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Unformatted text preview: drops so low that ice forms on the surface of ponds and lakes. If the bulk temperature in a large lake is held constant at 36 oF, and the air temperature is constant at 25 F, find the thickness of the ice layer on a lake assuming steady state heat transfer. Thermal conductivity of ice: k = 1.3 Btu/hr ft F. Heat transfer coefficients: Ice to air (forced convection,wind) h = 5 Btu/hr ft 2 F Ice to water (natural convection) h = 2.5 Btu/hr ft 2 F 4. Hot combustion gases ( C p = 0.38 kcal/kg C) at 825 C are to be used to heat water from 25C to saturated steam at 145C. The mass flow rate of water is 45 kg/s. Heat transfer coefficients (kcal/m 2 hr C): gas, forced convection 55; water, forced convection 300; water, boiling 2800. H v = 530 kcal/kg Find the minimum flow rate of combustion gases. Find the required area of the heat exchanger for a flow rate 35% above this value....
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- Spring '10