M E 4210 Lecture 2: ME 4210_Lecture #02_F2014

• School: Wayne State University
• Department: Mechanical Engineering
• Course: M E 4210
• Professor: Bashar S.Abdul Nour

Document Summary

Suppose that we have a plane wall with t1 > t2. Heat will be transferred from surface s1 to s2 in the direction of decreasing t. Fourier"s law states that the total heat transfer rate, q, is directly proportional to the area, a, and the temperature differential t (= t1 t2), but inversely proportional to the distance x between the two surfaces; i. e. , q. The above can be written in terms of equality as. 1 [ x. x] refers to the corresponding section number a in the textbook. Dr. bashar abdulnour where the negative sign is introduced to account for the decrease in t as x increases; i. e. , negative temperature gradient. Heat transfer is a directional (or vector) quantity, which takes place in the direction normal to surfaces of constant temperature (i. e. , isothermal surfaces). Then the above relationship can also be written as q x dtak dx q n.