https://bura.brunel.ac.uk/bitstream/2438/14115/5/Fulltext.pdf

Flow boiling in microchannels: Fundamentals and applications

Review of computational studies on boiling and condensation

Evaporation of a Droplet: From physics to applications

A comprehensive review on interaction of nanoparticles with low salinity water and surfactant for enhanced oil recovery in sandstone and carbonate reservoirs

Numerical investigation of hydrodynamics and heat transfer of elongated bubbles during flow boiling in a microchannel

\n Surface temperature uniformity is an important factor in the thermal management of electronics. The present numerical study investigates the influence of multiple bypass injections on the wall temperature distribution of a single-phase mini/micro-channel. The proposed scheme consists of sending a fraction of the coolant through the inlet of a 0.6 mm deep, 2.5 mm wide, and 25 mm long channel and injecting the remaining coolant through multiple bypass inlets on top of the channel positioned at different axial locations. The study explores four different configurations: the first one being three equispaced bypass micro-nozzles or bypass inlets of uniform diameter (1 mm), the second one being three equispaced bypass micro-nozzles of varying diameter (2 mm, 1 mm, and 0.5 mm), the third one being five equispaced bypass micro-nozzles of varying diameter (2 mm, 1 mm, 0.5 mm, 0.25 mm, and 0.125 mm), and the fourth one being five bypass micro-nozzles, but with three equispaced bypass inlets of varying diameter (2 mm, 1 mm, and 0.5 mm), and the last two bypass inlets of the same diameter as that of the third inlet (0.5 mm). Water is considered as the coolant in the study and the simulations are carried out for two mass fluxes of 465 kg/m2s and 930 kg/m2s and two heat fluxes of 25 kW/m2 and 125 kW/m2. The thermal performance of the channel is evaluated for bypass percentages of 25%, 50%, and 75%, with the Reynolds number varying from 150 to 900 at the primary channel inlet and at the secondary channel inlet, and the range of the nozzle Reynolds number varying from 10 to 707. The fourth configuration results in a near uniform wall temperature distribution, with 82–89% reduction in the wall temperature nonuniformity compared with the no-bypass case. The reductions for the third, second and first configurations are 65–71%, 53–76%, and 54–74%, respectively. The third configuration results in an average heat transfer coefficient enhancement of up to 49%. On the whole, the improvement in the wall temperature uniformity is higher than the increase in the pressure drop, and the increase in the channel heat transfer coefficient is higher than pressure drop for some cases.

Numerical Study of Single-Phase Heat Transfer Performance of a Mini/Micro-Channel Integrated With Multiple Bypass Micro-Nozzles

Combined micro-channel flow and jet impingement can be one of the methods to maximise the benefits of micro-channel heat sinks but very less research has been done in this direction. However, there are difficulties and limitations involved in implementing both the techniques together, for e.g., channel flow blockages or stagnations caused by multiple jets along the channel. In the present study, to overcome these limitations, multiple secondary inlets along the channel, besides the main inlet, are proposed such that the flow takes place in only one direction. This avoids flow blockage, and still exploits some benefits of jet impingement. Six different cases were modelled and studied using commercial CFD software ANSYS FLUENT to determine the effects of size and inclination of secondary inlets on the heat sink performance. The best performance is shown by the secondary inlets with 50% reduction in the successive diameters and inclined at 90° with the horizontal. The results show reduced heat sink wall temperature, increased uniformity in wall temperature and higher heat transfer coefficients, however, at the cost of higher pressure losses.

Numerical studies on single-phase micro-channel heat sink with multiple inlets along the channel

In the present study, a 1-dimensional model is proposed to estimate the pressure drop and heat transfer coefficient for flow boiling in a rectangular microchannel. The present work takes into account the pressure fluctuations caused due to the confined bubble growth and the effect of pressure fluctuations on the heat transfer characteristics. The heat transfer model considers five zones, namely, liquid slug, partially confined bubble, fully confined (elongated) bubble, partial dryout and full dry-out. The model incorporates the thinning of liquid film due to shear stress at liquid-vapour interface in addition to evaporation. The transient fluctuations in pressure and heat transfer coefficient, along with the time-averaged ones, are verified with the experimental data available in the literature. Heat transfer characteristics with flow reversal caused by inlet compressibility are also presented.

Modeling of pressure drop and heat transfer for flow boiling in a mini/micro-channel of rectangular cross-section

The modelling of the dynamics of inclined closed loop buoyancy driven heat exchangers with inclusion of the wall conduction effect at the heat exchanger is presented in the current study. A Coupled Natural Circulation Loop (CNCL) is an ideal system for studying the closed loop buoyancy driven heat exchanger. The modelling utilises a Fourier series based approach to develop a 1-D model which is then verified with the 3-D CFD studies of the respective cases. A good agreement is observed with the 3-D CFD data, which demonstrates the suitability of the 1-D model for transient behaviour prediction. The non-dimensional numbers and thermal coupling sensitivity coefficients which govern the dynamics of the CNCL are identified and an appropriate parametric study is conducted. Results show that the wall conduction and inclination have a significant effect on the transient behaviour of the CNCL system. A jump in the heat transfer coefficient with variation in the inclination of the Conjugate CNCL system is observed. The 1-D model is also able to capture the flow direction reversal with change in the inclination of the Conjugate CNCL system for zero flow field initial conditions.

Sateesh Gedupudi

Papers

Numerical Study of Single-Phase Heat Transfer Performance of a Mini/Micro-Channel Integrated With Multiple Bypass Micro-Nozzles

Numerical studies on single-phase micro-channel heat sink with multiple inlets along the channel

Modeling of pressure drop and heat transfer for flow boiling in a mini/micro-channel of rectangular cross-section

Fourier series based modeling of the dynamics of inclined closed loop buoyancy driven heat exchangers with conjugate effect

Machine learning in heat transfer