Morefundamentalstudies are needed concerning the effectof hydrodynamics
in tankcleaning processes. CFDhas beenshown to be a useful tool for the
optimisationof the hygienicdesign of plain,closedprocess equipment (Jensen,
2003).A combination of wallshearstress,fluidexchange and turbulencecon-
ditions can be usedto predictareas that are not properly cleanedin bothsimple
and complexflowsystems(Friisand Jensen,2002).The surfaceroughness is
difficultto implementin flowmodels, but the fact that the above-mentioned
results on surface roughness are not a significant factor in cleaning is
encouragingthe use of CFDsimulationsas toolsfor optimisingthe cleaning
procedure.In the CFDmodellingtool the flowphenomena, e.g. wall shearstress
and fluidexchange,are usedfor predicting the cleanabilityin the flowsystems.
The combination of surface topography, fluid dynamics and surface
microbiologyprovidesa goodbasisfor studyingand solvingissuesrelatingto
hygiene in closed systems.
30.6 Future trends
The resultsof the preliminary experimentsstudyinga simple casegaveeach
other goodsupportin the simplecase studyperformed. This has provided
evidencefor the hypothesisthat a combinationof knowledge in fluiddynamics
and microbiologyalso provides an excellent basisfor the hygienicdesign of
integratedtankand CIPcleaningsystems. The mainfocushas beenon the
experimentalpartsincea sound basicknowledge wasrequired in order to
establisha properCFDmodelthat can be usedto simulate this typeof process
system. The CFDmodel shouldbe extendedto coverdifferenttanks and spray
balls and validated with the use of modified microbial test methods.
Development of thesetest methodsis neededin the futurestudies.Chismand
Smith (2004)havepatented a methodfor refurbishingbeveragestoragetanks.
The interiorsurfaceof the beverage storagetankis sprayed witha fluidjet to
remove liningand surfacecontaminants.The interiorsurfaceof the beverage
storagetankis abrasive blasted and a beverage-safe coating material is applied
to the prepared interiorsurface of the beveragestoragetankpriorto reuse.A
future trendwill also be to use improved coating materials for the tanksurfaces
in order to facilitatethe cleaning procedures.
30.7 References
AGIUS G, BURKEENSandMYNATTJ(2004)Benefitsof usingchlorinedioxideas an
alternativeto hot-watersanitation,MastBrewAss AmerTechQuart, 41 , 42±44.
AUSTINJWandBERGERONG(1995)Developmentof bacterialbiofilmsin dairyprocessing
lines,J DairyRes, 62 , 509±519.
BIRUST(2003)Use of stainlesssteeltanksin the fruit juiceindustry,Fluessiges-Obst, 70 ,
658±660.
504 Handbookof hygiene controlin the foodindustry