Study of Langmuir monolayers and Langmuir-Schaefer films based on symmetrical meso-aryl-substituted porphyrin derivative

This paper presents the results of a study of meso-aryl-substituted porphyrin Langmuir monolayers by the method of compression isotherms. Experimental data were used to plot the dependences of the compression modulus (C−1) on the specific area. Monolayers at specific surface pressure were transferred to solid substrates and investigated. The monolayers were transferred to the surface of monocrystalline silicon at surface pressures of 8, 25, and 60 mN/m and examined them by atomic force microscopy (AFM) in a semi-contact mode. It was found that with an increase in the transfer pressure, the coarsening of molecular aggregates occurs. The smallest roughness is observed for a porphyrin film formed and transferred at a pressure of 8 mN/m.

Numerical analysis of heat transfer and fluid flow around circular and non-circular tubes

A two-dimensional study of turbulent flow and heat transfer in a channel with circular and non-circular tubes has been carried out using the CFD Fluent software package. Four non-circular tubes were investigated: flat, ellipse, cam, and drop-shaped. Reynolds number varied in the range of 7300 ≤ Re ≤ 14600. All tubes were investigated under similar operating conditions. Local heat transfer, pressure, and friction coefficients over a surface of the tubes were presented. The thermal-hydraulic performance was used to estimate the efficiency of the non-circular tubes. The results indicated that the drop-shaped tube has the best thermal-hydraulic performance, which was about 5.6, 2.6, 1.7, 1.3 times higher than that of the circular, flat, ellipse, cam tube, respectively.

An analysis of tube thickness effect on shell and tube heat exchanger

Heat exchangers are important equipment for the process of placing heat. The most widely used type of heat exchanger is shell and tube. This type is widely used because of its simple and easy design. Design of shell and tube heat exchangers is done by the side or shell variations to get the desired performance. Therefore, research is conducted to study the effect of tube thickness on heat transfer, pressure drop, and stress that occurs in the shell and tube heat exchanger so that the optimal tube thickness is obtained. In this research, the activities carried out are the design of heat exchangers for the production of oxygen with a capacity of 30 tons/day. The standard used in this study is the 9th edition heat exchanger design guidance document compiled by the Tubular Exchanger Manufacturer Association (TEMA). Analysis of the tube thickness effect on heat transfer, pressure drop, and stress was carried out using the SimScale platform. The effect of variations in tube thickness on heat transfer is that the thicker the tube, the lower the heat transfer effectiveness. The highest value of the heat exchanger effectiveness is 0.969 at the tube thickness variation of 0.5 mm. The lowest value of the heat exchanger effectiveness is 0.931 at the tube thickness variation of 1.5 mm. The effect of variations in tube thickness on pressure drop is that the thicker the tube, the higher the pressure drop. The highest value of pressure drop is in the variation in tube thickness of 1.5 mm, 321 Pa. The lowest value of drop pressure is in the variation of 0.5 mm tube thickness, which is 203 Pa. The thickness of the tube also increases the maximum stress on the components of the shell, head, tubesheet, baffle, and saddle, but the value is fluctuating

Numerical Design and Laboratory Testing of Encapsulated PCM Panels for PCM-Air Heat Exchangers

Heat transfer between encapsulated PCM panels and air plays an important role in PCM-Air heat exchangers. A new design for the encapsulation panel was developed considering practical aspects such as the cost of production and ease of manufacturing, in addition to heat transfer and pressure drop. A number of encapsulated panel surfaces were first investigated via 3D CFD simulations and compared with an existing panel in use by a commercial PCM-Air heat exchanger manufacturer. After validation, 2D CFD simulations were carried out for 32 different geometries to select the most effective design, which was fabricated and tested in the laboratory. Laboratory parameters tested included heat transfer, pressure drop and melting/solidifying. The laboratory results confirmed the improvements of the new panel in comparison with the existing panel and a flat panel. It was found that the proposed design doubled the heat transfer, holds 13.7% more material and the fan can overcome the increased pressure drop.

Working Body for Deformation of Thin-Walled Pipe Billets

In this paper we consider different types of working bodies and fillers used in the manufacture of hydro-gas systems of aircraft from thin-walled pipe billets, and also explored the advantages and disadvantages of liquid, fusible, solid, elastic, loose and combined fillers in the deformation of pipe segments by means of distribution, crimping, forming and flexible. As a result of the research, a device for distributing pipe billets along a rigid matrix and a working body made of granular polyurethane and ice, the main advantages of which are: good rheological properties (fast flow); high ductility and viscosity; high ability to transfer pressure throughout the metal zone; ability to withstand high compression load; ease of entry into the workpiece and removal from the finished part; low production costs.

Molding Recipe Study for MUF Solder Crack Improvement

In recent years, flip chip technology becomes more and more important with benefits of thin package profile, reduction of package outline, and excellent electrical and thermal performance by connection of copper pillar bumps (CuP) or C4 solder bumps. In order to fill the die gap to prevent voids problem, two encapsulated solutions could be applied: capillary underfill (CUF) and molded underfill (MUF). In general comparison, CUF means to dispense underfill first to fill in die gap then proceed over-molding afterward; and MUF is directly fill under and above die by mold compound. The advantages of MUF solution are low cost and high throughput, however, it will suffer other assembly issues such as solder extrusion and solder crack, and might result in potential function failure. To form these kinds of defects, we suspected that solder will plastically deform under thermal stress treatment, which comes from unbalance mold transfer pressure and material expansion stress during thermal process. In this article, we have tried to investigate the mechanism of solder crack through molding recipe DOE (Design of Experiment) and mold flow simulation. The test vehicle is 12 × 12 mm2 FCCSP, with 6 × 5 mm2 die size. The bump type is copper pillar bump and pitch/size are 126 um and 35 × 60 um2, respectively. The molding recipe has been evaluated by cross section, and it revealed that molding transfer time and molding temperature are directions toward improvement of solder crack issue.