Experimental Study of Enhanced Nucleate Boiling Heat Transfer on Uniform and Modulated Porous Structures

Abstract

An experimental investigation of the Critical Heat Flux (CHF) and heat transfer coefficient (HTC) of two-phase heat transfer of de-Ionized (DI) water, pool boiling was conducted using several kinds of sintered copper microparticle porous uniform and modulated structures. The modulated porous structure reached a heat flux of 450 W/cm 2 and a heat transfer coefficient of 230,000 W/m 2 K. The thick and thin uniform porous structures achieved CHFs of 290 W/cm 2 and 227 W/cm 2 , respectively, and heat transfer coefficients of 118,000 W/m 2 K and 104,000 W/m 2 K. The mechanisms for the dramatically improved CHFs and HTCs were identified with assistance of a visualization study.

Comparison study of liquid replenishing impacts on critical heat flux and heat transfer coefficient of nucleate pool boiling on multiscale modulated porous structures

“…The summary shows that the porous structures are very effective for the CHF enhancement by increasing the nucleation site density, extending heating surface area, and controlling bubble dynamics, especially when the heat flux demand is over 150 W/cm 2 . Comparison study in Table 1 also shows that micron to millimeter size structures can give a better two-phase change heat transfer performance than the nanometer size structures due to the geometric effect on the vapor escaping, as explained in detail by Li and Peterson [19,28]. When the heat flux reaches a relatively high level, a modulated porous structure will achieve much better heat transfer performance than the uniform thickness porous structures due to the fact that the modulated structures can separate the adjacent vapor columns for vertical liquid replenishment, suppress the hydrodynamic instability, and delay the formation of the vapor blanket covering the heating surface.…”

“…Heating surfaces coated with porous structure show great promise in improving both CHF and heat transfer coefficient [5][6][7][8][9][10][11][12][13][14][15][16][17][18]. More recently, creating nanoscale structures on heating surfaces has been explored and those new nanoscale surface structures have demonstrated dramatic enhancements on CHF and heat transfer coefficient beyond expectations, which is believed due to the increasing of the surface wettability and nucleation site density [19][20][21][22][23][24][25].…”

“…One is the fairly accepted hydrodynamic instability mechanism developed by Zuber [26] and further modified by Polezhaev and Kovalev [27], and the other one is the surface liquid replenishment of dryout hotspots [19][20][21][22][23][24][25].…”

A systematic study of pool boiling heat transfer on structured porous surfaces: From nanoscale through microscale to macroscale

“…Surface structures that can separate the liquid and vapor flow columns have been studied to delay and even possibly prevent CHF from occurring. 7,11,22 The theory of the wetting limit, the point at which fluid can no longer be supplied to the hot spots on the surface, states that CHF can still occur prior to 117133-9 Rioux, Nolan, and Li AIP Advances 4, 117133 (2014) the coalescence of the vapor columns due to hydrodynamic instability. When the liquid rewetting to the hotspots reaches its limit, CHF will occur.…”

“…29 The second theoretical group describing the onset of CHF covers the ability of the surface to resupply hotspots with cool liquid, 30 and has been referenced in many of the latest research efforts on nanoscale surface structures. 18,22,31,32 The hydrodynamic instability theory states that CHF will be reached once hydrodynamic instability of vapor columns occurs. The model recognizes the vapor streams leaving the surface create separate channels of liquid and vapor.…”