Numerical analysis of fractal fins with different aspect ratios to enhance phase change material melting heat transfer

doi:10.19799/j.cnki.2095-4239.2020.0343

Abstract

Abstract:

A fractal phase change heat exchanger model was established to study the law of enhanced phase change heat transfer by fractal fins on the basis of phase change heat transfer theory and fractal theory, and the enthalpy-porosity method was used to simulate phase change material (PCM) melting and heat transfer in the fractal fin heat exchanger. The influence of the radial length of the fractal fins, the diameter of the heat exchange pipe, and their ratio on the melting heat transfer of PCM is analyzed. The results show that when Fo < 0.02, the PCM melting rate decreases with the increase in the aspect ratio; when Fo > 0.02, the PCM melting rate increases with the aspect ratio and finally stabilizes. At the same dimensionless time, the uniformity of the PCM temperature distribution increases as the aspect ratio increases. At the initial moment, the heat flux decreases with the increase in the aspect ratio; in the late melting stage, the heat flux increases with the increase in the aspect ratio and maintains a relatively high and stable level over time. During PCM melting, the best ratio between the radial length of the fractal fins and the heat exchanger tube diameter is 12; that is, when the heat exchange tube diameter is 10 mm, the best radial length of the fractal fins is 120 mm. This provides a theoretical basis for the structural design of fractal phase change energy storage.

Key words: fractal fin, phase change material, numerical analysis, melting heat transfer

CLC Number:

TK 02

Xinmei LUO, Jia'an GU. Numerical analysis of fractal fins with different aspect ratios to enhance phase change material melting heat transfer[J]. Energy Storage Science and Technology, 2021, 10(2): 523-533.

Figures/Tables 20

Fig. 1

Fig. 2

Fig. 3

Table 1

Physical model parameters"

类型	模型1	模型2	模型3	模型4	模型5	模型6	模型7
$R e / m m$	30	50	70	90	110	130	150
$R i / m m$	10	10	10	10	10	10	10
$γ = L r a d / R i$	2	4	6	8	10	12	14
$L 0 / m m$	10	20	30	40	50	60	70
$L 1 / m m$	0.707	14.14	21.21	28.28	35.36	42.43	49.5
$L 2 / m m$	0.5	10	15	20	25	30	35
$D 0 / m m$	0.7	1.04	1.4	1.74	2.09	2.44	2.80
$D 1 / m m$	0.5	0.74	1	1.23	1.48	1.73	1.97
$D 2 / m m$	0.35	0.52	0.7	0.87	1.05	1.22	1.40
$A f i n / m 2$	0.088	0.177	0.265	0.353	0.441	0.530	0.618

Table 1

Table 2

Material properties"

材料

密度

ρ/kg·m^-3

比热容

C_p/J·(kg·K)^-1

热导率

λ/W·(m·K)^-1

相变潜热

$L a$ /J·kg^-1

相变温度

$T p / K$

月桂酸

（C₁₂H₂₄O₂）

1000

2150(固相)

0.15(固相)

178000

314.15(固相)

2203(液相)

0.22(液相)

351.15(液相)

铝

2719

871

202.4

Table 2

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Fig. 8

Fig. 9

Fig. 10

Fig. 11

Fig. 12

Fig. 13

Fig. 14

Fig. 15

Fig. 16

Fig. 17

Fig. 18

References 19

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