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A 'long' steel shaft of 10 cm diameter is austenised at 870°C and then quenched in a liquid at 30°C. The average surface heat transfer coefficient is 2000 W/m² °C. The relevant thermophysical properties of the shaft material are k = 20 W/m °C; p= 7800 kg/m³; c, = 0.46 kJ/kg °C. Calculate: (i) the time required for the centre-line temperature to drop down to 200°C (martensite forms at this temperature), (ii) the temperature at half-radius at that moment, and (iii) the amount of heat that has been transferred to the liquid by that time per metre length of the shaft.

A 'long' steel shaft of 10 cm diameter is austenised at 870°C and then quenched in a liquid at 30°C. The average surface heat transfer coefficient is 2000 W/m² °C. The relevant thermophysical properties of the shaft material are k = 20 W/m °C; p= 7800 kg/m³; c, = 0.46 kJ/kg °C. Calculate: (i) the time required for the centre-line temperature to drop down to 200°C (martensite forms at this temperature), (ii) the temperature at half-radius at that moment, and (iii) the amount of heat that has been transferred to the liquid by that time per metre length of the shaft.

Introduction to Chemical Engineering Thermodynamics
Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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A 'long' steel shaft of 10 cm diameter is austenised at 870°C and then quenched in a liquid at 30°C. The average surface heat transfer coefficient is 2000 W/m² °C. The relevant thermophysical properties of the shaft material are k = 20 W/m °C; p = 7800 kg/m³; c = 0.46 kJ/kg °C. Calculate: (i) the time required for the centre-line temperature to drop down to 200°C (martensite forms at this temperature), (ii) the temperature at half-radius at that moment, and (iii) the amount of heat that has been transferred to the liquid by that time per metre length of the shaft.
Transcribed Image Text:A 'long' steel shaft of 10 cm diameter is austenised at 870°C and then quenched in a liquid at 30°C. The average surface heat transfer coefficient is 2000 W/m² °C. The relevant thermophysical properties of the shaft material are k = 20 W/m °C; p = 7800 kg/m³; c = 0.46 kJ/kg °C. Calculate: (i) the time required for the centre-line temperature to drop down to 200°C (martensite forms at this temperature), (ii) the temperature at half-radius at that moment, and (iii) the amount of heat that has been transferred to the liquid by that time per metre length of the shaft.
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