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 March 19, 2015

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

3. BACKGROUND Cooling a high temperature air flow, such as the exhaust flow from a stationary natural gas turbine generator, normally requires spray cooling with droplet sizes on the scale of atomized particles. System limitations may limit the ability to produce an atomized droplet spray. Water quality available for cooling spray Cooling system pressure limits Spray nozzle availability Additives that affect droplet surface tension Evaporative cooling provides 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. METHOD

5. THEORY This paper begins with a droplet modeled as a half circle on top of a rectangular metal plate in a region of hot air flow. The original droplet diameter is 1mm, and since the droplet is modeled as a half circle, the surface contact angle is 90°. The effects of changing the droplet volume and surface contact angle are studied, but this paper does not research what methods are used to change these properties of the droplet. In an effort to simplify the study, the preliminary results model the evaporation process as a snapshot in time, and the boundary of the droplet is not moving.

6. ASSUMPTIONS Heat and mass transfer of the system are in steady state. The properties of the water are assumed to be constant. The upper “wall” (boundary) of the gas region modeled along with the metal surface are assumed to be slip conditions. Pure water is used for the spraying fluid. It is assumed that atomization is not possible with the components of the system, so droplet diameter is assumed to be 1mm and greater.

7. PRELIMINARY RESULTS Originally, the wall of the flat plate was modeled as a non-slip condition, which disrupted the velocity field of the hot air flow. The second figure models this wall as a slip condition and the velocity vectors are show.

8. 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