Vertical Parallel Plates Research Articles

Natural convective heat transfer between vertical parallel plates with symmetric and asymmetric heating.

To analyze the heat transfer phenomenon in electronic circuit plates, natural convective heat transfer between two vertical parallel plates, with symmetric or asymmetric uniformly heated wall, was investigated experimentally in the range of high Grashof number (Gr=103-107).The local heat transfer coefficient was strongly affected by the axial distance of the plate in the case where distance and temperature difference between plates were small. Average Nusselt number was affected by Grashof number, distance and temperature difference between the plates. An empirical equation for average Nusselt number in the two vertical parallel plates was obtained.

Natural convection heat transfer in vertical parallel plates with a closed lower end. (1st report Numerical analysis)

On natural convection heat transfer of two vertical parallel plates with a closed lower end, a numerical analysis was performed for Grashof numbers ranging from 104 to 107, the ratio of hot and cold wall temperatures ranging from 0.1 to 1 and a Prandtl number of 0.71, under the condition of constant wall temperature. The local Nusselt number is slightly larger than that of the experimental results by Siegel in the range of 106 < Gr < 107. For small values of the wall temperature ratio, negative heat transfer coefficients of the cold wall are observed. The average Nusselt number can be expressed as a function of the distance of parallel plates and the Grashof number based on it ; Nus =C(GrsS2)n where C and n are functions of the wall temperature ratio. Circulating flows are found in the vicinity of the end of the parallel plates.

Turbulent free convection heat transfer to air from vertical parallel plates.

Turbulent free convection heat transfer to air from vertical parallel plates (height of 5000 mm and spacings B of 50, 100 and 200 mm) were studied experimentally. Turbulence quantities (intensities and correlations of fluctuating temperature and velocities, and turbulent shear stress) in the induced flow between the parallel plates were measured using LDV and fine thermocouples at height X (=820, 1690, 2630 and 3840 mm). The measured streamwise variations of the turbulence quantities, which were affected by the inlet disturbances in the upstream flow region, demonstrated that there were three types of flow regions corresponding to the laminar, transition and turbulent regions of the free convection boundary layer on a single vertical plate. The characteristics of the turbulence quantity profiles in each flow region were consistent with those of the local Nusselt number distributions on heated plates, calculated from the vertical distributions of temperature on it.

Natural convection heat transfer in vertical parallel plates with a closed lower end. (2nd report Experiment)

Natural convection heat transfer in vertical parallel plates with a closed lower end. (2nd report Experiment)

Transition to Meandering Rivulet Flow in Vertical Parallel-Plate Channels

Transition to Meandering Rivulet Flow in Vertical Parallel-Plate Channels

Characterization of Plasma-Enhanced Chemical Vapour Deposition of Silicon-Oxynitride

AbstractThe plasma-enhanced chemical vapour deposition (PECVD) of siliconoxynitride from silane, ammonia and nitrous oxide was studied using an ASM vertical parallel plate reactor.Films varying from PECVD oxide (refractive index no1.50) to PECVD nitride (n=2.00) were analyzed using ellipsometry, UV-visible reflection spectroscopy, Fourier-transform infrared transmission spectroscopy (FTIR), nuclear reaction analysis (NRA), Rutherford backscattering (RBS) and electron spectoscopy for chemical analysis (ESCA).Stress measurements were performed using a Fizeau interferometer.

Convective Immersion Cooling of Parallel Vertical Plates

Complete immersion of electronic assemblies, in fluids of appropriately high dielectric strength and low dielectric constant, offers a most promising alternative to conventional thermal control measures. The present study is aimed at providing an analytical basis for the design and optimization of convective immersion cooling systems by focusing on the analytical development and experimental verification of composite relations for the natural convection heat transfer coefficients prevailing along the Surfaces of immersed, uniformly heated plates in both symmetric and asymmetric configurations.

Natural convection flow of a non-Newtonian fluid between two vertical flat plates

The natural convection of a homogeneous incompressible fluid of grade three is investigated between two infinite parallel vertical plates. The effect of the non-Newtonian nature of fluid on the skin friction and heat transfer are studied.

Heat and mass transfer with a mist formation in free convective field between vertical parallel plates. 2nd report Experimental study.

前報で理論的に明らかにされた自然対流熱・物質伝達へのミスト発生の影響について、実験的に検討した。水蒸気-空気系での等温垂直冷却平行平板間自然対流場での凝縮実験を行い、ミスト発生の様相の観察、吸引サンプリング法によるミスト質量流量の測定、温度分布および熱・物質伝達率の測定結果と解析結果との比較により、解析の妥当性が明かにされるとともに、滴の成長・輸送の過程が熱・物質伝達との関連づけ明かにされた。

The Stability of Natural Convection in a Vertical Layer of Dielectric Fluid in the Presence of a Horizontal ac Electric Field

Linear stability theory is applied to examine the effect of a horizontal ac electric field on the stability of natural convection which occurs in a dielectric fluid between two parallel vertical plates maintained at different temperatures. The power series method is used to obtain the eigenvalue equation which is then solved numerically. It is shown that when the electrical Rayleigh number L (defined in the text) is less than about 2130 the electric field has no effect on the stability of natural convection, and that when L exceeds this value the electric field and the natural convection flow are coupled strongly and they exhibit a complicated but interesting effect on the stability of the system. A rough criterion is given for applicability of the power series method to the present problem.

Convection naturelle mixte et forcee dans un thermosiphon vertical chauffe a flux constant

Developing laminar mixed convection between two vertical parallel plates with uniform but asymmetric heating is investigated numerically using a finite difference method, in the three following cases: aiding flow, opposing flow with fluid flowing either upwards or downwards. The flow rate and the wall temperatures calculated in these three cases allows the physical behaviour of the flow to be discussed.

Elliptical multielectron dimples on liquid and solid helium surfaces

The structure of multielectron dimples on helium substrates is investigated for conditions deviating from axial symmetry. Main sources for an ellipticity of dimples are an anisotropy of the surface tension, as for the liquid-solid He interface, or anisotropic boundary conditions, as for liquid He between vertical parallel plates.

The Effect of Nonlinear Density Stratification on the Stability of a Vertical Water Layer in the Conduction Regime

The thermal stability of a layer of water between two vertical parallel plates maintained at different temperatures, T1 and T2, is investigated for the conduction regime. Three cases are considered include where: (a) the maximum density layer is within the water region; (b) is at the boundary; and (c) is outside the water region. Cubic polynomials are used to represent the density-temperature relation in the temperature range 0–55°C. The numerical results show that the critical states of stability do not depend on Prandtl number but instead depends on the combinations of T1 and T2. Of the three cases considered, the first case is the most unstable. In all three cases, the instabilities set in as a traveling wave, moving against gravity, for most T1 and T2 combinations. Stationary waves were also found for case (c).

Attraction and repulsion of floating particles

The horizontal force that has to be applied to floating cylinders to equilibrate the capillary force is calculated for a general geometry with cylindrical symmetry and for any wetting characteristics of the cylinders. The force on a cylinder can be related to a single parameter of each of the two menisci that contact the cylinder. It is found that the force between parallel vertical plates or parallelipipeds can be repulsive if one of the contact angles is acute and the other obtuse. The force on cylinders between fixed walls is also calculated and the results suggest that it may be possible to separate floating particles with different wetting properties by placing them between two walls with different contact angles.

Experiments on Free Convection Between Vertical Plates With Symmetric Heating

Laboratory experiments on natural convection of air between vertical parallel plates with uniform and symmetric heat fluxes are reported. Data collection was through direct temperature measurement using thermocouples and through analysis of interferograms of the flow. Data were collected over a range of heat fluxes and geometric parameters where the flow was in the developing temperature field regime. A correlation is developed that allows for the calculation of the maximum temperature variation of the plates for a given input heat flux and plate geometry. The equation is expected to be accurate to ±5 percent.

Flow instability and transport phenomena in combined free and forced convection between vertical parallel plates.

Flow instability and transport phenomena in combined free and forced convection between vertical parallel plates.

Convection naturelle laminaire dans un canal vertical chauffe a flux constant

Developing laminar free convection between vertical parallel plates with uniform but asymmetric heating is investigated numerically. The governing equations are solved by a finite difference method taking into consideration the moving pressure drop due to the fluid velocity at the channel entrance plane, which was neglected in the previous numerical studies. The results are shown to be in good agreement with similar solutions for the vertical flat plate at large Grashof numbers and thus the range of validity for the results obtained previously is defined. Flow rates, velocity and temperature profiles are obtained for different ratios of the two wall heat fluxes. Wall temperatures and heat transfer parameters are calculated.

Buoyancy effects on turbulent transport in combined free and forced convection between vertical parallel plates

Turbulent mixed flow of free and forced convection was investigated experimentally and theoretically. Experiments were carried out in the upward turbulent flow between vertical parallel plates at different wall temperatures. In this condition, the aiding and opposing flows arose simultaneously on the heated and cooled sides, respectively, and a fully developed condition was established.Buoyancy effects on the mean velocity and temperature profiles, eddy diffusivities of heat and momentum, Nusselt number and friction factor, as well as the intensity of velocity and temperature fluctuations were examined, and the substantial effects of the buoyancy force were confirmed.In addition, an analytical model was proposed, based upon the damping factor concept of the turbulent fluctuations due to viscous action and buoyancy force. It is confirmed that the analytical model predicts the experimental results for the buoyancy effects on the turbulent transport process, and also partly explains the behavior of the turbulent properties.

NATURAL CONVECTION IN A VERTICAL CHANNEL: I. INTERACTING CONVECTION AND RADIATION. II. THE VERTICAL PLATE WITH AND WITHOUT SHROUDING

Numerical finite-difference solutions enabled the determination of heat transfer rates for pure natural convection and for Interacting natural convection and radiation in a vertical parallel plate channel of finite height. Attention was focused on the effect of the thermal boundary conditions and on the role of radiation as an enhancement mechanism. The results also enabled comparisons of the heat transfer from a single isothermal vertical plate with that for a plate that is shrouded by an adiabatic wall situated parallel to the plate. For pure convection and at intermediate and large Grashof numbers, the rate of heat transfer for a channel with two Isothermal equt-temperature walls exceeds by more than a factor of 2 that for a channel with one isothermal wall and one adiabatic wall (note that the ratio of active heat transfer areas for the two cases Is equal to 2). At lower Grashof numbers, the heat transfer rates differ only slightly. Radiation effects were explored for the case of a channel having one ...

Experiments on Natural Convection from Vertical Parallel Plates with Either Open or Closed Edges

Natural convection heat transfer from the face-to-face surfaces of parallel, square vertical plates was investigated experimentally. The experiments encompassed three types of hydrodynamic conditions along the lateral edges: (1) fully open to ambient, (2) blockage of one of the edge gaps, (3) blockage along both of the edge gaps. Measurements were made for ten interplate spacings. Use of a mass transfer measurement technique (the naphthalene sublimation technique) instead of direct heat transfer enabled elimination of radiation effects, extraneous connective/conductive heat losses, and variable property effects. The results for the fully open-edged case cast substantive doubt on the oft-quoted data of Elenbaas in the low range of the parameter (b/H)Ra, where b is the interplate spacing and H is the plate height. Uncertainties in Elenbaas’ results owing to large fluid property variations are also demonstrated (the present results correspond to constant properties). Suppression of fluid flow along one lateral edge gap generally has only a modest effect on the transfer coefficients and no effect for (b/H)Ra &gt; 4. When both edges are blocked, 30 percent (or more) reductions in the coefficients occur at lower (b/H)Ra. When (b/H)Ra &gt; 10, the lateral edge conditions do not affect the results.