Production and Quality Control

Thermal conductivity of lipidic emulsions has been experimentally determined by the probe method. To this purpose a special probe has been designed and built in laboratory, with small diameter (0.6 mm) and a high length to diameter ratio (≈100). The temperature sensor of the probe (type T thermocouple) and the heater (Pt wire) were properly calibrated. Moreover, the probe performance has been tested by means of a pure liquid (glycerin) having well known thermal conductivity by literature. Differences of about 1.5% at ambient temperature in thermal conductivity values between literature and experiments were found. On lipidic emulsions first thermal conductivity has been measured in the temperature range 10÷40°C, second the same property as a function of time at constant temperature (40°C), then the values after freezing at –15°C and reheating at 20 °C; and last the kinetics of degeneration. Results show a significant difference between thermal conductivity values of a new emulsion (≈0.51 W/m K), compared with the creamed one (≈0.62 W/m K), and the decayed one (≈0.68 W/m K ). It has also put into evidence why the frozen emulsion cannot be used for intravenous injection, i.e. viscosity increases because of breaking of the oil particles. Finally information about the kinetics of the degeneration process have been obtained. The uncertainty resulting from the calibration and tests justifies the possible use of the measurement technique for process control of production, and also for quality control in the clinical practice. 1. Introduction Between the thermo physical properties of materials, thermal conductivity and thermal diffusivity (or thermal capacity) are responsible of the steady state and transient thermal behaviour, respectively. This is the reason why they play a key role in explaining thermal phenomena and in designing thermal devices. Besides, being these properties dependent on material chemical composition, treatment and resulting structure (porosity, size of void space, homogeneity, presence of fibres and their orientation), an accurate knowledge of their values can be used to judge the production process of goods or their quality. As an example, thermal conductivity of porous media (as bricks) can be used to evaluate their water content. Thermal diffusivity and thermal conductivity can be measured independently or simultaneously, being their value joined by the relationship p