A new mixed Eulerian-Lagrangian computational model for simulating and visualizing the internal processes and the variations of dynamic parameters of a two-stage pulse tube cooler (PTC) operating at 4 K-temperature re...A new mixed Eulerian-Lagrangian computational model for simulating and visualizing the internal processes and the variations of dynamic parameters of a two-stage pulse tube cooler (PTC) operating at 4 K-temperature region has been developed. We use the Lagrangian method, a set of moving grids, to follow the exact tracks of gas particles as they move with pressure oscillation in the pulse tube to avoid any numerical false diffusion. The Eulerian approach, a set of fixed computational grids, is used to simulate the variations of dynamic parameters in the regenerator. A variety of physical factors, such as real thermal properties of helium, multi-layered magnetic regenerative materials, pressure drop and heat transfer in the regenerator, and heat exchangers, are taken into account in this model. The present modeling is very effective for visualizing the internal physical processes in 4 K-pulse tube coolers.展开更多
The homogeneous nucleation with subsequent spontaneous condensation of water, pentanol, and ethanol xupors in a carrier gas are investigated experimentally and theoretically in the expansion part of a shock tube. The ...The homogeneous nucleation with subsequent spontaneous condensation of water, pentanol, and ethanol xupors in a carrier gas are investigated experimentally and theoretically in the expansion part of a shock tube. The precise pressure and Mcw measurements give additional information about the wetness, so that the nucleation and condensation rates which are closely coupled for stronger expansion rates are determined more accurately. Predictions of the principle of the minimum of entropy production are compared with experiments performed for water, ethanol and pentanol at different pressures.展开更多
文摘A new mixed Eulerian-Lagrangian computational model for simulating and visualizing the internal processes and the variations of dynamic parameters of a two-stage pulse tube cooler (PTC) operating at 4 K-temperature region has been developed. We use the Lagrangian method, a set of moving grids, to follow the exact tracks of gas particles as they move with pressure oscillation in the pulse tube to avoid any numerical false diffusion. The Eulerian approach, a set of fixed computational grids, is used to simulate the variations of dynamic parameters in the regenerator. A variety of physical factors, such as real thermal properties of helium, multi-layered magnetic regenerative materials, pressure drop and heat transfer in the regenerator, and heat exchangers, are taken into account in this model. The present modeling is very effective for visualizing the internal physical processes in 4 K-pulse tube coolers.
文摘The homogeneous nucleation with subsequent spontaneous condensation of water, pentanol, and ethanol xupors in a carrier gas are investigated experimentally and theoretically in the expansion part of a shock tube. The precise pressure and Mcw measurements give additional information about the wetness, so that the nucleation and condensation rates which are closely coupled for stronger expansion rates are determined more accurately. Predictions of the principle of the minimum of entropy production are compared with experiments performed for water, ethanol and pentanol at different pressures.
