Theoretical analysis of laminar-film condensation heat transfer inside inclined wickless heat pipes flat-plate solar collector

Hussein, H.M.S.; Mohamad, M.A.; Elasfouri, A.S.

doi:10.1016/s0960-1481(00)00149-x

Cited by 51 publications

(19 citation statements)

References 3 publications

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“…Heat pipes eliminate the welding and scale formation while it gives 88% efficiency with low cost. [38] suggest that the pipe inclination angle have a substantial effect on heat transfer inside the wickless heat pipe. Similarly [39] shows that the increase in number of wickless heat pipe gives a significant effect on the collector efficiency.…”

Section: Micro Tubes Flat Plate Collectormentioning

confidence: 98%

A Review on Revolution of Flat Plate Collector for Solar Water Heater

Patil¹

2018

IJRASET

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Energy is the significant need of the world either for nutrition or for development of the society. The power bank of the earth is the sun, which has tremendous amount of energy in it and will never exhaust. The conversion of solar energy to thermal energy is the function of collector. Flat plate collector (FPC) are cost effective and more convenience in all collectors. The paper reveals the different design of the flat collectors used to enhance the efficiency of the collector. Effect of using phase change material, nanofluids, heat pipe, different geometry of the tubes and absorber discussed. This review deals with the suggestion for the research work in flat plate collector. Keywords: FPC Design; Solar Collectors; different collectors for SWH; Design of SWH I. INTRODUCTIONEnergy is the most important and a key factor in day-to-day life. The keen interest is towards the solar energy which is a pure green energy and available in plenty. The energy of Sun used to heat the water, which is the great need of each human being for various purposes. During review it is found that the various solar water heating system were made by many researchers with relatively high efficiency and reasonable cost, but the system does not meet the requirement of other countries due to climatic conditions and many other reasons. Today environment is the major issue and the awareness regarding the environment is increasing this promote solar and renewable energy system in world and decreases the dependencies' on fossil fuels. The solar water heating system consist of riser tubes, absorbers a dark surface plate, insulation and glazed glass. The system when exposed to the sun, the absorber absorbs the solar radiation and transfers a part of it to the fluid flowing over/under it [3][4][5][6][7]. The more is the collector area more will be the energy, but the law of thermodynamics state that no machine can gives 100% output therefore we even cannot get the 100% percent conversion. Now, the design goals were to have the collector that can convert the maximum solar energy to heat energy with a lesser amount of losses; and cost. The objective for the review of solar water heating system is to get the various designs available and invented by researchers at one place to get the idea of possible development in it with the future of design in Solar Water Heater (SWH). The review is limited to the flat plate collector and other similar to it. There are two broad categories of SWH (passive and active), each of them operating in either direct or indirect mode. The active systems give 35%-80% efficiency higher than those of the passive systems [3].

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Section: Micro Tubes Flat Plate Collectormentioning

confidence: 98%

A Review on Revolution of Flat Plate Collector for Solar Water Heater

Patil¹

2018

IJRASET

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“…The solution can also be used for condensation inside tubes. Hussein et al (2001) proposed a numerical model, also derived from Nusselt's theory, but for an application of condensation in thermosyphons. In the model, a steady-state two-dimensional model is solved to determine the liquid film thickness.…”

Section: Thermal Modelling Of Separated Condensing Flowsmentioning

confidence: 99%

“…In the model, a steady-state two-dimensional model is solved to determine the liquid film thickness. Both in the Fieg and Roetzel (1994) and in the Hussein et al (2001) models, gravitational and shear forces are taken into account but capillary forces are neglected. A major assumption of these models is that the liquid film thickness is supposed to be small compared with the tube radius.…”

Section: Thermal Modelling Of Separated Condensing Flowsmentioning

confidence: 99%

Stratified flow model for convective condensation in an inclined tube

Lips

Meyer

2012

International Journal of Heat and Fluid Flow

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Experimental data are reported for condensation of R134a in an 8.38 mm inner diameter smooth tube in inclined orientations with a mass flux of 200 kg/m²s. Under these conditions, the flow is stratified and there is an optimum inclination angle, which leads to the highest heat transfer coefficient. There is a need for a model to better understand and predict the flow behaviour. In this paper, the state of the art of existing models of stratified two-phase flows in inclined tubes is presented, whereafter a new mechanistic model is proposed. The liquidvapour distribution in the tube is determined by taking into account the gravitational and the capillary forces.The comparison between the experimental data and the model prediction showed a good agreement in terms of heat transfer coefficients and pressure drops. The effect of the interface curvature on the heat transfer coefficient has been quantified and has been found to be significant. The optimum inclination angle is due to a balance between an increase of the void fraction and an increase in the falling liquid film thickness when the tube is inclined downwards. The effect of the mass flux and the vapour quality on the optimum inclination angle has also been studied.

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“…For small thermosyphon length to radii ratios (L c /r i ≤ 20), the thermosyphon tube is modeled as laminar film condensation on a flat inclined surface, where the condensed film returns to the evaporator by gravity and evaporates completely by the end of the evaporator section (i.e., no liquid pool exists at the base of the 7 evaporator). However, for larger length to radii ratios (L c /r i > 20), a modified heat transfer coefficient correlation is used that better captures the circumferential liquid film thickness variation due to thermosyphon inclination (Hussein, 2001). The vapor is assumed to be at saturation conditions, and shear forces are negligible (Faghri, 1995) resulting in thermal resistances of evaporation and condensation heat transfer described by Eqns.…”

Section: Thermosyphon Modelingmentioning

confidence: 99%

Modeling and optimization of hybrid solar thermoelectric systems with thermosyphons

2011

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We present the modeling and optimization of a new hybrid solar thermoelectric (HSTE) system which uses a thermosyphon to passively transfer heat to a bottoming cycle for various applications. A parabolic trough mirror concentrates solar energy onto a selective surface coated thermoelectric to produce electrical power. Meanwhile, a thermosyphon adjacent to the back side of the thermoelectric maintains the temperature of the cold junction and carries the remaining thermal energy to a bottoming cycle. Bismuth telluride, lead telluride, and silicon germanium thermoelectrics were studied with copper-water, stainless steel-mercury, and nickel-liquid potassium thermosyphonworking fluid combinations. An energy-based model of the HSTE system with a thermal resistance network was developed to determine overall performance. In addition, the HSTE system efficiency was investigated for temperatures of 300 K -1200 K, solar concentrations of 1 -100 suns, and different thermosyphon and thermoelectric materials with a geometry resembling an evacuated tube solar collector. Optimizations of the HSTE show ideal system efficiencies as high as 52.6% can be achieved at solar concentrations of 100 suns and bottoming cycle temperatures of 776 K. For solar concentrations less than 4 suns, systems with thermosyphon wall thermal conductivities as low as 1.2 W/mK have comparable efficiencies to that of high conductivity material thermosyphons, i.e. copper, which suggests that lower cost materials including glass can be used. This work provides guidelines for the design, as well as the optimization and selection of thermoelectric and thermosyphon components for future high performance HSTE systems.

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Theoretical analysis of laminar-film condensation heat transfer inside inclined wickless heat pipes flat-plate solar collector

Cited by 51 publications

References 3 publications

A Review on Revolution of Flat Plate Collector for Solar Water Heater

A Review on Revolution of Flat Plate Collector for Solar Water Heater

Stratified flow model for convective condensation in an inclined tube

Modeling and optimization of hybrid solar thermoelectric systems with thermosyphons

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