Inordertoachieveacomprehensiveoverviewofpressuredropinsmallpipes,twoexperimentalrigsweredesignedandbuildtoexamine5smallpipesofboth1,2,3,4and5mminnerdiameter.Figure1showsthetestrigforthe2and4mminnerdiameterpipes.Asimilarexperimentalrigwasalsodesignedandmanufacturedtoexaminethepipesof1mm,3mm,and5mmdiameter.EachtestrigwasmanufacturedfromtwothicksheetsofPerspex(25mm)wereinitiallymachinedflatbeforemachiningofthesettlingchamber.Thepipesof450mmlengthwerethencreatedusingballnosecuttersofappropriatediameter.Valveholesandassemblyholeswherethendrilled.TheCNCmachinewasusedtominimizetheerrorindimensionsandallowsforprecisionfeaturestobemachined.Theholeswerethentappedbyhandusingtappingtools.Therigwascleanedbeforethehydrophobiccoatingwasappliedtopipes.TheLT-8hydrophobicsolutionproducedmicro-postsintheorderofNano-metresheightonthesurfaceofthechannel.
ExperimentalProcedure
Thetestrigwasplacedonalargetabletominimizethedifferenceinlevelbetweentheinletandoutletofpipes.However,thedistancebetweenthefloorandthefourcornersofthetablewasmeasuredtoconfirmthehorizontallevel.Thelevelofwaterinthetankkeptconstantbyusingafloatingballvalve.Thewaterflowratecontrolledbyavalvesystemallowsflowratetobecontrolledineachpipeindividually.Theflowexitingeachpipewillbecollectedinagraduatedcylinderforaspecifictimetocalculatetheflowrate.ThedatawillthenbeusedtoevaluatethevelocityoftheflowandthenusedtocalculatetheReynoldsnumber.Thevaluesofheightfromthemanometerreadings,h,willbeusedtocalculatethepressuredifferenceduetofrictionlossesoftheflowwithineachpipeusingEquation1,\(P=\rho gh\)(1)Thewatertankwillthenbeelevated,andtheexperimentrepeated.Thechangeofelevationofthewatertankisusedtocontroltheflowrate(Reynoldsnumber)inthepipes.TherelationshipbetweenthepressuresineachpipeandReynoldsnumberwillthenbegraphicallypresented.Forthepipeof2and4mmdiameter,datawillalsoberecordedfor½coatedpipes.Datawillthenbecomparedtothatofcoatedandnon-coatedpipes.Highdefinitionimageryrecordingwillbetakenoftheflowineachpipeinordertoexaminetheeffectofcoatingonflowproperties.Theimagerywillcapturevideoatarateor100framespersecond.