Thermal Performance Evaluation of a Residential Solar/Gas Hybrid Water Heating System

In climate regions with lower average daily solar radiation, such as the Pacific Northwest, a solar energy collector might not economically satisfy year-round domestic water heating demands, requiring an auxiliary unit, such as a natural gas water heater. Previous studies of such hybrid systems have shown that the efficiencies achieved while running in combined solar/gas mode was lower than expected. This inefficiency was attributed to a reduction in gas burner efficiency when the process fluid was partially pre-heated by the solar input. To predict the actual energy and cost savings under various design conditions, the performance of solar/gas hybrid systems must be better understood. In this work, the performance of a commercial hybrid solar/gas system is experimentally characterized to evaluate individual component and overall system efficiency. The hybrid water heating system consisted of three flat plate collectors arranged in series (total area = 6.44 m2), and a 22.3 kW natural gas burner. Under different temperature lifts and solar insolation values, the system was operated at three different modes of heating: solar, gas, and combined solar/gas mode. Efficiency value for each mode was calculated. Based on the experimental efficiency results, a configuration that would provide higher efficiency for combined solar/gas heating is suggested

Energy and carbon footprint reduction during textile-based product design and manufacturing

Due to concerns over non-renewable energy consumption and associated emissions, industry has sought methods and technologies to support energy efficiency practices and use of alternative energy during product manufacturing, use, and end-of-life. Efforts have been undertaken to more precisely calculate environmental metrics, such as energy consumption and carbon footprint, to support broader sustainable design activities. The work reported endeavours to integrate sustainability principles into the design of products, manufacturing processes, and relevant supply chain networks to assist decision makers. Two backpacks are evaluated to examine the influence of design choices on energy consumption and carbon footprint. The study system boundary includes raw material extraction, materials processing, manufacturing operations, and transportation for each component. The results show that manufacturing processes dominate transportation-related impacts. The work appears to be the first to apply a comprehensive process-based approach to estimate cradle-to-gate energy consumption and carbon footprint for textile-based product design variants

Cyber Collaboratory-based Sustainable Design Education: A Pedagogical Framework

Educators from across the educational spectrum are faced with challenges in delivering curricula that address sustainability issues. This article introduces a cyber-based interactive e-learning platform, entitled the Sustainable Product Development Collaboratory, which is focused on addressing this need. This collaboratory aims to educate a wide spectrum of learners in the concepts of sustainable design and manufacturing by demonstrating the effects of product design on supply chain costs and environmental impacts. In this paper, we discuss the overall conceptual framework of this collaboratory along with pedagogical and instructional methodologies related to collaboratory-based sustainable design education. Finally, a sample learning module is presented along with methods for assessment of student learning and experiences with the collaboratory

Investigation of the combined efficiency of a solar/gas hybrid water heating system

In climate regions with large seasonal variations in solar radiation, such as the Pacific Northwest of the United States, a solar thermal energy collector might not economically satisfy year-round domestic water heating demands, requiring an auxiliary unit, such as a natural gas-fired water heater. Previous studies have shown that the burner efficiency of a gas-fired water heater varies depending on the log-mean temperature difference between the cold fluid (water) and the hot fluid (combustion gases). In a solar/gas hybrid water heating system, where solar collectors are used in conjunction with a gas-fired heater, the partial heating of water provided by solar input reduces the log-mean temperature difference value for the gas heater, reducing the efficiency of the gas burner. Since this efficiency reduction varies depending on the amount of pre-heating provided by solar energy input, it is difficult to accurately predict the actual cost and energy savings offered by solar/gas hybrid water heaters in different climates and operation scenarios. Hence, to predict the actual energy and cost savings under various design conditions, the performance of solar/gas hybrid systems must be better understood. The objective of this work is to experimentally determine the thermal performance of a solar/gas water hybrid water heating system with a 6.44 m2 flat plate solar collector array and a 22.3 kW natural gas burner in Corvallis, Oregon, USA. Under different temperature lifts and solar insolation values, the system was operated at three different modes of heating: solar, gas, and combined solar/gas mode. The overall system thermal efficiency value for each mode is calculated. The efficiency of the solar collector heating system was found to be 41.97%, 39.82%, and 35.05% at initial water temperature of 20, 30, and 51.5 °C, respectively. For initial water temperatures of 20, 30, and 51.5 °C, the efficiency of the gas burner was found to be 69.2%, 66.4%, and 65.5% at the HHV, and 76.7%, 73.6%, and 72.6% at the LHV of natural gas, respectively. In the combined solar/gas heating mode, the efficiency of the gas burner decreased with increasing solar fraction. For solar fractions of 4.93%, 9.40%, 11.39%, and 14.27%, the efficiency of the gas burner in terms of the HHV of natural gas was found to be of 69.08%, 66.80%, 66.17%, and 65.18%, respectively. Based on the experimental results, a configuration that would provide higher overall system efficiency for combined solar/gas heating is suggested

Enabling Non-expert Sustainable Manufacturing Process and Supply Chain Analysis During the Early Product Design Phase

Consumers are pressuring companies to produce products with superior sustainability performance, yet educators are disadvantaged in training students about sustainable engineering and many engineers are often not well-positioned to perform product sustainability assessments. In particular, quantifying environmental impacts is a key aspect of achieving improved product sustainability performance that has garnered much attention over the past two decades, but tools remain deficient to assist manufacturing decision making. In light of efforts undertaken to develop sustainability assessment methodologies, we review recent developments in quantifying a widely adopted environmental performance metric, carbon footprint, in manufacturing processes and supply chain networks. We also present a methodology to address the deficit identified from this review for simple, easy-to-use sustainability assessment methods and tools. We suggest a questionnaire-based methodology to provide non-experts with a better understanding of sustainability performance, specifically during the product design phase. An application of the methodology is demonstrated to quantify and compare environmental impacts for the production of two quadcopter upper shell designs. The review presented can help the sustainable design and manufacturing community in identifying research gaps, while non-expert engineers and engineering students can benefit from application of the presented methodology in learning and in practice

Investigation of thermal influence on weld microstructure and mechanical properties in wire and arc additive manufacturing of steels

Alloy steels are commonly used in many industrial and consumer products to take advantage of their strength, ductility, and toughness properties. In addition, their machinability and weldability performance make alloy steels suitable for a range of manufacturing operations. The advent of additive manufacturing technologies, such as wire and arc additive manufacturing (WAAM), has enabled welding of alloy steels into complex and customized near net-shape products. However, the functional reliability of as-built WAAM products is often uncertain due to a lack of understanding of the effects of process parameters on the material microstructure and mechanical properties that develop during welding, primarily driven by thermal phenomena. This study investigated the influence of thermal phenomena in WAAM on the microstructure and mechanical properties of two alloy steels (G4Si1, a mild steel, and AM70, a high-strength, low-alloy steel). The interrelationships between process parameters, heating and cooling cycles of the welded part, and the resultant microstructure and mechanical properties were characterized. The welded part experienced multiple reheating cycles, a consequence of the layer-by-layer manufacturing approach. Thus, high temperature gradients at the start of the weld formed fine grain structure, while coarser grains were formed as the height of the part increases and the temperature gradient decreased. Microstructural analysis identified the presence of acicular ferrite and equiaxed ferrite structures in G4Si1 welds, as well as a small volume fraction of pearlite along the ferrite grain boundaries. Analysis of AM70 welds found acicular ferrite, martensite, and bainite structures. Mechanical testing for both materials found that the hardness of the material decreased with the increase in the height of the welded part as a result of the decrease in the temperature gradient and cooling rate. In addition, higher hardness and yield strength, and lower elongation at failure was observed for parts printed using process parameters with lower energy input. The findings from this work can support automated process parameter tuning to control thermal phenomena during welding and, in turn, control the microstructure and mechanical properties of printed parts.publishedVersionPeer reviewe

Evaluating the use of zinc oxide and titanium dioxide nanoparticles in a metalworking fluid from a toxicological perspective

Adding nanoparticles (NPs) to metalworking fluids (MWFs) has been shown to improve performance in metal cutting. Zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO₂ NPs), for example, have exhibited the ability to improve lubricant performance, decrease the heat created by machining operations, reduce friction and wear, and enhance thermal conductivity. ZnO and TiO₂ NPs are also relatively inexpensive compared to many other NPs. Precautionary concerns of human health risks and environmental impacts, however, are especially important when adding NPs to MWFs. The goal of this research is to investigate the potential environmental and human health effects of these nanoenabled products during early design and development. This research builds on a prior investigation of the stability and toxicity characteristics of NPs used in metalworking nanofluids (MWnF™). The previous study only investigated one type of NP at one level of concentration. This research expands on the previous investigations through the valuation of three different types of NPs that vary in morphology (size and shape) and was conducted over a wide range of concentrations in the base fluid. In the presented work, mixtures of a microemulsion (TRIM® MicroSol® 585XT), two different types of TiO₂ NPs (referred to as TiO₂A and TiO₂B) and one type of ZnO NP were used to evaluate MWnF™ stability and toxicity. Dynamic light scattering (DLS) was used to assess stability over time and an embryonic zebrafish assay was used to assess toxicological impacts. The results reveal that, in general, the addition of these NPs increased toxicity relative to the NPfree formulation. The lowest rate of zebrafish malformations occurred at 5 g/L TiO₂A NP, which was even lower than for the base fluid. This result is particularly promising for future MWnF™ development, given that the mortality rate for 5 g/L TiO₂A was not significantly different than for the base fluid.Keywords: Environmental and health effects, Titanium Dioxide Nanoparticles, Zinc Oxide Nanoparticles, Nanotoxicology, Nanofluid Stabilit

Development of Learning Modules for Sustainable Life Cycle Product Design: A Constructionist Approach

Constructionism is an approach to learning in which learners construct their own understanding and knowledge through making a meaningful product. A cyberlearning environment for sustainable life cycle engineering design has been developed based upon this approach through a multi-university research project funded by the NSF entitled “Constructionism in Learning: Sustainable Life Cycle Engineering (CooL:SLiCE).” The pedagogic significance of CooL:SLiCE is to better enable university students to learn about sustainable product life cycle engineering design by realizing effective learning modules for personalized environmentally-responsible product design. The CooL:SliCE platform has developed a web-based portal with three learning modules: 1) Sustainable product architecture and supplier selection (S-PASS), 2) Visualization and CAD design, and 3) Manufacturing analysis. To test these modules, students from three different universities with different engineering backgrounds were asked to design sustainable multi-copters through the developed web-based portal. A case study of this intercollegiate collaborative pilot project is developed from multiple data sources to describe the effectiveness of constructionism to engage students in learning sustainable life-cycle engineering