Showing papers on "Micro heat exchanger published in 2018"
TL;DR: In this article, an effort has been made to categorize the active and passive methods and review the various heat transfer techniques applied in heat exchangers, and a combined method have also been recommended which include both active and active methods.
Abstract: The objective of this paper is to review the different techniques, which have been used to enhance the heat transfer rate in heat exchanger devices such as solar air heater, cooling blades of turbine and so on using single phase heat transfer fluids. The results of recent published articles with the development of new technologies such as Electrohydrodynamic (EHD) and Magnetohydrodynamics (MHD) are also included. Enhancement of heat transfer in heat exchanger can achieved by means of several techniques. These techniques are grouped into the active and passive method. In the active methods, system need some external power, however, passive method utilize surface modification either on heated surface or insertion of swirl devices in the flow field. Active methods are very complex because of external power supply, although these methods have great potential and can control thermally. Passive methods include artificial roughness, extended surface, winglets, insertion of swirl devices in the flow which alters the flow pattern causes to disturb the thermal boundary layer, and consequently high heat transfer. Passive methods are dominant over active methods because its can easily employed in existing heat exchangers. In this paper, an effort has been made to categorize the active and passive methods and review the various heat transfer techniques applied in heat exchangers. Important results have been listed for ready reference. It has been concluded that either active or passive methods have been employed alone. Based on literature, a combined method have also been recommended which include both active and passive methods.
220 citations
TL;DR: In this paper, the effects of nanoparticles volume fraction, flow direction and Reynolds number on base fluid, nanofluid and wall temperatures, thermal efficiency, Nusselt number and convection heat transfer coefficient have been studied.
209 citations
TL;DR: In this article, a hierarchical manifold micro-channel heat sink array is used to reduce the parasitic thermal resistances due to contact and conduction resistances, which can reduce the chip footprint area and shorten effective fluid flow lengths.
205 citations
TL;DR: In this paper, a parametric analysis for the round pin-finned heat sinks subjected to steady heat densities for effective and reliable cooling of mobile electronic devices is presented, where phase change material (PCM) namely paraffin wax is adopted as energy storage material and aluminum made round pinfins are selected as thermal conductivity enhancers (TCEs).
164 citations
TL;DR: In this article, the laminar heat transfer of kerosene nanofluid/multi-walled carbon nanotubes in the micro-channel heat sink is studied, and the results reveal that applying oscillating heat flux significantly influences the profile figure of Nusselt number and this impressionability is obvious in Reynolds numbers of 10 and 100.
Abstract: In this investigation, the laminar heat transfer of kerosene nanofluid/multi-walled carbon nanotubes in the microchannel heat sink is studied. The considered microchannel is two layers in which the length of bottom layer is truncated and is equal to the half of the length of bottom layer. The length of microchannel bottom layer is L = 3 mm, and the length of top layer is L
1 = 1.5 mm. The microchannel is made of silicon, and each layer of microchannel has the thickness of t = 12.5 µm. Along the external bottom wall, the sinusoidal oscillating heat flux is applied. The top external and lateral walls are insulated, and they do not have heat transfer with the environment. The results of this research revealed that in different Reynolds numbers, applying oscillating heat flux significantly influences the profile figure of Nusselt number and this impressionability is obvious in Reynolds numbers of 10 and 100. Also, by increasing the slip velocity coefficient on the solid surfaces, the amount of minimum temperature reduces significantly which behavior remarkably entails the heat transfer enhancement.
119 citations
TL;DR: In this article, the authors summarized the research outcomes of various experimental and numerical studies, and provided an overview of heat transfer mechanisms responsible for the change in thermal performance of heat pipes.
107 citations
TL;DR: In this article, the effect of functionalized multi walled carbon nanotubes on heat transfer and pressure drop of ethylene glycol-water flow in a tube was investigated.
99 citations
Abstract: Inserts are used to enhance the heat transfer rates between the two fluids in heat exchanger tubes. A variety of tube inserts such as twisted tape, wire coil, swirl flow generator have been investigated for their effect on heat transfer rates and fluid friction. This paper reviews the works pertaining to the application of different class of tube inserts in order to comprehend the prevailing mechanism of fluid flow and heat transfer. An attempt has been made to elucidate the fluid flow behaviour sustained by the particular class of insert that controls the heat transfer rates across the thermal boundary layer attached to the tube wall.
95 citations
TL;DR: In this article, a manifold-micro-channel heat exchanger is proposed for dry cooling of power plants, which consists of manifold microchannels on the air side and rectangular channels on the water side in a cross-flow configuration.
90 citations
TL;DR: In this article, the combination effects of structure parameters (diameter of pin-fin D1, depth of dimple δ and stream-wise spacing S) on flow structure and heat transfer were investigated in detail.
76 citations
TL;DR: An additively manufactured manifold-micro-channel heat exchanger made of Inconel 718 and experimentally tested for high temperature aerospace applications was presented in this paper, where a minimum fin thickness of 180μm was achieved.
TL;DR: In this paper, the second law attributes including entropy generation, exergy destruction and second law efficiency for flow a novel nanofluid containing graphene nanoplatelets decorated with silver nanoparticles are investigated in a micro double-pipe heat exchanger.
TL;DR: In this article, the authors investigated the performance of corrugated/perforated fins (CPFs) for use in plate heat exchangers as heat exchange devise in the active solar heating system.
TL;DR: In this paper, the effect of jet-plate spacing to jet diameter ratios on the jet impingement heat transfer and pressure drop of TiO2 nanofluids have been presented.
TL;DR: In this paper, the evaporation heat transfer coefficient and pressure drop of R-1233zd(E) in a brazed plate heat exchanger are measured with respect to the mass flux, heat flux, saturation temperature, and vapor quality.
TL;DR: In this article, a two-dimensional continuum flow model is proposed for heat transfer in compressible laminar flow in mini-/micro-channels, where analytical solutions of the dimensionless model are achieved in closed-form symbolic algebras of Whittaker eigenfunctions.
TL;DR: In this article, the effect of carbon nanotubes (CNTs) on thermal transfer in a planar microchannel with multiple slip effects was investigated, and the results showed that the effects of CNTs in microchannel flow by utilizing viscous dissipation and Joule heating were first investigated.
Abstract: Purpose
The microfluidics has a wide range of applications, such as micro heat exchanger, micropumps, micromixers, cooling systems for microelectronic devices, fuel cells and microturbines. However, the enhancement of thermal energy is one of the challenges in these applications. Therefore, the purpose of this paper is to enhance heat transfer in a microchannel flow by utilizing carbon nanotubes (CNTs). MHD Brinkman-Forchheimer flow in a planar microchannel with multiple slips is considered. Aspects of viscous and Joule heating are also deployed. The consequences are presented in two different carbon nanofluids.
Design/methodology/approach
The governing equations are modeled with the help of conservation equations of flow and energy under the steady-state situation. The governing equations are non-dimensionalized through dimensionless variables. The dimensionless expressions are treated via Runge-Kutta-Fehlberg-based shooting scheme. Pertinent results of velocity, skin friction coefficient, temperature and Nusselt number for assorted values of physical parameters are comprehensively discussed. Also, a closed-form solution is obtained for momentum equation for a particular case. Numerical results agree perfectly with the analytical results.
Findings
It is established that multiple slip effect is favorable for velocity and temperature fields. The velocity field of multi-walled carbon nanotubes (MWCNTs) nanofluid is lower than single-walled carbon nanotubes (SWCNTs)-nanofluid, while thermal field, Nusselt number and drag force are higher in the case of MWCNT-nanofluid than SWCNT-nanofluid. The impact of nanotubes (SWCNTs and MWCNTs) is constructive for thermal boundary layer growth.
Practical implications
This study may provide useful information to improve the thermal management of microelectromechanical systems.
Originality/value
The effects of CNTs in microchannel flow by utilizing viscous dissipation and Joule heating are first time investigated. The results for SWCNTs and MWCNTs have been compared.
TL;DR: In this article, the authors compared the thermal performance of two types of ground-air heat exchangers (GAHEs) with a two-level arrangement and an innovative plate exchanger, in which the air is in direct contact with the ground.
TL;DR: In this article, the authors reviewed various studies, in which different obstacle roughness elements are used to enhance the rate of heat transfer in the heat exchanger tubes, including twisted tapes, wire coil ribs, baffles, and swirl flow generators.
Abstract: Heat exchangers are widely used in almost all industrial activities. Turbulent promoters used in heat exchanger tubes are an effective way of enhancing the performance. This paper summarises various investigations using twisted tapes, wire coil ribs, baffles, and swirl flow generators. The main objective of this paper is to review various studies, in which different obstacle roughness elements are used to enhance the rate of heat transfer in the heat exchanger tubes. It has been found that a lot of experimental and analytical studies reported in the literature. On the basis of correlations developed by various investigators an attempt has been made to compare the thermal hydraulic performance of obstacles in heat exchanger tubes. In this work, a comparative study is also carried out to select the best obstacle roughness shapes for higher heat transfer rate and low pressure drop losses.
TL;DR: In this paper, the effect of surface roughness on the heat transfer coefficient and pressure drop in a chevron gasketed plate heat exchanger was studied. But the authors focused on the effect on the surface roughs and did not consider the effect in the condensation heat transfer of R-134a.
TL;DR: In this paper, the effect of microchannel height, width and spacing on fluid flow and heat transfer performance is comprehensively studied, and the results show that the increasing height and width have an appreciable contribution to the velocity profile.
TL;DR: In this paper, a series of experimental tests were carried out in a commercial 300MW CFB boiler with fluidized bed heat exchangers (FBHEs), and the test results indicated that there is a good linear correspondence between the FBHEs conical valve openings and circulating ash flow rate.
TL;DR: In this paper, the authors investigated the effects of various parameters, such as the height and density (number) of transverse microchannels and Reynolds numbers, on the pressure drop, temperature distribution and heat transfer rate inside the heat sink.
TL;DR: In this article, a comparison between different forms of obstacles (rectangular, triangular and circular), inserted in the geometry of the proposed membrane-based heat exchanger, is presented, in order to evaluate their impacts on the heat and mass transfer distributions, a numerical model including the momentum, heat, and mass transport equations is solved.
TL;DR: In this article, a standalone absorption chiller based on microchannel heat exchanger technology was developed with a cooling capacity of 7kW, and a control system for standalone operation was developed.
Abstract: A standalone absorption chiller based on microchannel heat exchanger technology was developed with a cooling capacity of 7 kW. A review of recent advances in microscale heat and mass exchangers and vapor absorption technology guided this development. Thermodynamic and heat and mass transfer design procedures are discussed. A control system for standalone operation was developed. Experimental evaluation demonstrated the achievement of target cooling capacities. An overall system COP of 0.44, and an ammonia–water cycle COP of 0.51 were achieved. Reasons for differences between model predictions and actual performance are discussed. This development validates scalability and application of microscale heat exchanger technology for absorption heat pumps at residential-scale capacities. In contrast to conventional absorption systems, core heat and mass exchangers require only small portion of overall system volume and weight, which significantly improves the prospects of this technology for small capacity applications.
TL;DR: In this paper, an experimental study performed to compare the results of different methods used in the literature for the calculation of heat transfer coefficient in double-tube heat exchangers is presented.
Abstract: An experimental study performed to compare the results of different methods used in the literature for the calculation of heat transfer coefficient in double-tube heat exchangers. Then, a new funda...
TL;DR: A plate microchannel heat exchanger (MHX) with isosceles trapezoid-shaped reentrant cavities (ITRCs) in the sidewalls was designed in this paper.
Abstract: A plate microchannel heat exchanger (MHX) with isosceles trapezoid-shaped reentrant cavities (ITRCs) in the sidewalls was designed. The flow, heat transfer, and pressure drop characteristics of the MHX were analyzed numerically based on the commercial software FLUENT and compared with a traditional rectangular MHX. The influences of the structural parameters of the ITRCs on the heat transfer performance were investigated. The results indicate that the heat transfer capacities of both MHXs increase first and then weaken with the increase in the flow rate. The heat transfer performance is better for the MHX with ITRCs than for the traditional rectangular MHX and the advantage of the former is more apparent at an increased flow rate. At flow rates greater than 130 ml/min, the pressure drop is lower for the MHX with ITRCs than for the traditional rectangular MHX. The best heat transfer performance is observed at the optimum value of the number or the height of the ITRCs. The heat transfer performance decreases with the increase in the coincidence degree of the ITRCs. The heat transfer performance of the from-dense-to-sparse (FDTS) ITRC distribution exhibits advantages at flow rates lower than 60 ml/min, whereas the performance of the from-sparse-to-dense (FSTD) ITRC distribution is better at greater flow rates.
TL;DR: In this article, a directexpansion solar-assisted heat pump hot water system using variable frequency control was studied experimentally, and the system mainly consisted of a frequency conversion compressor, a condenser using microchannel heat exchanger, a bare plate solar collector/evaporator, and an electronic expansion valve as the throttling device.