A study on the optimum condition of electric snow melting and deicing system for the anti-freezing testing road

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.

, .

,

, J. Kor. Soc. Fish. Tech., 44(4), 362 369, 2008

DOI:10.3796/KSFT.2008.44.4.362

A study on the optimum condition of electric snow melting and deicing system for the anti-freezing testing road

Kyu-Il H AN *

Division of Mechanical Engineering, Pukyong National University, Busan 608-739, Korea

The snow melting system by electric heating wires which is adopted in this research is a part of road facilities to keep surface temperature of the road higher than freezing point of water for melting the snow accumulated on it. The electric heating wires are buried under paved road at a certain depth and operated automatically and manually. Design theory, amount of heating, and installation standard vary according to economic situation, weather condition, installation place and each country applying the system. A main purpose of this study is figuring out the appropriate range of required heat capacity and installation depth and pitch for solving snowdrifts and freezing problems with minimum electric power consumption. This study was performed under the ambient air temperature( 2 C, 5 C), the pitches of the electric heating wires(200 mm, 300 mm), heating value(250 W/m

²

, 300 W/m

²

, 350 W/m

²

).

Key words : Electric heating cable, Anti-freezing, Light weight electric traction system, Simulation

* Corresponding author: [email protected], Tel: 82-51-629-6194, Fax: 82-51-629-6188

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250 W/m

²

, 300 W/m

²

,

350 W/m

²

.

10mm .

Fig. 1. Schematic diagram of experimental apparatus.

Table 1. The average value of temperature and wind velocity

2004 2005 2006 Average Average

0.8 2.8 0.0 1.2

temperature( C) Average

wind velocity 3.7 3.5 3.6 3.6

(m/s)

Constant temperature room

Electric heating cable

Data logger Powermeter

V A W

Slidacs Concrete

sample Controller

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3 2 C

5 C . Fig. 3 4

300 W/m

²

, 300 mm,

. (0 C)

2 C 20 30

, .

Fig. 5 6 300 W/m

²

, 5

C, 300 mm ,

. (a) Pitch of electric heating cable(300mm) (b) Pitch of electric heating cable(200mm) Fig. 2. A location of thermocouples.

Fig. 3. Variation of surface temperature according to time( 2 C).

Fig. 4. Variation of surface temperature according to time ( 5 C).

10 8 6 4 2 0 -2 -4 -6

8 6 4 2 0 -2 -4 -6

Temperature( C) Temperature( C)

Time(hour)

0 2 4 6 8

Fig. 5. Variation of surface temperature according to time(no ice condition).

8 6 4 2 0 -2 -4 -6

Temperature( C)

Time(hour)

0 2 4 6 8

A B C D E F

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2 .

.

Fig. 7 8 300 W/m

²

,

2 C,

,

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200 mm .

300 mm

200 mm 30 40

. 200 mm

300 mm 50 mm

,

.

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.

4 (A, B, D, E)

. 4 ,

.

200 mm 10 30

. 200

mm

,

. 300 mm

. Fig. 6. Variation of surface temperature according to

time (ice condition).

8 6 4 2 0 -2 -4 -6 -8

Temperature( C)

Time(hour)

0 2 4 6 8 10 12 14 16 18 20

Fig. 7. Variation of temperature according to depth(pitch of heating cable : 300mm).

10 8 6 4 2 0 -2 -4

Temperature( C)

Time(hour)

0 2 4 6 8

A B C D E F

0mm(surface) 50mm 120mm 160mm 190mm 300mm(bottom)

Fig. 8. Variation of temperature according to depth(pitch of heating cable : 200mm).

10 8 6 4 2 0 -2 -4

Temperature( C)

Time(hour)

0 1 2 3 4 5 6 7

0mm(surface) 50mm 120mm 160mm 190mm 300mm(bottom)

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∂ ∂T ∂ ∂T ∂ ∂T ∂T

___ _∂x ( ^k___ _∂x ) ^___ _∂y ( ^k___ _∂y ) ^___ _∂z ( ^k___ _∂z ) ^ρc

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1 , x, y, z 2

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.

250 W/m

²

, 300 W/m

²

, 350 W/m

²

. , 600

mm 300 mm

,

.

. Table 3 4

.

Fluent . Fig. 9 11

300 W/m2, 2 C,

300mm .

. Table 2. A comparison of melting point reaching time Table 3. Material properties

Material ρ c

p

k

(kg/m

³

) (J/kg K) (W/m K)

concrete 2700 1050 1.2

copper 8978 381 387.6

Table 4. Test conditions

ambient temperature( C) 2, 5 convection heat transfer

coefficient on surface(W/m

²

K) 14.4

heating value(W/m

²

) 250, 300, 350 Width

(mm) 200 300

Ambient air temperature Heating value ( C)

(W/m

²

) 250

300

350 123min 237min 70min 160min

45min 123min

150min 255min 85min 183min

54min 166min

2 5 2 5 2 5

Fig. 9. Simulation interpretation diagram.

8

6

4

2

0

2 Temperature( C)

0 100 200 300 400 500 600 700 Time(min)

Simulation data Experiment data

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50 ,

100 0 C

, 600 .

,

.

,

.

300 W/m

²

, 300 mm ,

2 C 5 C

20 30 . 300 W/m

²

,

300 mm , 5

C

2 .

200 mm 300 mm

(0 C) 40

. 2 (C, F) A,

B, D, E ,

2 .

200 mm 300 mm

, 300

mm .

350 W/m

²

, 300 W/m

²

.

300 W/m

²

.

300 W/m

²

,

2 , 300 mm ,

.

2007

.(PK 2007 024)

Chapman, W.P, 1952. Design of snow melting system.

Fig. 10. 1 hour later from initial set temperature of 2 C.

Fig. 11. 10 hours later from initial set temperature of 2 C.

2.86e+02 2.85e+02 2.83e+02 2.82e+02 2.80e+02 2.79e+02 2.77e+02 2.76e+02 2.74e+02 2.73e+02 2.71e+02

2.95e+02 2.93e+02 2.91e+02 2.88e+02 2.86e+02 2.84e+02 2.81e+02 2.79e+02 2.77e+02 2.74e+02 2.72e+02

Y Z X Y Z X

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Heating and Ventilating, 88 92.

Chapman, W.P. and S. Katunich, 1956. Heat requirements of snow melting system. ASHRAE Transactions, 62 359.

Incropera, F.P. and D.P. Dewitt, 2007. Fundamentals of heat and mass transfer. John Willy, 70 73.

Lawrie, R,J., 1965. Electric snow melting systems. Electrical

Construction and Maintenance, pp. 125 129.

Nydahl, J.E., K. Pell and R. Lee, 1987. Bridge deck heating with ground-coupled heat pipes. ASHRAE Transaction, pp. 93.

Shin, H.J. and S.J. Seo, 1993. A study on the highway snow melting and deicing system using geothermal energy. Journal of KIIS, 8(4), 139 148.

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