Engineering, 12.08.2020 07:01 jeffcarpenter

A thermocouple junction with a diffuse and gray surface (A_S = 0.2 m^2) is placed in a large environment of temperature at 300 K. The junction is used to measure the temperature of a moving fluid surrounding the surface (T_infinity). The heat transfer coefficient is h = 20 W/m^2-K. The total hemispherical irradiation from the environment incident on the small surface is 460 W/m^2. The total hemispherical emissivity of the surface is 0.95. Required:
a. What is the radiation energy incident on the surface per unit time (q_irra)?
b. What is the total hemispherical absorptivity alpha?
c. What is the radiation energy absorbed by the surface per unit time q_abs?
d. If after steady state, the temperature of the junction senses a temperature of 320 K, what is the total hemispherical emitted power E from the junction surface?
e. What is the radiation energy emitted from the junction surface per unit time q_emit?
g. Apply energy balance to the junction after steady state. Neglect the contribution from the thermocouple wires. Calculate the temperature of the fluid. What is the major reason that the temperature of the fluid cannot be accurately measured by the thermocouple junction?

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