Investigation of heat transfer coefficient during quenching in various cooling agents

Heat transfer coefficients, HTCs, at the surface of a metal sample during immersion quenching were measured and evaluated using numerical procedures. The boundary inverse heat conduction problem has been defined and solved. A FEM self-developed computer code has been used to obtain a solution to the direct problem. The sensitivity of the method enabled us to examine the effect of various quenching parameters on the heat transfer for two mineral oils and a polymer quenchant. At 800 degrees C the HTC values were equal to similar to 0.5 kW/(m(2) K) and similar to 3.2 kW/(m(2) K), for mineral oils and a polymer coolant, respectively. They increased to similar to 4.7 kW/(m(2) K) - oil A, similar to 6.0 kW/(m(2) K) - oil B and similar to 7.4 kW/(m(2) K) - polymer, respectively. The peak of HTC was sharp and occurred at a narrow temperature interval between 520 and 550 degrees C for the oils, whereas for the polymer, the peak was lower by approx. 100 K and flat over 100-120 K interval. Subsequently HTC decreased, and at similar to 150 degrees C the values were similar to 0.5 kW/(m(2) K) and similar to 2.0 kW/(m(2) K), for mineral oils and a water polymer coolant, respectively. (C) 2013 Elsevier Inc. All rights reserved.