Boiling Flow Interaction Between Two Parallel Microchannels

2006 ◽  
Author(s):  
Roger D. Flynn ◽  
David W. Fogg ◽  
Jae-Mo Koo ◽  
Ching-Hsiang Cheng ◽  
Kenneth E. Goodson
Keyword(s):  
Heat Transfer ◽  
Liquid Flow ◽  
Heat Exchangers ◽  
Single Channel ◽  
Flow Boiling ◽  
Parallel Channel ◽  
Flow Interaction ◽  
Boiling Flow ◽  
Parallel Microchannels ◽  
Channel Configuration

Microchannel heat exchangers predominately use a parallel channel configuration to maximize heat transfer with minimal pump demand. Previous work optimized bulk performance of liquid flow heat exchangers but noted that upon boiling, flow redistributed among parallel channels, and they ultimately found that this instability caused an uncontrollable operating condition. This work predicts and measures fully coupled boiling flow interaction in a simplified two microchannel system. A series of silicon microfabricated devices enable piecewise study of the coupled fluidic and heat transfer interactions, first uniting the fluid inlets of thermally isolated channels, then connecting neighboring channel walls to allow heat transfer between channels. Multiple combinations of boiling and liquid flow, each satisfying system boundary conditions, are identified using flow demand curves assembled from single channel data. Each unique flow condition is experimentally demonstrated and found to be heavily dependent on the prior state of the channels. Connecting channel walls, thermally, is shown to lessen the number of allowed solutions and increase instability in the two channel system, allowing distinction between purely fluidic instabilities and fluidic instabilities coupled to heat transfer between channels. This work in describing interaction between two channels is a necessary step as work continues toward characterizing flow boiling in more complex parallel channel heat sinks.

History, Advances, and Challenges in Liquid Flow and Flow Boiling Heat Transfer in Microchannels: A Critical Review

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Liquid Flow ◽  
Heat Exchangers ◽  
Single Phase ◽  
Heat Dissipation ◽  
Flow Boiling ◽  
Thermal Control ◽  
Future Research ◽  
Practical Implementation ◽  
High Heat Flux

As the scale of devices becomes small, thermal control and heat dissipation from these devices can be effectively accomplished through the implementation of microchannel passages. The small passages provide a high surface area to volume ratio that enables higher heat transfer rates. High performance microchannel heat exchangers are also attractive in applications where space and/or weight constraints dictate the size of a heat exchanger or where performance enhancement is desired. This survey article provides a historical perspective of the progress made in understanding the underlying mechanisms in single-phase liquid flow and two-phase flow boiling processes and their use in high heat flux removal applications. Future research directions for (i) further enhancing the single-phase heat transfer performance and (ii) enabling practical implementation of flow boiling in microchannel heat exchangers are outlined.

History, Advances, and Challenges in Liquid Flow and Flow Boiling Heat Transfer in Microchannels: A Critical Review

2010 ◽  
Author(s):  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Liquid Flow ◽  
Heat Exchangers ◽  
Single Phase ◽  
Heat Dissipation ◽  
Flow Boiling ◽  
Thermal Control ◽  
Future Research ◽  
Practical Implementation ◽  
High Heat Flux

As the scale of devices becomes small, thermal control and heat dissipation from these devices can be effectively accomplished through the implementation of microchannel passages. The small passages provide a high surface area to volume ratio that enables higher heat transfer rates. High performance microchannel heat exchangers are also attractive in applications where space and/or weight constraints dictate the size of a heat exchanger or where performance enhancement is desired. This survey article provides a historical perspective of the progress made in understanding the underlying mechanisms in single-phase liquid flow and two-phase flow boiling processes and their use in high heat flux removal applications. Future research directions for (i) further enhancing the single-phase heat transfer performance, and (ii) enabling practical implementation of flow boiling in microchannel heat exchangers, are outlined.

Comparison of 30 Boiling and Condensation Correlations for Two-Phase Flows in Compact Plate-Fin Heat Exchangers

2017 ◽  
Author(s):  
Wenhai Li ◽  
Ken Alabi ◽  
Foluso Ladeinde
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Flow Boiling ◽  
Transfer Coefficients ◽  
Two Phase Flows ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
Heat Exchanger Design ◽  
Micro Channels ◽  
Vertical Tubes

Over the years, empirical correlations have been developed for predicting saturated flow boiling [1–15] and condensation [16–30] heat transfer coefficients inside horizontal/vertical tubes or micro-channels. In the present work, we have examined 30 of these models, and modified many of them for use in compact plate-fin heat exchangers. However, the various correlations, which have been developed for pipes and ducts, have been modified in our work to make them applicable to extended fin surfaces. The various correlations have been used in a low-order, one-dimensional, finite-volume type numerical integration of the flow and heat transfer equations in heat exchangers. The NIST’s REFPROP database [31] is used to account for the large variations in the fluid thermo-physical properties during phase change. The numerical results are compared with Yara’s experimental data [32]. The validity of the various boiling and condensation models for a real plate-fin heat exchanger design is discussed. The results show that some of the modified boiling and condensation correlations can provide acceptable prediction of heat transfer coefficient for two-phase flows in compact plate-fin heat exchangers.

An Experimental Investigation of Microchannel Size Effects on Flow Boiling With De-Ionized Water

2009 ◽  
Author(s):  
Bradley T. Holcomb ◽  
Tannaz Harirchian ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Flow Boiling ◽  
Dielectric Liquid ◽  
Channel Width ◽  
Boiling Curve ◽  
Test Pieces ◽  
Parallel Microchannels

The heat transfer characteristics during flow boiling of deionized water in parallel microchannels are investigated. The silicon heat sinks contain an array of integrated heaters and diodes for localized heat-flux control and temperature measurement. The channel widths for the three different test pieces range from 250 μm to 2200 μm, with a nominal depth for all channels of 400 μm. The present study investigates the effects of the channel width and mass flux on the boiling performance. This study follows a previous study using a wetting dielectric liquid, and aims to understand the role of wetting since water is relatively non-wetting. From the results of the present study, a weak dependence of the boiling curve and heat transfer coefficient on mass flux was observed. Varying the channel width also does not have a strong effect on either the boiling curve or the heat transfer coefficient. The experimental results are compared to those obtained previously for a dielectric liquid. They are also compared with predictions from several correlations from the literature.

Local Heat Transfer Coefficient of Flow Boiling in Microchannels With Artificial Reentrant Cavities

2007 ◽  
Author(s):  
Chih-Jung Kuo ◽  
Yoav Peles
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Bubble Generation ◽  
Parallel Microchannels

Flow boiling in parallel microchannels with structured reentrant cavities was experimental studied. Flow patterns, boiling inceptions and heat transfer coefficients were obtained and studied for G = 83 kg/m2-s to G = 303 kg/m2-s and heat fluxes up to 643 W/cm2. The heat transfer coefficient-mass velocity and quality relations had been analyzed to identify boiling mechanism. Comparisons of the performance of the enhanced and plain-wall microchannels had also been made. The microchannels with reentrant cavities were shown to promote nucleation of bubbles and to support significantly better reproducibility and uniformity of bubble generation.

Suppression of Boiling Flow Oscillations in Parallel Microchannels by Inlet Restrictors

2005 ◽  
Vol 128 (3) ◽  
pp. 251-260 ◽  
Author(s):  
Ali Koşar ◽  
Chih-Jung Kuo ◽  
Yoav Peles
Keyword(s):  
Dimensionless Parameter ◽  
Flow Instability ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Mass Fluxes ◽  
Boiling Flow ◽  
Flow Oscillations ◽  
Parallel Channels ◽  
Geometrical Effects ◽  
Parallel Microchannels

Geometrical effects of MEMS-based microfabricated inlet orifices on the suppression of parallel channel and upstream compressible volume instabilities commonly exhibited during flow boiling in parallel microchannels have been investigated. The heat fluxes at the onset of unstable boiling have been obtained over effective heat fluxes ranging from 9 to 614W∕cm2 and mass fluxes from 115to389kg∕m2s. A dimensionless parameter M, which accounts for the pressure drop increase imposed by the inlet restrictors, has been used to correlate the extent of flow instability suppression. It has been shown that the onset of unstable boiling asymptotically increases with M. At sufficiently high M values, parallel channels and upstream compressible volume instabilities are completely eradicated although it gives way to another instability to develop, namely, the critical heat flux conditions. A correlation has been developed in terms of M to predict the conditions leading to unstable boiling.

A Modified Correlation for Flow Boiling Heat Transfer in Plate Heat Exchangers

2019 ◽  
Author(s):  
Tong Lv ◽  
Boren Zheng ◽  
Wei Li ◽  
Zahid Ayub
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Plate Heat ◽  
Error Band ◽  
Flow Boiling Heat Transfer ◽  
Compact Size ◽  
Wide Range ◽  
Data Points

Abstract Corrugated plate heat exchangers are increasingly used in two-phase flow applications for their flexible and compact size and the efficient heat transfer performance. This paper presents a review of recent studies on the subject and creates a database containing 533 data points from experiment studies. The collected database covers seven working fluids, a wide range of vapor quality (both mean and local) 0.01–0.94, heat flux 0.5–46 kW m−2, mass flux 5.5–137 kg m−2 s−1, chevron angle 30°–70°, and hydraulic diameter 1.7–4.0 mm. Based on the database a brief comparison between several previous correlations are discussed. A new prediction method for flow boiling heat transfer coefficient is generated by multiple regression analysis and modifying an existing correlation. It was observed that the modified correlation shows a better agreement and predicts 74.3% of data points within ±30% error band and 94.9% within ±50% error band.

Extending the Applicability of the Flow Boiling Correlation to Low Reynolds Number Flows in Microchannels

2003 ◽  
Author(s):  
Satish Kandlikar ◽  
Prabhu Balasubramanian
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Liquid Flow ◽  
Flow Boiling ◽  
Reynolds Numbers ◽  
Nucleate Boiling ◽  
Mean Deviation ◽  
Low Reynolds Number Flows ◽  
Boiling Heat Transfer Coefficient ◽  
Low Reynolds

As microchannels are applied in flow boiling applications, it is becoming apparent that the Reynolds number based on all liquid flow could approach values below 100. The earlier work by Kandlikar and Steinke (2002, 2003) provided modifications to the Kandlikar correlation (1990, 1991) by extending the range of the correlation to all-liquid Reynolds numbers in the range 1000–3000. The present work utilizes the newly available data on flow boiling in microchannels that cover the all-liquid flow Reynolds number between 50–500. A new correlation is developed in this range that is able to predict the flow boiling heat transfer coefficient and its trends with quality, heat flux and mass flux accurately within less than 15 percent mean deviation. It is noted that the correlation simply accounts for the change of the flow boiling mechanism without incorporating any additional empirical constants. The heat transfer mechanism during flow boiling at such low Reynolds numbers is altered considerably indicating strong presence of nucleate boiling mode of heat transfer.

Numerical Simulation of the Flow Boiling Heat Transfer Performance of R134a in a Microchannel Evaporator With Louvered Fins

2011 ◽  
Author(s):  
Justin J. Gossard ◽  
Andrew D. Sommers
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Flow Boiling ◽  
Control Volume ◽  
Cooling Capacity ◽  
Heat Exchanger Design ◽  
Microchannel Tubes ◽  
Louvered Fins

The need for more compact and more efficient heat exchangers in the aerospace, automotive, and HVAC&R industries has led to the development of heat exchangers that utilize minichannel or microchannel tubes coupled with louvered fins. Minichannel and microchannel heat exchangers exhibit enhanced heat transfer with a minimal increase in pressure drop over conventional round tube, plain fin heat exchangers often with a significant reduction in the required refrigeration charge and overall heat exchanger size. This paper presents the development and validation of a finite volume, steady-state evaporator model to be used as an aid in heat exchanger design and analysis. The model focuses on evaporator geometries that include minichannel and microchannel tubes with louvered fins and headers. Multiple published correlations provide the user with options for calculating the air-side and refrigerant-side heat transfer and pressure drops within the control volume. Once the model was validated, it was then briefly used to study the effects of maldistribution of refrigerant within the inlet headers on the cooling capacity and refrigerant side pressure drop.

Sign in / Sign up

Export Citation Format

Share Document