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Oil Palm Multilayer Dielectric Model for Microwave Drying Technique

1 2 3

Kritsada Pongsuwan1 , Mitchai Chongcheawchamnan2 and Chakrit tongurai 3

(Exocarp) (Mesocarp) (Shell) (Kernel) (Homogeneous) COMSOL 2.45 160, 320, 480 800

ABSTRACT

This paper presents a multilayer dielectric model for oil palm fruit for microwave heating to predict the temperature characteristic. The model under homogeneous assumption of is oil palm species Tenera developed as four physical layers which are exocarp, mesocarp, shell and kernel. The proposed dielectric model is implemented to simulate microwave drying of a palm fruit with COMSOL Multiphysics software. Several experiments on microwave heating at 2.45 GHz for four different power levels (160, 320, 480, 800 W) confirm that the model can predict the temperature characteristic of mesocarp accurately. It is the authors belief that the proposed model should be very useful to microwave drying application for oil palm fruit. Key Words: microwave technique, oil palm fruit, dielectric E-mail address:[email protected]

1,2 . . 90112 1,2 Computer Engineering Department, Prince of Songkla University, Hatyai, Songkha 90112 3 . . 90112 3 Chemical Engineering Department, Prince of Songkla University, Hatyai, Songkha 90112

( , 2546) 1 ( , 2553) 2 ( , 2528)

(Porous media) Sukaribin and Khalid (2009) 2 (kW) 10 440 W 520 W 2 kW ( , 2551)

(Datta, 2006) COMSOL

2.45 GHz 4

8 Figure 1 ( , 2528)

Figure 1 Oil palm specied tenera

Table1 Dielectrics properties of oil palm on the frequency 2450 MHz

Table1 (Chow and Ma, 2007) 2450 MHz (Choi and Okos, 1986; Narv ez et al., 2008) Figure 1( , 2528)

(1)

(1)

(2)

Kopelmen (1966) (Homogeneous structure) (3)

Layer Dielectric Constant ( ) Loss Factor( ) Shell 5.1 1.8

Mesocarp 11.5 4.2 Kernel 11.7 5.8

(3)

(4)

(5)

(Maxwells Equations)

(6)

(V/m) (A/m) (S/m) (Relative Magnetic Permeability) (rad/s) (F/m) (Relative Dielectric Constant)

(7)

(8), (9)

(8) (9)

3

(10)

(11)

(K) (s) (J/ (kg K))

(kg/m3) (W/ (m K)) (W/m3) T0

(12) K (13)

3 (6) - (13) COMSOL Multiphysics LG MS2349HK 160 W, 320 W, 480 W 800W 485x385x280 mm. Figure 2

Figure 2 FEM mesh structure with palm fruit. Figure 3 Microwave heating system.

Figure 2 92

Microwave Oven

Electronic balance

Palm fruit

24 43.32(1.17) mm. 30.32 (1.15) mm. 17.37 (1.4) g 30% 160 W 8 3 320 W 480 W 800 W 3 3 1 2 Figure 4

Figure 4 Position temperatures inside the palm fruit.

Figure 5

4 160,320,480 800 W (11)

160 W, 320 W, 480 W 800 W 0.95-0.99 160 W 2 (0.68)

Position 1

Position 1

Position 2 Position 2

(A) Position 1 (B) Position 2

Figure 5 Comparison between simulated and measured of temperatures

(SEC)

(R.B.S.C)

0

20

40

60

80

100

120

140

0 1 2 3 4 5 6 7 8

Tem

pe

ratu

re(d

eg

C)

Time(min)

Position 1

Simulation 160W Simulation 320W


Equipment 160W Equipment 320W


0

20

40

60

80

100

120

140

0 1 2 3 4 5 6 7 8

Tem

pe

ratu

re(d

eg

C)

Time(min)

Position 2





, . 2551.

, .382-387. 22. .

. 2546. . 1

, . . 2528. :.

. . 2553. . .

:http://it.doa.go.th/palm/linkTechnical/efficiency.html, 26 2553. Choi, Y. and M.R. Okos. 1986. Effects of temperature and composition on the thermal

properties of foods, pp. 93101. In Transport Phenomenon, L. Maguer and P. Jelen., eds. Food Engineering and Process Applications. Elsevier, New York.

Chow, M. C. and A. N. Ma. 2007. Processing of fresh palm fruits using microwaves, Journal

of Microwave Power and Electromagnetic Energy 40 (3): 165-173. Datta, A. K. 2006. Porous media approaches to studying simultaneous heat and mass transfer

in food processes. I: Problem formulations. Journal of Food Engineering :80-95. Kopelman, I. J. 1966. Transient heat transfer and thermal properties in food systems. Ph.D.

Thesis, Michigan State University. Narv ez, P. C., S. M. Rinc n, L. Z. Casta eda and F. J. S nchez. 2008. Determination of some

physical and transport properties of palm oil and of its methyl esters. Latin American applied research 38 (1): 1-6.

Sukaribin, N. and K. Khalid. 2009. Effectiveness of sterilisation of oil palm bunch using microwave technology. Industrial Crops and Products 30 (2): 179-183.

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