Sap and Vacuum Dynamics - University of Vermontpmrc/SapVac.pdfDoes NOT greatly affect sap chemistry, sap sugar content, or wounding. Vacuum level ... Sap and Vacuum Dynamics Author:

DYNAMICS OF SAP AND VACUUM FLOW

Timothy D. Perkins, DirectorTimothy D. Perkins, DirectorUniversity of Vermont

Proctor Maple Research CenterCopyright Timothy Perkins, UVM Proctor Maple Res Ctr, May 2010

30Effects of Vacuum

r2 = 0.969

20

25

Seas

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ted)

15

on in

200

4 S

amet

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Microspout

5

10

p Pr

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lons

-di

a

0

5

0 3 6 9 12 15 18 21 24

Sap (ga

0 3 6 9 12 15 18 21 24Vacuum Level (inches Hg)

Vacuum increases sap yield. 50‐200% increase in sap yield using vacuum. Strong linear relationship between vacuum level and sap yield (more vacuumrelationship between vacuum level and sap yield (more vacuum = more sap). Does NOT greatly affect sap chemistry, sap sugar content, or wounding.

Vacuum level? The higher the better! Detection and repair of leaks is critical.Copyright Timothy Perkins, UVM Proctor

Maple Res Ctr, May 2010

Fewer taps on a lateral line results in higher production. Vacuum is not propagated well through liquid When lines are full of liquid vacuum level at the tree is reduced resultingthrough liquid. When lines are full of liquid, vacuum level at the tree is reduced, resulting in lower production.

“Strive for five, no more than ten” OR Every extra 5 taps loses ~10% of sap yieldCopyright Timothy Perkins, UVM Proctor Maple Res Ctr, May 2010

University of VermontProctor Maple Research Center

Underhill Center, Vermont

Control ‐ 5 Taps/Lateral Martin Block(High Yield

Chamber Spout Base

One Tap/Lateral

(High Yield Study)

Mainline / No Laterals

SapShed

RedSeries

(Strategies Study)*

• Initial thinning• Treatment plots laid out(12 Plots, Total 775 taps

Main Bush

0 1,000 2,000500Feet

Avg 65 trees/plot, Avg 14.2” dbh)

• Mainline/tubing installed• Sap shed expanded

PMRC Lab

Main Bush(Tubing

ComparisonStudy)*

*Sugarhouse

Funded By: NAMSC & USDA GrantsProperty BoundaryTapping Boundary

Sap shed expanded• Vacuum pump installed• Custom releasers Copyright Timothy Perkins, UVM Proctor


Treatment 1 Treatment 2

High Sap YieldsTreatment 1.

Control – Standard Layout3/4” Mainline

5/16” Lateral Line3’ long, 5/16” Droplines, 3‐5 taps per lateral

Treatment 2. Chamber Spout Base

3/4” Mainline5/16” Lateral Line

3’ long, 5/16” Droplines, modified chamber spout base

Treatment 3. Treatment 4. One Tap per Lateral

3/4” Mainline5/16” Lateral Line

3’ long, 5/16” Droplines, 1 tap per lateral

No Lateral Lines3/4” Mainline

3’ long, 5/16” Droplines, 1 tap per lateral

Copyright Timothy Perkins, UVM Proctor Maple Res Ctr, May 2010

All single‐pipe systems

Very long mainlines

Average of 65 trees/plotAverage of 65 trees/plot

25‐26” Hg

Tapped at the same time

Standard Leader Spouts& Stubbys (NOT CV)




31.5 32.130.7

35

29.1

25

30

20

gal/tap)

15

Sap Yield (g

10

0

5

5 Taps Per Lateral 1 Tap Per Lateral Mainline Only Chamber Spout Base

TreatmentCopyright Timothy Perkins, UVM Proctor Maple Res Ctr, May 2010

Mainline Systems have been Optimized

Both single‐pipe and dual‐pipe systems, if sized and installedproperly are able to transfer vacuum to the far reaches of themainline system. Research and practical experience have resultedin systems that function very well. Little more can be done here.Copyright Timothy Perkins, UVM Proctor


Why No Differences in Sap Yield?

Chamber Spout Base results are likely NOT representative due to large number of leaks from both the spout/tree andfrom both the spout/tree andspout/spout base interface.

We will repeat this study in 2011 using an improved Chamber Spout Base design orp p g(more likely) something else.

1. Vacuum is being equally well transferred through all the mainline systems.

2. Sap flow in 2010 was low‐moderate for most of the season and never truly “challenged” any of the systems.

3 Mainline is NOT the major restriction in3. Mainline is NOT the major restriction in tubing systems. Something else is.

4. Other?

So is the system we have nowSo is the system we have now the best possible?


What about Lateral Lines and Drop Lines ?Plastic tubing was originallyPlastic tubing was originallyadapted from medical andindustrial tubing sourcesand tended to be ¼” insidediameter.

Fittings were necessarilysized to fit the tubing.

l b h d h ll hEarly on, most tubing was on gravity. When run downhill, having anumber of taps on small diameter tubing served to develop“natural vacuum”, which increased sap yields.

In current systems, vacuum pumps replace “natural vacuum”,however this creates a problem of having to transfer gases (fromthe tree and from leaks) through the tubing system along with sapthe tree and from leaks) through the tubing system along with sap.

Vacuum is not propagated well through liquid.Copyright Timothy Perkins, UVM Proctor Maple Res Ctr, May 2010

Factors that Restrict the Flow of Sap and Vacuum in Current Tubing Systemsp g y

Major Losses

• Type of fluid (capillarity)

Δh = λ (l / dh) (v2 / g 2)

yp ( p y)

• Flow rate (number of taps on a lateral line)

• Pipe length (length of laterals and drops)

• Pipe roughness (dirt/debris/biofilms)

• Pipe diameter

Minor Losses

• Tubing fittings (restrictions, number of fittings on lateral line changes in direction/bendson lateral line, changes in direction/bends,merging of sap streams at tees)

• Turbulence

• Gas from tree (gas moves faster than liquid)

• Change in flow direction (backflow)Copyright Timothy Perkins, UVM Proctor Maple Res Ctr, May 2010

1 8

2.0100' 5/16” Lateral line10 taps

Fitting ID Tubing ID

0.2"

1.4

1.6

1.8Mod‐High Flow Rate

1.4” Hg

1/4 "

1.0

1.2

ad Loss (ft)

0.9” Hg

1/4 "

5/16"0.4

0.6

0.8

Hea

5/16"

3/8 "7/16" 1/2 " 5/8 "

0.0

0.2

0.4

A loss of pressure that results from friction sustained by a fluid passing through a line

0.15 0.25 0.35 0.45 0.55 0.65

Tubing Diameter (inches)Δh = λ (l / dh) (v2 / g 2)

A loss of pressure that results from friction sustained by a fluid passing through a line, valve, fitting, or other device. Head loss that occurs in pipes is dependent on the flow velocity, pipe length and diameter, and a friction factor based on the roughness of the pipe and the Reynolds number of the flow.Copyright Timothy Perkins, UVM Proctor


1.8

2.010 tapsMod‐High Flow Rate

1.4

1.6

1.0

1.2

ad Loss (ft)

0.9” Hg

0 4

0.6

0.8He

0.0

0.2

0.4

1/2” line + fittings


50 100 150 200 250 300

Lateral Line Length (ft)Δh = λ (l / dh) (v2 / g 2)



1.8

2.0100 ftMod‐High Flow Rate

1.4

1.6

g

1.0

1.2

ad Loss (ft)

0.9” Hg

0.4

0.6

0.8He

0.0

0.21/2” line + fittings


0 2 4 6 8 10 12 14 16 18 20

Number of Taps per Lateral LineΔh = λ (l / dh) (v2 / g 2)



12 0

14.0

10 50

12.25

Mathematical Modeling of

10.0

12.0 Peak Flow(many taps, long lines)

8.75

10.50Pressure Loss in Lateral Lines

6.0

8.0

ad Loss (ft)

Moderate Flow5.25

7.00

Pressure Los

4.0

Hea

Slow Flow(few taps, short lines)

1 75

3.50

ss (“ Hg)

0.0

2.0

0 00 0 05 0 10 0 15 0 20 0 25 0 30 0 35 0 40

1/2” line + fittings

1.75

0.00


0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

Sap Flow Rate (gal/hr)Δh = λ (l / dh) (v2 / g 2)



Fewer taps on a lateral line results in higher production. Vacuum is not propagated well through liquid When lines are full of liquid vacuum level at the treethrough liquid. When lines are full of liquid, vacuum level at the treeis reduced, resulting in lower production.

“Strive for five, no more than ten” OR Every extra 5 taps loses ~10% of sap yieldCopyright Timothy Perkins, UVM Proctor Maple Res Ctr, May 2010

Measurement of Sap Flow Under Vacuum

Two trees (25” and 11” or 16” dbh)

5/16” spout and tubing

Connected to vacuum chamber

22” Hg

Each line runs through an individualEach line runs through an individual tipping bucket rain gage

Bucket tips are 7.6 ml (0.002 gal)

Time of each tip recorded with datalogger.


TippingBucketBucket RainGageInsideInsideVacuumCh bChamber







Vacuum MeasurementsRecording Gages Error limits + 0 1% FS (0 09” Hg)Error limits + 0.1% FS (0.09 Hg)Measured at 1 sec intervals6 locations in dual‐pipeline systemPump (before moisture trap)• Releaser (upper stage)• Mainline (25’ after manifold)• Mainline end (~300’ from manifold)• Dropline (4th tap – normal spout• Dropline (4 tap – normal spout• Dropline (4th tap – CV Adapter)




Sap in lines

PumpTurned On

Naturalvacuum

Vacuum level at the taphole Vacuum in dual‐line system pslowly decreases during sap run

Vacuum in dual line systemclosely tracks pump



Approaches to Reducing Losses Due to Lateral/Drop Line Restrictions

Oversized Lateral LinesChamber Spout Base(Modified Stubby)

Dual Lateral & Drop Lines

Due to Lateral/Drop Line Restrictions

Spring 2010Spring 2010Fall 2008Spring 2009, Spring 2010 Copyright Timothy Perkins, UVM Proctor


Dual‐LineDual‐Line Spout Video


30

2009 ‐ Single versus Dual‐Lateral/Dropline

25

18.9%

20

ons/tap)

15

p Yield (gallo

10Sap

5Single

Dual

0

2/26 3/5 3/12 3/19 3/26 4/2 4/9 4/16Copyright Timothy Perkins, UVM Proctor


Chamber Spout BaseChamber Spout Base

½” PVC Fittings

Bushing to mate to a Clear‐Straight‐Throughg g(CST) Spout

5/16” Drop & Lateral5/16 Drop & LateralLine



45

2010 ‐ Over‐Sized Lateral Lines & Fittingsi h difi d S B

35

40 with modified Spout Base

18.4%

25

30

/tap

)

20

25

ap Yield (gal

10

15

Sa

55/16" line

1/2" line

0

2/24 3/3 3/10 3/17 3/24 3/31 4/7Copyright Timothy Perkins, UVM Proctor


SummaryCalculations indicate that we are frequently losing up to 2‐4” Hg of vacuum due to lateral and d li (di t l th fitti t ) tdroplines (diameter, length, fittings, etc.) at moderate‐high flow rates, and transiently losing up to 10” Hg at peak flow rates.p g p

This represents a 10‐20+% loss in potential sap yield during good runs, and up to 50% loss during y g g , p % gbrief peak flow periods.

Does this loss actually occur in the field?Does this loss actually occur in the field?

Is this an acceptable loss?

Can we do something about it?Copyright Timothy Perkins, UVM Proctor



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Sap and Vacuum Dynamics - University of Vermontpmrc/SapVac.pdfDoes NOT greatly affect sap chemistry, sap sugar content, or wounding. Vacuum level ... Sap and Vacuum Dynamics Author: