Pumping power and heat transfer rate of converging microchannel heat sinks: errors associated with the temperature dependency of nanofluids

2019 ◽  
Vol 140 (3) ◽  
pp. 1267-1275 ◽  
Author(s):  
M. Dehghan ◽  
H. Vajedi ◽  
M. Daneshipour ◽  
A. Pourrajabian ◽  
S. Rahgozar ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Sinks ◽  
Temperature Dependency ◽  
Pumping Power ◽  
Microchannel Heat Sinks

Analytic Optimization of Porous Medium Heat Sinks for Energy Efficiency and Minimum Mass

2013 ◽  
Author(s):  
Ninad Trifale ◽  
Eric Nauman ◽  
Kazuaki Yazawa
Keyword(s):  
Heat Transfer ◽  
Energy Efficiency ◽  
Porous Medium ◽  
Heat Transfer Rate ◽  
Heat Sink ◽  
Transfer Rate ◽  
Heat Sinks ◽  
High Heat Flux ◽  
Minimum Mass ◽  
Pumping Power

Use of microchannel heat sinks for high heat flux applications is substantial for thermal management and it is also critical for scalable power generation. For both applications, the energy efficiency consideration of the pump power is crucial. A number of models have been created that predict the performance as a function of the geometrical parameters, taking into account, the pressure loss over the length and volume constraints. Most of the approaches either involve sophisticated calculations incorporating fluid dynamics in channels, or have an analogy with the pin-fin model, which gives simpler calculations but considers only a single laminar flow regime for optimization. Even with the simplified models available, the geometrical impact on mass and pumping power is nonlinear and not apparent for optimization. We propose an optimization of porous medium heat sinks with respect to the heat transfer rate, mass, and pumping power. These are functions of the simplest geometric parameters, i.e. porosity, pore density, and length of the porous medium. Considering large production, mass (cost of raw material) is nearly proportional to the cost of the heat sink, we consider minimizing the mass for indirectly minimizing the overall cost. The other factor for saving energy considered here is the pumping power. This connects to both the heat transfer rate and the power consumption to drive the fluid through the porous medium. The optimization is performed for a specific value of porosity and length of the heat sink. The model considers the effect of flow through the porous medium and the effective thermal conduction as a function of combined conductivity of the solid ligaments and the fluid in pores. An optimum coefficient of performance (COP) is found at over 90% of porosity for minimum mass, pumping work and maximum heat transfer. This mathematical expression of the model will give a quantifiable figure-of-merit to take into account the impact of the mass and the pumping power on the performance to cost ratio.

An analytical approach for optimal design of heat sinks under forced convection

2013 ◽  
Vol 3 (2) ◽  
Author(s):  
Antonio Miguel
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Transfer Rate ◽  
Analytical Approach ◽  
Constant Heat Flux ◽  
Heat Sinks ◽  
Pumping Power ◽  
Fluid Stream ◽  
Design Standards ◽  
Constant Heat

AbstractSaving energy is just as important as generating energy. In this paper, we seek an optimized structure that achieves a certain level of heat transfer rate under a minimum pumping power to drive the fluid stream. Constraints are specified by the flow regime (laminar and turbulent), admissible boundary conditions on the walls (prescribed temperature and constant heat flux), and design standards. The study will help designers with more effective basic tools for the conceptual design of system and in establishing proper operating procedures.

Convective Heat Transfer and Pumping Power Requirement Using Nanofluid for the Flow Through Corrugated Channel

2015 ◽  
Author(s):  
Shafi Noor ◽  
M. Monjurul Ehsan ◽  
M. S. Mayeed ◽  
A. K. M. Sadrul Islam
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Pumping Power ◽  
Power Requirement ◽  
Corrugated Channel ◽  
Flow Through

Convective heat transfer rate for turbulent flow using nanofluid through both plain and corrugated channel has been investigated numerically in the present study. Three different types of nanofluids namely Al2O3-water, TiO2-water and CuO-water of different volume fractions (1%, 2%, 3%, 4% and 5%), are used as the working fluid flowing through the channel. The corrugated channels have wall geometries of trapezoidal shape of different amplitude-wavelength ratios. Grid independence study was carried out for all the geometries. The obtained results in case of base fluid-water flowing through parallel plate channel have been validated with well-established correlations. The study has been conducted by finite volume method to solve the transport equation for the momentum, energy and turbulence quantities using single phase model of the nanofluids where the thermophysical properties of the nanofluids are calculated by using different correlations from the literature. In this study, the heat transfer enhancement using nanofluids compared to that using base fluid-water is presented for a range of Reynolds number- 15000 to 40000. The pumping power required for the flow through the channels increases with the increase in the viscosity of the fluid which justifies the increase in pumping power requirement in case of nanofluids compared to that with water. While using corrugation at the wall of the channels, in addition to the enhancement in the convective heat transfer rate, there is an increase in the pumping power requirement for the same Reynolds number. However, for a given requirement of heat transfer rate, the required pumping power can be reduced by using nanofluids. This study includes the trend and limit of volume fraction of nanofluid during this pumping power reduction phenomenon. The results show that with the increase in the volume fraction of the nanofluids, the convective heat transfer rate increases which is same for all the geometries of the fluid domain. Addition of nanofluid reduces the pumping power requirement for a constant heat transfer rate. The volume fraction of the nanofluids with which the maximum reduction of pumping power takes place at the optimum working condition is also found in the present study. This study draws a comparison among three different nanofluids in terms of the enhancement in the convective heat transfer rate and corresponding pumping power requirement for the flow through the trapezoidal shaped corrugated channel of various amplitude-wavelength ratios in order to find out the best nanofluids for its optimum results within a specified range of working conditions.

Numerical Simulation of Heat Sink Performance With Interrupted and Staggered Fins

2009 ◽  
Author(s):  
Suabsakul Gururatana ◽  
Xianchang Li
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Heat Transfer Rate ◽  
Heat Sink ◽  
Pressure Loss ◽  
Transfer Rate ◽  
Flow Direction ◽  
Heat Sinks ◽  
High Heat Transfer

Extended surfaces (fins) have been used to enhance heat transfer in many applications. In electronics cooling, fin-based heat sinks are commonly designed so that coolants (gas or liquid) are forced to pass through the narrow straight channel. To improve the overall heat sink performance, this study investigated numerically the details of heat sinks with interrupted and staggered fins cooled by forced convection. Long and narrow flow passages or channels are widely seen in heat sinks. Based on the fundamental theory of heat transfer, however, a new boundary layer can be created periodically with interrupted fins, and the entrance region can produce a very high heat transfer coefficient. The staggered fins can take advantage of the lower temperature flow from the upstream. The tradeoff is the higher pressure loss. A major challenge for heat sink design is to reduce the pressure loss while keeping the heat transfer rate high. The effect of fin shapes on the heat sink performance was also examined. Two different shapes under study are rectangular and elliptic with various gaps between the interrupted fins in the flow direction. In addition, studies were also conducted on the parametric effects of Reynolds number and gap length. It is observed that heat transfer increases with the Reynolds number due to the feature of developing boundary layer. If the same pressure drop is considered, the heat transfer rate of elliptic fins is higher than that of rectangular fins.

Buoyancy-Induced Convection in Metal Foam and Finned Metal Foam Heat Sinks©

2000 ◽  
Author(s):  
A. Bhattacharya ◽  
Roop L. Mahajan
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Metal Foam ◽  
Metal Foams ◽  
Experimental Results ◽  
Heat Sinks ◽  
Normal Metal ◽  
Optimum Number

Abstract In this paper, we present our recent experimental results on buoyancy induced convection in metal foams of different pore densities (corresponding to 5, 10, 20 and 40 pores per inch) and porosities (0.89–0.96). The results show that compared to a hot surface facing up, the heat transfer coefficients in these heat sinks are 5 to 6 times higher. However, when compared to commercially available heat sinks of similar dimensions, the enhancement is found to be marginal. The experimental results also show that for a given pore size, the heat transfer rate increases with porosity suggesting the dominant role played by conduction in enhancing heat transfer. On the other hand, if the porosity is held constant, the heat transfer rate is found to be lower at higher pore densities. This can be attributed to the higher permeability with the larger pores, which allows higher entrainment of air through the porous medium. An empirical correlation, developed for the estimation of Nusselt number in terms of Rayleigh and Darcy numbers, is found to be in good agreement with the experimental data with a maximum error of 10%. We also report our results on novel finned metal foam heat sinks© in natural convection. Experiments were conducted on aluminum foams of 90% porosity with 5 and 20 PPI (pores per inch) with one, two, and four aluminum fins inserted in the foam. All these heat sinks were fabricated in-house. The results show that the finned metal foam heat sinks© are superior in thermal performance compared to the normal metal foam and conventional finned heat sinks. The heat transfer increases with increase in the number of fins. However, the relative enhancement is found to decrease with each additional fin. The indication is that there exists an optimum number of fins beyond which the enhancement in heat transfer due to increased surface area is offset by the retarding effect of overlapping thermal boundary layers. Similar to normal metal foams, the 5 PPI samples are found to give higher values of the heat transfer coefficient compared to the 20 PPI samples due to higher permeability of the porous medium. Future work is planned to arrive at the optimal heat sink configuration for even larger enhancement in heat transfer.

Enhancement and Prediction of Heat Transfer Rate in Turbulent Flow Through Tube With Perforated Twisted Tape Inserts: A New Correlation

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
J. U. Ahamed ◽  
M. A. Wazed ◽  
S. Ahmed ◽  
Y. Nukman ◽  
T. M. Y. S. Tuan Ya ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Circular Tube ◽  
Twisted Tape ◽  
Pumping Power ◽  
Plain Tube ◽  
Flow Through

An experimental investigation has been carried out for turbulent flow in a tube with perforated twisted tape inserts. The mild steel twisted tape inserts with circular holes of different diameters (i.e., perforation) are used in the flow field. An intensive laboratory study is conducted for heat transfer and pressure drop characteristics in the tubes for turbulent flow with various airflow rates. Heat transfer and pressure drop data are engendered for a wide range Reynolds number (1.3×104–5.2×104). Tube wall temperature, pressure drop, air velocity, and its temperature are measured both for plain tube and for tube with perforated twisted tape inserts. Heat transfer coefficients, Nusselt number, pumping power, and heat transfer effectiveness are calculated for both cases. Experimental results showed that perforated twisted inserts of different geometry in a circular tube enhanced the heat transfer rate with an increase in friction factor and pumping power for turbulent flow. The pumping power, heat transfer coefficient, and effectiveness in the tube with the twisted tape inserts are found to increase up to 1.8, 5.5, and 4.0 times of those for the plain tube for same Reynolds number, respectively. Finally, a correlation is developed for prediction of the heat transfer rate for turbulent flow through a circular tube with perforated twisted tape inserts.

Constructal heat transfer rate maximization for cylindrical pin-fin heat sinks

2016 ◽  
Vol 108 ◽  
pp. 427-435 ◽  
Author(s):  
Aibo Yang ◽  
Lingen Chen ◽  
Zhihui Xie ◽  
Huijun Feng ◽  
Fengrui Sun
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Sinks ◽  
Pin Fin ◽  
Rate Maximization

scholarly journals A REVIEW ON HEAT TRANSFER FROM DIFFERENT SHAPED FINS

2016 ◽  
Vol 2 (2) ◽  
Author(s):  
Abhinandan Jain ◽  
P K Upadhyay ◽  
Jitendra Singh Chouhan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Heat Sink ◽  
Transfer Rate ◽  
Cost Effective ◽  
Industrial Applications ◽  
Heat Sinks ◽  
Manufacturing Cost ◽  
Automotive Components ◽  
Reliable Solution

Heat sinks with fins are generally used to enhance the heat transfer rate in many industrial applications such as cooling of electronic, power electronic, telecommunication and automotive components. In many situations where heat transfer is by natural convection fins offer economical and trouble free solutions. The weight and volume of the equipment are the most important parameters of design. Now days the general trend is to use compact systems especially in electronic field which leads to higher packing density of systems causing higher heat generation. It affects the performance of system and may cause the system failure. The most preferred method for cooling electronic and telecommunications devices is passive cooling since it is cost effective and reliable solution. It doesn’t require costly enhancing devices. This features leads to focus on development of efficient fin heat sink. The important element that defines the geometry of the heat sink is its fins. The fins generally used in industry are straight, circular and pin shaped. The objective of this work is review on the heat transfer rate by different shaped fins in different systems. The proper selection of the interruption length increases the heat transfer rate and in addition providing fin interruptions results in considerable weight reduction that can lead to lower manufacturing cost.

Optimal Ratio of Heat Removal Rate to Pumping Power for PCM Emulsion Fluids: Low Reynolds Number Limits

2006 ◽  
Author(s):  
P. Maloji ◽  
Y.-X. Tao
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Phase Change ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Removal Rate ◽  
Pure Water ◽  
Heat Removal ◽  
Pumping Power ◽  
Optimal Ratio

There are many applications where high heat transfer removal rate in a limited tight space are required. The applications include mini and micro-scale channels flows in compact heat exchangers. The increase in heat transfer rate often requires the significant increase in fluid velocity and therefore the increase in the pumping power. One option is to utilize Phase Change Materials (PCM). This study contributes to the further understanding of performance enhancement of an improved heat transfer fluid by studying the optimal ratio of heat removal rate to the fluid pumping power. PCMs have the unique characteristics that can increase the thermal capacity of heat transfer fluids by providing latent heat capacity at a temperature different than the melting point of the carrier fluid. The ratio of heat transfer rate (Q) to fluid pumping power (P) is about twice as that for using pure water without PCM particles. The effectiveness factor (compared to water without PCM) is also doubled. It has been observed that as Re decreases the effective factor increases and Q/P ratio increases, which is also true if the concentration of PCM increases. In this experimental study focuses are on the heat transfer enhancement effects for very low Reynolds number (Re < 180 of pure water velocity) and PCM concentration slurry flow of 10% to 20%. Experimental investigations relevant to PCM slurry flows are carried out. Experimental results indicate that PCM slurry's heat transfer coefficient and apparent specific heat are affected significantly by the phase change process and the slurry mass fraction. It is found that the Q/P ratio primarily is a function of Reynolds number.

scholarly journals Computational Investigation of Micro-channel Heat Sink with Rectangular Shape Obstacles

2021 ◽  
Vol 2070 (1) ◽  
pp. 012181
Author(s):  
P M Wadekar ◽  
A B Shinde ◽  
V B Patil ◽  
P D. Kulkarni ◽  
P V Kengar ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Heat Sink ◽  
Transfer Rate ◽  
Heat Sinks ◽  
Micro Channel ◽  
Rectangular Shape ◽  
Numerical Result ◽  
Geometrical Features ◽  
Modeling Software

Abstract Nowadays a lot of interest is given to the geometrical modification of heat sink systems to cool down the electronic components. To improve the performance index of the heat sinks, the use of geometrical features with different shapes and at different locations on the surface can be a valuable approach. In this paper, the effect of rectangular shape obstacles on the micro channel heat sink (MCHS) performance is studied. Due to surface features, vortex is developed which helps to increase the heat transfer rate. Numerical modeling software Comsol Multiphysics with heat transfer in fluid physics is used to investigate the characteristics of a micro-channel heat sink. The numerical result shows that the heat transfer rate can be improved through an appropriate arrangement of rectangular shape obstacles, on the heat sink. Numerical analysis and the comparison is carried out for micro-channel heat sink with and without obstacles. In this paper, various parameters like temperature rise, cell Peclet number and Mean effective thermal conductivity are studied.

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