scholarly journals Heat Transfer Enhancement of Circular- and Petal- Shaped Double-Tube-Type Heat Exchangers by Triple Ones

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6590
Author(s):  
Toshihiko Shakouchi ◽  
Kazuma Yamamura ◽  
Koichi Tsujimoto ◽  
Toshitake Ando
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Cold Water ◽  
High Heat ◽  
Hot Water ◽  
Compact Heat Exchangers ◽  
Heat Transfer Efficiency ◽  
High Heat Transfer ◽  
Tube Type ◽  
Counter Current

Conventional circular double or triple tube type heat exchanger, DHE or THE, is one of the compact heat exchangers; a large number of studies have been performed to improve their heat transfer performance. The authors demonstrated that a petal-shaped special DHE with a large wet perimeter yields a high heat transfer efficiency, η. In this study, the DHE with six or five petals-, five shallow petals-, and circular-inner tubes were used. To further improve the η of the DHE, a THE with a petal-shaped inner tube along with the middle and outer circular tubes were used. Hot water flowed through the inner tube and cold water flowed through the middle and outer tubes as a counter current flow. The heat transfer was approximately equal; however, the flow resistance (pressure loss) of the outer tube of the DHE could be decreased using the middle and outer tubes under the same amount of cold water as the DHE; consequently, the η could be improved. In addition, the effect of changing the flow path of the hot- and cold-water flows on the η was examined.

Heat Transfer Enhancement of Double-Tube-Type Heat Exchanger by Petal-Shaped Tube (Study on Optimum Tube Shape)

2018 ◽  
Vol 11 (1) ◽  
Author(s):  
Toshihiko Shakouchi ◽  
Yusuke Matsumoto ◽  
Koichi Tsujimoto ◽  
Toshitake Ando
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
High Heat ◽  
Practical Applications ◽  
Heat Transfer Efficiency ◽  
High Heat Transfer ◽  
Tube Shape ◽  
Tube Type ◽  
Wetted Perimeter ◽  
Fin Tube

Abstract Heat exchangers are used widely in many fields, and various kinds of exchanger have been developed according to the requirement of the practical applications. Recently, heat exchangers that are highly efficient or compact have become more desirable from the viewpoint of energy conservation, and several new types have been developed, such as a compact fin tube type and a double tube type having an inner pipe with a special geometry. In this study, the flow and heat transfer characteristics of a petal-shaped double tube with a large wetted perimeter of six and five petals and five shallow petals and the effect of tube shape on the heat transfer and heat transfer efficiency were examined experimentally. The heat transfer of the double tube with a petal-shaped inner tube was increased because of the large wetted perimeter, but the pressure loss by friction increased. The optimal shape of the petal-shaped double tube with a high heat transfer performance and the greatest efficiency is discussed.

scholarly journals Numerical Study of Flow Maldistribution in Multi-Plate Heat Exchangers Based on Robust 2D Model

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3121 ◽  
Author(s):  
Arkadiusz Brenk ◽  
Pawel Pluszka ◽  
Ziemowit Malecha
Keyword(s):  
Heat Exchangers ◽  
Numerical Study ◽  
High Heat ◽  
Pressure Balance ◽  
Plate Heat ◽  
Pressure Losses ◽  
Heat Transfer Efficiency ◽  
High Heat Transfer ◽  
Wide Range ◽  
Flow Maldistribution

Plate heat exchangers (PHE) are characterized by high heat transfer efficiency and compactness. An exploitation problem of the PHE is related to flow maldistribution, which can make part of the PHE idle, resulting in overheating and damage. Making geometrical modifications to the PHE can help reduce flow maldistribution. Modifications should be kept to a minimum, so as not to complicate the production process. There is a large number of possible geometrical modifications, which simply considers additional obstacles or stream dividers. To test all of them would be impractical and would also take a prohibitively long amount of time to obtain experimental measurements. A typical PHE is characterized by a complex system of channels. Making numerical calculations of its 3D model can be prohibitively time and resource-consuming. The present work introduces a physically consistent methodology of the transformation of a real 3D geometry to its 2D representation. Its main novelty is to assure the same pressure drop balance remains between the 3D and 2D geometries. This is achieved by a preservation of the same cumulative pressure losses in both geometries. The proposed innovative approach levels the pressure balance difference by adding properly designed local geometrical modifications. The developed methodology allowed a wide range of parameter space and various geometrical modifications to be investigated, and revealed geometrical optimizations leading to the improved performance of the PHE. To minimize the influence of other factors, an incompressible and single-phase flow was studied.

Review of the Development of Compact, High Performance Heat Exchangers for Gas Turbine Applications

2006 ◽  
Author(s):  
Neal R. Herring ◽  
Stephen D. Heister
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Gas Turbine ◽  
Heat Exchangers ◽  
High Performance ◽  
High Heat ◽  
Swirl Flow ◽  
Acoustic Oscillations ◽  
Transfer Coefficients ◽  
High Heat Transfer

This study provides a review of the current state-of-the-art in compact heat exchangers and their application to gas turbine thermal management. Specifically, the challenges and potential solutions for a cooled cooling air system using the aircraft fuel as a heat sink were analyzed. As the sensible heat absorbed by the fuel in future engines is increased, the fuel will be exposed to increasingly hotter temperatures. This poses a number of design challenges for fuel-air heat exchangers. The most well known challenge is fuel deposition or coking. Another problem encountered at high fuel temperatures is thermo-acoustic oscillations. Thermo-acoustic oscillations have been shown to occur in many fluids when heated near the critical point, yet the mechanism of these oscillations is poorly understood. In some cases these instabilities have been strong enough cause failure in the thin walled tubes used in heat exchangers. For the specific application of a fuel-air heat exchanger, the advantages of a laminar flow device are discussed. These devices make use of the thermal entry region to achieve high heat transfer coefficients. To increase performance further, heat transfer enhancement techniques were reviewed and the feasibility for aerospace heat exchangers was analyzed. Two of the most basic techniques for laminar flow enhancement include tube inserts and swirl flow devices. Additionally, the effects of these devices on both coking and instabilities have been assessed.

Mesoscale Combustor/Evaporator Development

1999 ◽  
Author(s):  
Kriston P. Brooks ◽  
Peter M. Martin ◽  
M. Kevin Drost ◽  
Charles J. Call
Keyword(s):  
Heat Transfer ◽  
High Heat ◽  
Heat Fluxes ◽  
Hot Water ◽  
Fabrication Process ◽  
Coolant Temperature ◽  
Reduced Pressure ◽  
Compact Source ◽  
Aspect Ratios ◽  
High Heat Transfer

Abstract Battelle has developed a mesoscale combustor/evaporator that provides a lightweight and compact source of heating, cooling, or energy generation for both man-portable and stationary applications. The device uses microscale flow channels that increase the available surface area for heat transfer and reduce the fluid boundary layer. These characteristics in turn result in heat fluxes for hydrocarbon/air combustion in excess of 25 W/cm2 and thermal efficiencies of 80 to 90%. Furthermore, high heat transfer rates allow for short channels and reduced pressure drops. Recent development efforts have focused on obtaining low emissions and improving the combustor/evaporator fabrication process. By using spatially varying stoichiometry inside the combustor, catalyst coated microchannels, and increased coolant temperature, the combustor’s CO and NOx emissions were reduced to below California standards for hot water heaters and boilers. The fabrication process photochemically machines thin metal laminates and then uses diffusion bonding to form a monolithic component. This approach is capable of high fin aspect ratios and can be scaled up for mass production.

Research on the Heat Transfer Characteristics of Receiver in Designed Solar Direct Steam Generation System

2014 ◽  
Vol 472 ◽  
pp. 286-290
Author(s):  
Jing Long Du ◽  
Xiang Huang ◽  
Da Wei Tang
Keyword(s):  
Heat Transfer ◽  
High Heat ◽  
Stable Operation ◽  
Steam Generation ◽  
Generation System ◽  
Heat Transfer Efficiency ◽  
High Heat Transfer ◽  
Direct Steam ◽  
Attractive Option ◽  
Simulation Results

The direct steam generation (DSG) with parabolic collector is an attractive option regarding the economic improvement of parabolic technology for solar thermal electricity generation system. On the basis of theory analysis of flow and heat transfer mechanism in the DSG system, this paper presents the numerical simulation results of one 650 meters loop under different direct normal irradiation values, performance parameters such as water temperature, heat transfer coefficient and dryness of the fluid in the absorber pipe are obtained in the simulation results. This paper shows that fluids parameters are susceptible to the solar direct normal values , high heat transfer efficiency and sensitive control system are the key to ensure DSG systems stable operation.

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.

Decreasing the Fouling of Heat Exchanger Plates Using Air Bubbles

2010 ◽  
Vol 297-301 ◽  
pp. 1199-1204 ◽  
Author(s):  
Seung Moon Baek ◽  
Won Sil Seol ◽  
Ho Saeng Lee ◽  
Jung In Yoon
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Environmental Pollution ◽  
High Heat ◽  
Air Bubbles ◽  
Heat Transfer Efficiency ◽  
High Heat Transfer ◽  
Heat Exchanger Plate ◽  
Removal Equipment ◽  
Exchanger Plate

The heat transfer performance of heat exchanger plate decreases as time goes by. The main reason for this phenomenon is the fouling of the heat exchanger plates. To remove the fouling, we have usually cleaned the plate of heat exchanger using chemicals or polishing brush or cloth with hand after stopping the equipment and disassembling the heat exchanger. However, to clean the plate using these methods, the heat exchanger equipment needs to be stopped and disjointed. In addition, it must be re-jointed after cleaning. Especially, the concern of environmental pollution happens in case of using chemicals. Therefore, we need to develop an automatic fouling removal equipment which can continuously keep high heat transfer efficiency and solve the problem of environmental pollution. So, in this paper, we developed and tested the equipment which can clean the fouling on heat exchanger plates automatically per constant period and interval using air bubbles. The total heat transfer coefficient decreased with a slower tendency when using air bubbles compared to the existing methods. There was 10% higher heat transfer effect air bubbles every 10 minutes for 2 hours to remove the fouling ingredients on the heat transfer surface area concerned to the case without air bubbles after 192 hours.

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.

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