Study of Influence Effect on Heat Transfer Performance of Single-Loop Oscillating Heat Pipe

2014 ◽  
Vol 535 ◽  
pp. 114-118 ◽  
Author(s):  
Su Lei
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Filling Rate ◽  
Oscillating Heat Pipe ◽  
Heating Section ◽  
Cooling Section

s. The experiment studied the effect of heat source temperature, heating section length ratio, cooling air flow rate, liquid filling rate and pipe diameter on the heat transfer performance of the single-loop red copper-water oscillating heat pipe. The results show that increasing heat source temperature or pipe diameter and reducing filling rate can obviously reduce the thermal resistance of the heat pipe; in the air cooling mode, the cooling thermal resistance outside the pipe is affected by both cooling conditions and heat pipe cooling section average temperature; when the heating section is shorter than the cooling section, the heat pipe thermal resistance shows an apparent trend of increasing with the increase of heating section length ratio, when the heating section is longer than the cooling section, the cooling thermal resistance increases with it apparently; the heat transfer power is the highest when the filling rate is 50%.

scholarly journals Study on Heat Transfer Performance of Non-integral Capillary Core Sintered Uniform Plate

2021 ◽  
Vol 7 (5) ◽  
pp. 292-301
Keyword(s):  
Heat Transfer ◽  
Particle Size ◽  
Heat Source ◽  
Thermal Resistance ◽  
Copper Powder ◽  
Heat Transfer Performance ◽  
Copper Plate ◽  
Transfer Performance ◽  
Filling Rate ◽  
Large Particle Size

This paper mainly introduces the sintering process of the monolithic capillary wick and analyzes the influence of different copper powder particle size, filling rate, copper powder shape and heat source size on the heat transfer performance of the isothermal plate. The experimental results show that: (1) For the isothermal plate sintered with spherical copper powder, the capillary force of large particle size copper powder is small, but the flow resistance is also small, and the performance of the isothermal plate sintered with large particle size copper powder is better. (2) In the case of low filling rate, the isothermal plate is dried due to insufficient return fluid. In the case of high filling rate, on the one hand, the thickness of the liquid film at the evaporation end of the isothermal plate is large, resulting in additional thermal resistance. On the other hand, the thin film evaporation mode will be transformed into pool boiling mode, which will reduce the heat transfer performance. (3) Spherical copper powder sintered plate with regular shape has the best performance, while dendritic copper powder sintered plate has relatively high thermal resistance. (4) The heat source area has a great influence on the thermal resistance of the plate. Under the same heating power, the thermal resistance of the small area heat source is much higher than that of the large area heat source; The thermal resistance of sintered copper plate is lower than that of pure copper plate under two heat source areas.

Experimental Investigation on the Effects of Inclination Angle on Heat Transfer Performance of a Liquid Metal High-Temperature Oscillating Heat Pipe

2021 ◽  
Author(s):  
Mengke Wu ◽  
Yulong Ji ◽  
Yanmin Feng ◽  
Xin Yang ◽  
Yadong Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Inclination Angle ◽  
Heat Transfer Performance ◽  
Input Power ◽  
Transfer Performance ◽  
Oscillating Heat Pipe ◽  
Inclination Angles

Abstract The liquid metal high-temperature oscillating heat pipe (LMHOHP) is a kind of high efficiency heat transfer device, which can function in high-temperature environments above 500°C. In this paper, the effects of inclination angle on the startup and heat transfer performance of a LMHOHP were investigated experimentally. The sodium-potassium alloy (potassium 78%) was used as the working fluid of the LMHOHP and the filling ratio was 50%. The start-up characteristics and heat transfer performance of the LMHOHP at four inclination angles of 0°, 30°, 60° and 90° were tested when the operating temperatures were 150°C and 400°C, respectively. Experimental results show that (1) The LMHOHP can start-up and function at all the tested inclination angles, the maximum temperatures of the evaporator and condenser can exceed 1000°C and 700°C, respectively. (2) The thermal resistance of the LMHOHP decreases with inclination angle increases, the thermal resistance at the inclination angle of 90° decreases by up to 32.9%, 41.6% and 55.9% compared with that at the inclination angle of 60°, 30° and 0°, respectively. (3) When the input power exceeds 3000W, the flow patterns of LMHOHP at the inclination angle of 90°, 60° and 30° can be changed from the oscillating motion to the unidirectional circulating flow. (4) Compared with the operating temperature of 150°C, the heat transfer performance of the LMHOHP improves at the operating temperature of 400°C, at the input power of 3457W and the inclination angle of 90°, the minimum thermal resistance of LMHOHP is 0.075°C/W. The results shown that the LMHOHP has a good adaptability to working conditions which further extends the application range of oscillating heat pipe.

Study on Periodic Thermal-Switching Behavior of Flat Heat Pipe

2015 ◽  
Author(s):  
Shigeki Hirasawa ◽  
Tatsuya Nakamu ◽  
Tsuyoshi Kawanami ◽  
Katsuaki Shirai
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Switching Behavior ◽  
Transfer Performance ◽  
Unsteady Heat Transfer ◽  
Cold Energy ◽  
Thermal Switching ◽  
Flat Heat Pipe

The coupling of the electrocaloric effect in thin films with thermal switches has the potential to be used for efficient refrigeration. We studied the unsteady heat transfer performance and periodic thermal-switching behavior of a flat heat pipe to transfer cold energy from a changing heat source. The condenser of the flat heat pipe was the changing heat source and changed from −20 W to +20 W every 5 s. The temperature of the condenser surface changed in accordance with the heat generation of the heat source. The evaporator was a plate with a mesh wick attached to a water-flow pipe. Cold energy transferred from the condenser surface to the evaporator surface only when the temperature of the condenser surface was lower than that of the evaporator surface. We analyzed the unsteady temperature change and heat transfer performance of the flat heat pipe by numerical simulation. The analytical results showed that it was necessary to have two thermal switches to separate the heat energy and cold energy of the changing heat source. Also, it was important to reduce the thermal resistance and heat capacity of the evaporator surface to improve the unsteady heat transfer performance of the heat pipe. Next, we measured the unsteady heat transfer performance of the flat heat pipe experimentally. The experimental results showed that the thermal-switching behavior was observed when the heat generation of the heat source changed every 5 s.

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.

scholarly journals Research on Heat Transfer Performance of Micro-Channel Backplane Heat Pipe Air Conditioning System in Data Center

2020 ◽  
Vol 10 (2) ◽  
pp. 583
Author(s):  
Liping Zeng ◽  
Xing Liu ◽  
Quan Zhang ◽  
Jun Yi ◽  
Xianglong Liu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Pipe ◽  
Temperature Difference ◽  
Air Conditioning ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Micro Channel ◽  
Filling Rate ◽  
Air Conditioning System

This paper deals with the heat transfer performance of a micro-channel backplane heat pipe air conditioning system. The optimal range of the filling rate of a micro-channel backplane heat pipe air conditioning system was determined in the range of 65–75%, almost free from the interference of working conditions. Then, the influence of temperature and air volume flow rate on the heat exchange system were studied. The system maximum heat exchange is 7000–8000 W, and the temperature difference between the inlet and outlet of the evaporator and the condenser is almost 0 °C. Under the optimum refrigerant filling rate, the heat transfer of the micro-channel heat pipe backplane system is approximately linear with the temperature difference between the inlet air temperature of the evaporator and the cooling distribution unit (CDU) inlet water temperature in the range of 18–28 °C. The last part compares the heat transfer characteristics of two refrigerants at different filling rates. The heat transfer, pressure, and refrigerant temperature of R134a and R22 are the same with the change of filling rate, but the heat transfer of R134a is lower than that of R22. The results are of great significance for the operational control and practical application of a backplane heat pipe system.

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.

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