Computation Of Total Exchange Areas Using Monte Carlo Method

Vol.8 No.3

Year: 2013

 
Issue: Feb-Apr

Title : Computation Of Total Exchange Areas Using Monte Carlo Method

Author Name : Saurav Khanna, UGRASEN YADAV, M.K.E. Prasad

Synopsis :

Monte Carlo method is widely used for the computation of total exchange areas in radiative heat transfer processes. This paper covers the development of a method based on classical probability distribution function and random numbers to evolve a computer algorithm for determination of total exchange areas in three dimensional furnace enclosures with emitting and absorbing surfaces.The method involves simulation of the pathways of a large number of beams carrying finite amount of energy from a specified surface zone inside an enclosure and tracing their routes until they get absorbed. Equations for beam tracings and intersection criteria have been developed for plane walls, rectangular paralleopiped and cylinders. Computed total exchange areas were found to be within 0.1% of theoretically calculated values of known shape factors for similar surface zones. The equations once verified can be applied to more complicated geometries by combining these basic shapes using zone method. Total exchange areas thus obtained can then be used in heat balance equations for multiple surface and gas zones to find the temperature and heat flux profile inside the furnace enclosure. These will be especially useful in modelling and simulation of reaction furnaces of unconventional shapes.

Drag reduction using mixed solutions of hydrotrope and surfactant in gravity driven flow systems

Vol.8 No.3

Year: 2013

 
Issue: Feb-Apr

Title : Drag reduction using mixed solutions of hydrotrope and surfactant in gravity driven flow systems

Author Name : Venkata Ramana, Subbarao chirravuri, Gopal singh, P.V

Synopsis :

Using drag reducing agents, experiments on efflux time are performed for ascertaining drag reduction during gravity draining of a liquid from a large cylindrical storage tank through an exit pipe. The drag reducing agents used are water soluble sodium salicycalate, a hydrotrope, Cetyl trimethylammonium bromide, a cationic surfactant (CTAB) and mixed solutions consisting of CTAB and sodium salicylate(SS). The experiments are performed using different weight ratios of sodium salcylate and CTAB. Optimum concentrations for all the three cases have been established. The diameter of storage tank diameter of the exit pipe and lengths of exit pipe are kept constant while performing experiments. The experiments are also performed for different volumes of liquid in the tank. It has been observed that the optimum concentration (minimum efflux time) for all the cases is independent of volume of liquid in the tank. The drag reduction ( i.e reduction in efflux time) with mixed solutions of sodium salicycalate and CTAB at 100 ppm is observed to be comparable with that of CTAB alone at 1000 ppm.

Numerical Simulation Of Turbulent Flow And Local Heat Transfer Coefficient Over A Horizontal Step

Vol.8 No.3

Year: 2013

Issue: Feb-Apr

Title : Numerical Simulation Of Turbulent Flow And Local Heat Transfer Coefficient Over A Horizontal Step

Author Name : Yasser Rihan

Synopsis :

This paper deals with a numerical analysis to investigate the heat transfer and the fluid flow behavior in a rectangular channel with a horizontal step on one principal wall. A mathematical model is proposed to simulate the heat transfer process inside the heat exchangers. The model is based on the conservation equations of continuity, momentum and energy. The two equations of turbulence model ‘k-ε’ are also applied. The implicit scheme of finite volume method is used for solving the coupled differential equations with iterative procedure. Thereby, the degree of flow separation is varied by changing the step height. The step height ratio (b/H) ranging from 0.25 to 0.75. The Reynolds number ranges from 10,000 to 80,000. The results show that the local heat-transfer coefficients in the separated reattached and redeveloped regions are several times as large as those for a fully developed flow. In general, the increase of the heat transfer coefficient owing to flow separation is accentuated as the Reynolds number increases. The comparison between the presented model and previously published experimental data shows a good agreement.

Estimation of vertical coherence of ship Generated noise in the Bay of Bengal region

Vol.8 No.3

Year: 2013

 
Issue: Feb-Apr

Title : Estimation of vertical coherence of ship Generated noise in the Bay of Bengal region 

Author Name : SIVAKUMAR GANGADHARAM, V.Rajanikanth

Synopsis : 

The Bay of Bengal sea area near by Chennai carries considerable amount of shipping. This mostly originates from traffic to and from the other major ports of India. Shipping noise is the most influence of ambient noise in shallow water areas close to shipping narrow ways . Shipping noise is most evident in the 50-300 Hz frequency range. Shallow water region acts as a high pass filter, with the cut-off frequency increasing as the water get shallower. There is an multiple bottom reflection encountered in shallow water region .So the spatial structure of the ambient noise field strongly depends on the geo acoustic properties of the seabed. The vertical directionality and coherence are stable feature of the ambient noise, which are determined by the seabed. These properties are not varied due to the surface source distribution. The ambient noise field in shallow water region is highly complex due to the waveguide nature of the shallow water environment. The automatic ambient noise measurement system deployed in shallow water region of the Bay of Bengal was used to determine the vertical coherence of ship generated noise. In this paper the vertical coherence for different sea state, level of spectrum and effect of ship noise forcing on coherence pattern are presented.

Modeling Of Laser Lithotripsy Technique Author Name : Munqith S. Dawood, Wedyan H. Rejah

Vol.8 No.3

Year: 2013

 
Issue: Feb-Apr

Title : Modeling Of Laser Lithotripsy Technique Author Name : Munqith S. Dawood, Wedyan H. Rejah

Synopsis :

Different lasers are used in intra corporeal lithotripsy. They differ in their wavelengths, pulse durations, and pulse energies. One of the most recently used laser in surgery is the Ho:YAG laser. It is introduced for both of the soft tissue ablation and lithotripsy applications. The use of this laser in lithotripsy is increasingly widespread, because it can fragment all stone types and produce tiny fragments, which can easily pass through the urinary tract. The mathematical models of this laser interaction with two urinary stones are considered and studied in this paper. They are based on the thermal effect calculations of Ho:YAG laser on these stones. The crater volumes and crater depths in both of the calcium oxalate monohydrate (COM) hard stone and uric acid (UA) fragile stone were calculated as a function of the exposure radiant laser energy, number of pulses and pulse durations of thisHo:YAGlaser. The achieved theoretical results are close to other published practical results. It was found that the absorption of laser energy by the urinary stones is the most effective parameter, which makes the theoretical results comparable to the practical results.