ME 340 Project: Fall 2010Heat Transfer in a Rice Cooker

Brad GlennMason Campbell

Introduction

• Knowing the heating power of a rice cooker, we will heat a known mass of water and predict the outer surface temperature of the pot. In order to accomplish this we need to calculate a convection coefficient and the overall thermal resistance between the water and the surface of the pot.

Set up of the Problem

• Create a thermal circuit of the conduction through the pot and convection between the pot and the water.– Assuming natural convection, determine the

convection coefficient of the water– Then determine the overall thermal resistance of the

circuit• Assuming a constant heat rate, determine the

temperature of the pot surface after 30 seconds.• (See Appendix for details)

Solution

• Temp of water initially T1=38.3 C• Heat rate of rice cooker q=275 W

• Convection coefficient h=971.53 W/m^2 K• Thermal Resistance Rtot=.09226 K/W

• Predicted temp of pot surface Ts=69.5 C

Results of Experiment

• Measured value of Ts=75.8 C

Conclusions

• We think one of the biggest sources of error in our assumptions was that our convection coefficient was too high resulting in lower predicted surface temperature. – One possible reason for this error was that we had

to assume the inner surface temperature when calculating the Grashof number.

– More iterations are recommended for a more accurate result.

Appendix