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Conjugate Heat Transfer Predictions of Gas Turbine Hot Walls Jets Cooling: Influence of Short Hole Grid Resolutions Using Com.utational Fluid Dynam.cs*

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Journal of Power and Energy Engineering 2023年第10期11卷 1-16页

作者： abubakar m. el-jummah Shehu A. Abdulrahm.n Alhaji S. Grem. Departm.nt of m.chanical Engineering University of Maiduguri Maiduguri Nigeria Departm.nt of m.chanical Engineering Nigerian Army University Biu Borno Nigeria Departm.nt of Chem.cal Engineering University of Maiduguri Maiduguri Nigeria

Short hole investigations relevant to gas turbine (GT) hot walls cooling heat transfer techniques, were carried out using com.utational fluid dynam.cs (CFD) com.ined with conjugate heat transfer (CHT) code. The CFD software are com.ercial ones: ICEm.for grid m.delling and ANSYS Fluent for the num.rical calculation, where sym.etrical application prevails. The CFD CHT predictions were undertaken for Nim.nic-75 m.tal walls with square (152.4 m.) arrays of 10 holes, whereby the lum.ed heat capacitance m.thod was applied in order to determ.ne the surface average heat transfer coefficient (HTC), h (W/m.sup>2 K) and the dim.nsionless Nusselt num.er, Nu. The m.jor param.ters considered for the short hole geom.tries are the pitch to diam.ter, X/D and length to diam.ter, L/D ratios and both were varied with range of D values, but X of 15.24 m. and L of 6.35 m. kept constant. Also applied, are variable m.ss flux, G (kg/s∙m.sup>2) and were used in predicting the flow aerodynam.cs in the short holes. The predictions were for classic therm.l entry length into a round hole, as vena contracta, flow separation and reattachm.nt dom.nates the holes, hence the developm.nt of therm.l profile through the depth of the GT hot walls. Additionally, the acceleration of the flow along the wall surfaces as it approaches the holes, was a significant part of the overall heat transfer. This was shown to be independent of the hole length, even though the L/D param.ter is a critical com.onent to enhanced heat transfer. The CFD CHT predictions showed that validation of the HTC h, Nu and pressure loss, ∆P are in better agreem.nt with m.asured data and within reasonable acceptance. The ∆P agreem.nt signifies that the aerodynam.cs were predicted correctly, which is also the reason why the HTC expressed per wall hole approach surface area and Nu were better predicted. This illustrates how effective and efficient the wall internal heat transfer cooling is for gas turbine hot wall heat transfer

关键词： Lum.ed Heat Capacitance Therm.l Entry Length Sym.etrical Application Flow Separation Flow Reattachm.nt

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Developm.nt and Evaluation of the m.chanical Properties of Coconut Fibre Reinforced Low Density Polyethylene Com.osite

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Open Journal of Com.osite m.terials 2022年第3期12卷 83-97页

作者： Ahm.d m.ham.ed Bukar abubakar m.ham.ed el-jummah Abba Alhaji Ham.ajam Departm.nt of m.chanical Engineering University of Maiduguri Maiduguri Nigeria

This research work developed and evaluated the m.chanical properties of coconut fibre reinforced low density polyethylene (LPDE) com.osite m.terial. The effect of fibre loading on the m.chanical properties: tensile, flexural, and im.act of the developed com.osite m.terial have been investigated. Also carried out was the effect of fibre loading on the water absorptivity of the developed m.terial. Sam.le categories of the developed com.osite were prepared by varying the fibre contents by weight at 0%, 10%, 20%, and 30%. The aim.is to reduce the excessive waste disposal of LDPE m.terials that are largely found in the form.of disposed water package m.terials (or pure water sachets) that usually affects the environm.nt in the form.of pollution. The water retting process was applied in extracting and cleaning fibre (or coir), while the m.xed coir-LDPE (or developed com.osite m.terial) was prepared by Com.ression m.ulding Technique (Cm.). The tensile and flexural properties were tested using Hounsfield m.nsanto Tensom.ter (type w) while the im.act properties were tested using the Charpy Im.act testing m.chine. The m.crostructure of the com.osite was investigated using Scanning electron m.croscopy (SEm.. The fractured surface m.rphology of the com.osite sam.les indicated a hom.geneous m.xture of the coir fibre and LDPE m.trix. However, weak interfacial bonding between the coir fibre and LDPE m.trix was also observed. The analysis of the water absorptivity showed that the developed com.osite m.terials have low water absorptivity at low fibre loading. However, at higher fibre loading, the water absorptivity increases significantly.

关键词： Coconut Fibre Low Density Polyethylene Com.osite m.chanical Properties Water Absorptivity

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Experim.ntal Investigation on the Therm.l Properties of Gypsum.Plaster-Rice Husk Ash Com.osite

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Open Journal of Com.osite m.terials 2022年第4期12卷 131-138页

作者： Nuhu Caleb Am.lah abubakar m.ham.ed el-jummah Abba Alhaji Ham.ajam.Usm.n Ibrahim Departm.nt of m.chanical Engineering Faculty of Engineering University of Maiduguri Maiduguri Nigeria Departm.nt of m.chanical Engineering Faculty of Engineering Nigerian Army University Biu Nigeria Departm.nt of m.chanical Engineering Faculty of Engineering Ramat Polytechnic Maiduguri Nigeria

This experim.ntal investigation aim. at evaluating the therm.l properties of rice husk ash (RHA)—filled gypsum.plaster com.osite for potential applications, as insulating m.terials. The therm.l conductivities of com.osites of gypsum.plaster reinforced with RHA at 0%, 10%, 20%, 30%, and 40% volum. fractions were determ.ned experim.ntally using Lee’s disc m.thod. The experim.ntal results show that integrating RHA reduces the therm.l conductivity of gypsum.plaster and im.roves its insulation capacity. The results obtained from.the experim.nts were com.ared with the Rule of m.xture m.del, m.xwell m.del, and Russell m.del. It was observed that the therm.l conductivities obtained from.experim.nts and the theoretical m.dels decreased with an increase in the volum. fraction of RHA. The errors associated with the m.dels with respect to experim.ntal results are on the average of 28.7% for m.xture Rule, 31.6% for Russel m.del, and 18.8% for the m.xwell m.del. An agricultural waste like RHA can be beneficially used for the preparation of com.osites and, due to im.roved insulation capability, these com.osites can be used for applications such as insulation boards and sheathing, hardboard, ceilings of roofs, decorations, etc.

关键词： Rice Husk Ash Therm.l Conductivity Gypsum.Plaster Lee’s Disc m.thod Agricultural Waste

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The Green Com.osites: m.llet Husk Fiber (m.F) Filled Poly Lactic Acid (PLA) and Degradability Effects on Environm.nt

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Open Journal of Com.osite m.terials 2019年第3期9卷 300-311页

作者： Abba Alhaji Ham.ajam.abubakar m.ham.ed el-jummah Zahari Nur Ism.rrubie Departm.nt of m.chanical Engineering University of Maiduguri Maiduguri Nigeria Departm.nt of m.chanical and m.nufacturing Engineering Universiti Putra Malaysia Serdang Selangor Malaysia

This study provides an overview on green com.osites degradability. Practically, the m.in drawbacks of using natural fibers are their poor dim.nsional stability, degradability and high degree of m.isture absorption. While, end use of product from.natural fiber filled or reinforced com.osites has becom. subject of concern to m.terial engineers and scientist. The m.jor properties of natural fiber reinforced polym.r com.osites are greatly dependent on the hydrophilic tendency and dim.nsional stability of the fibers used, m.rphology aspect ratio for long fiber, while voids for powder fibers. The effects of chem.cal treatm.nts on cellulosic fibers that are used as reinforcem.nts for therm.plastics were studied. The chem.cal source for the treatm.nts is alkalization. The significance of chem.cally-treated natural fibers is seen through the im.rovem.nt of m.chanical properties. The untreated fiber com.osites degrade faster in m.nicipal soil com.ared to treated fiber com.osites.

关键词： Degradability Com.osite Fibers Poly Lactic Acid m.llet Husk

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Experim.ntal Investigation on the Therm.l Properties of Gypsum.Plaster-Rice Husk Ash Com.osite

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Open Journal of Com.osite m.terials 2022年第4期

作者： nuhu caleb am.lah abubakar m.ham.ed el-jummah abba alhaji ham.ajam.usm.n ibrahim

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