The sweeping jet (SJ) film cooling hole has shown promising cooling performance compared to the standard shaped hole in low-speed conditions. The present work demonstrates the first attempt of SJ film cooling at an engine relevant Mach number. An experimental investigation was conducted to study the SJ film cooling on a nozzle guide vane suction surface. A well-established additive manufacturing technique commonly known as stereolithography (SLA) was utilized to design a transonic, engine representative vane geometry in which a row of SJ holes was used on the vane suction surface. Experiments were performed in a linear transonic cascade at an exit Mach number of 0.8 and blowing ratios of BR = 0.25–2.23. The measurement of heat transfer was conducted with the transient IR method, and the convective heat transfer coefficient (HTC) and adiabatic film cooling effectiveness were estimated using a dual linear regression technique (DLRT). Aerodynamic loss measurements were also performed with a total pressure Kiel probe at 0.25Cax downstream of the exit plane of the vane cascade. Experiments were also conducted for a baseline-shaped hole (777-hole) for a direct comparison. Results showed that the SJ hole has a wider coolant spreading in the lateral direction near the hole exit due to its sweeping motion that improves the overall cooling performance particularly at high blowing ratios (BR > 1). Aerodynamic loss measurement suggested that the SJ hole has a comparable total pressure loss to the 777-shaped hole.
Drying of moist porous media, such as paper and pulp, is an extremely energy-consuming process. Traditional drying techniques are primarily associated with convection, conduction, and thermal radiation. It is desirable to develop innovations in non-thermal and high-efficiency drying techniques. In the previous study, a novel drying technology, making use of the Dielectrophoresis (DEP) mechanism, has been experimentally proved to be an energy-efficient method to enhance the drying rate of moist porous media. DEP is a translational motion of neutral matter caused by the polarization effects in a diverging electric field. During the drying process, in the presence of the DEP force, the vapor phase is extracted away from the porous medium, which results in an increase of the evaporation rate and a decrease of the sample surface temperature. This paper extends previous experimental studies by including analysis of the heat-transfer characteristics. Specifically, the heat flux rate underneath the moist paper is monitored during the drying process. The sample surface temperature is monitored through an Infrared (IR) camera. Moreover, the convection heat transfer coefficients are estimated, and the sample’s initial moisture content is studied as a function of drying time. The experimental results show an up to 132% increase of the heat flux rate and a 242% increase of the convection coefficient due to the application of an electric field, as compared to conventional drying process. The experimental results also illustrate that the DEP effects diminish at low moisture levels. The detailed heat transfer analysis provides a foundation for the enhancement of moist porous media using the DEP mechanism for drying fragile products.
The paper drying process is very energy inefficient. More than two-thirds of the total energy used in a paper machine is for drying paper. Novel drying technologies, such as ultrasound (US) drying, can be assessed numerically for developing next-generation drying technologies for the paper industry. This work numerically illustrates the impact on drying process energy efficiency of US transducers installed on a two-tiered dryer section of a paper machine. Piezoelectric transducers generate ultrasound waves, and liquid water mist can be ejected from the porous media. The drying rate of handsheet paper in the presence of direct-contact US is measured experimentally, and the resultant correlation is included in the theoretical model. The drying section of a paper machine is simulated by a theoretical drying model. In the model, three scenarios are considered. In the first scenario, the US modules are positioned in the dryer pockets, while in the second scenario, they are placed upstream of the drying section right after the press section. The third case is the combination of the first and second scenarios. The average moisture content and temperature during drying, enhancement of total mass flux leaving the paper by the US mechanism, total energy consumption, and thermal effect of heated US transducers are analyzed for all cases. Results show that the application of the US can decrease the total number of dryer drums for drying paper. This numerical study is based on the US correlation obtained with the US transducer in direct contact with the paper sample. Thus, future work should include US correlation based on a non-contact US transducer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.