Comparison of High Efficiency Heat Exchanger Retrofits for the

Powell Star Bulk Barn

Stephen Barts and T. David ReedVirginia Tech

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Background• The Powell Star CB-9 barns is the most

predominant bulk curing barn in Virginia

– Very good curing characteristics

– Has a unique heat exchanger that was designed specifically for the barn

– Has a relatively high level of energy consumption(fuel and electricity) resulting in comparatively high curing costs

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Background• Original heat exchanger manufactured 15-20

years ago

• Little consideration give at that time to efficiency

• Aging heat exchangers now warrant replacement

• Greater emphasis should be given to efficiency of replacement units

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Objective

Evaluate new high efficiency heat exchanger retrofits for the Powell Star CB-9 curing barn

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Test Barns at Lazy C Farms 201

8_T

WC

71_B

arts

.pdf

TW

C20

18(4

8) -

Doc

umen

t not

pee

r-re

view

ed

Test Barns at Lazy C Farms

Heat exchangers evaluated

1. Original Powell Star unit (Powermatic burner)2. DeCloet SLR (existing Powermatic burner)3. Tytun (new Reillo burner)

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Tobacco Barn Heat Exchanger Testing Procedure

1. Burner setup – set output to 400K Btu and optimize efficiency (O2, CO, excess air, etc.)

2. Use a calibrate combustion gas analyzer to measure stack temperature and provide calculated combustion efficiency value

3. Record combustion efficiency after a set firing schedule

Presented at the 47th TWC (Reed)

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Testing Protocol

1. Initial 2 minute warm-up

2. 2 minute off cycle

3. Run three (3) burner cycles of 6 minutes on and 2 minutes off

4. Record combustion efficiency at end of third cycle as heat exchanger efficiency

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Length of burn (minutes)

2 2 4 6 2 4 6 2 4 6Ef

ficie

ncy

(%)

70

75

80

85

90

Tytun

Star

DeCloet

Length of burn (minutes)

2 2 4 6 2 4 6 2 4 6

Stac

k te

mpe

ratu

re (F

)

100

150

200

250

300

350

400

450

500

Tytun

Star

Decloet

Heat Exchanger Efficiency TestingLazy C Farms, 2017

Powell Star CB-9 barns

89.0%

76.2%

74.4%

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Length of burn (minutes)

2 2 4 6 2 4 6 2 4 6

Stac

k te

mpe

ratu

re (F

)

100

150

200

250

300

350

400

450

500

Length of burn (minutes)

2 2 4 6 2 4 6 2 4 6Ef

ficie

ncy

(%)

70

75

80

85

90

Heat Exchanger Efficiency TestingLazy C Farms, 2017

Original Star heat exchanger

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Length of burn (minutes)

2 2 4 6 2 4 6 2 4 6

Stac

k te

mpe

ratu

re (F

)

150

200

250

300

350

400

450

500

Length of burn (minutes)

2 2 4 6 2 4 6 2 4 6

Effic

ienc

y (%

)

70

75

80

85

90

Heat Exchanger Efficiency TestingLazy C Farms, 2017

DeCloet SLR

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Length of burn (minutes)

2 2 4 6 2 4 6 2 4 6

Stac

k te

mpe

ratu

re (F

)

100

150

200

250

300

350

400

450

Length of burn (minutes)

2 2 4 6 2 4 6 2 4 6Ef

ficie

ncy

(%)

70

75

80

85

90

Heat Exchanger Efficiency TestingLazy C Farms, 2017

Tytun

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

High Efficiency Condensing Heat Exchanger

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Air Flow Issues• Standard Powell Star CB-9 experiences airflow

issues related to the burner placement

– Heat exchanger is mounted low in relation to the fans

– Offset burner results in uneven heat distribution

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Front Box Pin TemperaturesLazy C Farms, 2017

Original Star barn – front box pin temperatures

Curing Time (hrs)12 24 36 48 60 72 84 96 108 120 132 144 156 168 180 192 204 216

Tem

pert

ure

(F)

70

80

90

100

110

120

130

140

150

160

170

Upper leftUpper rightLower leftLower right

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Front Box Pin TemperaturesLazy C Farms, 2017

DeCloet – front box pin temperatures

Curing Time (hrs)12 24 36 48 60 72 84 96 108 120 132 144 156 168 180 192 204 216

Tem

pert

ure

(F)

70

80

90

100

110

120

130

140

150

160

170

Upper leftUpper rightLower leftLower right

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Front Box Pin TemperaturesLazy C Farms, 2017

Tytun – front box pin temperatures

Curing Time (hrs)

12 24 36 48 60 72 84 96 108 120 132 144 156 168 180 192 204 216

Tem

pert

ure

(F)

70

80

90

100

110

120

130

140

150

160

170

Upper leftUpper rightLower leftLower right

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Curing Efficiency Results

Heat Exchanger Fuel consumption Curing efficiency

(Gal. per cure) (Lbs tobacco per gal.)

Original Star barn 517 a 7.1 b

DeCloet heat exchanger 450 a 7.9 b

Tytun retrofit 346 b 10.1 a

Averaged results of 6 cures

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Summary

• The DeCloet SLR heat exchanger increased curing efficiency by 11% and had a positive impact on air-flow

• The Tytun retrofit with a high efficiency heat exchanger and burner resulted in a 42% increase in curing efficiency

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Cost of Tobacco Curing

• Prices can fluctuate making budgeting difficult

• Bulk LPG and the use of natural gas addresses the cost of curing fuel

• Retrofitting barns with high efficiency heat exchanger addresses reducing fuel consumption

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C71

_Bar

ts.p

dfT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed