In the literature of the theory of gas turbine cycles certain views are expressed, which on critical examination can be shown to be incorrect. In particular with cycles incorporating intercooling or reheat the influence of the proportioning of the pressure ratios of the turbo-machines on the cycle efficiency and the specific work is frequently overlooked. Further questions relate to the definition of the performance of the heat exchanger in the Brayton cycle. The heat exchanger is usually

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... d by its effectiveness. However, it will be shown that effectiveness is not a satisfactory criterion of performance. This is particularly the case when changes in other cycle parameters or comparisons between different types of cycles (i.e., simple cycle with intercooled cycle) have to be evaluated. A better criterion is proposed in a parameter which is dependent upon the surface area of the heat exchanger.