Modeling of MEMS-type Rankine cycle machines

Preliminary design and performance calculations for a silicon-based micro Rankine machine are discussed. The designs considered draw heat from a high temperature air stream with inlet temperatures between 770 and 1000 K and reject heat to an ambient air stream at 300 K. Most of the designs have a typical footprint of 6 cm(2). Water and benzene are considered as working fluids. Effects of the limits of heat exchanger and turbomachinery performance are analyzed and discussed. The designs of two types of heat exchangers (hole type and fin type) are described in detail. Their respective performances are compared. The calculations indicate that a machine with a 6 cm(2) footprint area is capable of delivering in excess of 40 W of shaft power.