Applied sciences

Archives of Thermodynamics

Content

Archives of Thermodynamics | 2011 | No 3 December |

Abstract

The paper presents results of research focused on modelling heat storage tank operation used for forecasting purposes. It presents selected issues related to mathematical modelling of heat storage tanks and related equipment and discusses solution process of the optimisation task. Presented detailed results were obtained during real-life industrial implementation of the optimisation process at the Siekierki combined heat and power (CHP) plant in Warsaw owned by Vattenfall Heat Poland S.A. (currently by Polish Oil & Gas Company - PGNiG SA) carried out by the Academic Research Centre of Power Industry and Environment Protection, Warsaw University of Technology in collaboration with Transition Technologies S.A. company.

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Abstract

Microscale combined heat and power (CHP) unit based on solid oxide fuel cells (SOFC) for distributed generation was analyzed. Operation principle is provided, and the technology development in recent years is briefly discussed. System baseline for numerical analysis under steady-state operation is given. Grid-connected unit, fuelled by biogas corresponds to potential market demand in Europe, therefore has been selected for analysis. Fuel processing method for particular application is described. Results of modeling performed in ASPEN Plus engineering software with certain assumptions are presented and discussed. Due to high system electrical efficiency exceeding 40%, and overall efficiency over 80%, technology is an example of highly competitive and sustainable energy generation unit.

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Abstract

Anti-condensation coatings are widely used in refrigeration, air conditioning and ships technology. They can store a certain amount of water in its own volume, and then return it back in favorable conditions. Anti-condensation coatings are used also to protect structures from the moisture. This paper presents the results of experimental research on heat and mass transfer in an anti-condensation coating under natural and forced convection. Experimental results are obtained for horizontal and inclined plates. Experimental data are compared with different models of computation.
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Abstract

In the paper presented is a novel concept to utilize the heat from the turbine bleed to improve the quality of working fluid vapour in the bottoming organic Rankine cycle (ORC). That is a completely novel solution in the literature, which contributes to the increase of ORC efficiency and the overall efficiency of the combined system of the power plant and ORC plant. Calculations have been accomplished for the case when available is a flow rate of low enthalpy hot water at a temperature of 90 °C, which is used for preliminary heating of the working fluid. That hot water is obtained as a result of conversion of exhaust gases in the power plant to the energy of hot water. Then the working fluid is further heated by the bleed steam to reach 120 °C. Such vapour is subsequently directed to the turbine. In the paper 5 possible working fluids were examined, namely R134a, MM, MDM, toluene and ethanol. Only under conditions of 120 °C/40 °C the silicone oil MM showed the best performance, in all other cases the ethanol proved to be best performing fluid of all. Results are compared with the "stand alone" ORC module showing its superiority.
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Abstract

The paper presents the results of optimizing the coefficient of the share of cogeneration expressed by an empirical formula dedicated to designers, which will allow to determine the optimal value of the share of cogeneration in contemporary cogeneration systems with the thermal storages feeding the district heating systems. This formula bases on the algorithm of the choice of the optimal coefficient of the share of cogeneration in district heating systems with the thermal storage, taking into account additional benefits concerning the promotion of high-efficiency cogeneration and the decrease of the cost of CO2 emission thanks to cogeneration. The approach presented in this paper may be applicable both in combined heat and power (CHP) plants with back-pressure turbines and extraction-condensing turbines.
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Abstract

The installations of CO2 capture from flue gases using chemical absorption require a supply of large amounts of heat into the system. The most common heating medium is steam extracted from the cycle, which results in a decrease in the power unit efficiency. The use of heat needed for the desorption process from another source could be an option for this configuration. The paper presents an application of gas-air systems for the generation of extra amounts of energy and heat. Gas-air systems, referred to as the air bottoming cycle (ABC), are composed of a gas turbine powered by natural gas, air compressor and air turbine coupled to the system by means of a heat exchanger. Example configurations of gas-air systems are presented. The efficiency and power values, as well as heat fluxes of the systems under consideration are determined. For comparison purposes, the results of modelling a system consisting of a gas turbine and a regenerative exchanger are presented.
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Abstract

A new method for measurement of local heat flux to water-walls of steam boilers was developed. A flux meter tube was made from an eccentric tube of short length to which two longitudinal fins were attached. These two fins prevent the boiler setting from heating by a thermal radiation from the combustion chamber. The fins are not welded to the adjacent water-wall tubes, so that the temperature distribution in the heat flux meter is not influenced by neighbouring water-wall tubes. The thickness of the heat flux tube wall is larger on the fireside to obtain a greater distance between the thermocouples located inside the wall which increases the accuracy of heat flux determination. Based on the temperature measurements at selected points inside the heat flux meter, the heat flux absorbed by the water-wall, heat transfer coefficient on the inner tube surface and temperature of the water-steam mixture was determined.
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Abstract

The paper presents a thermomechanical computational solid mechanics analysis (CSM) of a pipe "double omega", used in the steam superheaters in circulating fluidized bed (CFB) boilers. The complex cross-section shape of the "double omega" tubes requires more precise analysis in order to prevent from failure as a result of the excessive temperature and thermal stresses. The results have been obtained using the finite volume method for transient state of superheater. The calculation was carried out for the section of pipe made of low-alloy steel.
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Abstract

The paper presents a thermal-economic analysis of a 900 MW coal-fired power unit for ultra-supercritical parameters with internal steam reheat. The subject of the study was the cycle proposed as the "initial thermal cycle structure" during the completion of the project "Advanced Technologies for Energy Generation" with the steam parameters of 650/670 °C/30 MPa. Two configurations of internal reheat were analysed: with a four- and seven-section exchanger. The effect of reheat on the operation of the power unit under a partial load was also analysed, and preliminary calculations of the heat exchange area of the internal reheat were made.
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Abstract

The direct carbon fuel cell technology provides excellent conditions for conversion of chemical energy of carbon-containing solid fuels directly into electricity. The technology is very promising since it is relatively simple compared to other fuel cell technologies and accepts all carbon-reach substances as possible fuels. Furthermore, it makes possible to use atmospheric oxygen as the oxidizer. In this paper the results of authors' recent investigations focused on analysis of the performance of a direct carbon fuel cell supplied with graphite, granulated carbonized biomass (biocarbon), and granulated hard coal are presented. The comparison of the voltage-current characteristics indicated that the results obtained for the case when the cell was operated with carbonized biomass and hard coal were much more promising than those obtained for graphite. The effects of fuel type and the surface area of the cathode on operation performance of the fuel cell were also discussed.
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Abstract

The paper presents heat transfer calculation results concerning a control rod of Forsmark Nuclear Power Plant (NPP). The part of the control rod, which is the object of interest, is surrounded by a mixing region of hot and cold flows and, as a consequence, is subjected to thermal fluctuations. The paper describes a numerical test which validates the method based on the solution of the inverse heat conduction problem (IHCP). The comparison of the results achieved by two methods, computational fluid dynamics (CFD) simulations and IHCP, including a description of the IHCP method used in the calculation process, shows a very good agreement between the methods.
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Abstract

The paper is concerned with an important issue from the field of thermoacoustics - the numerical modelling of the flow field in the thermoacoustic engine. The presented way of modelling is based on the solution to fundamental fluid mechanics equations that govern the flow of compressible, viscous, and heat-transferring gas. The paper presents the way of modelling the thermoacoustic engine, the way of conducting calculations and the results which illustrate the correctness of the selected computational technique.
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Abstract

The following paper presents the method for solving one-dimensional inverse boundary heat conduction problems. The method is used to estimate the unknown thermal boundary condition on inner surface of a thick-walled Y-branch. Solution is based on measured temperature transients at two points inside the element's wall thickness. Y-branch is installed in a fresh steam pipeline in a power plant in Poland. Determination of an unknown boundary condition allows for the calculation of transient temperature distribution in the whole element. Next, stresses caused by non-uniform transient temperature distribution and by steam pressure inside a Y-branch are calculated using the finite element method. The proposed algorithm can be used for thermal-strength state monitoring in similar elements, when it is not possible to determine a 3-D thermal boundary condition. The calculated temperature and stress transients can be used for the calculation of element durability. More accurate temperature and stress monitoring will contribute to a substantial decrease of maximal stresses that occur during transient start-up and shut-down processes.
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Abstract

Temperature related decrease of steam turbine components is one of the main transient processes that occur during a typical long-term operation. With a natural cooling (no user interference) it takes more than 14 days before the temperature of components reaches the level that allows to open and repair a turbine. It is then reasonable to apply a forced cooling in order to decrease the time between a shut-down of a power generating unit and a beginning of a repair. This paper presents the analysis of application of a forced cooling process to supercritical steam turbines. The main problems under the investigation are the safety issues of the process and the optimization of cooling conditions. The paper describes the safety restrictions and the optimization criteria. The process is analyzed in numerical simulations conducted for various cooling conditions.
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Abstract

For the optimal location of an additional surplus measurements in the design of redundant measurements system, from data reconciliation point of view, of thermal processes, an information entropy has been applied. The relative entropy - Kullback-Leibler divergence, has been used. As a criterion of the optimal location of an additional surplus measurements in a system of measurements data, the minimum of the entropy information of reconciled measurements data has been assumed. Hence, the objective function in the described optimization task is maximum of the relative entropy - Kullback-Leibler divergence concerning sets of raw and reconciled measurements data. Simulation calculation with application of data reconciliation algorithm and Monte Carlo method concerning the influence of installation of the additional surplus measurements on decrease of entropy information of measurements after data validation have been carried out. The example calculations concerned the cross high-pressure heat regeneration system with cascade flow of condensate installed in 153 MW power unit equipped with cooler of steam are presented. Calculations for all variants of configurations of an additional surplus measurements in the analyzed thermal system have been done. Usefulness of the proposed Kullback-Leibler divergence as a objective function has been demonstrated.
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Abstract

The paper presents a thermal-economic analysis of different variants of a hard coal-fired 900 MW ultra-supercritical power unit. The aim of the study was to determine the effect of the parameters of live and reheated steam on the basic thermodynamic and economic indices of the thermal cycle. The subject of the study was the cycle configuration proposed as the "initial thermal cycle structure" during the completion of the project "Advanced Technologies for Energy Generation" with the live and reheated steam parameters of 650/670 °C. At the same time, a new concept of a thermal cycle for ultra-supercritical parameters with live and reheated steam temperature of 700/720 °C was suggested. The analysis of the ultra-supercritical unit concerned a variant with a single and double steam reheat. All solutions presented in the paper were subject to a detailed thermodynamic analysis, as well as an economic one which also included CO2emissions charges. The conducted economic analysis made it possible to determine the maximum value of investment expenditures at which given solutions are profitable.
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Abstract

The paper presents proposal of a model of the fluidized bed boiler adapted for use in model-based controllers e.g. predictive, adaptive or internal model control (IMC). The model has been derived in the form of transfer function matrix which allows its direct implementation in the controller structure. Formulated model takes into consideration the principal cross-coupling between process variables which enables the opportunity to search for feasibility of decoupling control. The results of the identification of the dynamics of the 2 MW industrial bubbling fluidized bed boiler using the proposed model form was presented. According to the experimental data it was found that despite of introduced simplifications presented model allows the boiler behavior prediction.
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Abstract

Optimization of vane positions in a mechanical draft wet-cooling tower is presented in this paper. The originally installed, equally spaced, vanes produced non-uniform air velocity distribution reducing the performance of the fill of the cooling tower. A 2D CFD model of the tower has been created. The model has then been used to determine the objective function in the optimization procedure. The selected objective function was the standard deviation of the velocity of air entering the fill. The Goal Driven Optimization tools of the ANSYSWorkbench 2.0 have been used for the optimization and the ANSYS Fluent 13.0 as a flow solver. The optimization allowed reduction of the objective function and producing a more uniform air flow.
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Editorial office

Honorary Editor
Wiesław Gogół, Warsaw University of Technology, Poland

Editor-in-Chief
Jarosław Mikielewicz, The Szewalski Institute of Fluid-Flow Machinery PAS, Poland

Deputy
Marian Trela, The Szewalski Institute of Fluid-Flow Machinery PAS, Poland

Members of Editorial Commitee
Roman Domanski, Warsaw University of Technology, Poland
Andrzej Ziębik, Technical University of Silesia, Poland

Managing Editor
Jarosław Frączak, The Szewalski Institute of Fluid-Flow Machinery PAS, Poland

International Advisory Board
J. Bataille, Ecole Central de Lyon, Ecully, France
A. Bejan, Duke University,  Durham, USA
W. Blasiak, Royal Institute of Technology,  Stockholm, Sweden
G. P. Celata, ENEA,  Rome, Italy
M. W. Collins, South Bank University,  London, UK
J. M. Delhaye, CEA, Grenoble, France
M. Giot, Université Catholique de Louvain, Belgium
D. Jackson, University of Manchester, UK
S. Michaelides, University of North Texas, Denton, USA
M. Moran, Ohio State University,  Columbus, USA
W. Muschik, Technische Universität, Berlin, Germany
I. Müller, Technische Universität, Berlin, Germany
V. E. Nakoryakov, Institute of Thermophysics, Novosibirsk, Russia
M. Podowski, Rensselaer Polytechnic Institute, Troy, USA
M.R. von Spakovsky, Virginia Polytechnic Institute and State University, Blacksburg, USA

Contact

IFFM Publishers (Wydawnictwo IMP),

The Szewalski Institute of Fluid-Flow Machinery,
Fiszera 14, 80-952 Gdańsk, Poland,
telephone: +48 58 6995141, fax: +48 58 3416144,
e-mail: jfrk@imp.gda.pl; now@imp.gda.pl

 

 

Instructions for authors

Archives of Thermodynamics publishes original papers which have not previously appeared in other journals. The language of the papers is English. No paper should exceed the length of 25 pages. All pages should be numbered. The plan and form of the papers should be as follows:
 

1. The heading should specify the title (as short as possible), author, his/her complete affiliation, town, zip code, country and e-mail. Please show the corresponding author. The heading should be followed by Abstract of maximum 15 typewritten lines.

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`2` Rizzo F.I., Shippy D.I.: A method of solution for certain problems of transient heat conduction.
AIAA Journal 8(1970), No. 11, 2004–2009.
 
9. As the papers are published in English, the authors who are not native speakers of English are obliged to have the paper thoroughly reviewed language-wise before submitting for publication.

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