Performance of Two-Phase Microchannels at Sub-Atmospheric Pressure

2006 ◽  
Author(s):  
Tao Tong ◽  
Shankar Devasenathipathy ◽  
Je-Young Chang ◽  
John Dirner ◽  
Suzana Prstic ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Atmospheric Pressure ◽  
High Speed ◽  
Flow Boiling ◽  
Ambient Pressure ◽  
Saturation Temperature ◽  
Heat Removal ◽  
Working Fluid ◽  
Cold Plate ◽  
Two Phase

Two-phase microchannel system is a promising technology to achieve enhanced heat removal and more effective cooling of hotspots. The excellent thermodynamic properties of water make it a prime candidate as the working fluid in two-phase microchannel systems. While typical integrated circuit components require die temperature to remain below 95 °C, most of the earlier microchannel flow boiling studies were conducted at or above ambient pressure, where the saturation temperature of water is equal to or higher than 100 °C. In this paper, we tested flow boiling at sub-atmospheric pressure such that the saturation temperature of water can be significantly reduced below 95 °C. We study the pressure drop and heat transfer characteristics of our two-phase cold plate configuration, under uniform and hotspot (non-uniform) heating conditions at sub-atmospheric system pressures. A cold plate with 61 μm wide and 272 μm deep microchannels was tested at two systems pressures of 35 and 46 kPa and at two mass flow rates of 67 and 107 kg/m2-s. High-speed flow imaging was used for identifying flow patterns in the microchannels with the above test conditions. Pressure drop data were compared with the available semi-empirical correlations and the annular flow model. An explanation was proposed for the mismatch between the models under current microchannel configuration.

Experimental Investigation of Flow Boiling Pressure Drop of R134A in a Microscale Horizontal Smooth Tube

2011 ◽  
Vol 3 (1) ◽  
Author(s):  
Cristiano Bigonha Tibiriçá ◽  
Jaqueline Diniz da Silva ◽  
Gherhardt Ribatski
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Flow Boiling ◽  
Smooth Tube ◽  
Working Fluid ◽  
Prediction Methods ◽  
Internal Diameter ◽  
Two Phase ◽  
Pressure Drops ◽  
Frictional Pressure Drop

This paper presents new experimental flow boiling pressure drop results in a microscale tube. The experimental data were obtained under diabatic conditions in a horizontal smooth tube with an internal diameter of 2.32 mm. Experiments were performed with R134a as working fluid, mass velocities ranging from 100 kg/m2 s to 600 kg/m2 s, heat flux ranging from 10 kW/m2 to 55 kW/m2, saturation temperatures of 31°C, and exit vapor qualities from 0.20 to 0.99. Flow pattern characterization was also performed from images obtained by high-speed filming. Pressure drop gradients up to 48 kPa/m were measured. These data were carefully analyzed and compared against 13 two-phase frictional pressure drop prediction methods, including both macro- and microscale methods. Comparisons against these methods based on the data segregated according to flow patterns were also performed. Overall, the method by Cioncolini et al. (2009, “Unified Macro-to-Microscale Method to Predict Two-Phase Frictional Pressure Drops of Annular Flows,” Int. J. Multiphase Flow, 35, pp. 1138–1148) provided quite accurate predictions of the present database.

Performances of Silicon Micro-Flow-Passage Cold Plates From Single-Phase to Two-Phase With Water and HFE-7100 as Working Fluids

2007 ◽  
Author(s):  
Tao Tong ◽  
Je-Young Chang ◽  
Shankar Devasenathipathy ◽  
John Dirner ◽  
Suzana Prstic ◽  
...  
Keyword(s):  
Phase Change ◽  
Flow Boiling ◽  
Ambient Pressure ◽  
Heat Removal ◽  
Operating Conditions ◽  
Working Fluid ◽  
Channel Height ◽  
Two Phase ◽  
Working Fluids ◽  
Cold Plates

Two-phase (phase-change) microchannel (MC) system is a promising technology for achieving enhanced heat removal for highdensity electronics. Yet phase-change studies in MCs with hydraulic diameters on the order of several hundred micrometers or smaller have been inconclusive. Most of earlier studies involved one specific channel design and one type of working fluid. It is thus difficult to make fair comparisons across various experimental works toward recommending the best design option for real applications under specific operating conditions. In the current work, flow boiling experiments were conducted for MC cold plates with channel widths ranging from 61 μm to 330 μm and channel height ∼ 300 μm (hydraulic diameters from ∼ 100 μm to ∼ 337 μm) and a pin-fin array cold plate with fin size and inter-spacing ∼ 150 μm. Two working fluids, deionized water at sub-atmospheric pressure (∼ 25 kPa to 45 kPa) and HFE-7100 at ambient pressure, were tested respectively. High-speed visualization facilities were employed to help understand the rapid phase-change processes inside the flow passages. Pressure drop and heat transfer characteristics of the microchannel cold plates under various heat flux and flow rate conditions were recorded and analyzed as well as boiling fluctuations. Detailed visualization results will be presented in a separate paper [Tong et al., IMECE2007-42028].

Experimental Investigation of Flow Boiling Pressure Drop of R134a in a Micro-Scale Horizontal Smooth Tube

2010 ◽  
Author(s):  
Cristiano Bigonha Tibiric¸a´ ◽  
Gherhardt Ribatski
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Flow Boiling ◽  
Smooth Tube ◽  
Working Fluid ◽  
Internal Diameter ◽  
Two Phase ◽  
Pressure Drops ◽  
Micro Scale ◽  
Frictional Pressure Drop

This paper presents new experimental flow boiling pressure drop results in a microscale tube. The experimental data were obtained under diabatic conditions in a horizontal smooth tube with internal diameter of 2.3 mm. Experiments were performed with R134a as working fluid, mass velocities ranging from 100 to 600 kg/m2s, heat flux ranging from 10 to 55 kW/m2, saturation temperatures of 31 °C, and exit vapor qualities from 0.20 to 0.99. Flow pattern characterization was also performed from images obtained by high-speed filming. Pressure drops up to 48 kPa/m were measured. These data were carefully analyzed and compared against 13 two-phase frictional pressure drop prediction methods, including both macro- and micro-scale methods. Comparisons against these methods based on the data segregated according to flow patterns were also performed. Overall, the method by Cioncolini et al. [1] provided quite accurate predictions of the present database.

scholarly journals Experimental validation of pressure drop models during flow boiling of R134a – effect of flow acceleration and entrainment

2018 ◽  
Vol 240 ◽  
pp. 03010
Author(s):  
Tomasz Muszynski ◽  
Rafal Andrzejczyk ◽  
Carlos Dorao
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
High Heat ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Flow Acceleration ◽  
High Heat Transfer

A crucial step to assure proficient work of power and process apparatus is their proper design. A wide array of those devices operates within boiling or condensation of the working fluid to benefit from high heat transfer rates. Two-phase flows are associated with high heat transfer coefficients because of the latent heat of evaporation and high turbulence level between the liquid and the solid surface. Predicting heat transfer coefficient and pressure drop is a challenging task, and has been pursued by researchers for decades. In the case of diabatic flows, the total pressure drop is due to the change in kinetic and potential energy. The article presents detailed boiling pressure drops data for R134a at a saturation temperature of 19.4°C. Study cases have been set for a mass flux varying from 300 to 500 kg/m2s. Presented data along with the data reduction procedure was used to obtain the momentum pressure drop values during flow boiling. The study focuses on experimental values of momentum pressure drop component and its prediction based on various void fraction models and entrainment effects.

Two-Phase Flow in Microchannels

2001 ◽  
Author(s):  
G. Hetsroni ◽  
A. Mosyak ◽  
Z. Segal
Keyword(s):  
Heat Sink ◽  
High Speed ◽  
Single Phase ◽  
Flow Boiling ◽  
Electronics Cooling ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Two Phase ◽  
Infrared Radiometry ◽  
Phase Water

Abstract Experimental investigation of a heat sink for electronics cooling is performed. The objective is to keep the operating temperature at a relatively low level of about 323–333K, while reducing the undesired temperature variation in both the streamwise and transverse directions. The experimental study is based on systematic temperature, flow and pressure measurements, infrared radiometry and high-speed digital video imaging. The heat sink has parallel triangular microchannels with a base of 250μm. According to the objectives of the present study, Vertrel XF is chosen as the working fluid. Experiments on flow boiling of Vertrel XF in the microchannel heat sink are performed to study the effect of mass velocity and vapor quality on the heat transfer, as well as to compare the two-phase results to a single-phase water flow.

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

Experimental Investigation of Flow Patterns, Pressure Drop, and Flow Instability During Flow Boiling in a Cross-Linked Microchannel Heat Sink

2010 ◽  
Author(s):  
Ayman Megahed
Keyword(s):  
Pressure Drop ◽  
Flow Visualization ◽  
Mass Flux ◽  
Heat Sink ◽  
Flow Instability ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Microchannel Heat Sink ◽  
Two Phase ◽  
Phase Pressure

This paper investigates experimentally flow boiling characteristics in a cross-linked microchannel heat sink at low mass fluxes and high heat fluxes. The heat sink consists of 45 straight microchannels with a hydraulic diameter of 248 μm and heated length of 16 mm. Three cross-links, of width 500 μm, are introduced in the present microchannel heat sink to achieve better temperature uniformity and to avoid flow maldistribution. Flow visualization, flow instability, and two-phase pressure drop measurements are conducted using the dielectric coolant FC-72 for the range of heat flux from 20.1 to 104.2 kW/m2, mass flux from 109 to 290 kg/m2.s, and exit quality from 0.02 to 0.65. Flow visualization studies indicate that the observed flow regime is primarily slug. Instability results show that the periods and amplitudes of inlet pressure and outlet saturation temperature oscillations decrease with increasing mass flux. The two-phase pressure drop strongly increases with the exit quality and the two-phase frictional pressure drop increases by a factor of 1.6–2, at xe, o < 0.3, as compared with that in the straight microchannel heat sink.

Pressure Drop of Two-Phase Flow Boiling with R-22 and R-290 in 7.6 mm Diameter Tube

2016 ◽  
Vol 818 ◽  
pp. 23-27
Author(s):  
Agus Sunjarianto Pamitran ◽  
Nasruddin ◽  
Helmi Dadang Ardiansyah ◽  
Muhammad Idrus Alhamid
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Phase Flow ◽  
Lower Mass ◽  
Two Phase ◽  
Experimental Pressure

The characteristics of two-phase flow boiling of R-290 are required for replacing R-22 that has been phased-out. The present study focuses on experimental pressure drop for R-22 and R-290. The experiment was run with heat flux of 5.09 kW/m2 to 19.03 kW/m2, mass flux of 114.91 kg/m2s to 751.74 kg/m2s and saturation temperature of 4.77°C to 18.12°C. The present result showed that pressure drop was affected by heat flux, mass flux and saturation temperature. Lower mass flux, heat flux and saturation temperature results in lower pressure drop. The pressure drop of R-290 is lower than that of R-22. Among the existing pressure drop prediction methods, Lokhart-Martinelli (1949) gives the best prediction for the present pressure drop data.

Micro-Scale Flow Pattern Classification Based on the K-Means Clustering Algorithm

2010 ◽  
Author(s):  
Daniel Sempe´rtegui ◽  
Gherhardt Ribastki
Keyword(s):  
Flow Pattern ◽  
High Speed ◽  
Clustering Algorithm ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Flow Patterns ◽  
Statistical Characteristics ◽  
Phase Flow ◽  
Two Phase

In the present work, an objective method to characterize two-phase flow pattern was developed and implemented. The method is based on the characteristics of the signals provided by transducers measuring local temperature and pressure plus the intensity of a laser beam crossing the two-phase flow. The statistical characteristics of these signals were used as input features for the k-means clustering method. In order to implement the method, experimental flow patterns were obtained during flow boiling of R245fa in a 2.32 mm ID tube. Experiments were performed for mass velocities from 100 to 700kg/m2s, saturation temperature of 31 °C and vapor qualities up to 0.99. The cluster classification was compared against flow patterns segregated based on high speed camera images (8000 images/s) and a reasonable agreement was obtained.

scholarly journals Research on pumped two-phase single-sided cold plate of IGBT for rail transit applications

2021 ◽  
Author(s):  
Hui Wu ◽  
Gang Zhang ◽  
Zhaozan Feng ◽  
Kai He ◽  
Lei Yao ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Flow Boiling ◽  
Working Fluid ◽  
Base Temperature ◽  
Cold Plate ◽  
Two Phase ◽  
Insulated Gate Bipolar Transistor ◽  
Error Band

ABSTRACT The use of pumped two-phase cooling to improve the thermal management of insulated gate bipolar transistor (IGBT) in rail transportation is a novel cooling technology. An experimental investigation on pumped two-phase cold plate of IGBT used in HXD1C locomotives was conducted at a mass flow rate of 0.1 kg/s–0.29 kg/s and a heat flux of 6.2 W/cm2, with R245fa as the working fluid. The experimental results showed that the base temperature nonuniformity can be controlled within 2.2 °C at flow rates of 0.14 kg/s and 0.19 kg/s, which is of great benefit to the reliability of IGBT. Based on well known correlations for saturated flow boiling in tubes, an analytical model was developed and compared with the experimental data. The model could predict the base temperature data within an error band of ±3 °C, as well as capture the trend of base temperature as a function of vapour quality and mass flow rate. The performance of the pumped two-phase cold plate of IGBT could be further improved with the aid of the developed model.

Sign in / Sign up

Export Citation Format

Share Document