Heating and cooling with miniature impinging jets has been proposed for numerous applications. For a single round jet, determine the minimum jet diameter for which Equation 7.71 may be applied for air at atmospheric pressure (a) at
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- 10A.5. Free convection velocity. (a) Verify the expression for the average velocity in the upward-moving stream in Eq. 10.9-16. (b) Evaluate 3 for the conditions given below. (c) What is the average velocity in the upward-moving stream in the system described in Fig. 10.9-1 for air flowing under these conditions? Pressure Temperature of the heated wall Temperature of the cooled wall Spacing between the walls Answer: 2.3 cm/s T3=0°F. Wall 1 atm 100°C 20°C 0.6 cm -T₂ = 61°F Surface temperatures -T₁ = 69°F of plastic panel Plastic panel has thermal conductivity k = 0.075 Btu/hr. ft. °F (average value between T₁ and T₂) -0.502" Fig. 10A.6. Determination of the thermal resistance of a wall. Problems 321arrow_forward11B.6. Transpiration cooling in a planar system. Two large flat porous horizontal plates are sepa- rated by a relatively small distance L. The upper plate at y = L is at temperature T₁, and the lower one at y = 0 is to be maintained at a lower temperature To. To reduce the amount of heat that must be removed from the lower plate, an ideal gas at To is blown upward through both plates at a steady rate. Develop an expression for the temperature distribution and the amount of heat qo that must be removed from the cold plate per unit area as a function of the fluid properties and gas flow rate. Use the abbreviation = pCpv,L/k. Answer: edy/Let 1-e k(T₁ - To) Φ L T-TL To - TL Problems 365 ; 9⁰ =arrow_forwardA long, cylindrical, electrical heating element of diameter D = 14 mm, thermal conductivity k = 251 W/m ⋅ K, density ρ = 2,805 kg/m3, and specific heat cp = 903 J/kg ⋅ K is installed in a duct for which air moves in cross-flow over the heater at a temperature and velocity of 30°C and 9 m/s, respectively. (a) Neglecting radiation, estimate the steady‐state surface temperature when, per unit length of the heater, electrical energy is being dissipated at a rate of 1,033 W/m.arrow_forward
- Hand Sanitizer (70% propanol gel) needs to be transported on a floor in a hospital from a central location per floor. The room farthest from the source is 17.5-m away. The hand sanitizer enters the tubing at 20°C and 275 kPa absolute and exits the tubing at atmospheric conditions. The tubing can Flowrate/velocity Calculation. Hand sanitizer be considered smooth; however, there are two (2) 90° curved elbows and four (4) Tee Run throughs, and one (1) foot value (Refer to the Loss for Fittings table in Canvas). The density of the hand sanitizer is 955 kg/m3 and the viscosity is 4.5 cP. What is the flow rate that can be obtained if the tubing diameter is 4.5-mm?arrow_forwardA heat treat steel plate measures 3 m *1 m and is initially at 30 degree Celsius. It is cooled by blowing air parallel to 1 m edge at 9 km/hr. If the air is at 10 degree Celsius. Estimate the convective heat transfer from both sides of the plate.arrow_forwardShow all working explaining detailly each step. Answer Qb(i), (ii) & (iii)arrow_forward
- A long, cylindrical, electrical heating element of diameter D = 12 mm, thermal conductivity k = 240 W/m ⋅ K, density ρ = 2,856 kg/m3, and specific heat cp = 908 J/kg ⋅ K is installed in a duct for which air moves in cross flow over the heater at a temperature and velocity of 30°C and 10 m/s, respectively. (a) Neglecting radiation, estimate the steady‐state surface temperature when, per unit length of the heater, electrical energy is being dissipated at a rate of 1,238 W/m.arrow_forwardShow your complete solution.arrow_forward6.64 Consider application of the naphthalene sublimation technique (Problem 6.63) to a gas turbine blade that is coated with naphthalene and has a surface area of A, = 0.05 m². Airflow V,T_ - Turbine blade with naphthalene coating A., T., P. (T₂) To determine the average convection heat transfer coef- ficient for a representative operating condition, an experiment is performed in which the coated blade is exposed for 30 min to atmospheric air at the desired velocity and a temperature of T = 27°C. During the experiment the surface temperature is T. = 27°C, and at its conclusion the mass of the blade is reduced by Am = 8 g. What is the average convection heat transfer coefficient associated with the operating condition?arrow_forward
- Solve it correctly please. I will rate accordingly with 3votes.arrow_forwardO. Air with free stream temperature of 10 C is flowing over a flat plate (1.5m long and Im wide). The air is flowing along 1.5m side of the plate. The plate is maintained at 90'C. Find the velocity of air required to have a rate of heat dissipation as 3.75 kW. Use the correlations: Nu =0.664Reos Pro33 for laminar flow Nu, = (0.037RE-871)Pr3 for turbulent flow Take the properties p = 1.0877 kg/m u=2.029×10 m/s, k=0.028 W/mK, C,-1.007KJ/kg.K and Pr-0.703arrow_forwardConsider two cases involving parallel flow of dry air at V = 4.5 m/s, T, = 45°C, and atmospheric pressure over an isothermal plate at T = 20°C. In the first case, Re= 5x 105, while in the second case the flow is tripped to a turbulent state atx = 0 m. At whatx -location, in m, are the thermal boundary layer thicknesses of the two cases equal? What are the local heat fluxes, in W/m?, at this location for the two cases? x = i m Jam i W/m? i W/m? I turbarrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning