Flow boiling of 1-methoxyheptafluoropropane (HFE 7000) in 222 m hydraulic diameter channels containing a single row of 24 inline 100 m pin fins was studied for mass fluxes from 350 kg /m2 s to 827 kg /m2 s and wall heat fluxes from 10 W /cm2 to 110 W /cm2. Flow visualization revealed the existence of isolated bubbles, bubbles interacting, multiple flow, and annular flow. The observed flow patte...

Boiling--a process that has powered industries since the steam age--is governed by bubble formation. State-of-the-art boiling surfaces often increase bubble nucleation via roughness and/or wettability modification to increase performance. However, without active in situ control of bubbles, temperature or steam generation cannot be adjusted for a given heat input. Here we report the ability to t...

Molecular dynamics (MD) simulations were employed to investigate the effect of wettability (via contact angle variation) on nanoscale pool boiling heat transfer of a liquid argon thin film on a horizontal copper substrate topped with cubic nano-pillars. The liquid-solid potential was incrementally altered in order to vary the contact angle between hydrophilic (θ~63°) and super hydrophobic (θ~15...

This paper presents a new numerical model, called the CAS model, for boiling heat transfer. The CAS model is based on the cellular automata (CA) technique that is integrated into the popular SIMPLER algorithm for CFD problems. In the model, the CA technique deals with the microscopic nonlinear dynamic interactions of bubbles while the traditional CFD algorithm is used to determine macroscopic s...

Boiling heat transfer is a key thermal limit in nuclear systems. However, for decades, its modeling has relied on speculative hypotheses and a good dose of empiricism. As researchers now start to develop more mechanistic models, the need for high-quality high-resolution data on the bubble nucleation and growth cycle is increasing. Specifically, nucleation site density, bubble departure diameter...

Boiling is a common mechanism for liquid-vapor phase transition and is widely exploited in power generation and refrigeration devices and systems. The efficacy of boiling heat transfer is characterized by two parameters: (a) heat transfer coefficient (HTC) or the thermal conductance; (b) the critical heat flux (CHF) limit that demarcates the transition from high HTC to very low HTC. While incre...

Experiments on the flow boiling heat transfer of almost pure CO2 and CO2-oil mixtures in horizontal smooth and micro-fin tubes have been carried out. The smooth tube is a stainless steel tube with an inside diameter of 3mm, and the micro-fin tube is a copper tube with a mean inside diameter of 3.04mm. Experiments were carried out at mass velocities from 190 to 1300kg/(ms), saturation temperatur...

This thesis consists of an experimental investigation of the effect of surfactants on the boiling curve of water. Via adsorbtion to the boiling surface, surfactants alter the surface energy interaction during bubble formation at nucleation sites. The surfactants initially enhance the heat transfer coefficient at the onset of nucleate boiling due to higher nucleation density and higher bubble de...

Steady state pool boiling heat transfer coefficients have been obtained experimentally for acetone–isopropanol–water and acetone–MEK (methyl ethyl ketone)–water ternary systems. The data show that, for a given heat flux, the heat transfer coefficients of mixtures are lower than those obtained for pure components constituting the mixture. The measured heat transfer coefficients were compared wit...