Investigation of Some Heat Transfer Surfaces for Gas Turbine Recuperators

Abstract: A part of this thesis has been devoted to present general recuperator technology such as available gas turbine recuperator types, applications where recuperators are utilized, recuperator materials etc. An investigation of some compact and highly efficient heat transfer surfaces, for intended use in gas turbine recuperators, include the following surfaces: · Cross Wavy (CW) primary surface. · Corrugated Undulated (CU) primary surface. The CU surface is a relatively new surface which is projected for use in air preheaters · Cross Corrugated (CC) primary surface. The CC surface is familiar from the process industry (often called chevron type or herring bone pattern) but is so far not used in any commercially available gas turbine recuperator · A plate-fin type configuration, called the off-set strip fin is. The method of Computational Fluid Dynamics (CFD) has been used for prediction of thermal performance and pressure losses of the CU and CW surfaces above. In this thesis a specific variant of the CW surface has been considered, called the Trapezoidal Cross Wavy (TCW) surface. This surface may be used in applications having larger hydraulic diameter than the small dimensions used in modern gas turbine recuperators. Design calculations of a recuperator heat transfer matrix were performed using configurations of the above surface types for a specific 50 kW microturbine. In these calculations the hydraulic diameter is equal for all configurations enabling comparison of the thermal and hydraulic performances of the surfaces. The results are presented as heat transfer matrix volumes and weights. The CC surface configurations give the smallest volume and weights of the heat transfer matrix for the specific microturbine recuperator. The straight corrugations of the CC surface should also be easier to fabricate by a stamping, pressing or folding process. It is concluded that the CC surface has potential to give a smaller volume and weight of a recuperator than any commercially available unit today.