Purpose-The purpose of this paper is to investigate flow behavior of electrorheological (ER) fluid in a closed piston-cylinder system. Design/methodology/approach -A basic study of flow characteristics of ER fluid in a damper model is conducted experimentally and numerically. The electric field is applied between inner wall of the cylinder and outer wall of the piston, and the pressure difference between upper and lower chamber of the cylinder is measured. A numerical prediction of ER fluid flow in the damper model system is performed in order to study the ER fluid flow characteristics. Visualization experiment isalso made and used to qualitatively verify the numerical formulation. Findings -The agreement between the numerical predictions and experimental results is encouraging, and the ER fluid flow patterns under different piston aspect ratios, movement speeds and applied electric field strengths are presented. The results show that the piston aspect ratio has much smaller influence on the ER flow pattern than other influencing factors. Increasing piston movement speed or reducing the electric field applied is helpful to reduce the pressure response time period, which is an important indicator showing sensitiveness of the damper. It is also seen that the pressure difference between the upper and lower chamber of the cylinder increases with the electric field strength and the piston movement speed. Originality/value -First time the detailed investigation into the hydrodynamics behavior in such working models of neering applications for ER fluid.

In this report, a new CO2 refrigeration system is introduced, which can achieve a refrigeration capability below the CO2 triple point of -56.6 C. The proposed CO2 refrigeration system consists of two thermodynamic cycles arranged in cascade, where one is a CO2 trans-critical cycle and another is a trans-triple-point cycle. An experimental set-up is constructed and tested in order to obtain a basic knowledge about this CO2 system. Based on the measured data, it is concluded that the built CO2 refrigeration system can operate continuously and stably, although dry ice particles exist in the closed CO2 loops. An average COP (a ratio of cooling energy to the compressor power consumption) is measured at 2.45 in the present experiment range for the low-pressure system of the experimental set-up. In addition, the influence of the condensation temperature on the refrigeration cycle is investigated and more studies are needed for the future optimization work.

Transport phenomena in three-dimensional branching channel are important because of their relevance in polymer processing. In this article, an experimental study on viscoelastic flow in a three-dimensional cylindrical branching channel is carried out to investigate variations of flow pattern. Flow visualization in representative symmetric planes is made both for the viscoelastic fluid and Newtonian flow. From the results of the present investigation, the flow field in the threedimensional cylindrical branching channel is clarified within the range of laminar flow. It is confirmed that corner vortex, shedding vortex, and secondary vortex flow are all obviously changed with the fluid concentration and the Reynolds number, which are much more three-dimensional and complex than the Newtonian fluid, and the flow pattern of the viscoelastic fliud flow largely depends on the Reynolds number and fluid concentration. Even for the viscoelastic flow at the low Reynolds number, shedding vortex and secondary vortex and complex three-dimensional flow occur in the cylinder. The flow field is not symmetric space for the viscoelastic flow and however is fairly symmetric for the Newtonian fluid. The above reasons explain why the flow deflection happens even at the low Reynolds number flow. POLYM. ENG. SCI. , 50:32–42, 2010. a2009 Society of Plastics Engineers

Experiment and numerical study were conducted to investigate the heat transfer characteristics of a thermo-sensitive magnetic fluid (TSMF) filled in a cubic container with a heat generating square cylinder stick inside and under a uniform magnetic field. The experimental results show that, regardless of the heat generating object sizes, the heat transfer characteristic of the TSMF is enhanced when the magnetic field is applied to the TSMF. However, the heat transfer of the TSMF becomes poor as the size of the inside heat generating object increases because the space where the fluids go through becomes narrower and the flow is obstructed when the heat generating object size becomes bigger. Numerical simulation based on the Lattice Boltzmann method confirmed the experimental findings, and disclosed more flow details of the natural convection of the TSMF inside cavity.

In this article, natural convections of a magnetic fluid in a cubic cavity under a uniform magnetic field are investigated experimentally and numerically. Results obtained from experiments and numerical simulations reveal that the magnetic field and magnetization are influenced by temperature. There exist relative larger magnetization and magnetic forces in the regions near the upper wall and center inside the cavity than in the region near the bottom and side walls. A weak flow roll occurs inside cavity under the magnetic force, and it brings the low temperature fluid downward in the center region, and streams the high temperature fluid upward along the regions near the sidewalls. With the magnetic field imposed, the heat transfer inside the cavity is enhanced significantly compared to that without the magnetic field, and increasing the strength of the magnetic field the heat transfer is increased further.