Parametric Study of a Thermosyphon Loop Pressure Drop Model

2004 ◽  
Author(s):  
Jinsong Zhang ◽  
Jason Hugenroth ◽  
Issam Mudawar ◽  
Timothy S. Fisher
Keyword(s):  
Heat Flux ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Flow Boiling ◽  
Current System ◽  
Experimental Studies ◽  
Two Phase ◽  
Flow Area ◽  
Cross Sectional

A closed loop two-phase thermosyphon has been modeled based on earlier experimental and numerical studies by Mukherjee and Mudawar [1, 2]. Unlike conventional thermosyphons in which the heat dissipating device is submerged in a pool of liquid coolant, the current system uses a flow boiling arrangement. The advantage is that for a given boiling surface area, the critical heat flux (CHF) can be increased. Parametric studies with respect to adiabatic section flow areas, boiler section flow area, and system height were performed. The maximum practical heat flux that is attainable is predicted, as well as other flow parameters such as mass flow rate, flow velocities and fluid quality existing the boiler. Performance enhancements relative to the original system, may be possible by introducing a divergent cross sectional area in the boiler section that increases the system mass flow rate. It can also, however, reduce the flow velocity in certain sections of the boiler, tending to reduce the boiler CHF. Experimental studies are recommended to determine if an actual improvement can be realized.

Numerical Study of Laminar Mixed Convection of a Nanofluid in a Horizontal Curved Tube with Constant Heat Flux and Mass Flow Rate

2011 ◽  
Vol 110-116 ◽  
pp. 3657-3662
Author(s):  
S. Alikhani ◽  
A. Behzadmehr ◽  
S. Mirmasoumi
Keyword(s):  
Heat Flux ◽  
Mixed Convection ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Volume Fraction ◽  
Numerical Study ◽  
Two Phase ◽  
Curved Tube ◽  
Laminar Mixed Convection

Fully developed laminar mixed convection of a nanofluid (water/Al2O3) in a horizontal curved tube is numerically investigated. Three-dimensional elliptic governing equations have been solved to show how nanoparticle concentration affects on thermal and hydrodynamic parameters while these parameters are impressed by centrifugal and buoyancy forces under constant mass flow rate and heat flux. Comparisons with previously published experimental works on horizontal curved tubes show good agreements between the results. Results which are obtained using the two – phase mixture model indicate that adding the nanoparticles causes changes in the properties of nanofluid and finally increases the temperature of the flow. Furthermore, increasing nanoparticles volume fraction at first augments the heat transfer coefficient of nanofluid and then, for higher concentration of particles, decreases this thermal parameter of nanofluid.

Two-phase natural circulation loop behaviour at atmospheric and subatmospheric conditions

2018 ◽  
Vol 233 (4) ◽  
pp. 687-700
Author(s):  
S Venkata Sai Sudheer ◽  
K Kiran Kumar ◽  
Karthik Balasubramanian
Keyword(s):  
Heat Flux ◽  
Physical Properties ◽  
Spatial Variation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Natural Circulation ◽  
Two Phase ◽  
Natural Circulation Loop ◽  
Thermo Physical Properties

This paper aims to present the steady-state behaviour of two-phase natural circulation loop at atmospheric and sub-atmospheric conditions. One-dimensional numerical approach is adopted to evaluate various system parameters, with special emphasis on spatial variation of thermo-physical properties and flashing. Homogeneous equilibrium model is applied for two-phase flows. An in-house code is developed in MATLAB to solve numerical model iteratively. It is observed that consideration of spatial variation of thermo-physical properties can precisely predict the loop behaviour. The evaluated results are validated with the open literature and reasonably good agreement is observed. The heater inlet temperature, inlet pressure and heat flux are found to have significant influence on spatial variation of pressure, temperature and enthalpy. As system pressure decreases from atmospheric to sub-atmospheric (1–0.8 atm), it is observed that the sub-atmospheric loop gives a higher mass flow rate compared to atmospheric loop at lower heat fluxes. However, as the heat flux increases in the sub-atmospheric loop, the mass flow rate is reduced due to increased drag force in the loop.

Effect of Nanoparticle Concentration on Thermo-Hydraulic Behavior of a Nanofluid in a Horizontal Tube with Constant Heat Flux and Mass Flow Rate

2011 ◽  
Vol 110-116 ◽  
pp. 3650-3656
Author(s):  
S. Mirmasoumi ◽  
A. Behzadmehr
Keyword(s):  
Heat Flux ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Horizontal Tube ◽  
Constant Heat Flux ◽  
Tube Length ◽  
Nanoparticle Concentration ◽  
Constant Heat ◽  
Two Phase

How nanoparticle concentration affects on thermal and hydrodynamic parameters of a nanofluid (water+Al2O3) is numerically investigated in a horizontal tube while these parameters are impressed by buoyancy force under constant heat flux and mass flow rate. Comparisons with previously published experimental and numerical works on mixed convection in horizontal tubes show good agreements between the results. Results which are obtained using the two – phase mixture model indicate that adding the nanoparticles causes changes in the properties of nanofluid and finally increases the temperature of the flow. Whereas, dimensionless pressure drop along the tube length could increase with the nanoparticle concentration.

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.

Thermal Characterization of Interlayer Microfluidic Cooling of Three-Dimensional Integrated Circuits With Nonuniform Heat Flux

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Yoon Jo Kim ◽  
Yogendra K. Joshi ◽  
Andrei G. Fedorov ◽  
Young-Joon Lee ◽  
Sung-Kyu Lim
Keyword(s):  
Integrated Circuits ◽  
Mass Flow Rate ◽  
Thermal Management ◽  
Mass Flow ◽  
Flow Rate ◽  
Single Phase ◽  
Hot Spot ◽  
Three Dimensional ◽  
Two Phase ◽  
Two Phase Cooling

It is now widely recognized that the three-dimensional (3D) system integration is a key enabling technology to achieve the performance needs of future microprocessor integrated circuits (ICs). To provide modular thermal management in 3D-stacked ICs, the interlayer microfluidic cooling scheme is adopted and analyzed in this study focusing on a single cooling layer performance. The effects of cooling mode (single-phase versus phase-change) and stack/layer geometry on thermal management performance are quantitatively analyzed, and implications on the through-silicon-via scaling and electrical interconnect congestion are discussed. Also, the thermal and hydraulic performance of several two-phase refrigerants is discussed in comparison with single-phase cooling. The results show that the large internal pressure and the pumping pressure drop are significant limiting factors, along with significant mass flow rate maldistribution due to the presence of hot-spots. Nevertheless, two-phase cooling using R123 and R245ca refrigerants yields superior performance to single-phase cooling for the hot-spot fluxes approaching ∼300 W/cm2. In general, a hybrid cooling scheme with a dedicated approach to the hot-spot thermal management should greatly improve the two-phase cooling system performance and reliability by enabling a cooling-load-matched thermal design and by suppressing the mass flow rate maldistribution within the cooling layer.

Thermal and Fluid Dynamic Behavior of a Horizontal Channel With Adiabatic Moving Lower Plate

2005 ◽  
Author(s):  
Assunta Andreozzi ◽  
Vincenzo Naso ◽  
Oronzio Manca
Keyword(s):  
Heat Flux ◽  
Reynolds Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Horizontal Channel ◽  
Lower Plate ◽  
Stationary Condition ◽  
Moving Plate ◽  
Plate Velocity

In this study a numerical investigation of mixed convection in air in horizontal parallel walled channels with moving lower plate is carried out. The moving lower plate has a constant velocity and it is adiabatic, whereas the upper one is heated at uniform heat flux. The effects of horizontal channel height, heat flux and moving plate velocity are analyzed. Results in terms of temperature and stream function fields are given and the mass flow rate per unit of length and divided by the dynamic viscosity is reported as a function of Reynolds number based on the moving plate velocity. For stationary condition of lower plate, a typical C–loop inside the horizontal channel is detected. Different flow motions are observed in the channel and the two reservoirs, depending on the heat flux values and the distance between the heated upper stationary plate and lower adiabatic moving plate. The dimensionless induced mass flow rate presents different increase between the Reynolds number lower or greater than 1000.

scholarly journals Development of Hybrid Airlift-Jet Pump with Its Performance Analysis

2018 ◽  
Vol 8 (9) ◽  
pp. 1413 ◽  
Author(s):  
Dan Yao ◽  
Kwongi Lee ◽  
Minho Ha ◽  
Cheolung Cheong ◽  
Inhiug Lee
Keyword(s):  
Boundary Conditions ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Jet Pump ◽  
Two Phase

A new pump, called the hybrid airlift-jet pump, is developed by reinforcing the advantages and minimizing the demerits of airlift and jet pumps. First, a basic design of the hybrid airlift-jet pump is schematically presented. Subsequently, its performance characteristics are numerically investigated by varying the operating conditions of the airlift and jet parts in the hybrid pump. The compressible unsteady Reynolds-averaged Navier-Stokes equations, combined with the homogeneous mixture model for multiphase flow, are used as the governing equations for the two-phase flow in the hybrid pump. The pressure-based methods combined with the Pressure-Implicit with Splitting of Operators (PISO) algorithm are used as the computational fluid dynamics techniques. The validity of the present numerical methods is confirmed by comparing the predicted mass flow rate with the measured ones. In total, 18 simulation cases that are designed to represent the various operating conditions of the hybrid pump are investigated: eight of these cases belong to the operating conditions of only the jet part with different air and water inlet boundary conditions, and the remaining ten cases belong to the operating conditions of both the airlift and jet parts with different air and water inlet boundary conditions. The mass flow rate and the efficiency are compared for each case. For further investigation into the detailed flow characteristics, the pressure and velocity distributions of the mixture in a primary pipe are compared. Furthermore, a periodic fluctuation of the water flow in the mass flow rate is found and analyzed. Our results show that the performance of the jet or airlift pump can be enhanced by combining the operating principles of two pumps into the hybrid airlift-jet pump, newly proposed in the present study.

Research on Two-Phase Flow Instability in Evaporator of Refrigeration System

2010 ◽  
Author(s):  
Nan Liang ◽  
Changqing Tian ◽  
Shuangquan Shao
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Density Wave ◽  
Phase Flow ◽  
Constant Mass ◽  
Refrigeration System ◽  
Two Phase

As one kind of fluid machinery related to the two-phase flow, the refrigeration system encounters more problems of instability. It is essential to ensure the stability of the refrigeration systems for the operation and efficiency. This paper presents the experimental investigation on the static and dynamic instability in an evaporator of refrigeration system. The static instability experiments showed that the oscillatory period and swing of the mixture-vapor transition point by observation with a camera through the transparent quartz glass tube at the outlet of the evaporator. The pressure drop versus mass flow rate curves of refrigerant two phase flow in the evaporator were obtained with a negative slope region in addition to two positive slope regions, thus making the flow rate a multi-valued function of the pressure drop. For dynamic instabilities in the evaporation process, three types of oscillations (density wave type, pressure drop type and thermal type) were observed at different mass flow rates and heat fluxes, which can be represented in the pressure drop versus mass flow rate curves. For the dynamic instabilities, density wave oscillations happen when the heat flux is high with the constant mass flow rate. Thermal oscillations happen when the heat flux is correspondingly low with constant mass flow rate. Though the refrigeration system do not have special tank, the accumulator and receiver provide enough compressible volume to induce the pressure drop oscillations. The representation and characteristic of each oscillation type were also analyzed in the paper.

Heat Transfer and Flow Friction Characteristics for Compact Cold Plates

2003 ◽  
Vol 125 (1) ◽  
pp. 104-113 ◽  
Author(s):  
Chang-Yuan Liu ◽  
Ying-Huei Hung
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Thermal Resistance ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Average Nusselt Number ◽  
Cold Plate ◽  
Air Mass

Both experimental and theoretical investigations on the heat transfer and flow friction characteristics of compact cold plates have been performed. From the results, the local and average temperature rises on the cold plate surface increase with increasing chip heat flux or decreasing air mass flow rate. Besides, the effect of chip heat flux on the thermal resistance of cold plate is insignificant; while the thermal resistance of cold plate decreases with increasing air mass flow rate. Three empirical correlations of thermal resistance in terms of air mass flow rate with a power of −0.228 are presented. As for average Nusselt number, the effect of chip heat flux on the average Nusselt number is insignificant; while the average Nusselt number of the cold plate increases with increasing Reynolds number. An empirical relationship between Nu¯cp and Re can be correlated. In the flow frictional aspect, the overall pressure drop of the cold plate increases with increasing air mass flow rate; while it is insignificantly affected by chip heat flux. An empirical correlation of the overall pressure drop in terms of air mass flow rate with a power of 1.265 is presented. Finally, both heat transfer performance factor “j” and pumping power factor “f” decrease with increasing Reynolds number in a power of 0.805; while they are independent of chip heat flux. The Colburn analogy can be adequately employed in the study.

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