International Journal of Engineering
Volume:18 Issue: 1, Feb 2005

In this paper the heat transfer characteristics of a two-phase closed thermosyphon over a wide range of heat transfer rates, system pressure, aspect ratios and filling ratios were studied. The experiments focused on the boiling and condensation heat transfer characteristics of a thermosyphon with a copper tube having 25 and 32 mm inside and outside diameters. Distilled water was used as the working fluid. The experimental boiling and condensation heat transfer coefficients inside the thermosyphon were compared with the existing correlations. A good agreement between the experimental results of condensation heat transfer of the thermosyphon and Nusselt’s correlation was obtained. In addition, the optimal working fluid filling and the overall heat transfer coefficient were evaluated for practical operation. Finally, according to poor agreement between the experimental results of boiling heat transfer coefficient and existing correlations, the working conditions were analyzed and a new practical formula (correlation) was presented. The new correlation can be used to predict boiling heat transfer coefficient generally.

In the present paper, the problem of externally excited exponential transmission line hasbeen solved analytically in frequency domain using a simple approach. Then steplines approximationas a first order approximation for the problem of externally excited nonuniform transmission lines ingeneral and exponentially tapered transmission line (ETL) as a special case has been presented.Finally the two approaches are compared and some useful results are obtained to show when the twomethods are equivalent.

This study deals with a state dependent machining system having provision of mixed spares. The service facility of the system consists of permanent as well as removable additional repairmen. When all the spares are utilized, the system works in short mode. The steady state solution of the queue size distribution is derived using product type solution. Expressions for some performance measures are established. Some earlier models are deduced as special cases of the model for specific values of the parameters.

The unstable flow with rotating-stall-like (RS) effects in a rotor-cascade of an axialcompressor was numerically investigated. The RS was captured with the reduction in mass flow rateand increasing of exit static pressure with respect to design operating condition of the single rotor.The oscillatory velocity traces during the stall propagation showed that the RS vortices repeatperiodically, and the mass flow rate was highly affected by the blockage areas made by stall vortices.The results also showed that large scale vortices highly affects on the generation and growth of thenew vortices. An unsteady two-dimensional finite-volume solver was employed for the numericalstudy which was developed based on Van Leer’s flux splitting algorithm in conjunction with TVDlimiters and the flow rate with the experimental results validates the numerical study.κ-ε turbulence model was also employed. The good agreement of the computed mass

Oxygen is an essential part of the living organism. It is transported from blood to the body tissue by the systematic circulation and large part of it is stored in the blood flowing in capillaries. In this work we discuss a mathematical model for oxygen transport in tissues. The governing equations are established assuming that the blood is flowing along a co-axial cylindrical capillary inside the tissue and has a constant partial pressure of oxygen. We solve the governing partial differential equations using finite element techniques. The main object of the present work is to investigate the effects of various assumptions such as neglecting axial diffusion and neglecting the effect of facilitated myoglobin diffusion.