PERFORMANCE IMPROVEMENT OF DOUBLE PIPE HEAT EXCHANGER BY USING TURBULATOR
The various techniques for achieving improved heat transfer are usually referred to as “heat transfer augmentation” or “heat transfer enhancement” and the heat exchanger provided with heat transfer enhancement techniques as “Augmented Heat Exchanger”. The objective is to reduce as many of the factors as possible: Capital Cost, Power Cost, Maintenance Cost, Space and Weight, Consistent with safety and reliability. Present work describes the principal techniques of industrial importance for the augmentation of single phase heat transfer on the inside of tubes namely twisted tapes. So twisted tape should be used in heat exchanger when high heat transfer rate is required and pressure drop is of no significance.
Heat Transfer Enhancement in Concentric Tube Heat Exchanger in ANSYS FLUENT 14 . 5
The study deals with CFD simulation of concentric tube heat exchanger and concentric tube heat exchanger with insert used for heating air using ANSYS FLUENT Software for steel. Design process for heat exchanger and insert has been carried out in SOLIDWORKS, fluid domain is formed in ANSYS workbench, followed by meshing in default mesh tool of ANSYS and solution is developed using ANSYS FLUENT software as FINITE ELEMENT TOOL and the results are compared between the two designs for parallel flow. The Reynolds number of air varied from 21000 to 100000. Inlet temperature of hot water and cold air are 60̊ C and 26̊ C respectively. The work included the determination of Nusselt number, heat transfer coefficient and pressure drop for insert in parallel flow.
CLINICAL TRIALS OF THE ABDOMINAL LEFT VENTRICULAR ASSIST DEVICE (ALVAD): PROGRESS REPORT.
An abdominal left ventricular assist device (ALVAD) is undergoing controlled clinical trials in our institution. The ALVAD is pneumatically-actuated, synchronously or asynchronously with an external console and is interposed between the apex of the left ventricle and the infrarenal abdominal aorta. It is an order of magnitude more effective than conventional intraaortic balloon pumping. Thus far, we have implanted this pump in 21 patients (15 males and six females). The average age has been 50. The duration of cardiopulmonary bypass with intensive pharmacologic support and IABP until ALVAD implantation has been nearly 4 hours. The plasma hemoglobins prior to ALVAD implantation have averaged 168 mg%. The platelet counts at implantation have averaged 68,000 mm(3). The average duration of ALVAD support has been in excess of one day and the longest trial extended for one week. We have been able to remove the pump after ventricular recovery in two instances and effected cardiac allografting in one instance of ALVAD dependency. We have found that (1) the profoundly depressed left (and right) ventricles can recover if totally supported with this device; (2) the device can function in the presence of ventricular fibrillation and/or standstill; (3) the device can effectively replace both left and right ventricular function in the presence of normal pulmonary vascular resistance and microcirculatory hemodynamics; and (4) in the presence of impending multiple organ failure, procrastination in use is to be avoided.