Heat Transfer Optimization in Laminar Flow of Non-Linear Viscoelastic Fluids in Asymmetric Straight Ducts With Inclusions

2017 ◽  
Author(s):  
Mario F. Letelier ◽  
Dennis A. Siginer ◽  
Gabriel Arriagada ◽  
Amaru González
Keyword(s):  
Heat Transfer ◽  
Cross Sections ◽  
Circular Cross Section ◽  
Working Fluid ◽  
Flow Strength ◽  
Optimization Study ◽  
Non Linear ◽  
Linear Viscoelastic ◽  
Eccentric Tube ◽  
Transversal Flow

This paper presents the preliminary findings of an optimization study of transversal flow strength in tube cross-sections with arbitrary external contours and an internal inclusion. The eccentric tube contours are generated through a one-to-one mapping of a base circular cross-section. The working fluid obeys the non-linear modified Phan-Thien-Tanner (MPTT) constitutive model. The computation of the total transversal flow rate leads to the determination of effective cross-sections for heat transfer enhancement.

scholarly journals Effect of liquid cooling on PCR performance with the parametric study of cross-section shapes of microchannels

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yousef Alihosseini ◽  
Mohammad Reza Azaddel ◽  
Sahel Moslemi ◽  
Mehdi Mohammadi ◽  
Ali Pormohammad ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Heat Sink ◽  
Evaluation Criteria ◽  
Circular Cross Section ◽  
Microchannel Heat Sink ◽  
Liquid Cooling ◽  
Maximum Heat ◽  
Maximum Heat Transfer

AbstractIn recent years, PCR-based methods as a rapid and high accurate technique in the industry and medical fields have been expanded rapidly. Where we are faced with the COVID-19 pandemic, the necessity of a rapid diagnosis has felt more than ever. In the current interdisciplinary study, we have proposed, developed, and characterized a state-of-the-art liquid cooling design to accelerate the PCR procedure. A numerical simulation approach is utilized to evaluate 15 different cross-sections of the microchannel heat sink and select the best shape to achieve this goal. Also, crucial heat sink parameters are characterized, e.g., heat transfer coefficient, pressure drop, performance evaluation criteria, and fluid flow. The achieved result showed that the circular cross-section is the most efficient shape for the microchannel heat sink, which has a maximum heat transfer enhancement of 25% compared to the square shape at the Reynolds number of 1150. In the next phase of the study, the circular cross-section microchannel is located below the PCR device to evaluate the cooling rate of the PCR. Also, the results demonstrate that it takes 16.5 s to cool saliva samples in the PCR well, which saves up to 157.5 s for the whole amplification procedure compared to the conventional air fans. Another advantage of using the microchannel heat sink is that it takes up a little space compared to other common cooling methods.

Thermo-Fluidic Characteristics in a Cross-Linked Silicon Microchannel Heat Sink

2007 ◽  
Author(s):  
R. Muwanga ◽  
I. Hassan
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cross Sections ◽  
Heat Sink ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Significant Difference ◽  
The Cross

This paper presents the flow and heat transfer characteristics in a cross-linked silicon microchannel heat sink. The heat sink is composed of 45 channels, 270 μm wide × 285 μm tall in a silicon substrate formed via deep reactive ion etching. A detailed discussion of the pressure drop data reduction is described, including characterization of the channel cross-sections and methods to account for inlet and exit loss coefficients. No significant difference is observed in the pressure drop measurements between the cross-linked and standard heat sinks flowing air and water. The use of un-encapsulated liquid crystal thermography was successfully utilized to obtain local heat transfer data with FC-72 as the working fluid. The heat transfer results show inflections in the thermal profile due to the cross-links.

scholarly journals Experimental study on the performance limitation of micro heat pipes of non circular cross-sections

2008 ◽  
Vol 12 (3) ◽  
pp. 91-102 ◽  
Author(s):  
Lutful Mahmood ◽  
Razzaq Akhanda
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Performance ◽  
Cross Sections ◽  
Heat Pipes ◽  
Working Fluid ◽  
Electric Heater ◽  
Condenser Section ◽  
Inclination Angles ◽  
Micro Heat Pipes

An experimental study of three different cross-sections (circular, semicircular and rectangular) of micro heat pipes having same hydraulic diameter (D= 3mm) is carried out at three different inclination angles (0?, 45?, 90?) using water as the working fluid. Evaporator section of the pipe is heated by an electric heater and the condenser section is cooled by water circulation in an annular space between the condenser section and the water jacket. Temperatures at different locations of the pipe are measured using five calibrated K type thermocouples. Heat supply is varied using a voltage regulator which is measured by a precision ammeter and a voltmeter. It is found that thermal performance tends to deteriorate as the micro heat pipe is flattened. Thus among all cross-sections of the pipes circular cross-section exhibits the best thermal performance followed by semicircular and rectangular cross-sections. Moreover maximum heat transfer capability of the pipes also decreases with decreasing of its inclination angle. A correlation is developed using all the gathered data of the present study to predict the heat transfer coefficient of micro heat pipes of different cross-sections placed at different inclination angles.

scholarly journals An experimental investigations of the single phase fluid flow through mini pipes with circular cross section

2020 ◽  
Vol XXIII (2) ◽  
pp. 25-31
Author(s):  
Avram Elena Rita
Keyword(s):  
Fluid Flow ◽  
Cross Sections ◽  
Circular Cross Section ◽  
Experimental Results ◽  
Working Fluid ◽  
Total Hardness ◽  
Experimental Investigations ◽  
Turbulent Friction ◽  
Pressure Drops ◽  
Flow Through

The experimental investigation that has been conducted on the fluid flow in mini pipes with circular cross-sections are presented in this paper. The working fluid is water and its main physical-chemical analysis (pH, total hardness, electrical conductivity) were carried out. The liquid flow through mini pipes of 1, 2 and 3 mm diameter with simulated pressure drops from 1.01 to 61 bar is investigated and the experimental results are presented. The laminar and turbulent friction factor f at different pressure drop values, the transition from the laminar to turbulent flow, the effect of relative roughness, and the boundary-layer thickness, δ, are computed and studied. The experimental results are presented, discussed and analysed, according to the theoretical principles.

Numerical investigation of the effect of water/Al2O3 nanofluid on heat transfer in trapezoidal, sinusoidal and stepped microchannels

2019 ◽  
Vol 30 (5) ◽  
pp. 2439-2465 ◽  
Author(s):  
Vahid Jaferian ◽  
Davood Toghraie ◽  
Farzad Pourfattah ◽  
Omid Ali Akbari ◽  
Pouyan Talebizadehsardari
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cross Section ◽  
Cross Sections ◽  
Volume Fraction ◽  
Pure Water ◽  
Circular Cross Section ◽  
Reynolds Numbers ◽  
Two Phase ◽  
Content Type

Purpose The purpose of this study is three-dimensional flow and heat transfer investigation of water/Al2O3 nanofluid inside a microchannel with different cross-sections in two-phase mode. Design/methodology/approach The effect of microchannel walls geometry (trapezoidal, sinusoidal and stepped microchannels) on flow characteristics and also changing circular cross section to trapezoidal cross section in laminar flow at Reynolds numbers of 50, 100, 300 and 600 were investigated. In this study, two-phase water/Al2O3 nanofluid is simulated by the mixture model, and the effect of volume fraction of nanoparticles on performance evaluation criterion (PEC) is studied. The accuracy of obtained results was compared with the experimental and numerical results of other similar papers. Findings Results show that in flow at lower Reynolds numbers, sinusoidal walls create a pressure drop in pure water flow which improves heat transfer to obtain PEC < 1. However, in sinusoidal and stepped microchannel with higher Reynolds numbers, PEC > 1. Results showed that the stepped microchannel had higher pressure drop, better thermal performance and higher PEC than other microchannels. Originality/value Review of previous studies showed that existing papers have not compared and investigated nanofluid in a two-phase mode in inhomogeneous circular, stepped and sinusoidal cross and trapezoidal cross-sections by considering the effect of changing channel shape, which is the aim of the present paper.

Study of Buoyancy Effects on Supercritical CO2 Heat Transfer in Circular Pipes

2020 ◽  
Author(s):  
Akshay Khadse ◽  
Ladislav Vesely ◽  
James Sherwood ◽  
Andres Curbelo ◽  
Vipul Goyal ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Cross Sections ◽  
Supercritical Co2 ◽  
High Pressures ◽  
Cooling System ◽  
Reduction Process ◽  
Density Variation ◽  
Working Fluid ◽  
Power Cycle

Abstract Supercritical CO2 (sCO2) can be utilized as a working fluid in various systems including high scale power cycle, portable power production unit, centralized cooling system and standalone cooling device. Lack of accurate predication tools such as heat transfer coefficient correlations and insufficient knowledge behind fundamental heat transfer processes can hinder its practical realization in key energy and cooling systems. The overall objective of the proposed study is to extend fundamental knowledge about heat transfer and fluid flow processes in conduits pertinent to sCO2 power cycle with an emphasis on buoyancy effects. Operational requirement of high pressures and temperatures for intended applications put a significant amount of constraints on measurement strategy and instrumentation. For this paper, experiments were conducted with uniform volumetric heat generation within pipe wall, for a single Reynolds number of 16,600 at test section inlet. The designed test apparatus and data reduction process are validated with high pressure air experiments, complemented by companion computations. Nusselt number was found to be within 10% of conventional correlations. For the test parameters and pipe size selected, factors of 2 to 4 variations in circumferential Nusselt number distributions are observed in sCO2 flow. Richardson number and other similar parameters to indicate importance of buoyancy-driven flow phenomena suggest that buoyancy forces caused by large density variation of sCO2 in flow cross-sections may cause the observed circumferential variations in Nusselt number.

An Investigation of Flat-Plate Oscillating Heat Pipes

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Peng Cheng ◽  
Scott Thompson ◽  
Joe Boswell ◽  
H. B. Ma
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Flat Plate ◽  
Cross Sections ◽  
Heat Transfer Performance ◽  
Heat Pipes ◽  
Power Input ◽  
Copper Plate ◽  
Working Fluid ◽  
Transfer Performance

The heat transfer performance of flat-plate oscillating heat pipes (FP-OHPs) was investigated experimentally and theoretically. Two layers of channels were created by machining grooves on both sides of a copper plate in order to increase the channel number per unit volume. The channels had rectangular cross-sections with hydraulic diameters ranging from 0.762 mm to 1.389 mm. Acetone, water, diamond/acetone, gold/water, and diamond/water nanofluids were tested as working fluids. It was found that the FP-OHP’s thermal resistance depended on the power input and operating temperature. The FP-OHP charged with 0.0003 vol % gold/water nanofluids achieved a thermal resistance of 0.078 K/W while removing 560 W with a heat flux of 86.8 W/cm2. The thermal resistance was further decreased when the nanofluid was used as the working fluid. A mathematical model predicting the heat transfer performance was developed to predict the thermal performance of the FP-OHP. Results presented here will assist in the optimization of the FP-OHP and provide a better understanding of heat transfer mechanisms occurring in OHPs.

scholarly journals Thermohydraulic Performance of a Series of In-Line Noncircular Ducts in a Parallel Plate Channel

2014 ◽  
Vol 2014 ◽  
pp. 1-10
Author(s):  
Siddharth D. Mhaske ◽  
Soby P. Sunny ◽  
Sachin L. Borse ◽  
Yash B. Parikh
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Parallel Plate ◽  
Circular Cross Section ◽  
Flow Characteristics ◽  
Ansys Fluent ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Plate Channel

Heat transfer and fluid flow characteristics for two-dimensional laminar flow at low Reynolds number for five in-line ducts of various nonconventional cross-sections in a parallel plate channel are studied in this paper. The governing equations were solved using finite-volume method. Commercial CFD software, ANSYS Fluent 14.5, was used to solve this problem. A total of three different nonconventional, noncircular cross-section ducts and their characteristics are compared with those of circular cross-section ducts. Shape-2 ducts offered minimum flow resistance and maximum heat transfer rate most of the time. Shape-3 ducts at Re < 100 and Shape-2 ducts at Re > 100 can be considered to give out the optimum results.

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