A simplified model for analysis of heat and mass transfer between air stream and flowing down water film in counter-flow plate heat exchanger which serves as an indirect evaporative cooler is theoretically analyzed in...A simplified model for analysis of heat and mass transfer between air stream and flowing down water film in counter-flow plate heat exchanger which serves as an indirect evaporative cooler is theoretically analyzed in this paper. Indirect evaporative cooler is used for sensible cooling of air which then is used for air conditioning purposes. Mathematical model was developed allowing determining heat transfer surface, outlet air temperature and specific humidity of the air being cooled. To make the model simpler some simplifications have been incorporated. The model has high level of correctness and can be used to calculate and design different types of evaporative heat exchangers. Analysis of results of calculations by the help of the developed model prove that the surface of heat exchanger depends on the thickness of water film layer by the regularity of direct proportionality. Moreover, increasing of the water film thickness brings to the decreasing of the efficiency of evaporative type heat exchanger. The model can be used for correct calculation and design of an evaporative cooling air conditioning systems.展开更多
Background Thalassemic patients demonstrate an increased rate of extracardiae vascular complications and increased carotid wall intima-media thickness （cIMT）, but very low prevalence of coronary artery disease （CAD...Background Thalassemic patients demonstrate an increased rate of extracardiae vascular complications and increased carotid wall intima-media thickness （cIMT）, but very low prevalence of coronary artery disease （CAD）. We investigated the atheroma burden by assessing the coronary artery calcium （CAC） and elMT in these patients. Methods We examined 37 patients with β-thalassemia and 150 healthy control volunteers with multi-detector computer tomography （CT） and ultrasonography to determine CAC score and cIMT, respectively. Results Propensity score matching （C-statistic： 0.88; 95% CI： 0.83-0.93） resulted in 27 pairs of patients; severe CAC was observed in 2 （7.4%） and 0 of β-thalassemia patients and healthy volunteers respectively （P = 0.5）. Median calcium score was 0 （0-0） in β-thalassemia patients and 0 （0-4） in healthy volunteers （P = 0.8）. Median intima-media thickness was higher in β-thalassemia patients compared to control group [0.45 （0.06-0.65） vs. 0.062 （0.054-0.086）; P = 0.04]. Conclusions Patients with β-thalassemia in comparison with healthy control subjects exhibit similar CAC score and increased cIMT. Our findings indicate a disparate rate of progression of atherosclerosis between coronary and extracardiac arteries in these patients lending support to the epidemiological evidence.展开更多
文摘A simplified model for analysis of heat and mass transfer between air stream and flowing down water film in counter-flow plate heat exchanger which serves as an indirect evaporative cooler is theoretically analyzed in this paper. Indirect evaporative cooler is used for sensible cooling of air which then is used for air conditioning purposes. Mathematical model was developed allowing determining heat transfer surface, outlet air temperature and specific humidity of the air being cooled. To make the model simpler some simplifications have been incorporated. The model has high level of correctness and can be used to calculate and design different types of evaporative heat exchangers. Analysis of results of calculations by the help of the developed model prove that the surface of heat exchanger depends on the thickness of water film layer by the regularity of direct proportionality. Moreover, increasing of the water film thickness brings to the decreasing of the efficiency of evaporative type heat exchanger. The model can be used for correct calculation and design of an evaporative cooling air conditioning systems.
文摘Background Thalassemic patients demonstrate an increased rate of extracardiae vascular complications and increased carotid wall intima-media thickness （cIMT）, but very low prevalence of coronary artery disease （CAD）. We investigated the atheroma burden by assessing the coronary artery calcium （CAC） and elMT in these patients. Methods We examined 37 patients with β-thalassemia and 150 healthy control volunteers with multi-detector computer tomography （CT） and ultrasonography to determine CAC score and cIMT, respectively. Results Propensity score matching （C-statistic： 0.88; 95% CI： 0.83-0.93） resulted in 27 pairs of patients; severe CAC was observed in 2 （7.4%） and 0 of β-thalassemia patients and healthy volunteers respectively （P = 0.5）. Median calcium score was 0 （0-0） in β-thalassemia patients and 0 （0-4） in healthy volunteers （P = 0.8）. Median intima-media thickness was higher in β-thalassemia patients compared to control group [0.45 （0.06-0.65） vs. 0.062 （0.054-0.086）; P = 0.04]. Conclusions Patients with β-thalassemia in comparison with healthy control subjects exhibit similar CAC score and increased cIMT. Our findings indicate a disparate rate of progression of atherosclerosis between coronary and extracardiac arteries in these patients lending support to the epidemiological evidence.
