engleski

Comparative measurement and evaluation of the Quenching intensity of a petroleum quench oil and palm oil based on temperature gradients

In contrast with small laboratory probes developed to check the sample of a quenchant, the new Liščić /Petrofer probe is designed to measure and record the quenching intensity in real industrial conditions. The probe is a cylinder of 50 mm diameter and 200 mm length, made of INCONEL 600, and instrumented with 3 thermo-couples on the same radius of the cross- section at the middle of the length. The outer thermocouple measures the temperature at 1 mm below surface ; the second thermocouple is located at 4.5 mm below the surface, and the third thermocouple is located at the center of the probe. The working principle of the probe is the measurement of the dynamics of heat extraction which is best represented by the change of temperature gradients. The results of each test with this probe are presented in the form of 4 diagrams: 1.) The recorded cooling curves ; 2.) The calculated heat transfer coefficient (α) as function of time ; 3.) The calculated α as function of surface temperature ; and 4.) The calculated surface temperature with characteristic points on the temperature and on the time scale. For impartial and precise evaluation of a test, 6 characteristic criteria from these diagrams are applied.The series of 26 tests recently performed with this probe at the Quenching Research Centre (QRC) of the Faculty for Mechanical Engineering, University of Zagreb, Croatia has shown that by using this probe, distinctive differences canola oil and a petroleum oil quenchant are easily characterized. Final conclusions of this series of tests confirm that: a)The information provided, which is valuable for the practical use of a quenchant, is not obtainable from any of the small laboratory probes that are currently standardized (ISO 9950, ASTM D6200 and JIS K2242 ; b)The probe and the evaluation method are sufficiently sensitive to clearly differentiate the results with changes of quenching conditions ; c)The Liščić /Petrofer probe can be used for different types of liquid quenchants under different quenching conditions and it is a unique device to evaluate and compare their quenching intensity in industrial practice.

Quenching intensity; Temperature Gradient Method; Heat transfer coefficient.

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