Cascade coolers are a series of standard pipes, usually manifolded in parallel, and connected in series by vertically or horizontally oriented U-bends. Process fluid flows inside the pipe entering at the bottom and water trickles from the top downward over the external pipe surface. The water is collected from a trough under the pipe sections, cooled, and recirculated over the pipe sections. The pipe material can be any of the metallic and also glass, impervious graphite, and ceramics. The tubeside coefficient and pressure drop is as in any circular duct. The water coefficient (with Re number less than 2100) is calculated from the following equation by W.H. McAdams, T.B. Drew, and G.S. Bays Jr., from the ASME trans. 62, 627-631 (1940).
h = 218 * (G'/Do)m (W/m2 °C) (11-82) G = m/(2L) m = water rate (kg/hr) L = length of each pipe section (meter) Do = outside diameter of pipe (meter)
LMTD corrections are per Fig. 11-4 i or j depending on U-bend orientation.
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