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SCIENCE CHINA Technological Sciences, Volume 61 , Issue 11 : 1732-1744(2018) https://doi.org/10.1007/s11431-018-9252-9

Thermal design of a novel heat sink cooled by natural convection with phase transition in the series loop

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  • ReceivedFeb 27, 2018
  • AcceptedApr 9, 2018
  • PublishedJun 14, 2018

Abstract

In this paper, a novel heat sink, cooled by natural convection, with phase transition in the circulation loop was designed, and the heat sink was applied on averaging temperature and cooling the electronic equipment. The working fluid in the heat sink was driven by the capillary pump. Numerical simulations were performed, to study the heat transfer performance of two systems with various heating power, filling ratios and refrigerants. The influences of above elements on temperature uniformity of two systems were also studied and the thermal performances of two systems were compared. The volume of fluid (VOF) model was utilized to simulate fluid motion in ANSYS FLUENT. The simulation results indicate that the temperature differences of the system comprising two substrates (system 1) are very small under suitable filling ratio conditions, and the thermal performance of system 1 is preferable to the system comprising one substrate (system 2) at the same volume. Besides, the simulation results also show that the system using R245fa possesses excellent temperature uniformity for the same filling ratio and heating power. Finally, the experiments were investigated and the experimental results proved the correctness of the theoretical model.


Funded by

the National Natural Science Foundation of China(GrantNo.51225602)


Acknowledgment

This work was supported by the National Natural Science Foundation of China (Grant No. 51225602).


References

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  • Figure 1

    (Color online) Structure of cooling system 1 (unit: mm). (a) Horizontal direction; (b) vertical orientation.

  • Figure 2

    Sectional view of flow passages and fins (unit: mm).

  • Figure 3

    The cross-section views of the capillary pump (unit: mm). (a) Radial view; (b) axial view.

  • Figure 4

    (Color online) The circulation flow of working fluid in the looped flow passages of system 1.

  • Figure 5

    (Color online) Structure of cooling system 2 (unit: mm). (a) Horizontal direction; (b) vertical orientation.

  • Figure 6

    (Color online) The circulation flow of working fluid in the looped flow passages of system 2.

  • Figure 7

    (Color online) The input power of system.

  • Figure 8

    (Color online) The experimental device.

  • Figure 9

    The thermocouple locations.

  • Figure 10

    (Color online) Contours of temperature of substrate. (a) Evaporation substrate; (b) condensation substrate.

  • Figure 11

    (Color online) Contours of phase volume fraction and velocity vector. (a) System 1; (b) system 2.

  • Figure 12

    (Color online) Maximum temperature difference of (a) evaporation substrate and (b) condensation substrate vs heating power.

  • Figure 13

    (Color online) Average temperature difference of two substrates vs heating power.

  • Figure 14

    (Color online) Maximum temperature difference of the substrate vs filling ratios for R245fa, R1233zd and R134a.

  • Figure 15

    (Color online) Maximum temperature of system 2 vs filling ratios for R245fa, R1233zd and R134a.

  • Figure 16

    (Color online) Maximum temperature difference of the substrate vs heating power.

  • Figure 17

    (Color online) Maximum temperature of system 1 and system 2 vs heating power (filling ratio 50%).

  • Figure 18

    (Color online) Maximum temperature difference of the substrate in system 1 and system 2 vs heating power (filling ratio 50%).

  • Table 1   Table 1Structure parameters of system 1

    Parameters

    Value (mm)

    Length of substrate

    700

    Width of substrate

    370

    Thickness of substrate

    2

    Spacing between two substrates

    85

    Length of right channel

    610

    Length of left channel

    670

    Height of channel

    8

    Width of channel

    2

    Spacing between flow passages

    17

    Length of right fin

    580

    Length of left fin

    640

    Height of fin

    40

    Thickness of fin

    0.5

    Internal spacing of fin

    10

    External spacing of fin

    12

    Diameter of capillary pump

    40

    Length of capillary wick

    210

    Diameter of capillary wick

    30

    Diameter of liquid passage

    12

    Height of vapor passage

    3

  • Table 2   Table 2The heating power

    Total power (W)

    Q1 (W)

    Q2 (W)

    Q3 (W)

    Q4 (W)

    500

    150

    135

    110

    105

    400

    120

    108

    88

    84

    300

    90

    81

    66

    63

    200

    60

    54

    44

    42

    100

    30

    27

    22

    21

  • Table 3   Table 3The convective heat transfer coefficients

    Qin(W)

    System 1

    System 2

    hlf,in

    hlf,out

    hrf,in

    hrf,out

    hs

    hf,in

    hf,out

    hs

    100

    0.97

    1.91

    1.08

    2.06

    2.65

    1.33

    2.37

    2.82

    200

    1.38

    2.42

    1.52

    2.57

    2.93

    1.82

    2.89

    3.11

    300

    1.69

    2.76

    1.86

    2.92

    3.14

    2.14

    3.20

    3.30

    400

    1.98

    3.04

    2.15

    3.20

    3.30

    2.42

    3.46

    3.46

    500

    2.11

    3.17

    2.29

    3.36

    3.38

    2.61

    3.63

    3.56

  • Table 4   Table 4Grid independent check

    Mesh size(cells)

    System 1

    System 2

    1656589

    919863

    581983

    1143527

    751847

    445805

    ΔTs,rs (K)

    3.43

    3.94

    3.55

    7.63

    8.10

    8.42

    ΔTs,ls (K)

    1.66

    2.06

    1.8

     

    ΔTs,ds (K)

    0.45

    0.55

    0.51

    Tmax (K)

    362.69

    363.14

    362.96

    375.40

    375.06

    374.75

  • Table 5   Table 5Maximum temperature difference of substrate and maximum temperature in system 1

    R134a

    R1233zd

    R245fa

    10%

    30%

    60%

    10%

    30%

    60%

    10%

    30%

    60%

    ΔTs,rs (K)

    6.44

    6.13

    5.82

    5.02

    4.20

    4.07

    4.88

    3.23

    3.03

    ΔTs,ls (K)

    4.19

    3.79

    3.53

    3.02

    2.17

    2.08

    2.93

    1.70

    1.59

    ΔTs,ds (K)

    2.07

    1.71

    1.59

    1.53

    1.12

    1.06

    1.27

    0.47

    0.44

    Tmax (K)

    359.46

    358.92

    358.48

    358.23

    357.72

    357.43

    358.22

    356.55

    356.37

  • Table 6   Table 6Comparison between experimental and simulation data of system 1 for heat load 400 W

    Filling ratio (%)

    T¯e,ls(K)

    T¯s,ls(K)

    T¯e,rs(K)

    T¯s,rs(K)

    ΔTe,ls(K)

    ΔTs,ls(K)

    ΔTe,rs(K)

    ΔTs,rs(K)

    ΔTe,ds(K)

    ΔTs,ds(K)

    40

    327.50

    330.75

    331.06

    330.97

    3.97

    1.71

    7.53

    3.22

    3.56

    0.22

    50

    327.71

    330.76

    330.18

    330.98

    3.26

    1.72

    5.50

    3.18

    2.47

    0.22

    60

    327.59

    330.80

    330.17

    331.00

    3.20

    1.59

    5.10

    3.03

    2.58

    0.20

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