(a) (10%) What is the definition and meaning of D/Dt?

(a) (10%) The heat transfer rate of the heat exchanger

(b)(10%) The outlet temperature of the heating liquid

(c) (10%) The logarithmic mean temperature difference ( the ratio of difference of the temperature difference between the two streams at end A and end B over [In(temperature difference between the two streams at end A)- In(temperature difference between the two streams at end B)]

(d)(10%) The length of the heat exchanger

(b)(10%) In this flow, is it compressible? Why or why not?

(c) (10%) Simplify the equations if steady

(d)(10%) Simplify the equations if steady and inviscid.

(e) (10%) Simplify the equations if steady, inviscid, and 2D flow (x-y coordinately only)

3. (10%) A steel rod with an initial carbon concentration 0.2% by weight is to be hardened. An equilibrium concentration of carbon in iron at the phase interface of 1.5%. Calculate the time required for the location Imm below the surface to have a carbon mass concentration of 0.8%. The diffusion coefficient of carbon in steel at the process temperature is . Hints: The similarity variable for this problem is , and the erfc(x)= 1 - erf(x)

一、 根據一些社會學研究指出，健康有其社會基礎，亦即健康與階級、性別及族群（或種族）具有密切的相關。試分別舉出一個以上日常生活中的例子，說明這樣的關係。