Condensing Boiler Research Articles

Investigation of the Flue Gas and Condensate Compositions during the Combustion of Natural Gas and Methane-hydrogen Mixtures in a Condensing Boiler

Investigation of the Flue Gas and Condensate Compositions during the Combustion of Natural Gas and Methane-hydrogen Mixtures in a Condensing Boiler

Life Cycle Assessment of the Domestic Micro Heat and Power Generation Proton Exchange Membrane Fuel Cell in Comparison with the Gas Condensing Boiler Plus Electricity from the Grid

The energy demand of private households contributes globally to 36.5% of the total CO2 emissions. To analyze the emissions reduction potential, we conducted a comparative life cycle assessment of a proton exchange membrane fuel cell in a residential application and a conventional system with a stand-alone gas condensing boiler and electricity from a grid mix. The period under review was referred to as the service life of the PEMFC and is assumed to be 10 years (83,038 h of PEMFC). The applicability of this in a single-family house built between 1991 and 2000 under German climatic conditions was investigated. The functional unit is set to the thermal energy demand of 16,244 kWh/a and electricity demand of 4919 kWh/a of a single-family house. The impact assessment method “CML 2001–August 2016” was used in this investigation. The manufacturing phase of the proton exchange membrane fuel cell showed disadvantages, whereby the use phase had significant advantages in most of the environmental impact categories as compared to the conventional energy supply system. Considering the whole life cycle, the advantages from the use phase could outperform the disadvantages from the manufacturing phase in most of the impact categories, except for ADP elements and TETP.

The Direct Effect of Enriching the Gaseous Combustible with 23% Hydrogen in Condensing Boilers’ Operation

Following the international trend of using hydrogen as combustible in many industry branches, this paper investigates the impact of mixing methane gas with 23% hydrogen (G222) on condensing boilers’ operation. After modeling and testing several boilers with heat exchange surface different designs, the authors gathered enough information to introduce a new concept, namely High-Performance Condensing Boiler (HPCB). All the boilers that fit into this approach have the same operational parameters at nominal heat load, including the CO2 concentrations in flue gases. After testing a flattened pipes condensing boiler, a CO2 emission reduction coefficient of 1.1 was determined when converting from methane gas to G222 as combustible. Thus, by inserting into the national grid a G222 mixture, an important reduction in greenhouse gases can be achieved. For a 28 kW condensing boiler, the annual reduction in CO2 emissions averages 1.26 tons, value which was experimentally obtained and is consistent with the theoretical evaluation.

Long-Term Neutralization of Acidic Condensate from Gas Condensing Boilers

The pH of wastewater needs to remain between 6 and 9 to protect water organisms. Condensates from a gas condensing boiler have a pH value of about 3. An optimal way to neutralize the acid condensate is to use cheap material such as dolomite. An old-style neutralization box (NB) was tested with a standard faction of dolomite. However, it did not sufficiently neutralize the condensate. Therefore, several tests were performed involving changes to the construction of the neutralization box, a finer fraction of dolomite and aerating the condensate in the neutralization box. In summary, a new NB technology with partitions, a finer fraction of dolomite and condensate aeration proved sufficient in the neutralization of the pH of the condensate in the short and long terms. It depends on what material the heat exchanger is made of in the condensing boiler. The aluminum content reduces the effectiveness of dolomite in the long run, so aerating the condensate in the NB is recommended, which leads to its more effective neutralization.

CO2 Emissions Reduction through Increasing H2 Participation in Gaseous Combustible—Condensing Boilers Functional Response

Considering the imperative reduction in CO2 emissions, both from household heating and hot water producing facilities, one of the mainstream directions is to reduce hydrocarbons in combustibles by replacing them with hydrogen. The authors analyze condensing boilers operating when hydrogen is mixed with standard gaseous fuel (CH4). The hydrogen (H2) volumetric participation in the mixture is considered to vary in the range of 0 to 20%. The operation of the condensing boilers will be numerically modeled by computational programs and prior validated by experimental studies concluded in a European Certified Laboratory. The study concluded that an increase in the combustible flow with 16% will compensate the maximum H2 concentration situation with no other implications on the boiler’s thermal efficiency, together with a decrease in CO2 emissions by approximately 7%. By assuming 0.9 (to/year/boiler), the value of CO2 emissions reduction for the condensing boiler determined in the paper, and extrapolating it for the estimated number of boilers to be sold for the period 2019–2024, a 254,700-ton CO2/year reduction resulted.

Rational Heat Schemes Using Condensing Boilers in Local Heat Supply Systems

Within the framework of this publication, thermal diagrams of autonomous heat supply systems using condensing heat generators are considered. The insignificant Russian experience of using small condensation boilers in residential construction shows that it is often used to simply replace traditional equipment with condensation technology in existing (or traditionally used) heat schemes, for example, with protection of the boiler from “cold return” by recirculating heat carrier or installing a hydraulic regulator. The consequence of this is almost completely lost the effect of the use of condensing boilers. At the same time, even using the heating temperature schedule of quality regulation 80-60°C and applying water heating to the DHW target up to 45°C you can achieve the effect of the boiler operation in the condensation mode, depending on the construction area, up to 75% of the total working time per year, generating about 70% of thermal energy in the annual cycle. However, it must be borne in mind that the efficiency of the condensing boiler is determined by the part of the latent heat of water vapor in the combustion products, which can be obtained with partial condensation. If this part is small, for example, when cooling the flue gases to 50-45°C (on gas), then the efficiency gain is only 1-3%.

Application of Gas Condensing Boilers in Domestic Heating

Application of Gas Condensing Boilers in Domestic Heating

Life cycle assessment of domestic fuel cell micro combined heat and power generation: Exploring influential factors

Residential Fuel Cell micro combined heat and power (FC-μCHP) systems can help decarburizing the energy system. In the European ene.field project, the environmental performance of FC-μCHP under different conditions was therefore evaluated by means of a comprehensive Life Cycle Assessment (LCA). Important influential factors were explored, i.e. heating demands, full load hours (FLHs) and electricity replacement mixes (ERMs). The systems were compared with a stand-alone Gas Condensing Boiler (GCB) and a heat pump (HP, only in single family homes, SFHs). For the initially assumed FLHs and the current ENTSO-E ERM, relevant environmental impacts including climate change are generally smaller for the FC-μCHPs than for the HP and the stand-alone GCB. In the setting “existing SFHs in central climate” with the highest deployment potential, GHG emission savings are higher the more carbon-intensive the ERM is and/or higher the net electricity export into the grid is. The results are discussed and put into perspective. Further research demands as well as product development opportunities are outlined. The importance of a green hydrogen economy is emphasized.

Study on condensing boiler technology potential accounting various fuels

Condensing boilers represent now the most advanced technology in boilers field. Currently, their operation is almost entirely based on natural gas, which mostly consists of methane (typically more than 95 % in volumetric composition). When natural gas is not available – for example when there is no access to the natural gas network – the usual alternative is LPG. Liquid fuel is also taken into account in some studies. The energy saving potential by harnessing the latent heat of water vapors from flue gas is analyzed in the paper for another seven fuels – butane, propane, coal gasification gas, biogas, heavy fuel oil, diesel and bio-oil – and the reference fuel is methane. The greenhouse impact of these fuels is also analyzed. The study indicates that biogas offers the highest energy saving potential for condensing technology (even higher than methane) while heavy fuel oil has the lowest potential. Evaluation of CO2 emissions shows that coal gasification gas has the greatest greenhouse impact.

Актуальність використання газових конденсаційних котлів для опалення малоповерхового житла

Актуальність використання газових конденсаційних котлів для опалення малоповерхового житла

Influence of Heating Oil Formulation on the Combustion and Emissions of Domestic Condensing Boilers Using Fossil Fuel and Renewable Fuel Mixtures

The residential sector is responsible for approximately 40% of final energy consumption in the European Union, being a potential target to increase energy efficiency and improve urban air quality. New high-efficiency heating oil boilers have been developed requiring fuel adaption by diminishing the sulfur content in the fuel. The present work has led to the conclusion that further fuel development, including the use of alternative fuels, may be directed to reduce fossil fuel consumption and decrease the formation of pollutants. Specific fuel properties, such as distillation curve and nitrogen content, show an influence on pollutant emissions, especially NOx, which can be reduced below the lowest limit required for gas domestic boilers, which, until now, set the state of the art in terms of NOx emissions. The addition of renewable fuels in heating oil formulations, contributing to a global CO2 decrease, does not affect the reduction in NOx emissions as far as it does not affect the nitrogen content and dis...

Measurement method and influencing factors of temperature and humidity of condensed flue gas based on in situ flue gas heat tracing

Condensing boilers are efficient for the utilization of natural gas. However, condensed droplets in flue gas are supercooled after condensation heat transfer, and direct contact devices cannot accurately measure the temperature of flue gas containing such droplets. Therefore, an in situ heating interlayer pumping device was designed. Experimental results showed that in situ heating interlayer pumping device can effectively filtered out the influence of supercooled droplets, the temperature of flue gas measured by the proposed device was about 3 °C higher than that measured by direct contact temperature measuring device; the device optimum flow rate was 0.35 L/min, optimum heat tracing temperature was in the range 100–140 °C; the effective reliability of the device was verified experimentally using the positive balance efficiency and the counter balance efficiency of 30-kW gas-fired condensing heat-transfer test platform.

Experimental Investigation of a Novel Condensing Boiler

A novel laboratory type condensing boiler was developed and a data acquisition system was set up in order to measure physical magnitudes related to the performance of the developed boiler. A closed circuit water circulation system was included in the experimental setup in order to circulate water as the energy carrier fluid. The boiler was operated according to the predetermined parameters and data acquisition system collect the data from electronic transmitters placed in the probes at the certain points in the experimental setup. All these results were presented in graphical form and they are interpreted in terms of physics related to the phenomena. The temperature increase in the boiler changes in a parabolic manner. At the beginning of the incident, convection dominantly occurs in respect of heat transfer even though radiation also exists. However radiation contributes more with elapsed time in the experiment and temperature rise curve deviates from the linear path. Numerical analyses can contribute to the findings as well as design parameters.

Computational Model for a Condensing Boiler with Finned Tubes Heat Exchanger

European regulations state a minimum boiler efficiency for the main steady-state functioning conditions and for the overall heating season conditions. In order to comply the demands of the new regulations, more and more boiler manufacturers are switching the gas boilers production to condensing functioning. In the paper we present the numerical and computational modeling of a boiler made out of packages of finned tubes and packages of smooth pipes. Validation of the computational results is made by comparison with experimental results obtained in a certified laboratory for the modelled equipment (boiler). The modelling was set on an aluminium finned tubes heat exchanger existent in the testing laboratory (part of a condensing boiler). The geometry modeling considered the discretization of the heat exchanger in several zones, characterized by homogenous flue gas flow speed, flow geometry and heat transfer characteristics (mainly feature-length). A good correlation between measured and calculated values was obtained, the error ranging +/- 1% for the total and sensible heat and for thermal efficiency.

Real-time monitoring energy efficiency and performance degradation of condensing boilers

Condensing boilers achieve higher efficiency than traditional boilers by using waste heat in flue gases to preheat cold return water entering the boiler. Water vapor produced during combustion is condensed into liquid form, thus recovering its latent heat of vaporization, leading to around 10–12% increased efficiency. Many countries have encouraged the use of condensing boilers with financial incentives. It is thus important to develop software tools to assess the correct functioning of the boiler and eventually detect problems. Current monitoring tools are based on boiler static maps and on large sets of historical data, and are unable to assess timely loss of performance due to degradation of the efficiency curve or water leakages. This work develops a set of fault detection and diagnosis tools for dynamic energy efficiency monitoring and assessment in condensing boilers, i.e. performance degradation and faults can be detected using real-time measurements: this real-time feature is particularly relevant because of the limited amount of data that can be stored by state-of-the-art building energy management systems. The monitoring tools are organized as follows: a bimodal parameter estimator to detect deviations of the efficiency of the boiler from nominal values in both condensing and noncondensing mode; a virtual sensor for the estimation of the water mass flow rate; filters to detect actuator and sensor faults, possibly due to control and sensing problems. Most importantly, structural properties for detection and isolation of actuators and sensing faults are given: these properties are crucial to understand which faults can be diagnosed given the available measurements. The effectiveness of these tools is verified via extensive simulations.

Experimental Study on the Combustion System Optimization in the Case of a 36 kW Condensing Boiler

The Energy-related Products Directive that came into force in all EU countries on September 25, 2015 is focusing attention on the condensing boilers more than ever before since they currently represent the most advanced and environmental friendly heating technology based on fossil fuels. In this context, an experimental study referring to the combustion system of a condensing system of 36 kW nominal heat output - defined in central heating mode and condensing regime - was developed. The analyzed condensing system is of premixed type, consisting of an air blower, a gas valve, a fuel gas-air mixer and a cylindrical multihole burner. Beside nominal heat output, another important requirement is a wide heat output range, for flexibility relative to the load. Consequently, the minimum heat output of the boiler should be as low as possible. This problem of maximum and minimum heat output of the boiler is, in fact, a question of maximum and minimum air flow that enters in the combustion system, which is decided by minimum aria of nozzle of the fuel gas-air mixer. In order to establish the optimum solution for the analyzed combustion system, four fuel gas-air mixers, Siemens type, had been experimented. The paper presents the results of this study.

Polymer heat exchanger design for condensing boiler applications

Condensing boilers achieve very high efficiency levels by recovering both sensible heat and water vapor latent heat from the flue gas. Research since the 1980's has focused on corrosion in such condensing heat exchangers related to the acidic condensate and material selection. Polymers in condensing heat exchangers have been considered to avoid the cost and corrosion concerns of metallic designs. Past efforts have shown that polymers offer the advantage of corrosion resistance and cost, however, lower thermal conductivity limited their application. More recent developments have introduced thermally conductive polymers which now offer promising conductivity values. This project focused on the evaluation of a thermally conductive polymer heat exchanger for this application.Computational fluid dynamic results indicated thermal conductivity values of stainless steel, a typical heat exchanger material, do not need to be achieved for similar heat transfer performance. An increase in thermal conductivity from about 10 times that of the base polymer can achieve an overall heat exchanger effectiveness similar to that achieved with stainless steel. A polymer composite thermal conductivity of approximately 2.5 W/m⋅K would be adequate. Thermally conductive polymer materials are now commercially available which offer values up to 20 W/m⋅K. In this work, one Nylon-12 and one thermally conductive polymer composite heat exchanger prototypes were constructed for a condensing boiler application. Tests demonstrated that good overall heat transfer performance was achieved. The lower thermal conductivity of the polymer heat exchanger will lead to higher surface temperatures and lower water condensation rates.

A Novel Modelling Approach for Condensing Boilers Based on Hybrid Dynamical Systems

Condensing boilers use waste heat from flue gases to pre-heat cold water entering the boiler. Flue gases are condensed into liquid form, thus recovering their latent heat of vaporization, which results in as much as 10%–12% increase in efficiency. Modeling these heat transfer phenomena is crucial to control this equipment. Despite the many approaches to the condensing boiler modeling, the following shortcomings are still not addressed: thermal dynamics are oversimplified with a nonlinear efficiency curve (which is calculated at steady-state); the dry/wet heat exchange is modeled in a fixed proportion. In this work we cover these shortcomings by developing a novel hybrid dynamic model which avoids the static nonlinear efficiency curve and accounts for a time-varying proportion of dry/wet heat exchange. The procedure for deriving the model is described and the efficiency of the resulting condensing boiler is shown.

Which Is Greener? The Gas Condenser Boiler Or Ground Source Heat Pump. Which Is The Contribution Of Renewable Energy To The Energy Consumption For Heating To A Building?

Abstract The goals of this paper are: to estimate the carbon emission reduction on energy efficiency measurements in a laboratory building in Transilvania University from Braşov, Romania, in accordance with the European Directive 2009/28/EC and to estimate the contribution of renewable energy to energy efficiency of the building using the performance indicator named Renewable Energy Ratio - RER. We will detail the methods of calculation for CO2 emissions and we will present the results for gas condensing boiler, and ground source heat pump for the laboratory building. The results show that conventional energy efficiency technologies and renewable energy technologies can be used to decrease CO2 emissions in buildings by 20–30% on average and up to over 40% for some building types and locations. The contribution of renewable energy is between 40 and 50 % from total energy use and only for heating is 58%. This value could rise to 0.63 if we apply to electricity produced by photovoltaic panels.

Financial and economic analysis for ground-coupled heat pumps using shallow ground heat exchangers

A discounted cash flow analysis (DCFA) and a cost-benefit analysis (CBA) have been implemented in order to investigate the economic aspects of ground-coupled heat pump (GCHP) for space heating and cooling, in comparison to traditional condensing boiler (CB). The DCFA allows the analysis of investment costs, operating costs and savings of the two different systems in order to understand if the GCHP's payback periods (PBPs) are more interesting than that of CB in coming years. The first financial model (DCFA) takes account for economic factors as prices, costs and growth, while the economic approach (CBA) includes the carbon price into the calculation, considering the social costs of carbon dioxide emissions.The whole analysis is implemented to adopting a parametric approach, in which all the economic terms are linked to energy labels, degree-days and energy mix ratios (EMRs), the latter obtained as the ratio between the cost of electricity and natural gas paid by the householder. Relating to different EMRs, the PBPs are presented in matrices in which energy labels and degree-days are the row/column indexes, to confront the benefits of choosing between GCHP and CB. The PBPs are also calculated with the introduction of the carbon price so that some considerations about the environmental aspects are presented. The results show that all higher energy labels have a good profitability ratio between costs and payback periods and demonstrate that GCHP system does pay off.