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A shell-and-tube heat exchanger with one shell pass and 20 tube passes uses hot water on the tube side to heat oil on the shell side. The single copper tube has
inner and outer diameters of 20 and 24 mm and a length per pass of 3 m. The water enters at 87°C and 0.2 kg/s and leaves at 27°C. Inlet and outlet temperatures of the oil are 7 and 37°C. What is the average
convection coefficient for the tube outer surface?

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A concentric tube heat exchanger of length L = 2m is used to thermally process a pharmaceutical product flowing at a mean velocity of um,c = 0.1 m/s with an
inlet temperature of Tc,i =20°C. The inner tube of diameter Di = 10 mm is thin walled, and the exterior of the outer tube (Do = 20 mm) is well insulated.
Water flows in the annular region between the tubes at a mean velocity of um,h = 0.2 m/s with an inlet temperature of Th,i = 60 °C. Properties of the pharmaceutical
product are nu = 10 x10 6 m2/s, k = 0.25 W/m K, density = 1100 kg/m3, and cp = 2460 J/kg K. Evaluate water properties at T
h =50°C.
(a) Determine the value of the overall heat transfer coefficient U.
(b) Determine the mean outlet temperature of the pharmaceutical product when the exchanger operates in the counterflow mode.
(c) Determine the mean outlet temperature of the pharmaceutical product when the exchanger operates in the parallel-flow mode.

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A furnace with a long, isothermal, graphite tube of diameter D = 12.5 mm is maintained at Tf = 2000 K and is used as a blackbody source to calibrate heat flux gages. Traditional heat flux gages are constructed as blackened thin films with thermopiles to indicate the temperature change caused by absorption of the incident radiant power over the entire spectrum. The traditional gage of interest has a sensitive area of 5 mm2 and is mounted coaxial with the furnace centerline, but positioned at a distance of L = 60 mm from the beginning of the heated section. The cool extension tube serves to shield the gage from extraneous radiation sources and to contain the inert gas required to prevent rapid oxidation of the graphite tube.

(a) Calculate the heat flux (W/m2) on the traditional gage for this condition, assuming that the extension tube is cold relative to the furnace.

(b) The traditional gage is replaced by a solid-state (photoconductive) heat flux gage of the same area, but sensitive only to the spectral region between 0.4 and 2.5 um. Calculate the radiant heat flux incident on the solid-state gage within the prescribed spectral region.

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Helium gas at 25C and 4 bars is contained in a glass cylinder of 100-mm inside diameter and 5-mm thickness. What is the rate of mass loss per unit length of the cylinder? 

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Helium gas at 25C and 4 bars is contained in a glass cylinder of 100-mm inside diameter and 5-mm thickness. What is the rate of mass loss per unit length of the cylinder? 

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Oxygen gas is maintained at pressures of 2 bars and 1 bar on opposite sides of a rubber membrane that is 0.5 mm thick, and the entire system is at 25C. What is the molar diffusive flux of O2 through the membrane? What are the molar concentrations of O2 on both sides of the membrane (outside the rubber)?

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Oxygen gas is maintained at pressures of 2 bars and 1 bar on opposite sides of a rubber membrane that is 0.5 mm thick, and the entire system is at 25C. What is the molar diffusive flux of O2 through the membrane? What are the molar concentrations of O2 on both sides of the membrane (outside the rubber)?

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Estimate values of the mass diffusivity Dab for binary mixtures of the following gases at 350 K and 1 atm: ammonia-air and hydrogen-air

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Estimate values of the mass diffusivity Dab for binary mixtures of the following gases at 350 K and 1 atm: ammonia-air and hydrogen-air

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Resolucion Challenge Dab for binary mixtures (Rudy Riera)

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Resolucion Challenge Dab for binary mixtures (Rudy Riera)

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Beginning with a differential control volume, derive the diffusion equation, on a molar basis, for species A in a one-dimensional, spherical, stationary medium, considering species generation.

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Beginning with a differential control volume, derive the diffusion equation, on a molar basis, for species A in a one-dimensional, spherical, stationary medium, considering species generation.