scholarly journals Experimental Investigation and Prediction on Pressure Drop during Flow Boiling in Horizontal Microchannels

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 510
Author(s):  
Yan Huang ◽  
Bifen Shu ◽  
Shengnan Zhou ◽  
Qi Shi
Keyword(s):  
Pressure Drop ◽  
Flow Model ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Separated Flow ◽  
Heat Fluxes ◽  
Phase Flow ◽  
Vapor Quality ◽  
Two Phase ◽  
Gas Flux

In this paper, two-phase pressure drop data were obtained for boiling in horizontal rectangular microchannels with a hydraulic diameter of 0.55 mm for R-134a over mass velocities from 790 to 1122, heat fluxes from 0 to 31.08 kW/m2 and vapor qualities from 0 to 0.25. The experimental results show that the Chisholm parameter in the separated flow model relies heavily on the vapor quality, especially in the low vapor quality region (from 0 to 0.1), where the two-phase flow pattern is mainly bubbly and slug flow. Then, the measured pressure drop data are compared with those from six separated flow models. Based on the comparison result, the superficial gas flux is introduced in this paper to consider the comprehensive influence of mass velocity and vapor quality on two-phase flow pressure drop, and a new equation for the Chisholm parameter in the separated flow model is proposed as a function of the superficial gas flux . The mean absolute error (MAE ) of the new flow correlation is 16.82%, which is significantly lower than the other correlations. Moreover, the applicability of the new expression has been verified by the experimental data in other literatures.

scholarly journals A Separated-Flow Model for Predicting Flow Boiling Critical Heat Flux and Pressure Drop Characteristics in Microchannels

2012 ◽  
Author(s):  
Tie Jun Zhang ◽  
Siyu Chen ◽  
Evelyn N. Wang
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Critical Heat Flux ◽  
Flow Model ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Separated Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Microchannel Cooling

Two-phase microchannel cooling promises high heat flux removal for high-performance electronics and photonics. However, the heat transfer performance of flow boiling microchannels is limited by the critical heat flux (CHF) conditions. For variable heat inputs and variable fluid flows, it is essential to predict CHFs accurately for effective and efficient two-phase microchannel cooling. To characterize the CHF and pressure drop in flow boiling microchannels, a separated-flow model is proposed in this paper based on fundamental two-phase flow mass, energy, momentum conservation and wall energy conservation laws. With this theoretical framework, the relationship among liquid/vapor interfacial instability, two-phase flow characteristics and CHF is further studied. This mechanistic model also provides insight into the design and operational guidelines for advanced electronics and photonics cooling technologies.

scholarly journals Evaluation of Pressure Drop of Two-Phase Flow Boiling with R290 in Horizontal Mini Channel

2021 ◽  
Vol 89 (2) ◽  
pp. 160-166
Author(s):  
Fajriocta Umar ◽  
Jong Taek Oh ◽  
Agus Sunjarianto Pamitran
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Phase Flow ◽  
Two Phase ◽  
Mass Fluxes ◽  
Channel Tube ◽  
Inner Diameter

Various experiments on the pressure drop of a two-phase flow boiling in a mini channel tube have been carried out. This study is aimed at characteristics of the pressure drop of a two-phase flow boiling using a refrigerant R290. The experiment uses a horizontal, stainless steel, 2-m-long mini-channel tube with a 3-mm inner diameter. The experiment has been carried out using various data with the vapor qualities ranging from 0.1 to 0.9, the mass fluxes ranging 50 kg/m2s to 180 kg/m2s, and the heat fluxes ranging from 5 kW/m2 to 20 kW/m2. Furthermore, several homogeneous and separated methods were used to predict the experimental data. Li and Hibiki’s correlation give the best overall deviation pressure drop value is the most accurate with its deviation amounting 19.47%.

Pressure drop characteristics for two-phase flow of FC-72 in microchannel

2017 ◽  
Vol 232 (6) ◽  
pp. 987-997 ◽  
Author(s):  
Yong-Seok Choi ◽  
Tae-Woo Lim ◽  
Sam-Sang You ◽  
Hwan-Seong Kim
Keyword(s):  
Pressure Drop ◽  
Two Phase Flow ◽  
Separated Flow ◽  
Absolute Error ◽  
Experimental Results ◽  
Phase Flow ◽  
Vapor Quality ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Rate Of Increase

In this paper, an experimental study on two-phase flow pressure drop of refrigerant FC-72 is carried out in a microchannel. The microchannel has a width and depth of 0.45 and 0.2 mm respectively, and comprises 15 parallel channels with a length of 60 mm. The experiment is conducted under the condition of mass flux of 100.3–458.0 kg/m2s and heat flux of 3.2–49.0 kW/m2. This study analyzed the pressure drop characteristics for two-phase flow by using a separated flow model. To predict the frictional pressure drop, two-phase frictional multiplier obtained from experiments is compared with the existing correlations. The experimental results show that two-phase frictional multipliers rely heavily on the vapor quality. Fractional pressure drop increases as the vapor quality increases. However, the rate of increase in the high vapor quality region decreases as the vapor quality increases. Based on pressure drop characteristics obtained from the experiments, a new correlation is proposed to predict the frictional pressure drop. Two-phase multiplier is modified with the dimensionless parameters such as Reynolds number, Weber number, and Martinelli parameter. The newly developed correlation predicts the experimental results well within a mean absolute error of 8.0%.

Two-Phase Flow Through Square and Circular Microchannels—Effects of Channel Geometry

2004 ◽  
Vol 126 (4) ◽  
pp. 546-552 ◽  
Author(s):  
Peter M.-Y. Chung ◽  
Masahiro Kawaji ◽  
Akimaro Kawahara ◽  
Yuichi Shibata
Keyword(s):  
Pressure Drop ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Separated Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Channel Geometry ◽  
Frictional Pressure Drop ◽  
Channel Shape

An adiabatic experiment was conducted to investigate the effect of channel geometry on gas-liquid two-phase flow characteristics in horizontal microchannels. A water-nitrogen gas mixture was pumped through a 96 μm square microchannel and the resulting flow pattern, void fraction and frictional pressure drop data were compared with those previously reported by the authors for a 100 μm circular microchannel. The pressure drop data were best estimated using a separated-flow model and the void fraction increased non-linearly with volumetric quality, regardless of the channel shape. However, the flow maps exhibited transition boundaries that were shifted depending on the channel shape.

Numerical Simulation of Forced Convective Boiling in a Microchannel

2018 ◽  
Vol 10 (4) ◽  
Author(s):  
Yun Whan Na ◽  
J. N. Chung
Keyword(s):  
Numerical Simulation ◽  
Two Phase Flow ◽  
Liquid Velocity ◽  
Flow Boiling ◽  
Simulation Method ◽  
Flow Patterns ◽  
Heat Fluxes ◽  
Phase Flow ◽  
Two Phase ◽  
Convective Boiling

Forced convective flow boiling in a single microchannel with different channel heights was studied through a numerical simulation method to investigate bubble dynamics, two-phase flow patterns, and boiling heat transfer. The momentum and energy equations were solved using a finite volume (FV) numerical method, while the liquid–vapor interface of a bubble is captured using the volume of fluid (VOF) technique. The effects of different constant wall heat fluxes and different channel heights on the boiling mechanisms were investigated. The effects of liquid velocity on the bubble departure diameter were also analyzed. The predicted bubble shapes and distribution profiles together with two-phase flow patterns are also provided.

INVESTIGATION ON VOID FRACTION FOR TWO-PHASE FLOW PRESSURE DROP OF EVAPORATIVE R-290 IN HORIZONTAL TUBE

2016 ◽  
Vol 78 (8-4) ◽  
Author(s):  
Agus Sunjarianto Pamitran ◽  
Sentot Novianto ◽  
Normah Mohd-Ghazali ◽  
Nasruddin Nasruddin ◽  
Raldi Koestoer
Keyword(s):  
Pressure Drop ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Homogeneous Model ◽  
Saturation Temperature ◽  
Horizontal Tube ◽  
Phase Flow ◽  
Two Phase ◽  
Experimental Conditions

Two-phase flow boiling pressure drop experiment was conducted to observe its characteristics and to develop a new correlation of void fraction based on the separated model. Investigation is completed on the natural refrigerant R-290 (propane) in a horizontal circular tube with a 7.6 mm inner diameter under experimental conditions of 3.7 to 9.6 °C saturation temperature, 10 to 25 kW/m2 heat flux, and 185 to 445 kg/m2s mass flux. The present experimental data was used to obtain the calculated void fraction which then was compared to the predicted void fraction with 31 existing correlations. A new void fraction correlation for predicting two-phase flow boiling pressure drop, as a function of Reynolds numbers, was proposed. The measured pressure drop was compared to the predicted pressure drop with some existing pressure drop models that use the newly developed void fraction model. The homogeneous model of void fraction showed the best prediction with 2% deviation

Two-Phase Flow and Heat Transfer in Rectangular Micro-Channels

2004 ◽  
Vol 126 (3) ◽  
pp. 288-300 ◽  
Author(s):  
Weilin Qu ◽  
Seok-Mann Yoon ◽  
Issam Mudawar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Flow Patterns ◽  
Heat Sinks ◽  
Phase Flow ◽  
Micro Channel ◽  
Two Phase

Knowledge of flow pattern and flow pattern transitions is essential to the development of reliable predictive tools for pressure drop and heat transfer in two-phase micro-channel heat sinks. In the present study, experiments were conducted with adiabatic nitrogen-water two-phase flow in a rectangular micro-channel having a 0.406×2.032mm2 cross-section. Superficial velocities of nitrogen and water ranged from 0.08 to 81.92 m/s and 0.04 to 10.24 m/s, respectively. Flow patterns were first identified using high-speed video imaging, and still photos were then taken for representative patterns. Results reveal the dominant flow patterns are slug and annular, with bubbly flow occurring only occasionally; stratified and churn flow were never observed. A flow pattern map was constructed and compared with previous maps and predictions of flow pattern transition models. Features unique to two-phase micro-channel flow were identified and employed to validate key assumptions of an annular flow boiling model that was previously developed to predict pressure drop and heat transfer in two-phase micro-channel heat sinks. This earlier model was modified based on new findings from the adiabatic two-phase flow study. The modified model shows good agreement with experimental data for water-cooled heat sinks.

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