Imperial College London


Faculty of EngineeringDepartment of Chemical Engineering

Research Associate







ACE ExtensionSouth Kensington Campus






BibTex format

author = {Chatzopoulou, MA and Sapin, P and Markides, C},
publisher = {ECOS},
title = {Optimisation of off-design internal combustion-organic Rankine engine combined cycles},
url = {},
year = {2018}

RIS format (EndNote, RefMan)

AB - Organic Rankine cycle (ORC) enginesare an efficient means of convertinglow-to-medium renewable orwaste heat to useful power. In practicalapplications, ORC systemsexperience varying thermalinputprofile,due to the dynamic nature of realheat sources. Maximisingthe uptake of this technology requiresoptimisedORC designsand sizing tomaintain high efficiencyand power output,not only at full-load operation, but also under off-design conditions. Key for maintaining the efficient operationof the systemis the maximisation of heat extraction from the heat source, inthe ORC evaporator. In this paper, the off-design operation of an ICE-ORC combined heat and power (CHP) system is investigated, to optimise the ORC performance under varying ICE load conditions. First, the ORC enginethermodynamic design is optimised for the 100% load operation of the ICE. Alternative working fluids are investigated, including low ODP/GWP refrigerants and hydrocarbons. The ORC system is then sized using two different heat exchanger (HEX) architectures; tube-in-tube (DPHEX) and plate (PHEX) designs, at designconditions. The sizing results reveal that the PHEX area requirements are almost 50% lower than the respective ones for DPHEX, while recovering equivalent quantities of heat. Next, the ORC engine operation is optimised atpart-load ICE conditions, and the HEX heat transfer coefficients (HTCs) are predicted. Results indicate that: i) PHEX HTCs are up to 50% higher than DPHEX equivalents;ii)HTCsdecreaseat part load for both HEXs, but because the average temperaturedifferenceincreases, the overall HEX effectiveness improves; and iii) the ORC system with a PHEX evaporator has slightly higher power output thanthe DPHEX equivalent at off-design operation.Overall, the modelling tool developed here can predict ORC performance over an operating envelopeand allows the selection ofoptimal designsand si
AU - Chatzopoulou,MA
AU - Sapin,P
AU - Markides,C
PY - 2018///
TI - Optimisation of off-design internal combustion-organic Rankine engine combined cycles
UR -
ER -