Zhi-Fu Zhou

Fully developed flow of a drilling fluid between two rotating cylinders

In this paper, we study the fully developed Couette flow of a drilling fluid, and explore the effects of concentration and shear-rate-dependent viscosity. The one-dimensional form of the governing equations, as well as the boundary conditions are made dimensionless and a parametric study is performed by varying the dimensionless numbers.

Rapid fabrication of metal-coated composite stereolithography parts

Abstract In this paper, the rapid fabrication method based on stereolithography (SL) and electrochemical deposition is described in detail and mechanical test results of composite nickel-coated SL parts are presented. Coatings of electrodeposited nickel on SL prototypes result in increases in Youngs modulus, UTS, flexural modulus, and strength. Electrodeposited nickel coating has dramatically improved the overall strength and stiffness of SL parts. The adhesive strength of the roughened SL resin-nickel interface is higher than the original. In particular, the influence of the surface roughness on adhesive strength between SL and metal is investigated. Moreover, this paper has presented an application of a structural electrodeposited nickel coating over SL parts to make a functional airfoil model with a complex internal structure and sufficient mechanical strength and stiffness.

Theoretical Evaporation Model of a Single Droplet in Laser Treatment of PWS in Conjunction With Cryogen Spray Cooling

Cryogen spray is an effective cooling technique used for laser treatment of Port Wine Stain. The cooling process involves complex droplet evaporation and strong convective heat and mass transfer, therefore a deep understanding of spray characteristics is essential in order to optimize the nozzle design and improve the cooling efficiency of the spray. This paper improves a theoretical model to describe the equilibrium evaporation process of a single cryogen droplet in cryogen spray. The results of comparative analysis of gas phase models for single droplet heating and evaporation are presented. Six different semi-theoretical models based on various assumptions are compared and their effects on a single droplet heating and evaporation characteristics in the process of cryogen R-134a spray cooling are compared. It is pointed out that the gas phase model, in which the effect of superheat is taken into account, predicts the evaporation process closest to the experimental data. Finally, a parametric study of the influences of initial diameter and velocity on the droplet evaporation is then carried out. The results can be used to guide the Cryogen Spray Cooling of laser therapy.Copyright