1. T HE C OOLING E FFECTS OF V ARYING W ATER D ROPLET V OLUME AND S URFACE C ONTACT A NGLE W ITH A M ETAL S URFACE I N A S TEADY S TATE, H IGH T EMPERATURE A IR F LOW Project Proposal MANE 6970 Matthew Noll February 19, 2015

2. INTRODUCTION This project will analyze the effects of changing physical parameters of a water droplet on the evaporative cooling of a flat metal plate in a high temperature air flow.

3. BACKGROUND Cooling a high temperature air flow normally requires spray cooling with droplets on the scale of atomized particles. Depending on the system design or properties, an atomized spray is not always available. Evaporative cooling has the potential to maintain materials and components that are located in high temperature air flows at much lower temperatures without the need for an atomized spray.

4. APPROACH The analytical method that calculates the heat transfer between the plate, water and air flow, will be calculated to support the COMSOL analysis. A hemisphere, as shown below will be used to create the mesh which will act as the water droplet. The mesh will be done automatically to simplify the process. By traversing the wall boundary up through the mesh, the surface contact angle is changed.

5. APPROACH (CONT.) When modeling the evaporation of the droplet in COMSOL, the time step is assumed to be very small and therefore is seen as a snapshot in time. The volume of the droplet will be changed by changing the radius of the hemisphere that is bounded by the wall.

6. POSSIBILITIES FOR SCOPE EXPANSION Although the “snapshot” analysis will give accurate values for heat transfer and metal surface temperature, the actual boundary of the liquid droplet is constantly shrinking as it is evaporated. COMSOL has multiple modules which can be used to analyze a system with a moving boundary, which can be applied to this case.

7. REFERENCES 1.Pressurizer Heater Material Issues in the Nuclear Industry Project Proposal, Daniel B. Denis, March 12, 2014 2.C OMSOL E XAMPLE, Evaporative Cooling of Water: (https://roundcube.rpi.edu/roundcube/?_part=4&_action=get&_mbox=INBOX& _uid=977&_task=mail) 3.S PRAY E VAPORATIVE C OOLING TO A CHIEVE U LTRA F AST C OOLING IN R UNOUT T ABLE ( HTTP :// WWW. SCIENCEDIRECT. COM. LIBPROXY. RPI. EDU / SCIENCE / ARTICLE / PII /S12900729090001 92) 4.Numerical simulation of accident spray cooling system in FGD system inlet (http://eds.a.ebscohost.com.libproxy.rpi.edu/eds/pdfviewer/pdfviewer?sid=8b8 1cb50-a6fa-447d-8bb4-cc979b945368%40sessionmgr4004&vid=3&hid=4102) 5.Fundamentals of Heat and Mass Transfer, Wiley 2011, Hoboken NJ, 07030-5774