()

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Boiling heat transfer enhancement for ammonia
using micro fabrication surface on plate evaporator(Effect of micro groove direction)
Hirofumi ARIMA*5, Nobuhiko MATSUO, Keita SHIGYOU,Akio OKAMOTO and Yasuyuki IKEGAMI*5 Institute of Ocean Energy, Saga University
1-48 Kubara-aza, Hirao, Yamashiro-machi, Imari-shi, Saga 849-4256, JapanThe experimental study has been performed for the heat transfer enhancement in ammonia on this newplate evaporator which treated the surface on the micro groove. The micro groove is depth of 30 micro meters
and width of 200 micro meters. The local boiling heat transfers were measured on the evaporator surface using
10-thermocouples inside evaporator. For comparison of the heat transfer characteristic of the evaporator, thelocal boiling heat transfer coefficient on a flat surface and two micro grooved surface which have vertical andhorizontal directions to ammonia flow, were measured in a range of mass flux (2 - 7.5 kg/m2 s), heat flux (10 20kW/m2), and saturation pressure (0.7 - 0.9 MPa).
The result shows that, the local boiling heat transfer coefficient increased with an increase mass flux,
averaged heat flux and vapor quality in all surface conditions. The heat transfer coefficient of horizontal andvertical micro grooved surface was larger than that of flat surface. Especially, the horizontal micro grooved
surface had best heat transfer coefficient. In case of low vapor quality which was in nucleate boiling region, theheat transfer coefficient of horizontal and vertical surfaces showed large increment from that of flat surface.
However, in case of high vapor quality which was added the slightly effect of convective boiling, the heattransfer of vertical surface showed small increment from that of flat surface though that of horizontal surface
showed large increment.
Key Words : Heat transfer enhancemnet, Ammonia, Plate heat exchanger, Micro grooved surface

1.
OTEC
30℃
(OTEC)
OTEC

30℃
25℃
OTEC

*
2010 7 31
*1
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E-mail: arima@ioes.saga-u.ac.jp(1)(2)

Djordjevic

(3)

(4)

(5)

(1) (2)

/

w
x

(3)

[m][-]

δ(4)/([m]90%)3.
Fig. 1

3 1
Djordjevic(8)(5)()
3OTEC

(6)

(7)

2kW

(8)

(7)

(8)

30µm
PROMASS 83A± 0.1%

10 ~ 40%(8)

FD-M, FD-P

± 1.6%
FP101

0 ~ 2MPa± 0.25%
KST61370mm220mm)

±1.5℃
PC

0.1oC

2.
G
hi
ifg
isat.liqkli
Psat
qav
rc
Ti
Tsat
Twall

Fig. 2[kg/m2s][W/m2K]

SUS304
SUS304[J/kg]((2mm)[J/kg][J/kg]

5[W/mK][m]

240mm,

[Pa]

10K

59mm
100V-1050W

2[W/m ]
[m]
[℃]
[℃]
[℃]

100mm
150W

2250mm

20mm

Working fluid circuit

Cold water circuit
15T613PT

THot water circuit

P TTP T 14

TTT2T4PTT

1311PT

12T

910P

78165

1. Test plate (Evaporator) 2. Pre-heater 3. Condenser 4. Working fluid tank 5. Sub cooler 6. Electric heater
7. Cold water tank 8. Refrigerator 9. Hot water tank 10. Working fluid pump 11. Hot water pump 12. Cold water pump
13. Mass flow meter 14. Volumetric flow meter 15. Degassed valve 16. Release valve

Fig. 1 Schematic of experimental apparatus

7Heat transferplateSpacerFrame

Heaterblock

TC wells

Fig. 3(δ) 2 mm(w) 100mm

B

Fig. 2B

Fig. 4
T1,40

l1, T2

T2,l2

AA

l2

2

S1, S3: l2 = 5.02
S2: l2 = 5.01
5Fig. 2 Assembly of test plate

Fig. 3 Cross sectional view of test plate(A-A’ cross section of Fig. 2)

3

Ti Thin plateT −T
q=k 1 2l1

Ti base plate
Solder(1)

Twall

T wall

T2(1)

T1
l2 = 5.02

4 . 55

0. 4
l3

Twall = T2 −l1 = 40ql 2k(2)l3 = S1, S3: 0.07, S2: 0.06.

hTsat

Twall
Fig. 4 Configuration of thermocouples inside test plate(Detail of circle “B” area of Fig. 2)

h=3 2
Fig. 5q(Twall − Tsat )(3)

33(Ti)

Tsat

220mm,370mm

50mm

100mm

Psat

250mm
0.4mm

Ti

Ti

3.3.2

(a) ~ (c)

x()

Ti
Ti

(a) ~ (c)x=(a)(S1) :(b)(0.6 µmi − isat ,liq

(4)

i fg

S2) :
i(c)

(isat.liq

S3) :iFig. 6

P-PROPATH(9)(b), (c)TiFig. 6 (b)200µm,100µm,Table 1

3 430µm
0.6 µm

55 µm

3 3
3.3.1
qT2

l1ifg

Fig. 4T1
k42(8)

250(a)Ti thin flat surface

Ti base100

Ti thin grooved plate(b)
Ti baseTi thin grooved plate(c)
Ti base(i) General view(ii) Side viewFig. 5 Photographs of three test heat transfer plates(a) S1: Flat surface, (b) S2: Vertical grooved surface, (c) S3: Horizontal grooved surface

Table 1 Experimental Conditions

Working fluid
Plate surface
Plate substance
Mass flux G [kg/ m2s]
Average heat flux
qav [kW/ m2]
Saturation pressure
Psat [MPa]Fig. 6 Detail of S2 and S3 plate surface

5Pure ammonia
S1: Flat surface
S2: Vertical grooved surface
S3: Horizontal grooved surface
Titanium
2, 5, 7.5
10, 15, 20
0.7, 0.8, 0.9

4.
4 1

Fig. 7 (a)G=52(b)2

Average heat flux qav [W/m ]7.5 kg/m s
S1 ~ S3(x = 0.2)(x = 0.7)(10)(Psat = 0.7MPa)
G = 5 kg/m2s

Fig. 7 (a)

(10)

S1

2

G=5.0 kg/m s
20000 Psat=0.7MPahigh low
S1
S2
S310000

Pool boiling (0.7MPa)
Pool boilingon Porous (0.7MPa)

low : quality x= 0.2
high : quality x= 0.700S1

1[ by Arima et al.

2(10)]

34∆Tsat [K]qav =10kW/m2(a) G = 5 kg/m2s
2

S3Average heat flux qav [W/m ]S2

S30.5K
S2

S3
S1

qav = 10kW/m2

S1 ~ S3

2

G=7.5 kg/m s
20000 Psat=0.7MPahigh low
S1S2
S3

10000

Pool boiling (0.7MPa)
Pool boilingon Porous (0.7MPa)

low : quality x= 0.2
high : quality x= 0.7000.2K[ by Arima et al. (10) ]1234∆Tsat [K]2

qav > 15kW/m
S1, S2, S3(b) G = 7.5 kg/m2s
Fig. 7 Boiling curve at different plate surfaces

Fig. 84 2(a)S1(qav = 10 kW/m2)(b)(Psat = 0.7 MPa)

Fig. 8 (a)Fig. 8 (a)G = 7.5 kg/m2s

Fig. 7 (b)S2G=2

S1 ~ S35 kg/m2s

30%
G=5Fig. 7 (a)G(b)

7.5 kg/m2s
Fig. 8 (b)57.5(3)

G = 7.5 ~ 15 kg/m2s
G = 2 kg/m2s

6S33 ~ 11 mm/s

Local heat transfer coefficient
2hloc [W/(m K)]

rc(11)
rc = 2 µm (Psat = 0.7MPa, ∆Tsat = 1℃)

10000

S10.6µm
S22G[kg/m s]
2.05.07.5

5000

S3200µm

30µm

rc

2

qav=10kW/m
Psat=0.7MPa
000.2

0.4
0.6
0.8
Vapor quality x [-]

S2
S2

1S3
S3Fig. 6

S2

S3(a) S2

Local heat transfer coefficient
2hloc [W/(m K)]

S3

Local heat transfer coefficient
2hloc [W/(m K)]

10000
2G[kg/m s]
2.05.07.5

5000

100002

qav=10kW/m
Psat=0.7MPa
000.2

0.4
0.6
0.8
Vapor quality x [-](S3/S1) 10%(S2/S1) 2%(S3/S1) 16%(S2/S1) 11%

S1
S2
S35000

1

2

G=5 kg/m s 2
qav=20kW/m
Psat=0.7MPa

000.2(b) S30.4
0.6
0.8
Vapor quality x [-]1Fig. 8 Comparison between boiling heat transfer coefficient at(a) G = 5 kg/m2s

Fig. 9 (a)4 3(qav = 20 kW/m2)(b)(Psat = 0.7 MPa)

10000

S1, S2, S3
Fig. 9 (a)(b)

Local heat transfer coefficient
2hloc [W/(m K)]

different mass fluxes on S2 and S3

G = 5 kg/m2s, Fig. 9(b)(x < 0.3)

S1

S212%, S3

16 ~22%S1S2S3(S3/S1) 22%

5000

7.5kg/m2s

Fig. 9 (a)(S3/S1) 10%(S2/S1) 0%(S2/S1) 12%2

G=7.5 kg/m s2
qav=20kW/m
Psat=0.7MPa

000.2

0.4
0.6
0.8
Vapor quality x [-]1(x > 0.3)
S1

S2(b) G = 7.5 kg/m2s

0 ~ 2%, S310%
S3Fig. 9 Comparison between boiling heat transfer coefficient for

S2plate S1, S2 and S37

S2S1S2OTEC

S3S2(1)

Kushibe M. et al., Trans. JSRAE, Vol. 22, No. 4 (2005) ,pp. 403-415 (in Japanese).
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5.

(4)

pp. 359-370.
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pp. 131 - 139 (in Japanese).
Djordjevic E. et al., Int. J. Heat Mass Trans., Vol. 51(2008), pp. 6235-6242.
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industrial publishing (in Japanese).
(7) Ikegami Y. et al., Proceedings of 37th National heattransfer symposium of Japan, Vol. 37, No. 3, (2000), pp.
825-826 (in Japanese).
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(9) P-Propath
http://www2.mech.nagasaki-u.ac.jp/PROPATH/p-propath.
html (2006.4).
(10) Arima H., et al., Thermal Science and Engineering, Vol. 9,No. 4, (2001), pp. 65-66(11) Griffith P. et al., Chem. Eng. Progress Symp. Series, Vol.
56, No. 30, (1960) , pp. 39 - 48.
(5)

(1)
(2)
(3)
(4)
G = 2 kg/m2s8