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This paper presents a numerical and experimental study of a heating system that consists of hot air generator driven by biomass pellet burner to drive the NH3-water absorption heat pump made by Robur. The aim of this work is to fully test the system of hot air generator for thermal potential, by developing a thermal field, while driving the absorption heat pump of medium capacities for residential purposes, and to make model of predicting the efficiencies of heating comparing to conveyed heat in desorber of absorption heat pump. Numerical simulations of the hot air generator were performed in the commercial software ANSYS FLUENT and CFX. The experimental part was carried out in the laboratory of the Faculty of Mechanical Engineering in Niš, where the temperature and velocity measurements were obtained and compared to numerical results. Results were obtained for mass air-flow through the hot air generator and desorber of 0.17 and 0.2552 kg/s, pellet burner power of 15 kW, 18 kW, 21 kW, 24 kW, 27 kW, and 30 kW, with air inlet temperature in desorber of around 89-140 °C. The heating efficiency of the absorption heat pump goes from 1.01 to 1.37. The heat loss over the surfaces of hot air generator goes from 0.6-0.9 kW depending on ambient air and surface temperatures. The system has the potential to be applied in low temperature heating and the spare heat from combustion products and residual hot air can be used for different purposes. [ABSTRACT FROM AUTHOR]

In engineering practice exergy can be used for technical and economic optimization of energy conversion processes. The problem of increasing energy consumption suggests that heating plants, i.e. hot water boilers, as energy suppliers for household heating should be subjected to exergy and energy analysis. Heating plants are typically designed to meet energy demands, without the distinguished difference between quality and quantity of the produced heat. In this paper, the energy and exergy analysis of a gas fired hot water boiler is conducted. Energy analysis gives only quantitative results, while exergy analysis provides an insight into the actually available useful energy with respect to the system environment. In this paper, a hot water boiler was decomposed into control volumes with respect to its functional components. Energy and exergy of the created physical model of the hot water boiler is performed and destruction of exergy and energy loss in each of the components is calculated. The paper describes the current state of energy and exergy efficiency of the hot water boiler. The obtained results are analyzed and used to investigate possibilities for improvement of availability and reliability of the boiler. A comparison between the actual and the proposed more reliable solution is made.

Boilers are one of the most used units for both heat generation plants and industry systems. Their operation is subjected to different working loads and maintenance requirements. Exploitation experience points out critical boiler zones where failures and break downs typically occur. This paper analyzes critical zones in hot water fire-tube boiler. Experimental procedure was performed on the model of this type of boilers and its critical element. The tube plate of hot water boiler was identified as the most critical one. Experimental analysis and numerical model verification were performed using Aramis system based on 3-D digital image correlation method. Numerical analysis was done in ANSYS software package and verification of results was done based on measurements obtained by strain gauges and local measurements performed by the Aramis system. Stress-strain analysis indicates the critical zones of boiler tube plate. The character of change parameters such as strain and stress occurring in the critical zones can be verified both by experimental and numerical data. The paper presents a novel approach in experimental and numerical analyses that can be conducted in similar units and used for existing unit optimization, as well as for new product testing on different loads and provide opportunity for further development and improvement for practical industrial application. [ABSTRACT FROM AUTHOR]

A polygeneration system is an energy system capable of providing multiple energy outputs to meet local demands, by application of high process integration. In this paper, optimal configuration and capacity of a polygeneration system for an indoor swimming pool building is determined by application of a method based on TRNSYS simulation and GenOpt optimization software. Based on the applicability, a superstructure of the polygeneration system is integrated, consisting of the following polygeneration modules: an internal combustion engine cogeneration module, a vapor compression chiller, and adsorption chiller, a ground source heat pump, flat plate solar thermal collectors, photovoltaic collectors, and heat storage. Annual behavior of energy loads of the public swimming pool building during a typical meteorological year and the polygeneration system are modeled and simulated using TRNSYS software, whereas techno-economic optimization is performed by GenOpt optimization. The results indicated the optimal configuration of the polygeneration system for the modelled energy demands, as well as the optimal capacity of the polygeneration modules, thus defining the optimal capacity of the polygeneration system for the energy demands of the public swimming pool building. [ABSTRACT FROM AUTHOR]

Exploitation experience of hot water boiler plants indicates relatively frequent and permanent breakdowns resulting from the accident state of various elements of the boiler. In addition to the damages caused by the corrosion processes and inadequate management of the plant, the phenomena of fatigue of boiler elements exposed to high pressures and temperatures can occur. Due to high pressure and temperature certain boiler elements are exposed to, high strain and stress of these elements can eventually lead to breakdowns. In this paper, a hot water fire tube boiler, produced by "Minel-Kotlogradnja" Belgrade, type TE110V, installed within the plant "Technical Faculties" at Faculty of Mechanical Engineering in Nis, Serbia, is analyzed. Thermomechanical stress-strain analysis is performed with loads typically occurring during operation. Finite element analysis is performed using ANSYS Workbench 17 Software package, while the CAD model is formed using SOLID WORKS 2015. The results were used to investigate and to give recommendations for the thickness of tube plate of the first reversing chamber based on determined functional dependence of equivalent stress in the tube plate from the thickness of the plate. The noted functional dependence was determined by Kriging response surface based on results of virtual numerical experiment with different thicknesses of the tube plate. [ABSTRACT FROM AUTHOR]

Buildings with indoor swimming pools have a large energy footprint. The source of major energy loss is the swimming pool hall where air humidity is increased by evaporation from the pool water surface. This increases energy consumption for heating and ventilation of the pool hall, fresh water supply loss and heat demand for pool water heating. In this paper, a mathematical model of the swimming pool was made to assess energy demands of an indoor swimming pool building. The mathematical model of the swimming pool is used with the created multi-zone building model in TRNSYS software to determine pool hall energy demand and pool losses. Energy loss for pool water and pool hall heating and ventilation are analyzed for different target pool water and air temperatures. The simulation showed that pool water heating accounts for around 22%, whereas heating and ventilation of the pool hall for around 60% of the total pool hall heat demand. With a change of preset controller air and water temperatures in simulations, evaporation loss was in the range 46-54% of the total pool losses. A solar thermal sanitary hot water system was modelled and simulated to analyze it's potential for energy savings of the presented demand side model. The simulation showed that up to 87% of water heating demands could be met by the solar thermal system, while avoiding stagnation. [ABSTRACT FROM AUTHOR]

The paper presents an application of the finite elements method for stress and strain analysis of the hot water boiler structure. The aim of the research was to investigate the influence of the boiler scale on the thermal stresses and strains of the structure of hot water boilers. Results show that maximum thermal stresses appear in the zone of the pipe carrying wall of the first reversing chamber. This indicates that the most critical part of the boiler are weld spots of the smoke pipes and pipe carrying plate, which in the case of significant scale deposits can lead to cracks in the welds and water leakage from the boiler. The non-linear effects were taken into account by defining the bilinear isotropic hardening model for all boiler elements. Temperature dependency was defined for all relevant material properties, i. e. isotropic coefficient of thermal expansion, Young’s modulus, and isotropic thermal conductivity. The verification of the FEA model was performed by comparing the measured deformations of the hot water boiler with the simulation results. As a reference object, a Viessmann-Vitomax 200 HW boiler was used, with the installed power of 18.2 MW. CAD modeling was done within the Autodesk Inventor, and stress and strain analysis was performed in the ANSYS software. [ABSTRACT FROM AUTHOR]

This paper presents a new approach in mathematical modeling of thermodynamic cycles and electric power of utility district-heating and co-generation steam turbines. The approach is based on the application of the dimensionless mass flows, which describe the thermodynamic cycle of a combined heat and power steam turbine. The mass flows are calculated relative to the mass flow to low pressure turbine. The procedure introduces the extraction mass flow load parameter ?h which clearly indicates the energy transformation process, as well as the co-generation turbine design features, but also its fitness for the electrical energy system requirements. The presented approach allows fast computations, as well as direct calculation of the selected energy efficiency indicators. The approach is exemplified with the calculation results of the district heat power to electric power ratio, as well as the cycle efficiency, vs. ?h. The influence of ?h on the conformity of a combined heat and power turbine to the grid requirements is also analyzed and discussed. [ABSTRACT FROM AUTHOR]