MEE 4071: Thermal Systems Design Assignment #1 (Due Date: Monday, Sept 9, 2019) 1. Consider a concentric tube heat exchanger. Assuming there is no fin attached to any of the surfaces and considering negligible fouling, what would be the appropriate equation for calculating the overall heat transfer coefficient? Briefly describe each term in this equation. 2. How does fouling affects the performance of a heat exchanger? How would you incorporate the effect of fouling in the equation for the overall heat transfer coefficient? 3. A double-pipe heat exchanger is constructed of a copper (k=380 W/m °C) inner tube of internal diameter Di=1.2 cm and external diameter Do = 1.6 cm and an outer tube of diameter 3.0 cm. The convection heat transfer coefficient is reported to be hi=700 W/m2 °C on the inner surface of the tube and ho=1400 W/m2 °C on its outer surface. For a fouling factor R" = 0.0005 m2 °C/W on the tube side and Ro -0.0002 m2 °C/W on the shell side, determine (a) the thermal resistance of the heat exchanger per unit length and (b) the overall heat transfer coefficients Ui and Uo based on the inner and outer surface areas of the tube, respectively. 4. A long double-pipe heat exchanger (with negligible wall thickness) with tube and shell diameters of 1.0 cm and 2.5 cm, respectively, is used to condense refrigerant 134a by water at 20°C. The refrigerant flows through the tube, with a convection heat transfer coefficient of h, -5000 W/m² °C. Water flows through the shell at a rate of 0.3 kg/s. Determine the overall heat transfer coefficient of this heat exchanger. 5. A steel tube (k = 50 W/m.K) of inner and outer diameters D₁ = 20 mm and D.= 26 mm, respectively, is used to transfer heat from hot gases flowing over the tube (h=200 W/m²K) to cold water flowing through the tube (h. = 8000 W/m²K). What is the cold-side overall heat transfer coefficient U.? To enhance heat transfer, 16 straight fins of rectangular profile are installed longitudinally along the outer surface of the tube. The fins are equally spaced around the circumference of the tube, each having a thickness of 2 mm and a length of 15 mm. What is the corresponding overall heat transfer coefficient U.?