Thermal Conductivity Measurement and Prediction of Particulate Foods

Figures & data

TABLE 1 Protein, fat, and carbohydrate compositions of the powdered foods (mass basis)

	Protein	Fat	Carbohydrate
	%	%	%
Cocoa	20	14	59
Corn starch	-	-	88
Milk powder	24	24	35
Sucrose	-	-	99
Wheat flour	12	2	72

TABLE 2 Bulk densities, moisture contents, and thermal conductivities of five powdered foods measured at 20°C

	Bulk density	Moisture content	Thermal conductivity
	kg m^–3	(mass fraction)	W m^–1 K^–1
Cocoa	405	0.0785	0.044
Corn starch	690	0.116	0.081
Milk powder	565	0.161	0.061
Sucrose	777	0.00920	0.085
Wheat flour	656	0.150	0.085

TABLE 3 Comparison of measured data against thermal conductivity bounds

	ɛ		k (Wm^–1 K^–1)
			Modelled
		Measured	(Eq. 1)	(Eq. 2)	(Eq. 3)	(Eq. 4)	(Eq. 5)
Cocoa	0.70	0.044	0.094	0.034	0.047	0.078	0.057
Corn starch	0.54	0.081	0.149	0.043	0.068	0.125	0.101
Milk powder	0.53	0.061	0.146	0.044	0.068	0.123	0.100
Sucrose	0.51	0.085	0.127	0.045	0.067	0.109	0.093
Wheat flour	0.54	0.085	0.155	0.044	0.068	0.130	0.104

FIGURE 1 Thermal conductivity data for wheat flour along with thermal conductivity bounds.

FIGURE 2 Thermal conductivity data for cocoa along with thermal conductivity bounds.

FIGURE 3 Thermal conductivity data for sucrose along with thermal conductivity bounds.

TABLE 4 Comparison of measured data against thermal conductivity predictions

	ɛ		k (Wm^–1 K^–1)			ξ
		Measured	Eq. (11)	Eq. (12)	Eq. (15)	Eq. (11)	Eq. (12)	Eq. (15)
Cocoa	0.70	0.044	0.0505	0.0585	0.0652	0.0061	0.0140	0.0208
Corn starch	0.54	0.081	0.0782	0.0918	0.0941	0.0029	0.0107	0.0131
Milk powder	0.53	0.061	0.0782	0.0914	0.0932	0.0173	0.0306	0.0324
Sucrose	0.51	0.085	0.0748	0.0860	0.0865	0.0102	0.0010	0.0015
Wheat flour	0.54	0.085	0.0799	0.0941	0.0965	0.0047	0.0095	0.0119
Average						0.0082	0.0132	0.0159