scholarly journals THERMAL PERFORMANCE ENHANCEMENT OF A VERTICAL THERMOSYPHON HEAT PIPE BY FLOW CONTROL OF THE TWO PHASES

2021 ◽  
Vol 25 (01) ◽  
pp. 109-122
Author(s):  
Alaa A. B. Temimy ◽  
◽  
Adnan A. Abdulrasool ◽  
Keyword(s):  
Heat Pipe ◽  
Thermal Performance ◽  
Performance Enhancement ◽  
Flow Patterns ◽  
Working Fluid ◽  
Three Dimensional Model ◽  
Complex Flow ◽  
Condenser Section ◽  
Evaporator Section ◽  
Two Phases

Heat Pipe (THP) has a continues evaporation/ condensation cycles of the working fluid. The flow patterns of the two phases is founds by previous published articles, as a non-steady complex spatial flow pattern. This type of the flow blocks the easy moving of the two-phases and limits the thermal performance of the THP. In this study, a copper tubes packing (TP) is simulated numerically to control/manage the flow streams of the two phases inside the THP. The simulated THP is 600mm length made of copper partially filled with water. The TP is consist of a two copper tubes attached contrary to each other with a neighboring openings. The upper tube (Riser tube) facilitate the moving of steam streams from evaporator section to the top of the condenser section. The lower tube (Down-comer tube) facilitate the moving of the condensate streams from the condenser section to the bottom of the evaporator section. The tested filling ratios are (40,50,55,60 and 70) % of evaporator section volume. The supplied heats are (50,75,100,150 and 200) W. The Computational Fluid Dynamics solution are done for a three dimensional model (3DCFD) using ANSYS/ Fluent R19.0 software. The simulation result of the steam volume fractions contours shows that the insertion of TP control the flow streams of both phases. Also prevent the formation of complex flow patterns then enhance the axial velocity vectors and reduce cross velocity vectors. The inserted TP provide a regular circulation paths for the working fluid phases and enhance evaporation /condensation processes. Hence it’s reduce the thermal resistance of the THP about 55% and enhance the thermal performance with the same percentage. In addition, the thermal performance of the enhanced TPTHP is not/a little influence due to the variation of the filling ratio.

Heat Transport Limitation of a Triangular Micro Heat Pipe

2003 ◽  
Author(s):  
D. Sugumar ◽  
Kek Kiong Tio
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Operating Temperature ◽  
Working Fluid ◽  
Transport Capacity ◽  
Condenser Section ◽  
Micro Heat Pipe ◽  
Evaporator Section ◽  
Higher Temperature ◽  
Specific Temperature

A micro heat pipe will operate effectively by achieving its maximum possible heat transport capacity only if it is to operate at a specific temperature, i.e., design temperature. In reality, micro heat pipe’s may be required to operate at temperatures different from the design temperature. In this study, the heat transport capacity of an equilateral triangle micro heat pipe is investigated. The micro heat pipe is filled optimally with working fluid for a specific design temperature and operated at different operating temperatures. For this purpose, water, pentane and acetone was selected as the working fluids. From the numerical results obtained, it shows that the optimal charge level of the micro heat pipe is dependent on the operating temperature. Furthermore, the results also shows that if the micro heat pipe is to be operated at temperatures other than its design temperature, its heat transport capacity is limited by the occurrence of flooding at the condenser section or dryout at the evaporator section, depending on the operating temperature and type of working fluid. It is observed that when the micro heat pipe is operated at a higher temperature than its design temperature, the heat transport capacity increases but limited by the onset of dryout at the evaporator section. However, the heat transport capacity decreases if it is to be operated at lower temperatures than its design temperature due to the occurrence of flooding at condenser end. From the results obtained, we can conclude that the performance of a micro heat pipe is decreased if it is to be operated at temperatures other than its design temperature.

Experimental Study of a Curved Rotating Heat Pipe

2008 ◽  
Vol 130 (10) ◽  
Author(s):  
T. A. Jankowski ◽  
F. C. Prenger ◽  
A. Razani
Keyword(s):  
Heat Pipe ◽  
Thermal Management ◽  
Working Fluid ◽  
Heat Sources ◽  
Refrigeration System ◽  
Condenser Section ◽  
Rotating Machine ◽  
Thermal Management System ◽  
Axis Of Rotation ◽  
Evaporator Section

A curved rotating heat pipe for use in motor and generator applications is studied experimentally. The heat pipe is built so that both the condenser and evaporator sections are parallel to the axis of rotation. The condenser section is close to the axis of rotation while the evaporator section can be placed in contact with off-axis heat sources in the rotating machine. The geometry is achieved by incorporating an S-shaped curve between the on-axis rotating condenser section and the off-axis revolving evaporator section. The curved rotating heat pipe allows for a direct coupling of the rotating condenser section to an on-axis stationary refrigeration system, while allowing the revolving evaporator section to intercept off-axis heat sources in the rotating machine. An experimental rotating heat pipe test apparatus was built and operated. The test data indicate that the working fluid continued to circulate, resulting in heat transfer with a high effective thermal conductivity, with the curved rotating heat pipe operating under the influence of centrifugal accelerations approaching 400g. Furthermore, the experimental results were used to validate a heat pipe thermal model that can be used in the design of rotating machines that rely on the curved rotating heat pipe as part of the thermal management system.

Thermal Resistance of a Rotating Closed-Loop Pulsating Heat Pipe: Effect of Centrifugal Accelerations

2016 ◽  
Vol 851 ◽  
pp. 292-298
Author(s):  
Niti Kammuang-Lue ◽  
Deuansavanh Phommavongsa ◽  
Kritsada On-Ai ◽  
Phrut Sakulchangsatjatai ◽  
Pradit Terdtoon
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Closed Loop ◽  
Working Fluid ◽  
Outer Side ◽  
Gravitational Acceleration ◽  
Pulsating Heat Pipe ◽  
Centrifugal Acceleration ◽  
Condenser Section ◽  
Evaporator Section

Objective of this study is to experimentally investigate the effect of centrifugal accelerations on thermal resistance of the rotating closed-loop pulsating heat pipe (RCLPHP). The RCLPHPs were made of a copper tube with internal diameter of 1.50 and 1.78 mm and bent into flower’s petal-shape and arranged into a circle with 11 turns. The evaporator section located at the outer end of the bundle while the condenser section placed around the center of the RCLPHP with no adiabatic section. Both sections had an identical length of 50 mm. R123, and ethanol was filled as working fluid respectively. The RCLPHP was installed on the test rig and it was rotated by the DC motor at the centrifugal acceleration of 0.5, 1, 3, 5, 10, and 20 times of the gravitational acceleration considering at the connection between the evaporator and condenser section. Heat input was generated by electrical annular-plate heaters and varied from 30 to 50, 100, 150, and 200 W. Ceramic papers, wooden plate, and insulation sheet were consecutively attached on the outer side of the heaters in order to prevent the heat loss from the heater. It can be concluded that when the centrifugal acceleration increases, the thermal resistance continuously decreases since the condensate flows back to the evaporator section more rapidly.

Effect of Tube Bending on Heat Transfer Characteristics of Miniature Heat Pipe with Sintered Porous Media

2011 ◽  
Vol 312-315 ◽  
pp. 1015-1020 ◽  
Author(s):  
P. Sakulchangsatjatai ◽  
N. Thuchayapong ◽  
P. Terdtoon ◽  
N. Sangsirakoup
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Pipe ◽  
Working Fluid ◽  
Tube Bending ◽  
Heat Transfer Characteristics ◽  
Small Space ◽  
Condenser Section ◽  
Transfer Characteristics ◽  
Evaporator Section

Miniature heat pipe is a compact heat transfer device with very high heat transfer capability. The miniature heat pipes have been widely accepted for thermal management in laptop computer. Generating heat from chip-set is rapidly transferred to a heat sink via the miniature heat pipe which occupies small space, resulting in smaller and more attractive size of the laptop. Heat pipe bending is unavoidable in such small space. However, tube bending decreases thermal performance of heat pipe and it stops working in some cases. In this study, a computer program to simulate heat transfer characteristics of a bending water-copper-sintered-wick heat pipe has been established. Domains of heat pipe consist of three parts; vapor of working fluid in vapor core which transfer heat and mass from evaporator section to condenser section, liquid of working fluid in wick which transfer heat and mass from condenser section to evaporator section in porous media by capillary force, and container wall. In simulation, fluid flow and heat transfer were assumed to be steady, laminar and incompressible. The porous media is saturated with liquid and working fluid is assumed to be Newtonian fluid. The governing equations, i.e. continuity, Navier-Stokes, and energy equations, and boundary conditions were solved by using the Finite Element Method (FEM). Several bending angles (0 and 90; angle measured from straight pipe) with 6 mm outer diameter and 200 mm length were simulated and tested. It was found that the predicted and experimental thermal resistances of heat pipe, when bending angle increases from 0 to 90, increased from 0.47°C/W to 0.65°C/W and 0.67°C/W to 0.88°C/W respectively, due to rising of the vapor pressure drop in vapor channel. The simulation results are in agreement with experimental data with 26-29% error.

scholarly journals Sodium-Potassium Alloy Heat Pipe under Geyser Boiling Experimental Study: Heat Transfer Analysis

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7582
Author(s):  
Hongzhe Zhang ◽  
Fang Ye ◽  
Hang Guo ◽  
Xiaoke Yan
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heating Power ◽  
Heat Transfer Analysis ◽  
Working Fluid ◽  
Condenser Section ◽  
Sodium Potassium ◽  
Alloy Heat ◽  
Convection Cooling ◽  
Boiling Mode

In the geyser boiling mode, the working fluid state is divided into a boiling process and a quiet process, and the sodium-potassium (Na-K) alloy heat pipe can discontinuously transfer heat at each boiling. The overheating of the liquid working fluid at the bottom causes short-term boiling and forms slug bubble, the strong condensing ability quickly conducts heat from the evaporator section. And geyser boiling can occur before the working fluid forms continuous flow, so it transfers more heat at lower temperatures than natural convection cooling. In this study, the heat transfer process of a Na-K alloy heat pipe with forced convection cooling under different heating power was experimental studied. The geyser boiling mode can make the Na-K alloy heat pipe work below 650 °C and reduce the start-up time. In the process of geyser boiling, the heat transfer quantity was increased by the boiling frequency and the amount of vapor produced in a single boiling. The boiling temperature had no obvious change with the increased of heating power, and the condenser section temperature increased with the heating power.

Experimental Investigation of Thermal Conduction Performance on Silicon-Based Micro Flat Heat Pipe

2015 ◽  
Vol 645-646 ◽  
pp. 1032-1037
Author(s):  
Cong Ming Li ◽  
Yi Luo ◽  
Chuan Peng Zhou ◽  
Liang Liang Zou ◽  
Xiao Dong Wang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Pipe ◽  
Effective Thermal Conductivity ◽  
Thermal Performance ◽  
Axial Direction ◽  
Filling Ratio ◽  
Parallel Structure ◽  
Working Fluid ◽  
Vacuum Degree ◽  
Structure Dimension

There are several factors that affect heat transfer of heat pipe, for example, structure dimension, filling ratio and vacuum degree of charging. This paper studied the thermal conductivity of micro flat heat pipes (MFHPs) with different structure dimension and with different filling ratio, when the charging vacuum degree of MFHP was decided. When electric power was 2W or 4W, MFHPs with parallel grooves and nonparallel grooves, charged by working fluid with different filling ratio, were carried out. And the filling ratio is 30%, 40% and 50%, respectively. The better thermal performance of MFHP can be evaluated by lower thermal resistance and higher effective thermal conductivity. The experiment results show that MFHP has the highest effective thermal conductivity when the filling ratio is 40%; and the thermal performance of MFHP with nonparallel structure in axial direction is better than that of MFHP with parallel structure.

Reciprocating-Mechanism Driven Heat Loops and Their Applications

2003 ◽  
Author(s):  
Yiding Cao ◽  
Mingcong Gao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Electronics Cooling ◽  
Working Fluid ◽  
High Heat Flux ◽  
Two Phase ◽  
Condenser Section ◽  
Evaporator Section ◽  
Two Phase Heat Transfer ◽  
Transfer Device

This paper introduces a novel heat transfer mechanism that facilitates two-phase heat transfer while eliminating the so-called cavitation problem commonly encountered by a conventional pump. The heat transfer device is coined as the reciprocating-mechanism driven heat loop (RMDHL), which includes a hollow loop having an interior flow passage, an amount of working fluid filled within the loop, and a reciprocating driver. The hollow loop has an evaporator section, a condenser section, and a liquid reservoir. The reciprocating driver is integrated with the liquid reservoir and facilitates a reciprocating flow of the working fluid within the loop, so that liquid is supplied from the condenser section to the evaporator section under a substantially saturated condition and the so-called cavitation problem associated with a conventional pump is avoided. The reciprocating driver could be a solenoid-operated reciprocating driver for electronics cooling applications and a bellows-type reciprocating driver for high-temperature applications. Experimental study has been undertaken for a solenoid-operated heat loop in connection with high heat flux thermal management applications. Experimental results show that the heat loop worked very effectively and a heat flux as high as 300 W/cm2 in the evaporator section could be handled. The applications of the bellows-type reciprocating heat loop for gas turbine nozzle guide vanes and the leading edges of hypersonic vehicles are also illustrated. The new heat transfer device is expected to advance the current two-phase heat transfer device and open up a new frontier for further research and development.

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