Proceedings of IMECE2007 2007 ASME International Mechanical Engineering Congress and Exposition November 11-15, 2007, Seattle, Washington, USA DRAFT IMECE2007-41335 ANALYSIS OF THE PERFORMANCE OF IONIC LIQUIDS IN COOLING LOOPS Mihir Sen, Samuel Paolucci and Wenjun (Katherine) Liu Department of Aerospace and Mechanical Engineering University of Notre Dame Notre Dame, Indiana 46556 ABSTRACT Liquids are often pumped in closed loops to trans- fer heat from a high temperature source to a low tem- perature sink. They operate at low Reynolds number when the diameter of the pipe is small, the fluid veloc- ity is low, or when the working liquid is very viscous. Ionic liquids, though environmentally friendly, typi- cally have viscosities much larger than water. An ana- lytical study is made of the process for the purpose of determining what the important physical parameters of the system are that will enable the largest quan- tity of heat to be transferred for unit work expended. For this purpose, a loop is considered that has a pump that generates a certain pressure rise and two heat ex- changers, one for heating the fluid and the other for cooling it. Laminar flow that is fully-developed hy- drodynamically and thermally is assumed. The analy- sis is based on constant fluid properties, and analytical expressions are obtained for the heat rate and the work input. Address all correspondence to this author: Mi- hir.Sen.1@nd.edu Abstract Nomenclature D diameter of pipe k fluid thermal conductivity L total length of loop L c length of cooled section L h length of heated section Nu Nusselt number in heat exchanger Δ p pressure increase in pump Q heat transfer rate R QW T temperature of fluid T c temperature of cooling fluid T h temperature of heating fluid T in c temperature fluid entering cooler T out c temperature fluid leaving cooler T in h temperature fluid entering heater T out h temperature fluid leaving heater V average fluid velocity W mechanical power input x local coordinate inside heat exchanger Greek symbols αβ c β h non-dimensional parameters ρ fluid density 1 Copyright c 2007 by ASME