Kinetics of Kaymak separation

U radu su prikazani rezultati eksperimentalnih ispitivanja kinetike procesa izdvajanja kajmaka iz mlijeka, s ciljem da se dobiveni podaci iskoriste kao podloga za razvoj novog proizvodnog tehnološkog postupka. Izdvajanje kajmaka obavljeno je u instalacijama laboratorijskih razmjera. U toku procesa, mlijeko je stalno zagrijavano na povišene temperature, a iznad slobodne površine strujao je ugrijani zrak. Parametri procesa, čiji je utjecaj na prinos kajmaka proučavan, bili su: visina sloja mlijeka, temperature mlijeka i zraka i brzina strujanja zraka. Dobiveni eksperimentalni rezultati ukazuju da se pogodnim izborom radnih parametara procesa, mogu ostvariti takve brzine izdvajanja kajmaka koje su nekoliko puta veće u odnosu na brzine procesa ostvarene pri tradicionalnim, postupcima proizvodnje.Kinetics of kaymak separation was studied on a laboratory scale experimental equipment. Obtained results were used for developing a new kaymak production process. During the kaymak separation, the bulk of milk was heated using a hot water heat exchanger. Drying of the kaymak layer, separated on the milk surface, was performed by hot airflow. Kaymak yield was analysed as a function of the following parameters: depth of the initial milk layer, temperature gradients in the bulk of milk as well as in the air over the milk surface, and the rate of airflow. Obtained experimental results have shown that the rate of the kaymak separation can be significantly increased by selecting the appropriate working parameters

Temperature and moisture distributions inside the layer of moist material placed on hot isothermal surface

The problem of contact drying of a layer of moist material placed on a hot isothermal surface is considered. A system of heat and mass transfer equations and equations for the initial and boundary conditions are proposed. Luikov's theoretical approach is utilized, but all relevant thermophysical coefficients are considered to be fully dependent on the temperature and moisture content inside the material during the process. The model is solved numerically. Results for temperature and moisture distributions inside the layer of the material obtained using this model are compared to results obtained by solving a model with constant thermophysical coefficients in the governing equations, formed by using the same type of heat and mass transfer equations and equations for the initial and boundary conditions. The process is also examined experimentally, which provided results that enable verification of the proposed models