HEAT EXCHANGER DESIGN GOALS: u Role of heat exchangers in chemical processing u Basic concepts and terminology u Types of heat exchangers u Design methodology ð Sizing ð Design ð Rating 8/24/99 Heat Exchanger Design 1 PURPOSE OF A HEAT EXHANGER u To Heat or Cool a stream flowing from item of equipment to another. The steam may be a: ð A liquid ð A gas ð A multiphase mixture u To Vaporize a liquid stream u To Condense a vapor stream 8/24/99 Heat Exchanger Design 2 SINGLE TUBE PASS, SINGLE SHELL PASS COUNTERCURRENT HEAT EXCHANGER Shell Side Shell Side Outlet Inlet Nozzle Nozzle Tube Side Tube Side Outlet Inlet Nozzle Nozzle 8/24/99 Heat Exchanger Design 3 TYPES OF HEAT EXCHANGER SERVICE u Fluid heated by external utility ð Steam ð Hot oil or molten salt bustion gas (furnace) ð Electricity (resistive, inductive, microwave) u Fluid cooled by external utility ð Cooling water ð Refrigeration u Fluid heated or cooled by other process stream 8/24/99 Heat Exchanger Design 4 TYPES OF HEATING AND COOLING CURVES Sensible Heat - Heating Sensible Heat - Cooling T (K) ponent Condensation or Vaporization ponent Cooling/Condensation DUTY Q (kJ/s) 8/24/99 Heat Exchanger Design 5 CALCULATION OF COOLING CURVES u Sensible Heat: Q = W Cp (Tin - Tout) (For constant Cp: Q = W (Hin - Hout) otherwise) u Latent Heat: Q = W λ u ponent Cooling Curves: Requires point-by- point flash calculations 8/24/99 Heat Exchanger Design 6 FEASIBLE COOLING CURVE PAIRINGS u Corollary of the Second Law of Thermodynamics: Heat can only be transferred from a higher temperature to a lower one. u For heat exchangers this means that the higher temperature cooling curve and the lower temperature heating curve cannot intersect. u When this condition is satisfied, the pairing of a heating and cooling curve is said to be feasible. 8/24/99 Heat Exchanger Design 7 FEASIBLE COOLING CURVE PAIRINGS T1in T1in Countercurr
