Novel evaporator architecture with entrance-length crossflow-paths for supercritical Organic Rankine Cycles

•Introduced new multi-scale heat exchangers based on thermal entrance length flow paths.•Estimated the cost of newly designed heat exchangers by considering surface area and pumping power.•Identified low-cost configurations of new heat exchangers (HX) based on non-isothermal model.•Cost per heat load of new HXs is lower by 20–26% than that for lowest cost shell-and-tube.•Total cost of new HXs is lower by 15–30% than that for lowest cost shell-and-tube. In this paper, a novel geometry is proposed for evaporators that are used in Supercritical Organic Rankine Cycles. The proposed geometry consists of successive plenums at several length-scale levels, creating a multi-scale heat exchanger (HX). The channels at the lowest length-scale levels were considered to have their length determined by the thermal entrance-length. Numerical simulations based on turbulent flow correlations for supercritical R134a and water were used to evaluate the performance of heat exchangers. Using the data on pumping power and area of heat exchange, the total present cost was evaluated using a cost model for shell-and-tube heat exchangers. With respect to the shell-and-tube baseline case, the cost per heat load and total costs of new HXs is lowered by approximately 20–26% and 15–30%, respectively. This reduction in present costs of the new HXs were found to be attributed to higher operational costs for the shell-and-tube HXs, as evidenced by the higher pumping power, as well their capital investment costs. The cost savings in the new HX designs compared to those of the shell-and-tube HXs, at similar heat load performance, indicate that the new HX architectures proposed in this paper are valid alternatives to traditional HX designs.