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The paper presents a cause-and-effect analysis of the failure of a 130 MWt gas-fired water boiler. The fault was a rupture of the helically finned tubes in the first rows of the second-stage water heater (ECO2). The high frequency of failures forced the boiler user to investigate their causes. The rapid drop in water flow in the ECO2 and the tightly finned pipes suggested that the permissible operating temperature of the steel used was exceeded. The only possible way to assess the working conditions was through a CFD simulation of the operation of the ECO2. Validated with the data acquisition system, the results show that the main reason for the failure was the overheating of the first rows of finned water heater pipes, regardless of the boiler load. The high heat flux value, exceeding 500,000 W/m2, and the increased flue gas temperature in front of the ECO2, almost reaching 900 °C, affected the appearance of the boiling film, limiting the cooling of the tube wall. Heat radiation and eddies behind the tubes significantly impacted the non-uniform temperature distribution, resulting in high pipe wall stress. By analyzing the service life of the first row of pipes based on the Larson–Miller parameter, it was concluded that the pipes would fail after only a few tens of hours. [ABSTRACT FROM AUTHOR]

The study focused on comparing the electrical energy and the volume of hot water consumed using the inefficient 18 kW, 1600 L electric boiler and an efficient and renewable air source heat pump (ASHP) unit with an input power of 6.0 kW, as retrofit to the electric boiler, for sanitary hot water production. A data acquisition system was built and deployed, to monitor the baseline while the electric boiler was in used and the performance assessment were the ASHP water heater was in operation. The results showed that the annual energy saving and the load factor reduction, due to the retrofitting of the electric boiler with the ASHP unit, was 52117.630 kWh and 0.092. One-way ANOVA test depicted that the p-value of the average month-day electrical energies consumed by the electric boiler and the ASHP water heater during the entire monitoring period was 1.09 x 10-22. A very small p-value confirmed a significant difference existed in at least one of the among four groups of the average month-day electrical energies consumed and the heating season. The implementation of ASHP water heater for sanitary water heating at the residence on University's campus served as sustainable energy technology. [ABSTRACT FROM AUTHOR]

Carbon monoxide is one of the indoor air contaminants in homes that causes the most concern among energy efficiency programs. Programs that perform energy upgrades to homes spend substantial effort evaluating carbon monoxide hazards. Furnaces, boilers, water heaters, and ovens/ranges are common sources of carbon monoxide in the indoor environment. The current article presents results of carbon monoxide measurements from two studies that looked at homes that underwent energy efficiency upgrades as part of the U.S. Department of Energy's low-income Weatherization Assistance Program. In the first study, carbon monoxide was measured in the flues of furnaces, boilers, and water heaters, in the exhaust of ovens/ranges, and in the indoor ambient air. Measurements of the appliance combustion gases were done once while at the site, and indoor air measurements were done using dataloggers recording for about a month before and after weatherization. In the second study the focus was only on measured indoor ambient air, also with measurements using dataloggers for about 1 week. The results show that most appliances have carbon monoxide levels within allowable standards, though some are elevated. Regarding indoor ambient air, less than 5% of homes have persistent levels (i.e., for more than 10% of the time) of carbon monoxide of 5 ppm or higher. However, elevated peak levels above 9 ppm are much more common, with about 20%–30% of units in both studies reached 9–10 ppm at least once within a week-long test period. These results show that elevated indoor ambient carbon monoxide is a highly episodic phenomenon, and, therefore, not well addressed by whole-home ventilation. Further, the data suggest that it is the cooking appliances that are most subject to producing short-term elevations of carbon monoxide. The current article also includes a comparison of carbon monoxide before and after retrofits. [ABSTRACT FROM PUBLISHER]

This study focuses on the environmental impact assessment through Life Cycle Analysis (LCA) of two innovative 10 kW pellet boilers. In particular, the second boiler represents a technological evolution of the first one developed to improve its performance in terms of efficiency and environmental impact. For both boilers, emission factors measured during laboratory tests (full load tests and specific load cycle tests representative of real life boiler operation) have been used as input data in the life cycle analysis. The SimaPro software (v.8.0.4.30) was used for the LCA and the ReCiPe Midpoint method (European version H) was chosen to assess the environmental impact of all boilers (according to LCA ISO standards). In addition, the ReCiPe Endpoint method was used to compare the final results of all 5 boilers with literature data. The pelletisation process represented the most relevant share of the overall environmental impact followed by the operational phase, the manufacturing phase and the disposal phase. A sensitivity analysis performed on the most efficient pellet boiler evidenced the variation of the boiler’s environmental impact as a function of PM10 and NO X emission factors with respect to emission factors monitored during boiler full load operation. Moreover, the reduction of the boiler’s weight and the adoption of new electronic components led to a consistent reduction (−18%) of its environmental impact with respect to the previous technology. A second LCA has been carried on for a 15 kW oil boiler, a 15 kW natural gas boiler and a 15 kW pellet boiler, representative of the state of the art of EU technology, to finally compare all LCA results. Results showed the environmental impact reduction of BW10 and BW10 2 pellet boilers with respect to fossil fuelled boilers mainly due to their reduced impact on CC (reductions by 86–90% and 88–91% with respect to the NG and oil boilers respectively), NLT (reductions by 77–79% and 86–87% with respect to the NG and oil boilers respectively) and FD (reductions by 89–92% and 90–93% with respect to the NG and oil boilers respectively) ReCiPe Midpoint subcategories. [ABSTRACT FROM AUTHOR]

Abstract: This simulation study investigates both different boiler specifications and various kinds of boiler integration in solar thermal combi systems with the help of a new developed fossil fuel boiler model. For each variant, the simulation outcomes to be discussed are the annual boiler efficiency, the cycling rate and, as the main indicator, the primary energy savings of the complete system. The results indicate that the effects of a solar thermal system on the annual boiler efficiency are small. Besides the system layout the annual amounts of hot water and space heating demand and their temperature levels affect the impact of the solar thermal system. Each additional storage tank, which is heated by conventional energy, should be analyzed critically due to their additional heat losses, which reduce the system efficiency. The latter is particularly true for a boiler buffer storage. This study points out that the savings of primary and final energy are the most important indicators for the assessment of solar thermal combi systems. Subsystem indicators like the annual values of collector yield and boiler efficiency give additional information, but they are not sufficient for a full evaluation of a complete system. [Copyright &y& Elsevier]

Abstract: This paper deals with exergoeconomic analysis of a dormitory heated by a conventional boiler in a central heating system. The energy and exergy flows are examined from the generation stage to the envelope of the building. The energy and exergy flows between the stages are obtained using a predesign tool for an optimized building design. Exergetic and exergoeconomic analyses of some heating equipment are comprehensively evaluated. A conventional boiler and a water heater in the central heating system are considered in the analysis. Based on the analysis results obtained, the total exergy input rate is calculated to be 1455kW while the largest exergy loss rate is found to be 987.6kW. Exergetic efficiencies of the conventional boiler and the water heater are also obtained to be 15.6% and 20.4%, respectively. [Copyright &y& Elsevier]

Abstract: Condensing boilers allow better performances when return temperatures from the plant are lower and above all when these temperatures are below the dew temperature of the smoke. That is the reason why many believe that condensing boiler is not suitable for the traditional heating plant terminals: the radiators. Instead the classic control system with weather compensation curve produces relatively low temperatures and an appreciable condensing operation during March, April, October and November. Moreover, condensing boilers allow a better performance than traditional boiler even when they do not perform condensing operation. However for the optimum exploitation of condensing boilers in a radiator plant, variable-flow-rate plants should be selected that permit every outside condition to maintain a high difference between delivery and return temperature. This control selection, which is fully consistent with the use of thermostatic valves, needs variable-flow-rate pumps and, if possible, with proportional head. [Copyright &y& Elsevier]

Abstract: Enhancement of energy efficiency and introduction of newer and more efficient space and water heating technologies in the UK domestic sector are essential if the UK is to achieve its ambitious target for 2050 of reducing greenhouse gas (GHG) emissions to less than 80% of 1990 levels. The UK domestic sector currently relies heavily on conventional boilers for space and water heating even though electric or gas engine driven vapour compression heat pumps can provide heating and cooling with more than double the efficiency of conventional boilers. UK government has recently introduced laws and policies that are designed to accelerate the uptake of renewable heating technologies by domestic consumers rather than relying solely on market forces. To date despite their excellent performance heat pumps are not the primary choice of the general UK domestic consumer. Factors that may influence this behaviour have been analysed and are discussed here. [Copyright &y& Elsevier]

The objective of this paper is to perform the energy, exergy and exergoeconomic analysis for the Hamedan steam power plant. In the first part of the paper, the exergy destruction and exergy loss of each component of this power plant is estimated. Moreover, the effects of the load variations and ambient temperature are calculated in order to obtain a good insight into this analysis. The exergy efficiencies of the boiler, turbine, pump, heaters and the condenser are estimated at different ambient temperatures. The results show that energy losses have mainly occurred in the condenser where 306.9 MW is lost to the environment while only 67.63 MW has been lost from the boiler. Nevertheless, the irreversibility rate of the boiler is higher than the irreversibility rates of the other components. It is due to the fact that the combustion reaction and its high temperature are the most significant sources of exergy destruction in the boiler system, which can be reduced by preheating the combustion air and reducing the air–fuel ratio. When the ambient temperature is increased from 5 to 24°C, the irreversibility rate of the boiler, turbine, feed water heaters, pumps and the total irreversibility rate of the plant are increased. In addition, as the load varies from 125 to 250 MW (i.e. full load) the exergy efficiency of the boiler and turbine, condenser and heaters are increased due to the fact that the power plant is designed for the full load. In the second part of the paper, the exergoeconomic analysis is done for each component of the power plant in order to calculate the cost of exergy destruction. The results show that the boiler has the highest cost of exergy destruction. In addition, an optimization procedure is developed for that power plant. The results show that by considering the decision variables, the cost of exergy destruction and purchase can be decreased by almost 17.11%. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: To comply with energy saving regulations, vacuum insulation panels (VIPs) have been used in refrigerators and automatic vending machines for some years now. VIPs for low-temperature applications are constructed from laminated plastic films, which are heat-welded together to maintain a vacuum inside. At high temperatures, the vacuum is lost and the performance of these panels degrades sharply. But recently there has been a demand for efficient insulation materials for use in hot-water equipment (e.g., vending machines, heat pumps, boilers and water heaters), which necessitates the study of laminated plastic films and getter devices for high-temperature VIPs. Measurements have been made of the allowable temperature limit of plastic films and the release of water vapor and outgassing during temperature-programmed adsorption with different getter materials. Suitable laminated films and getter device systems for high-temperature VIPs were chosen based on the results of these measurements, and their long-term reliability was evaluated by measuring the thermal conductivity at high temperature. As a result it was found that high-retort CPP and PBT films are the most suitable materials for use in the welded layers of high-temperature VIPs (105°C). [Copyright &y& Elsevier]

Purpose - The article aims at contributing to a better understanding of the interdependence between supply management and the strategic position of the buying firm. Design/methodology/approach - The research follows a qualitative analysis of two cases: Adira, a family-owned manufacturer of machinery to cut steel, and Vulcano, a manufacturer of instantaneous house gas water-heaters and boilers. Findings - The article finds that supply management decisions depend not only on the network position of the buying firm, but also on the network vision of its managers. Research limitations/implications - The study is based on two contrasting cases. Further research should develop and test the findings by using other cases and methodological approaches more quantitative in nature. Practical implications - The article has three major practical implications: supply management should integrate three levels of decisions: dyadic, portfolio and network decisions; supply management does not depend solely on firms' strategic positioning and strategies, but also on managers' network theory about the role and capabilities of suppliers; and "no strategy" can also be a strategy. Originality/value - The study was conducted on the basis of a multi-dimensional model that integrates three levels of analysis: dyadic, portfolio and network. [ABSTRACT FROM AUTHOR]

Outdoor wood boilers (OWBs) are detached wood-fired units that heat water used for domestic consumption and heating. The increasing use of OWBs has prompted regulatory concern because of escalating public complaints. Few field studies of OWB ambient emissions have been conducted, limiting efforts to assess this air quality problem. A screening level evaluation was conducted to characterize ambient fine particle (PM2.5) levels nearby an OWB device and to overview operating and design factors that could influence PM2.5 levels. High hourly (186 μ g/m3 4.3 h mean, 665 μg/m3 95th percentile) and peak continuous (8,880 μg/m3 15.5 avg) PM2.5 concentrations were found within 50–150 ft of an OWB relative to background levels throughout the course of nearly routine operating conditions. Values were highest during air intake within 1 h of fuel loading (416 μg/m3 1 h mean) compared to air-starved 22–24 h after loading (115 μg/m3 3.3 h mean). OWB features that could affect PM2.5 levels include exemption from federal wood stove standards, poor combustion design, large firebox capacity, trash burning use, low stack height, and four-season utility. In view of cardiac and respiratory health risks associated with transient exposure to ambient PM2.5 at levels well below those reported here, this pilot study contributes to the risk assessment field by identifying an emerging problem of potential public health significance. [ABSTRACT FROM AUTHOR]