An Overview of Surface Roughness Effects on Nucleate Boiling Heat Transfer~!2009-10-31~!2010-01-01~!2010-04-16~!

Abstract

Abstract:The paper aims at an overview of heating surface microstructure effects on nucleate boiling heat transfer. A comprehensive chronological literature survey is presented followed by an analysis of the results of an experimental investigation. Boiling data of refrigerants R-134a and R-123 on 19 mm diameter copper and brass tubes of average surface roughness varying from 0.07 μm to 10.5 μm have been gathered under the present investigation. Though most of the data confirm previous literature trends, according to which the heat transfer coefficient increases with surface roughness, very rough surfaces present a peculiar behavior with respect to that of the smoother surfaces (Ra<3.0 μm). Heat transfer performance of very rough surfaces is superior to the smoother ones at low heat fluxes (q<20 kW/m 2 ). However, decay in their thermal performance is observed in the high heat fluxes range. An in depth analysis of the effect of roughness on the slope, "m" of the h vs q curves has been performed with a general conclusion being that "m" is affected not only by de pressure but also by the surface roughness. Finally, an analysis of the active cavities density is performed using some models from the literature in order to evaluate the effect of surface roughness in cavity activation. The obtained results are generally inconclusive. However, it has been determined that surface microstructure effects must not be neglected in future models.

Experimental and Numerical Study of the Effects of Asymmetric Micro Ratchets on Pool Boiling Performance

“…It can be quickly seen that the highest performance is reserved for the 10:1 aspect ratio. These results correlate well with the results of Jabardo [86] who found that the heat transfer coefficient and heat flux increases and then decreases with increasing surface roughness.…”

Saturation boiling of PF-5060 on rough Cu surfaces: Bubbles transient growth, departure diameter and detachment frequency

“…These variances are partially due to the different methods used for the surface preparation [10] and the different properties of the surface materials [9,11]. Some studies have indicated that the enhancement in nucleate boiling increases with increasing surface roughness up to a point, beyond which little changes occur [12]. Other investigators have reported that increasing surface roughness increases its hydrophobicity [13][14][15], decreasing the bubble departure diameter and increasing the detachment frequency, and thus enhancing nucleate boiling.…”

Computational fluid dynamics assessment of subcooled flow boiling in internal-combustion engine-like conditions at low flow velocities with a volume-of-fluid model and a two-fluid model

“…A different way to obtain was proposed in [17], where it was expressed as a function of the roughness arithmetic average as:…”

“…The fluid/surface material combinations are accounted for by coefficient , whose values are around 1, ranging from 0.8 to 1.3 [17]. Even if the fluids are different from that considered in this work, the possibility of applying equation (5) to the present case was checked.…”