heat and mass transfer (20 points) Air at 25°C cools a 2170 cylindrical battery (with a diameter of 21 mm and a length of 70 mm) with a cross flow velocity of 6 m/s. a) Determine the average conv...
A long cylindrical rod of diameter 220 mm with thermal conductivity 0.5 W/m-K expe riences uniform volumetric heat generation of 25,000 W/m3. The rod is encapsulated by a circular sleeve having 7 W/m K. The outer surface of the sleeve is exposed to cross flow of air at 25°C with a convection coefficient of 25 W/m2-K. Find the temperature at the interface between the rod and sleeve, and on the outer surface. an outer diameter of 410 mm and thermal...
Problem 3 (25 points) In an experiment to find the convective heat transfer coefficient, an internally heated cylindrical electric heater is placed in the path of a cross-flow of air. The air is at 27C moving with a velocity of 10m/s. The heater has dimensions of diameter 15mm, length-90mm, and dissipates a power of 50W. The average surface temperature of the heater is 127°C. Determine: a) The convective heat transfer coefficient using the data provided. b) The convective heat transfer...
A long cylindrical rod of diameter 100 mm with thermal conductivity of 0.5 W/mK experiences uniform volumetric heat generation of 5.0 x 10 W/m². The rod is encapsulated by a circular sleeve having an outer diameter of 400 mm and a thermal conductivity of 4 W/mK. The outer surface of the sleeve is exposed to cross flow of air at 27°C with a convection coefficient of 25 W/m2K (a) Find the temperature at the Interface between the rod and sleeve...
6 Water is heated in a pipe by exchanging heat with a warmer fluid that flows outside the pipe. Inside diameter of the pipe is dn 0.045 m and outside diameter dour0.05 m. Mean velocity of the water in the pipe is um-0.31 m/s and the bulk temperature is 323 K (density 988 kg m-3; viscosity 0.00055 kg m' sı. Pr 3.56, thermal conductivity k 0.64 W m1 Kt). The material of the pipe has thermal conductivity k 0.61 W...
III. Convective coefficient (40 pt). An electric wire having diameter of 6.0 mm and covered with a plastic insulation (thickness 2.0 mm; thermal conductivity: 0.4 W/m K) is exposed to air at 300 K. The heat loss per meter of wire generated is 200 W/m. Determine: ) Convective heat-transfer coefficient between the insulation and the surrounding air, h (25 pt) 2) Temperature of the insulation surface T2. (15 pt) HINT: T2 is a value between 320K and 400K To T2...
G4 Problem Statement: Circular fins of uniform cross section, with diameter of 14 mm and length 70 mm are attached to the wall with surface temperature o C. The fin is made of material with thermal conductivity of 210 W/mk, and exposed to an ambient air condition of 24 °C and the convection heat transfer coefficient of 190 W/m2k. f 300 1- Plot the temperature variation for the following boundary conditions a- Infinitely long fin b- Adiabatic fin tip c-...
A 70-mm diameter hot solid rod is suspended in a room in which the air and walls are at 25°C., The surface temperature of the rod and its emissivity are 200°C and 0.8, respectively. The associated coefficient of convective heat transfer from the rod surface to the air is 15 W/m2.K. If the total heat loss from the surface area of the rod is estimated to be 947 W, what is the length of the rod? Area of both sides of the...
Problem 3 (20 points) A cross-flow heat exchanger consists of a bundle of 32 tubes in a long duct. Hot water at 150°C and a mean velocity of 0.5 m/s enters the tubes having inner and outer diameters of 10.2mm and 12.5mm and has to be cooled to 136°C. The tubes are made of steel of thermal conductivity k-40 W/m.K. Air at 10°c enters the exchanger (unfinned) with a volumetric flow rate of 1.0 m3/s. The convective heat transfer coefficient...
part b only please8.12 Dry, compressed air at Tm,i 75°C, p- 1o atm, with a mass flow rate of a 30-mm-diameter, 5-m-long tube whose surface is at T, 25°C. 0.001 kg/s, enters (a) Determine the thermal entry length, the mean temperature of the air at the tube outlet, the rate of heat transfer from the air to the tube wall, and the power required to flow the air through the tube. For these conditions the fully developed heat transfer coefficient is...
A 25-mm-diameter hot surface at
is cooled by an air jet exiting a 5-mm-diameter round nozzle with
a velocity of 35 m/s and temperature of 25. The
nozzle exit is 25 mm from the hot surface. Determine the percentage
change in average heat transfer coefficient at the hot surface if
the air is replaced with carbon dioxide or helium. Use material
properties from reputable tables.
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