Upper bound on the rate of entropy increase accompanying noise power flow through linear systems

An upper bound is established for the rate of entropy increase due to noise power flow in a nonisothermal linear network containing n independent noise sources. The bound depends on the net power flows to (or from) the noise sources collectively, the lowest noise temperature in the network, and the efficiency of a Carnot heat engine operating between the highest and the lowest noise temperature occurring in a system. The author´s example demonstrates that for a two port, the upper bound is actually reached and therefore a tighter bound cannot be found in general. Based on this example, a previously published bound is interpreted as the statement that the rate of entropy increase in the given n-port system cannot exceed that in a two port, in which the terminations are at the maximum and the minimum temperatures and the power flow equal the net value