Table Of ContentSolving Problems in Food Engineering
Stavros Yanniotis, Ph.D.
Author
Solving Problems in
Food Engineering
StavrosYanniotis,Ph.D.
DepartmentofFoodScienceandTechnology
AgriculturalUniversityofAthens
Athens,Greece
ISBN:978-0-387-73513-9 eISBN:978-0-387-73514-6
LibraryofCongressControlNumber:2007939831
#2008SpringerScience+BusinessMedia,LLC
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‘‘Tell me and I will listen,
Show me and I will understand
Involve me and I will learn’’
Ancient Chinese Proverb
Preface
Food engineering is usually a difficult discipline for food science students
because they are more used to qualitative rather than to quantitative descrip-
tionsoffoodprocessingoperations.Foodengineeringrequiresunderstanding
ofthebasicprinciplesoffluidflow,heattransfer,andmasstransferphenomena
andapplicationoftheseprinciplestounitoperationswhicharefrequentlyused
in food processing, e.g., evaporation, drying, thermal processing, cooling and
freezing, etc. The most difficult part of a course in food engineering is often
consideredthesolutionofproblems.Thisbookisintendedtobeastep-by-step
workbook that will help the students to practice solving food engineering
problems. It presumes that the students have already studied the theory of
eachsubjectfromtheirtextbook.
The book deals with problems in fluid flow, heat transfer, mass transfer,
andthemostcommonunitoperationsthatfindapplicationsinfoodprocessing,
i.e.,thermalprocessing,coolingandfreezing,evaporation,psychometrics,and
drying.Thebookincludes1)theoreticalquestionsintheform‘‘true’’or‘‘false’’
whichwillhelpthestudentsquicklyreviewthesubjectthatfollows(theanswers
to these questions are given in the Appendix); 2) solved problems; 3) semi-
solved problems; and 4) problems solved using a computer. With the semi-
solvedproblemsthestudentsareguidedthroughthesolution.Themainsteps
are given, but the students will have to fill in the blank points. With this
technique, food science students can practice on and solve relatively difficult
foodengineeringproblems.Someoftheproblemsareelementary,butproblems
of increasing difficulty follow, so that the book will be useful to food science
studentsandeventofoodengineeringstudents.
ACDissuppliedwiththebook which containssolutions ofproblemsthat
requiretheuseofacomputer,e.g.,transientheatandmasstransferproblems,
simulationofamultipleeffectevaporator,freezingofa2-Dsolid,drying,and
others.Theobjectivesforincludingsolvedcomputerproblemsare1)togivethe
studentstheopportunitytorunsuchprogramsandseetheeffectofoperating
and design variables on the process; and 2) to encourage the students to use
computers to solve food engineering problems. Since all the programs in this
CDareopencodeprograms,thestudentscanseealltheequationsandthe logic
behind the calculations. They are encouraged to see how the programs work
vii
viii Preface
and try to write their own programs for similar problems. Since food science
studentsfeelmorecomfortablewithspreadsheetprogramsthanwithprogram-
ming languages, which engineering students are more familiar with, all the
1
problemsthatneedacomputerhaveEXCEL spreadsheetsolutions.
I introduce the idea of a digital SWITCH to start and stop the programs
whentheproblemissolvedbyiteration.WiththedigitalSWITCH,wecanstop
andrestarteachprogramatwill.WhentheSWITCHisturnedofftheprogram
is not running, so that we can change the values of the input variables. Every
timewerestarttheprogrambyturningtheSWITCHon,allcalculationsstart
from the beginning. Thus it is easy to change the initial values of the input
variablesandstudytheeffectofprocessinganddesignparameters.Intheeffort
tomakethingsassimpleaspossible,someofthespreadsheetprogramsmaynot
operateonsomesetsofparameters.Insuchcases,itmaybenecessarytorestart
theprogramwithadifferentsetofparameters.
I am grateful to Dr H. Schwartzberg, who read the manuscripts and made
helpful suggestions. I will also be grateful to readers who may have useful
suggestions,orwhopointouterrorsoromissionswhichobviouslyhaveslipped
frommyattentionatthispoint.
Athens StavrosYanniotis
May2007
Contents
Preface .................................................... vii
1. ConversionofUnits ........................................ 1
Examples
Exercises
2. UseofSteamTables........................................ 5
ReviewQuestions
Examples
Exercises
3. MassBalance............................................. 11
ReviewQuestions
Examples
Exercises
4. EnergyBalance ........................................... 21
Theory
ReviewQuestions
Examples
Exercises
5. FluidFlow ............................................... 33
ReviewQuestions
Examples
Exercises
6. Pumps................................................... 41
Theory
ReviewQuestions
Examples
Exercises
ix
x Contents
7. HeatTransferByConduction............................... 55
Theory
ReviewQuestions
Examples
Exercises
8. HeatTransferByConvection............................... 67
Theory
ReviewQuestions
Examples
Exercises
9. HeatTransferByRadiation................................. 95
ReviewQuestions
Examples
Exercises
10. UnsteadyStateHeatTransfer .............................. 101
Theory
ReviewQuestions
Examples
Exercises
11. MassTransferByDiffusion ................................ 141
Theory
ReviewQuestions
Examples
Exercises
12. MassTransferByConvection .............................. 155
Theory
ReviewQuestions
Examples
Exercises
13. UnsteadyStateMassTransfer.............................. 163
Theory
ReviewQuestions
Examples
Exercises
14. PasteurizationandSterilization ............................. 181
ReviewQuestions
Examples
Exercises
Contents xi
15. CoolingandFreezing ..................................... 193
ReviewQuestions
Examples
Exercises
16. Evaporation ............................................ 215
ReviewQuestions
Examples
Exercises
17. Psychrometrics.......................................... 237
ReviewQuestions
Examples
Exercises
18. Drying ................................................ 253
ReviewQuestions
Examples
Exercises
References ................................................. 273
Appendix:AnswerstoReviewQuestions ......................... 275
Moodydiagram......................................... 280
Gurney-Luriecharts ..................................... 281
Heislercharts........................................... 284
Pressure-EnthalpychartforHFC134a....................... 285
Pressure-EnthalpychartforHFC404a....................... 286
Psychrometricchart...................................... 287
Besselfunctions ......................................... 288
Rootsofdtand=Bi...................................... 290
RootsofdJ1(d)-BiJo(d)=0................................ 291
Rootsofdcotd=1-Bi .................................... 292
Errorfunction .......................................... 293
Index...................................................... 295
