Wavy Plate Research Articles

Exergy method of optimisation of a wavy plate indirect evaporative cooler

The present paper deals with the performance optimisation of a wavy plate surface of indirect evaporative coolers with cooling capacities of 10, 25, 45 kW. Based on the minimum entropy generation rate and by applying a number of geometrical constraints, as well as using a search method, the optimum apparatus's dimensions and the secondary air discharge and the primary air mass flow rates are calculated. The numerical results show that, to increase the cooling load of an indirect evaporative cooler, the optimisation of the above mentioned parameters by this method can increase energy efficiency by up to 65%.

Heat sinks with fluted and wavy plate fins in natural and low-velocity forced convection

The effect on heat transfer of geometrically rearranging the surface area of a finned heat sink is investigated. Novel heat sinks with fluted and wavy plate fin configurations are designed and fabricated together with conventional longitudinal-plate and pin fin heat sinks. The experimental apparatus, consisting of the guard heater assembly, isolation chamber, wind tunnel, and data acquisition instrumentation, is described. The thermal performance of the novel and conventional heat sinks is measured and compared for the horizontal and vertical base plate orientations under natural and low-velocity forced convection conditions. Results, presented as the Nusselt number against the Rayleigh or Reynolds numbers, reveal that the pin fin heat sink generally outperforms the other heat sinks, when the heat sink surface area is held constant. A significant effect on heat transfer of the orientation of the forced flow with respect to the buoyancy flow is observed. Overall, the novel heat sink designs do not yield significantly better thermal performance than an optimized conventional longitudinal-plate heat sink.

Combined Free and Forced Convection Film Condensation on a Finite-Size Horizontal Wavy Plate

Abstract Mixed-convection film condensation with downward flowing vapors onto a finite-size horizontal wavy plate is studied by a simple mathematical model and the spline alternating-direction implicit method. Effects of the wavy geometry, the interfacial vapor shear and the pressure gradient on the local condensate film thickness and the heat transfer characteristics have been studied independently. Results show that the pressure gradient tends to increase the heat transfer rate and to decrease the influence of the wavy amplitude. The appropriate wave number which can enhance the maximum condensation heat transfer rate is found in the neighborhood of lunder all circumstances.

Actomyosin promotes cell plate alignment and late lateral expansion in Tradescantia stamen hair cells.

Cytokinesis in higher-plant cells involves the formation of a cell plate in the interzone between the separating chromatids. The process is directed by the phragmoplast, an array of microtubules, actin filaments, and membranous elements. To determine if the role of actin in cytokinesis is dependent on myosin, we treated stamen hair cells of Tradescantia virginiana L. with 2,3-butanedione monoxime (BDM), an inhibitor of myosin ATPase and ML-7, a specific inhibitor of myosin light-chain kinase. Treatment with BDM resulted in a tilted cytokinetic apparatus during early initiation and a wavy cell plate with curved phragmoplasts during late lateral expansion. Treatment with ML-7 also resulted in inefficient late lateral expansion of the cell plate, with effects ranging from slower expansion to complete inhibition. Taken together, these results implicate myosin in the control of cell plate expansion and alignment.

Effects of Stimulus Blocking, Light Scattering, and Distortion on Multifocal Electroretinogram

Purpose: To investigate how the multifocal electroretinogram (ERG) is altered in conditions of blocking, light scattering, or distortion of the stimulus that are seen in ocular pathologies. Methods: A central 40°-diameter stimulus pattern consisting of 61 hexagons was presented on a cathode ray tube monitor at a rate of 75 Hz according to the pseudo-random binary M sequence by the Veris computer program. Localized responses corresponding to each hexagon and ERG topographies were displayed on the computer screen. Central scotoma was simulated by blocking the central area of the stimulus, visual field constriction by blocking the outer area of the stimulus, mild cataract by using acrylic filters that caused light scatter, and epiretinal membrane by using a wavy plastic plate that produced metamorphopsia. Results: The responses from the blocked area were nonrecordable whether blockage was central or peripheral; responses from the adjacent unblocked area had a larger amplitude when large areas of the stimulus were blocked. The light scatter that decreased vision from 20/20 to 20/70 did not significantly decrease response amplitudes. Responses from areas in which the stimulus pattern was distorted were minimally affected. Conclusions: The results show that the system records local ERGs from the macula and outside the macula. It can detect the area where the stimulus is blocked. Moderate light scattering and distortion do not cause loss of local ERG characteristics.

Second-Law Analysis on Wavy Plate Fin-and-Tube Heat Exchangers

Second-law analysis on the herringbone wavy plate fin-and-tube heat exchanger was conducted on the basis of correlations of Nusselt number and friction factor proposed by Kim et al. (1997), from which the entropy generation rate was evaluated. Optimum Reynolds number and minimum entropy generation rate were found over different operating conditions. At a fixed heat duty, the in-line layout with a large tube spacing along streamwise direction was recommended. Furthermore, within the valid range of Kim et al.’s correlation, effects of the fin spacing and the tube spacing along spanwise direction on the second-law performance are insignificant.

Laminar film condensation on a finite-size horizontal wavy plate

A theoretical analysis of two-dimensional, steady laminar film condensation on a finite-size horizontal wavy plate is studied for the case in which a cold plate faces upwards. The present study considers that the wavy characteristic length, amplitude and the depth of boundary layer at the plate edge is equal to a minimum depth. The dimensionless heat transfer coefficients and the dimensionless film thickness along the surface are found to be functions of five parameters: dimensionless wave length and amplitude, Pr, Ja and Ra.

Natural convection along a wavy vertical plate to non-Newtonian fluids

A numerical investigation of natural convection flow along irregular vertical surfaces in non-Newtonian fluids is reported. A wavy vertical surface is used as an example to show the heat transfer mechanism near such surfaces. The results demonstrate that with an increase of flow index, the axial velocity increases, but the velocity boundary layer becomes thinner. The difference between the velocity in the crests and the troughs is indiscernible. The boundary layer around nodes is getting thicker compared to that of the crests and the troughs. When the natural convection boundary layer grows thick, the amplitude of the local Nusselt number gradually decreases. The effects of Prandtl number, flow index and surface amplitude in non-Newtonian fluids are also discussed in detail.

Heat Transfer and Friction Correlations for Wavy Plate Fin-and-Tube Heat Exchangers

This paper deals with heat exchangers having plate fins of herringbone wave configuration. Correlations are developed to predict the air-side heat transfer coefficient and friction factor as a function of flow conditions and geometric variables of the heat exchanger. Correlations are provided for both staggered and in-line arrays of circular tubes. A multiple regression technique was used to correlate 41 wavy fin geometries by Beecher and Fagan (1987), Wang et al. (1995), and Beecher (1968). For the staggered layout, 92 percent of the heat transfer data are correlated within ±10 percent and 91 percent of the friction data are correlated within ±15 percent.

Transient free convection of non-Newtonian fluids along a wavy vertical plate including the magnetic field effect

A Prandtl transformation method is applied to study the transient free convection of non-Newtonian fluids along a wavy vertical plate in the presence of a magnetic field. A simple transformation is proposed to transform the governing equations into the boundary-layer equations and solved numerically by the cubic spline approximation. A simple coordinate transformation is employed to transform the complex wavy surface to a vertical flat plate for a constant wall temperature by the numerical method. The effects of the magnetic field parameter, the wavy geometry and the non-Newtonian nature of the fluids on the flow characteristics and heat transfer are discussed in detail.

Some new stable one-dimensional quasicrystals in an Al65Cu20Fe10Mn5 alloy

Structure types and fine structures of the stable one-dimensional (1D) quasicrystals (QCs) in an Al65Cu20Fe10Mn5 alloy have been studied using transmission electron microscopy. The 1D QCs are intimately related to a prototype decagonal quasicrystal (DQC) and may be described by introducing appropriate linear phason strains into the DQC. In the present work we have observed three types of 1D QC with lattice parameters of a1=8 0.23nm=1.84 nm,c= 1.2 nm,a2=18 0.23 nm = 4.14 nm,c2=1.2 nm and a3=13 0.23 nm = 2.99nm,c3= 1.2 nm respectively, where c1=c2=c3 is the period along the original tenfold axis (A10) of the prototype DQC and a1, a2 are the periods along one of the A2P axes of the prototype DQC with different 3 linear phason strains. The multiplicative values before 0 .23 nm for a1 and a3 belong to the numbers of one type of Fibonacci sequence with N=1 and N1=3, while that for a2 belongs to a number of another type of Fibonacci sequence with N0=1 and N= 3. The latter two 1D QCs are discovered for0 1 the first time. Chalk-like needle domains along the A10 direction and wavy thin plate domains perpendicular to the A10 direction have been observed in some regions of the 1D QC.

Natural convection of non-Newtonian fluids along a wavy vertical plate including the magnetic field effect

A Prandtl transformation method is applied to study the natural convection of non-Newtonian fluids along a wavy vertical plate in the presence of a magnetic field. A simple transformation is proposed, to transform the governing equations into the boundary layer equations, and solved numerically by the cubic spline approximation. A simple coordinate transformation is employed to transform the complex wavy surface to a vertical flat plate for a constant wall temperature by the numerical method. The effects of the magnetic field parameter, the wavy geometry and the non-Newtonian nature of the fluids on the flow characteristics and heat transfer are discussed in detail. It is found that the action of the magnetic field is to decelerate the flow, thus decreasing the Nusselt number.

Contact resistance in air-cooled plate fin-tube air-conditioning condensers

Test equipment and procedures have been developed to measure the heat transfer performance of an industry-standard wavy plate fin-tube condenser, and to compare it with alternative designs. Two test rigs were employed: one used direct electric heating, and the other used an R22 thermosyphon. Analysis revealed that the standard production heat exchanger suffered from excessive fin-tube resistance. This was confirmed by sectioning and microscopic examination. Seven different designs were compared at the same Reynolds number. The results were analysed to isolate the air-side heat transfer coefficient.

The dynamic modelling of elastic wavy plates

The aim of the contribution is to formulate an engineering theory describing the dynamic behaviour of periodically waved shell-like elements, called wavy plates. On the basis of the proposed theory, the effect of coupling between free macro- and micro-vibrations of a wavy plate is investigated. It is also shown that the homogenized model of wavy plates (obtained by scaling down the wavelength parameters) cannot be applied in the analysis of dynamic problems.

Surface Treatments to Reduce Friction: Rubber Glove Applications

Abstract The frictional properties of rubber surfaces modified by various treatments have been investigated in order to understand the factors which reduce the friction and give the surface appropriate qualities for practical use. The study was in two stages. Initial measurements were made on thin sheets of hot-vulcanized natural rubber; then followed tests on latex glove material to see how the initial results and understanding related to the application. Measurements of friction coefficient were made against a wavy glass plate, giving reproducible results, and against finger skin. Supplementary measurements were made of surface roughness and hardness, liquid contact angle, and water absorption. Factors of importance in the reduction of dry friction were found to be an increased surface roughness and hardness. In practice, difficulties may be experienced under slightly wet or damp conditions, which can increase the friction above the dry value. Here it was found to help if the surface treatment could absorb water. For surgeons' gloves in contact with moist skin, one particular treatment, a hydrogel polymer coating, gave the necessary surface roughness, hardness, and water absorptivity, making the gloves easy to don and pleasant to wear.

Thin film flowing down a curved surface

The film flow down a curved surface is analysed by an orthogonal curvilinear system and a perturbation in the small ratio of film thickness to minimum radius of curvature. General solutions are obtained to second order. The results are applied to plates with exponential curvature and sinusoidal curvature. Separation is most likely to occur on the upstream sides of a wavy plate.

Response of variations of free stream velocity on inviscid and incompressible flow past a wavy plate

This paper studies the several types of free stream flow past the wavy plate. The solution is obtained in terms of free stream function by regular perturbation. It may be noted that the introduction of small vorticity does not affect the primary flow due to uniform free stream; however it tends to increase the maximum pressure at the wall. As in the case of uniform free stream, the extrema of the pressure coefficient along the X-direction coincide with those of the wall. The perturbed flow fields due to the presence of the wavy shaped boundary die out transversally at the same rate as in case of uniform stream.

Drag due to a striated boundary in slow Couette flow

A highly viscous fluid separates a smooth plate moving in its own plane and a wavy plate. Due to the wavy striations, the mean flow is decreased and the mean drag is increased. The waviness makes the fluid appear to be anisotropic.

Unsteady boundary layer flows induced by a wavy plate

Unsteady boundary layer flows generated in an incompressible, homogeneous, nonrotating viscous fluid bounded by a rigid wavy plate are studied theoretically. The Laplace transform method is employed to obtain exact solutions of the unsteady boundary layer equations in a wavy plate configuration. The structures of the unsteady velocity distribution and the associated boundary layers are determined explicitly and several particular solutions are recovered as special cases of this analysis. The physical interpretation of the mathematical results are examined.

The impulsive motion of a wavy plate in a conducting fluid

This paper describes the nonsteady phenomena occurring when a thin plate with sinusoidal shape at both sides and moving with velocityU 0 in an inviscid fluid with uniform velocityU 0 is suddenly brought to rest in a magnetic fieldB 0 parallel toU 0. After it has been shown that the appropriate initial condition for the flow is the nonmagnetic potential flow, the problem is, for the cases where the phase difference between upper and lower side is 0 andπ, formulated in terms of the stream function for the flow and the vector potential for the magnetic field. The governing equations are linearized and solutions valid for large time are found by means of Laplace transformations.