Analytical solution to the equations for parallel-flow four-channel heat exchangers part 2: Double zero eigenvalue case

An analytical solution to the set of linear differential equations of the first order with constant coefficients describing the heat transport in a parallel-flow four-channel heat exchanger is presented for the case of a double zero eigenvalue of the coefficient matrix of the set. This paper is a continuation of the authorʹs previous work [1] in which the case of simple eigenvalues of the coefficient matrix was analysed.