DYNAMIC ANALYSIS OF DOUBLE-PIPE HEAT-EXCHANGERS SUBJECTED TO PERIODICINLET TEMPERATURE DISTURBANCES

A mixed lumped-differential formulation is employed to model the trans ient energy equations for fully developed laminar-laminar or laminar-t urbulent flow situations in concurrent or countercurrent double-pipe h eat exchangers. The temperature distribution in the outer annular chan nel is radially lumped, providing a more general boundary condition fo r the inner channel differential energy equation, coupled through the interface condition. The case of periodically varying inlet temperatur es is more closely considered, and the dynamic response of the exchang er is established in terms of the governing dimensionless parameters, such as heat capacity flow rate ratio, dimensionless inlet temperature oscillation frequency, and relative wall thermal resistence. The idea s in the generalized integral transform technique are extended to yiel d analytical solutions to the related periodic problem defined in the complex domain, and offer highly accurate numerical results for quanti ties of practical interest, such as fluids bulk temperatures.