The Key Role of Heat Exchangers in Closed Brayton Cycle Gas Turbine Power Plants

Abstract

In the power generation field, simple cycle gas turbines are dominant, with heat exchanged variants only selected based on particular user’s requirements. For the lesser known closed Brayton cycle (CBC) power plant, heat exchangers are mandatory. The following three categories of heat exchangers are addressed in this paper, 1) heat input to the closed cycle from an external source; for example the heat exchanger in a fluidized bed combuster in the case of a fossil-fired plant, or an intermediate heat exchanger (IHX) in the case of an indirect cycle nuclear gas turbine, 2) recuperator in the system to enhance efficiency, and 3) exchangers (i.e., precooler and intercooler) for heat rejection from the system. The influence that these heat exchangers have on the selection of system parameters, and plant performance is discussed. Heat exchanger technology state-of-the-art for CBC systems is highlighted.

Perspective on a Combustion-Free Gas Turbine to Meet Power Generation Needs in the 21st Century

“…A key factor in the realization of plant efficiencies approaching 50 percent,is the utilization of high effectiveness heat exchangers.Because of the large heat transfer areas required it is necessary to utilize compact plate-fin geometries (McDonald 1996f) for integration in the volume-limited steel pressure vessel. , Flow passages with much smaller hydraulic diameters than used in recuperators for combustion gas turbines are necessary, and a development effort is needed to provide data for the design of the heat exchangers in the demonstration plant.With very small passage heights and a dense fin count,the first step will be to demontrate that clean burr-free geometries can be fabricated.Small scale samples of the brazed matrix will be used to generate basic heat transfer and friction data.Modules embodying the matrix and headering will be tested to investigate the effects of flow maldistribution.Since the units have an internal pressure differential much higher than in existing plate-fin units,thermal/pressure cycling tests will be necessary to confirm their structural integrity at elevated temperature.…”