Tambunan, Armansyah H, Indonesia
Jurnal Keteknikan Pertanian Vol. 11 No. 1 (1997): Buletin Ketenikan Pertanian - Articles
Freeze drying of food materials is a time and energy consuming process, hence a high cost process. The drying rate is limited by heat and mass transfer process within the dried portion of the product. In order to improve the freeze drying performance, it is important to know parameters which affect the drying characteristics of each spesific food material, in regard to the drying time and the energy consumption. The objective of this experiment was to study the freeze drying characteristic of miched beef especially the effect of freezing rate and surface temperature of the material to the drying time.
The study was conducted with freezing rate at 7.71 cmhours and 1.94 cmhours which are classified into fast and slow freezing rate, while the surface temperature of the material was controlled at 40 OC, 35 OC, and 30 OC. The experimental results confirmed that the faster freezing rate then the longest drying time, while the higher surface temperature give a shorter drying time of miched beef. It is important to determine the optimal freezing rate and surface temperature from the view point of energy consumption.
Jurnal Keteknikan Pertanian Vol. 12 No. 2 (1998): Buletin Ketenikan Pertanian - Articles
The ratio of specifc heat capacity, at constant presszrre to that at constant volume (cdc,J, of a gas can be determined by either the adiabatic expansion method or the sound velocity method. The objective of this experiment is apply the adiabatic expansion method for determining the spec$c heat capacity ratio of gas N2 and O2 The result showed that the ratio were 1.14 and 1.19 respectively for gas N2 and 02.T he value obtained by the experiment was d~flerenta bout 15 to 19% from the result determined by theoretical method using 5 degree of Jkeedom. Theoretically cdc,, of both gas N2 and 0 2 which have 5 degree offreedom are 1.4. The dzflerence was considered to be caused by thee xperimental condition, which were not suflciently adiabatic, as required by the method. However, the simplicity of the method and clarity of its theoretical approach is advantageous to be used by students of Advance Thermodynamic class as a practical exercise.