Experimental Study on Oscillating Heat Pipe With a Hydraulic Diameter Far Exceeding the Maximum Hydraulic Diameter

2020 ◽  
Vol 12 (6) ◽  
Author(s):  
Lilin Chu ◽  
Yulong Ji ◽  
Hongbin Ma ◽  
Yantao Li ◽  
Chao Chang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Input ◽  
High Speed ◽  
Heat Transfer Performance ◽  
Power Input ◽  
Hydraulic Diameter ◽  
Working Fluid ◽  
Transfer Performance ◽  
Vertical Orientation ◽  
Oscillating Heat Pipe

Abstract In order to understand the heat transfer performance, startup, and fluid flow conditions of oscillating heat pipes (OHPs) with a hydraulic diameter far exceeding the maximum hydraulic diameter (MHD) defined by dh,max≤2σBo/(ρl−ρv)g, an experimental investigation on the OHP heat transfer performance and visualization was conducted. The effects of heat input, working fluid, and orientation on the oscillating motion and heat transfer performance of the investigated OHPs have been conducted. In addition, the detailed flow patterns of the tested OHPs were recorded by a high-speed camera from both vertical and horizontal orientations. Results show that the maximum hydraulic diameter, which can form a train of liquid plugs and vapor bubbles, which is essential for an OHP to function, depends on the heat input, working fluid, and orientation. At a power input of 1000 W, the OHP can still function well even when the tube diameter exceeds the MHD of 91.6%. This maximum hydraulic dimeter depends on the orientation. While the OHP with a dimeter far exceeding the MHD can still function, the heat transfer performance of the OHP in a vertical orientation is better than in a horizontal orientation.

Experimental Study on Oscillating Heat Pipe With Hydraulic Diameter Far Exceeding the Maximum Hydraulic Diameter

2019 ◽  
Author(s):  
Lilin Chu ◽  
Yulong Ji ◽  
Chunrong Yu ◽  
Yantao Li ◽  
Hongbin Ma ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Hydraulic Diameter ◽  
Working Fluid ◽  
Transfer Performance ◽  
Vertical Orientation ◽  
Oscillating Heat Pipe ◽  
Horizontal Orientation ◽  
Small Bubbles

Abstract In order to understand the heat transfer performance, startup and fluid flow condition of oscillating heat pipe (OHP) with hydraulic diameter far exceeding the maximum hydraulic diameter (MHD), an experimental investigation on heat transfer performance and visualization was conducted. From the experimental performance, it is found that the OHP can still work well with ethanol as the working fluid when the tube diameter has exceeded the MHD of 91.6%. In addition, the detailed flow patterns of the OHP were recorded by a highspeed camera for vertical and horizontal orientation to understand its physical mechanism. In the vertical orientation, initially working fluid generates small bubbles, and then the small bubbles coalesce and grow to vapor plugs, the vapor plugs finally pushes the liquid slugs to oscillate in the tube. In the horizontal orientation, the working fluid surface fluctuates due to the vapors flow from the evaporator to the condenser and bubbles burst in the evaporator. When the peak of liquid wave reaches the upper surface of tube, a liquid slug has been formed, and then the steam flow pushes the liquid slugs to oscillate in the tube.

Experimental Investigation of Oscillating Heat Pipe With Hybrid Fluids of Liquid Metal and Water

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Tingting Hao ◽  
Hongbin Ma ◽  
Xuehu Ma
Keyword(s):  
Heat Transfer ◽  
Liquid Metal ◽  
Heat Pipe ◽  
Heat Input ◽  
Heat Transfer Performance ◽  
Pure Water ◽  
Experimental Results ◽  
Working Fluid ◽  
Transfer Performance ◽  
Oscillating Heat Pipe

A new oscillating heat pipe (OHP) charged with hybrid fluids can improve thermal performance. The key difference in this OHP is that it uses room temperature liquid metal (Galinstan consisting of gallium, indium, and tin) and water as the working fluid. The OHP was fabricated on a copper plate with six turns and a 3 × 3 mm2 cross section. The OHP with hybrid fluids as the working fluid was investigated through visual observation and thermal measurement. Liquid metal was successfully driven to flow through the OHP by the pressure difference between the evaporator and the condenser without external force. Experimental results show that while added liquid metal can increase the heat transport capability, liquid metal oscillation amplitude decreases as the filling ratio of liquid metal increases. Visualization of experimental results show that liquid metal oscillation position and velocity increase as the heat input increases. Oscillating motion of liquid metal in the OHP significantly increases the heat transfer performance at high heat input. The lowest thermal resistance of 0.076 °C/W was achieved in the hybrid fluids-filled OHP with a heat input of 420 W. We experimentally demonstrated a 13% higher heat transfer performance using liquid metal as the working fluid compared to an OHP charged with pure water.

Experimental Investigation of Ultrasonic Effect on an Acetone Oscillating Heat Pipe

2013 ◽  
Author(s):  
Nannan Zhao ◽  
Benwei Fu ◽  
Dianli Zhao ◽  
Hongbin Ma
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Power Input ◽  
Input Power ◽  
Transfer Performance ◽  
Oscillating Heat Pipe ◽  
Ultrasonic Effect ◽  
Ultrasonic Sound ◽  
Oscillating Motion

The ultrasonic effect on the oscillating motion and heat transfer in an oscillating heat pipe (OHP) containing acetone was investigated experimentally. The ultrasonic sound was applied to the evaporating section of the OHP by using electrically-controlled piezoelectric ceramics. The ultrasonic sound is used to generate and maintain the oscillating motion, and, thereby, heat transfer is enhanced. The heat pipe was tested with or without the ultrasonic sound. In addition, the effects of heat load, filling ratio, orientation, operating temperature, and input power from 15 W to 200 W were investigated. The experimental results demonstrate that ultrasonic sound can affect the oscillating motions and enhance the heat transfer performance of the acetone OHP. In particular, the application of the ultrasonic sound on an acetone OHP can significantly reduce the thermal resistance of the acetone OHP and enhance the heat transfer performance in a low power input region. The investigation will provide an insight into the oscillating mechanism of the acetone OHP influenced by ultrasonic sound and provide a new way to enhance the heat transfer performance of the OHP.

Heat Transfer Characteristics of Horizontal Nano-Structured Oscillating Heat Pipes

2019 ◽  
Author(s):  
Tingting Hao ◽  
Huiwen Yu ◽  
Xuehu Ma ◽  
Zhong Lan
Keyword(s):  
Heat Transfer ◽  
Heat Input ◽  
Capillary Force ◽  
Heat Transfer Performance ◽  
Filling Ratio ◽  
Water Evaporation ◽  
Working Fluid ◽  
Transfer Performance ◽  
Structured Surface ◽  
Inner Surface

Abstract Working fluid in the oscillating heat pipe (OHP) with low turn number (< 9) positioned in the horizontal heat mode could not easily backflow to the evaporator due to the absence of gravity. In this paper, copper OHP with superhydrophilic nano-structured inner surface by introducing additional capillary force was investigated through the visualization and thermal experiments. OHPs with 6 turns, charged with pure water as the working fluid, were fabricated with copper, and nano-structured inner surface and tested for comparison. Contact angles of water on the copper and superhydrophilic surface were 36.7 and 0 deg. The filling ratio of water was 50%, 65%, and 80%, respectively. Startup performance, thermal resistance, and liquid slug oscillation of OHPs were investigated experimentally at the heat input of 100–380 W. Experimental results showed that OHPs with the superhydrophilic nano-structured surface showed an enhanced heat transfer performance due to the nanostructure-induced capillary action for water in the horizontal direction. The optimum filling ratio was 65% in this work. Dryout was observed in the OHPs with the filling ratio of 50% at the heat input higher than 220 W. At the filling ratio of 80%, the working fluid was accumulated in the adiabatic and condensation section, and the driving force due to the water evaporation in evaporator was not high enough to activate the movements of liquid slugs. Heat transfer performance of OHP with nano-structured surface was higher than that of bare copper surface by introducing the additional capillary force.

An Experimental Investigation of the Heat Transfer Performance of an Oscillating Heat Pipe With Copper Oxide (CuO) Microstructure Layer on the Inner Surface

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Yulong Ji ◽  
Chen Xu ◽  
Hongbin Ma ◽  
Pan Xinxiang
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Copper Oxide ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Working Fluid ◽  
Transfer Performance ◽  
Oscillating Heat Pipe ◽  
Inner Surface ◽  
Copper Tubing

This paper presents an experimental investigation of whether heat transfer performance in an oscillating heat pipe (OHP) would improve if the inner surface of the heat pipe was coated with a layer of copper oxide (CuO). The OHP had six turns and three sections, i.e., evaporator, condenser, and adiabatic section with lengths of 40 mm, 64 mm, and 51 mm, respectively. The cleaned copper tubing was chemically treated with a chemical solution and heated in a furnace. A microstructure layer of CuO was formed in the inner surface of the OHP with K2S2O8 and KOH. The working fluid in this study was water with filling ratios ranging from 40% to 70%. The experimental results show that the CuO microstructure layer is superhydrophilic and can enhance the OHP heat transfer performance. The investigation results in a new way to enhance the heat transfer performance of an OHP.

Heat Transfer Characteristics of Oscillating Heat Pipe With Water and Ethanol as Working Fluids

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Haizhen Xian ◽  
Yongping Yang ◽  
Dengying Liu ◽  
Xiaoze Du
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Inclination Angle ◽  
Heat Transfer Performance ◽  
Filling Ratio ◽  
Working Fluid ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Oscillating Heat Pipe ◽  
Transfer Characteristics

In this paper, experiments were conducted to achieve a better understanding of the oscillating heat pipe (OHP) operating behavior with water and ethanol as working fluid. The experimental results showed that there existed a necessary temperature difference between the evaporator and the condenser section to keep the heat pipe working. The maximum effective conductivity of the water OHP reached up to 259 kW/m K, while that of the ethanol OHP is of 111 kW/m K. Not all the OHPs are operated in the horizontal operation mode. The heat transfer performance of the ethanol OHP was obviously affected by the filling ratio and the inclination angle but the influence law is irregular. The effect of the filling ratio and the inclination angle of the water OHP were smaller than that of the ethanol one. The heat transfer performance of the OHP was improved with increase of operating temperature. The startup characteristics of the OHP depended on the establishment of the integral oscillating process, which was determined by the operating factors. The startup temperature of the ethanol OHP varied from 40°C to 50°C and that of the water, OHP varied from 40°C to 60°C without considering the horizontal operating mode. The water OHP showed a better performance and more stable heat transfer characteristics than the ethanol OHP, which had no obvious advantages of the startup capability as well.

Copper Oxide (CuO) Effect on Heat Transfer Performance in an Oscillating Heat Pipe

2012 ◽  
Author(s):  
Yulong Ji ◽  
Chen Xu ◽  
Hongbin Ma
Keyword(s):  
Heat Transfer ◽  
Copper Oxide ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Working Fluid ◽  
Transfer Performance ◽  
Oscillating Heat Pipe ◽  
Inner Surface ◽  
Copper Tubing ◽  
Adiabatic Section

An experimental investigation of an oscillating heat pipe (OHP) with an inner surface coated with a copper oxide (CuO) layer was conducted. The OHP has six turns and three sections: evaporator, condenser and adiabatic section with the lengths of 40 mm, 64 mm and 51 mm, respectively. The cleaned copper tubing was chemically treated with a chemical solution and heated in a furnace. A layer of CuO was formed in the inner surface of the OHP. A working fluid (water in this study) at filling ratios ranging from 40% to 70% was studied. The experimental results show that the CuO layer can enhance the heat transfer performance of the OHP. The investigation results in a new way to enhance the heat transfer performance of an OHP.

Experimental Studies on the Isothermal and Heat Transfer Performance of Trough Solar Power Collectors

2014 ◽  
Vol 1044-1045 ◽  
pp. 320-326 ◽  
Author(s):  
Yun Liu ◽  
Hong Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Thermal Power ◽  
Experimental Studies ◽  
Power Input ◽  
Working Fluid ◽  
Transfer Performance ◽  
Medium Temperature ◽  
Temperature Heat

The medium temperature heat pipe is a highly effective heat transfer element through heat exchange due to phase change of the liquid organic working fluid. A medium temperature heat pipe used in solar energy receiver of parabolic trough thermal power generating system has been analysed, and a medium temperature heat pipe with liquid organic working fluid has been designed. The isothermal performance and heat transfer performance of the medium temperature heat pipe with liquid organic working fluid have been tested under various power input and different inclined angles. Test proves that axial temperature difference of half circle heated medium temperature heat pipe is smaller, and the half circle heated heat pipe with inclined angle is 4°and 8°can work stably, having good axial isothermal performance and heat transfer performance, the influence on isothermal performance and heat transfer performance of the medium temperature heat pipe can be neglected.

Experimental Investigation of a Three-Phase Oscillating Heat Pipe

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Tingting Hao ◽  
Hongbin Ma ◽  
Xuehu Ma
Keyword(s):  
Heat Transfer ◽  
Liquid Phase ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Transfer Performance ◽  
Solid Phase ◽  
Working Fluid ◽  
Transfer Performance ◽  
Oscillating Heat Pipe ◽  
Three Phase

This paper presents an investigation of a three-phase oscillating heat pipe (3P OHP). The working fluid in the OHP consists of phase change material (PCM) and water. During the operation, the PCM changes the phase between solid and liquid, and water changes phase between liquid and vapor. The OHP investigated herein contains three phases: solid, liquid, and vapor. Erythritol was selected as the PCM with an instant cooling effect when dissolved in water due to the high fusion heat of 340 J/g. When the working fluid flows into the evaporator section, the PCM solid phase of the working fluid can become liquid phase in the evaporator, and the PCM liquid phase of the working fluid become solid phase in the condenser. The effects of heat input ranging from 100 to 420 W, and the erythritol concentration ranging from 1 to 50 wt % on the slug oscillations, and the OHP thermal performance was investigated. Experimental results show that while the erythritol can help to increase the heat transfer performance of an OHP, the heat transfer performance depends on the erythritol concentration. With a range of 1–5 wt % concentration of erythritol/water mixtures, a maximum 10% increase in the thermal performance was observed. When the erythritol concentration of erythritol/water mixtures was increased to a range of 10–50 wt %, the thermal performance of OHPs was lower than pure water-filled OHP, and the thermal performance decreased as the erythritol concentration was further increased. In addition, visualization results showed that slug oscillation amplitudes and velocities were reduced in the OHPs with erythritol solution compared with water-filled OHP.

An Investigation of Flat-Plate Oscillating Heat Pipes

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Peng Cheng ◽  
Scott Thompson ◽  
Joe Boswell ◽  
H. B. Ma
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Flat Plate ◽  
Cross Sections ◽  
Heat Transfer Performance ◽  
Heat Pipes ◽  
Power Input ◽  
Copper Plate ◽  
Working Fluid ◽  
Transfer Performance

The heat transfer performance of flat-plate oscillating heat pipes (FP-OHPs) was investigated experimentally and theoretically. Two layers of channels were created by machining grooves on both sides of a copper plate in order to increase the channel number per unit volume. The channels had rectangular cross-sections with hydraulic diameters ranging from 0.762 mm to 1.389 mm. Acetone, water, diamond/acetone, gold/water, and diamond/water nanofluids were tested as working fluids. It was found that the FP-OHP’s thermal resistance depended on the power input and operating temperature. The FP-OHP charged with 0.0003 vol % gold/water nanofluids achieved a thermal resistance of 0.078 K/W while removing 560 W with a heat flux of 86.8 W/cm2. The thermal resistance was further decreased when the nanofluid was used as the working fluid. A mathematical model predicting the heat transfer performance was developed to predict the thermal performance of the FP-OHP. Results presented here will assist in the optimization of the FP-OHP and provide a better understanding of heat transfer mechanisms occurring in OHPs.

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