An isothermal silicon chip of width W = 20 mm on a side is soldered to an aluminum heat sink (k = 180 W/m-K) of equivalent width. The heat sink has a base thickness of Lb = 3 mm and an array of N = 11 rectangular fins, each of length Lf =15 mm and thickness t = 0.182 mm. The fin pitch is S= 1.982 mm. Airflow at To = 20°C is maintained through channels formed by the fins and a cover plate, and the flow is such that a convection coefficient of h = 100 W/m2-K is maintained on all surfaces of the fins. The solder joint has a thermal resistance of R" = 2x10-6 m2-K/W. How much thermal energy is dissipated 't,c away from the chip when the chip is at its maximum allowable temperature of Tc = 85°C? An adiabatic fin tip condition may be assumed, and airflow along the outer surfaces of the heat sink may be assumed to provide a convection coefficient equivalent to that associated with airflow through the channels. Chip, T. Ic Solder. R"

A gas at 525 ° C flows through an AISI 316 stainless steel pipe (d.i = 94 mm and d.o. = 100 mm). The pipe is covered with a covering of mineral wool granules with 35 mm thick asbestos binders. The pipe is exposed to ambient air at 25 ° C. The heat transfer coefficients for the surrounding gas and air are 29 W / (m2 K) and 12W / (m2 K), respectively. Do the following: (a) Draw a schematic diagram and the thermal resistances of the scheme b) Calculate the critical radius and indicate if the coating increases or decreases heat transfer c) Calculate the heat loss per meter of tube length with the covering. d) Estimate the temperature on the surface of the coating exposed to the environment

Water flows in a duct having a cross-section of 10x20 mm with a mean bulk diameter of 15.56 deg C. If the duct wall temperature is constant at 60 deg C and fully developed laminar flow prevails. a.) Calculate the heat transfer coefficient, h in W/m2-deg Cchoices: (405, 305, 151, 252) b.) What is the thermal conductivity of water at the given temperature, k in W/m-deg Cchoices: (0.604, 0.6, 0.585, 0.595) c.) Calculate the heat transfer rate per unit length in W/mchoices; (605, 366, 505, 404)

Refrigerant-134a is being transported at 0.08 kg/s through a Teflon tube of inside diameter D; = 20 mm and outside diameter Do = 25 mm, while atmospheric air at V = 28 m/s and 300 K is in cross flow over the tube. What is the heat transfer per unit length of tube, in W/m, to Refrigerant-134a at 230 K? q' = i W/m Use Hilpert correlation to estimate the external heat transfer coefficient, and please state ALL assumptions.