Solar energy is an important form of renewable energy that can be used as an alternative to fossil fuels. It can be used to produce electricity or to provide heat. One particular application is using solar energy for a domestic hot water system. The purpose of this research is to improve the thermal performance of a solar domestic hot water (SDHW) system. Experimental research was conducted to study the thermal performance of a shell-and-3coil heat exchanger and a shell-and-4coil heat exchanger using either water or glycol as working fluids on the tube side. An experimental set-up simulating a SDHW system was designed and constructed. The set-up contained a 270 L storage tank, a shell-and-three coil heat exchanger or a shell-and-four coil heat exchanger, and electrical heaters to simulate the solar collector. At the inlets and outlets of the storage tank and the heat exchanger the temperatures, pressures, and flow rates were measured to determine the thermal performance. The results from the experiment tests were analyzed in terms of the overall heat transfer coefficient product (UA) and the pressure drop (?P) between the inlet and outlet of the heat exchanger. The UA value of the shell-and-4coil heat exchanger was higher than the UA value of the shell-and-3coil heat exchanger. For example, at a heat transfer rate of 2000 W for water, the UA values were 240 W/K and 270 W/K for the shell-and-3coil heat exchanger and the shell-and-4coil heat exchanger, respectively. With respect to glycol, at a heat transfer rate of 2000 W the UA values were 197 W/K and 215 W/K for shell-and-3coil, and shell-and-4coil heat exchanger, respectively. The degradation of the thermal performance of the shell-and-3coil was offset by benefits, such as reduction in mass, volume, labor cost and the final cost. A reasonable agreement between theoretical and experimental results in terms of the UA value was observed. The thermal performance of each coil in both heat exchangers was below that predicted by the relevant heat transfer correlations. A performance factor was calculated for each coil. For both glycol and water, and both heat exchangers, the performance factors for the inner most and outer most coils were 0.70 and 0.53, respectively. However, there is a slight difference in the performance factors of coils between the inner most and the outer most coils for the 3-coil and 4-coil heat exchangers. For these coils the performance factors varied from 0.55 to 0.67.

No description available.

In adult cardiomyocytes, the established mechanism of excitation-contraction coupling is calcium-induced calcium release (CICR) mediated by L-type Ca2+ channels (Cav1.2). Briefly, membrane depolarization opens voltage-gated Cav1.2 to allow for the influx of extracellular Ca2+ into the cytosol. This small sarcolemmal (SL) Ca2+ influx is necessary for triggering a larger release of Ca2+ from the intracellular Ca2+ storage site, the sarcoplasmic reticulum (SR), through the SR Ca2+ release channel also known as the ryanodine receptor (RyR). RyR-mediated release of SR Ca2+ effectively raises the cytosolic free Ca2+ concentration, allowing for Ca2+ binding to troponin C on the troponin-tropomysin complex, leading to cross-bridge formation and cell contraction. However, previous functional data suggests an additional CICR modality involving reverse mode Na+-Ca2+ exchanger (NCX) activity also exists in neonate cardiomyocytes. To further our understanding of how CICR changes occur during development, we investigated the spatial arrangement of caveolin-3 (cav-3), the principle structural protein of small membrane invaginations named caveolae, and NCX in developing rabbit ventricular myocytes. Using traditional as well as novel image processing and analysis techniques, both qualitative and quantitative findings firmly establish the highly robust and organized nature of NCX and cav-3 distributions during development. Specifically, our results show that NCX and cav-3 are distributed on the peripheral membrane as discrete clusters and are not highly colocalized throughout development. 3D distance analysis revealed that NCX and cav-3 clusters are organized with a distinct longitudinal and transverse periodicity of 1-1.5 μm and that NCX and cav-3 cluster have a pronounced tendency to be mutually exclusive on the cell periphery. Although these findings do not support the original hypothesis that caveolae is the structuring element for a restricted microdomain facilitating NCX-CICR, our results cannot rule out the existence of such microdomain organized by other anchoring proteins. The developmentally stable distributions of NCX and cav-3 imply that the observed developmental CICR changes are achieved by the spatial re-organization of other protein partners of NCX or non-spatial modifications. In addition, the newly developed image processing and analysis techniques can have wide applicability to the investigations on the spatial distribution of other proteins and cellular structures.

AN ABSTRACT OF THE THESIS OF Daniel Grohmann, for the Master of Science degree in Mechanical Engineering on May 5, 2014, at Southern Illinois University Carbondale DESIGN AND CHARACTERIZATION OF A COMPACT HEAT EXCHANGER FOR USE WITH NANOFLUIDS Major Professor: Dr. Kanchan Mondal This research is aimed to design and characterize an experimental plain channel, plate heat exchanger and further compare the performance of water based nanofluids as with that of water. The thesis discusses the designing and fabrication of the heat exchanger such that several parameters such as temperature, flow rate, nanoparticle concentration, and length of channels can be varied. Three sizes of heat exchangers were fabricated. Experiments were conducted to remove heat from air at different temperatures by the various heat exchanger fluids, namely water, 0.5, 0.75 and 1 vol.% alumina in water. Flow rates of the cold fluid were varied in order to change the Reynolds Number while maintaining a laminar regime. In the experiments with water as the heat exchanger fluid, it was found that the heat exchange did not follow pure counter current flow conditions presumably due to end effects. A correction factor, F, for the log mean temperature difference value was calculated for each case to estimate the mean temperature difference. The effectiveness values were found to be greater than 0.75 for most cases. It was also found that the thermal entrance length was larger than the length of the channels for the shortest heat exchanger. In addition, it was observed that the laminar regime Nusselt number values were similar to values reported in literature for flow through mini and micro channels. Convective heat transfer coefficients were calculated and were found to be of the order of those reported for water. It was also discovered that Prandtl number was the most influential property for this study. As opposed to expectations, the use of nanofluids was found that it did not significantly improve heat transfer than that of the water alone. The only case that the nanofluids had a significant enhancement in the performance was that of the 6in plate at 1 vol.% of 11% increase. The rest of the study showed that it had no increase or negative effects.

No description available.

Master of Science / Department of Mechanical and Nuclear Engineering / Akira T. Tokuhiro / In the STAR-LM (Secure Transportable Autonomous Reactor-Liquid Metal) reactor concept developed at Argonne National Laboratory (ANL), a supercritical CO2 (S-CO2) Brayton cycle is used as the power conversion system because it features advantages such as a higher efficiency due to less compressive work, and competitive cost due to a reduced complexity and size. From the components of the cycle, high performance of both the recuperator and precooler has a large influence on the overall cycle efficiency and plant economy. One attractive option for optimizing the performance of the cycle is to use an high efficiency heat exchanger such as the Printed Circuit Heat Exchanger (PCHE) manufactured by Heatric. The PCHE is a compact heat exchanger with high effectiveness, wide operating range, enhanced safety, and low cost. PCHEs are used in various industrial applications, but are relatively new to the nuclear industry. In this study, performance testing of a PCHE using supercritical CO2 and water as heat transfer media were performed at ANL. The heat transfer characteristics of the PCHE under operating conditions of the STAR_LM precooler were investigated. The S-CO2 , defined the “hot-side”, had its outlet condition near the pseudocritical point at 7.5MPa (~31-32 C). We found that of all the thermophysical properties undergoing rapid change near the critical point, heat transfer for S-CO2 is strongly correlated with the specific heat of CO2. Additional experiments performed with different bulk temperatures and pressures on the hot side also supported this conclusion. We proposed plotting the heat transfer results, (Nu2 + Pr2/3) versus (RePr4/3), based on an order-of-magnitude analysis, to reveal the close proximity of the outlet to pseudocritical conditions. In order to check the experimental results, a nodal model of a segmented PCHE using a traditional log-mean temperature difference method was developed. This approach provided the temperature distribution along the heat exchanger. Additionally a CFD simulation (FLUENT) of a 4-layer, zig-zag channeled PCHE was developed. Comparison of the simulation and LMTD nodal model revealed that indeed specific heat strongly influenced the heat transfer.

In adult cardiomyocytes, the established mechanism of excitation-contraction coupling is calcium-induced calcium release (CICR) mediated by L-type Ca2+ channels (Cav1.2). Briefly, membrane depolarization opens voltage-gated Cav1.2 to allow for the influx of extracellular Ca2+ into the cytosol. This small sarcolemmal (SL) Ca2+ influx is necessary for triggering a larger release of Ca2+ from the intracellular Ca2+ storage site, the sarcoplasmic reticulum (SR), through the SR Ca2+ release channel also known as the ryanodine receptor (RyR). RyR-mediated release of SR Ca2+ effectively raises the cytosolic free Ca2+ concentration, allowing for Ca2+ binding to troponin C on the troponin-tropomysin complex, leading to cross-bridge formation and cell contraction. However, previous functional data suggests an additional CICR modality involving reverse mode Na+-Ca2+ exchanger (NCX) activity also exists in neonate cardiomyocytes. To further our understanding of how CICR changes occur during development, we investigated the spatial arrangement of caveolin-3 (cav-3), the principle structural protein of small membrane invaginations named caveolae, and NCX in developing rabbit ventricular myocytes. Using traditional as well as novel image processing and analysis techniques, both qualitative and quantitative findings firmly establish the highly robust and organized nature of NCX and cav-3 distributions during development. Specifically, our results show that NCX and cav-3 are distributed on the peripheral membrane as discrete clusters and are not highly colocalized throughout development. 3D distance analysis revealed that NCX and cav-3 clusters are organized with a distinct longitudinal and transverse periodicity of 1-1.5 μm and that NCX and cav-3 cluster have a pronounced tendency to be mutually exclusive on the cell periphery. Although these findings do not support the original hypothesis that caveolae is the structuring element for a restricted microdomain facilitating NCX-CICR, our results cannot rule out the existence of such microdomain organized by other anchoring proteins. The developmentally stable distributions of NCX and cav-3 imply that the observed developmental CICR changes are achieved by the spatial re-organization of other protein partners of NCX or non-spatial modifications. In addition, the newly developed image processing and analysis techniques can have wide applicability to the investigations on the spatial distribution of other proteins and cellular structures. / Medicine, Faculty of / Pathology and Laboratory Medicine, Department of / Graduate

No description available.

Extruded Al-Mn alloy are used in heat exchanger applications due to their light weight and good thermal conductivity. Depending on the application, the units may be subjected to external corrosion, which can lead to perforation of the tube. The industrial test most commonly used to assess heat exchanger alloys is the seawater acetic acid test (SWAAT). This is a cyclic fog at 40°C and pH 2.9. In the present study, it was found that pits developing in extruded Al-Mn tubes during the SWAAT test are purely crystallographic. Furthermore, a mechanistic understanding for crystallographic pitting has been developed. The SWAAT test can be of relatively long duration and, typically, does not yield information on the underlying corrosion initiation and propagation mechanisms. In the present study, alternate methods to assess pitting corrosion were elaborated. A drop testing procedure has been successfully implemented to study the mechanism of pit initiation. It was revealed that pits initiated within the aluminium matrix in the vicinity of grain boundaries. A close link between large second-phase particles and pit initiation was established. No preferred grain orientation for pit initiation was evident. Scanning electron microscopy and associated tomography were undertaken for the first time to clarify the mechanism of pit propagation. The pit walls were oriented {100}, while the fast-dissolving planes were {110} and {111}. The findings were in accordance with previous literature. Corrosion penetrated deeper into the alloy when the corrosion front was close to a grain boundary. Pit walls were cathodic to the aluminium matrix, possibly due to enrichment of alloying elements at pit walls. The effect of alloy additions on the corrosion behaviour of extruded aluminium alloys was investigated. Alloys with varying copper, iron and manganese contents were compared. Shot noise analysis and post-mortem analyses were undertaken. The increased amount of manganese in solid solution delayed the transition from micropits to stable pitting. This delay is attributable to second-phase particles that are less cathodic to the aluminium matrix in alloys with increased manganese content. Increasing copper decreased the size of the dissolved polyhedra during stable pitting. Furthermore, pits propagated faster in alloys rich in copper. This could be attributed to an increased level of copper enrichment at the pit walls. Finally, more second-phase particles were present in alloys with increased iron levels. Additionally, pits located in those alloys propagated deeper than pits located in alloys with low levels of iron. A competition between two different types of cathodes, enrichment layer and second-phase particles, is suggested. In conclusion, the effect of microstructure and alloy additions on the corrosion mechanism for crystallographic pitting developed during the project was clarified.

In this study, the techno-economic feasibility of converting an existing process steam plant into a combined heat and power plant, using an external solar thermal field as the additional heat source was studied. Technical feasibility entailed designing a suitable heat exchanger, which uses hot oil from the solar field to raise the steam conditions from dry saturated to superheated. The solar field was sized to heat a selected heat transfer fluid to its maximum attainable temperature. A suitable turbine-alternator was chosen which can meet the required plant power demand. For this to be a success, the processes which require process steam were analysed and a MathCAD model was created to design the heat exchanger and check turbine output using the equations adapted from various thermodynamics and power plant engineering texts, together with the Standards for the Tubular Exchanger Manufacturer's Association. The U.S. National Renewable Energy Laboratory system advisor model was used to size the suitable solar field. A financial model was developed in Excel to check the economic feasibility of the project, using discounted payback period as the economic indicator. It was found out that amongst loan interest rates, variation of system output and the electricity output, the profitability of the project was largely influenced by the electricity tariff. An optimum size for the heat exchanger of 30ft was established from the sensitivity analysis and it was concluded that the project is currently not economically viable on an independent investor financing model, unless either the electricity tariff improves or the solar thermal energy and turbine technology costs decrease.