Evaluation and Improvement of Thermal Energy of Heat Exchangers with SWCNT, GQD Nanoparticles and PCM (RT82)

Abstract

Today, due to the reduction of energy resources in the world and its pollutants, energy storage methods and increase the thermal efficiency of various systems are very important. In this research, the thermal efficiency and energy storage of two heat exchangers have been investigated in series using phase change materials (RT82) and single wall carbon nanotubes (SWCNT) and graphene quantum dot nanoparticles (GQD) In this research, two heat exchangers have been used in combination. The first heat exchanger was in charge of storing thermal energy and the second heat exchanger was in charge of heat exchange. The reason for this is to improve the heat exchange of the main exchanger (shell and tube) by using heat storage in the secondary exchanger, which has not been addressed in previous research. The results of this study showed that using two heat exchangers in series, the thermal efficiency of the system has increased. Also, the heat energy storage of the double tube heat exchanger was obtained using phase change materials in the single-walled carbon nanotube composition of about 3000 W. The average thermal efficiency of the two heat exchangers as the series has increased by 52%. In general, the effect of the two heat exchangers on each other was investigated in series with two approaches (energy storage and energy conversion) using fin and nanoparticles, which obtained convincing results.

Enhancing cooling performance and economic analysis of a vertical earth air heat exchanger (VEAHE) through geometric shape optimization

“…On the other hand, fluid expansion in cylindrical chambers causes fluid circulation in the upper and lower part of the chamber, which itself is a reason for increasing the contact surface of the fluid and the wall, and as a result, increases the cooling performance of the system. 62…”

Evaluation and Improvement of PCM Melting in Double Tube Heat Exchangers Using Different Combinations of Nanoparticles and PCM (The Case of Renewable Energy Systems)

“…Validation of numerical simulation of melting of the PCM was performed in the study. First, an initial run was performed and the predictions were compared with the experimental data of Hosseini et al [16] and Rostami et al [42], as shown in Figure 3. It is clearly noted in Figure 3 that a good agreement between the predictions and measured data was found.…”

“…Furthermore, the left and right points of the HTF demonstrate less melting. This is because the presence of side fins has prevented the natural convection due to PCM melting at the lower points of the heat transfer, while the highest amount of melting has occurred in the upper hemisphere of the heat transfer and between the two fins, which was due to the heat transfer from HTF Center [42][43][44][45]. Furthermore, with the increase of this process and heat circulation, it moves to the lower points.…”

“…Increasing the mass fraction of nanoparticles in nano-HTF model has a far milder impact on the melting process than in another structural type, and the best possible case is to use a mass fraction of 1% of SWCNT in nano-HTF type, so that in this, the conditions create a balance between the effects of natural convection and thermal conductivity in HTF. While the increase of nanoparticles increases the density and gravity gradient and decreases the buoyancy force and natural convection [42,43]. The fin structure generally accelerates the melting of the PCM because the heat transfer surfaces increased, but with more time from the process and the appearance of a mushy state in the PCM, this fining compound prevents the ascent of thermal vortices due to natural convection.…”

“…In general, the use of nanoparticles and fin has played a complementary and very good role on the process of HTF temperature progress in PCM, so that nanoparticles and fin have a positive effect on the heat transfer rate of the heat exchanger. However, natural convection after the formation of a mushy state in PCM and a decrease in density and an increase in buoyancy force has played a complementary role in the process of melting the phase changing materials [16,42]. Figure 7 shows the average PCM temperature in different states of the nanoparticle composition.…”