- Email: [email protected]
Heat transfer from a bank of immersed horizontal smooth tubes in a fluidized bed
IN H E A T A N D M ~ S S T R A N S F ~ Vol. 6, pp. 225-229, 1979 ~)Pe~Press
0094-4548/79/0501-0225502.00/0 Ltd. Printed i n G r e a t B r i t a i n
HEAT TRANSFER FROM A BANK OF IMMERSED HORIZONTAL SMOOTH TUBES IN A FLUIDIZED BED
S.C. Saxena Department of Energy Engineering University of Illinois at Chicago Circle Box 4348, Chicago, Illinois 60680
(C~cated
by J.P. Hartnett and W.J. Minkowycz)
The purpose of this note is to report the preliminary results of eleven experiments performed in a fluidized bed of silica sand of two different mean particle diameters and dealing with heat transfer from immersed smooth horizontal tube bundles of different sizes and geometrical configurations.
The fluid
ized bed facility is described in a recent paper by Saxena, ChatterJee and Patel [I].
The bed cross-section is 30.5 cm by 30.5 cm and the distributor
consists of two perforated steel plates with a coarse cloth sandwiched between them.
One cm diameter holes are drilled in both the plates at a triangular
pitch of 14 cm, the open area being 37.5%.
The design of the side plates, a-
long with appropriate dimensions, which are used for mounting the heat transfer tubes is shown in Fig. I.
The silica sand of two different sizes and particle
size distributions is used as bed material. 167 ~m and 504 ~m, Grewal and Saxena [2].
The mean particle diameters are The heat transfer tubes are of
copper with 12.7 mm outside diameter, and are mounted horizontally.
The tubes
are electrically heated by a calrod heater 9.4 mm in diameter and 30.5 cm long. Three iron-constantan thermocouples are bonded to the tube surface in milled grooves with technical quality copper cement for temperature measurement and
225
226
S.C. S a ~ m ~
Vol. 6, No. 3
all such details are given by Grewal and Saxena [2,3].
These publications
report the procedure that hasbeen adopted for the measurements
50.8
o
o
o
@
o
a ?
and thence for
;
,% D IS
-25.4 aJa
a
a
a
o
I
Q, O,.,C
HOLE(S2)
22.2 DIA THRU HOLE/ (SO) FOR MOUNTING
o bY( )0,.,
12.7 041A TUBE
00000 (
25 I)iA HOLE F O R - ~ - ~ REMOVAL OF BED ~' MATERIAL
~7
oOo°
. -
L7
D
178 356
i_
"~
'r
[email protected]
O0(D 0O(9~ D 0o( ) O- q ~v-
o5,o5,9,
also
° ° °
o
~
",f . . . . . . .
~ - - - HOLEFORMOUNTINGI~ESSURE
FIG. i Details of the Plexiglass Side Plate for Mounting the ~eat Transfer Tube Bundle. All Dimensions are i n ~
the calculation of the total heat transfer coefficient, The results of the total heat transfer coefficient
h . w for a single tube and
tube bundles of three and five rows immersed in a fluidized bed of 167 ~m silica sand particles are displayed in Fig. 2 as a function of reduced mass fluidizing velocity, G/Gmf.
G is the superficial mass fluldizing velocity and Gmf is the
minimum superficial mass fluidizing velocity. these experiments locations
is about 36 cm.
in the bed.
The slumped bed height in all
The bed temperature
is measured at three
The bottom row of tubes in the other four sets of data
of Fig. 2 is located at a distance of 10.2 cm above the distributor plate.
The
vertical and horizontal pitches in the inline tube arrangement are 4 DT, where D T is the outside diameter of the copper tube. ments these are 2 D T and 4 D T respectively.
In the staggered tube arrange-
The maximum error associated with
Vol. 6, No. 3
our h
S~KXYII-I~'JBF_.S IN A FLUIDIZEDB]~D
227
values is estimated as + 8%, however, the reproducibility is about + 2%. W
--
--
While doing experiments with tube bundles only three heated tubes have been used for h
w
measurement.
It follows from the results given in Fig. 2 that the heat
transfer coefficient from a single tube to the fluidized bed is not influenced by adding two or four more rows as long as the horizontal pitch ~ 4D T and vertical pitch ~ 2D T for staggered tube bundles, and the pitches are ~ 4 D T for inllne tube bundles. The similar results of Fig. 3.
h
for larger
w
sand particles are displayed in
Conclusions derived from Fig. 2 are also valid for the results given
in Fig. 3.
It is to be noted that the single tube heat transfer characteristics
in relation to their performance in certain types of tube bundles are retained even when the average particle diameter is increased by about
three fold.
Further experiments are in progress with tubes arranged in different orientations in a bundle,
tube pitch varied over a wider range than employed here,
'
' 20/~
• SINGLE TUBE =THREE ROWS (INLINE) 500 - - T H R E E ROWS (STAGGERED) 04
E
450
-
Rz
2 .oo -/~," z2% oFIVE ROWS (INLINE)350
I
2
4
•F,yERgws ISTAGaEREO I 6
8
10
12
14
16
G/Gmf FIG. 2 Variation of Total Heat Transfer Coefficient (hw) With Reduced Mass Fluidizing Velocity (G/Gmf) for an Immersed Single Tube and Tube Bundles in a Fluidized Bed of Silica Sand of Average Particle Diameter 167 ~m
228
Vol. 6, NO. 3
S.C. Sa~ena
particles of different sizes and properties, and tubes of different surface roughness in fluldlzed beds of different sizes.
These results, their com-
parison with the available data, and correlations for the prediction of h W
for fluidlzed bed boilers will be reported at a later date. This research is supported in part by the United States National Science Foundation in a collaborative U.S.A.-U.S.S.R. research program under grant No.
ENG 77-08780A01.
The author is grateful to S.S. Kumbhat and N.S. Grewal for
their help in the work presented here.
320.
%
, , , • SINGLE TUBE ,-.=nnL.. =THREE ROWS
/
I •
I ,,
I .
"~ ~ I ./. -THREE R O W S '- 2601"- (. _-'_'::"~TAGGERED~ 2401/" I=FIVE ROWS(STAGG, ERED) <2
~..
~.6
~.8
2.0
2.2
2.4
GIGmf FIG. 3 Variation of Total Heat Transfer Coefficient With Reduced Mass Fluldlzlng Velocity for a Single Tube and Tube Bundles in a Fluldlzed Bed of Sillca Sand of Average Partlcle Diameter 504 ~m
Vol. 6, No. 3
SMDCTH ~
IN A FI//IDIZED BED
229
References I.
S.C. Saxena, A. ChatterJee and R.C. Patel, Powder Technol., 22 (1979) 191.
2.
N.S. Grewal and S.C. Saxena, Paper No. 57b, presented at the 86th AIChE National meeting held at Houston, Texas, during April 1-5, 1979.
3.
N.S. Grewal and S.C.Saxena, 4th Natl. Heat Mass Transfer Conf., India, (1977) 53.
0094-4548/79/0501-0225502.00/0 Ltd. Printed i n G r e a t B r i t a i n
HEAT TRANSFER FROM A BANK OF IMMERSED HORIZONTAL SMOOTH TUBES IN A FLUIDIZED BED
S.C. Saxena Department of Energy Engineering University of Illinois at Chicago Circle Box 4348, Chicago, Illinois 60680
(C~cated
by J.P. Hartnett and W.J. Minkowycz)
The purpose of this note is to report the preliminary results of eleven experiments performed in a fluidized bed of silica sand of two different mean particle diameters and dealing with heat transfer from immersed smooth horizontal tube bundles of different sizes and geometrical configurations.
The fluid
ized bed facility is described in a recent paper by Saxena, ChatterJee and Patel [I].
The bed cross-section is 30.5 cm by 30.5 cm and the distributor
consists of two perforated steel plates with a coarse cloth sandwiched between them.
One cm diameter holes are drilled in both the plates at a triangular
pitch of 14 cm, the open area being 37.5%.
The design of the side plates, a-
long with appropriate dimensions, which are used for mounting the heat transfer tubes is shown in Fig. I.
The silica sand of two different sizes and particle
size distributions is used as bed material. 167 ~m and 504 ~m, Grewal and Saxena [2].
The mean particle diameters are The heat transfer tubes are of
copper with 12.7 mm outside diameter, and are mounted horizontally.
The tubes
are electrically heated by a calrod heater 9.4 mm in diameter and 30.5 cm long. Three iron-constantan thermocouples are bonded to the tube surface in milled grooves with technical quality copper cement for temperature measurement and
225
226
S.C. S a ~ m ~
Vol. 6, No. 3
all such details are given by Grewal and Saxena [2,3].
These publications
report the procedure that hasbeen adopted for the measurements
50.8
o
o
o
@
o
a ?
and thence for
;
,% D IS
-25.4 aJa
a
a
a
o
I
Q, O,.,C
HOLE(S2)
22.2 DIA THRU HOLE/ (SO) FOR MOUNTING
o bY( )0,.,
12.7 041A TUBE
00000 (
25 I)iA HOLE F O R - ~ - ~ REMOVAL OF BED ~' MATERIAL
~7
oOo°
. -
L7
D
178 356
i_
"~
'r
[email protected]
O0(D 0O(9~ D 0o( ) O- q ~v-
o5,o5,9,
also
° ° °
o
~
",f . . . . . . .
~ - - - HOLEFORMOUNTINGI~ESSURE
FIG. i Details of the Plexiglass Side Plate for Mounting the ~eat Transfer Tube Bundle. All Dimensions are i n ~
the calculation of the total heat transfer coefficient, The results of the total heat transfer coefficient
h . w for a single tube and
tube bundles of three and five rows immersed in a fluidized bed of 167 ~m silica sand particles are displayed in Fig. 2 as a function of reduced mass fluidizing velocity, G/Gmf.
G is the superficial mass fluldizing velocity and Gmf is the
minimum superficial mass fluidizing velocity. these experiments locations
is about 36 cm.
in the bed.
The slumped bed height in all
The bed temperature
is measured at three
The bottom row of tubes in the other four sets of data
of Fig. 2 is located at a distance of 10.2 cm above the distributor plate.
The
vertical and horizontal pitches in the inline tube arrangement are 4 DT, where D T is the outside diameter of the copper tube. ments these are 2 D T and 4 D T respectively.
In the staggered tube arrange-
The maximum error associated with
Vol. 6, No. 3
our h
S~KXYII-I~'JBF_.S IN A FLUIDIZEDB]~D
227
values is estimated as + 8%, however, the reproducibility is about + 2%. W
--
--
While doing experiments with tube bundles only three heated tubes have been used for h
w
measurement.
It follows from the results given in Fig. 2 that the heat
transfer coefficient from a single tube to the fluidized bed is not influenced by adding two or four more rows as long as the horizontal pitch ~ 4D T and vertical pitch ~ 2D T for staggered tube bundles, and the pitches are ~ 4 D T for inllne tube bundles. The similar results of Fig. 3.
h
for larger
w
sand particles are displayed in
Conclusions derived from Fig. 2 are also valid for the results given
in Fig. 3.
It is to be noted that the single tube heat transfer characteristics
in relation to their performance in certain types of tube bundles are retained even when the average particle diameter is increased by about
three fold.
Further experiments are in progress with tubes arranged in different orientations in a bundle,
tube pitch varied over a wider range than employed here,
'
' 20/~
• SINGLE TUBE =THREE ROWS (INLINE) 500 - - T H R E E ROWS (STAGGERED) 04
E
450
-
Rz
2 .oo -/~," z2% oFIVE ROWS (INLINE)350
I
2
4
•F,yERgws ISTAGaEREO I 6
8
10
12
14
16
G/Gmf FIG. 2 Variation of Total Heat Transfer Coefficient (hw) With Reduced Mass Fluidizing Velocity (G/Gmf) for an Immersed Single Tube and Tube Bundles in a Fluidized Bed of Silica Sand of Average Particle Diameter 167 ~m
228
Vol. 6, NO. 3
S.C. Sa~ena
particles of different sizes and properties, and tubes of different surface roughness in fluldlzed beds of different sizes.
These results, their com-
parison with the available data, and correlations for the prediction of h W
for fluidlzed bed boilers will be reported at a later date. This research is supported in part by the United States National Science Foundation in a collaborative U.S.A.-U.S.S.R. research program under grant No.
ENG 77-08780A01.
The author is grateful to S.S. Kumbhat and N.S. Grewal for
their help in the work presented here.
320.
%
, , , • SINGLE TUBE ,-.=nnL.. =THREE ROWS
/
I •
I ,,
I .
"~ ~ I ./. -THREE R O W S '- 2601"- (. _-'_'::"~TAGGERED~ 2401/" I=FIVE ROWS(STAGG, ERED) <2
~..
~.6
~.8
2.0
2.2
2.4
GIGmf FIG. 3 Variation of Total Heat Transfer Coefficient With Reduced Mass Fluldlzlng Velocity for a Single Tube and Tube Bundles in a Fluldlzed Bed of Sillca Sand of Average Partlcle Diameter 504 ~m
Vol. 6, No. 3
SMDCTH ~
IN A FI//IDIZED BED
229
References I.
S.C. Saxena, A. ChatterJee and R.C. Patel, Powder Technol., 22 (1979) 191.
2.
N.S. Grewal and S.C. Saxena, Paper No. 57b, presented at the 86th AIChE National meeting held at Houston, Texas, during April 1-5, 1979.
3.
N.S. Grewal and S.C.Saxena, 4th Natl. Heat Mass Transfer Conf., India, (1977) 53.