High heat flux spray cooling with ammonia: Investigation of enhanced surfaces for CHF

    Authors

    H. Bostanci; D. P. Rini; J. P. Kizito; V. Singh; S. Seal;L. C. Chow

    Comments

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    Abbreviated Journal Title

    Int. J. Heat Mass Transf.

    Keywords

    Spray cooling; Thermal management; CHF; Enhanced surfaces; WATER SPRAY; Thermodynamics; Engineering, Mechanical; Mechanics

    Abstract

    A spray cooling study was conducted to investigate the effect of enhanced surfaces on Critical Heat Flux (CHF). Test surfaces involved micro-scale indentations and protrusions, macro (mm) scale pyramidal pin fins, and multi-scale structured surfaces, combining macro and micro-scale structures, along with a smooth surface that served as reference. Tests were conducted in a closed loop system using a vapor atomized spray nozzle with ammonia as the working fluid. Nominal flow rates were 1.6 ml/cm(2) s of liquid and 13.8 ml/cm(2) s of vapor, resulting in a pressure drop of 48 kPa. Results indicated that the multi-scale structured surface helped increase maximum heat flux limit by 18% over the reference smooth surface, to 910 W/cm(2) at nominal how rate. During the additional CHF testing at higher flow rates, most heaters experienced failures before reaching CHF at heat fluxes above 950 W/cm(2). However, some enhanced surfaces can achieve CHF values of up to approximate to 1100 W/cm(2) with approximate to 67% spray cooling efficiency based on liquid usage. The results also shed some light on the current understanding of the spray cooling heat transfer mechanisms. Enhanced surfaces are found to be capable of retaining more liquid compared to a smooth surface, and efficiently spread the liquid film via capillary force within the structures. This important advantage delays the occurrence of dry patches at high heat fluxes, and leads to higher CHF. The present work demonstrated ammonia spray cooling as a unique alternative for challenging thermal management tasks that call for high heat flux removal while maintaining a low device temperature with a compact and efficient cooling scheme. (C) 2012 Elsevier Ltd. All rights reserved.

    Journal Title

    International Journal of Heat and Mass Transfer

    Volume

    55

    Issue/Number

    13-14

    Publication Date

    1-1-2012

    Document Type

    Article

    Language

    English

    First Page

    3849

    Last Page

    3856

    WOS Identifier

    WOS:000304785900051

    ISSN

    0017-9310

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