STEADY STATE MODELING AND OPTIMIZATION FOR PERFORMANCE AND ENVIRONMENTAL IMPACT OF ADVANCED VAPOR COMPRESSION SYSTEMS

The use of heating, ventilation, air conditioning, and refrigeration (HVACR) systems is always increasing. This is because the HVACR systems are necessary for food production and ability to inhabit buildings that otherwise would be inhabitable. The basic vapor compression (VC) cycle which is still the main underlying HVACR technology worldwide, has already reached its limits and researchers are investigating more creative and complex cycles to improve capacity and efficiency. This motivates the development of a generalized vapor compression system simulation platform. This thesis presents a comprehensive vapor compression system steady state solver which has several novel features compared to the existing solvers. Firstly, this solver is capable of simulating large number of different vapor compression system designs. This includes system configurations comprising more than 500 components, multiple air and refrigerant paths, and user defined refrigerants. Also, the solver uses a component-based solution scheme in which the component models are treated as black box objects. This allows a system engineer to quickly assemble and simulate a system where-in the component models and performance data comes from disparate sources. This allows different vapor compression systems design engineers, and manufacturers to use the solver without the need to expose the underlying component model complexities. We validate the solver using a residential air source heat pump system, a vapor injection heat pump system with a flash tank, and a CO2 two-stage supermarket refrigeration system with mechanical subcooler. Moreover, designing a HVACR system while primarily considering its environmental impact requires an evaluation of the system's overall environmental impact as a function of its design parameters. The most comprehensive metric proposed for this evaluation is the system's Life Cycle Climate Performance (LCCP). Hence, this thesis presents an open-source and modular framework for LCCP based design of vapor compression systems. This framework can be used for, not only evaluation, but also LCCP-based design and optimization of vapor compression systems to minimize the environmental impact of such systems. Furthermore, the framework provides insights into various other challenges such as selection of appropriate systems for various climates and the choice of next generation lower global warming potential (GWP) refrigerants

Optimization of a Residential Air Source Heat Pump using Heat Exchangers with Small Diameter Tubes

Heat exchangers play significant role in refrigeration and air conditioning systems. Ongoing research aims to improve, or at least maintain, the system performance while reducing the size, weight and cost of the heat exchangers. This in turn leads to lower system refrigerant charge and reduced environmental impact. Using heat exchangers with small tube diameters (less than 5 mm) instead of large tube diameters has been shown to be a promising solution to meet the aforementioned goals. However, shifting towards mall tube diameters requires in-depth analysis and optimization of several heat exchanger design parameters. This paper presents a multi-objective optimization of a residential air source heat pump system using genetic algorithms with a particular focus on the use of small diameter tubes in the heat exchangers. The objectives are to minimize the heat exchangers’ cost and maximize the system performance. The goal of this study is to determine the potential material savings and cost reduction when using tube diameters between 3 mm and 5 mm in the heat exchangers. In addition to the tube diameters, multiple fin types, tube spacing and fin densities are also investigated. The optimization is carried out for R-410A, and a lower-GWP alternative, R-32. The system utilizing the improved heat exchanger designs has a cost reduction of 50% in comparison to the baseline system. Also, the improvements in the system’s COP and the system charge reduction are around 20% and 35%, respectively.

Steady State Modeling of Advanced Vapor Compression Systems

The use of heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems is always increasing. This is because the HVACR systems are necessary for food production and ability to inhabit buildings that otherwise would be inhabitable. Thus, there is continued research focused on improving the efficiency and reducing the negative environmental impact of these systems. The basic vapor compression cycle (i.e., evaporator, condenser, expansion device and compressor), which is still the main underlying HVAC&R technology worldwide, has already reached its limits and researchers are investigating more creative and complex cycles to improve capacity and efficiency. This motivates the development of an enhanced general vapor compression system steady state solver. Steady state simulations require less time than transient simulations, and are used in system design optimization and cost minimization for given performance. This paper presents a comprehensive vapor compression system steady state solver which has several novel features compared to the existing solvers. Firstly, this proposed solver is capable of simulating large number of different designs of vapor compression systems. This includes arbitrary system configurations, multiple air and refrigerant paths, and user defined refrigerants. The solver uses a component-based solution scheme in which the component models are treated as black box objects. This allows a system engineer to quickly assemble and simulate a system where in the component models and performance data comes from disparate sources. This allows different vapor compression systems design engineers, and manufacturers to use the solver without the need to expose any possible confidential component data. The solver is validated using a vapor injection heat pump system with a flash tank and the preliminary modeling results match the experimental results within 10% accuracy. This heat pump system model is also tuned in order to improve the validation accuracy. A parametric case study for a variable refrigerant flow (VRF) system is presented as well to demonstrate the applicability to larger systems

Impact of Charge Degradation on the Life Cycle Climate Performance of a Residential Air- Conditioning System

All the vapor compression systems continuously leak part of the refrigerant charge to the environment, whether during operation or servicing. As a result of the slow leak rates during operation, the refrigerant charge decreases until the system is serviced. This charge degradation, after certain limit, starts to have detrimental effect on the system’s capacity, power consumption, and coefficient of performance (COP). This paper presents a literature review and a summary of the previous experimental work on the under charging or charge degradation of different vapor compression systems especially the ones without a receiver. These systems include residential air conditioning and heat pump systems utilizing different components and refrigerants, and water chiller systems. It is shown that most of these studies show similar trends for the effect of the charge degradation on the system performance. However, it is found that although much of the experimental work exist on the effect of charge degradation on the system performance, no correlation, or comparison yet exists. Thus, based on the literature review, four different correlations, that characterize the effect of charge on system capacity and power consumption, are developed for different systems as follows: two for air-conditioning systems, one for vapor compression water-to-water chiller systems, and one for heat pumps. These correlations can be implemented in vapor compression cycle simulation tools to obtain a better prediction of the system performance throughout its lifetime. The correlations are then implemented in an open source tool for life cycle climate performance (LCCP) based design of vapor compression systems. The LCCP of a residential air conditioning system is evaluated using the tool and the effect of charge degradation on the results is studied. The air conditioning system is simulated using a validated component-based vapor compression system model. The LCCP results obtained using the different correlations are compared and conclusions drawn

An Evaluation of the Environmental Impact of Different Commercial Supermarket Refrigeration Systems Using Low Global Warming Potential Refrigerants

Commercial refrigeration systems consumed 1.21 Quads of primary energy in 2010 and are known to be a major source for refrigerant charge leakage into the environment. Thus, it is important to study the environmental impact of commercial supermarket refrigeration systems and improve their design to minimize any adverse impacts. The system’s Life Cycle Climate Performance (LCCP) was presented as a comprehensive metric with the aim of calculating the equivalent mass of carbon dioxide released into the atmosphere throughout its lifetime, from construction to operation and destruction. In this paper, a new open source tool for the evaluation of the LCCP of different air-conditioning and refrigeration systems is presented. This LCCP tool is used to compare the environmental impact of three typical supermarket refrigeration systems (low temperature, medium temperature, and multiplex direct expansion systems). The environmental impact of these systems is compared based on three different refrigerants as follows: two hydrofluorocarbon (HFC) refrigerants (R404A, and R407F), and a low global warming potential (GWP) refrigerant (N40). The comparison is performed for 8 different US cities representing different climates. The hourly energy consumption of the display cases, required for the calculation of the indirect emissions, is calculated using a widely used building energy modeling tool (EnergyPlus). An uncertainty analysis is conducted on the three systems to determine the effect of the uncertainty of each input on total LCCP. A sensitivity analysis is performed on the three systems to determine the sensitivity of the LCCP results to changes in the charge of the system and power plant emission values used in the calculations. These studies help to determine the design factors, whether in general or for certain climates, which would require more attention when designing a refrigeration system in order to reduce its carbon emissions

Towards plasmon mapping of SERS-active Ag dewetted nanostructures using SPELS

Thermal dewetting of silver thin flm can lead to SERS-active Ag nanoparticles. Here, we report our progress towards using scanning probe energy loss spectroscopy (SPELS) to map the plasmonic behaviour of SERS-active Ag nanoparticles (NP) by investigating NPs produced through the dewetting study of Ag thin flms on SiO2/Si and Ti/SiO2/Si substrates. The nanoparticles size and spatial distribution were controlled by the deposition and thermal annealing parameters. The results of preliminary SPELS measurements of these structures, alongside SERS data show that there is a correlation between the Raman enhancement and the nanoparticle size and interparticle spacing

Mapping the groundwater potentiality of West Qena area, Egypt, using integrated remote sensing and hydro-geophysical techniques

The integrated use of remote sensing imagery and hydro-geophysical field surveys is a well-established approach to map the hydrogeological framework, and thus explore and evaluate the groundwater potentiality of desert lands, where groundwater is considered as the main source of freshwater. This study uses such integrated approach to map the groundwater potentiality of the desert alluvial floodplain of the Nile Valley west of Qena, Egypt, as alternative water source to the River Nile. Typically ground gradient, faults and their stress field, lateral variation of rock permeability, drainage patterns, watersheds, rainfall, lithology, and soil types are the main factors believed to affect the groundwater recharge and storage from the infiltration of present-time and paleo-runoff. Following this generally accepted approach, different remote sensing data sets (SRTM DEM, Landsat-8, ALOS/PALSAR-1, Sentinel-1, and TRMM) as well as auxiliary maps (geological and soil maps) were used to identify and map these factors and prepare thematic maps portraying the different influences they exert on the groundwater recharge. These thematic maps were overlaid and integrated using weights in a GIS framework to generate the groundwater potentiality map which categorizes the different recharge capabilities into five zones. Moreover, the aeromagnetic data were processed to map the deep-seated structures and estimate the depth to basement rocks that may control the groundwater occurrence. In addition, the vertical electrical sounding (VES) measurements were applied and calibrated with the available borehole data to delineate the subsurface geological and hydrogeological setting as well as the groundwater aquifers. Different geoelectric cross-sections and hydro-geophysical maps were constructed using the borehole information and VES interpretation results to show the lateral extension of the different lithological units, groundwater-bearing zones, water table, and the saturated thickness of the aquifer. The GIS model and geophysical results show that the southwest part of Nag’a Hammadi-El-Ghoneimia stretch has very high recharge and storage potentiality and is characterized by the presence of two groundwater-bearing zones. The shallow groundwater aquifer is located at a depth of 30 m with a saturation thickness of more than 43 m. However, there are NW–SE faults crossing the study area and most likely serve as recharge conduits by connecting the shallow aquifer with the deeper ones. Such aquifers connection has been confirmed by investigating the chemical and isotopic composition of their groundwater.Published versio

Design, Synthesis, and Biological Evaluation of Novel 3-Cyanopyridone/Pyrazoline Hybrids as Potential Apoptotic Antiproliferative Agents Targeting EGFR/BRAFV600E^{V600E} Inhibitory Pathways

A series of novel 3-cyanopyridone/pyrazoline hybrids (21–30) exhibiting dual inhibition against EGFR and BRAFV600E has been developed. The synthesized target compounds were tested in vitro against four cancer cell lines. Compounds 28 and 30 demonstrated remarkable antiproliferative activity, boasting GI50 values of 27 nM and 25 nM, respectively. These hybrids exhibited dual inhibitory effects on both EGFR and BRAFV600E pathways. Compounds 28 and 30, akin to Erlotinib, displayed promising anticancer potential. Compound 30 emerged as the most potent inhibitor against cancer cell proliferation and BRAFV600E. Notably, both compounds 28 and 30 induced apoptosis by elevating levels of caspase-3 and -8 and Bax, while downregulating the antiapoptotic Bcl2 protein. Molecular docking studies confirmed the potential of compounds 28 and 30 to act as dual EGFR/BRAFV600E inhibitors. Furthermore, in silico ADMET prediction indicated that most synthesized 3-cyanopyridone/pyrazoline hybrids exhibit low toxicity and minimal adverse effects