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 Prandtl number for a flowing fluid greater than unity indicates that the hydrodynamic boundary layer thickness is a. less than the thermal boundary layer thickness b. equal to the thermal boundary layer thickness c. greater than the thermal boundary layer thickness 3. In natural convection heat transfer, the Nusselt number is a function of a. Re and Pr b. Re and Gr c. Gr and Pr 4. A fluid is flowing coefficient along the length a. decreases long a plate ng a uniform heat flux. The local transfer b. remain constant c. increases 5. For fully developed laminar flow and heat transfer in a heated long circular tube, if the flow velocity is doubled and the tube diameter is halved, the heat transfer coefficient will be b. half of the original value a. four times of the original value before c. same as d. double of the original value

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 Prandtl number for a flowing fluid greater than unity indicates that the hydrodynamic boundary layer thickness is a. less than the thermal boundary layer thickness b. equal to the thermal boundary layer thickness c. greater than the thermal boundary layer thickness 3. In natural convection heat transfer, the Nusselt number is a function of a. Re and Pr b. Re and Gr c. Gr and Pr 4. A fluid is flowing coefficient along the length a. decreases long a plate ng a uniform heat flux. The local transfer b. remain constant c. increases 5. For fully developed laminar flow and heat transfer in a heated long circular tube, if the flow velocity is doubled and the tube diameter is halved, the heat transfer coefficient will be b. half of the original value a. four times of the original value before c. same as d. double of the original value

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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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 5. For fully developed laminar flow and heat transfer in a heated long circular tube, if the flow velocity is doubled and the tube diameter is halved, the heat transfer coefficient will be a. four times of the original value before b. half of the original value с. same as d. double of the original value
Heat transfer Air flows through a smooth thin-walled rectangular duct of height, a= 0.3 m and width, b=1 m. The air is heated by the duct walls at a uniform heat flux of 250 W/m2 . At some location inside the duct, the mean velocity and temperature of air was measured to be um = 0.05 m/s and Tm = 350 K, respectively. (a) What is the hydraulic diameter of the duct? (b) What is the Reynolds number for the flow in the duct? (c) Is the flow laminar or turbulent? (d) Assuming fully developed flow, what is the heat transfer coefficient (h) at this location?
Air is to be heated by passing it across the tubes of an in-line tube bundle consisting of 8 rows of 25 mm OD tubes in the direction of flow and 10 tubes in each row normal to the flow. Air approaches the tube bank in the normal direction at 30 °C and 1 atm with a mean velocity of 10 m/s. The tube spacing is 37.5 mm in both parallel and normal to the flow. Calculate the heat transfer from the bundle per m of length when the tube surface temperature is 90 °C.
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Water flows through a tube of 5mm inside diameter with a volumetric flow rate of 7.8 cm3/s. Wall temperature of the tube is kept constant at 80oC. In a fully developed velocity and temperature profile region of 5m length, calculate the bulk temperature of exiting water if its inlet temperature is 20oC
Write your answer in 4 decimal places. DO NOT round off intermediate values. Water at a mean temperature of 25°C flows across a 1-cm square tube in cross-flow with a Reynolds number of 10,000. Calculate (a) Nu and (b) the convection heat transfer coefficient Answers: а. b. W/m?.K
Air is to be heated from 15 C to 270 C, as it flows through a tube 25mm diameter at average velocity 30 m/s. The tube surface is maintained at 280 C and the air is to be provided at rate 0.013 kg/s. Take the water properties k=0.0336 W/m.C, U = 25.9x 10-6 m2/s , Cp=1.014 kJ/kg.C, p = 0.8826 kg/ m3, Pr=0.689 Determine the following : 1- Heat transfer rate. 2- The necessary tube length. 3-Heat transfer coefficient?
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1. Experimental analysis was carried out about turbulent convective heat transfer in trapezoidal cross-sectioned duct.Average Nusselt numbers and Reynolds numbers were determined for each experiment and the following data set have beenobtained from this investigation. Find an engineering correlation between the average Nusselt number and Reynolds numberin the form ofNu = aReb
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