Micro turbines are gaining in importance as the future option for distributed generation. To make this option viable the present efficiency levels, which are low, have to be raised, without deteriorating the cost factor. For this a cost effective design of heat exchangers is imperative. For the gas to gas exchangers for micro turbines three options of plate-fin cross-flow, plate-fin counter-flow and rotary regenerator have been considered. Design of a cross flow plate fin recuperator with offset strip fins has been carried out for a micro turbine. The gas and air side pressure drops have been varied over the span of 1% to 5% of inlet pressure. The main issue with counter flow exchangers is the intricacies of header design. But the future trends are for thermodynamically superior counterflow heat exchangers with innovative header design and use of all primary surface heat exchangers. A recuperator design with counterflow has been carried out to demonstrate the effect of free flow area ratio and its advantage on compactness over cross flow design.

Design of a rotary regenerator has been carried out in the second part of the project. The effects of variables such as rotation, pressure leakage and heat exchanger pressure drop on the design and dimensions of the heat exchangers have been presented. Pressure drops over 1% to 5% range, Cr* from 1.0 to 8.0 and pressure leakage from 5 to 10 % have been varied for a parametric study of these variables on the design of the heat exchanger.

For the design of both types of heat exchangers Effectiveness-NTU approach has been followed using typical operating parameters for a 50 kW Micro turbine. Design codes developed in C++ have been validated by using input data and corresponding results from literature.

Keywords: Effectiveness, Geometrical Parameters, NTU, Rotary Regenerator Pressure drop, Temperature correction.