4. The net radiative heat flux at the surface of an opaque medium can be evaluated using the rollowing equation if the absorptivity of the medium is cqual to its emissivity
  
where E is the emissivity, o the Stefan-Boltzmann constant, Ts the surface temperature and J the radiosity. This equation seems to predict a very large radiative heat flux for a blackbody that (5%) hasε = 1. Please explain.

10. even though

1.如圖所示系統可用來量測水壓力之增加值△p,試問:當系統其XLiquid 液面高度上升 80mm(△h=80mm)時,水槽壓力改變量△p為何? (25%)

2. Two horizontal, infinite, parallel plates are spaced a distance b apart, please see the following figure. A viscous liquid is contained between the plates. The bottom plate is fixed (y = 0), and the upper plate (y = b) moves parallel to the bottom plate with a velocity U. Because of the no-slip boundary condition, the liquid motion is caused by the liquid being dragged along by the moving boundary. Assuming that there is no pressure gradient in the direction of flow (x-direction) and the flow is steady and incompressible without the y-component velocity. (a) Derive the governing equation of the above 2-D flow from the x-direction Navier-Stokes equation (see below). (b) Determine the velocity distribution between the plates. (c) Determine an expression for the flowrate per unit width passing between the plates. Express your answers of (b) and (c) in terms of b and U. (25%) 

3. A hot solid cube (having sides of equal length) of temperature Tco is put into a pot containing cold water of temperature Two. Assume that the heat exchange only occurs between the cube and water. (20%) (a) Write down the equation for determining the final equilibrium temperature. (b) Assuming both the cube and water keep spatially uniform in temperature, write down the equation for evaluating the temperature evolution for the cube and water, respectively. (c) Consider the cube is not spatially uniform in temperature but the water is. Write down the equation and boundary conditions for evaluating the temperature distribution in the cube. (d) Consider neither the cube nor the water keeps uniform in temperature. Write down the equation and boundary conditions for evaluating the temperature distribution in the water.

5. What are the definitions of the following terms? (10%) (a) Friction coefficient； (b) Biot number； (c) Stanton number； (d) Nusselt number； (e) Prandtl number. [Example]: Reynolds number, ReD= puD/μ, where r: fluid density, u: flow velocity, D: tube diameter, and u: fluid viscosity.

6. Please sketch the velocity and temperature profiles of laminar and turbulent flows in a circular  tube by following the format of the example.(6%)

 (a) What temperature should you use for evaluating the fluid properties? (2%)

(b) Is it a laminar flow or turbulent flow at the midpoint (x=0.5 m)? (2%)

(c) Please calculate the local heat transfer coefficient at the midpoint (x=0.5 m) of the flow. (5%) 

題目一:【10分】 請說明彈簧之功用並各舉出一個應用實例。