The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Marco Noro - One of the best experts on this subject based on the ideXlab platform.
-
photovoltaic thermal pv t ground dual source heat Pump optimum energy and economic sizing based on performance analysis
Energy and Buildings, 2020Co-Authors: Renato Lazzarin, Marco NoroAbstract:Abstract Dual or multisource heat Pumps were conceived to obviate to the defects of a single source, such as outside air, ground, water or solar radiation. Concerning the latter, the use of Photovoltaic/Thermal (PV/T or PVT) modules allows not only to partially recover the otherwise lost heat, but also to cool the PV and increase its electrical efficiency. Many studies simulated the possible behavior of combination of PVT with other sources, but generally unglazed PVT collectors were used. Only few results based on coupling glazed PVT to ground source heat Pumps are available in literature. The use of glazed PVT increases thermal efficiency of the collector, and the coupling of ground allows to keep the electrical efficiency at high values without the risk of cells damage due to overheating. A refurbished building located in Northern Italy will be equipped by a PVT dual source heat Pump, Operating with the ground as source/sink, whereas the PVT drives the heat Pump compressor and acts as a dual source. When the heat Pump does not need heat or operates for summer air conditioning, the ground is the heat sink both for the heat Pump and for the PVT cooling. A dynamic simulation allowed to size the plant and set up a suitable control logic of the main equipment. Very high efficiency and low primary energy consumption are demonstrated for the whole plant, thanks also to the high energy independency from the grid.
Ranjit John - One of the best experts on this subject based on the ideXlab platform.
-
effects of pulsatile and continuous flow left ventricular assist devices on left ventricular unloading
Journal of Heart and Lung Transplantation, 2008Co-Authors: Santiago Garcia, Forum Kandar, Andrew J Boyle, Monica Colvinadams, Kenneth Lliao, Lyle D Joyce, Ranjit JohnAbstract:Background In patients with end-stage heart failure, the use of left ventricular assist devices (LVADs) has improved clinical outcomes. Although newer continuous-flow devices have significant advantages, the effect of continuous flow on left ventricular unloading and hemodynamics is less well established. The aim of this investigation was to compare the effects of pulsatile- vs continuous-flow LVADs on left ventricular reverse remodeling and hemodynamic indices. Methods Thirty-five patients undergoing implantation with a pulsatile volume displacement Pump Operating at fixed speed ( n = 15; HeartMate XVE; Thoratec Corp., Pleasanton, CA) or a continuous-flow rotary Pump with an axial design Operating at a fixed rotor speed ( n = 20; HeartMate II; Thoratec) were evaluated. Right heart catheterization and echocardiography were performed pre-operatively, and at 1- and 6-month follow-up intervals. Results Thirty-five of 40 eligible patients with end-stage heart failure were included in this study. When used at fixed speed, use of both devices led to a substantial reduction in left ventricular volumes and dimensions at 1 month ( p p p -values not statistically significant). Conclusions Substantial left ventricular unloading and hemodynamic improvement is achieved with the HeartMate XVE and the HeartMate II. We conclude that continuous-flow LVADs are as effective as pulsatile-flow LVADs with regard to degree of left ventricular unloading and cardiac hemodynamics.
Nigel H Lovell - One of the best experts on this subject based on the ideXlab platform.
-
parameter optimized model of cardiovascular rotary blood Pump interactions
IEEE Transactions on Biomedical Engineering, 2010Co-Authors: Einly Lim, Socrates Dokos, Shaun L Cloherty, Robert F Salamonsen, D G Mason, J A Reizes, Nigel H LovellAbstract:A lumped parameter model of human cardiovascular-implantable rotary blood Pump (iRBP) interaction has been developed based on experimental data recorded in two healthy pigs with the iRBP in situ. The model includes descriptions of the left and right heart, direct ventricular interaction through the septum and pericardium, the systemic and pulmonary circulations, as well as the iRBP. A subset of parameters was optimized in a least squares sense to faithfully reproduce the experimental measurements (pressures, flows and Pump variables). Our fitted model compares favorably with our experimental measurements at a range of Pump Operating points. Furthermore, we have also suggested the importance of various model features, such as the curvilinearity of the end systolic pressure-volume relationship, the Starling resistance, the suction resistance, the effect of respiration, as well as the influence of the Pump inflow and outflow cannulae. Alterations of model parameters were done to investigate the circulatory response to rotary blood Pump assistance under heart failure conditions. The present model provides a valuable tool for experiment designs, as well as a platform to aid in the development and evaluation of robust physiological Pump control algorithms.
-
Noninvasive Average Flow and Differential Pressure Estimation for an Implantable Rotary Blood Pump Using Dimensional Analysis
IEEE Transactions on Biomedical Engineering, 2008Co-Authors: Einly Lim, Shaun L Cloherty, J A Reizes, Dean M Karantonis, David G. Mason, Nigel H LovellAbstract:Accurate noninvasive average flow and differential pressure estimation of implantable rotary blood Pumps (IRBPs) is an important practical element for their physiological control. While most attempts at developing flow and differential pressure estimate models have involved purely empirical techniques, dimensional analysis utilizes theoretical principles of fluid mechanics that provides valuable insights into parameter relationships. Based on data obtained from a steady flow mock loop under a wide range of Pump Operating points and fluid viscosities, flow and differential pressure estimate models were thus obtained using dimensional analysis. The algorithm was then validated using data from two other VentrAssist IRBPs. Linear correlations between estimated and measured Pump flow over a flow range of 0.5 to 8.0 L/min resulted in a slope of 0.98 (R 2 = 0.9848). The average flow error was 0.20 plusmn 0.14 L/min (mean plusmn standard deviation) and the average percentage error was 5.79%. Similarly, linear correlations between estimated and measured Pump differential pressure resulted in a slope of 1.027 (R 2 = 0.997) over a pressure range of 60 to 180 mmHg. The average differential pressure error was 1.84 plusmn 1.54 mmHg and the average percentage error was 1.51%.
-
noninvasive average flow estimation for an implantable rotary blood Pump a new algorithm incorporating the role of blood viscosity
Artificial Organs, 2007Co-Authors: Nicolo Malagutti, Shaun L Cloherty, Robert F Salamonsen, D G Mason, Dean M Karantonis, Peter J Ayre, Nigel H LovellAbstract:The effect of blood hematocrit (HCT) on a noninvasive flow estimation algorithm was examined in a centrifugal implantable rotary blood Pump (iRBP) used for ventricular assistance. An average flow estimator, based on three parameters, input electrical power, Pump speed, and HCT, was developed. Data were collected in a mock loop under steady flow conditions for a variety of Pump Operating points and for various HCT levels. Analysis was performed using three-dimensional polynomial surfaces to fit the collected data for each different HCT level. The polynomial coefficients of the surfaces were then analyzed as a function of HCT. Linear correlations between estimated and measured Pump flow over a flow range from 1.0 to 7.5 L/min resulted in a slope of 1.024 L/min (R2=0.9805). Early patient data tested against the estimator have shown promising consistency, suggesting that consideration of HCT can improve the accuracy of existing flow estimation algorithms.
Kim D Pressnail - One of the best experts on this subject based on the ideXlab platform.
-
evaluating a proposed retrofit measure for a multi unit residential building which uses an air source heat Pump Operating in an enclosed balcony space
Energy and Buildings, 2014Co-Authors: Marianne F Touchie, Kim D PressnailAbstract:Abstract To improve the energy performance of Toronto's post-war multi-unit residential buildings (MURBs), these buildings must be energy retrofitted. Here, a novel energy retrofit strategy employing air-source heat Pumps (ASHPs) Operating in enclosed balcony spaces is assessed. The enclosed balcony provides a thermal buffer zone (TBZ) which can improve the coefficient of performance of the ASHP compared to typical exterior operation by accessing captured solar gains. The estimated energy savings associated with implementing this retrofit strategy was determined using a hybrid modeling approach. A calibrated energy model of a 1968 MURB represented the base case energy consumption. Then, a supplementary algorithm, developed based on laboratory testing, was used to determine the quantity of energy that could be extracted from the TBZ and delivered to the north- and south-facing suites as well as to hot water storage. The modeling exercise yielded estimated whole-building energy and greenhouse gas emissions savings of 39% and 45%, respectively. Due to utility prices at the time of writing, the energy cost savings do not present a compelling financial case. However, the qualitative benefits of this retrofit strategy include suite-based control for occupants and the ability to sub-meter space heating energy use at the suite-level.
-
testing and simulation of a low temperature air source heat Pump Operating in a thermal buffer zone
Energy and Buildings, 2014Co-Authors: Marianne F Touchie, Kim D PressnailAbstract:Abstract Air-source heat Pumps (ASHPs) are commonly used in temperate climates throughout Europe and Asia to provide energy efficient heating and cooling. However, ASHPs have not been widely adopted for heating in colder climates because the coefficient of performance (COP) is lower when outdoor temperatures are colder. While many researchers are working on improving the cold-temperature performance of ASHPs by altering the design of the equipment, this work examines an innovative way to improve performance by Operating an existing ‘off-the-shelf’ ASHP within a thermal buffer zone. This paper shows that Operating an ASHP in a thermal buffer zone (TBZ) created by an enclosed balcony space can improve the COP in cold temperatures. An ASHP Operating in a TBZ was tested in a climate chamber where the performance was monitored under a variety of climatic conditions. The temperature drawdown of the TBZ and the associated impact on the COP were observed. The TBZ solar heat gain rates required to improve the COP were identified for a range of exterior temperatures. Then, a suite-based energy model was developed and calibrated to simulate the performance of the ASHP Operating in the TBZ. The model provided a reasonable prediction of the ASHP performance below 10 °C.
Francis D. Pagani - One of the best experts on this subject based on the ideXlab platform.
-
hemodynamic and exercise performance with pulsatile and continuous flow left ventricular assist devices
Circulation, 2007Co-Authors: Jonathan W Haft, William F Armstrong, D B Dyke, Keith D Aaronson, Todd M Koelling, David J Farrar, Francis D. PaganiAbstract:Background— Continuous-flow rotary Pumps with axial design are increasingly used for left ventricular assist support. The efficacy of this design compared with pulsatile, volume displacement Pumps, with respect to characteristics of left ventricular unloading, and exercise performance remains largely unstudied. Methods and Results— Thirty-four patients undergoing implantation with a pulsatile, volume displacement Pump Operating in a full-to-empty cycle (HeartMate XVE; Thoratec Inc, Pleasanton, Calif; n=16) or continuous-flow rotary Pump with an axial design Operating at a fixed rotor speed (HeartMate II; Thoratec Inc; n=18) were evaluated with right heart catheterization and echocardiography preoperatively and at 3 months postoperatively and cardiopulmonary exercise testing 3 months postoperatively. Support with either the XVE or II resulted in significant ( P 2 −XVE: 46.8±10.2 versus II: 49.1±13.6). Echocardiography at 3 months demonstrated a significantly ( P Conclusions— The HeartMate XVE or II provided equivalent degrees of hemodynamic support and exercise capacity. The XVE was associated with greater left ventricular volume unloading. Characteristics of left ventricular pressure and volume unloading between these Pump designs and mode of operation do not influence early exercise performance.
