Thermo-Fluid Characteristics of High Temperature Molten Salt Flowing in Single-Leaf Type Hollow Paddles

A single-leaf type paddle heat exchanger with molten salt as the working fluid is a proper option in high temperature heating processes of materials. In this paper, based on computational fluid dynamics (CFD) simulations, we present the thermo-fluid characteristics of high temperature molten salt flowing in single-leaf type hollow paddles in the view of both the first law and the second law of thermodynamics. The results show that the heat transfer rate of the hollow paddles is significantly greater than that of solid paddles. The penalty of the heat transfer enhancement is additional pressure drop and larger total irreversibility (i.e., total entropy generation rate). Increasing the volume of the fluid space helps to enhance the heat transfer, but there exists an upper limit. Hollow paddles are more favorable in heat transfer enhancement for designs with a larger height of the paddles, flow rate of molten salt and material-side heat transfer coefficient. The diameter of the flow holes influences the pressure drop strongly, but their position is not important for heat transfer in the studied range. Other measures of modifying the fluid flow and heat transfer like internal baffles, more flow holes or multiple channels for small fluid volume are further discussed. For few baffles, their effects are limited. More flow holes reduce the pressure drop obviously. For the hollow paddles with small fluid volume, it is possible to increase the heat transfer rate with more fluid channels. The trade-off among fluid flow, heat transfer and mechanical strength is necessary. The thermo-fluid characteristics revealed in this paper will provide guidance for practical designs

Clinical characteristics and outcome of percutaneous coronary intervention in Yemeni patients

Background: Percutaneous coronary intervention (PCI) is increasingly used in the management of acute coronary syndromes (ACSs). PCI has decreased the demand for coronary artery bypass grafting, and more patients with ACS are now undergoing PCI. No previous data about the characteristics and outcome of patients performing PCI in Yemen. This study aimed to assess the patient presentation, characteristics, and outcome among Yemeni patients having PCI in the Military Cardiac Center. Methods: All patients who underwent PCI either primary or elective in the Military Cardiac Center in Sanaa City were included over 6 months. Clinical, demographic, procedural, and outcome data were extracted and analyzed. Results: During the study period, 250 patients underwent PCI. The mean ± standard deviation age was 57 ± 11 years, with 84% being male. Of all the patients, 61.6% (156) smoked tobacco, 56% (140) had hypertension, 37% (93) had Type 2 diabetes, 48.4% (121) had hyperlipidemia, and 8% (20) had a family history of ischemic heart disease. Coronary artery presentation was in the form of acute ST-elevation myocardial infarction at 41% (102), non-STEMI at 5.2% (58), stable angina at 31% (77), and unstable angina at 5.2% (13). Coronary artery interventions were elective PCI in 81% (203), emergency in 11% (27), and urgent in 8% (20) with only 3% radial artery access and 97% femoral access. PCI was mainly in the left anterior descending artery in 82% (179), right coronary artery in 41% (89), left circumflex artery in 23% (54), and left main in 1.25% (3). All stents were drug-eluting stents during the registry time. Complication occurred in 17.6% (44) and case fatality was 2% (5). Conclusions: Despite the current situation in Yemen, PCI was performed with success in a large number of patients with a low incidence of inhospital complications and mortality that is comparable to high- or middle-income settings