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Concept explainers
The air passage for cooling a gas turbine vane can be approximated as a lube of 3-mm diameter and
(a) For an airflow rate of
(b) Generate a plot of the air outlet temperature as a function of flow rate for
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Fundamentals of Heat and Mass Transfer
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- Air at 22˚C and at atmospheric pressure flows over a flat plate at a velocity of 1.65 m/s. If the length of the plate is 2.179 m and its temperature is 98 ˚C, Calculate Heat rate by using exact and approximate methods both. What is the %age difference of the heat transfer rate values by these methods? Take width of the plate as unity. Properties given at 60˚C are as follows: Density: 1.058 kg/m3 , cp = 1.005 kJ/kg˚C, k= 0.02897 w/m˚C, Kinematic viscosity is 18.97 × 10-6 m2 /sarrow_forwardCurrent Attempt in Progress 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 0.014 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 0.018 m/s. Part A Your answer is incorrect. 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 0.014 kg/s. Liquid water engine oil Nak (m/s) ! i XALA(M) xer (m) Attempts: unlimited Submit Answerarrow_forwardChoose 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. 0.1 b. О.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 C. same as d. double of the original valuearrow_forward
- 5.0 Air at p=p= 1 atm enters a thin-walled (D=D= 5-mm diameter) long tube (L=L= 2 m) at an inlet temperature of Tm,i=Tm,i= 100°C. A constant heat flux is applied to the air from the tube surface. The air mass flow rate is m˙ =m˙ = 125 × 10-6 kg/s. If the tube surface temperature at the exit is Ts,o=Ts,o= 160°C, determine the heat rate entering the tube, in W. Evaluate properties at T=T=400 K.arrow_forwardAir at 0.8 atm enters at 18 C. Flows across bank of tubes 13 rows high and 7 rows deep at velocity of 9 m/s .The surfaces of tubes are maintained at 78 . The length of tubes is 1.2 m and the diameter of 1.5 cm .They are arranged in staggered manner so that the spacing in both the vertical and horizontal direction are 3cm and 2.25cm respectively. Calculate the total heat transfer and the exit air temperature.arrow_forward1. 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 = aRebarrow_forward
- Fully developed conditions are known to exist for water flowing through a 50-mm ID tube at 0.02 kg/s and 27°C. What is the maximum velocity of the water in the tube? What is the pressure gradient associated with the flow?arrow_forward11 An airstream of speed 160 m/s and temperature 3000 K travels on the inside of a 30 cm I.D. steel tube whose wall thickness is 2.5 mm. On the outside of the tube, water coolant flows coaxially in an annular space 6.1 mm thick. The coolant velocity is 10 m/s, and it has a local temperature of 15°C. Both flows are approximately fully developed. The pressure of the airstream is around 140 kPa. Estimate the maximum wall temperature of the tube.arrow_forwardWater at 27°C flows with a mean velocity of 1 m/s through a 1 km-long pipe of 0.25 m inside diameter. Answer the following: a. Is the flow hydrodynamically fully developed? Support your answer with calculations. b. Is the flow thermally fully developed? Support your answer with calculations. c. What is the pressure drop over the pipe length, if the pipe surface is smooth? (Ans: 0.289 Bar) d. What is the pump power requirement, if the pipe surface is smooth? (Ans: 1.42 kW)arrow_forward
- When viscous dissipation is appreciable, the energy balance of a convective system must include the viscous effects of the fluid, so a third term is added to the energy balance: A slide bearing (pillow block) can be idealized as a static plate and a plane that moves parallel to it. The rotary axis of such a system has a diameter of 100 mm and rotates at 3600 rpm inside the bearing, which has a gap between the plates of 0.5 mm. The system is lubricated by oil, with a density of 800 kg / m, a viscosity of 0 01 kg / ms and a thermal conductivity of 0:14 W / mk. The top and bottom surfaces of the bearing are at 60 ° C. Considering the viscous effects of the oil, determine a) The maximum temperature of the oil. FC b) Bottom plate heat flux per unit length W / m Write down all assumptions madearrow_forwardConsider 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 iarrow_forwardWrite legibly, provide manual step by step solution, and diagram for below given problem. At an average temperature of 110°C, hot air flows through a 5m pipe with outside diameter of 80mm and pipe thickness of 1cm. The temperature of the tube along its entire length is 240°C. If heat transfer if 650 W, find the convective film coefficient, W/m² - C.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning
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