In order to comprehensively assess the performance of microchannel heat sink with fan-shaped ribs on sidewalls, this third part of a three-part study focuses on the relationship between thermal resistance and pumping power, and further the entropy generation rate and performance evaluation criteria, with water and silicon used as fluid and solid for the computational domain. The microchannel has the width of 0.1 mm and depth of 0.2 mm in the constant cross-section region. The geometric parameters include the width (0.05-0.4 mm), height (0.005-0.025 mm) and spacing (0.2-5 mm) of aligned or offset fan shaped ribs. For deep insight into the basic mechanisms and properties of such heat sinks, the entropy generation rate due to heat transfer and fluid friction are separately studied. Results show that the fan-shaped ribs can lead to better comprehensive performance and the geometric parameters of fan shaped ribs have a significant influence on the performance of such microchannel heat sinks. With the increase of the rib's height, the microchannel heat sinks with offset fan-shaped ribs gradually perform better than the ones with aligned fan-shaped ribs. With the decrease of the rib's spacing, the comprehensive performance firstly becomes better and then gradually deteriorates. For the microchannel heat sink with large rib's height and small rib's spacing, the increase of Reynolds number can lead to tremendously increase of entropy generation rate due to fluid friction, which can withdraw the decrease of entropy generation rate due to heat transfer and lead to the increase of total entropy generation rate, making the comprehensive performance worse than the smooth one. For Reynolds number ranging from 187 to 715 and studied geometric parameters, the best microchannel heat sink shows a 32% decrease in entropy generation rate and 1.33 in performance evaluation criteria, comparing with the smooth one. Crown Copyright (C) 2016 Published by Elsevier Ltd. All rights reserved.