Numerical simulation of the fluid dynamics within the tissue engineering scaffolds micro-tubes

The core of tissue engineering is the fabrication of a complex three-dimensional space with cells and biomaterials. In the development of porous scaffolds in vitro, no matter the seed cells ran into the scaffold, or its excretion of waste discharged scaffolds, they both need the nutrient solution to be brought into or taken out. Therefore, the flow of the nutrient solution, cells and metabolic waste for the profitable living in vitro culture plays a significant role. the paper constructed bone scaffold models of different geometric parameters, analog cells, and nutrient solution flow conditions in the scaffolds using the FLUENT software. By making a contrastive analysis with the simulated result, the internal organizational design parameters of scaffold for tissue engineering is optimized and a certain amount of data and a theoretical basis for the internal bone scaffold structure design is provided

Research on heat transfer characteristics of serpentine tube

In order to reduce energy consumption and improve the efficiency of CO2 heat pumps, a numerical simulation method was used to study the heat transfer characteristics of supercritical CO2 in serpentine tube air cooler based on Fluent software. The flow characteristics of supercritical CO2 in a serpentine tube were mainly investigated. The heat transfer performance of the serpentine tube was analyzed by changing the operating pressure, the mass flow rate of CO2, and cooling water. The results show that the periodic reversal of centrifugal force in a serpentine tube will cause the temperature and velocity gradients to exhibit a periodic trend of internal and external interdiffusion; The closer the supercritical CO2 pressure is to the critical point, the higher the average heat transfer coefficient is. The average heat transfer coefficient at a pressure of 8 MPa is 24.37% and 42.53% higher than that at 9 MPa and 10 MPa, respectively. The average heat transfer coefficient of supercritical CO2 will increase with the increase of the CO2 mass flow rate, and decrease with the increase of the cooling water mass flow rate. The increase of the cooling water mass flow rate will not have an impact on the heat transfer coefficient of the peak point, but will advance the location of the peak point. The research results provide a theoretical basis for the design, operation and thermal efficiency improvement of the serpentine tube air cooler of supercritical CO2 heat pump, and have important guiding significance for the application of high efficiency heat exchangers

Numerical simulation of high-temperature phase transition thermal energy storage container for solar thermal power generation applications

The heat storage process of the high temperature thermal energy storage container using single-stage PCM for solar thermal power generation is numerically simulated. The change curves of the PCM's temperature and liquid rate over time during the single-stage thermal stage melting process and its cloud distributions of the liquid rate at different time have been obtained. Through the analysis of the curves and cloud figures, in the premise of ensuring the heat accumulation amount, three kinds of PCM cascade regenerative high temperature thermal energy storage container design schemes are derived and simulated on their regenerative performance. The result indicates that the cascade heat storage schemes greatly reduce the total heat storage time and the "dead zones" effects effectively on the performance of heat storage during the single-stage regenerative terminal stage, which can make the PCM liquid rate distribution to be more uniform. It provides the theoretical basis for the optimization design of the high temperature phase change thermal energy storage container for solar thermal power generation applications

Numerical simulation of cooling heat transfer of supercritical carbon dioxide in twisted elliptical tubes

In order to enhance the heat transfer performance of CO2 heat pump, based on the numerical simulation method of Fluent, the law of supercritical CO2 cooling and heat transfer characteristics and secondary flow in the horizontal elliptical tube whose torque is 100 mm or one infinity number under different mass flow are studied. In addition, concerning part coefficient of heat transfer and pressure drop brought by vertical elliptical tube, the influence of the length of the axial ratio b/a and the torque on the heat transfer performance is studied. Simulation results show that, the effect of buoyancy on the twisted elliptical tube is significantly larger than that of elliptical tube under low mass flow, and for the elliptical tube when supercritical CO2 is under the low mass flow G<200 kg/(m2·s2), the elliptical tube has a greater intensity of secondary flow caused by buoyancy, and the enhanced heat transfer is more pronounced; when supercritical CO2 is under the high mass flow G>200 kg/(m2·s2) , the twisted elliptical tube has a greater intensity of periodic secondary flow caused by self-structure, and the enhanced heat transfer is more pronounced; the heat transfer coefficient and pressure drop increase with the increasing degree of twist and flattening. It provides important theory and data support for the application of the twisted elliptical tube in CO2 heat pump

Research on heat transfer characteristics of eccentric

In order to explore the influence of eccentric structure on the heat transfer performance of carbon dioxide tubular the air cooler, the concentric rectangular spiral casing and eccentric rectangular spiral casing air cooler were established based on Fluent software, the temperature nephogram, velocity nephogram and specific heat capacity nephogram under the same operating conditions were compared, and the convective heat transfer coefficient, turbulent kinetic energy and pressure curve were analyzed. The numerical simulation results show that compared with the concentric casing air cooler, the cloud image of the eccentric casing air cooler is more skewed than that of the concentric structure, and the average convective heat transfer coefficient and turbulent kinetic energy increase by 12.99% and 15.38%, respectively, compared to the concentric structure. At the same time, the maximum pressure drop increases by 14.85%, and the overall heat transfer performance of the eccentric casing is better than that of the concentric casing. The eccentric sleeve type air cooler structure is superior to the concentric sleeve type, which provides scientific basis for the design, operation, and thermal efficiency improvement of rectangular spiral wound gas coolers in supercritical CO2 heat pumps, and has important practical significance for the application of high-efficiency heat exchangers

Numerical simulation of the fluid dynamics within the tissue engineering scaffolds micro-tubes

The core of tissue engineering is the fabrication of a complex three-dimensional space with cells and biomaterials. In the development of porous scaffolds in vitro, no matter the seed cells ran into the scaffold, or its excretion of waste discharged scaffolds, they both need the nutrient solution to be brought into or taken out. Therefore, the flow of the nutrient solution, cells and metabolic waste for the profitable living in vitro culture plays a significant role. the paper constructed bone scaffold models of different geometric parameters, analog cells, and nutrient solution flow conditions in the scaffolds using the FLUENT software. By making a contrastive analysis with the simulated result, the internal organizational design parameters of scaffold for tissue engineering is optimized and a certain amount of data and a theoretical basis for the internal bone scaffold structure design is provided

Study on heat transfer enhancing performance of spiral groove tube in phase change heat storage for solar energy

Based on the energy storage problems for solar energy utilization and the advantages of spiral groove tube heat exchanger, spiral groove tubes are used in the solar energy phase change heat storage, with numerical simulation of the thermal storage process of heat reservoir. Firstly, the simulation method and the reliability of the used model are verified experimentally with smooth tube. Using spiral groove tube as water flow pipe and phase change material as heat storage medium, building the three-dimensional model by Gambit software and meshing by ICEM, the heat storage process in the spiral groove tube and smooth tube heat storage are numerically simulated while the heat transfer enhancing effect is investigated. The influence of structural parameters such as groove pitch and groove depth on the heat storage process is simulated numerically and the influence rules are analyzed. The results show that the convective heat transfer intensity and heat transfer capability are enhanced when the smooth tubes are substituted by spiral groove tubes in the phase change heat storage and the heat storage time become shorter. In the range of simulation, the optimal structural parameters of spiral groove tube is that the groove pitch p=7 mm and groove depth e=0.4 mm. The further improved design of phase change thermal storage can be realized in later research in-depth

Numerical simulation of the fluid dynamics within the tissue engineering scaffolds micro-tubes

The core of tissue engineering is the fabrication of a complex three-dimensional space with cells and biomaterials. In the development of porous scaffolds in vitro, no matter the seed cells ran into the scaffold, or its excretion of waste discharged scaffolds, they both need the nutrient solution to be brought into or taken out. Therefore, the flow of the nutrient solution, cells and metabolic waste for the profitable living in vitro culture plays a significant role. the paper constructed bone scaffold models of different geometric parameters, analog cells, and nutrient solution flow conditions in the scaffolds using the FLUENT software. By making a contrastive analysis with the simulated result, the internal organizational design parameters of scaffold for tissue engineering is optimized and a certain amount of data and a theoretical basis for the internal bone scaffold structure design is provided

Invasive Eichhornia crassipes Affects the Capacity of Submerged Macrophytes to Utilize Nutrients

Invasion by free-floating species, such as Eichhornia crassipes, is one of the most critical threats to the biodiversity and sustainability of wetland ecosystems, where all plants experience spatial heterogeneity in substrate nutrients. However, few studies have focused on the effects of free-floating invaders on the capacity of submerged plants to utilize substrate nutrients. A 10-week greenhouse experiment was conducted to test the effects of free-floating invasive E. crassipes (presence or absence) on the growth of Ceratophyllum demersum and Myriophyllum spicatum, and their capacity to use heterogeneous and homogeneous substrate nutrients. We found that the invasion of E. crassipes could significantly decrease the growth of both submerged C. demersum and M. spicatum and that substrate nutrient heterogeneity increased the growth of C. demersum (approximately 30% in total biomass and 40% in the number of nodes) but not of M. spicatum. The two submerged species have different strategies to address invasion by E. crassipes. These results indicate that E. crassipes can prevent the growth of submerged plants even if the submerged plants can effectively use heterogeneous nutrients. For the effective conservation of submerged macrophytes in wetlands, measures should be taken to restrict the spread of invasive free-floating species