Evaluation of enhanced nucleate boiling performance through wall- temperature distributions on PDMS-silica coated and non-coated laser textured stainless steel surfaces

Matevž Zupančič (Avtor), Matic Može (Avtor), Peter Gregorčič (Avtor), Anže Sitar (Avtor), Iztok Golobič (Avtor)

Povzetek

Nucleate boiling was examined on Joule heated stainless steel foils, functionalized by PDMS-silica coating and/or nanosecond-laser texturing. The nucleating bubbles and transient temperature fields were visual- ized through high-speed IR and video recordings. The differences in boiling performance were evaluated through wall-temperature distributions. Results confirmed that smooth surfaces require high activation temperatures and produce larger bubbles, while wall-temperature distributions display higher standard deviations, higher local superheats, and bimodal shapes. Similarly, relatively high activation temperatures were observed on the superhydrophilic surface, where the enhanced liquid replenishment on the active nucleation sites reduces the bubble departure diameters and prevents formation of local hotspots. Consequently, the analyzed temperature distributions have negative skewness and decreased standard deviation. The highest heat transfer coefficient was achieved on a laser textured surface with nonuniform wettability and multi-scale microcavities. Here, nucleation site density was as high as 200 cm-2 at 300 kW/m2 , while wall-temperature distributions demonstrated by far the lowest standard deviation. The temperature distributions also proved that annealed PDMS-silica coating significantly increased the thermal resistance of the entire heater. On the contrary, laser textured surfaces provided an even better boiling performance compared to coated surfaces and did not increase heater's thermal resistance. This additionally endorses the coating-free, direct laser texturing method as a cutting-edge technology in the development of surfaces capable of significantly enhanced boiling heat transfer.

Ključne besede

enhanced boiling heat transfer;high-speed IR thermography;wall-temperature distributions;PDMS-silica coating;nanosecond laser texturing;

Podatki

Jezik:	Angleški jezik
Leto izida:	2017
Tipologija:	1.01 - Izvirni znanstveni članek
Organizacija:	UL FS - Fakulteta za strojništvo
UDK:	536.24(045)
COBISS:	15473691
ISSN:	0017-9310
Št. ogledov:	1715
Št. prenosov:	982
Ocena:	0 (0 glasov)
Metapodatki:

Ostali podatki

Sekundarni jezik:	Slovenski jezik
Sekundarne ključne besede:	izboljšan prenos toplote pri vrenju;hitrotekoča IR termografija;temperaturna porazdelitev na grelni površini;PDMS-silika premaz;strukturiranje z nanosekundnimi laserskimi bliski;
Vrsta dela (COBISS):	Članek v reviji
Strani:	str. 419-428
Zvezek:	ǂVol. ǂ111
Čas izdaje:	Aug. 2017
DOI:	10.1016/j.ijheatmasstransfer.2017.03.128
ID:	10991033