Before introducing apples to cold storage, they should be cooled to a temperature of 3°C in order to avoid problems when exposing the hot apples to the much lower temperature in the storage. It is assumed that the apples are initially at 25°C, they are spheres of 7 cm diameter and that the cooling is carried out by means of an airstream at −1°C, to a such velocity that the heat convection coefficient is 30 W/(m2 °C). Calculate the necessary time to cool the apples so that its geometric center reaches 3°C. Data (apple properties): density, 930 kg/m3 ; thermal conductivity, 0.50 W/(m °C); specific heat, 3.6 kJ/(kg °C)

Before introducing apples to cold storage, they should be cooled to a temperature of 3°C in order to avoid problems when exposing the hot apples to the much lower temperature in the storage. It is assumed that the apples are initially at 25°C, they are spheres of 7 cm diameter and that the cooling is carried out by means of an airstream at −1°C, to a such velocity that the heat convection coefficient is 30 W/(m2 °C). Calculate the necessary time to cool the apples so that its geometric center reaches 3°C. Data (apple properties): density, 930 kg/m3 ; thermal conductivity, 0.50 W/(m °C); specific heat, 3.6 kJ/(kg °C)

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter8: Natural Convection

Section: Chapter Questions

Problem 8.60P

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