1. A 1 m long flat plate is heated with an electrical heater which supplies a uniform heat flux. Air at 25°C is flowing over the surface with a velocity 50 m/s. Plate surface temperature at x = 0.1 m is measured as: Tr = 71°C.
a. Calculate the heat flux from the surface.
b. Calculate the surface temperature at x = 1 m.
Use the following properties of air for calculations: v = 1876 x 10-5 m2/s, k = 0.0284 W/(mK), Pr = 0.703.
2. We want to design a heat exchanger using 7 tubes per row in the direction perpendicular to the flow (NT = 7) due to space requirements. The heat exchanger will use an aligned arrangement of 40-mm diameter tubes with ST - SL = 80 mm and a tube length of 1 m. Water with approach temperature T = 14oC and velocity 1 m/s flows over the tubes. Wall temperature of the tubes is 100°C due to steam condensation inside the tubes. The properties of water at an assumed mean temperature arc given as: p= 993 Kg/m3, μ = 695 x 10-6 Ns/m2, k = 0.628 W/(mK), v = 7 x 10-7 m2/s, e = 4.178 KJ/(KgK), Pr = 4.62. Make sure to use a correlation that fits given properties.
If it is expected that NL > 20 rows, what is the average heat transfer coefficient?
If the average heat transfer coefficient is 1.429 x 104 W(m2K), and if we want the temper-mare of the water leaving the tube bank to be 60oC, how many rows of tubes In the flow direction should be used?