If someone is interested to this paper, please just downloaded it here.

2. 1411-5565
DEWAN REDAKSI
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Wakil Ketua penyunting
tGNK yudhyadi
Penyunting petaksana
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Tata Usaha
Anrta Wulansari
Jurnarreknrk
R*''yrs/l terbrt 2 (dua) karisetahirn pada butan Junr dan Desember
,,,:#''ffffiIfl,i*,iifrfl,}r,l,,
#HJ:: :,,,,
ISSN
JURT{AT

3. VOLUME 14 NOMOR 2, Desember 2413
DAFTAR ISI
EDITORIAL
. Sifat Mekanik Komposit Pet-Serabut Kelapa-Tempurung Kelapa/Resin
Poliester Tak Jenuh {Mechanical properties of PET-coconut fibre-coconut
shell/U nsatu rated Polyesfer Resrn)
( Nasmi Herlina Sari, Sugiman, Sujita, Emmy Dyah S. )
. Pembuatan Dan Uji Briket Biomassa Dari Buah Nyamplung (Production and
testing of brbmass briquette of nyamplung fruit)
(Hendry Sakke Tira, Abdurrahman)
. Pengaruh Pendidihan Di Upsfream Loop Terhadap Ketidak Stabilan DariAliran
Mendidih Di Dalam Saluran lMikro (Effecfs of Boiling in the Upstream Loop on
lnstability of Flow Boiling in a Microchannef)
(Mirmanto)
. Studi Tingkat Produktivitas lndustri Mikro Kecil Untuk Meningkatkan Daya
Saing lndustri (Studi kasus: Di Kabupaten Lombok Barat) (Study of
Productivity of Small and Micro Scale Export Oriented Products lndustry to
improve its competitiveness (case study: in West Lombok Regency-NTB)
(Suartika, Alit Triadi, Yudhyadi, Okariawan, Wijana)
o Analisa Kinerja Sistem Ofcdm I PSK Berbasis Wavelet Dan Berbasis
Fft(Pertormance analysis of 8 PSK OFCDM sysfem Based on Wavelet and
Based on FFT )
(Sudi mariyanto Al Sasongko,l Made BudiSuksmadana, Parlinawati)
o Analisis Hidrograf Satuan Untuk Daerah Aliran Sungai Berbentuk Bulu (Unif
Hydrograph Analyses for Fury Watershed)
(Humairo Saidah, Muhamad Ulwan, Nurun Ainuddin)
o Kiflerja Jaringan lrigasi Berdasarkan Kerapatan Bangunan Dan Kerumitan
Jaringan Pada Daerah lrigasi Tolo Tangga (Pertormance Of lrrigation Network
Eased on Network Complexity At Tolo Tangga lnigation Network Area)
(Salehudin, M. Birgus Budianto, L. Wirahman W., RajabiMubarak)
. Tinjauan Kuat Acuan Kayu Lokal Berdasarkan Atas Pemilahan Secara
Mekanik (Review Of Reference Wood Sfrong Local Sorting Based On The
Mechanicaf
(AryaniRofaida)
r Evaluasi Awal Potensi Likuifaksi Di Kota Mataram (lnitial Evaluation of
Liquefaction Potentialin The Mataram City)
(Muhajirah, Agung Prabowo, lsya Ashari)
o Evaluasi Kelayakan Tarif Angkutan Penyeberangan Di Kawasan Taman
Wisata Alam Laut Gili Matra Kecamatan Pemenang Kabupaten Lombok Utara
(Feasibility Study of Transport Rafres in Natural Park Marine Tourism Gili Matra
Sab-drsfncf of Pemenang North Lombok Regency)
(Rohani)
fis - 124
. Kewajiban Perusahaan Memberikan Cuti Hamil Atau Melahirkan Terhadap 168 - 173
Tenaga Kerja Wanita (The Liability Of Company to Give an Off Duty Of
Women Labor That Pregnant Or Has Giving Birth )
(Nurun Ainuddin)
ISSN:1411-5565
I
ii
92-99
1 00-1 05
106- 114
121 - 128
129 -',134
135 - 140
141 - 145
146 -'156
157 - 167
Jumal REKAYASA, Volume 14 No 2, Desem er 2013

4. )h
ci
---'ml Teknik REKAyASA, Volume t4 No 2 Desember 2013
PENGARUH PENDIDTHAN DI UPSTREAM LOOP TERHADAP KETIDAK
STABTLAN DARI ALIRAI.I MENDIDIH DI DALAM SALURAN MIKRO
Effects of Boiting in the tJpstream Loop on tnstability of Flow Boiling in
a Microchannel
Mirmanto
Jurusan Teknik Mesin Fakultas Teknik Universitas Mataram
Jtn. Majapahit No.62 Mataram Nusa Tenggara Barat Kode Pos: 83125
Teip. (0370) 636087;636126; ext 128 Fax (0370) 636087
:
ABSTRAK
caper ini menyajikan flukuasitekanan dan aliran batik di dalam saturan tunggal pada alira.n air
mendidih dan- pengaruh pendidihan pada upstream loop terhada-P flaktuasi tekanan. Saluran
iunggalfersebuf tiftuat dai tembaga dengan diameter hidtolik 619 pm 97ry 9a.1ian0
40 mm'
uniik menguXur fluktuasi tekanan Ai aatam saluran, empat transducer PCC24 di pasang pada
saluran aingan jarak antar sensor I mm. Dua sensor tekanan iuga dipasang pada sisi
nasukan din ketuaran. Atiran batik di observasi dengan metode perbedaan tekanan. Jika
petuedaan tekanan bemilai negatif, ada kemungkinan aliran balk sesaaf teriadi. Hasil penelitian
nenunjukan hahwa fluktuasi-tekanan dan aliran batik disebabkan oleh aktivitas gelembung
;,rng *ur"ul, tumbuh dan meninggalkan saluran secara peiodik. Pendidihan di bagian
'ge,iipaan
sebetum seksi uji dapat-ienyebabkan aliran tidak stabil. Aliran balik dapat terjadi
ketika gelembung membaigkitkan tekaian sesaaf yang lebih besar dari pada tekanan di stst
masukan.
Kabkunci: saluran mikro, ftuffiuasi tekanan, aliran balik dan kerugian tekanan.
ABSIRACT
This paper presenfs pressure fluctuation and flow reversal in a metallic single channel duing
flow
'boiling
of de-ionized water and effecfs of boiling in the upstream loop on pressure
ffuctuations. The channel was made of a copper with a hydraulic diameter of 619 pm and a
6ngtn of 40 mm. To measure pressure fluctuations inside the channel, four inexpensive
dtff-erential pressure fransducers PCC24 were inserted into the channel with an inter'axial
disfance of I mm. Two pressurc sensors were also mounted on the channel, but they were in
the intet and outtet plenums. The two pressure sensors were used for measuring inlet and outlet
pressures. A flow reversal was observed using a pressure difference method. When a pressure
difference between two pressure tappings has a negative value, there is a possibility that a
temporary flow reversaloccurs. fnd resutts showed ihat prcssure ftuctuation and flow reversal
were due to activities of bubble which was appeaing, growing, departing and leaving from the
channel periodicatty. Boiling in the upstream loop could cause an unstable flow. The flow
reversal could occur when the bubbte generated a temporary pressure which was bigger than
the inlet prcssure.
Keyword: microchannel, pressure fluctuation, flow reversal and pressure drop.
106

5. llirmonto..........
Penguruh pedidihon
Di l/pstreon Loop
INTRODUCTION
pressure
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mass flux, r.,";,,133 - ,"rv"rriiJrl J:r':: ;:X,fi.ft
becomins more susceptibre to
system porl-;io''ll 9-perating conditior
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[li++ITilr,,tl:'*rm"ff,,ll# :r:'* :*#"}j,,**],1';6':*"rupotnt. They also ohsi^^;'".I:'.'
L11 oolllllQ reversed n"*'rll',1]tiluu[lon teading to a
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tn upstream i"r.J.I^::ly:l generation at the
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the upstrearn flov
oscillations generat
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1,07
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6. --.l-E -erqt( REXIyASA, Volurne 14 No 2 Desember 2013
:-oesec trte superheated liquid released its
=r€. ener(ry to vapour phase through a
1r-ale bubble interface during short time.
::T€ffior€, an increased sharp pressure in
:€ .€pour caused the fluid traveling in both
l:..:st'eam and upstream directions.
From open literature above, in
7'e.al. pressure fluctuation and flow
-=,ei'sal are due to activities of bubble
3-arr$ inside the channel. However, there is
-?- nteraction or a relationship between
:r?ssure fluctuation-flow reversal and an
-:stream compressibility. The upstream
=rnpressibility
may influence or support the
:-essure fluctuation and flow reversal, in
:errns of magnitude and live time. ln this
;aper. author presents differences between
)ressure fluctuations and flow reversals
'esutted in the experiments with boiling in
:1e upstream loop (case A) and without
rciling in the upstream loop (case B). The
:olective of this work is to know the effects
cf boiling in' the upstream loop on the
pressure fluctuation and flow reversal.
Nomenclature:
: area
: channel length
: pressure
; power from power supply.
: useful heat.
: heat loss to the sunoundings.
: heat flux
difference
Subscript:
ht : heated
1,2,3,4 : location measured from the inlet.
(8mm, 16mm,24mm and 32mm)
in : inlet
out : outlet
EXPERIMENTAL SET UP AND
PROCEDURES
The experimentalfacility or flow loop
is shown in Fig. 1. The loop consists of a
main boiler tank, gear pump, Coriolis
flowmeter, rotameter, two preheaters, and a
test module (test section).
Deionized water with a PH of 6.8
was used as the working fluid and drawn
from the main boiler and flowed through out
the loop. To remove any particles in the
working fluid, two filters (1 mm and 1 pm)
were fitted to the loop. The temperatures of
working fluid were measured in the inlet and
outlet plenums of microchannel using K type
thermocouples with a seated diameter of 0.5
mm and a length of 150 mm. A Coriolis
flowmeter with an uncertainty of t0.6 g/min
was installed in the loop and used to
rneasure the mass flow rate.
All thermocouples were calibrated
using a cpnstant temperature bath against a
platinum resistance precision thermometer
with an accuracy of 0.025 K. The uncertainty
of thermocouples was t0.2 K.
All local pressures were measured
using inexpensive pressure transducers
model PCC24 calibrated against a
deadweight tester with an uncertainty of !0.2
kPa.
Lf
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q
9los
q
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=!5 I_J jj
Figure 1, Schematic of e
&,n
xperimental fadlitY
IJ
Figure Z, Test section construction
#ff',',ffi:;$T,l#ifr*
I. fhrnrnocorgr
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8. Jrrml Teknik REKAyASA, Volume 14 No 2 Des€rnber 2013
DATA REDUCTION
Parameters used in the data
reduction are summarized in this section.
Total power supplied to the channel is noted
as P* and given by
P. =VI (1)
where Z is the voltage and ,I is the current.
Total heat flux, qn is calculated as follows:
Q=P,-Qw"
tn =(z.H +w)t
(2)
(3)
(4)
(5)
t
tr
€
, Q lt-Quu
' Ah, QH +W )L
where 4 is the net power (net heat), F/ is
the channel deplh, W is the channel weight,
Z is the channel length and lr, is the heat
transfer area. Heat loss (Q,",,) was
determined from single-phase experirnents
using energy balance and approximately
6.8% of net heat. Therefore, Eq. (4) can be
rearranged as
,,- Q - 0.932V1-
' A^, (z.n +w)L
Pressure droP is the difference
between inlet pressure and outlet pressure
and expressed as:
LP = P,n - Po* (6)
where pi, and poa are measured intet and
outlet pressures. However, pressures in the
inlet and outlet channel ends were not
known since there was no pressure sensor
at the end of upstream and downstrearn of
the channel. Pressure drop is used for
predicting the flow reversal in this study.
When the value of Pressure droP is
negative, it indicates that in the channel
there is a temporary flow reversal or
reversed flow, Chang et al. (2007). The
reveresed flow between each pressure
sensor inside the channel can be predicted
using a difference pressure value between
each sensor as given bY
Mt=pr-pz (7)
Lp, = Pt - Pt (8)
Lp-, = Pt - Pc (9)
where p1, Pz, Ps, pa w€re measured directly.
ln this work, there are two cases that are
examined: (1) flow boiling with boiling in the
preheater/upstream loop (case A) and (2)
flow boiling without boiling in the upstream
loop (case B).
RESULTS AND DISGUSSION
As reported by Zu et al. (2009), flow
reversal can only happen when there is a
compressible volume in the upstream loop.
Figure 3 depicts that pressure drop
fluctuation for case A is bigger than that for
case B. However, a flow reversal does
happens regularly for case A, but
occasionally for case B. This indicates that
the effect of boiling in the upstream loop is
significant. Nevertheless, without boiling in
the upstream looP, see case B' an
occasionally and temporary flow reversal
occurs.
-
G = 1S60 kgftnk, Ii * BAC , y = {21 ft{ttlrrf, Case A
-
G - 1068 kgtmrc, ?i - E8'c , { - Azl kllll/m", case B
Figure 3. Pressure drop fluctuation wlth and without bolllng in the up6tresm loop
110

9. l
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P"rgo"uh penddhor
Di Llpstream Loop................
=8:ilfftfl,H%
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1.1,7

10. --.rnal Teknik REKAyASA, Volume lrt No 2 Desernber 2013
Flgure 6. Efiecr of hest flux oo prersure drop fluctuation
urithout boiling h the prsheaer.
This might be due to existing trapped gas or
another upstream compressible volume
source. The maximum pressure drop
fluctuation amplitude (peak to peak) for case
A is around 10 kPa, while for case B is
around 8.4 kPa. The minimum value of -2.2
kPa is obtained for case A and -0.4 kPa for
case B. Hence, the biggest fluctuation is
observed for case A in which boiling in the
upstream loop presents. The different values
of pressure fluctuation for case A and B are
due to the boiling in the preheater. Thus,
boiling in the upstream loop affects pressure
and pressure drop fluctuations.
What does happen in single-phase
flow when boiling in the upstream loop
exists? Figure 4 indicates that pressure drop
fluctuation for both cases is small and the
difference of pressure fluctuation for both
cases is not big. lt is around 1.5 kPa (peak
to peak). Hence, the influence of boiling in
the upstream loop for single-phase flow is
not significant. However, at a low mass flux,
the effect of boiling in the upstream loop is
significant. Figure 5 shows the effect of
boiling in the upstream loop at a low mass
flux. For case A, the amplitude of pressure
drop is approximately 1.75 kPa, whilst for
case B is around 1 kPa. Thus, boiling in the
upstream loop is not suitable to demonstrate
the effect of upstream compressibility,
especially at a low mass flux,
Figure 6 presents the effect of heat
flux on pressure drop fluctuation at the same
mass flux without boiling in the preheater. At
a low heat flux, see Fig. 6a, a flow reversal
was observed, it was indicated by a negative
value of pressure drop. This was due to near
the onset of flow boiling and a low pressure
drop. Near the onset of flow boiling, less
bubble nucleation was generated. This
created a temporary/periodically boiling with
a high pressure build up. This was also
affected by the fact that at low heat flux, the
pressure drop generated was still low. As a
result, the inlet pressure was low and could
be defeated by bubble pressures inside the
channel during boiling. At a high heat flux,
see Fig. 6b, a flow reversal was not
detected. This was owing to a high pressure
dropfinlet pressure. Moreover, at a high heat
flux, there were many bubbles generated
and continue boiling occurred with high
frequencies. Therefore, an intermittent flow
(two-phase flow and liquid flow) did not
occur. lf it was guessed that the upstream
G = 440 kg/rnr*, Ii = 88"C, g'= 20S klll/lmr
G - 44S kg/mk, I' - 8S[, q" : $30 kl/Vlnii
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11. 'wrmonfo"""""
pengnrrh
Feaddhor Dr r,lpstream Loop-...............
ff[ffiHi"g"'i1,-n?],.P''st (because the
a*r,.,t",i, ,[:; j|",XJlijJl:?g:_,1_
11J W!*,1 heat sink,_tnt J Heat
volume was
From Figs. .,Hi";:*i"iii! fiTffi#e Gedur,#:t,",il,.]|,i,::ipp-zbzo-zoeb "''
1::i:rfu:fiiiru:nr"iiffi{[::i 'ffiiwl'li;;i,i,;jxf,,n","ii irtiii"rl^"?I
t9'"ttalbut it is oeriJJJj tu,ehar.ret"""o "i[r,
td *piiiriljTrti'-e-
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'",".."i. no*"rJi **p*u,b,,oy ,n{"' intet
nigt
-
t6,i"iIji.?i:t:Y'9 droP nuctui
f*t Hi*ii.iil!}f,#,ffi'1::*?'"*.nl!iffir:r;':!j;;,#i"
coNclussroN E;i:',rr',!r,,
uo*,rr{ Parattet
ffi{r-r-'fli}l:" g*#,':iilf ."ff ,",.,",itiffi;";;;
m" ; ;il,*laoeoroxyiJr'Y
a sro9ro microchspnsr I^'^r':!:-, .A unitoil"timperature
diameter or'uft'.1tu"_"opper wfth a rrvorauiic 2:::^:,r!, .to, cooiiig' ii etectrcnic
o"
"on"rrili;Jil
rrom the anarysis it cai XE,:r,-!r.
J. H;;'"M;"'
1. Boiling in thr
. il*i*'ddii:,t$,r r** *rfi
.-.T
{;ff!:#Wr#[ir,r*
'
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P ts due to ouour" yy9*gnril![n^.uY ,.f!.!:'n in
4. Flow reversat
:*q,*::frr*,x:ffi*:*'#i
--ffid!#W
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votume is eu, W., i;Jfii
' gl[ti',lfl$Jfpui[:l,i** [!it"::;rri:' ir,{l#ifr,
A.KN.,,LEDGMENT suzuki, [:t#;:l;;f':,i'i, .!r';u-t rrll",
ffl*li]*'J['x**i{:#,h*, rx# _)__,WifW;l
;il:;;"'
"{i#t,!ir,# .. ..#;*!''m:-ttiautrproc. of twelf
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,^^, _:.
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5 | ,.l:r, c., 2oo7, Two_phase ftow in silicon ;f#T;:""::?n,rj,;,ii,l,*nstabi ty -
ior bonin{
-,11 "'; *, it{{# f,${ftri:iiti#1r.3
rn panret siricon miiic"nii,iili!,,n
Jiri

12. --r'-c -eknik REKAyASA, Volume 14 No 2 Desember 2013
different heat flux, lnt. J. Heat Mass
Transfer 47, pp. 3631 -3641.
:- , erU. G., Zhang, W., Li, e., Wang, B.,
2009. Seed bubble stabilizes ftow
and heat transfer in parattet
microchannels, lnt. J. Multiphase
Flow 35, pp. 773-790.
I-:-i i., Koo, J.M., Ashegi, M., Goodson,
K.E., Santiago, .,.G., 2OO2,
Measurement and modeling of two
phase flow in nnicrochannel with
nearly constant heat flux boundary
condition, J. Microelctromech, Syst.
11(1), pp. 72-17.
Zu, Y.Q., Gedupudi, S., yan, y.y.,
Karayiannis, T.G., Kenning, D.B.R.,
20t2, Numerical simulation and
experimental obseruation of
confined bubble growth during flow
boiling in a microchannel with a
rectangular cross secf,bn of hQh
aspect ratio, Proc. lnternational
ASME conference, lCNMM2009,
South Korea.
1',t4