Experimental Study of Condensation on Micro Grooved Plates

Two-Phase Heat Transfer Laboratory

Texas A&M University

Experimental Study of Condensation on Micro Grooved Plates

R. Barron-jimenez, H. Y. Hu, G. P. PetersonDepartment of Mechanical Engineering




Overview

• Introduction• Experimental System

– Apparatus– Test Plates– Test Conditions

• Results– Overall Condensation Heat Transfer Coefficient– Condensate Removal

• Conclusions



Micro Grooves

Scientific Interest• Optimum geometry to

take advantage of the surface tension

• Effect of vapor shear during condensation

• Role of gravitational body force during condensation

Applications• Condensate removal

– Thin film• Retain liquid

– Enhance capillary pumping in micro heat pipes

Better understanding of the condensation phenomena



Experimental Apparatus

Rotameter

CondensateRemovalUnit

Direct -contactCondenser

Thermocouples

GroovedPlate

Observation WindowVapor Tunnel

Boiler

Cooling Base

Cooling Base

Heater

SuperHeater

Heater




Grooved Plate

Cooling PassagesCondensateRemoval

Unit

ObservationWindow

VaporTunnel Micro Grooves

Capillary Paper

Thermocouples

Thermocouples









Test Plates

L = 25.4 mm

H r

a aS W

I.D. 0 1 2 3 4 5 6W 0 0.41 0.41 0.33 0.63 0.67 0.69[º] 0 60 60 60 45 60 45

a 25.4 2.25 2.59 2.59 2.44 2.46 2.45S 0 0.95 1.79 1.47 1.17 1.13 1.11Hr 0 0.31 0.31 0.21 0.39 0.48 0.60n 0 16 10 12 12 12 12

Dh 0 0.20 0.20 0.14 0.21 0.32 0.33

Micro Grooves Geometry



Test Plates



Test Plates



Test Conditions

• Vapor velocity : 4.14±0.64 m/s

• Re (transition regime) : 3.474*103

• System pressure : 101.35 kPa

• Plate orientation : Horizontal

• Cooling Temperature : 20, 35, 50, or 65ºC



Test Conditions

20304050607080

Plate location [mm]

20

35

5065

Plate

temp

eratur

e [º

C]

13 44.75 76.5 108.25 137.20

T c [ºC]

Constant Plate Temperature Assumption



Results

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

30 40 50 60 70 80Plate temperature, T s [ºC]

0

0.14

0.21

0.32

0.33

h [kW

/m2 K]

D h [mm]

Overall Condensation Heat Transfer Coefficient

Plate 5 vs. 3 (W) : 1.75 and 2.9 times larger = 60º vs. 45º : 1.55 better

hmC (T T )

A (T T )p c,out c,in

s v s



Results

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

30 40 50 60 70 80Plate temperature [ºC]

0

0.14

0.21

0.32

0.33

h [kW

/m2 K]

D h [mm]

Overall Condensation Heat Transfer Coefficient

0

20

40

60

80

100

120

140

160

33.308 46.142 60.134 72.452Plate temperature [ºC]

0

0.2

0.2

0.14

0.21

0.32

0.33

Unce

rtaint

y [%

]0 0 0

11

1 1

2

2

2

23

3

3

3

4

4

4

45 5 5

56

66

6

Uh

100UC

Um

2 UT

2 U

T Th Cp

p

2

m2

T

c

2

T

v s

2

Average Uh: 52%



Results

Condensate Removal

Micro grooves in plate 5 are better than smooth surface

0.05

0.1

0.15

0.2

0.25

0.3

0.35

30 40 50 60 70 80Plate temperature [ºC]

00.20.2

0.140.210.320.33

Mea

n con

dens

ate re

mova

l rate

[gr/s

]D h [mm]



Conclusions

• Data is not conclusive. Further work is recommended

• Large micro grooves with 60º apex angles tend to work better (best performance: Plate 5)

• Tests conditions improve the micro grooves performance

• Micro grooves help to maintain a stable condensation pattern

• Eliminate “wall channel” effect and reduce heat losses



Questions?

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Documents

Experimental Study of Condensation on Micro Grooved Plates