Experimental Study of Heat Transfer During Quenching of Steel Cylinders in Boiling Nanofluid
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Copyright © 2023 by American Scientific Publishers Journal of Nanofluids
All rights reserved. Vol. 12, pp. 348–355, 2023
Printed in the United States of America (www.aspbs.com/jon)
Experimental Study of Heat Transfer During
Quenching of Steel Cylinders in Boiling Nanofluid
Vasyl Moraru∗ , Dmytro Komysh∗ , Mykola Sydorenko, and Serhiy Sydorenko
Department of Thermo-Chemical Processes and Nanotechnologies, Gas Institute of National Academy of Sciences,
39 Degtyarivska str., Kyiv, 03113, Ukraine
Current study was dedicated to explore cooling performance of TiO2 nanofluid. Preliminary tests have shown the
possibility of significant improvement of emergency cooling performance by nanofluids in the case of overheated
surfaces. Tests that were held during current investigation were performed with cylinders of stainless steel,
which were used as an overheated surface. The temperature was recorded by a digital system of 3 type-K
thermocouples. The object, preheated in a furnace to high temperatures (600–800 C), was immersed into
boiling distilled water. Usage of the set of thermocouples allows to determine heat flow in steel cylinder by its
temperature distribution. The implementation of emergency cooling was to add a certain amount of nanofluid
concentrate to the volume of boiling distilled water. The experiment was continued until the complete cooling of
the object (up to 100 C—the temperature of the surrounding liquid). Calculations confirmed increase of heat
transfer coefficient for NF and, respectively, about 40% decrease in cooling time for NanoFluid compared to
ARTICLE
distilled water was observed. Three method of determination of heat transfer coefficient were compared.
KEYWORDS: Nanofluids, Pool Boiling Heat Transfer, Boiling Crisis, Overheated Surfaces, Emergency Cooling.
IP: 5.10.31.211 On: Sat, 22 Jul 2023 00:44:45
Copyright: American Scientific Publishers
1. INTRODUCTION Delivered byboundary
Ingenta layer of the liquid significantly reduce the time
Modern heat-loaded energy facilities, for example, nuclear of transition to bubble boiling.
power plants (NPP) have the urgency of intensification of Successful cooling of nichrome wires (0.3 mm diame-
emergency cooling in case of accident or similar out-of- ter) from above 500 C down to 130 C performed under
order situations. pool boiling conditions had discovered a new page of per-
This is due to not effective enough emergency cooling spective application of new nanofluids at emergency acci-
systems that use single-phase liquids as a cooling agent. dents which are accompanied with a large release of heat
The main problem in such processes is film boiling, which while operating of high-loaded equipment.1 2
does not allow coolant to perform efficient heat removal Kim et al.3 conducted studies on the cooling of stain-
from overheated heat transfer surfaces. It is important in less steel spheres with a diameter of 9.5 mm in NF based
the intensification of heat transfer processes of this type on alumina with different concentrations (0.1%, 0.01%,
to minimize the transition time from the film boiling to and 0.001% vol.). The initial temperature of the spheres
nucleate boiling modes. was 1000 C, and the coolant temperature was 100 C.
Modern coolants, such as nanofluids (NFs), can solve The researchers observed a rapid transition of film boiling
this problem. The properties of NFs allow reducing the to nucleate boiling. In addition, they noted a significant
increase in the minimum heat flux without clearing the ball
cooling time from above thousand down to hundreds of
of nanoparticles (NPs) deposit between experiments.
degrees Celsius significantly compared to water. NFs is
In work,4 Kim et al. conducted experiments on the cool-
able to interact efficiently with the heat transfer surface by
ing of spheres made of steel and zirconium alloys. They
modifying it. This allows the cooling suspension to pene-
used NFs with NPs of Al2 O3 , SiO2 and diamond (C) at
trate directly thru vapor film to accelerate the formation of
low NPs concentrations. The researchers reported an inten-
a bubble boiling regime. Modification of the surface and
sification of cooling in repeated experiments and the depo-
change in the nature of the temperature distribution in the
sition of NPs on the sphere.
In work,5 Kim et al. performed experiments on metal-
∗
lic rodlets and spheres at both saturated and subcooled
Authors to whom correspondence should be addressed.
Emails: vasily.moraru@gmail.com, dmytro.komysh@outlook.com conditions using pure water and water-based nanofluids
Received: 24 December 2021 with alumina nanoparticles of 0.1% by volume. The results
Accepted: 25 May 2022 demonstrate that while the initial quenching behavior in
348 J. Nanofluids 2023, Vol. 12, No. 2 2169-432X/2023/12/348/008 doi:10.1166/jon.2023.1915
Moraru et al. Experimental Study of Heat Transfer During Quenching of Steel Cylinders in Boiling Nanofluid
nanofluids is identical to that in pure water, both the min- experimentally obtained in saturate pure water and two
imum heat flux point temperature and quench front speed nanofluids (SiO2 and TiO2 ) with 0.01 wt%. The cylinder
are significantly enhanced in subsequent quenching repe- was vertically lowered into the pool of saturated water and
titions due to nanoparticle deposition. its temporal center temperature was measured by a thermo-
Authors in work6 investigated the cooling behavior of couple. The boiling curves were then obtained by solving
aqueous NFs containing different NP volume fractions of a transient one-dimensional inverse heat conduction model
Al2 O3 , SiO2 , TiO2 , and CuO (concentrations of 0.01%, and measuring the temperature at the center of the cylinder.
0.05%, and 0.1% vol.), brass rod heated to high tempera- The images of the surface morphology and uniformity of
tures (diameter 20 mm, height 75 mm). The experiments the deposited SiO2 and TiO2 nanoparticles were captured
were performed under saturated conditions at atmospheric by the scanning electron microscope (SEM). The cooling
pressure. The researchers obtained cooling curves that time during quenching of the cylinder was decreased about
indicate the efficiency of using NFs for cooling, especially 50% by nanoparticles deposition. However, the SiO2 and
with SiO2 -based NF. TiO2 nano particle deposition have similar critical heat flux
In this study, the heat fluxes are predicted by using increment (up to 120%). Film boiling heat transfer rate
inverse heat transfer method. According to this method, increased by repetitive quenching in SiO2 nanofluid.
firstly the heat transfer coefficient () was estimated. The Recent publications that deal with preparation, synthe-
heat transfer coefficient was calculated using the differ- sis, thermophysical properties, experimental aspects and
ence between the rates of energy obtained. The difference numerical studies of hybrid nanofluids in thermal appli-
between the estimated and calculated values was suc- cations were summarized. The main reasons behind the
cessively selected as the convergence criterion. The con- enhanced performance of heat transfer in hybrid nanofluids
vergence criterion was selected as 0.01 W/(m K). 2 6 is the improved effective thermal conductivity and kinetic
7
In work, the authors cooled the brass ball (diameter motion of nanoparticles. Despite the enhanced heat trans-
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10 mm) from 600 C down to 100 C in preheated to 92 C fer of hybrid nanofluids, many challenges, penalties and
liquids (pure water and NF). They used NFs based on NPs obstacles are facing designers and researches working in
of SiO2 , Al2 O3 , TiO2 , CuO with the concentration of 0.1% this field. For instance, higher pumping power is needed
vol. The researchers observed the best results when using to overcome pressure drop, stability analysis, the effect of
IP: 5.10.31.211 On: Sat, sizes
22 Juland 2023 00:44:45
shapes of nanocomposite materials particles as
SiO2 NPs in NF. Copyright: American Scientific Publishers
8
In work some parameters such as quenching and well
boil- by Ingentaas identifying the mechanisms for thermal and rhe-
Delivered
ing curves of a stainless steel cylindrical rod 80 mm long ological properties enhancement. These challenges should
and having a diameter of 15 mm were experimentally be viewed as opportunities to carry out more research.
obtained in saturating pure water and two nanofluids (SiO2 Finally, more effort is required in determining use of
and TiO2 ) with 0.01 wt.%. Researchers find out that the hybrid nanofluids to serve as a promising coolant in indus-
10
CHF for TiO2 and SiO2 was significantly increased with trial sector.
repetitive insertion into the pool.
According to the works cited above, the following con- 2. EXPERIMENTAL DETAILS
clusion can be drawn: It is advisable to use NF with a 2.1. Materials and Methods
concentration of NPs from 0.05 to 0.5 vol.%; the initial Some thermophysical characteristics of the objects of
temperature of the cooled object 600–1000 C; the tem- study are given in Table I. In these experiments, we used
perature of the coolants is 95–100 C. aqueous nanofluid (NF) based on TiO2 nanodispersed par-
In paper9 a finite element technique has been used to ticles (NPs) with an average size of 130 nm. The weight
predict the residual and thermal stresses which occur dur- concentration of NPs in the cooling volume of the resulted
ing water quenching of solid stainless-steel spherical balls. suspension is 0.5% mass.
The variations of residual stresses at different positions and The initial 5%-nanofluid TiO2 /water were obtained by
cross-sections, e.g., the radial, axial and tangential direc- a two-stage method. 50 g of micro powder of rutile
tions, have been examined. Also, the influence of heat grade RO-2 (Sumy PO Chimprom, Ukraine) was soaked
transfer coefficient, the initial temperature and the harden-
ing assumption on residual stress results has been inves- Table I. Some physicochemical properties of research objects.
tigated. The results show that high compressive residual
stresses occur along the cooling surface. The paper com- Thermal
conductivity, Specific heat Melting
pares these measurements with the finite element results
Density, , W/m · K capacity, Cp, point, Tboiling ,
as well as comparing the measured cooling temperature Objects kg/m3 at 20 C J/kg · K
C
C
history with simulation. Overall there is good agreement
Distilled water 998 0,613 4190 0,0 100
between the predicted and measured stresses.
8 TiO2 (rutile) 4230 8,40 692 1870 2972
In study, some parameters such as quenching and Still cylinder 7800 16,5 536 1450 >2000
boiling curves of a stainless steel cylindrical rod were
J. Nanofluids, 12, 348–355, 2023 349
Experimental Study of Heat Transfer During Quenching of Steel Cylinders in Boiling Nanofluid Moraru et al.
in 988 ml of distilled water with pH 9, previously adjusted
with 0.1 N NaOH solution. Next, the mixture was dis-
persed on a high-speed homogenizer RT-2 for 10 minutes.
Then the suspension was processed for 15 minutes using
an ultrasonic disperser UZDN-2T at a frequency of 22 kHz
and a power of 500 W. NFs with lower concentrations of
TiO2 (0.25, 0.5, 0.75, 1.0, and 1.5 wt.%) were obtained
by diluting the initial 5% suspension with the base liquid
followed by homogenization.
The stability of the obtained NFs was assessed visually
by the kinetics of sedimentation, as well as by the value
of the zeta ()-potential.
The dispersed (granulometric) composition and -
potential of NFs were determined on a ZetaSizer NANO-
ZS laser correlation spectrometer (Malvern Instrument,
UK). Measurements of the particle size distribution of the
working nanofluid with 0.5% TiO2 showed the following
results: polydispersity range: 60–250 nm, particles aver-
age size: 132 nm, average zeta-potential is −39.7 mV,
which indicates a high aggregative stability of the disper-
sion (sedimentation stability was at least 7 days).
The viscosity of nanofluids was measured using a VPJ-
2 glass capillary viscometer with a capillary diameter of
ARTICLE
0.56 mm or a Brookfield LVDVII +Pro viscometer (USA).
Dynamic viscosity () at 15 C and effective thermal
conductivity (k) for working NF with 0.5% TiO2 were
1.1 mPa·s and 0.68 W/(mK), respectively. In the studied
IP: 5.10.31.211 On: Sat, 22 Jul 2023 00:44:45
range of solid phase contents (Cs = 0.1–1.5%
Copyright:
wt.),American
the vis- Scientific Publishers
cosity of NFs TiO2 /water increased linearly withDelivered
increas- by Ingenta
ing mass concentration of rutile, and its values are in good
agreement with the literature data.11
2.2. Experimental Procedure Fig. 1. Image of steel cylinder after surface restoration.
The implementation of emergency cooling is held by
adding to the volume of boiling distilled water a certain first in the center of the upper base of the cylinder, the
amount of NF concentrate (T ≈ 96 ÷ 98 C). Preheated up second at a distance of 7.5 mm from the center, the third
to 800 C cylinder was immersed into boiling (∼98 C) at a distance of 1 mm from the wall) to accommodate ther-
distilled water. The transition from film boiling to nucle- mocouples 1. The holes are located in such a way so that
ate boiling was observed during tests. When the object we can record the temperature change at three points and
reached a temperature of 430 C, the film boiling regime monitor the nature of the temperature distribution of the
changed into a transient and subsequently into a nucle- object over its thickness. Therefore, only one thermocou-
ate boiling mode, which was accompanied by a signifi- ple was used for calculations in current article.
cant increase in a steam release. Image of steel cylinder Object 7 is heated in the furnace 4. Heating continues
after heating surface is restored for next test is shown on to a temperature of 500∼800 C, and with the help of the
Figure 1. holder 3 fixed by a threaded connection with object 7 it is
The test unit (Fig. 2) contains: support stage 12, lamp possible to move the stated above object clearly vertically
13, camera 14, furnace 4, and mechanism for descend and relative to the furnace and the vessel with the test liq-
rise 15; of test object 7, in which Type-K thermocouples uid. The temperature of the object is measured using three
are placed at a depth of 20 mm. The object is fixed on a type-K thermocouples 1, which are placed in the object.
Holder 3; thermocouples 1 and 11 signals are accepted by The temperature in vessel 9 is fixed by means of a ther-
ADC 5 and transfer digital signal to PC 6. Furnace 4 and mocouple 11 (type K) and is maintained at the level of
heater 10 power supply is provided by Power supply unit 95 ÷ 100 C.
8. Rollers 2 allow uniform descent of object 7 into test When the object reaches the required temperature, it
vessel 9 by operating mechanism 15. moves vertically into vessel 9 with the test liquid.
Object 7 is a stainless steel cylinder ø30 mm and 40 mm The series of experiments begins with cooling the object
height, with three holes 20 mm deep and ø1.5 mm (the first in the distilled water and then in the NF. Between
350 J. Nanofluids, 12, 348–355, 2023
Moraru et al. Experimental Study of Heat Transfer During Quenching of Steel Cylinders in Boiling Nanofluid
3. RESULTS AND DISCUSSION
First of all, it must be emphasized that in this work
we studied the heat transfer during NF boiling, which
is always accompanied by the deposition of a porous
layer of nanoparticles on the heating surface. This layer
is known to be a powerful generator of the formation of
steam bubbles-convection enhancers. Therefore, in contrast
to the mode of forced heat transfer without boiling, in
heat exchange processes with boiling NFs (for example,
during emergency cooling of superheated bodies), such
NFs characteristics as viscosity () and thermal conduc-
tivity (k) play a secondary role, significantly giving way
to convection.
Concerning the role of thermal conductivity and viscos-
ity of the studied TiO2 /water nanofluid in heat exchange
during emergency cooling of superheated surfaces, the fol-
Fig. 2. Scheme of test unit for investigation of emergency cooling lowing should also be added:
of overheated objects by nanofluids. 1–Thermocouples type-K (3 pcs.); (1) Our studies have shown that with the studied vol-
2–Rollers; 3–Holder of the test object (stainless pipe); 4–Furnace; 5– ume fraction of 0.1–0.2, TiO2 /water nanofluids are char-
Temperature measurement unit (normalizers and ADC); 6–PC; 7–Test
acterized by low values of effective thermal conductivity
object; 8–Power supply; 9–Vessel; 10–Coolant heater; 11–Thermocouples
type-K; 12–Stand; 13–Lamp; 14–Camera; 15–Immerse mechanism. (k = 0.64–0.68 W/m·K) and dynamic viscosity ( = 105–
1.1 mPa·s), which are close to those for the base liquid
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experiments, the object is subjected to mechanical treat- (water).
ment in the form of polishing, which must be carried out (2) Due to the fact that thermal conductivity (k) and
to minimize the possible impact of the deposited sediment viscosity () have opposite effects on heat transfer dur-
on the heat transfer parameters. IP: 5.10.31.211 On: Sat, 22 ing Jul
boiling,
2023 their contributions almost cancel each other
00:44:45
Observing of cooling curves is realized thanks American
Copyright: to ADC Scientific
out and their influence on the heat transfer coefficient is
Publishers
and specially created software. Recording takes Delivered place in bynegligible.
Ingenta Related calculation of heat trafer are repre-
real-time and is displayed on the PC display. sented in Table II.
The obtained boiling curves allow us to evaluate the As can be seen from Figure 4, for the NF, a notice-
efficiency of the studied NF in the process of emergency able decrease for up to 20∼25% shortage of cooling
cooling of overheated objects.
The experiment was continued until the object was Table II. Experimental and calculated data for the determination of
cooled entirely (to 100 C—the temperature of the cool- heat-transfer coefficients at fluids boiling in terms of overheated cylinder
ing suspension). According to the decrease in the heater cooling.
temperature, the intensity of boiling increased visually. to to tw
Deposits of NPs in the process of NF boiling form an experim., , calculated, calculated, , T = tw − tsat ,
intermittent layer on the heat transfer surface, which can # C s C C W/m2 ·K K
be seen in Figure 3. Distilled water
1 540 60 530 500 250 400
2 500 70 500 465 250 365
3 450 80 440 410 250 310
4 400 90 400 363 250 263
5 350 96 363 325 285 225
6 330 100 332 280 300 200
7 250 104 240 220 430 120
8 200 108 203 173 525 73
9 150 115 145 132 700 32
10 130 120 123 117 800 17
Nanofluid TiO2
11 500 54 490 428 350 328
12 450 60 460 400 350 300
13 400 65 400 370 380 270
14 300 70 310 275 450 175
15 200 75 210 185 750 85
Fig. 3. NF’s of TiO2 deposited on the cylinder during cooling in NF 16 140 86 117 113 1200 13
((a) Image magnification ×400; (b) Image magnification ×1600).
J. Nanofluids, 12, 348–355, 2023 351
Experimental Study of Heat Transfer During Quenching of Steel Cylinders in Boiling Nanofluid Moraru et al.
On the first stage of the investigation, it is necessary to
determine the heat transfer coefficients. The cooled body
is a steel cylinder (AISI321) with size h = 40 mm, d =
30 mm with the following chemical and physical proper-
ties (Table I):
- thermal conductivity–c = 16 W/m·K;
- density– c = 7800 kg/m3 ;
- heat capacity–Cc (J/kg·K), depending on the temper-
ature,9 the coefficient of thermal conductivity:
c
a= (2)
Cc · c
The calculation is performed with the following param-
eters (Fig. 4): at = 70 s experimental time—the temper-
Fig. 4. Cooling graphs for pure distilled water (DW) (1) and TiO2 -based
ature in the center of the cylinder to ≈ 300 C, the initial
nanofluid (2). temperature of the center of the cylinder tst = 800 C, NF
temperature tsat = 100 C. Since we assume to = 300 C
time is observed compared to distilled water. The impor-
then Cc = 536 J/kg·K, which corresponds to:
tant point is that the reduction of the cooling time is
mainly achieved by reducing the cooling time in the high- 2
c 16 −6 m
temperature range. This is a noticeable difference of 20% a = = = 383 × 10 (3)
Cc · c 536 · 7800 s
in cooling time from 700 to 400 C. The duration of the
temperature transition from 400 to 100 C remains almost The liquid in which the cylinder is immersed—NF
ARTICLE
the same for all samples. Detailed calculation of relative (TiO 2 based NF CTiO2 = 0,5% mass), has temperature of
cooling time shortage for NF is represented in Table III. t sat = 100 C.
Analysis of different cooling/boiling modes is a subject of The calculation is first performed under the assump-
future research. IP: 5.10.31.211 On: Sat, tion
22 that
Jul the 00:44:45
2023 cylinder is infinitely long. The heat transfer
Copyright: American
During the insertion of the rodlet to the fluid, a Scientific
coefficient Publishers
(HTC) is accepted on the basis of preliminary
Delivered bycalculations
Ingenta = 450 W/m2 ·K.
constant heat flux due to the high speed of the rod
immersion is considered. The governing equation for the The value of similarity numbers for the cylinder is cal-
one-dimensional transient heat conduction within the solu- culated:
tion domain can be written as follows: Fourier number:
a· 383 × 10−6 · 70
1 T T 1 T Fo = = = 119 (4)
r = (1) R2 00152
r r r t
Table III. Absolute and relative comparison of cooling time by distilled Where R = D/2 = 0.03/2 = 0.015 m—definitive size.
water and nanofluid respectively. Bio number:
Time, s · R 450 · 0015
Bi = = = 042 (5)
Temperature, C DW NF Shortage of cooling time, % c 16
800 0 0 0 According to these data from Ref. [12] we define the
700 27 22 18.52 values of dimensionless temperatures:
600 45 37 17.78
500 68 54 20.59
For cylinder axis:
450 80 61 23.75
t −t
400 90 66 26.67 0
= 0 sat = 042 (6)
w − tsat
t
375 94 67 28.72 C
350 96 68 29.17
325 99 69 30.30 for cylinder wall:
300 101 70 30.69
tw − tsat
275 102 71 30.39 w
= = 035 (7)
250 104 72 30.78
C tf − tsat
225 106 73 31.13
200 108 75 30.55 where:
175 110 77 30.00 t0 —temperature in the middle of cylinder axis;
150 114 79 30.70
tw —temperature on the middle of cylinder sidewall;
125 123 86 30.08
105 135 90 33.33 tst —initial temperature of the cylinder (800 C);
tsat —constant temperature of the liquid (100 C).
352 J. Nanofluids, 12, 348–355, 2023
Moraru et al. Experimental Study of Heat Transfer During Quenching of Steel Cylinders in Boiling Nanofluid
ARTICLE
Fig. 5. Experimental (1, 3) and calculated (2, 4) curves of cooling an overheated cylinder in DW (1, 2) and in TiO2 -nanofluid (3, 4), plotted using
measured temperatures of the cylinder’s center (1, 3) and calculated temperatures of cylinder’s walls (2, 4).
IP: 5.10.31.211 On: Sat, 22 Jul 2023 00:44:45
Copyright:
Next, the influence of the height of the cylinder American
is taken Scientific
SimilarPublishers
calculations are performed for the middle of the
Delivered by Ingenta
into account, which is the result of the intersection of the cylinder axis:
pipe and the plate, taking into account that the thickness
of the plate 2· = h = 0,04 M, where = 0,02 M. 0
= 0
× 0
= 072 × 042 = 030 (12)
Since the physical properties of the plate are the same PL C
as for the cylinder, then:
Since 0 / = t0 − tsat /tw − tsat , then:
−6
a· 383 × 10 · 70
Fo = 2 = = 067 (8)
0022 t0 = 0 × tw − tsat + tsat = 030 × 800 − 100
· R 450 · 002 + 100 = 310 C (13)
Bi = = = 056 (9)
c 16
Same calculations are performed for distilled water.
According to these data and data contained in Ref. [12], Consistently changing the time point of the experiment
the values of dimensionless temperatures for the plate are: for both NF and DW and selecting for each the value
0 / PL = 072 for axis and w / PL = 060 for side- of the heat transfer coefficient , at which the experimental
wall (Fig. 5). (Fig. 4) and calculated (Table II) values of temperature t0
By multiplying the corresponding values of dimension- are coincident. The obtained data are used to construct a
less temperatures, we find their values for the middle of graphical dependence = f ( T), where T = tw − tsat
the side surface W / and the middle of the axis 0 / for both NF and DW (Fig. 6).
Usually, higher efficiency of cooling by nanofluids is
w
= w
× 0
= 035 × 072 = 025 (10) achieved in the modes of non-stationary and nucleate boil-
C PL ing, which corresponds to the results obtained earlier in
Since in the general case s / = tw − tsat /tst − tsat , the study of NFs boiling at free convection1 4 and with the
then: results of other studies.3–8
Another way to define the temperature distributions in
tw = w
× tw − tsat + tsat = 025 × 800 − 100 the test rod is the finite-volume method for the steady-state
condition, and then the rate of total energy of the rod is
+ 100 = 275 C (11) determined. In this calculation, two boundary conditions
J. Nanofluids, 12, 348–355, 2023 353Experimental Study of Heat Transfer During Quenching of Steel Cylinders in Boiling Nanofluid Moraru et al.
ARTICLE
Fig. 6. Dependency of HTC by temperature difference T = tw − tsat , while cooling of an overheated cylinder; 1–Distilled water, 2–Nanofulid.
are used. The first is the measuredIP: center temperature
5.10.31.211 On:ofSat, 22Thus, the results
Jul 2023 of this work show a significantly higher
00:44:45
rod. The second is defined as follows:Copyright: American Scientific
intensification
Publishers transfer upon cooling with nanoflu-
of heat
Delivered byids
Ingenta
compared to DW.
dT
−k = T − Tsat (14) Despite obtained data demonstrate good correlation with
dr r=r0 other researches there are still some differences in total
numbers. Most of investigations show slight difference
The described calculations is repeated for the next mea- at high temperatures between theoretical and experimen-
sured center temperature. tal results. Large number of papers states initiation of
In the case of quenching or emergency cooling, rapid transient boiling mode at about 380–450 C which does
cooling and rapid destabilization of the film boil with the not corresponds to Kutateladze13 or Nukiyama14 numbers
achievement of a transient boiling mode is important so (500–600 C).
that the liquid can contact the heat exchange surface. At
this moment, a porous layer of nanoparticles is formed,
which leads to further intensification of heat transfer. 4. CONCLUSIONS
Figure 6 shows the change in the calculated value of During cooling of superheated bodies in both DW and
the heat transfer coefficient as a function of temperature TiO2 -nanofluid, as their temperature decreases, an increase
difference T = tw − tsat , when the overheated cylinder is in the boiling intensity is observed. This sequence of
cooled in distilled water and in TiO2 -nanofluid. From the changes in the intensity of the boiling process is due to
graphs it is seen that HTC is much higher for NF than the change of the film boiling mode with a low heat trans-
for DW (40% at film boiling and 30% at transient mode). fer coefficient (HTC) to the mode of transient and bubble
This explains the fact that the cooling of the cylinder in boiling with a high HTC.
the NF is completed much faster. Thus, at = 90 s of For nanofluid, there is a significantly higher intensifi-
the experiment, the temperature in the cylinder’s center cation of heat transfer and a noticeable reduction in the
decreases to 100 C, when cooling occurs in NF, and to cooling time of the object compared to distilled water,
400 C, when cooling occurs in DW. which is very important in the elimination of emergencies,
The important point is that the reduction of cooling especially in nuclear energy.
time, in this case, is achieved mainly by cooling accelerat- The calculation of temperatures in the cylinder by the
ing in the high-temperature range. This noticeable differ- method of non-stationary thermal conductivity allowed
ence is 20% of the cooling time in the range T from 700 to determine the temperature of the outer wall and the
to 400 C. value of T = Tw − Tsat based to the readings of the
354 J. Nanofluids, 12, 348–355, 2023Moraru et al. Experimental Study of Heat Transfer During Quenching of Steel Cylinders in Boiling Nanofluid
thermocouple placed in the center of the cylinder (t0 ). sat Saturation
According to the calculated data, the graphical depen- w Wall
dences = f T are presented for both NF and DW.
Analysis of these graphs shows a significantly higher Conflicts of Interest
intensification of heat transfer during nanofluid cooling The authors declare no conflicts of interest.
compared to DW. The HTC value for NF is much higher
than for DW (40% at film boiling and 30% at transient Acknowledgments: The research was performed in
mode). accordance with the departmental theme of the Gas Insti-
Further research will include comparison of different tute of the NAS of Ukraine in accordance with the Tar-
methods for calculation of HTC ant wall temperature. At get Program of Research of the Department of Physical
current stage of the test object construction it does not and Technical Problems of Energy of the NAS of Ukraine
allow to calculate temperatures with satisfactory precision. “Fundamental Research of Energy Conversion and Use”
Influence of different composition of nanofluids and for 2017–2021 years. “Creation of new nanomaterials and
concentration of solid particles are also in our field of nanotechnologies” for 2015–2019, state. registration No
interest. 0115U005087.
NOMENCLATURE AND ACRONYMS
References and Notes
ADC Analog-to-digital converter 1. B. I. Bondarenko, V. N. Moraru, S. V. Sydorenko, D. V. Komysh,
Bi Bio number and A. I. Khovavko, Tech. Phys. Lett. 38, 853 (2012).
C Specific heat capacity, J/kg·K 2. B. I. Bondarenko, V. N. Moraru, S. V. Sydorenko, and D. V. Komysh,
D Diameter, m Tech. Phys. Lett. 42, 675 (2016).
Fo Fourier number 3. H. Kim, J. Buongiorno, L. W. Hu, T. McKrell, and G. DeWitt, ASME
Int. Mech. Eng. Congr. Expo. Proc. 10, 1839 (2009).
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NF Nanofluid 4. H. Kim, G. DeWitt, T. McKrell, J. Buongiorno, and L. Hu, Int. J.
NP Nanoparticle Multiph. Flow 35, 427 (2009).
NPP Nuclear power plant; 5. H. Kim, J. Buongiorno, L.-W. Hu, and T. McKrell, Int. J. Heat Mass
R Radius, m Transf. 53, 1542 (2010).
IP: 5.10.31.211 On: Sat, 22 6. Jul
D. 2023 00:44:45
Ciloglu and A. Bolukbasi, Nucl. Eng. Des. 241, 2519
t Temperature, C Copyright: American Scientific
(2011).Publishers
T Bulk fluid temperature, K Delivered by 7.
Ingenta
D. Ciloglu, A. Bolukbasi, and H. Cifci, Int. J. Mater. Metall. Eng.
k Effective thermal conductivity, 9, 694 (2015).
a Coefficient of thermal conductivity, m2 /s 8. A. Rahimian, H. Kazeminejad, H. Khalafi, S. M. Mirvakili, and A.
Akhavan, Int. J. Eng. 33, 28 (2020).
Greek Symbols 9. S. Hossain, M. R. Daymond, C. E. Truman, and D. J. Smith, Mater.
Heat transfer coefficient, W/(m2 ·K) Sci. Eng. A 373, 339 (2004).
10. A. A. Hussien, W. Al-Kouz, N. Md Yusop, M. Z. Abdullah,
Thermal conductivity, W/(m·K) and A. A. Janvekar, Stroj. Vestnik/Journal Mech. Eng. 65, 441
Dynamic viscosity, mPa·s (2019).
Electrokinetic potential, mV 11. H. K. Naina, R. Gupta, H. Setia, and R. K. Wanchoo, J. Nanofluids
Density, kg/m3 1, 161 (2012).
Dimensionless temperature 12. M. A. Mikheev and I. M. Mikheeva, Basics of Heat Transfer, 2nd
edn., Energy, Moskow (1977).
13. S. S. Kutateladze, Heat Transfer in Condensation and Boiling,
Subscripts 2nd edn., Leningrad Division of State Publishing House, Moscow
c Cylinder (1952).
f Fluid 14. S. Nukiyama, Int. J. Heat Mass Transf. 9, 1419 (1966).
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