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

Integrating Sustainable Manufacturing Assessment into Decision Making for a Production Work Cell

Sustainability has been the focus of intense discussions over the past two decades, with topics surrounding the entire product life cycle. In the manufacturing phase, research has often focused solely on environmental impact assessment or environmental impact and cost analysis in its assessment of sustainability. Few efforts have investigated sustainable production decision making that addresses the three pillars of sustainability concurrently; which requires engineers and managers to consider economic, environmental, and social impacts. An approach is developed to assess broader sustainability impacts by conducting economic assessment, environmental impact assessment, and social impact assessment at the work cell level. Assessment results are then integrated into a sustainable manufacturing assessment framework, along with a modified weighting method based on pairwise comparison and an outranking decision-making method. The approach is illustrated for a representative machining work cell producing stainless steel knives. Economic, environmental, and social impact results are compared for three production scenarios by applying the sustainable manufacturing assessment framework. The case study finds that cutting tool cost is the largest contributor to production costs for the investigated work cell. The level of environmental and social impact varies according to cycle time. Sensitivity analysis is conducted to examine the robustness of the results.Keywords: Decision making, Sustainable manufacturing, Manufacturing work cell, Life cycle assessmen

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

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

Optimization of steel production to improve lifecycle environmental performance

To reduce lifecycle impacts, manufacturers require an understanding of how design, manufacturing, and other decisions influence their eco-footprint across all product lifecycle stages, e.g., manufacturing, use, and end-of-life. However, few tools exist to address manufacturing impacts on the environment. For many products, steelmaking accounts for the majority of manufacturing energy use, with process wastes also representing significant concerns. A predictive model for a steelmaking electric arc furnace (EAF) is briefly described and is then used to illustrate how environmental performance can be optimized for a given steel alloy. Process inputs are identified that minimize a variety of environmental measures

Examining Industry Expectations for Content Knowledge in Mechatronics Across Career and Professional Certificate Programs

Technological advancements, ever-evolving necessary skillsets, and an aging workforce have all contributed to a growing labor crisis wherein there are not enough qualified candidates available to fill vacant jobs in the manufacturing sector – in essence, a skilled labor shortage. Certificate programs (earned independently in a two-year college, while working in industry, or concurrently with an undergraduate degree) in hybrid fields like mechatronics provide a conduit for producing qualified candidates that ideally are equipped with the skills required by industry. However, it is important to gauge what industry expects from such graduates; in other words, pragmatically, what do they expect these students to know after completing a given certificate? The current study surveyed a range of mechatronics industry professionals on their expectations for content knowledge on a list of relevant skills for two different certificate programs in mechatronics (i.e., career pathway (two-year) and professional (four-year) certificates). Results showed that expectations differed for the two certificates on certain topics, especially related to feedback and control systems. It is hoped that these findings will enable the subsequent development and refinement of certificate programs to best ensure that students are mastering the critical requisite skills to be successful in their manufacturing careers

A comparison of manufacturing and remanufacturing energy intensities with application to diesel engine production

Climate change reports and policies relating to end-of-use products, CO2 emissions, and energy are causing manufacturers to examine their operations closely. Several reports have touted the economic and environmental benefits of remanufacturing, including claims of significant reductions in terms of energy and CO2 emissions. However, large-scale remanufacturing of heavy equipment engine components has not been closely examined and no standard procedure exists to quantify the benefits of remanufacturing. A methodology is presented for determining the energy intensity and benefits of remanufacturing as compared to new manufacturing, and this is applied to a diesel engine example. These findings are used to estimate the embodied manufacturing/remanufacturing energy across multiple use cycles. © 2008

Improving worker health and safety in wire arc additive manufacturing : A graph-based approach

Research on human health and safety impacts of wire arc additive manufacturing is often overshadowed by the need for weld quality and mechanical strength improvements. To address this gap, a review of research literature is conducted focusing on the influence of welding process parameters, welding fumes, and fume exposure on worker health. The review uses a causal graph to classify research literature into two domains: manufacturing technology and public health. The graph serves as a precursor to development of a Bayesian network model, whose expected benefits, steps for implementation, and likely challenges that would be encountered during implementation are discussed.publishedVersionPeer reviewe

An economic and environmental assessment model for microchannel device manufacturing: part 2-Application

Microchannel heat exchangers provide large surface area to volume ratios and accelerated heat transfer, leading to compact form factors for application in portable and distributed thermal management and waste heat recovery. The application of microchannel heat exchangers in industry has been slowed by high manufacturing costs. Therefore, efforts are being made to find new ways to manufacture these components. This research investigates the application of a process-based cost and environmental impact assessment model to the evaluation of manufacturing alternatives to produce microchannel heat exchangers. A bottom-up process-based cost modeling method is used to estimate the cost of manufacturing a microchannel heat recovery unit (HRU). Cradle-to-gate life cycle assessment is simultaneously applied to evaluate environmental impact. Both sets of calculations extend from a single common set of data consisting of production and device geometry parameters. An analysis is demonstrated for different manufacturing alternatives for producing the HRU. Among the six manufacturing plans evaluated, the combination of laser cutting and diffusion brazing was found to have the lowest cost but the highest environmental impact, while the combination of photochemical machining and laser welding was found to have the lowest environmental impact with a comparatively high cost. Among the cost categories defined, consumables, capital tooling, and utilities were found to be the primary drivers for cost and environmental impact suggesting these as areas to concentrate in future process capability assessments and technology development.Keywords: Environmental impact assessment, Decision making, Microchannel process technology, Graphical user interface, Bottom-up cost modelin