A213 Development of liquid-gas two-phase flow solver towards simulation of oscillating heat pipe by large-scale parallel computers (original) (raw)

The Proceedings of the Thermal Engineering Conference

https://doi.org/10.1299/JSMETED.2014._A213-1_

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Heat Transfer Enhancement of a Low-Profile Block in a Channel Flow at Low Air-Velocity

Transactions of the Japan Society of Mechanical Engineers. B, 2005

investigation was preformed to enhance the heat transfer from a low-profile block placed in a channel flow at low duct Reynolds number of below 1000. The inflowing air to the heated block was accelerated due to the contraction effect by setting a barrier on the ceiling of the channel. The input electric-power to the cooling fan was kept constant, i.e., the flow rate decreases with increasing the pressure loss. The heat transfer from the heated block was dramatically increased in the conditions for which the flow reattachment on the top face of the block occurred as a result of the flow acceleration at the gap of the barrier. This method is particularly effective when the fan is operating at low loading conditions. If heated blocks are placed locally in a channel, the method using a barrier, which accelerates the flow directly around the blocks without increasing the flow rate, results in the less use of the fan power (pumping power) to achieve the heat transfer enhancement.

Simultaneous Measurement of Velocity and Heat Transfer in Unsteady Flow and Thermal Fields near the Wall Region

Nenji Taikai, 2016

In this study, the correspondence relationship between the instantaneous heat transfer and flow behaviours downstream of a backward facing step is presented. The temporal sequence of the instantaneous flow and temperature distributions were simultaneously measured by using stereoscopic PIV system (2D-3C) and a high-speed infrared thermography. Using this system, the unsteady flow and heat transfer behaviours were investigated at Reynolds number of 2.5 × 10 3 in the xy cross section. The flow in the heated wall direction corresponded to the enhancement of the heat transfer spatially near the wall.

Plasma Production and Ion Acceleration Process Study and Performance Prediction of Hall Thrusters Using Simple One-Dimensional Flowfield Calculation

JOURNAL OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES

Low-power Hall thruster flowfields were calculated using a simple one-dimensional model to understand plasma characteristics and ion acceleration processes and to predict thruster performance. The influences of magnetic field strength and acceleration channel length were mainly examined. The thruster model for calculation is the THT-IV low power thruster developed in Osaka University. Generally, ions were produced in an upstream region from the anode to some axial location of the acceleration channel, and then they were intensively accelerated in a region downstream just from the ionization region. With too short channel, ionization began downstream just from the anode, and then ion acceleration also occurred in the same region, resulting in poor ion flux and low thrust performance. In large channel length, the channel was long enough to produce a fully-ionized plasma, and efficient ion production and acceleration occurred. When the magnetic field strength increased in the channel, ionization occurred in a more upstream region, and ion acceleration began in the same region; that is, ionization and acceleration overlapped in the relatively long region. On the other hand, with a weak magnetic field ion production and acceleration, intensively and efficiently, occurred in their thin regions. Furthermore, we tried to include unclear anomalous electron diffusions by changing a Bohm diffusion coefficient at each high magnetic field strength in order to fit a calculated performance to the measured one. The calculated discharge current almost equaled the measured one, and the thrust characteristic also agreed well with the measured one.

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