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The main objective of this study was to obtain the flow restricting capacity by determining their flow coefficients and to investigate the unsteady flow with low Reynolds number in the flow‐restricting devices such as orifices and capillary tubes having small diameters.

There is an enormous literature on the flow of Newtonian fluids through capillaries and orifices particularly in many application fields of the mechanical and chemical engineering. But most of the experimental results in literature are given for steady flows at moderate and high Reynolds numbers (Re>500). In this study, the unsteady flow at low Reynolds number (10<Re<650) through flow‐restricting devices such as orifices and capillary tubes having very small diameters between 0.35 and 0.70 mm were experimentally investigated.

The capillary tubes have much more capillarity property with respect to equal diameter orifices. Increasing the ratio of capillary tube length to tube diameter and decreasing the ratio of orifice diameter to pipe diameter before orifice increase the throttling or restricting property of the orifices and the capillary tubes. The orifices can be preferred to the capillary tubes having the same diameter at the same system pressure for the hydraulic systems or circuits requiring small velocity variations. The capillary tubes provide higher pressure losses and they can be also used as hydraulic accumulators in hydraulic control devices to attenuate flow‐induced vibrations because of their large pressure coefficients. An important feature of the results obtained for capillary tubes and small orifices is that as the d/D for orifices increases and the L/d reduces for capillary tubes, higher values C are obtained and the transition from viscous to inertia‐controlled flow appears to take place at lower Reynolds numbers. This may be explained by the fact that for small orifices with high d/D ratios and for capillary tubes with small L/d ratios, the losses due to viscous shear are small. Another important feature of the results is that the least variations in C for small orifices and the higher variations in C for capillary tubes occur when the d/D and L/d ratios are smallest. This has favourable implications in hydraulic control devices since a constant value for the C may be assumed even at relatively low values of Re.

To the authors' knowledge, there is not enough information in the literature about the flow coefficients of unsteady flows through capillary tubes and small orifices at low Reynolds numbers. This paper fulfils this gap.

The objective of this study is to investigate the feasibility of using selective laser melting (SLM) process to print fine capillary wick porous structures for heat pipe applications and clarify the interrelations between the printing parameters and the structure functional performance to form guidelines for design and printing preparation.

A new toolpath-based construction method is adopted to prepare the printing of capillary wick with fine pores in SLM process. This method uses physical melting toolpath profile with associated printing parameters to directly define slices and assemble them into a printing data model to ensure manufacturability and reduce precision loss of data model transformation in the printing preparation stage. The performance of the sample was characterised by a set of standard experiments and the relationship between the printing parameters and the structure performance is modeled.

The results show that SLM-printed capillary wick porous structures exhibit better performance in terms of pore diameter and related permeability than that of structures formed using traditional sintering methods, generally 15 times greater. The print hatching space and infilling pattern have a critical impact on functional porosity and permeability. An empirical formula was obtained to describe this impact and can serve as a reference for the design and printing of capillary wicks in future applications.

This research proves the feasibility of using SLM process to printing functional capillary wicks in extremely fine pores with improved functional performance. It is the first time to reveal the relations among the pore shapes, printing parameters and functional performance. The research results can be used as a reference for heat pipe design and printing in future industrial applications.

This study aims to propose a contactless and continuous dielectrophoretic cell-separation device using quadrupole electric field. To examine the separation performance, numerical simulations of the electric field in the cross-section of the glass capillary installed in the center of the quadrupole electrode were conducted.

To estimate the magnitude of the dielectrophoretic force induced on cells, electrostatic analysis was performed by using a boundary-fitted coordinate system.Distribution of the electric field and gradient of the electric field square in the cross-section of the glass capillary were simulated for various ratios of radii of the glass capillary to the electrode rod.

The distribution of the electric field was found to have a cone-like profile about the center axis of the glass capillary with maximum at the internal surface of the glass capillary. The magnitude of the gradient of electric field square had similar distribution as that of the electric field, but had steeper slope near the internal surface of the glass capillary. The optimal values of the ratio of radii and the applied voltage were also estimated to achieve the local electric field strength suitable for cell separation.

One major advantage of the proposed device is simple and low fabrication cost, in addition to its contactless structure free from cell damage. Derived knowledge is instructive in achieving high-throughput cell separation without the use of devices of complex structure.

This paper describes the tests performed to evaluate the solder capillary action which occurs within a gap between two solderable surfaces during soldering. The goal was to determine the optimal gap distance for maximum capillary flow in the attainment of hermetic solder joints capable of withstanding extreme temperature cycles and various mechanical shocks. One of the test conditions was arranged so that the gap thicknesses would vary while the width of the gaps remained constant. In a second condition, the gap thicknesses remained constant while the gap widths varied. Three plating designs were evaluated. They were nickel plating; nickel overplated with gold; and nickel, copper intermediate, with tin overplate. The capillary action of all three plating combinations deposited onto aluminium specimens, with the gap configurations previously described, was evaluated. The capillary results were measured with X‐ray and microstructural data. End use solder joint designs were determined from the capillary results. These designs are shown and they include the best plating design for the application. In addition, an unexpected result was obtained that is useful for testing the solderability of all finishes—the Configured Capillary Solderability Test.

A test procedure was developed to assess the capillary flow wettability of solders inside a confined geometry. The test geometry comprised two parallel plates with a controlled gap of constant thickness (0.008 cm, 0.018 cm, 0.025 cm and 0.038 cm). Capillary flow was assessed by: (1) the meniscus or capillary rise of the solder within the gap; (2) the extent of void formation in the gap; and (3) the time dependence of the risen solder film. Tests were performed with the lead‐free solders 95Sn‐5Sb, 96.5Sn‐3.5Ag, and 91.84Sn‐3.33Ag‐4.83Bi. The capillary rise of the lead‐free solders was less than that observed with the 63Sn‐37Pb control. Reducing the solder surface tension and contact angle improved capillary flow. Void formation by the non lead solders increased as the gap became smaller. The extent of voiding was determined primarily by the gap size rather than the wettability parameters (contact angle or surface tension) of the individual alloys.

Presents a fully coupled numerical model to simulate the slow transient phenomena involving heat and mass transfer in deforming partially saturated porous materials. Makes use of the modified effective stress concept together with the capillary pressure relationship. Examines phase changes (evaporation‐condensation(, heat transfer through conduction and convection, as well as latent heat transfer. The governing equations in terms of gas pressure, capillary pressure, temperature and displacements are coupled non‐linear differential equations and are discretized by the finite element method in space and by finite differences in the time domain. The model is further validated with respect to a documented experiment on partially saturated soil behaviour, and the effects of two‐phase flow, as compared to the one‐phase flow solution, are analysed. Two other examples involving drying of a concrete wall and thermoelastic consolidation of partially saturated clay demonstrate the importance of proper physical modelling and of appropriate choice of the boundary conditions.

This paper aims to describe how successfully a particular restrictor delivers its best in increasing the conical journal bearing performance. The restrictors are used in the hole-entry conical journal bearing subjected to hybrid mode. Thus, the restrictors, like constant flow valve (CFV), orifice and capillary, are studied comparatively.

Numerical simulation for the bearing results with the three restrictors are obtained by using finite element method (FEM) under the well-known modified Reynolds equation.

When the hole-entry conical journal bearings, with the restrictor design parameter range C¯_s2 = 0.03 – 0.09, are operated, the results obtained are quite distinctive and significant. It indicates that the CFV restrictor-based conical bearing gives enhanced performance in comparison to orifice and capillary restrictors. Moreover, it suggests the performance-wise sequence of the restrictors in hybrid bearings as CFV > Orifice > Capillary.

The outcome of the research paper will give insight to help the bearing designer to choose the particular restrictor in hybrid conical bearing depending on the industrial need.

This work aimed at studying the use of capillary forces as a gripping principle in the handling of sub‐millimetric sized components. The goal was to present the results as design rules of so‐called capillary grippers.

Each parameter (surrounding environment, materials, volume of liquid, separation distance, gripper geometry and gripper size, relative orientation of the gripper with respect to the component) has been quantified, either numerically or experimentally. In some validation cases, both means have been used.

The capillary forces can be modified between a maximum F_max and a minimum F_min so that a component with any mass m between F_min/g and F_max/g can be picked up and released.

By comparison with some existing capillary grippers prototypes, this work is only a theoretical and experimental study. Nevertheless, its originality lies in the exhaustive study and quantification of all parameters so that most of the capillary grippers of the literature can be explained or improved with these results.

The main implication of the capillary gripping is that it provides an alternative to existing gripping principles (vacuum grippers, tweezers). This principle is strong enough (a few mN) and well adapted to pick up components with only one free accessible surface. The scaling laws are the most favorable (F∼L). It provides a “soft” picking, avoiding high contact forces.

The originality lies in the exhaustive quantification of the role of each parameter. These results can be used by researchers and designers.

An integral component in heat pipes (HPs) and vapor chambers (VCs) is a porous wicking structure. Traditional methods for manufacturing wicking structures within HPs and VCs involve secondary manufacturing processes and are generally limited to simple geometries. This work aims to leverage the unprecedented level of design freedom of laser powder bed fusion (LPBF) additive manufacturing (AM) to produce integrated wicking structures for HPs and VCs.

Copper wicking structures are fabricated through LPBF via partial sintering and via the formation of square, hexagonal and rectangular arrangements of micro-pins and micro-grooves, produced in multiple build directions. Wicks are characterized by conducting capillary performance analysis through the measurement of porosity, permeability and capillary rate-of-rise.

Copper wicking structures were successfully fabricated with capillary performance, K/reff, ranging from 0.186–1.74 µm. The rectangular-arrangement micro-pin wick presented the highest performance.

This work represents the first published report on LPBF AM of copper wicking structures for HPs/VCs applications and represents foundational knowledge for fabricating complete assemblies of copper VCs and HPs through LPBF AM.

This paper aims to present experimental and finite volume method (FVM)-based simulation studies on the scaling effect on the capillary contact angle and entrant pressure for a three-dimensional encapsulation process of ball-grid array (BGA).

With the development of various sizes of BGA packages, the scaling effect of BGA model on capillary underfill (CUF) process is investigated together with the influences of different industrial standard solder bump arrangements and dispensing methods used as case study.

The experimental results agree well to the simulation findings with minimal deviation in filling time and similar flow front profiles for all setups. The results revealed that the capillary contact angle of flow front decreases in scale-up model with larger gap height observed and lengthens the encapsulation process. Statistical correlation studies are conducted and accurate regression equations are obtained to relate the gap height to the completion filling time and contact angle. CUF threshold capillary pressures were computed based on Leverett-J function and found to be increasing with the scale size of the package.

These statistical data provide accurate insights into the impact of BGA’s scale sizes to the CUF process that will be benefiting the future design of BGA package. This study provided electronic designers with profound understanding on the scaling effect in CUF process of BGA, which may be extended to the future development of miniature-sized BGA and multi-stack device.

This study relates the flow behaviour of encapsulant to its capillary contact angle and Leverett-J pressure threshold, in the CUF process of different BGA and dispensing conditions. To date, no research has been found to predict the threshold pressure on the gap between the chip and substrate.