Air flows through an uninsulated circular duct of 5 cm diameter at a mass flow rate of 0.03 kg/s. Air enters the duct at 95 °C and leaves the duct at a temperature of 70 °C. Length of the duct is 7 m and it is exposed to ambient at 3 °C. Determine the convective heat transfer coefficient, h. Properties of air at mean temperature are: ρ = 0.993 kg/m3, μ = 210x10-7 N-s/m2, k = 0.0304 W/m-K, and Cp = 1 KJ/kg-K. Assume the viscosity of wall temperature and of mean temperature are equal.
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Air flows through an uninsulated circular duct of 5 cm diameter at a mass flow rate of 0.03 kg/s. Air enters the duct at 95 °C and leaves the duct at a temperature of 70 °C. Length of the duct is 7 m and it is exposed to ambient at 3 °C. Determine the convective heat transfer coefficient, h.
Properties of air at mean temperature are: ρ = 0.993 kg/m3, μ = 210x10-7 N-s/m2, k = 0.0304 W/m-K, and Cp = 1 KJ/kg-K. Assume the viscosity of wall temperature and of mean temperature are equal.
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- Water is to be heated from 15 C to 65 C as it flows through a 3 cm internal diameter 5 m long tube. The tube surface is subjected to uniform heat flux. If the mean water velocity is 0.236 mm/s, determine 1. The total heat transferred to water. 2. The inner surface temperature of the pipe at the inlet and the exit. Take water properties p=992.1 kg/m³, v 0.658 x 10-6 m²/ s Cp=4179 J/kg.K, Pr-4.32, Nu= 0.023Re08Prº.4 k=0.631 W/m.°C,Heated air at 1 atm and 35°C is to be transported in a 150-m-long circular plastic duct at a rate of 0.35 m3/s . If the head loss in the pipe is not to exceed 20 m, determine the minimum diameter of the duct (a) Now the duct length is doubled while its diameter is maintained constant. If the total head loss is to remain constant, determine the drop in the flow rate through the duct.Consider a triangular duct 40 m long, with a = b = c = 220 mm as shown in the figure, it is kept at a constant surface temperature of 5°C. Liquid water enters the pipeline at 20°C and 1 atm, at a volumetric flow rate of 7920 L/h. Determine the leaving temperature of the water and the rate of heat transfer to the water b 0 = 60° Te=20.51°C Q=-4528.83
- 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 0.6Question 2 Air (Cp= 1.005 kJ/kg.°C) enters a 7-m-long, 7.2-cm-diameter pipe at 63°C at a rate of 0.06 kg/s. The air cooled at an average rate of 320 W/m² surface area of the pipe. The air temperature at exit of the pipe is:Liquid mercury is flowing at 0.9kg/s through a 5-cm diameter tube with inlet and outlet mean temperatures of 100°C and 200°C, respectively. The tube surface temperature is maintained constant at 250°C. Determine the tube length using the Dittus-Boelter equation, in m. ______ mAir at atmospheric pressure flowing through a tube of 10 cm diameter at a rate of 0.1 kg/s is to be cooled from 400K to 300K with uniform wall temperature of 250K. Determine the length of the tube. Justify any assumptions that you have made.Combustion gases passing through a 5-cm-internal-diameter circular tube are used to vaporize waste water at atmospheric pressure. Hot gases enter the tube at 225 kPa and 250oC at a mean velocity of 2.5 m/s, and leave at 150o If the average heat transfer coefficient is 150 W/m2K and the inner surface temperature of the tube is 110oC, determine (a) the tube length and (b) the rate of evaporation of water.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 kr 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-0.316Red ¹/4. The Reynolds number is defined by Rep-prviD/μr, where pr, vr, 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 NuD-A-ReDxPr. The Prandtl number is defined by Pr-war, where and ar are the fluid kinematic viscosity and fluid thermal diffusivity, respectively. Note that the local Nusselt number formula should be applicable to Rep<2×10 and 0.6Air enters a 7-m-long section of a rectangular duct of cross section 15 cm X 20 cm at 50°C at an average velocity of 7 m/s. If the walls of the duct are maintained at 10°C, determine: (a) the outlet temperature of the air, (b) the rate of heat transfer from the air, and (c) the fan power needed to overcome the pressure losses in this section of the duct.Consider a pipe with a length of 25 m and diameter of 5 cm. The surface temperature of the pipe is constant at 150°C.Oil at 20°C is passing though this pipe with a mass flow rate of 0.5 kg/s. determine (a) the temperature of the oil at the exit and (b) the total heat transfer rate. Note. Report your solution step by step and clearly.Air at 1atm, 35 degree celcius (ρ = 1.145 kg/m3 and μ = 1.895 x 10-5 kg/m.s) and average velocity of 7 m/s, enters a 10m section of a circular pipe with diameter of 20cm. Neglecting the entrance effects, determine the fan power needed to overcome the pressure losses in the duct. Use friction factor f= 0.020336SEE MORE QUESTIONSRecommended textbooks for youElements Of ElectromagneticsMechanical EngineeringISBN:9780190698614Author:Sadiku, Matthew N. O.Publisher:Oxford University PressMechanics of Materials (10th Edition)Mechanical EngineeringISBN:9780134319650Author:Russell C. HibbelerPublisher:PEARSONThermodynamics: An Engineering ApproachMechanical EngineeringISBN:9781259822674Author:Yunus A. Cengel Dr., Michael A. 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