A new heat-pipe type solar domestic hot water system

Mathioulakis, E.; Belessiotis, V.

doi:10.1016/s0038-092x(01)00088-3

Cited by 127 publications

(36 citation statements)

References 4 publications

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“…This is different from a wicked heat pipe, where the working fluid is returned from the condenser by capillary forces [1][2][3][4]. Heat pipes have been successfully used for waste heat energy recovery in a vast range of engineering applications, such as heating, ventilation, and air conditioning (HVAC) systems [5], ground source heat pumps [6], water heating systems [7] and electronics thermal management [8]. This is mainly because of their simple structure, special flexibility, high efficiency, good compactness, and excellent reversibility [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Numerical modelling of the temperature distribution in a two-phase closed thermosyphon

Fadhl

Wrobel

Jouhara

2013

Applied Thermal Engineering

243

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A B S T R A C TInterest in the use of heat pipe technology for heat recovery and energy saving in a vast range of engineering applications has been on the rise in recent years. Heat pipes are playing a more important role in many industrial applications, particularly in improving the thermal performance of heat exchangers and increasing energy savings in applications with commercial use. In this paper, a comprehensive CFD modelling was built to simulate the details of the twophase flow and heat transfer phenomena during the operation of a wickless heat pipe or thermosyphon, that otherwise could not be visualised by empirical or experimental work. Water was used as the working fluid. The volume of the fluid (VOF) model in ANSYS FLUENT was used for the simulation. The evaporation, condensation and phase change processes in a thermosyphon were dealt with by adding a user-defined function (UDF) to the FLUENT code. The simulation results were compared with experimental measurements at the same condition. The simulation was successful in reproducing the heat and mass transfer processes in a thermosyphon. Good agreement was observed between CFD predicted temperature profiles and experimental temperature data.

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Section: Introductionmentioning

confidence: 99%

Numerical modelling of the temperature distribution in a two-phase closed thermosyphon

Fadhl

Wrobel

Jouhara

2013

Applied Thermal Engineering

243

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Section: Introductionmentioning

confidence: 99%

“…The condensed liquid is then returned to the evaporator due to gravitational or capillary forces, according to the type of heat pipe [1][2][3][4][5]. Heat pipes have been successfully used for waste heat energy recovery in a vast range of engineering applications, such as heating, ventilation, and air conditioning (HVAC) systems [2], ground source heat pumps [6], water heating systems [7] and electronics thermal management [8].The most important characteristics to consider in identifying suitable working fluids are compatibility and wettability with the heat pipe materials, good thermal stability and conductivity, high latent heat of evaporation, high surface tension and low viscosity for both liquid and vapour [9]. In typical thermosyphons, the selection of the working fluid and the shell materials is subject to the working environment and temperature under which the thermosyphon-based system will function.…”

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confidence: 99%

CFD modelling of a two-phase closed thermosyphon charged with R134a and R404a

Fadhl

Wrobel

Jouhara

2015

Applied Thermal Engineering

165

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This paper examines the application of CFD modelling to simulate the two-phase heat transfer mechanisms in a wickless heat pipe, also called a thermosyphon. Two refrigerants, R134a and R404a, were selected as the working fluids of the investigated thermosyphon. A CFD model was built to simulate the details of the two-phase flow and heat transfer phenomena during the start-up and steady-state operation of the thermosyphon. The CFD simulation results were compared with experimental measurements, with good agreement obtained between predicted temperature profiles and experimental temperature data, thus confirming that the CFD model was successful in reproducing the heat and mass transfer processes in the R134a and R404a charged thermosyphon, including the pool boiling in the evaporator section and the liquid film in the condenser section. INTRODUCTIONA wickless heat pipe is a two-phase heat transfer device with a highly effective thermal conductivity, containing a small amount of working fluid that circulates in a sealed tube utilising the gravity forces to return the condensate back to the evaporator [1]. When the evaporator section is heated by an external source, the heat will be transferred to the working fluid through the evaporator wall. The working fluid absorbs an amount of heat proportional to the latent heat of evaporation, which is sufficient to change the fluid from liquid to vapour. The vapour then moves to the condenser section where it changes phase again, back to liquid, along the condenser's wall, giving up its latent heat that it absorbed in the evaporator section. The condensed liquid is then returned to the evaporator due to gravitational or capillary forces, according to the type of heat pipe [1][2][3][4][5]. Heat pipes have been successfully used for waste heat energy recovery in a vast range of engineering applications, such as heating, ventilation, and air conditioning (HVAC) systems [2], ground source heat pumps [6], water heating systems [7] and electronics thermal management [8].The most important characteristics to consider in identifying suitable working fluids are compatibility and wettability with the heat pipe materials, good thermal stability and conductivity, high latent heat of evaporation, high surface tension and low viscosity for both liquid and vapour [9]. In typical thermosyphons, the selection of the working fluid and the shell materials is subject to the working environment and temperature under which the thermosyphon-based system will function. For low temperature applications, ammonia and various refrigerants such as R134a, R22 and R410a have been used as working fluids with copper, steel, aluminium and other compatible metals as shell materials. Water has been proven to be a suitable working fluid for temperatures between 30°C and 300°C, with good compatibility with various metals including copper and stainless steel. Liquid metals and various organic fluids have been selected for thermosyphons when the working temperature is above 300°C [6,[10][11][12][13][14].Two-phas...

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“…Numerous studies have been carried out to understand the thermal performance of two phase thermosyphon used in solar water heaters. Mathioulakis and Belessiotis (2002) reported the results obtained through both theoretical simulation and experimental investigation of a solar collector with heat pipes. They have used ethanol as working fluid and obtained the maximum instantaneous efficiency up to 60%.…”

Section: Introductionmentioning

confidence: 99%

Performance Enhancement of Two Phase Thermosyphon Flat-Plate Solar Collectors by Using Surfactant and Nanofluid

Sahu¹,

Pise²,

Chougule³

2013

Frontiers in Heat Pipes

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In this study the thermal performance of three different wickless heat pipe solar collectors were investigated by using pure water, watersurfactant and CNT-water nanofluid for different coolant mass flow rates and tilt angles (20 0 , 31.5 0 , 40 0 , 50 0 and 60 0 ). First collector uses only pure water, the second one utilizes CNT nanoparticle of diameter 10-12 nm and 0.1-10 μm length with water as a base fluid. While the third collector uses water with 150 ppm 2-ethyl-hexanol as coolant for the investigation. Experiments were carried out for the three collectors under the same experimental conditions. It is observed that the performance of the solar collector that uses 2-ethyl-hexanol surfactant with water as coolant is better compared to solar collectors that utilize pure water and CNT/water nanofluid.

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A new heat-pipe type solar domestic hot water system

Cited by 127 publications

References 4 publications

Numerical modelling of the temperature distribution in a two-phase closed thermosyphon

Numerical modelling of the temperature distribution in a two-phase closed thermosyphon

CFD modelling of a two-phase closed thermosyphon charged with R134a and R404a

Performance Enhancement of Two Phase Thermosyphon Flat-Plate Solar Collectors by Using Surfactant and Nanofluid

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