Supercritical Fluid Carnot Cycle for Low Temperature Waste Heat Utilization

Supercritical Fluid Carnot Cycle for Low Temperature Waste Heat Utilization

Many chemical processes reject low-grade heat to the environment. While it is difficult to recover low temperature waste for work production, it would be useful to design processes that, in principle, could do this. In our presentation we describe computer simulations of a process for doing this using supercritical carbon dioxide as a working fluid for the power cycle. Given the low critical temperature of carbon dioxide and the desirability of keeping the working fluid in its one phase region, CO₂ is an ideal fluid for designing such a process. Using a temperature close to its critical point for the rejection leg of the Carnot cycle, we exploit the natural flattening of the critical isotherm in this region which leads to efficient work production in Carnot engines using small temperature driving forces between the input and rejection legs of the process. The concepts appear promising as a basis for designing experimental systems for recovering low- grade waste heat for conversion into work using supercritical CO2 as the power cycleÕs working fluid.