Answer Happy

Brief questions (7×5 score=35 score) 1. Please write out the three kinds of boundary conditions for heat conduction problems in mathematical and physical language. 2. How does the local convective heat transfer coefficient vary for convective heat transfer in the tube? Why should consider the pipe length effect for experimental correlations? 3. Please explain how the geometric parameters, physical properties and heat transfer conditions of the thermocouple affect the response rate of the thermocouple when using the thermocouple to measure the fluid temperature. Someone said, "I just bought a very sensitive temperature measuring element on the specification of its time constant te <0.1s", is this reasonable? 4. What are the effects of non-condensing gases on condensation and boiling heat transfer? And explain why. 5. Please write down the expressions of criterion numbers Nu and Bi, and briefly describe their physical meaning. 5. When boiling on a horizontally heated surface (with controllable wall temperature), does the convective heat transfer coefficient of boiling definitely increase with the increase of wall excess temperature? Why is that? 6. Does the electrical insulating layer on the surface of the electrical wire have the function of thermal insulation? Why? 7. The temperature of the surface of a black body is 227°C, please calculate the radiation intensity.