Re-entrant groove heat pipe

Harwell, W.; Kaufman, W. B.; Tower, Leonard K.

doi:10.2514/6.1977-773

Cited by 16 publications

(7 citation statements)

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“…(20), "þ" is applied when the average velocity of the vapor phase is greater than that of liquid at the liquid/vapor interface; otherwise "À" is applied…”

Section: Flow Analysismentioning

confidence: 99%

“…This causes the liquid fill amount inside the liquid channel to be so critical that a small decrease in liquid fill may result in a significant decrease in the capillary pumping pressure and, hence, a significant decrease in the maximum heat transport capacity. Heat pipe with axial "X"-shaped groove has been introduced as an attractive option for a wide variety of advanced electronic devices, such as in the spacecraft thermal control system and microelectronic cooling system, due to the high efficiency heat transfer capability, stable operation under microgravity conditions and the high degree of temperature uniformity [18][19][20]. As an optimum choice of high capacity heat pipe with axial grooves in the frame provided by the European Space Agency [21], heat pipe with axial "X"-shaped grooves combines a high capillary pumping pressure with a low axial pressure drop in the return liquid, whose cross-sectional structure is shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

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Evaporative Heat Transfer Analysis of a Heat Pipe With Hybrid Axial Groove

Bai¹,

Lin

Peterson

2013

Journal of Heat Transfer

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Through the application of thin film evaporation theory and the fundamental operating principles of heat pipes, a hybrid axial groove has been developed that can greatly enhance the performance characteristics of conventional heat pipes. This hybrid axial groove is composed of a V-shaped channel connected with a circular channel through a very narrow longitudinal slot. During the operation, the V-shaped channel can provide high capillary pressure to drive the fluid flow and still maintain a large evaporative heat transfer coefficient. The large circular channel serves as the main path for the condensate return from the condenser to the evaporator and results in a very low flow resistance. The combination of a high evaporative heat transfer coefficient and a low flow resistance results in considerable enhancement in the heat transport capability of conventional heat pipes. In the present work, a detailed mathematical model for the evaporative heat transfer of a single groove has been established based on the conservation principles for mass, momentum and energy, and the modeling results quantitatively verify that this particular configuration has an enhanced evaporative heat transfer performance compared with that of conventional rectangular groove, due to the considerable reduction in the liquid film thickness and a corresponding increase in the evaporative heat transfer area in both the evaporating liquid film region and the meniscus region.

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“…(20), "þ" is applied when the average velocity of the vapor phase is greater than that of liquid at the liquid/vapor interface; otherwise "À" is applied…”

Section: Flow Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evaporative Heat Transfer Analysis of a Heat Pipe With Hybrid Axial Groove

Bai¹,

Lin

Peterson

2013

Journal of Heat Transfer

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“…Special attention is paid to the rational and complex use of a flat HP with biphase heat-transfer fluid as a partition, and the organization of heat input in the case of flow-over of warm, exhausted air (the evaporation zone below) and heat removal (the condensation zone above), using fin fan computer heat exchangers (aluminum, aluminumcopper radiators ) [3,4]. The objects of the research are HP and fans-heat recupretors based on high-conductivity heat pipes [5].…”

Section: Introductionmentioning

confidence: 99%

Experimental research of heat recuperators in ventilation systems on the basis of heat pipes

2017

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Abstract. The paper presents the results of experimental studies of heat pipes and their thermo-technical characteristics (heat power, conductivity, heat transfer resistance, heat-transfer coefficient, temperature level and differential, etc.). The theoretical foundations and the experimental methods of the research of ammonia heat pipes made of aluminum section АS -КRА 7.5 -R1 (made of the alloy AD -31) are explained. The paper includes the analysis of the thermo-technical characteristics of heat pipes as promising highly efficient heat transfer devices, which may be used as the basic elements of heat exchangers -heat recuperators for exhaust ventilation air, capable of providing energy-saving technologies in ventilation systems for housing and public utilities and for various branches of industry. The thermo-technical characteristics of heat pipes (HP) as the basic elements of a decentralized supply-extract ventilation system (DSEVS) and energy-saving technologies are analyzed. As shown in the test report of the ammonia horizontal HP made of the section АS-КRА 7,5-R1-120, this pipe ensures safe operation under various loads.

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“…Previous researchers (e.g., Harwell et al [1], Alario et al [4], Henson [6], Brandt et al [9]) have modelled the flow of liquid in both re-entrant groove heat pipes and in monogroove heat pipes as a one-dimensional laminar flow through a smooth-walled tube in order to determine the pressure drop (Po = f Re = 16). In addition, the effect of the shear stress at the liquid-vapor interface has not been accounted for.…”

mentioning

confidence: 99%

“…However, these structures lead to a relatively high axial pressure drop in the liquid and, therefore, the second aim cannot be fulfilled. Harwell et al [1] described the heat transfer characteristics of an axially-grooved aluminum extrusion with a re-entrant groove profile. A typical cross section for this type of heat pipe is shown in Fig.…”

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confidence: 99%

Analysis of Fluid Flow in Axial Re-entrant Grooves with Application to Heat Pipes

Thomas

Damle

2004

37th AIAA Thermophysics Conference

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The fully developed laminar flow within a re-entrant groove has been analyzed using a finite element model. Re-entrant grooves have been used in both axially-grooved heat pipes and in monogroove heat pipes. The main benefit to using this type of wick structure is the reduction of the liquid pressure drop along the length of the groove due to countercurrent liquid-vapor interaction at the meniscus. All previous researchers assumed that the pressure drop within the liquid could be modelled as flow within a smooth tube, but the results of the current analysis show that this assumption can lead to significant errors in the pressure drop prediction. An extensive literature survey was completed and the results of five previous studies were used to validate the current numerical model. It was found that the present finite element model is both more accurate and consumes less computer resources than a finite difference based model developed previously by one of the authors of the current manuscript. A parametric analysis was carried out to determine the Poiseuille number, Po = f Re, the dimensionless mean velocity, v * , and the dimensionless volumetric flow rate,V * , as functions of the geometry of the re-entrant groove (groove height 1.0 ≤ H * ≤ 4.0, slot half-width 0.05 ≤ W * /2 ≤ 0.9, fillet radius 0.0 ≤ R * f ≤ 1.0), and the liquid-vapor shear stress (0.0 ≤ −τ * lv ≤ 2.5). It was determined that the flow variables were strongly affected by the groove height, slot half-width and liquid-vapor shear stress, but were relatively unaffected by the fillet radius. The case in which the meniscus recedes into the re-entrant groove was examined, which could be a result of evaporator dry-out or insufficient liquid fill amount. The cross-sectional area of the liquid in the groove, A * l , the meniscus radius, R * m , and the above-mentioned flow variables were calculated as functions of the meniscus contact angle (0 • ≤ φ ≤ 40 • ) and meniscus attachment point (0.0 ≤ H * l ≤ 2.75). In general, the flow variables were more strongly affected by the meniscus attachment point than the meniscus contact angle. Finally, the results of the numerical model were used to determine the capillary limit of a low-temperature heat pipe with two different working fluids, water and ethanol, for a range of meniscus contact angles. The capillary limit heat transfer was found to attain a maximum value in the slot region and then decreased dramatically when the meniscus receded into the circular region of the re-entrant groove. NomenclatureA g = total cross-sectional area of the re-entrant groove, m = maximum mean liquid velocity, m/s v * = µv/R 2 (−dp/dy) v * = µv/R 2 (−dp/dy) V = volumetric flow rate, vA l , m 3 /ṡ V * = µV /[R 4 (−dp/dy)] W = width of the slot, m W * = W/R W l = width of the liquid meniscus at the attachment point to the re-entrant groove wall, m= width of the liquid meniscus at the attachment point to the sinusoidal groove wall, m W s = width of the sinusoidal groove, m W tr = width of the trapezoidal groove, m x, y, z = Carte...

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Re-entrant groove heat pipe

Cited by 16 publications

References 1 publication

Evaporative Heat Transfer Analysis of a Heat Pipe With Hybrid Axial Groove

Evaporative Heat Transfer Analysis of a Heat Pipe With Hybrid Axial Groove

Experimental research of heat recuperators in ventilation systems on the basis of heat pipes

Analysis of Fluid Flow in Axial Re-entrant Grooves with Application to Heat Pipes

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