulting composite filter. This study introduces a design tool which can be used to optimize the configuration of a composite filter for enhanced particle capture efficiency and reduced pressure drop increase. [ABSTRACT FROM AUTHOR]