Choose the right answer 1. The mean Nusselt number for fully developed laminar flow in a circular tube under a constant heat flux a. depends on Reynolds number b. depends on Prandtl number c. is constant 2. The value of Prandtl number for air is about а. О.1 b. 0.3 с. 0.7 3. In natural convection heat transfer, the Nusselt number is a function of a. Re and Pr b. Re and Gr c. Grand Pr 4. A fluid is flowing along a plate having a high uniform wall temperature. The heat transfer along the length a. decreases b. remain constant c. increases

Choose the right answer 1. The mean Nusselt number for fully developed laminar flow in a circular tube under a constant heat flux a. depends on Reynolds number b. depends on Prandtl number c. is constant 2. The value of Prandtl number for air is about а. О.1 b. 0.3 с. 0.7 3. In natural convection heat transfer, the Nusselt number is a function of a. Re and Pr b. Re and Gr c. Grand Pr 4. A fluid is flowing along a plate having a high uniform wall temperature. The heat transfer along the length a. decreases b. remain constant c. increases

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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Consider pressurized water, engine oil (unused), and Nak (22%/78%) flowing in a 20-mm-diameter tube. (a) Determine the mean velocity, in m/s, the hydrodynamic entry length, in m, and the thermal entry length, in m, for each of the fluids when the fluid temperature is 366 K and the flow rate is 0.01 kg/s. (b) Determine the mass flow rate, in kg/s, the hydrodynamic entry length, in m, and the thermal entry length, in m, for water and engine oil at 300 and 400 K and a mean velocity of 0.022 m/s. Part A Determine the mean velocity, in m/s, the hydrodynamic entry length, in m, and the thermal entry length, in m, for each of the fluids when the fluid temperature is 366K and the flow rate is 0.01 kg/s. Liquid Um (m/s) Xfdh (m) Xfd,t (m) water i engine oil i i i Nak i
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Local Nusselt number for fully developed (hydrodynamically and thermally) turbulent flow in a smooth circular tube is defined by Nup-hD/kr, where h, D, and ke are the convective heat transfer coefficient, tube diameter, and fluid thermal conductivity, respectively. The friction factor for the smooth circular tube is given by the Blasius correlation, f-0.316Rep. The Reynolds number is defined by Ren-pviD/, where pr, vi, and ur are the fluid density, fluid velocity, and fluid viscosity, respectively. The Blasius correlation is applicable to Rep<2×10¹. Considering the analogy between velocity and thermal boundary layers and using the Blasius correlation, express the local Nusselt number using Reynolds and Prandtl numbers in the form of Nup-AxRepxPr. The Prandtl number is defined by Pr-wa, where and are the fluid kinematic viscosity and fluid thermal diffusivity, respectively. Note that the local Nusselt number formula should be applicable to Rep<2x10 and 0.6
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