Plate Heat Exchangers – Flow Analysis through Mini Channels

Experimental Research on Variable Hydraulic Resistors of Servo-hydraulic Valves

The heat accumulator can overcome the intermittent and fluctuating problems of the new energy structure and provide a guarantee for the efficiency of the thermal system. It is the most potential energy hub in the energy transition period. Although a lot of research on phase change materials and thermal storage systems has been carried out over the years, there is a lack of systematic and comprehensive research on the classification and evaluation of phase change thermal storage systems. This paper reviewed the recent kinds of literature on the research of phase change heat accumulators, aiming to summarize the research work of phase change heat accumulators. The thermophysical properties of various phase change materials and the selection principles for applying PCM in heat accumulators were analyzed, and the applicability of the method for improving the performance of phase change heat accumulators was introduced. The classification and typical advantages and disadvantages of heat accumulators were summarized and discussed, and the potential methods and research deficiencies of optimizing heat accumulators were found to provide a useful reference for the development of heat accumulators in the future. • The research work on phase change heat accumulators was summarized. • The PCM performance and selection principles were analyzed. • The method of improving the performance of the heat accumulator was introduced. • Potential methods for optimization and missing studies were discussed. 

Research progress and performance improvement of phase change heat accumulators

The paper is a theoretical one that focuses on the influence of dynamic absorbers in the reduction and elimination of torsion vibrations . The dynamic absorber is used for the reduction of the amplitude of the torsion vibrations of crankshafts. According to the construction restrictions , we notice that the dynamic absorber does not increase the number of resonance phenomena, irrespective of the order of the harmonic that causes forced vibrations.

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Theoretical considerations regarding the dynamic absorber

The multi-walled carbon nanotubes (MWCNTs) were synthesized by homemade equipment with the waste alcohol. The synthesized MWCNTs were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), and Raman spectroscopy. Moreover, in confirming the synthesized green/eco-friendly technique, MWCNTs were grown on some of the micropunches to show the attractive potential for bioenergy application compellingly and convincingly. Results show that due to the usage of the waste alcohol, not only is this technique definitely green/eco-friendly to the environment, but also MWCNTs as a protective layer on the micropunch can lengthen the service life of the micropunch by up to 35% without directly affecting the size of the punched holes compared with that of without MWCNTs. Moreover, the punched microholes are definitely quite distinct from that of traditional punching. Besides the fracture band is absent, the areas of rollover and burr are also extremely narrow, which implies the attractive punched microhole can be used directly without any posttreatments.

Carbon Nanotubes Synthesized by Green/Eco-friendly Technique Potential for Bioenergy Applications

The aim of this study is to determine the geometry of a plate for heat exchanger with high heat flow and low values for pressure losses. For this, in Solid Work software, were designed three plate geometries with different crimping angles for the flow channels. Was analyzed the influence of the crimping angle β on the fluid distribution and heat transfer. Also, were compared the data resulted from Computational Fluid Dynamics numeric simulation with the experimental ones for the plate heat exchangers with gaskets. The analysis of the vortices and temperature field distribution was achieved with the aid of simulation software Fluent. In order to validate the numerical simulation's results experimental research were carried out on a heat exchangers stand.

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Study regarding the influence of the crimping angle on the performances of the heat exchangers

Dynamic absorbers are used to reduce torsional vibrations. This paper studies the effect of a dynamic absorber attached to a mechanical system formed of three reduced masses which are acted on by one, two or three order x harmonics of a disruptive force.

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Contributions to the Study of Dynamic Absorbers, a Case Study

Hydropower is the most flexible and consistent of the renewable energy resources. A particular importance should be given to small hydropower plants, because of their large number. Small hydropower plants are sized so the servitude flow is obtained at minimum level of water, and when the level increase this flow increases. The difference between effective servitude stream flow and the amount required by the law, may be considered as a loss of energy in the sense that it could be sent to the turbine, thus increasing the produced energy. For this, it is necessary the use of a sluice gate for flow section  djustments. The paper presents the mathematical model for hydropower constructions of this type (up to 5 MW), which was utilized for numerical simulations, showing the main advantage mentioned above. The flow coefficients in the model were corrected after measurements made at two different hydropower plants. Then, a software application was made for dimensioning: the water intake, accumulation reservoir, desander, charging chamber and supply duct, so all the available flow is used.

https://atna-mam.utcluj.ro/index.php/Acta/article/download/1039/970

Dan Opruta

Papers

Experimental Research on Variable Hydraulic Resistors of Servo-hydraulic Valves

Study regarding the influence of the crimping angle on the performances of the heat exchangers

Contributions to the Study of Dynamic Absorbers, a Case Study

Optimal flow control for increased electricity production in small hydropower plants

Thermal energy storage system applicable to vehicles