Abstract
It is shown that certain tubular processes with varying flow rate and with performance criterion based on the output variables of the systems can be transformed into integral equation systems with time-varying delay. Necessary conditions for the optimization of a class of integral equation systems with time-varying delay are derived by use of variational technique. Steepest-descent method of control variable iteration is derived. Computational results are then given for the programming control of a wall temperature forced tubular heat exchanger with varying flow rate.