A novel heat exchanger concept consists of a large number of extruded polypropylene sheets (k = 0.17 W/m-K), each having a fin-like geometry, that are subsequently stacked and melted together

to form the heat exchanger core. Besides being inexpensive, the heat exchanger can be easily recycled at the end of its life. Carbon dioxide at a mean temperature of 10°C and pressure of 2 atm flows in the cool channels at a mean velocity of u m = 0.1 m/s. Air at 30°C and 2 atm flows at 0.2 m/s in the warm channels. The channel pitch is d = 15 mm. Neglecting the thermal contact resistance at the welded interface, determine the product of the overall heat transfer coefficient and heat transfer area, U A , for a heat exchanger core consisting of 200 cool channels and 200 warm channels. Physical Properties Mathematical Functions What is the hydraulic diameter of each channel, in m? What is the Nusselt number in each hot (air side) channel? What is the hot side convection heat transfer coefficient, in W/m2.K? What is the fin efficiency on the hot side for a fin that is ( d-c)/2 mm long (one half of each channel) with an adiabatic tip(corresponding to the centerline of channel)? What is the overall surface efficiency on the hot side? What is the value of the overall heat transfer coefficient - area product, U A, in W/m2.K?