Performance assessment of hybrid desiccant cooling system at various climates
In our work, operation of hybrid desiccant cooling system (HDCS) has been investigated based on experimental studies. Different climates have been created by changing the temperature and humidity of HDCS inlet air, using an electrical heater and a centrifuge humidifier. Input energies, temperature of various points, and their relative humidity have been measured at the created climates. Coefficient of performance (COP), thermal coefficient of performance, and electrical coefficient of performance (ECOP) of the HDCS have been calculated. As a reference situation, vapor compression system (VCS) was examined at the same condition as HDCS. Results show that COP of HDCS in comparison with VCS decreased about 36% and 28% in hot-dry and hot-humid climates, respectively, which is due to the thermal energy consumption in HDCS. In contrast its ECOP increased, which means that by using HDCS some electrical energy would be saved. Defining operating cost index (OCI) parameter, operation costs of VCS and HDCS have been compared. Analyzing the OCI results shows that in HDCS, although decreasing the electricity consumption results in more usage of natural gas, these systems are economical especially in those countries with low natural gas prices.
Energy approach analysis of desiccant wheel operation
This paper focuses on desiccant wheel (DW) energy analysis. Numerical modeling is developed for the DW which is the key component of desiccant cooling systems. The mathematical model is validated by experimental results. In this paper, energy effectivenesses of DW are studied as well as energy consumption. An energy relation is developed and used to calculate DW power consumption, which is consisted of both DW drive power consumption and regeneration heat. Trends of energy effectivenesses of DW are presented in the various regeneration temperatures and DW speeds. An energy term is defined by dividing total power consumption to the adsorbed water rate and introduced as “specific adsorption energy (SAE)”. In addition to specific adsorption energy trends in the various regeneration temperatures and DW speeds, Genetic algorithm is used to find the minimmal point of SAE in the range of operating variables. The optimization results show that in the regeneration temperature of 61.9 $$^{\circ }$$∘C and rotation DW speed of 21.2 (Rph), minimmal SAE of DW is achieved.
Optimized Delivery System Achieves Enhanced Endomyocardial Stem Cell Retention
Background—Regenerative cell-based therapies are associated with limited myocardial retention of delivered stem cells. The objective of this study is to develop an endocardial delivery system for enhanced cell retention. Methods and Results—Stem cell retention was simulated in silico using 1- and 3-dimensional models of tissue distortion and compliance associated with delivery. Needle designs, predicted to be optimal, were accordingly engineered using nitinol, a nickel and titanium alloy displaying shape memory and superelasticity. Biocompatibility was tested with human mesenchymal stem cells. Experimental validation was performed with species-matched cells directly delivered into Langendorff-perfused porcine hearts or administered percutaneously into the endocardium of infarcted pigs. Cell retention was quantified by flow cytometry and real-time quantitative polymerase chain reaction methodology. Models, computing optimal distribution of distortion calibrated to favor tissue compliance, predicted that a 75°-curved needle featuring small-to-large graded side holes would ensure the highest cell retention profile. In isolated hearts, the nitinol curved needle catheter (C-Cath) design ensured 3-fold superior stem cell retention compared with a standard needle. In the setting of chronic infarction, percutaneous delivery of stem cells with C-Cath yielded a 37.7±7.1% versus 10.0±2.8% retention achieved with a traditional needle without effect on biocompatibility or safety. Conclusions—Modeling-guided development of a nitinol-based curved needle delivery system with incremental side holes achieved enhanced myocardial stem cell retention.