The aim of the present numerical study to analyze the conjugate natural convection heat transfer in a rotating enclosure with finite wall thickness. The enclosure executes a steady counterclockwise an-gular velocity about its longitudinal axis. The staggered grid arrangement together with the Marker and Cell (MAC) method was employed to solve the governing equations…

Natural convection heat transfer in a two dimensional unsteady rotating differentially heated enclosure is studied numerically in this paper. The enclosure is filled with air and executes a steady counterclockwise rotation about the centre of the enclosure. A finite volume code on a staggered grid arrangement with TDMA algorithm is developed and employed to solve the governing equations subject to Boussinesq approximation.The numerical investigation is carried out for fixed Prandtl number equal to 0.71, Rayleigh number equal to1.1  ´ 105 while Taylors number vary from 5.2 ´ 104 to 3.3 ´ 105 and Rotational Rayleigh number from 4.9 ´ 102 to 3.1 ´ 103.Results reveal that there are considerable change in heat transfer rates beyond 15 rpm. The effect of rotation on the Nusselt number for a given Rayleigh number is shown in the present work which is not normally indicated and discussed in the available literature.

A Numerical study is carried out to investigate the effect of Rayleigh number with rotation on the flow and heat transfer characteristics in a differentially heated enclosure rotating about the horizontal axis. A Fortran Code developed based on FVM is used to discretize governing equations. Upwind difference scheme for convective terms and fully implicit scheme for transient terms are used. The SIMPLE algorithm is employed to couple pressure and velocities on staggered grid arrangement. The results were obtained for a Taylor number(10􀬷 ≤ 􀜶 􀜽 ≤ 10􀬹 ), rotation (10 􀝎 􀝌 􀝉 ≤ Ω ≤ 25 􀝎 􀝌 􀝉 ), and Rotational Rayleigh number (10􀬵 ≤ 􀜴 􀜽 􀯪 ≤ 10􀬷 ) for two different Rayleigh number (1. 3 × 10􀬸 & 1. 1 × 10􀬹 ) with fixed Prandtl number (􀜲 􀝎 = 0. 71). The results showed that the Coriolis force first tends to decrease heat transfer to a minimum and then starts to increase it with increase Rayleigh number and rotation. Minimum depends on Rayleigh number and corresponds to the balanced effects of interacting forces at the point of transition. At rotations, below minimum in average heat transfer, the circulations are counter clockwise. The direction of coriolis force is from core region, so both flow and heat transfer is reduced. When coriolis force is much larger than thermal buoyancy, motion is clockwise, and transition is prevented. coriolis force now tends to promote flow circulation and therefore increases the heat transfer. The frequency content of flow pattern reveals the structural changes in the flow and temperature fields with increasing Rayleigh number and rotation. The existence of different flow regimes dominated by these body forces complicates the time average heat transfer characteristics with a different behaviour in each of the regimes.

In the present study, mixed convective heat transfer inside a square enclosure in the presence of a rotating cylinder with various numbers of grooves is presented. Effects of counterclockwise and clockwise rotations with non-dimensional rotating speeds (RS) in the range from -1000 to 1000 are studied for different radius ratios (R) of 0.1, 0.2, and 0.3. Computations are carried out for Rayleigh numbers 103, 104, and 105 using the finite volume approach. The obtained results are validated against the available data for an empty enclosure (in the absence of a cylinder) as the reference case and also for an enclosure with a rotating smooth cylinder. It is demonstrated that for a specific value of the Rayleigh number, increasing the radius ratio enhances the thermal performance inside the enclosure regardless of the groove number and rotating speed. Increasing the Rayleigh number attenuates the roles of rotating speed and radius ratio, gradually. It is concluded that among all cases, the case with counterclockwise rotating smooth cylinder and among the grooved cases, Case 5 with three grooves provide the maximum heat transfer enhancements.

Aims The use of intrauterine devices (IUDs) has been one of the most effective, the safest and cost-effective methods for preventing pregnancy, for a long time. However, some complications have been reported for IUDs. The complications may be reduced by using a specific technique for placement of IUD. The objective of this study was to introduce the rotating withdrawal technique for the first time, which was investigated to reduce the complications of IUD insertion. Materials & Methods This historical cohort study was conducted on 1199 females who referred to Sarem Medical Center for IUD insertion from 1984 to 1995. After primary examinations, IUD was inserted by rotating withdrawal technique. The subjects were followed up for 2 years. Findings Displacement was observed just in 20 cases (1. 67%). All of them were seen in the first month after placement. For these cases, IUD insertion was done again. After the second replacement, displacement was observed in 4 cases (0. 035%) after one month. Therefore, it was recommended to them to use another preventive method. There was no pregnancy or displacement in the other cases during 2 years. Conclusion The rotating withdrawal technique can minimize the pregnancy rate when IUD is used. In addition to the type and quality of IUD, insertion method of IUD can increase its effectiveness.

In this research, a rotating solar still that uses external bottom reflectors was experimentally investigated. The solar still and reflectors have the capability to shift their angle with respect to the south and the reflectors have the capability to shift their angle with respect to the horizon. The experiment has been performed in both fixed and rotating states. For the fixed state the solar still was placed toward south and the reflectors were set in such a way to reflect sun rays on the bottom surface of the basin at solar noon. For rotating state, the solar still and reflectors were set manually every half an hour in such a way to reflect sun rays on the bottom surface of the basin and the system was directed toward the sun all the time. The experiments were performed from November to December for 27 days. Sunny days results indicated that on average, distilled water gained using rotating mode was about 64% more than the fixed mode. Both the rotating and fixed mode yield for two cloudy days with respect to the average yield of sunny days decreased by 47 and 53%, respectively.

There are two main methods in fire modeling: zone models and field models. The conservation of mass and energy in enclosure is the theoretical base of zone models. The models deal with heat release rate, fire plume, mass flow, smoke movement and gas temperature in fires. Theoretical principles of compartment fire zone modeling are presented and the behavior of fire in enclosures is discussed. The conservation laws are presented in control volume form and applied to the behavior of fire in enclosures. The governing equations are derived and presented. Some zone models and their field of application in fire modeling are also given.