On tuning a reactive silencer by varying the position of an internal membrane

A mode-matching method is used to investigate the performance of a two-dimensional, modified reactive silencer. The modification takes the form of a membrane which is attached to the internal walls of the expansion chamber parallel to the axis of the inlet/outlet ducts. The height of the membrane above the level of the inlet/outlet ducts can be varied and, by this means, the device is tuned. It is shown that the stopband produced by the silencer can be broadened and/or shifted depending upon the height to which the membrane is raised. Attention is focused on the efficiency of the device at low-frequencies - the regime where dissipative silencers are usually least effective. The potential use of the device as a component in a hybrid silencer for heating ventilation and air-conditioning (HVAC) ducting systems is discussed

Advances in simulated moving bed chromatographic separations

The development of some unconventional Simulated Moving Bed (SMB) strategies, such as the introduction of nonsynchronous inlet/outlet shifts (the Varicol process), variable flux or variable composition in the inlet/outlet streams (PowerFeed and Modicon, respectively), and also the use of multiple feed or distributed feed, have increased the potential of this technique for a wide range of binary separations. For multiple component separations, different strategies has been investigated, including a cascade of SMB, more complex SMB units composed by several adsorption zones, and the JO process operating in two different separation steps

The use of impulse response tracer experiments in horizontal subsurface flow constructed wetland development

A research proposal submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in fulfillment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2016In the past three decades there has been an increased interest in constructed wetlands (CW) and their effectiveness in treating water. The hydraulic efficiency of a CW can be determined by using chemical reactor theory to develop residence time distribution (RTD) parameters such as effective volume (Veff), normalized variance (σ2) and mean residence time (τm). Five experiments were conducted to study the effects on these RTD parameters in a CW by using a glass pilot-scale laboratory rig and varying the inlet-outlet positions. The rig made use of a glass tank 250x250x500mm filled with clear superabsorbent polymer balls as a packing. The clear tank and balls made it possible for the flow to be observed when a FWT red impulse tracer dye was inserted into the system. The flow was photographed at specific time intervals for visual analysis and comparison. . The visual results showed the formation of a hull-shaped velocity profile in all the experiments. The RTD was obtained by collecting tracer samples at specific outlet positions during the course of each experiment. The five inlet-outlet configurations RTD parameters results showed; a straight flow path from a single inlet to outlet yielded the lease desirable hydraulic performance with dead volumes contributing to up to 67% of the CW. An increase in the number of outlets and changing the direction of flow diagonally showed up to a 96% improvement to the effective volume of the system could be achieved when compared with single inline inlet-outlet flow. The best result was achieved by combining the visual and RTD data to make changes to the rigs geometry in order to eliminate dead zones and yielded up to a 148% improvement in the effective volume of the system when compared with single inline inlet-outlet flow. A well designed CW with respect to inlet-outlet position can result in reduced land requirements and construction costs by minimizing the dead volume and improving hydraulic efficiency.MT201

The Entrance Effect of Pin Type Flow Channel on Direct Methanol Fuel Cells

[[abstract]]This research alters the traditional single inlet/outlet opening of the pin type flow channel of direct methanol fuel cells (DMFCs). Multi-inlet/outlet openings are designed with the aim to distribute the methanol solution evenly and effectively remove CO2 bubbles and to improve the cell performance. The CO2 bubble dynamics in anode flow channels and the cell performance are investigated. Results show that the newly designed flow channels can overcome restrictions resulting from fuel and effectively remove CO2 bubbles, thereby enhancing the performance of the pin type DMFC. The “three-inlet and three-outlet” design increases the current density output by 19%.[[incitationindex]]SCI[[booktype]]紙

PROSES PEMBUATAN SALURAN MASUK SALURAN KELUAR DAN SISIR PADA MESIN PERAJANG KRUPUK RAMBAK

Mesin perajang krupuk rambak yang terdiri dari saluran masuk saluran keluar dan sisir merupakan bagian luar mesin yang juga berfungsi sebagai penutup mesin dan melindungi pekerja dari bagian dalam mesin yang berputar. Tujuan dari Proyek Akhir pembuatan saluran masuk, saluran keluar dan sisir adalah (a) mengetahui bahan yang digunakan, (b) mengetahui proses pembuatan, (c) mengetahui proses penyambungan antar komponen serta perakitan saluran masuk saluran keluar dan sisir dengan rangka, (d) mengetahui berapa lama waktu yang dibutuhkan untuk pengerjaan saluran masuk, saluran keluar dan sisir, (e) menggetahui berapa lama waktu yang dibutuhkan untuk perakitan komponen dengan rangka. Metode yang digunakan dalam pembuatan komponen meliputi identifikasi gambar kerja, identifikasi bahan, dan identifikasi mesin serta alat perkakas. Tahapan pembuatan meliputi pemilihan bahan, persiapan bahan, pemotongan, pengeboran, pembentukan, penyambungan dan penyelesaian permukaan. Dengan adanya metoda-metoda tersebut, diharapkan dapat membuat komponen yang sesuai dengan gambar kerja dan dapat berfungsi dengan baik. Bahan yang digunakan untuk membuat saluran masuk, saluran keluar dan sisir adalah plat stainless steel dengan tebal 1,2 dan 1,5mm. Proses pembuatan meliputi: Proses persiapan bahan, proses pemotongan, proses pengeboran, proses pembentukan, proses penyambungan, proses finishing. Perakitan saluran masuk, saluran keluar dan sisir dengan rangka menggunakan sambungan baut. Waktu yang diperlukan untuk proses pembuatan saluran masuk adalah ± 115 menit, waktu yang diperlukan untuk proses pembuatan saluran keluar adalah ± 115 menit., dan waktu yang diperlukan untuk proses pembuatan sisir adalah ± 395 menit

Experimental investigation of non-uniform heating on flow boiling instabilities in a microchannels based heat sink

Two-phase flow boiling in microchannels is one of the most promising cooling technologies able to cope with high heat fluxes generated by the next generation of central processor units (CPU). If flow boiling is to be used as a thermal management method for high heat flux electronics it is necessary to understand the behaviour of a non-uniform heat distribution, which is typically the case observed in a real operating CPU. The work presented is an experimental study of two-phase boiling in a multi-channel silicon heat sink with non-uniform heating, using water as a cooling liquid. Thin nickel film sensors, integrated on the back side of the heat sinks were used in order to gain insight related to temperature fluctuations caused by two-phase flow instabilities under non-uniform heating. The effect of various hotspot locations on the temperature profile and pressure drop has been investigated, with hotspots located in different positions along the heat sink. It was observed that boiling inside microchannels with non-uniform heating led to high temperature non-uniformity in transverse direction

Design, fabrication, and testing of micromachined silicone rubbermembrane valves

Technologies for fabricating silicone rubber membranes and integrating them with other processes on silicon wafers have been developed. Silicone rubber has been found to have exceptional mechanical properties including low modulus, high elongation, and good sealing. Thermopneumatically actuated, normally open, silicone rubber membrane valves with optimized components have been designed, fabricated, and tested. Suspended silicon nitride membrane heaters have been developed for low-power thermopneumatic actuation. Composite silicone rubber on Parylene valve membranes have been shown to have low permeability and modulus. Also, novel valve seats were designed to improve sealing in the presence of particles. The valves have been extensively characterized with respect to power consumption versus flow rate and transient response. Low power consumption, high flow rate, and high pressure have been demonstrated. For example, less than 40 mW is required to switch a 1-slpm nitrogen flow at 33 psi. Water requires dose to 100 mW due to the cooling effect of the liquid

On pressure and velocity flow boundary conditions and bounceback for the lattice Boltzmann BGK model

Pressure (density) and velocity boundary conditions inside a flow domain are studied for 2-D and 3-D lattice Boltzmann BGK models (LBGK) and a new method to specify these conditions are proposed. These conditions are constructed in consistency of the wall boundary condition based on an idea of bounceback of non-equilibrium distribution. When these conditions are used together with the improved incompressible LBGK model by Zou et al., the simulation results recover the analytical solution of the plane Poiseuille flow driven by pressure (density) difference with machine accuracy. Since the half-way wall bounceback boundary condition is very easy to implement and was shown theoretically to give second-order accuracy for the 2-D Poiseuille flow with forcing, it is used with pressure (density) inlet/outlet conditions proposed in this paper and in Chen et al. to study the 2-D Poiseuille flow and the 3-D square duct flow. The numerical results are approximately second-order accurate. The magnitude of the error of the half-way wall bounceback is comparable with that using some other published boundary conditions. Besides, the bounceback condition has a much better stability behavior than that of other boundary conditions.Comment: 18 pages, one figur