scholarly journals Enhanced Heat Transfer Characteristics of Graphite Concrete and Its Application in Energy Piles

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Qingwen Li ◽  
Lu Chen ◽  
Haotian Ma ◽  
Chung-Ho Huang
Keyword(s):  
Heat Transfer ◽  
High Heat ◽  
Transfer Efficiency ◽  
Heat Transfer Characteristics ◽  
Enhanced Heat Transfer ◽  
Energy Pile ◽  
Transfer Characteristics ◽  
Heat Transfer Efficiency ◽  
High Heat Transfer ◽  
Energy Piles

The latest research on energy piles demonstrates that most scholars are focusing their attention on optimization by designing more efficient heat exchanger coils, analyzing the heat pump matching parameters, and so on. However, after more than 20 years of development, these traditional methods for improving the heat transfer efficiency of energy piles have reached a bottleneck, and a new approach for the continued enhancement of this technology must be investigated. In this study, powdered graphite with high heat transfer characteristics was included in a concrete mix to create graphite concrete piles with enhanced heat transfer characteristics. The results from theoretical analysis, laboratory testing, and numerical simulation indicate that using graphite to improve the heat transfer efficiency of a concrete material is an effective method for enhancing the thermal efficiency of an energy pile system. The research results also show that the heat transfer coefficient of the concrete exhibits greater improvement when the graphite content is greater than 15% under the same environmental temperature. After studying the performance of the proposed graphite concrete energy pile under different environmental temperatures (10°C, 20°C, 30°C, and 40°C), the results indicate that the working efficiency of the energy pile is better in the summer than in the winter. Finally, parameters such as the cast-in pipe configuration and pile spacing are optimized.

scholarly journals Heat Transfer and Bearing Characteristics of Energy Piles: Review

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6483
Author(s):  
Jinli Xie ◽  
Yinghong Qin
Keyword(s):  
Heat Transfer ◽  
Low Cost ◽  
High Heat ◽  
Heat Pumps ◽  
Transfer Efficiency ◽  
Ground Source Heat Pumps ◽  
Heat Transfer Efficiency ◽  
High Heat Transfer ◽  
Energy Piles ◽  
Composite Energy

Energy piles, combined ground source heat pumps (GSHP) with the traditional pile foundation, have the advantages of high heat transfer efficiency, less space occupation and low cost. This paper summarizes the latest research on the heat transfer and bearing capacity of energy piles. It is found that S-shaped tubes have the largest heat transfer area and the best heat transfer efficiency; that energy piles need to be designed conservatively, such as adjusting the safety coefficient, number and spacing of the piles according to the additional temperature loads; and that unbalanced surface temperature has not been resolved, caused by uneven refrigeration/heating demand in one cycle. A composite energy pile applied to water-rich areas is proposed to overcome the decay of bearing and heat transfer performance. Besides, most of the heat transfer models are borehole-oriented and will fit for energy piles effectively if the models support variable ground temperature boundary conditions.

A New Design of Mini Heat Exchanger for PEMFC Bipolar Plates

2006 ◽  
Author(s):  
Yahia Lasbet ◽  
Bruno Auvity ◽  
Cathy Castelain ◽  
Hassan Peerhossaini
Keyword(s):  
Heat Transfer ◽  
Fuel Cell ◽  
Electrochemical Reaction ◽  
Electric Energy ◽  
Transfer Efficiency ◽  
Specific Power ◽  
Bipolar Plates ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Heat Transfer Efficiency

Fuel cell is a power generator which directly converts chemical energy to electric energy through an electrochemical reaction instead of thermal combustion. The electrochemical reaction produces as much heat as electric energy. In transport applications where the specific power density of the fuel cell is relatively high a large amount of heat should be evacuated from the system. Therefore, heat exchangers integrated in the bipolar plates play an important role in the operation and life time of fuel cells. Conventional designs of the cooling system of the current bipolar plates consist of a net work of parallel straight channels of half of the bipolar plate’s thickness. These designs reach rapidly their limit of efficacy and new designs are needed. Reynolds number in the bipolar channel flow is around 200; therefore the flow regime is laminar which is known for its weak heat transfer efficiency. In this work we present a new geometry of the cooling channels of bipolar plates in which heat transfer efficiency in laminar regime is enhanced by generating chaotic trajectories. Here we characterize the heat transfer characteristics of a single channel. Firstly, hydrodynamic and heat transfer characteristics of several channel geometries are characterized by using the CFD code Fluent. Thermo-physical properties of the working fluid are those of water and the velocity profile at the channel entrance is that of a fully developed Poiseuile flow. Secondly, fluid mixing along the channels is evaluated using two different criteria. For these calculations, thermal boundary conditions on the channel walls are adiabatic and the entrance of the channel is divided in two (horizontal or vertical) parts. In one part water flows at 300K while in the other part water is at 320K. The first criteria is the ratio of (Tmin/Tmax-Ro)/(1-Ro) over cross-section surfaces calculated for Reynolds numbers 100 and 200 and for both horizontal and vertical positions of the dividing surface at the entrance.

scholarly journals Experimental Investigation of the Flow and Heat Transfer Characteristics in Microchannel Heat Exchangers with Reentrant Cavities

Micromachines ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 403 ◽  
Author(s):  
Binghuan Huang ◽  
Haiwang Li ◽  
Tiantong Xu
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Volume Ratio ◽  
High Heat ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
High Heat Transfer ◽  
The Impact

The application of microchannel heat exchangers is of great significance in industrial fields due to their advantages of miniaturized scale, large surface-area-to-volume ratio, and high heat transfer rate. In this study, microchannel heat exchangers with and without fan-shaped reentrant cavities were designed and manufactured, and experiments were conducted to investigate the flow and heat-transfer characteristics. The impact rising from the radius of reentrant cavities, as well as the Reynolds number on the heat transfer and the pressure drop, is also analyzed. The results indicate that, compared with straight microchannels, microchannels with reentrant cavities could enhance the heat transfer and, more importantly, reduce the pressure drop at the same time. For the ranges of parameters studied, increasing the radius of reentrant cavities could augment the effect of pressure-drop reduction, while the corresponding variation of heat transfer is complicated. It is considered that adding reentrant cavities in microchannel heat exchangers is an ideal approach to improve performance.

Numerical Study on the Effect of Dislocation Relationship on Resistance Characters of the Ceramic Oxidation Bed Based on Fluent Software

2011 ◽  
Vol 347-353 ◽  
pp. 3798-3803
Author(s):  
Yong Qi Liu ◽  
Xiang Chun Chen
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Numerical Study ◽  
High Heat ◽  
Transfer Efficiency ◽  
Heat Transfer Efficiency ◽  
High Heat Transfer ◽  
Fluent Software ◽  
Resistance Loss ◽  
Overall Resistance

As ceramic oxidation bed has high heat transfer efficiency, now, great attention has been given on it. In the oxidation bed, between the honeycomb holes of the fore-and-aft blocks of ceramic honeycombs, there are dislocation relationships. The effect of dislocation relationship on the pressure drop of the oxidation bed was numerically simulated by Fluent software. The results show that, between the two blocks of closely adjacent ceramic honeycombs, when a gap distance of 1mm was left, compared to the situation the gap distance is 0, the overall resistance loss of the oxidation bed reduced vast.

Numerical Study of Heat Transfer Characteristics in Narrow Channel with Staggered Dimples

2014 ◽  
Vol 535 ◽  
pp. 71-74
Author(s):  
Hui Yong Chen ◽  
Shuai Guo
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Numerical Study ◽  
Narrow Channel ◽  
High Heat ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
High Heat Transfer ◽  
Calculation Results

In this paper, numerical simulations were conducted to investigate the flow and heat transfer characteristics of dimple channels. To contrast with the channel with dimples, a numerical study on a smooth plate channel was also made. The results show that in dimple channel, flow separation occurred near dimple windward edge, low heat transfer rate was observed in these regions and dimple wake region owned high heat transfer rate. The calculation results show that the mean Nusselt numbers of dimple channel were 27.58 and the amplification is 15.2%. The friction factor of dimple channel is 0.018 and decrease by 5.26%, the thermal performance parameter TP is 1.18. It can be seen that the heat transfer in the channel is enhanced markedly with the staggered dimples.

High heat flux flow boiling in silicon multi-microchannels – Part I: Heat transfer characteristics of refrigerant R236fa

2008 ◽  
Vol 51 (21-22) ◽  
pp. 5400-5414 ◽  
Author(s):  
Bruno Agostini ◽  
John Richard Thome ◽  
Matteo Fabbri ◽  
Bruno Michel ◽  
Daniele Calmi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Heat Transfer Characteristics ◽  
Flux Flow ◽  
Transfer Characteristics
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