Distributed airlift systems design with application to recirculating soft shell crawfish shedding systems

94 Pages·2017·1.19 MB·English

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LSU Master's Theses Graduate School
2005
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Sripavani Gudipati
Louisiana State University and Agricultural and Mechanical College
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Gudipati, Sripavani, "Distributed airlift systems design with application to recirculating soft shell crawfish
shedding systems" (2005). LSU Master's Theses. 2942.
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DISTRIBUTED AIRLIFT SYSTEMS DESIGN WITH APPLICATION TO
RECIRCULATING SOFT SHELL CRAWFISH SHEDDING SYSTEMS

A Thesis

Submitted to the Graduate Faculty of the
Louisiana State University and
Agricultural and Mechanical College
in partial fulfillment of the
requirements for the degree of
Master of Science in Civil Engineering
in
The Department of Civil and Environmental Engineering

by
Sripavani Gudipati
B.E. Civil Engineering
Osmania University, 2001
August, 2005
Dedicated to the Lord.

“May Thou inspire and guide our intellect in the right direction”

~ The Rig Veda (10:16:3)

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ACKNOWLEDGEMENTS

My masters’ at LSU has been an exciting learning experience in my development as an
individual academically and personally. Firstly I would like to thank my major professor Dr.
Malone for giving me an opportunity to work with him. The past one year has been enlightening
and motivating. I thank him for his support and trust in me; without his guidance this work
would not have been possible.
I appreciate my committee members Dr. Hall and Dr. Deng for their guidance and
feedback in helping me finish my thesis. I am thankful to Mr. Ty Dick for experimenting with
new technology in building the Lazy Cajun Soft Shell Crawfish Shedding Systems. I thank my
peers Brian, Steven and Terry in helping me build the experimental apparatus and also
discussing and reviewing my research work. I thank Dr. Cristina for reviewing the thesis and
discussing the technicalities. I appreciate my friends Abhilash, Sunil and Waleed who helped me
with my experiment.
I thank Dr. Kim MacGregor at Department of Education Leadership Research and
Counseling, LSU for funding me as a Graduate assistant all through my masters’. I thank my
family and friends for their love, encouragement and support. Finally I express my gratitude to
everyone who has directly or indirectly helped me through my master’s at LSU.

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TABLE OF CONTENTS

ACKNOWLEDGEMENTS...........................................................................................iii

LIST OF TABLES....................................................................................................... vi

LIST OF FIGURES.....................................................................................................vii

ABSTRACT................................................................................................................ ix

CHAPTER 1: INTRODUCTION......................................................................................1

CHAPTER 2: BACKGROUND.......................................................................................4
2.1 Eyestalk Ablation..................................................................................................................4
2.2 Hydraulic Separation............................................................................................................5
2.3 Airlift Technology................................................................................................................7

CHAPTER 3: EXPERIMENTAL METHODOLOGY..........................................................8
3.1 Experimental Apparatus........................................................................................................9
3.2 Weir Calibration..................................................................................................................13
3.3 Experimental Protocol........................................................................................................15
3.4 Data Analysis......................................................................................................................16
3.4.1 Gas Flow Rate Correction............................................................................................16
3.4.2 Calculation of Power Utilized for Running the Airlift Pump......................................17

CHAPTER 4: DISTRIBUTED AIRLIFT SYSTEM DESIGN FOR RECIRCULATING SOFT
SHELL CRAWFISH PRODUCTION SYSTEMS.............................................................18
4.1 Introduction.........................................................................................................................18
4.2 Background - Airlifts..........................................................................................................20
4.3 System Description.............................................................................................................22
4.4 System Design Rationale....................................................................................................25
4.4.1 Hydraulics and Friction Loss in Loops........................................................................25
4.4.2 Air Lift Riser Design...................................................................................................26
4.4.3 Distribution Pipe Design Rationale.............................................................................28
4.4.4 Air Requirement...........................................................................................................32
4.5 Discussion...........................................................................................................................32
4.5.1 Airlifts..........................................................................................................................32
4.5.2 Distribution Pipe..........................................................................................................33
4.6 Recommendations...............................................................................................................35

CHAPTER 5: CLOSURE STATEMENT.........................................................................38
5.1 Conclusions.........................................................................................................................38
5.3 Recent Airlift Applications.................................................................................................39
5.2 Future Work........................................................................................................................41

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REFERENCES............................................................................................................42

APPENDIX A: WEIR CALIBRATION DATA SHEETS...................................................46

APPENDIX B: EXPERIMENTAL RESULTS 2″ PVC PIPE..............................................51

APPENDIX C: EXPERIMENTAL RESULTS 3″ PVC PIPE..............................................63

APPENDIX D: DISTRIBUTION PIPE CALCULATIONS................................................75

VITA..........................................................................................................................84
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LIST OF TABLES

Table 3.1. Lift heights and submergence to be tested for a 2″ and 3″ diameter PVC schedule 40
pipe at varying air injection rates................................................................................16

Table 4.1.Components of a soft shell shedding system and head loss due to each.....................24

Table 4.2. Hydraulic system design recommendations for automated soft shell crawfish shedding
operations....................................................................................................................36

Table 4.3. Specific recommendations for distribution pipe design in RSC systems....................37

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LIST OF FIGURES

Figure 1.1.Steps involved in soft shell crawfish production............................................................1

Figure 2.1.Illustration of electrical shock gate in an acclimation tray.............................................6

Figure 3.1.Typical airlift showing basic parameters measured for experimental studies – water
flow rate, air flow rate, lift and submergence................................................................8

Figure 3.2.Air supply manifold and its components........................................................................9

Figure 3.3.Weir box placed on the top of the tank with weir plate, air injection line...................10

Figure 3.4.Bottom of the air injection pipe with end capped and holes for air injection..............11

Figure 3.5.Details of placing the airlift pipe in the tank, the T-fitting rests on bottom of the tank.
The position of tank pitot and pipe pitot are also indicated.........................................12

Figure 3.6.Position of weir pitot on the box, and tank, pipe pitot tubes outside the tank..............13

Figure 3.7.Curve fitting of actual flow over the weir and theoretical values to obtain a weir
equation using least sum of squares method................................................................15

Figure 4.1.Air lift pump illustrating the difference between static and dynamic lift and
submergence. The type of air injection method used is shown...................................21

Figure 4.2.Layout of a soft shell shedding system with 8 trays oriented longitudinally in each
row, filter, sumps and reservoir...................................................................................22

Figure 4.3.Component of the tray loop, with 2 trays showing the distribution pipe and airlift
connections..................................................................................................................23

Figure 4.4.Head loss at components in the tray loop as described in Table 4.1............................25

Figure 4.5.Water flow vs. gas flow rates for a 3″ pipe at 12″ lift for 20, 25 and 33 % Lift..........27

Figure 4.6.Water flow vs. gas flow rate for a 2″ pipe at 12″ lift for 20, 25 % Lift........................28

Figure 4.7.Plot of flow velocity and head loss in straight pipes of varying diameter (Timmons et
al, 2001).......................................................................................................................29

Figure 4.8.Comparison of dynamic submergence and velocity along a set of six trays when
using a uniform and tapered pipe.................................................................................30

Figure 4.9.Illustration for selection of a tapered distribution pipe for a set of 10 trays, water flow
rate, head loss and varying lift percent at each tray is shown......................................31
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Figure 4.10.Problem associated with trenching to meet submergence depth during construction
of a commercial facility...............................................................................................34

Figure 5.1.Hubbs Sea World –San Diego......................................................................................39

Figure 5.2.Mote Marine Sarasota Florida......................................................................................40

Figure 5.3. Lazy Cajun Soft Crawfish Facility – Baton Rouge.....................................................41

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ABSTRACT

Soft shell crawfish, a seafood delicacy, has a potential market for growth in the
aquaculture industry. Since the industry’s collapse in the 1990’s, the advent of new technologies
like eyestalk ablation, automated hydraulic separation and distributed airlift systems has elevated
the hope for restoration. In a distributed airlift system, airlifts and distribution pipes supply water
to holding trays. Airlifts are simple devices used to pump water by injecting air at the bottom of
an open pipe. The combination of airlifts and distribution pipes has potential economic benefits
for low head applications in recirculating aquaculture systems. This thesis focuses on guidelines
for the design of individual airlifts highlighting the rules for deciding the sizing of the riser, gas
to liquid ratio (G/L ratio) and the lift. It also explains the guidelines to be used for sizing of the
tapered water distribution pipes in distributed airlift systems.
Airlift diameter selection was based on a water flow rate of 15 gpm to each tray.
Experiments conducted on 2″ and 3″ pipes indicated that the 2″ pipe supplies 15 gpm at an
optimum G/L between 1 and 2 while using lesser air than a 3″ pipe for a lift height of 12″. The
airlifts should be designed for 20% lift and with no airlift exceeding 25% lift. They should be
operated with a G/L ratio between 1 and 2 to achieve an optimum rate of water flow and
minimum energy consumption.
Distribution pipes should be designed to minimize head loss and prevent settling. The
sizing of the water distribution pipes should be velocity based with a velocity in the distribution
system between 1 and 3 fps. Tapering of a distribution pipe is necessary to maintain the
minimum velocity. This also reduces head loss along the length of the pipe. Table 4.9 in this
thesis gives tapering requirements for soft shell crawfish systems with 5, 10, 15 and 20 trays in
each row.
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