In a paper-drying process, the paper moves on a conveyor belt at 0.2 m/s, while dry air from an in-line array of round jets (Figure 7.18b) impinges normal to its surface. The nozzle diameter and pitch are
Want to see the full answer?
Check out a sample textbook solutionChapter 7 Solutions
Fundamentals of Heat and Mass Transfer
Additional Engineering Textbook Solutions
Introduction To Finite Element Analysis And Design
Fox and McDonald's Introduction to Fluid Mechanics
Fundamentals Of Thermodynamics
Engineering Mechanics: Dynamics (14th Edition)
Thinking Like an Engineer: An Active Learning Approach (4th Edition)
Statics and Mechanics of Materials (5th Edition)
- Air flows inside a tube 60 mm in diameter (d) and 2.1 m long (l) at a velocity w = 5 m/sec. Find the heat-transfer coefficient α if the mean air temperature tf = 100oC. Note: Write your answer in space provided without the unit (the answer is in kcal/m2-hr-oC, one decimal places)arrow_forwardForced air at T∞ = 25°C and V = 12 m/s is used to cool electronic elements on a circuit board. One such element is a chip, 4 mm × 4 mm, located 153 mm from the leading edge of the board. Experiments have revealed that flow over the board is disturbed by the elements and that convection heat transfer is correlated by an expression of the form Nu_x=0.04Re_x^{0.85}\Pr^{\frac{1}{3}}Nux=0.04Rex0.85Pr31 Estimate the surface temperature of the chip if it is dissipating 32 mW.arrow_forward8. A lead pipe has 2 cm inside diameter, 3 cm outer diameter, length of 130 cm. Liquid water at 4°C flows through the pipe with a bulk velocity of 0.03 km/hr. Air is blown around the outside of the pipe at 20 deg C. The inside wall of the said pipe has a temperature of 8 deg Celsius. Density of liquid water= 1000 kg/m³ Cp water=4.210 J/kgK Viscosity of liquid water= 1.5674 x10° Pa.s thermal conductivity of lead = 35 W/mK thermal conductivity of water = 0.575 W/mK Find: Overall heat coefficient (U) based on outside surface area b. System's heat transfer rate Prandtl (Pr), Reynolds (Re) numbers and type of flow а. с.arrow_forward
- The forming section of a plastics plant puts out a continuous sheet of plastic that is 1.2 m wide and 2 mm thick at a rate of 18 m/min. The sheet is subjected to airflow at a velocity of 4 m/s on both top and bottom surfaces normal to the direction of motion of the sheet. The width of the air cooling section is such that a fixed point on the plastic sheet passes through that section in 2 s. Using properties of air at 1 atm and 60°C, determine the drag force the air exerts on the plastic sheet in the direction of airflow.arrow_forwardConsider parallel flow over a flat plate for air at 300 K and engine oil at 380 K. The free stream velocity is u temperature difference between the surface and the free stream is the same in both cases, with Ts > T (a) Determine the location, in m, where transition to turbulence occurs, xc, for both fluids. 8 X (b) For laminar flow over a flat plate, the velocity boundary layer thickness is given by = layer thickness 6, in m, for x = 1 for each fluid. Part A Determine the location, in m, where transition to turbulence occurs, xc, for both fluids. (c) Determine the thermal boundary layer thickness 6₁, in m, for x = 1 for each fluid. At an x-location where both fluids experience laminar flow conditions, which fluid has the largest temperature gradient at the plate surface, — dT/ dy|y_o? Which fluid is associated with the largest local Nusselt number Nu? Which fluid is associated with the largest local heat transfer coefficient h? y=0 Xc,air = Xc,eo = i m 5 Rex m = 1.6 m/s. The Determine…arrow_forwardThe liquid food is flowed through an uninsulated pipe at 90 ° C. The product flow rate is 0.3 kg / s and has a density of 1000 kg / m³, specific heat 4 kJ / (kg K), a viscosity of 8 x 10-6 Pa s, and a thermal conductivity of 0.55 W / (m) K). Assume that the change in viscosity is negligible. The internal diameter of the pipe is 30 mm with a thickness of 3 mm made of stainless steel (k = 15 W / [m ° C]). The outside temperature is 15 ° C. If the outer convective heat transfer coefficient is 18 W / (m² K), calculate the heat loss at steady state per meter pipe length. a. Find the convection coefficient in pipe = W / m² ° C. b. Calculate heat loss per meter pipe length = wattsarrow_forward
- 5. A fluid enters with a steady flow of 3.7 kg/s and an initial pressure of 690 kPa, and initial density of 3.2 kg/m?, an initial velocity of 60 m/s, and initial internal energy of 2000 kJ/kg. It leaves at a pressure of 172 kPa, density 0.64 kg/m², velocity 160 m/s, and internal energy 1950 kJ/kg. The heat loss is found to be 18.6 kJ/kg. Find the power in kW. A. –36 kW B. +152 kW C. -121 kW D. +68 kWarrow_forward1. Consider a new wind tunnel to test and utilise the effects of boundary layer conditions in order to maintain the velocity of a fluid. Laminar airflow enters a square duct design through a 0.25m² opening, as is shown in Figure 1. Because the boundary layer displacement thickness increases in the direction of flow, it is necessary to increase the cross-sectional size of the duct if a constant U=1 m/s velocity to be maintained outside the boundary layer. Assume standard air temperature in the calculation. U = 1 m/s 0.25 m2 d(x) 1 m/s Figure 1 a) Determine the expression of the duct size, d, in consideration to maintain the velocity outside the boundary layer. b) Plot a graph of the duct size, d, as a function of x for 0arrow_forwardConsider two cases involving parallel flow of dry air at V = 4m/s, T, = 45°C, and atmospheric pressure over an isothermal plate at T, = 20°C. In the first case, Re = 5 x 105, while in the second case the flow is tripped to a turbulent state at x = 0m. At what x -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 W/m? urb W/m? iarrow_forwardA steel ball with a diameter of 10 mm is taken suddenly from a medium at a temperature of 25ºc and annealed for 20 minutes in the furnace host at a temperature of 800ºc. How many ° C is the temperature of the steel ball when it comes out of the oven? (ρ(steel) = 7854 kg / m3, C(steel) = 434 J / kgK, h(air) = 10 W / m2K and h(oil) =100 W / m2K) a. 705.65 b. 662.90 c. 706.25 d. 750.81 e. 750.20arrow_forwardThe liquid food is flowed through an uninsulated pipe at 90 ° C. The product flow rate is 0.4 kg / s and has a density of 1000 kg / m³, specific heat 4 kJ / (kg K), a viscosity of 8 x 10-6 Pa s, and a thermal conductivity of 0.55 W / (m) K). Assume that the change in viscosity is negligible. The internal diameter of the pipe is 20 mm with a thickness of 3 mm made of stainless steel (k = 15 W / [m ° C]). The outside temperature is 15 ° C. If the outer convective heat transfer coefficient is 18 W / (m² K), calculate the heat loss at steady state per meter of pipe length. a.Find the convection coefficient in the pipe = AnswerW / m² ° C. b. Calculate heat loss per meter pipe length = Answerwatt.arrow_forwardAn air flow with velocity u∞ = 2m/s and T∞ = 300K is used to cool the surface of a flat metal plate that is L = 0.5m long, W = 0.5m wide, and H = 0.1m thick. The plate receives a uniform heat flux input of q′′ = 500W/m^2 from the bottom. Assume the plate reaches the steady state and has a uniform surface temperature Ts and bottom temperature Tb. Assume one-dimensional conduction across the plate. For the air flow, the Prandtl number is Pr = 0.7, the kinematic viscosity is ν = 2 × 10^(−5) m^2/s, and the thermal conductivity is kf = 0.03 W/m · K. The solid material of the plate has a uniform thermal conductivity ks = 10 W/m · K.Given correlations for convection heat transfer over flat plate:• For the laminar flow region, the local Nusselt number is Nu = 0.332Re^(1/2)*Pr(1/3) • For the turbulent flow region, the local Nusselt number is Nu = 0.0296Re^(4/5)*Pr(1/3) Questions:(1) Determine the local convection heat transfer coefficient h(x) and the averaged con- vection heat transfer…arrow_forwardarrow_back_iosSEE MORE QUESTIONSarrow_forward_ios
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning