MICROCHANNEL HEAT EXCHANGERS – PRESENT AND PERSPECTIVES (original) (raw)
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Heat Transfer Analysis in Microchannel Heat Exchanger: A Review
A systematic review on the heat transfer in microchannel heat exchangers with different geometries is presented. The slip and No-slip flow are accounted in this study. The two dimensional, three dimensional studies considered with single phase convective heat transfer microchannel with different geometries. Both theoretical and experimental studies are considered and comparison made between them. From the available experimental literature friction factor, Nusselt number is measured and they compared with the conventional theory and results shows that inequality between experiment and conventional theory results. The compressibility effect, roughness effect, viscous dissipation effect, variation in properties is also considered for find out the pressure drop. The results show that the pressure drop is the function of roughness. By paralleling the experimental data on single-phase convective heat transfer through microchannels, it is manifest that additional methodical studies are ess...
International Journal of Energy for a Clean Environment, 2019
Microscale heat exchangers are becoming an important area of interest in many fi elds of developing technology that require compact high heat energy removal solutions. In our work, numerical and experimental analyses are carried out for rectangular microchannels with fi ve sets of rectangular confi gurations, in order to fi nd optimum confi guration of a microchannel. Analysis of a rectangular microchannel is carried out for the forced convection heat transfer condition with a constant base area of 30-mm length and 20-mm width. An experimental setup has been developed to test the microchannel with diff erential pressure transducers, J-type thermocouples, and a digital magnetic rotameter with microchannel manifold. A theoretical analysis was carried out with a C program code to fi nd out the optimum theoretical dimension of the microchannel at various fl ow rates from 0.0016 kg/s to 0.1 kg/s. Experiments were carried out with heat inputs of 25 W to 150 W and fl ow inputs of 0.0016 kg/s to 0.1 kg/s. It was found that the heat transfer coeffi cient for a hydraulic diameter of 260 μm is equal to 12,000 W/m 2 •K. As compared to other confi gurations, the heat transfer coeffi cient is higher, so that the 260-μm diameter microchannel is more optimistic theoretically as compared to other confi gurations of a microchannel. Also, as the heat input increases, the confi guration with a larger hydraulic diameter shows a less pressure drop as compared to a hydraulic diameter of 260 μm. The range of pressure drop for a microchannel is observed at 0.026 kPa. For a hydraulic diameter of 370 μm, the pressure drop is minimum, 0.01 kPa. Experimental results show that for a 30-mm-long microchannel with a hydraulic diameter of 260 μm, the temperature rise for the refrigerant R22 is in a range of 2 o C to 18 o C in the analysis of a single-phase refrigerant. The results for experimental temperature diff erence across the microchannel is 10 to 20% less as compared to theoretical results. The range of applicability allows a comparison of the refrigerant distribution in diff erent designs of microchannel heat exchangers.
Study of Thermal Performance of Counter Flow Microchannel Heat Exchangers
In this paper a full numerical simulation is made to find the velocity and temperature fields for a counter flow microchannel heat exchanger (CFMCHE). Effects of entrance region and axial conduction on thermal performance of a CFMCHE are studied for various conditions. Results show that the well defined ε-NTU relation of conventional counter flow heat exchanger is remained the same but the value of U is the average along the heat exchanger taking into account the effect of entrance region and axial conduction. Analysis show that axial conduction reduced effectiveness of the heat exchanger and there is also an optimal value of wall to fluid thermal conductivity ratio which gives maximum performance of the heat exchanger.
Iaeng International Journal of Applied Mathematics, 2010
The influence of flow arrangement on the heat transfer behaviors was carried out for a microchannel heat exchanger. The results were obtained by both numerical simulations and experimental data. The solver of numerical simulations-COMSOL-was developed by using the finite element method. For all cases done in this study, the heat flux obtained from the counter-flow arrangement is always higher than that obtained from the parallel-flow one: the value obtained from the counter-flow is 1.1 to 1.2 times of that obtained from the parallel-flow. This means that the heat transfer behaviors of the microchanel heat exchanger with counter-flow are better than those with parallel-flow. For the case of the counter-flow, the experimental results indicated that the total heat flux of 17.81 W/cm 2 was achieved for water from the hot side of the device having the inlet temperature of 70 ºC and flow rate of 0.2321 g/s and for water from the cold side having the inlet temperature of 22.5 ºC and flow rate of 0.401 g/s. Besides, the numerically obtained profiles of the temperature and the temperature gradient were shown graphically. Furthermore, the results obtained from the numerical analyses were in good agreement with those obtained from the experiments, with the discrepancies of the heat transfer coefficient estimated to be less than 10 %.
Heat Transfer Analysis of Microchannel using Fluids
2020
In recent time due to high performance of electronic component the heat generation is increasing drastically. Due to this scenario heat dissipation becomes a major issue in efficiency promation and stable operation. Silicon based microchannel heat sink fabricated using semiconductor production technique plays important role in cooling devices. The effect of the thermophysical properties of working fluids on the performance of microchannel is tested or we can say investigated. For this purpose the different working fluids are selected. water, hepthane, ammonia, methanol, and ethanol. KeywordsHeat transfer, Micro channel, different coolents, natural convection, heat transfer, heat sink, , cooling, micro heat sinks. I.INTRODUCTION Now a days the electronic devices become compact. Due to compactness of this devices there is huge heat generation in this devices. Hence for the safety purpose heat should be remove from this devices continuosly.so the purpose of cooling system is to maintai...
A review of liquid flow and heat transfer in microchannels with emphasis to electronic cooling
Sādhanā
Since the realization of microchannel devices more than three and half decades ago with water as the cooling fluid providing heat transfer enhancement, significant progress has been made to improve the cooling performance. Thermal management for electronic devices with their ever-widening user profile remains the major driving force for performance improvement in terms of miniaturisation, long-term reliability, and ease of maintenance. The ever-increasing requirement of meeting higher heat flux density in more compact and powerful electronic systems calls for further innovative solutions. Some recent studies indicate the promise offered by processes with phase change and the use of active devices. But their adoption for electronic cooling still weighs unfavourably against long-term fluid stability and simplicity of device profile with moderate to high heat transfer capability. Applications and reviews of these promising research trends have been briefly visited in this work. The main focus of this review is the flow and heat transfer regime related to electronic cooling in evolving channel forms, whose fabrication are being enabled by the significant advancement in micro-technologies. Use of disruptive wall structures like ribs, cavities, dimples, protrusions, secondary channels and other interrupts along with smooth-walled channels with curved flow passages remain the two chief geometrical innovations envisaged for these applications. These innovations target higher thermal enhancement factor since this implies more heat transfer capability for the same pumping power in comparison with the corresponding straight-axis, smooth-wall channel configuration. The sophistication necessary to deal with the experimental uncertainties associated with the micron-level characteristic length scale of any microchannel device delayed the availability of results that exhibited acceptable matching with numerical investigations. It is indeed encouraging that the experimental results pertaining to simple smooth channels to grooved, ribbed and curved microchannels without unreasonable increase in pumping power have shown good agreement with conventional numerical analyses based on laminar-flow conjugate heat-transfer model with no-slip boundary condition. The flow mechanism with the different disruptive structures like dimple, cavity and rib, fin and interruption, vortex generator, convergingdiverging side walls or curved axis are reviewed to augment the heat transfer. While the disruptions cause heat transfer enhancement by interrupting the boundary layer growth and promoting mixing by the shed vortices or secondary channel flow, the flow curvature brings in enhancement by the formation of secondary rolls culminating into chaotic advection at higher Reynolds number. Besides these revelations, the numerical studies helped in identifying the parameter ranges, promoting a particular enhancement mechanism. Also, the use of modern tools like Poincare section and the analysis of flow bifurcation leading to chaotic advection is discussed. Among the different disruptive structures, sidewall cavity with rib on the bottom wall within the cavity plays a significant role in augmenting the thermal performance. Among the different converging-diverging side walls or curved axis, the sinusoidal channel provides the highest mixing by the introduction of secondary vortices or dean vortices to augment the heat transfer with less pressure drop. The optimum geometry in terms of high heat transfer with low pressure plays a major role in the design of heat sink. Directions of some future research are provided at the end.
IJERT-Heat Transfer Analysis of Microchannel using Fluids
International Journal of Engineering Research and Technology (IJERT), 2020
https://www.ijert.org/heat-transfer-analysis-of-microchannel-using-fluids https://www.ijert.org/research/heat-transfer-analysis-of-microchannel-using-fluids-IJERTV9IS070503.pdf In recent time due to high performance of electronic component the heat generation is increasing drastically. Due to this scenario heat dissipation becomes a major issue in efficiency promation and stable operation. Silicon based microchannel heat sink fabricated using semiconductor production technique plays important role in cooling devices. The effect of the thermophysical properties of working fluids on the performance of microchannel is tested or we can say investigated. For this purpose the different working fluids are selected. water, hepthane, ammonia, methanol, and ethanol.
A review of heat and fluid flow characteristics in microchannel heat sinks
Heat Transfer, 2020
Heat transfer and flow characteristic in microchannel heat sinks (MCHS) are extensively studied in the literature due to high heat transfer rate capability by increased heat transfer surface area relative to the macroscale heat sinks. However, heat transfer and fluid flow characteristics in MCHS differ from conventional ones because of the scaling effects. This review summarizes the studies that are mainly based on heat transfer and fluid flow characteristic in MCHS. There is no consistency among the published results; however, everyone agrees on that there is no new physical phenomenon in microscale that does not exist at macroscale. Only difference between them is that the effect of some physical phenomena such as viscous dissipation, axial heat conduction, entrance effect, rarefaction, and so forth, is negligibly small at macroscale, whereas it is not at microscale. The effect of these physical phenomena on the heat transfer and flow characteristics becomes significant with respe...
A study on the simulation and experiment of a microchannel counter-flow heat exchanger
Applied Thermal Engineering, 2010
Numerical simulations and experimental tests were carried out to study the fluid flow and heat transfer characteristics for a rectangular-shaped microchannel heat exchanger. Moreover, influences of gravity to heat transfer and pressure drop behaviors of the microchannel heat exchanger were presented by variation of the physical inclinations of the microchannel heat exchanger system used for experiments. For experimental results, a heat flux of 17.4 W/cm 2 was achieved for the heat exchanger. Besides, the results obtained for the actual effectiveness and for the effectiveness (the so-called effectiveness-NTU method) were determined. In this study, the pressure drop decreases as the water temperature rises. As the pressure drop increases from 880 to 4400 Pa, the mass flow rate increases from 0.1812 to 0.8540 g/s. In addition, the results obtained from numerical analyses were in good agreement with those obtained from experiments, with discrepancies of the heat transfer coefficient estimated to be less than 9%.