In a particular application involving airflow over a heated surface, the boundary layer temperature distribution may be approximated as
where y is the distance normal to the surface and the Prandtl number,
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Fundamentals of Heat and Mass Transfer
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Introduction to Heat Transfer
- To good approximation, the thermal conductivity k of a gasdepends only on the density ρ ,mean free path l , gas constant R , and absolute temperatureT . For air at 20 8 C and 1 atm, k ≈0.026 W/(m.K) and l ≈6.5 E-8 m. Use this information to determine k for hydrogenat 20 ° C and 1 atm if l ≈ 1.2 E-7 m.arrow_forwardFLUID MECHANICS NEED URGENT HELParrow_forwardThe continuity equation of fluids describes the property of energy conservation; and Bernoulli's equation indicates conservation of mass. Ture OR Falearrow_forward
- An oil preheater consists of a single tube of 10 mm diameter and 30 m length. The first half of the tube is heated by a heat rate per unit length of q' = ax2 [W/m], where a = 5 W/m³, and the second half is well insulated. Before entering the tube, the oil has a uniform temperature of 25 °C and a flow rate of 0.0125 kg/s. The hydrodynamic boundary layer has been fully developed. (a) Determine the type of flow (laminar or turbulent) inside the tube. (b) Determine the location where the thermal boundary layer is fully developed. (c) Calculate the mean fluid temperature at the tube exit, Tmo. Properties of the oil: p = 865.8 kg/m³ = 2035 J/kg K, u = 8.36×102 N⚫s/m², k = 0.141 W/mK, a=0.8×107 m²/s, and Pr-1206.6.arrow_forwardDimensional analysis concept applied herearrow_forwardPravinbhaiarrow_forward
- The properties of mercury at 300 K are Density = 13529 kg/m³. c = 0 1393 kJ/kgk dynamic viscosity = 0 1523 x 102 Ns/m² and thermal conductivity = 8 540 W/mK . What is the Prandtl number of the mercury at 300 K?arrow_forwardThe data listed below is from a passenger hot air balloon. The balloon is designed to lift 10-people (80 kg each person). The balloon consists of a basket, a burner- propane tank system. It will lift up when the cold air trapped inside warms up by the burner. Density of air inside the balloon is 99°C: 0.9486 kg/m³, density of air outside balloon is 20°C (ambient): 1.2041 kg/m³ Mass (kg) Balloon Basket Burner Propane tank 113.4 kg 63.5 kg 22.7 kg 183.7 kg Assume the balloon is a sphere shape, volume =(4/3)pi R3. a. Determine the minimum diameter of the balloon that would have a total lifting force to balance the weight of balloon, basket, burner, propane tank and 10 people? b. If the balloon is converted to survey the weather, it will be filled with hydrogen gas (H2). Assume the weight of the people (800kg) is now replaced by onboard equipment, what is minimum diameter needed to keep it afloat at 18km above the surface of the earth?arrow_forwardՁ Ա 12h fluid with f. **>x u Figure 1: Parallel Plates, top plate moving to the right at 2U and the bottom plate moving to the left at U. / ני ди suly)=? Figure 2: Angled Plate with a free surface 3. Figure 1 shows two infinite parallel plates separated by a distance 2h where the top plate is moving at a velocity 2U to the right and the bottom plate is moving to the left at a speed U. Noting that the coordinate system starts at the midpoint between the plates find the following: (a) Use continuity and boundary conditions to show v = 0 everywhere. (b) Derive the velocity profile u (y) using Navier-Stokes Equation. (c) At what position between the two plates is u (y) = 0?arrow_forward
- Q5/A 400 m² light-colored swimming pool is located in a normal suburban site, where the measured wind speed at 10 m height is 2 m/s. The water temperature is 25 °C, the ambient air temperature is 10 °C, and relative humidity is 60%. There are no swimmers in the pool, the temperature of the make-up water is 20 °C, and the solar irradiation on a horizontal surface for the day is 15 MJ/m2-d. Neglect heat losses due to evaporation and radiation. How much energy must the solar system supply (Qss) to the pool to keep its temperature to 25 °C? Take: a = Solar absorptance (a = 0.85 for light-colored pools; a = 0.90 for dark colored pools).arrow_forwardAir flows over a flat plate at 38 m/s, 25°C and 1 atm pressure. The kinematic viscosity of air at 25°C is ν = 1.562 × 10−5 m2/s. What plate length should be used to achieve a Reynolds number of 1 × 108 at the end of the plate? (Round the final answer to two decimal places.)arrow_forwardIs the pi group 4 already an acceptable form or answer or do you always have to modify it into the Reynold's number?arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning