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A Literature Review To Predict Performance Analysis Of Miniature Loop Heat Pipe

A Literature Review To Predict Performance Analysis Of Miniature Loop Heat Pipe

operation may be carried out using physical model. The experimental investigation reveals the concept of miniature heat pipes with noninverted meniscus with relations of main operation characteristic of evaporator. With the experimental test of MLHP with noninverted meniscus , Victar V. Maziuk [1] concluded that own thermal resistance of evaporator with noninverted meniscus is reduce as compare with thermal resistance of evaporators with inverted meniscus and additionally remove heat fluxes with much greater density. Le-lun JIANG [2] elaborate Miniature cylindrical metal powder sintered wick heat pipe is an ideal component with super-high thermal efficiency for high heat flux electronics cooling. The sintering process was optimally designed based on the equation of the heat transfer limit of sintered heat pipe The sintering parameters including with theory analysis through characterization of sintered wick, heat transfer limit of sintered heat pipe, optimization design of sintered wick and experimental steps like preparation, sintering process, sample testing. Result on the sintering temperature, sintering time, sintering atmosphere and sintering position were discussed. Viachaslau V. Doktarau, Victar V. Maziuk [3] focused on the concept of miniature loop heat pipe with noninverted meniscus with new principle and volume correlation for mLHP startup through experimental investigation. It experimental investigation of design and manufacture of mLHP with noninverted meniscus allow using capillary structure with high thermal conductivity, reduced in thermal resistance of evaporators. Also proved to remove heat fluxes with much greater density than mLHP with inverted meniscus. It studied more the concept of volume, porosity, compensation chamber, capillary structure in evaporation zone and vapour line for better
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Improvement on thermal performance of a disk shaped miniature heat pipe with nanofluid

Improvement on thermal performance of a disk shaped miniature heat pipe with nanofluid

Nanofluids have also been used in heat pipes in recent years [8-10], and the thermal enhancements of nano- fluids on heat pipes were shown in these studies. There is no surprise that suspended particles in a fluid can affect the boiling heat transfer phenomenon at the solid- liquid interface. Huang et al. [11] showed that the pool boiling heat transfer of a heated stainless steel horizontal plate was significantly enhanced by adding glass, copper, and stainless steel microparticles into DI water. How- ever, fluids with suspended microparticles may cause some problems such as abrasion and clogging [7]. Thus, they are not suitable for the applications of miniature heat pipes in which the pore size of the porous medium or the hydraulic diameter of the microchannel is of the order of the micrometer.
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Short Term International Study For Teachers As A Form of Experiential Learning: A Case Study of American Educators in Turkey

Short Term International Study For Teachers As A Form of Experiential Learning: A Case Study of American Educators in Turkey

comparable in magnitude to the reciprocal of the hydraulic radius of the total flow channel [17]. Typically, micro heat pipes have convex but cusped cross sections (for example, a polygon), with a hydraulic diameter in range of 10–500 μm [18]. A miniature heat pipe is defined as a heat pipe with a hydraulic diameter in the range of 0.5 to 5 mm [19]. However, the concept of micro and miniature heat pipes are not always properly addressed in the open literature the way mentioned earlier. For example, miniature heat pipes with micro grooves are sometimes improperly referred to as micro heat pipes [15]. Note, beyond the size ranges noted earlier, there are additionally other structural differences between micro and miniature heat pipes. A heat pipe in which both liquid and gas flow through a single noncircular channel is a true micro heat pipe where the liquid is pumped by capillary force, on the edges of channel, from the condensation section to the evaporation section [15]. An array of parallel micro heat pipes are normally mounted on the substrate surface to boost the area and consequently the heat transfer. Miniature heat pipes can be designed based on micro axially grooved structure (1D capillary structure), meshes or cross grooves (2D capillary structure).
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Experimental investigation of grooved heat pipe using nanofluids

Experimental investigation of grooved heat pipe using nanofluids

Muniappan et al [5] developed and tested a trapezoidal axial grooved wick cryogenic heat pipe using nitrogen as a working fluid. They reported that the thermal performance is improved 2.9 times more over solid copper rod at 100K. Liu Yi-Bing [6] developed micro – grooved plate heat pipes with three different shapes like rectangular, trapezoidal and triangular. He inferred that trapezoidal structure of the flat heat pipe shows best heat transfer performance next is rectangular structure followed by rectangular structure. K.N.Shukla [7] presented overview of heat pipes which includes development of loop hat pipes, micro loop heat pipes and micro and miniature heat pipes. The heat pipe mainly acts as a thermal protection system because of its light weight. Wick length enhances capillary fluid flow and working fluid such as nanofluids improve the heat transfer rates of the heat pipe. Hopkins et al. [8] investigated numerically and experimentally on a grooved wick structure flat plate heat pipe.
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Development of cryogenic loop heat pipes: A review and comparative analysis

Development of cryogenic loop heat pipes: A review and comparative analysis

Key factors affecting the supercritical startup performance was analyzed, and conclusions below have been drawn: a higher working fluid charged pressure and an enhanced thermal conductan[r]

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Heat Pipe Inspection System for Thermal Management in Electronic Circuit

Heat Pipe Inspection System for Thermal Management in Electronic Circuit

These two phase modes of heat transfer provide the heat pipe with its high effective thermal conductivity. For example, a 3mm diameter copper rod, 20cm long heated at one end, cooled at the other and insulated in between would have an end to end AT of over 300°C at IOW. A heat pipe of the same dimensions and with the same heated and cooled areas would exhibit an end to end AT under 5 'IC. This equates to a thermal conductivity for the heat pipe of 60 times that of copper. One thing that has to be noted in the heat pipe augmented systems is that the heat pipe itself is a heat transfer device, not a heat dissipation device. The heat pipe must be coupled to other components (such as a heat sink) to accomplish the dissipation function via natural or forced convection. What the heat pipe adds is a high thermal conductivity thermal link permitting the heat sink to be located remote from the heat source. The heat pipe can also increase the effectiveness of the heat sink surface area by distributing the heat load almost isothermally over its entire surface, overcoming the material's low thermal conductivity (compared to heat pipes).
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Economic fluctuations in 2013-14: Review on Indian Economic Conditions

Economic fluctuations in 2013-14: Review on Indian Economic Conditions

In this paper study of heat pipe, copper pipe and stainless steel pipe is done using apparatus. The power is supplied to the all three pipes using suitable electric heater and change of heat is possible with Dimmer stat suitable heat is supplied and Temperatures were taken at certain length from temperature sensor and indicator results shows that the heat transfer is very good in case of the stainless steel heat pipe compare to rest two pipes and also computational analysis carried out in the ansys workbench and cfx module and the result from the experiment is validated from it.
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An Exact Analytical Solution for Convective Heat Transfer in Elliptical Pipes

An Exact Analytical Solution for Convective Heat Transfer in Elliptical Pipes

A cursory inspection of the aforementioned surveys clearly reveals that the bulk of the literature relates to a circular cylinder, followed by that of rectangular cross section. However, the limited body of knowledge relates to the study of flow and heat transfer in the pipe with elliptical cross section. The fully developed laminar H1 and H2 heat transfer problem for elliptical ducts was first investigated by Claiborne [19]. He used Fourier series to solve the energy equation to obtain approximate temperature distribution and also the Nusslet number for various amounts of aspect ratios. Tao [20] by employing the method of complex variables studied the forced convection problems in few basic problems, including flows in equilateral triangular ducts and in elliptical tubes. This method [20] because of using a complex variable to solve the energy equation has some complexities to compute temperature distribution as well as Nusselt number. Cheng [21] studied natural convective heat transfer in a horizontal isothermal elliptical cylinder with temperature-dependent viscosity. This study [21] showed that the total heat transfer rate and the total skin friction of the elliptical cylinder with slender orientation are higher than those of the elliptical cylinder with blunt orientation. Moreover, increasing the viscosity-variation parameter enhances the heat transfer rates. Sakalis et al. [22] numerically studied the laminar fully developed and developing heat transfer in a straight pipe with the elliptical cross section under isothermal boundary condition. They showed that by increasing the aspect ratio of the ellipse, the friction factor is decreased. Their results also showed that in the thermally developing flow, Nusselt Number is increased by decreasing the aspect ratio. Velusamy et al. [23] numerically studied fully developed laminar flow and heat transfer in ducts of the semi-elliptical cross section for isothermal and a uniform
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Study of Heat Pipes in Solar Collectors Using Nano Fluids

Study of Heat Pipes in Solar Collectors Using Nano Fluids

This paper describes about the performance of heat pipes in solar collectors. The solar energy is the most readily accessible source of energy. It does not belong to anybody and is therefore free. It is also most important of the non- conventional sources of energy because it is eco-friendly. Solar energy captured by solar collector and an evacuated solar collector is most efficient and convenient collector among various kind of solar collector. Heat pipes plays important role in all electronic devices and also in solar collectors. Because the prime role of heat pipe is to reduce the over heat of the devices or collectors. Heat pipe heat exchanger is a simple device which is used to transfer the heat from one location to another location using an evaporation-condensation cycle. The day to day applications of heat pipe heat exchanger are water heater, heat engines, air conditioning and much more. The working fluid of heat pipe heat exchanger is NANO FLUIDS. NANO fluids are the solid-liquid suspension created by the combination of small NANO particles with base liquid(water).The commonly used NANO fluids are Alumina(Al2O3),Copper oxide(Cu2O),Titanium oxide(TiO2) and Au/water. The recently discovered NANO fluid is Graphene oxide due to its high thermal conductivity. The NANO fluid plays a vital role in many of the thermal applications like heat exchanger, solar power generation and Automobile industries because of its higher efficiency less, friction less heat loss and more advantages.
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Analysis of Mathematical Models and Influence of Constructions of High Efficient Heat Transfer Devices

Analysis of Mathematical Models and Influence of Constructions of High Efficient Heat Transfer Devices

On the basis of these studies, a drying plant has been created by using a highly efficient heat transfer device, where the highly efficient heat transfer device operates at the expense of solar energy and in which design can be distinguished: simplicity of design, exceptional maneuverability, ease of regulation and the possibility of transferring high heat fluxes over a considerable distance wıth extremely low temperature pressure [1, 2].

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Enhancement of Heat Transfer in Heat Pipes using Silver/Benzene based Nano Coolants

Enhancement of Heat Transfer in Heat Pipes using Silver/Benzene based Nano Coolants

[16] Li, X., Zou, C., Wang, T., & Lei, X. (2015). Rheological behavior of ethylene glycol-based SiC nanofluids. International Journal of Heat and Mass Transfer, 84, 925–930. [17] R.L. Hamilton, O.K. Carosser,(1962). Thermal conductivity of heterogeneous two-component systems. Industrial & Engineering Chemistry Fundamentals, 1(3),187– 191.

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Experimental and Comparison Study of Heat Transfer Characteristics of Wickless Heat Pipes by using Various Heat Inputs

Experimental and Comparison Study of Heat Transfer Characteristics of Wickless Heat Pipes by using Various Heat Inputs

Abstract: A wickless heat pipe is a heat transfer device which combines the principles of both thermal conductivity and phase transition without the usage of wick structure. The heat pipe generally consists of three sections namely evaporator section, adiabatic section and condensation section. An apparatus set up consisting of four heat pipes made up of different materials namely Copper, Aluminium, Brass and Stainless steel along with heater and cooling duct was designed and fabricated. Various working fluids such as Acetone, Toluene, Ethanol and Dichloro methane are used to determine which among the above working fluids can be used efficiently in heat pipes to improve its performance. The heat inputs are varied from 80 W to 460 W to determine the efficient heat input for the heat pipes. Thus the experiment was carried out to study the thermal efficiency of the heat pipes by using different materials, different working fluids and different heat inputs. At the end of the experiments, copper was found to be the material with high thermal conductivity when compared to the other materials. Dichloromethane was found to be one of the most efficient working fluid to be used in heat pipes at the heat input range of 160 W.
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Investigating thermal performance of a partly sintered wick heat pipe filled with different working fluids

Investigating thermal performance of a partly sintered wick heat pipe filled with different working fluids

formance of the heat pipe. Wong et al. [7] also carried out several experiments on wicks sintered by irregular or spherical shaped powders with dierent size distributions. Their results illustrated that ne pores at the wick bottom help to sustain a thin water lm under large heat loads that leads to better thermal performance and consequently makes large heat loads reachable. Liou et al. [8] reported that low wick permeability limited the reduction of evaporation resistance and prompted dry-out. Deng et al. [9] tested some types of powders and their eects on capillary performance. Their results showed that the irregular copper powder is better than the spherical one for the application in LHPs (loop heat pipes). The reason was attributed to the increased perme- ability and better capillary performance. Tsai and Lee [10] compared thermal performances of sintered heat pipes with dierent powder shapes and sizes. They reported that the spherical powder structures achieved twice the eective thermal conductivity of dendritic powder ones for each powder size. Further- more, Li et al. [11] showed that the size of powder particles aects the performance of the heat pipe, and there exists an optimal size for particles in which the maximum operating power and minimum start-up temperature are reached. Jiang et al. [12] reported that sintering process inuences thermal resistance, and porosity thickness and powder diameter aect heat transfer limit. Their results also illustrated that an optimal sintering process should keep balance between high porosity and proper radial shrinkage for mandrel pulling out.
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Design of Heat Exchanger for Efficient Quenching Process of Pipes/Rods

Design of Heat Exchanger for Efficient Quenching Process of Pipes/Rods

Abstract: Generally, manufacturers perform quenching of copper & its alloys pipes right after their extrusion from press. For better grains structure & efficient cooling of pipes, hot pipes are kept into water for a while. Cooling occurs due to heat exchange between quenching fluid & hot pipe by conduction and between hot water & surroundings by natural convection. Since the process of extrusion is continues, quenching of pipes must also be continues .However, conduction leads to rise in temperature of quenching fluid ,which in turn, adversely affects the continuity of the process. Also, rise in surrounding temperature affects worker's ability. To prevent these negative effects, we have to stop all processes until the temperature of hot water does not come into equilibrium to atmospheric temperature. Thus, low heat loss rate of quenching fluid poses problems during continues process. Therefore, Heat loss rate should be rapid & continues. To achieve this purpose, our objective is to design a cooling tower as per requirements, and measure its performance during process of heat exchange & quenching of pipes
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Boiling Heat Transfer on the Outside of A Miniature Diameter Compact Tube Bundle

Boiling Heat Transfer on the Outside of A Miniature Diameter Compact Tube Bundle

Recent interests in the development of a model to predict the local boiling heat transfer coefficient in small circular tube has led to the development of a two-state model by Jacobi and Thome [20]. Jacobi and Thome [20] modeled and developed a method to predict the heat transfer coefficient in small circular tube. It was assumed that the heat transfer coefficient observed in flow boiling was due to an elongated bubble in which transient evaporation was taking place. They concluded that the heat transfer coefficient in the laminar flow of the liquid was negligible compared to the thin film coefficient thus making the model a one–zone model. Parametric studies showed that the model predicted several independent data quite well when it was assumed that the film thickness lies in the range of 10- 20µm for channel size of 2.5mm.
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Effects of Powder Shape and Processing Parameters on Heat Dissipation of Heat Pipes with Sintered Porous Wicks

Effects of Powder Shape and Processing Parameters on Heat Dissipation of Heat Pipes with Sintered Porous Wicks

Heat pipes with sintered porous structures have been used widely to resolve the thermal management problems of electronic devices, such as notebook computers. 1) To provide effective cooling, the water at one end of the sealed heat pipe, which is under partial vacuum, evaporates into vapor that cools the hot device by using the latent heat, and the water vapor then passes through the hollow channel in the core of the heat pipe to the cold end, where the water vapor condenses. This condensed water is then transported back to the hot evaporator section through the capillary pressure in porous copper wicks, which are sinter-bonded to the outer copper tubing. 1) To ensure high heat dissipation, high
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A review of the applications of phase change materials in cooling, heating and power generation in different temperature ranges

A review of the applications of phase change materials in cooling, heating and power generation in different temperature ranges

Saman, F Bruno., Performance enhancement of high temperature latent heat thermal storage systems using heat pipes with and without fins for concentrating solar thermal power plants.. Pit[r]

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Increasing the Energy Output of Solar Hydrogen Power System by Heat Extraction and High Temperature Electrolysis

Increasing the Energy Output of Solar Hydrogen Power System by Heat Extraction and High Temperature Electrolysis

he global awareness and concern about the greenhouse effect and global warming has led the scientists of the world towards developing new technologies that are environment friendly. The development of hydrogen economy* in this area has stimulated widespread attention towards utilizing hydrogen as a future fuel. Solar energy has the potential to meet the present day Worlds demand many times over. 1% of solar energy falling on Earth could provide energy equivalent to run each and every household. But the way to implementation of these technologies require huge capital investments and the results given especially by solar panels do not match up with the investments. Our this work tries to improve the energy output of Solar Hydrogen Power System in two stages i.e. by extracting heat through heat loop pipes from PV panels and by high temperature electrolysis. Regarding feasibility of the work we need not mention that most parts of India have Global Horizontal Irradiance (GHI) for as many as 300 days, thus the proposed methodology by our estimation can improve PV output by 17% and electrolyser output by 4%.
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Comparison Of Thermal Analysis Of Heat Pipe With Silver End At Evaporator Section

Comparison Of Thermal Analysis Of Heat Pipe With Silver End At Evaporator Section

Abstract: Heat pipe is one of the heat transfering devices that transfers heat by following principles of both thermal conductivity & phase transition so that heat can transfer efficiently between two bodies. Heat pipe is a passive heat transfer heat exchange device which is utilized to expel heat from the heat source. The performance and effectiveness of the heat pipe rely on different factors likely working fluid, diameter, wick structure, wick mesh size etc. Here in this project we conducted the experimental work on comparison of copper cylindrical heat pipe and copper cylindrical heat pipe with silver pipe (i.e.combined copper and silver) at one end i.e at its evaporator section using TiO2 (Titanium dioxide) as a working fluid. As silver is more heat conductive than copper, so thermal resistance of is less and it is placed at different angles of 0°,60°, 30°, and 90° with the horizontal. Comparison of thermal performance of two heat pipes is analyzed where the Evaporator thermal resistance at 60° angle for copper with silver heat pipe at a load of 10W is 0.4K/W, total thermal resistance is 1.7K/W and for only copper pipe is 0.6K/W, 2.0K/W respectively.
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Toward TiO2 Nanofluids—Part 2: Applications and Challenges

Toward TiO2 Nanofluids—Part 2: Applications and Challenges

Generally, the biggest downside in application of nano- fluids is the sedimentation and degeneration of nanopar- ticles after long running which makes the long-term performances of nanofluid system challenged. Some re- searchers have proposed a new idea and a novel method to re-disperse the aggregates in real time of the running system [123]. However, the concrete effect of the device has to be verified experimentally, and then, the design and location of the re-dispersion device needs to be im- proved. The surfactant is expected to have positive effect on the re-dispersion characteristic of aggregates. How- ever, one of the biggest flaws in using surfactants is the occurrence of foaming when the fluids are under flowing or heating conditions which would have adverse impacts on the heat or mass transfer application of nanofluids. This defect suggests the amount of surfactant employed in the nanofluids should be limited.
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