Thermodynamic properties of drying process and water absorption of rice grains

Figures & data

Table 1. Mathematical models used to predict drying process of husk rice.

Tabla 1. Modelos matemáticos utilizados para pronosticar el proceso de secado de las cáscaras de arroz

Model name	Model
Two term (Henderson, 1974)		(2)
Logarithmic (Yagcioglu, Degirmencioglu, & Cagatay, 1999)		(3)
Modified Midilli (Ghazanfari, Emami, Tabil, & Panigrahi, 2006)		(4)
Page (Diamente & Munro, 1993)		(5)
Verma (Verma, Bucklin, Endan, & Wratten, 1985)		(6)

a, b, g, n are model parameters, dimensionless; k is drying rate, h⁻¹; t is drying time, h.

En los cuales: a, b, g, n son los parámetros de los modelos, sin dimensiones; k es la velocidad de secado, h⁻¹; t es el tiempo de secado, h.

Table 2. Statistical parameters of drying models for husk rice grain.

Tabla 2. Parámetros estadísticos de los modelos de secado de las cáscaras de granos de arroz.

Model	MRE (%)	SDE (% db)	R^2 (%)	Residual analysis
35°C
Two term	16.22	0.04	99.83	Random
Logarithmic	17.69	0.09	99.31	Biased
Modified Midilli	8.18	0.05	99.79	Random
Page	24.35	0.06	99.65	Biased
Verma	16.26	0.05	99.90	Random
45°C
Two term	19.14	0.06	99.58	Biased
Logarithmic	8.73	0.09	99.06	Biased
Modified Midilli	9.72	0.06	99.62	Random
Page	28.06	0.09	98.97	Biased
Verma	19.14	0.06	99.58	Biased
55°C
Two term	12.20	0.06	99.42	Biased
Logarithmic	9.87	0.11	98.22	Biased
Modified Midilli	5.19	0.04	99.81	Random
Page	18.44	0.10	98.57	Biased
Verma	12.20	0.06	99.58	Biased
65°C
Two term	7.53	0.04	99.66	Biased
Logarithmic	11.36	0.11	97.73	Biased
Modified Midilli	4.01	0.03	99.84	Random
Page	14.47	0.08	98.90	Biased
Verma	7.53	0.04	99.66	Biased
75°C
Two term	6.81	0.05	99.39	Biased
Logarithmic	9.56	0.13	95.75	Biased
Modified Midilli	6.49	0.04	99.54	Random
Page	12.23	0.09	97.96	Biased
Verma	6.81	0.05	99.39	Biased

Figure 1. Behavior of the residual distribution of modified Midilli model, in order to describe drying of husk rice (cv. Urucuia).

Figura 1. Comportamiento de la distribución residual del modelo Midilli modificado para describir el secado de las cáscaras de arroz (cv. Urucuia).

Table 3. Parameters of the modified Midilli model fitted to experimental data of husk rice drying, cv. Urucuia.

Tabla 3. Parámetros del modelo Midilli modificado utilizado con los datos experimentales del secado de las cáscaras de arroz, cv. Urucuia.

Temperature (ºC)	k	n	b
35	0.030485	0.781605	−0.000117
45	0.058121	0.695936	−0.000576
55	0.116606	0.560017	−0.001717
65	0.173321	0.544249	−0.001972
75	0.306872	0.440466	−0.005700

Figure 2. Husk rice drying curves at temperatures of 35°C, 45°C, 55°C, 65°C and 75°C.

Figura 2. Curvas de secado de las cáscaras de arroz a temperaturas de 35°C, 45°C, 55°C, 65°C y 75°C.

Table 4. Statistical parameters of Peleg model for water absorption by husk rice grain.

Tabla 4. Parámetros estadísticos del modelo Peleg de la absorción de agua de las cáscaras de granos de arroz.

Temperature (°C)	C1 (100 h kgms)kg^−1a	C2 (100 kgms)kg^−1a	MRE (%)	SDE (% db)	R^2 (%)	Residual analysis
35	3.998	7.422	1.02	0.01	99.80	Random
45	3.990	6.052	1.48	0.01	98.80	Random
55	3.981	4.420	1.71	0.02	99.28	Random
65	3.563	2.179	2.88	0.04	99.91	Random
75	3.427	0.887	7.48	0.15	98.49	Random

Figure 3. Curves of water absorption by the grains of paddy rice (cv. Urucuia) at temperatures of 35°C, 45°C, 55°C, 65°C and 75°C.

Figura 3. Curvas de absorción de agua de los granos de arroz con cáscara (cv. Urucuia) a temperaturas de 35°C, 45°C, 55°C, 65°C y 75°C.

Table 5. Thermodynamic properties (∆H: enthalpy; ∆S: entropy; ∆G: Gibbs free energy) of drying and water absorption processes of husk rice grain (cv. Urucuia).

Tabla 5. Propiedades termodinámicas (∆H: entalpía; ∆S: entropía; ∆G: energía libre de Gibbs) de los procesos de secado y absorción de agua de las cáscaras de granos de arroz (cv. Urucuia).

Process	Temperature (ºC)	Thermodynamic property
		∆H (kJ mol^−1)	∆S (kJ mol^−1 K^−1)	∆G (kJ mol^−1)
Drying	35	48.47	−0.1084	81.86
	45	48.38	−0.1086	82.95
	55	48.30	−0.1089	84.04
	65	48.22	−0.1092	85.13
	75	48.13	−0.1094	86.22
Absorption	35	−6.27	−0.2454	69.36
	45	−6.35	−0.2457	71.82
	55	−6.43	−0.2460	74.28
	65	−6.52	−0.2462	76.74
	75	−6.60	−0.2464	79.20

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