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Free convection heat transfer is sometimes quantified by writing Equation 4.20 as
An experiment for the configuration shown yields a heat transfer rate per unit length of
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Fundamentals of Heat and Mass Transfer
- Saved Help Required information Sometimes equations can be developed and practical problems solved by knowing nothing more than the dimensions of the key parameters. For example, consider the heat loss through a window in a building. Window efficiency is rated in terms of R value, which has the unit of ft2-hr-°F/Btu. A certain manufacturer offers a double-pane window with R=2.5 and also a triple-pane window with R= 3.4. Both windows are 3.5 ft by 5 ft. On a given winter day, the temperature difference between the inside and outside is 45°F. Assume that a homeowner buys 20 such triple-pane windows for the house. A typical winter equals about 120 heating days at AT = 45°F. Each triple-pane window costs $85 more than a double-pane window. Ignoring interest and inflation, how many years will it take the homeowner to make up the additional cost of the triple-pane windows from heating bill savings? years Save & Exit Subm Check my workarrow_forwardPLEASE BOX YOUR ANSWERS Problem 2 In an experiment conducted in a laboratory, the surface tension (Y) acting on a rotating square plate in a viscous fluid is a function of the external torque (t), plate length (a), area moment of inertia of plate (I), specific weight of the fluid (Y) and angular displacement of the plate (0). Using Buckingham-Pi theorem, find a suitable set of pi terms (in M, L and T primary dimensions). Your final answer should be written in proper functional form. Refer Table 5.1/ page-296 for secondary dimension of the variables.arrow_forwardThermal diffusivity is a(A) Function of temperature(B) Physical property of a substance(C) Dimensionless parameter(D) All of thesearrow_forward
- Example(1-13): steam and water flow through 75 mm inside diameter pipe at flow rate of 0.05 and 1.5 m³/s respectivily. If the mean temperature and pressure are 330 K and 120 kpa, what is the pressure drop per unit length of pipe. Where the pipe roughness 0.00015 mm, liquid and gas viscosities are 0.52x10³ pa.s and 0.0133x10-³ pa.s.arrow_forwardthe title of the book: Engineering Thermofluids Thermodynamics, Fluid Mechanics, and Heat Transfer by: Mahmoud Massoudarrow_forwardQ5) For laminar free convection from a heated vertical surface, the local convection coefficient may be expressed as hy = Cxx-1/4, where h, is the coefficient at a distance x from the leading %3D edge of the surface and the quantity C, which depends on the fluid properties, is independent of x. Obtain an expression for the ratio hx/hx, where x is the average coefficient between the leading edge (x = 0) and the x-location. Sketch the variation of h, and h, with x.arrow_forward
- SOLVE STEP BY STEO IN DIGITAL FORMAT A horizontal tube 6 m long and 123.5 cm in diameter is maintained at a temperature of 150 °C in a large room in which the air is at 20 "C and 8 W/m² "C The walls of the room are at 38 °C Assume that the emissivity of the tube is 0.76. How much heat is lost from the tube by both convection and radiation?arrow_forwardOne model of the glomerular membrane is a microporous membrane in which right cylindrical porespenetrate all the way through the membrane. Assume that the pores have a length of 50 nm and aradius of 3.5 nm. The viscosity of plasma is 0.002 Pa s. The average hydrostatic pressure in theglomerulus is 60 mm Hg, hydrostatic pressure in Bowman’s space is 20 mm Hg and the averageoncotic pressure of glomerular capillary blood is 28 mm Hg.A. Calculate the flow through a single pore assuming laminar flow (use the Poiseuille flowequation).B. How many pores would there have to be to produce a normal GFR?C. If the total aggregate area of the kidneys for filtration is 1.5 m2, what is the density of thepores (number of pores per unit area)D. What fraction of the area is present as pores?arrow_forwardall of the How much thermal energy is required to heat at water in a swimming pool by 1°C if the dimensions are 4 ft deep by 20 ft wide by 75 ft long? Report your result in megajoules.arrow_forward
- Both ends of a 32 cm long rod are maintained a constant temperature of 100 °C. Dimensions and thermal parameters of the rod are as follows: Diameter D = 2 cm Convection coefficient h = 10 W/m2K Ambient temperature T¥ = 20 °C Thermal conductivity k = 10 W/mK What is the midpoint temperature of the rod?arrow_forwardA 1:7 scale model simulates the operation of a large turbine that is to generate200 kW with a flow rate of 1.5 m3/s. What flow rate should be used in the model, andwhat power output is expected?(a) Water at the same temperature is used in both model and prototype.(b) The model water is at 25°C and the prototype water is at 10°C.arrow_forwardThe continuity equation of fluids describes the property of energy conservation; and Bernoulli's equation indicates conservation of mass. Ture OR Falearrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning