A microscale heater array 2:7 mm 2:7 mm in size along with a video camera was used to provide subcooled pool boiling heat transfer measurements at gravity levels ranging from 1.8g to 10 g. The fluid was FC-72 at 1 atm and subcooled by nominally 36 C for all cases. A Terrier–Orion sounding rocket and the KC-135 aircraft were used to provide the microgravity and low-g environments, respectively. ...

Infrared thermometry was used to obtain first-of-a-kind, time- and space-resolved data for pool boiling phenomena in water-based nanofluids with diamond and silica nanoparticles at low concentration (<0.1 vol.%). In addition to macroscopic parameters like the average heat transfer coefficient and critical heat flux [CHF] value, more fundamental parameters such as the bubble departure diameter a...

In this paper we consider a model for pool-boiling systems known from the literature. This model involves only the temperature distribution within the heater and models the heat exchange with the boiling medium via a nonlinear boundary condition imposed on the fluid-heater interface. The model allows multiple homogeneous (i.e. spatially constant) and multiple heterogeneous steady-state solution...

This study investigated the pool boiling heat transfer under heating surfaces with various interlaced wettability. Nano-silica particles were used as the coating element to vary the interlaced wettability of the surface. The experimental results revealed that when the wettability of a surface is uniform, the critical heat flux increases with the more wettable surface; however, when the wettabil...

Pool boiling experiments were conducted in microgravity on five space shuttle flights, using a flat plate heater consisting of a semitransparent thin gold film deposited on a quartz substrate that also acted as a resistance thermometer. The test fluid was R-113, and the vapor bubble behavior at the heater surface was photographed from beneath as well as from the side. Each flight consisted of a...

We consider a relatively simple model for pool boiling processes. This model involves only the temperature distribution within the heater and desribes the heat exchange with the boiling fluid via a nonlinear boundary condition imposed on the fluid-heater interface. This results in a standard heat equation with a nonlinear Neumann boundary condition on part of the boundary. In this paper we anal...

Despite system thermal–hydraulic codes were extensively validated for transient simulations of LWR, several activities highlighted limited capabilities these tools to model heat transfer within in-pool passive power removal system. Discrepancies with experimental results related the underestimate pool boiling and film condensation coefficients. Thus, DIAEE “Sapienza” University Rome developed a...

Flow boiling in microchannels has received considerable attention from researchers worldwide in the last decade. A scaling analysis is presented to identify the relative effects of different forces on the boiling process at microscale. Based on this scaling analysis, the flow pattern transitions and stability for flow boiling of water and FC-77 are evaluated. From the insight gained through the...

An easy-to-implement technique for pool boiling heat transfer enhancement is proposed and evaluated through an experimental investigation. This free-particle technique brings about nucleate boiling at a low degree of superheat by means of metal particles that are not fixed to the heated surface, but rather are free to move with respect to the surface. The effects of copper particles with sizes ...

Heat transfer with liquid–vapor phase change in microchannels can support very high heat fluxes for use in applications such as the thermal management of high-performance electronics. However, the effects of channel cross-sectional dimensions on the two-phase heat transfer coefficient and pressure drop have not been investigated extensively. In the present work, experiments are conducted to inv...