Title

Hysteresis In Spray Cooling Of Micro-Structured Surfaces

Abstract

Spray cooling experiments were performed in a closed loop with ammonia using RT1's vapor atomized spray nozzles, Thick film resistors, simulating heat source, were mounted onto 1cm × 2cm heater surfaces and heat fluxes up to 500 W/cm2 (well below critical heat flux (CHF) limit) were removed. Two nozzles each spraying 1 cm2 of heater area utilized 96 mlJcm 2- mm (9.7 gallin2-hr) liquid and 13.8 ml/cm2-s (11.3 ft3/in2-hr) vapor flow rate with only 48 kPa (7 psi) pressure drop. A smooth surface and two types of micro-structured surfaces with indentations and protrusions were used as test surfaces, Comparison of cooling curves in the form of surface superheat (ΔTsat T surf - Tsat) vs. heat flux in the heating-up and cooling- down modes (for increasing and decreasing heat flux conditions) demonstrated substantial performance enhancement for both micro-structured surfaces over a smooth surface, Moreover, results showed that smooth surface gives nearly identical cooling curves while micro-structured surfaces experience a hysteresis phenomenon depending on the surface roughness level and yields lower surface superheat in the cooling-down mode, compared to the heating-up mode, at a given heat flux, Micro-structured surface with protrusions was tested using two approaches to gain better understanding on hysteresis. Data mainly indicated that micro-structured surface helps retain established three-phase contact line, the region where solid, liquid and vapor phases meet, resulting in consistent cooling curve and hysteresis effect at varying heat flux conditions (as low as 25 W/cm2 for the present work), Data furthermore confirmed a direct connection between hysteresis and thermal history of the heater. Copyright © 2008 by ASME.

Publication Date

9-21-2009

Publication Title

2008 Proceedings of the ASME Summer Heat Transfer Conference, HT 2008

Volume

2

Number of Pages

581-587

Document Type

Article; Proceedings Paper

Personal Identifier

scopus

Socpus ID

70349110580 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/70349110580

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