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NASA Technical Memorandum 85807
tNASA-TM-85807 19840017577 } _6"_3[ _""t-_F_"_'_'_'_._...-._..__-.--.....- ,,,
Reynolds Number Effects onPressure Loss and TurbulenceCharacteristics of Four
Tube-Bundle Heat Exchangers
William B. Igoe and Garl L. Gentry, Jr.
LiR RYCOPYJUNE 1984
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_A ,_'' N.\ -SAL!_,,, .,'_,
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https://ntrs.nasa.gov/search.jsp?R=19840017577 2018-05-25T02:34:35+00:00Z
NASA Technical Memorandum 85807
Reynolds Number Effects onPressure Loss and TurbulenceCharacteristics of Four
Tube-Bundle Heat Exchangers
William B. Igoe and Garl L. Gentry, Jr.
Langley Research Center
Hampton, Virginia
National Aeronautics
and Space Administration
Scientific and TechnicalInformation Branch
1984
SUMMARY
The aerodynamic characteristics of pressure loss and turbulence on four tube-bundle configurations representing heat-exchanger geometries with nominally the sameheat capacity were measured as a function of Reynolds number from about 4000 to400 000 based on tube hydraulic diameter. Two elliptical- and two round-tube
configurations were tested. All four configurations had plate fins.
The results indicate an apparent aerodynamic advantage of the elliptical-tubeshape compared with the round-tube shape both for pressure loss and turbulence char-acteristics. For all four configurations, the pressure loss coefficient decreasedwith increasing Reynolds number at low Reynolds numbers. At high Reynolds numbers,the same trend persisted for the elliptical-tube configurations but was reversed forthe round-tube configurations.
INTRODUCTION
The adoption of cryogenic operation has made it possible to obtain high Reynoldsnumber test conditions at transonic speeds in conventional closed-circuit, fan-driven, continuous-flow wind tunnels (as indicated, for example, in refs. I to 4).Cryogenic operation in nitrogen with liquid nitrogen injected directly into the cir-cuit for cooling in these tunnels has been shown to increase the maximum testReynolds number by about 5 to 7 times that available at ambient temperatures for thesame stagnation pressure and Mach number conditions (ref. I).
The overall consumption of energy in cryogenic tunnels is high, primarilybecause of the energy required to produce the liquid nitrogen which is used for cool-ing (ref. 2). If a conventional chilled-water heat exchanger was used for cooling inthe ambient temperature mode of operation instead of liquid nitrogen injection, ithas been estimated that the consumption of energy in this mode would be reduced by anorder of magnitude. In addition to the advantages in energy consumption, the bene-fits of using a conventional heat exchanger for cooling also include the capabilityto use air as well as nitrogen as the test gas in the ambient temperature mode.
The Reynolds number range over which a cryogenic wind tunnel operates in thecryogenic mode is generally well above that for which a heat exchanger would beneeded for cooling in the ambient temperature mode. The external, or aerodynamic,characteristics of the tube-bundle elements of the heat exchanger such as pressureloss and turbulence generation are functions of Reynolds number as well as other testvariables. These aerodynamic characteristics are important to the efficiency and tothe flow quality of the wind tunnel and must be determined for all operating condi-tions. Consequently, in the development of large cryogenic wind tunnels, it may benecessary to determine these characteristics at Reynolds numbers substantiallygreater than those for which the heat exchangers are designed for heat transferpurposes.
The National Transonic Facility (NTF) at the Langley Research Center is an exam-ple of the kind of wind tunnel under discussion here. It is a cryogenic, fan-driven,continuous-flow wind tunnel with a 2.5-m-square test section. In order to test atlow and moderate Reynolds numbers in air as well as in nitrogen, the NTF has a
conventional chilled-water heat exchanger in the tunnel circuit (ref. 5). The heatexchanger has a design heat capacity corresponding to about 0.3 MW/m2 of frontalarea.
In order to provide comparative data needed to guide the selection of the heat-exchanger geometry for the NTF, several candidate tube-bundle configurations, eachdesigned for nominally the same heat capacity, were tested for the aerodynamic char-acteristics of pressure loss and turbulence. None of the heat-transfer characteris-tics of the heat exchangers were simulated, and all tests were conducted under
adiabatic flow conditions. Some results of tests at low Reynolds number are reportedin reference 6.
The present tests were conducted in the 20- by 60-cm test section of the Langley0.3-Meter Transonic Cryogenic Tunnel (TCT) at Reynolds numbers from about 3.8 x 105to 2.8 x 107 per meter. The free-stream Mach number was varied from about 0.01
to 0.10, the stagnation pressure was varied from about 1.2 to 5.0 atm, and the stag-nation temperature was varied from about 100 to 300 K. The Reynolds number based ontube hydraulic diameter varied from approximately 4 × 103 to 4 × 105.
SYMBOLS
a speed of sound
length
M Mach number, U/a
q dynamic pressure, pU2/2
R Reynolds number, pU_/_
U free-stream velocity
u' root-mean-square (rms) turbulent-velocity component in streamwisedirection
x,y,z streamwise coordinate, lateral coordinate parallel to tube axis, andlateral coordinate normal to tube axis, respectively
APt stagnation pressure loss across heat-exchanger tube bundle
dynamic viscosity of test gas
p mass density of test gas
TEST APPARATUS
The current configuration of the 0.3-m TCT with a 20- by 60-cm test section
(fig. 1) is described in reference 7. It is a closed-circuit, fan-driven, pressur-ized tunnel capable of continuous operation. The test gas is nitrogen, and themethod of cooling is by injection of liquid nitrogen into the circuit. This methodof cooling, and the consequent exhausting of gaseous nitrogen to the atmosphere tomaintain a constant pressure, limits the minimum operating pressure of the tunnel to
2
about 1.2 atm. At the time of the tests, the maximum pressure limit on the pressure
shell was 5.0 atm, although since that time this limit has been raised to 6.0 atm
(ref. 7).
The temperature limits of the tunnel range from a low of 77 K (the liquefaction
temperature of nitrogen) to about 327 K. This wide range of temperatures permits a
wide range of Reynolds numbers to be obtained at low dynamic pressures.
The tube-bundle heat-exchanger models were installed in the 20- by 60-cm test
section of the tunnel with the tubes spanning the 20-cm dimension as shown in the
photograph of figure 2 and the sketch of figure 3. Normally, the test section is
ventilated with longitudinal slots in the top and bottom walls. The side walls are
usually solid except when provisions are made for boundary-layer removal. For the
present tests, the slotted walls were replaced with solid walls, and no test-sectionventilation was used.
MODELS
The cryogenic feature of the 0.3-m TCT allowed high Reynolds number test condi-
tions to be reached without imposing severe loading conditions on the test models.
The low dynamic pressures allowed a simplified method of construction for the models
of the various tube-bundle heat exchangers.
Since heat transfer was not included in the tests, it was not necessary to con-
struct the tube bundles of actual tube hardware. Consequently, for simplicity, all
the models were constructed with thin, flat brass sheets for the plate fins with
aluminum washers aligned between the fins to simulate the tubes. The fin spacing,
tube diameter, and round or elliptical tube shapes were provided by using washers of
appropriate size and shape. The tube bundles were held together by aluminum stud
bolts through the centers of the washers. All the materials used were compatible
with the cryogenic temperature environment to which they were exposed.
Geometrically, the models were made the same size as the tube bundles they were
intended to represent. Streamwise, the full depth of the tube bundle was simulated.
Laterally, the number of tubes represented was sufficient to fill the 60-cm dimension
of the test section. The length of the tubes spanned the 20-cm dimension of the test
section.
Four tube-bundle heat-exchanger models were tested. The configurations of the
models are shown in figure 4. All the configurations had in-line tube arrays with
plate fins. Two of the configurations (elliptical 1 and 2) had elliptically shaped
tubes, and the other two configurations (baseline and six-row) had round tubes. Both
of the elliptical-tube configurations and the baseline configuration had four rows of
tubes streamwise. The other round-tube configuration had six rows of tubes stream-
wise. The two configurations designated elliptical 1 and 2 differed only in the size
of the tubes.
It was intended that all the tube-bundle heat-exchanger models would represent
configurations with substantially the same heat capacity. After the dimensions of
the smaller elliptical tube were selected, it was discovered that, from a heat-
transfer consideration, this configuration would require a water circulation velocity
inside the tube that was higher than was considered desirable. The larger elliptical
tube allowed a lower water velocity. For completely comparable internal flow condi-tions (same water velocity), the smaller elliptical-tube configuration would there-fore have fallen somewhat short (about 75 percent) of the required heat capacity.
INSTRUMENTATION
The instrumentation for the present tests consisted primarily of the instrumen-tation normally in use at the 0.3-m TCT (refs. 4 and 7). I_ should be noted that thecapacities of the pressure transducers regularly used at the tunnel are sized for thefull range of pressures associated with high Mach number (near-sonic) operation athigh total pressures. Because of the low speeds of the present tests, in someinstances lower capacity, more sensitive pressure transducers were used.
The tunnel free-stream total pressure is normally measured in the settling cham-ber (downstream of the anti-turbulence screens) with a differential pressure gagereferenced to vacuum with a capacity of about 700 kPa. For the present tests, thetotal pressure was measured with a pitot probe located just upstream of the testsection with the same kind of pressure gage installation and capacity.
The free-stream static pressure is normally measured with sidewall static-pressure orifices located near the front of the test section with a pressure gageinstallation and capacity the same as those used for the total pressure. For thepresent tests, a more sensitive pressure gage with a capacity of about 3 kPa wasconnected to the same static-pressure orifices and referenced to free-stream totalpressure.
The pressure drop across the tube-bundle heat-exchanger models was obtained fromthe difference in total pressures measured upstream and downstream of the models.The upstream total pressure was obtained from the free-stream total-pressure pitottube, and the downstream total pressure was measured with a total-pressure rake.This rake, which is shown in figure 5, is normally used for surveying the wake behindairfoil models in the test section with differential pressure gages referenced tofree-stream total pressures; the capacity of these gages is about 140 kPa. For thepresent tests, the farthest outboard total-pressure tube on the rake was connected toa sensitive differential-pressure gage referenced to free-stream total pressure. Thecapacity of this gage is about 50 kPa.
For the heat-exchanger models installed in the 0.3-m TCT test section, the dis-tance from the rear face of the tube bundle to the total-pressure-rake tubes was
52.7 cm for the elliptical I and 2 configurations, 48.9 cm for the baseline config-uration, and 38.7 cm for the six-row configuration. These distances expressed interms of tube spacing are 13.8, 12.8, and 7.6, respectively. Although the surveyrake is normally capable of vertical (z-direction) translation, for this test therake was fixed at the tunnel centerline. Consequently, the pressure-tube readings onthe rake represented single-point measurements. A vertical survey yielding a spatialaverage would have been preferred, but this was not possible because of hardwarelimitations. However, flow uniformity measurements of reference 6 for similar tube-bundle configurations at low Reynolds numbers indicate that single-point measurements
of total pressure loss, expressed in terms of Apt/q, should not differ from a spa-tially averaged measurement by more than ±0.2.
The hot-wire probes consisted of crossed wires of 5-_m, platinum-coated tungstenwire with an effective length-diameter ratio of about 250. The hot wires were oper-ated in the constant temperature mode for turbulence measurements and in the constant
4
current mode for measurements of temperature spottiness. The output signals from the
hot-wire probes were recorded on magnetic tape for off-line analysis, and on-line rms
readings were also recorded. Only the rms turbulence data are presented in this
report. The tunnel stagnation temperature was measured in the settling chamber withthe standard tunnel instrumentation consisting of a platinum resistance thermometer.
RESULTS AND DISCUSSION
The pressure loss characteristics of the various tube-bundle configurations are
presented in the form of the difference in stagnation pressures ahead and behind the
models Ap t divided by the free-stream dynamic pressure q. The turbulence charac-teristics are presented as the rms turbulent-velocity components u', v', and w'
divided by the free-stream velocity U. For convenience, the Reynolds numbers are
given as unit Reynolds numbers of the flow rather than the Reynolds number based on
the hydraulic diameter of the tubes. This is done because the main intention of the
tests is to obtain comparative data on the performance of tube bundles of different
geometries under the same flow conditions.
Effect of Mach Number
During the tests, it was necessary to vary velocity as well as temperature and
pressure in order to obtain the wide range of Reynolds numbers desired. The small
change in Mach number caused by the change in velocity was not expected to have sig-
nificant effects on the aerodynamics of the various tube bundles.
In order to illustrate this anticipated insensitivity to small changes in Mach
number, the pressure loss data Apt/q as a function of y (the probe position onthe rake) are shown in figure 6 for each configuration at a nearly constant Reynolds
number over a range of Mach numbers from about 0.05 to 0.10. In fibre 6, theReynolds number for the elliptical 1 configuration is about 25 x 10 per meter; for
the other configurations it is about 13 x 106 per meter. Within the normal scatter
of the data, the pressure loss is uniform for the several probes over the span of the
rake.
The data from figure 6 for the farthest outboard probe of the rake have been
replotted as a function of Mach number in figure 7 to show that the pressure losscoefficients do not vary significantly with Mach number. From these results, it has
been concluded that varying Reynolds number by varying velocity in this low Mach
number range does not introduce any extraneous Mach number effects.
Effect of Reynolds Number
As mentioned earlier, the Reynolds numbers of the tests varied from about
3.8 x 105 to 2.8 x 107 per meter. This wide range was only possible by varying
velocity or Mach number as well as pressure and temperature. The Reynolds number
range at constant Mach number was somewhat more limited. Pressure loss data for a
nearly constant Mach number of about 0.05 are presented in figure 8 for the four
tube-bundle configurations. With minor exceptions for the baseline and six-row con-
figurations, once again the pressure loss is uniform over the span of the rake.
The data from figure 8 for the farthest outboard probe on the rake (y = 11.4 cm)
have been replotted as a function of unit Reynolds number for the four configurations
5
in figure 9. Data for higher and lower Mach numbers have been included to increasethe Reynolds number range.
Within the range of the tests, both the elliptical I and 2 configurations show acontinuing reduction of pressure loss coefficient with increasing Reynolds number.The two round-tube configurations show a reversal to a rising trend at the higherReynolds numbers, with the effect being more pronounced for the baseline configura-tion, which also had the lowest porosity (ratio of projected open area to total areaof tube bundle).
The magnitude of the pressure loss coefficient in figure 9 varies from the low-
est for the elliptical 1 configuration (which had the highest porosity) to the high-est for the baseline configuration (which had the lowest porosity). A comparison ofthe pressure loss characteristics of the elliptical 2 and six-row configurations,which had nearly the same porosities, shows an apparent aerodynamic advantage for theelliptically shaped tubes.
Turbulence Characteristics
The root-mean-square (rms) longitudinal components of turbulent velocity u'/Umeasured upstream and downstream of the tube-bundle heat-exchanger models are pre-sented in figure 10. The downstream turbulence varies from lowest to highest roughlyin the order elliptical I, elliptical 2, baseline, and six-row configurations. Thehigh value of turbulence measured for the six-row configuration may be at least par-tially due to the greater streamwise depth of this tube bundle. The turbulence-measuring station was a fixed distance (54.3 cm) downstream from the front face ofall the tube-bundle heat-exchanger models. Consequently, for a tube bundle with
greater streamwise depth, the distance from the last row of tubes to the measuringstation was less. The streamwise decay of turbulence increases with this distance.Since this distance was less for the six-row configuration than for the others, theturbulence for this configuration had less flow length over which decay could takeplace. Consequently, the higher level of turbulence indicated for this configurationmay not be wholly attributable to the characteristics of the tube bundle itself, butmay be at least partially due to less decay of the turbulence.
The distance from the rear face of the tube bundle to the hot wire was 39.1 cmfor the elliptical 1 and 2 configurations, 35.3 cm for the baseline configuration,and 25.1 cm for the six-row configuration. In terms of tube spacing, these distanceswere 10.3, 9.3, and 4.9, respectively. Based on turbulence decay data obtained atlow Reynolds numbers for similar tube-bundle configurations (ref. 6), it is estimatedthat the difference in decay distance (35.3 cm for the baseline configuration com-pared with 25.1 cm for the six-row configuration) could cause a difference of 20 per-cent more reduction for the configuration with the greater decay length. Since thestreamwise depths of the elliptical I and 2 configurations were more nearly equal tothe baseline configuration, their decay distances were also more nearly equal(39.1 cm compared with 35.3 cm), and so their turbulence levels may be compareddirectly.
CONCLUDING REMARKS
The aerodynamic characteristics of pressure loss and turbulence on four tube-bundle configurations representing heat-exchanger geometries with nominally the sameheat capacity were measured as a function of Reynolds number from about 4000 to
6
400 000 based on tube hydraulic diameter. Two elliptical- and two round-tube
configurations were tested. All four configurations had plate fins.
The results indicate an apparent aerodynamic advantage of the elliptical-tubeshape compared with the round-tube shape both for pressure loss and turbulence char-acteristics. For all four configurations, the pressure loss coefficient decreasedwith increasing Reynolds number at low Reynolds numbers. At high Reynolds numbers,the same trend persisted for the elliptical-tube configurations but was reversed forthe round-tube configurations.
Langley Research CenterNational Aeronautics and Space Administration
Hampton, VA 23665May 15, 1984
REFERENCES
1. Kilgore, Robert A; Goodyer, Michael J.; Adcock, Jerry B.; and Davenport,Edwin E.: The Cryogenic Wind-Tunnel Concept for High Reynolds Number Testing.NASA TN D-7762, 1974.
2. Polhamus, E. C.; Kilgore, R. A.; Adcock, J. B.; and Ray, E. J.: %_neLangley Cryo-genic High Reynolds Number Wind-Tunnel Program. Astronaut. & Aeronaut.,vol. 12, no. 10, Oct. 1974, pp. 30-40.
3. Kilgore, Robert A.; Adcock, Jerry B.; and Ray, Edward J.: Simulation of FlightTest Conditions in the Langley Pilot Transonic Cryogenic Tunnel. NASATN D-7811, 1974.
4. Kilgore, Robert A.: Design Features and Operational Characteristics of theLangley 0.3-Meter Transonic Cryogenic Tunnel. NASA TN D-8304, 1976.
5. Howell, Robert R.; and McKinney, Linwood W.: The U.S. 2.5-Meter Cryogenic HighReynolds Number Tunnel. High Reynolds Number Research, Donald D. Baals, ed.,NASA CP-2009, 1977, pp. 27-51.
6. Johnson, William G., Jr.; and Igoe, William B.: Aerodynamic Characteristics atLow Reynolds Numbers of Several Heat-Exchanger Configurations for Wind-TunnelUse. NASA TM-80188, 1979.
7. Ray, Edward J.; Ladson, Charles L.; Adcock, Jerry B.; Lawing, Pierce L.; and Hall,Robert M.: Review of Design and Operational Characteristics of the 0.3-MeterTransonic Cryogenic Tunnel. First International Symposium on Cryogenic WindTunnels, Proceedings of the Symposium held in the Department of Aeronautics andAstronautics at the University of Southampton, England, Apr. 3-5, 1979,pp. 28.1 - 28.15.
co
9.14Zlm
_ _--1.219m /-Plenum& f----LN2
J /- Screensection / testr / / section / injection
i! n-t..
• _ _
1.7 _
Fan section _ r
Nace,,e [T_ \ [T_ "_ Drive _-_
__ Sliding joints __]]'_ anchorSeCti°n _-_7_/_,._t-- !;/,lrliTunnel _/ /\ \ ///
Jl ' ' '
Figure I.- The Langley 0.3-Meter Transonic Cryogenic Tunnel with 20- by 60-cmtest section.
L-77-8237.1
Figure 2.- Tube-bundle heat-exchanger model installed in 20- by 60-cm test sectionof the Langley 0.3-Meter Transonic Cryogenic Tunnel.
-72.39 -31.75 Sta. 0 78.74
Pitot f Hot-wire I
prob20._3__ probe
"//////2" ///,h\\'_/ /.,_\,_,,_ _.-_._////
• _ Flow_
/L.227 =-
Tube bundlej H - _--Total-pressure-80.01 rake
Plan view
Figure 3.- The 20- by 60-cm test section of Langley 0.3-Meter Transonic CryogenicTunnel showing typical tube-bundle heat-exchanger model installation. Alldimensions in centimeters.
I0
___ 15.240
1.905 11.43_ "_--L905
,1.826
(D O O O---_/
0 0 0 0
0 0 0 0
0 0 0 0
Q 0 0 0
0 0 0 0
0 0 0 0
FI0w--" 0 0 0 0
C_ 0 C_ 0 _ "_-'_
O CZ> O O j _ Platefins,=_ .0256thick<D <Z> tED tED _ '
; I rO (D CD O IL _ ' ' '
i J'
o tED <D o I' _ ,_ I I j') i [
1.826 per2.54
Z4 rows in-line, 3.81x 3.81Porosity= 0.713
(a) Elliptical 1 configuration.
Figure 4.- Geometry of tube-bundle heat-exchanger models. All dimensions
in centimeters.
11
15.240
1.905_ _iI.43_ _ i.i051.826
O O O 0-_-_-0000
0000
OOOO
0000
OOOO
0000Flow--_ 0000
O O O O 60.803 ....._1< _1!71_O O O O ) 1.135
O O O O _-Flatefins, --_-
<D CD <D (_ .
3.81
(_ CD O C2_ f /
_ <D (_ CD _ rz1.826 ,
_4rows in-line, 3.81x3.81Porosity= 0.631
(b) Elliptical 2 configuration.
Figure 4.- Continued.
12
0 0 0 0
0 0 0 0I
O O O 0
0 0 0 0
0 0 0 0Flow
--"- 0 0 0 0 60.803 J_
0 0 0 O _ Platefins, _.
6,thick 1.59 diam
0 O 0 0I
0 0 0 0(
0 0 0 0
(c) Baseline configuration.
Figure 4.- Continued.
13
i 29.210 _/_25.400 _i 1.905
O Q Q ® Q 0- _46j
O O O O O Q
O O O O O O
O 0 O O O O
0 0 O O O OFlow
---- 0 0 O (D O O 6o.803
55.88 __0 0 O O O O _?,i_s,thick 1.59diam
0 O O Q O O ,"x
0 O 0 O O Q-Ti.08
0 0 0 0 0 0 -I
0 O O O (D Q 6Z_p__54
O (D © © ©-- ,6 rowsin-line, 5.08x 5.08Porosity= 0.623
(d) Six-row configuration.
Figure 4.- Concluded.
14
Temperatureprobe
1.27
r
10.16 c_
Flow 12 95 ,
I
(Do
Y
l 2.54_'----Wall
_1.91_
Figure 5.- Rake used to measure downstream total pressure. All dimensionsin centimeters.
15
3.0
M
2.6 051060 25.3072 25.9082 25.8
2.2 088 25.i
APtlq 099 25,0
1.4 _._: ir_i_ _
....!i....0 2 _ 6 8 i0 12
(wall)y, cm
(a) Elliptical 1 configuration.
40
3.6 M• 048• 063 13.2• 065 12.7
3. 2 .077 12.6•083 12.3
APtlq
2.8
2.4
2.0
0 2 4 6 8 i0 12(wall)
y, cm
(b) Elliptical 2 configuration.
Figure 6.- Pressure loss coefficient at nearly constant Reynolds number forvarious Mach numbers.
16
(c) Baseline configuration.
50
:_x:.>:::x;l:::_..t:t:: :::l>:Ix:;{..:-:l:;:{_!_ii_il_I!_l_N_l_'_l_4_..-M R, per meter
4.6 :::::::::::::::::::::::::::::::::::::::::::::::::::::: -'-_'_::::::::::::::::::::::::::::::::::::::::::::::::::::::0 .049 14.1 x 106 =_..
,-, . 063 14.3 _
::::::::::::::::::::::::::::::::::::::::................ z_ .077 13.9 i_;_
_i_r. _';t U [ t:; i:;_ :*'r: :-_..: 7..:; ::;: ::-_= :::: ;_;: :::3 _ .7,_:;::_:IV +_ _ _'_:
0 2 4 8 10 12
(wall) y, cm
(d) Six-row configuration.
Figure 6.- Concluded.
17
R, permeter
Elliptical1 o 25Xl06Elliptical2 _ 13Baseline _ 13Six Row I_ 13
10 --
8--
6- _ AAPt/q _
4- _L-_. _ _
2 -
, I I I , I l I , I0 .02 .04 .06 .08 .I
M
Figure 7,- Pressure loss coefficient as a function of Math number at constantReynolds number for y = 11 .4 cm.
18
3.4 R, per meter M
o L68x106 .052o 2.26 .049
3.0 <> 3.37 .049A 6.80 .050t_ Ii.O0 .050r,, 25.30 .051
Z6
APtlq 2.2
L8
1.4
LO0 2 4 6 8 10 12
(wall) y, cm
(a) Elliptical 1 configuration.
(b) Elliptical 2 configuration.
Figure 8.- Pressure loss coefficient at nearly constant Mach number forvarious Reynolds numbers.
19
(c) Baseline configuration.
5.8 R, per meter M
0 1.77x106 .051 ;_:;:ii_[] 3.58 .049 !tiiil!i::i_!i
5.4 <> 6. 15 .047 l_;i__Iii!A 7.13 .049 r;'r_ 14.23 .050 i!ii{3 2Z44 .050 _::::
5. 0 n 28.47 .050
4.2 ....
• _, , _ .Lii!i
0 2 4 6 8 I0 12(wall)
y, cm
(d) Six-row configuration.
Figure 8.- Concluded.
2O
100
50
20
fl Pt' q10
5
2
R, per meter
o Elliptical 1(> Elliptical 2~ Six rowl::. Baseline
Porosity
0.713.631.623.525
Figure 9.- Pressure loss coefficient as function of unit Reynolds numberfor y = 11.4 cm.
14--
12 --I
O Upstream[] Downstream
10 --
08 -- []
D[][]
U'-G 06-- D
04--[]
02 -- OO O
0 0 0 0 0o oo
0 ' _ r v I llrl w I I , i _II ; I ; ; , rit{
105 106 107 108R, per meter
(a) Elliptical I configuration.
Figure 10.- Longitudinal turbulence characteristics of tube-bundle heat-exchanger models.
• 14 --
• 12 --
0 Upstream[] Downstream
• 10 --E3
[]
[]• 08 --
U' []
D•06 -- [] []
[13
• 04 -- 0
• 02 -- o© 0 0
o oo o o °80 l l _ I I _ _II l i l I w f l_l I , , f I ,,,I
105 106 107 108R, per meter
(b) Elliptical 2 configuration.
Figure I0.- Continued.
• 14 --
• 12 --
© Upstream[] Downstream
• i0 --
[] [] []
U' .08 -- [] [] m__ [7 '
U o E_nn DD
• 06 --
•04 --
•02 --0 0
0 0
0 I I I l I ,Ill I I I I I fal! I I I I I IIII
105 106 107 108R, per meter
(c) Baseline configuration.
Figure I0.- Continued.
• 14 --[]
0 Upstream[3 13 Downstream
• 12 m [] []
[][]
• 10
• 08
U'
.06 m
•04
•02 _ o
o o
0 I i i i L I LiJ l i l i , ,,,1 I i l i i i,,l
105 106 107 108R, per meter
(d) Six-row configuration.
Figure 10.- Concluded.
1. Report No. I 2. GovernmentAccessionNo. 3. Recipient'sCatalogNo.NASA TM-85807 I
4. Title and Subtitle 5. Report Date
REYNOLDS NUMBER EFFECTS ON PRESSURE LOSS AND TURBULENCE June 1984
CHARACTERISTICS OF FOUR TUBE-BUNDLE HEAT EXCHANGERS 6. PerformingOrganizationCode
505-31 -53-08
7. Author(s) 8. PerformingOrganizationReport No.
William B. Igoe and Garl L. Gentry, Jr. L-15721
10. Work Unit No.9. PerformingOrganizationNameand Address
NASA Langley Research Center 11 Contractor GrantNoHampton, VA 23665
13. Type of Report and Period Covered12. SponsoringAgency Name and Address
Technical MemorandumNational Aeronautics and Space Administration
14. SponsoringAgency CodeWashington, DC 20546
5. SupplementaryNotes
16. Abstract
The aerodynamic characteristics of pressure loss and turbulence on four tube-bundle
configurations representing heat-exchanger geometries with nominally the same heat
capacity were measured as a function of Reynolds numbers from about 4000 to 400 000
based on tube hydraulic diameter. Two configurations had elliptical tubes, the other
two had round tubes, and all four had plate fins. The elliptical-tube configurations
had lower pressure loss and turbulence characteristics than the round-tube configura-tions over the entire Reynolds number range.
,17. Key Words (Sugg_ted by Author(s)) 18. Distribution Statement
Finned tubes Wind tunnel Unclassified - UnlimitedHeat exchangersPressure loss
Turbulence
Reynolds number effects Subject Category 02
19. S_urity _a_if.(ofthisreport) 120. S_urityClassif.(ofthis_) 21. No. of Pages I 22. Dice
Unclassified I Unclassified 26 I A03
ForsalebytheNationalTechnicalInformationService,Sprinsfield,Virsinia2216! NASA-Langley,]98e
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