SHIELDED HOT-WIRE VISCOSITY SENSOR ONLINE FOR A FLOWING SYSTEM USING A SHIELD OF HIGH THERMAL-CONDUCTIVITY

Application of a hot-wire viscosity sensor, which measures the intensi ty of the natural convection around a hot wire, have been limited to t he stagnant systems. For the adaptation of the hot-wire viscosity sens or to flowing systems, the hot-wire viscosity sensor was protected fro m the effects of the flow by using a stainless steel shield. The shiel d was normally left open, and was closed only when the measurement was done. Although the hot-wire sensor response was influenced by the flo w outside the shield through the high thermal conductivity of the shie ld material, this effect could be eliminated when the sensor was used at a sufficiently high flow rate outside the shield. The shielded hot- wire sensor responded welt to changes in the viscosity of the test flu id in a wide range of viscosity. The effects of the size of the shield and the heat-flux applied on the sensor response were investigated. T he shielded hot-wire viscosity sensor was used for the monitoring of t he hydrolysis of starch by alpha-amylase.