The present paper presents peak wall shear stresses and velocities in a bifurcated femoral artery. This artery is modeled along with blockage downstream of bifurcation, blockage at bifurcation, blockage downstream of stented femoral artery. The femoral artery is subjected to peripheral artery disease. A two-dimensional computational fluid dynamic analysis is conducted in all the models, assuming steady blood flow and seventy percent plaque. However, the blood viscosity and blood pressure vary in the femoral artery models as they are subjected to other medical conditions. Femoral artery bifurcates into profunda femoris and the bifurcation angles are assumed to vary at 30, 45 and 60 degrees. The blocked bifurcated artery is replaced with a wall stent and in many cases, a blockage develops downstream of the bifurcated stented artery as a consequence of stent implantation. The wall shear stresses and velocities results from the bifurcated and blocked femoral arterial models are compared to a normal artery characteristic. Further, a comparative study has been conducted along the blocked bifurcated artery with and without the stent.
Intravascular stents play a major role in restoring the patency in atherosclerotic coronary arteries. However restenosis occurs in an artery after certain period of time. In order to obtain the consequences of various problems associated with the implantation of stent in a multiple blocked artery, an analysis is done at the blockage of artery downstream the stented region. The present paper analyzes blood flow downstream of partially blocked stented artery at different levels of blockages. The blockage rate is taken as thirty, fifty and sixty percentage of the stented artery. Velocity, flow rate and pressure drop at the blocked artery are simulated using the CFD software. The analysis illustrates an increment in velocity and pressure drop at the blockage with increase in velocity, pressure and mass flow rate at the inlet. The maximum velocity of blood in stented arteries at high percentage of blockage is more when compared to the lower ones. Due to the increase in pressure at inlet, the mass flow rate increased at the blockage downstream stented artery. The values for pressure obtained at blockage are decreasing which are in contrast to the velocity and pressure drop values at the blockage. The pressure drop at the blockage analyzes the blood pressure level in the artery which can be used for future optimizations and modifications during and after the stent implantation.
Coiled tubes are designed to improve heat transfer performance and minimize pressure drops in compact heat exchangers. Heat loss is most common in heat exchangers and this heat is not often used. Waste heat recovery is an important pathway to more efficient technologies. In the present study, the heat energy that would normally be wasted in a heat exchanger is allowed to run through a thermoelectric generator prior to being introduced in the heat exchanger. This design allows the waste heat energy to be recovered by the thermoelectric generator, and the power generated is measured. A conical coil heat exchanger is built and the test set up is used to conduct experimental analysis at varying temperatures and flow rates. The obtained results are validated by comparing them to experimental results of a previous study. It is observed that with increase in flow rates, heat transfer coefficient increases and maximum effectiveness is obtained at lower flow rates. As the difference in fluid temperature increases, the thermoelectric generator produces more power.
This paper reviews the recent literature on the stent applications and their recent advancements due to some controversies. The paper consists of two parts flow modeling of stents and a comparison between normal and stenosed artery. It also includes a comparison of stent geometries to determine hemodynamically favorable stents. In spite of many advantages bare metal stents are found to be unfavorable. However the study of stents based on flow and design recommend stent coatings. In comparison with bare metal stents, metal coated stents proved to be more efficient in terms of restenosis. Most of the metal coatings have less fluoroscopic visibility and low tensile strengths and hence drug eluting stents were studied. Although drug eluting stents were proved to be efficient in controlling restenosis, they have issues in patients with co-morbidities. For this reason, polymer and carbon coatings were studied in detail which showed better results than drug eluting stents. Biodegradable stents on the other hand inhibit smooth muscle cell proliferation and a decrease in neointimal proliferation. At present research on polymer, carbon and biodegradable stents are actively pursued for stent therapy applications.
This research was conducted to determine the indoor air flow throughout a multistory educational building. Due to increase in enrollments every year, classrooms are fully occupied which resulted in insufficient air flow in the classroom causing discomfort. This paper details numerous calculations to determine whether the multistory educational building's Heat Ventilation and Air Conditioning (HVAC) system was up to code by assessing the total amount of Cooling load and airflow, measured in Cubic Feet per Minute (CFM), within the building. The Cooling Load Temperature Difference (CLTD) method is a traditional method used while designing buildings HVAC system. Hence, the present study was conducted using the CLTD method to estimate the total cooling load and airflow in the building during summer season. The theoretical calculations were compared to measured values which showed difference in the airflow and cooling loads. The cooling load calculations measured in summer provided a dynamic approach to varying load and climate. The parameters assessed in the study include outside and room temperature, geographic position of building, occupancy, equipment, ventilation, etc. Fluctuations were noticed in the assessed parameters which affected the calculated CLTD load and CFM values in each room. The measured data was collected from the building's HVAC system to ensure the system was meeting the required demand of the load during the cooling season. The theoretical and measured data were compared for the summer season which shows that the Cooling loads and airflow within the building does not meets the building code standards for small classrooms.
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