THE INFLUENCE FACTORS ON HEAT TRANSFER PERFORMANCE OF LOOP THERMOSYPHON SYSTEM

2016 ◽  
Vol 40 (5) ◽  
pp. 947-958 ◽  
Author(s):  
Li-Chieh Hsu ◽  
Guo-Wei Wong ◽  
Kung-Ting Chen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Influence Factors ◽  
Passive Cooling ◽  
Width Ratio ◽  
Transfer Performance ◽  
Cooling Device ◽  
Cooling Performance ◽  
System A ◽  
Enhanced Boiling

The influence factors on the heat transfer performance of a loop thermosyphon system, a passive cooling device, are studied systematically. The parameters investigated include types of enhanced boiling structure, the depth to width ratio of enhanced boiling structures, the gap of evaporator, the condenser height and the inclination of evaporator. The results show the depth to width ratio and the condenser height has positive influences on the heat transfer performance. An optimal channel gap of evaporator exists and possesses better heat transfer performance. The inclination effect of evaporator may not be favorable to heat transfer. Among those, the horizontal and 90° inclination of evaporator has better cooling performance.

Comparative Study of Cooling Performance of Automobile Radiator Using Al2O3-Water and Carbon Nanotube-Water Nanofluid

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Sandesh S. Chougule ◽  
S. K. Sahu
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Base Fluid ◽  
Heat Transfer Performance ◽  
Pure Water ◽  
Transfer Performance ◽  
Nanoparticle Concentration ◽  
Cooling Performance ◽  
Forced Convective Heat Transfer ◽  
Better Than

In the present study, the forced convective heat transfer performance of two different nanofluids, namely, Al2O3-water and CNT-water has been studied experimentally in an automobile radiator. Four different concentrations of nanofluid in the range of 0.15–1 vol. % were prepared by the additions nanoparticles into the water as base fluid. The coolant flow rate is varied in the range of 2 l/min–5 l/min. Nanocoolants exhibit enormous change in the heat transfer compared with the pure water. The heat transfer performance of CNT-water nanofluid was found to be better than Al2O3-water nanocoolant. Furthermore, the Nusselt number is found to increase with the increase in the nanoparticle concentration and nanofluid velocity.

scholarly journals Effects of multiple-nozzle distribution on large-scale spray cooling via numerical investigation

2019 ◽  
Vol 23 (5 Part B) ◽  
pp. 3015-3024
Author(s):  
Qiang Xie ◽  
Zuobing Chen ◽  
Gong Chen ◽  
Yongjie Yu ◽  
Zheyu Zhao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Large Scale ◽  
Heat Transfer Performance ◽  
Spray Cooling ◽  
Transfer Performance ◽  
Enhance Heat Transfer ◽  
Cooling Performance ◽  
The Mean ◽  
Real Practice

Spray cooling has been widely employed in many applications due to its high flux removal ability. A previous study has been conducted to reveal the large-scale spray cooling performance of an industrial used single nozzle. Continuously, influence of multiple-nozzle distribution has also been numerically investigated in present work. The mean heat flux and its standard deviation and uniformity are used to qualify the cooling performance. A flat wall with 1.6 m in length and 1.0 m in width has been taken as the research object. Effects of nozzle number, distance and offset have been parametrically compared. It is found that increasing nozzle number could promote mean heat flux, improve the uniformity of cooling patterns and enhance heat transfer performance. A best nozzle number of 10 could be obtained by an equation fitting. Decreasing nozzle distance turns out to be detrimental to heat transfer. The reason comes from the collisions and interactions of two too adjacent nozzles. Based on choices in real practice, two types of arrays i. e. perpendicular and skew array have been discussed and compared. It is concluded that the skew array could obtain higher heat flux with more uniform distribution.

Characterization of Microstructures for Heat Transfer Performance in Passive Cooling Devices

2008 ◽  
Author(s):  
Ram Ranjan ◽  
Suresh V. Garimella ◽  
Jayathi Y. Murthy
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Contact Angle ◽  
Heat Transfer Performance ◽  
Passive Cooling ◽  
Liquid Volume ◽  
Geometrical Parameters ◽  
Transfer Performance ◽  
Liquid Meniscus ◽  
Cooling Devices

The topology and geometry of microstructures play a crucial role in determining heat transfer performance in passive cooling devices such as heat pipes. It is therefore important to characterize microstructures based on their wicking performance, the thermal conduction resistance of the liquid filling the microstructure, and the thin-film characteristics of the liquid meniscus. In the present study, the free-surface shapes of the static liquid meniscus in common microstructures have been modeled using the program, Surface Evolver, for zero Bond number. Four well-defined topologies, viz., surfaces with parallel rectangular ribs, horizontal parallel cylinders, vertically aligned cylinders, and spheres (the latter two in both square and hexagonal packing arrangements), have been modeled. Non-dimensional capillary pressure, average distance of the free liquid surface from solid walls (a measure of the conduction resistance of the liquid), total exposed area and thin-film percentage of surface area of the liquid meniscus have been computed. These parameters are presented as functions of the non-dimensional geometrical parameters of the microstructures, volume of the liquid filling the structure, as well as the contact angle between the liquid and solid. Based on these non-dimensional performance parameters, the microstructure, contact angle and non-dimensional liquid volume for the best performance are identified.

Numerical Calculation on Heat Transfer Performance of the Capillary Plane HVAC Terminal System

2008 ◽  
Author(s):  
Wei Bing ◽  
Li Li ◽  
Shuping Zhang ◽  
Jiang Lu
Keyword(s):  
Heat Transfer ◽  
Numerical Calculation ◽  
Indoor Air ◽  
Heat Transfer Performance ◽  
Influence Factors ◽  
Heating System ◽  
Flow Density ◽  
Transfer Performance ◽  
Terminal System ◽  
Average Temperature

Nowadays as a novel terminal air conditioning system, the capillary plane HVAC terminal system is being researched in China. In this system the terminal capillary pipes are buried in the surface of the ceiling or the wall or the floor with the purpose-built grout, the chilled or heated water circulates in the pipes and exchanges the sensible heat with the indoor air by radiation and convection to make the indoor air parameters stable. The capillary mat terminals usually combine with dedicated outdoor air system and the latter takes on the indoor latent heat. Compared with the floor radiant heating system, the capillary plane HVAC terminal system has the advantages of saving more indoor space and any position installation. In this paper, with the method of numerical calculation the heat transfer performance of the capillary pipe buried in the grout are studied, the average temperature of the radiation surface and average heat flow density in summer and winter are figured out, and the influence factors such as: the pipe spacing, pipe embedded depth, pipe diameter, average temperature of the supply and return water, and design indoor air temperature are analyzed respectively. The optimal mode or trend under given conditions are proposed and the relations of the influence factors are summarized. All these above will be good theoretical references for the design and application of the capillary plane HVAC terminal system.

Proposal of a Micro/Mini Cooling Device Using Fins-Installed Porous Media for High Heat Flux Removal Exceeding 1000W/cm2

2009 ◽  
Author(s):  
Kazuhisa Yuki ◽  
Akira Matsui ◽  
Hidetoshi Hashizume ◽  
Koichi Suzuki
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Sink ◽  
Heat Transfer Performance ◽  
High Heat ◽  
Heat Sinks ◽  
High Heat Flux ◽  
Transfer Performance ◽  
Cooling Device ◽  
Fin Thickness

Heat transfer characteristics of micro-sized bronze particle-sintered porous heat sinks and copper minichannel-fins heat sinks are experimentally investigated in order to clarify the feasibility of a newly proposed micro/mini cooling device using fins-installed porous media. Regarding the porous heat sinks, fin effect toward more inside of the porous medium is promoted by sintering the porous heat sink on the heat transfer surface, which results in increasing the heat transfer performance up to 0.8MW/m2K at heat flux of 8.2MW/m2 though there still remains a large pressure loss issue. In addition, the results clarify that the heat exchanging area exists only in the vicinity of the heat transfer surface. As to the minichannel-fins heat sinks, the influence of the channel width and the fin thickness are evaluated in detail. As a result, the minichannel-fins heat sink having the narrower channel width (i.e. scale effect) and lower porosity (i.e. thicker fin thickness with larger heat capacity) achieves higher heat transfer performance up to 0.10MW/m2K at 8.3MW/m2. However, rapid increase of pressure loss, which is occasionally observed in a microchannel due to vapor bubbles choking the narrow channel, still remains as an issue under flow boiling conditions in the minichannel. Finally, heat transfer performance of the fin-installed porous heat sink is numerically predicted by the control volume method. The simulation confirms that the heat transfer coefficient at each wall superheat of 0 and 30 degrees has performance 2.5 times and 2.0 times higher than that of the normal fins, which indicates that this heat sink coupling the micro and mini channels has high potential as efficient cooling method under high heat flux conditions exceeding 10MW/m2.

scholarly journals An experiment to assess the heat transfer performance of thermoelectric-driven conditioned mattress

2021 ◽  
pp. 146-146
Author(s):  
Xiaxia Li ◽  
Liming Shen ◽  
Ying Huang
Keyword(s):  
Heat Transfer ◽  
Thermal Comfort ◽  
Temperature Control ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Cooling Performance ◽  
Water Pipes ◽  
Circulating Water ◽  
Human Thermal Comfort ◽  
Control Layer

This study sets out to describe the design, construction and testing of thermoelectric-driven conditioned mattress intended to reduce the human-mattress interface temperature, in order to satisfy the personal sleep thermal comfort requirements in hot conditions. A prototype of thermoelectric-driven conditioned mattress is constructed and tested. A series of experimental studies related to the temperature of different cushion layers and time from start-up to stable state have been carried out, specifically to analyze the difference in heat transfer performance of two types of temperature control layers (i.e., integral water cushion and circulating water pipes) in cooling operations. The steady-state results showed that, the type of temperature control layer and pre-set temperature exhibited a remarkable influence on the cooling performance of mattress. The mattress with integral water cushion had a superior cooling performance as compared to mattress with circulating water pipes under similar consitons. Specifically, the upper surface temperature of mattress with integral water cushion at the the pre-set temperature of 20?C, 18?C and 16?C were 1.97?C, 2.46?C and 3.08?C lower than indoor air temperature, respectively. Besides, the temperature contour maps of temperature control layer and upper cushion layer for two types of mattresses were constructed using the bilinear interpolation, respectively, thus expected to provide reference for the untested temperatures in this study. This study aims to effectively evaluate the heat transfer performance of the thermoelectric-driven conditioned mattress, and shows highly practical value in further applications of this system in improving human thermal comfort during sleep.

Heat Transfer Performance of Cooling Device for Avionics Equipment Using Heat Pipe

2021 ◽  
Vol 45 (3) ◽  
pp. 165-171
Author(s):  
Sang Jin Park ◽  
Yong Hun Yun ◽  
Kyu Young Sim ◽  
Dae Won Yoon ◽  
Jin Kook Seo
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Cooling Device

Effects of Impinging Hole Shapes on Double Swirl Cooling Performance at Gas Turbine Blade Leading Edge

2018 ◽  
Author(s):  
Junfei Zhou ◽  
Xinjun Wang ◽  
Jun Li ◽  
Daren Zheng
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Thermal Performance ◽  
Heat Transfer Performance ◽  
Leading Edge ◽  
Transfer Performance ◽  
Cooling Performance ◽  
Impingement Cooling ◽  
Cooling Method ◽  
Blade Leading Edge

A double swirl cooling method has been raised recently to enhance the internal cooling performance at the blade leading edge. This paper mainly focuses on investigating the flow and heat transfer characteristics of the double swirl cooling method. Further more, four kinds of elliptical holes are applied to show effects of impinging hole shapes on the cooling performance. Results of all double swirl cooling cases are compared with that of an impingement cooling structure under four Reynolds numbers. Overall averaged Nusselt number, friction factor and thermal performance factor are compared in all cases, Vortexes induced by different impinging hole types and target chambers are studied and compared. The spanwise averaged Nusselt number, Nusselt number contours and Nusselt number distributions at several cross sections are studied and compared. Results show that the double swirl cooling method can significantly enhance the heat transfer performance compared with the traditional impingement cooling structure. Double swirl cooling with cylindrical impinging hole shows the best thermal performance and lowest flow losses. By applying the elliptical impinging hole with the sharp side faced the mainstream flow direction and a larger major to minor axis length ratio, the rotational vortex inside the double swirl chamber can be better developed and the heat transfer performance is also promoted.

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