| | SLO | ENG | Cookies and privacy

Bigger font | Smaller font

Search the digital library catalog Help

Query: search in
search in
search in
search in
* old and bologna study programme

Options:
  Reset


1 - 6 / 6
First pagePrevious page1Next pageLast page
1.
Influence of water scale on thermal flow losses of domestic appliances
Danijela Urbancl, Darko Goričanec, 2007, original scientific article

Abstract: Research results of how the precipitated water scale on heaters of small domestic appliances influences the consumption of electricity are presented. It shows that the majority of water scale samples are composed of aragonite, calcite and dolomite and that those components have an extraordinary low thermal conductivity. Also, the results show that at 2 mm thick deposit, depending on the chemical composition of water scale, the thermal flow is reduced for 10% to 40%; consequently, the consumption of electricity significantly increases.
Keywords: electricity, heat transfer, heat flow, heat exchanger, water scale
Published: 31.05.2012; Views: 1237; Downloads: 43
URL Link to full text

2.
Response functions and thermal influence for various multiple borehole configurations in ground coupled heat pump systems
Metka Pešl, Darko Goričanec, 2007, original scientific article

Abstract: Ground coupled heat pump (GCHP) utilizes the immense renewable storage capacity of the ground as a heat source or sink to provide space heating, cooling, and domestic hot water. GCHP systems are generally comprised of watersource heat pumps and ground heat exchangers (GHEs). Consisting of closedloop of pipes buried in boreholes, ground heat exchangers (GHEs) are devised for extraction or injection of thermal energy from/into the ground. Despite the low energy and lower maintenance benefits of ground-source heat pump systems, little work has been undertaken in detailed analysis. Many models, either numerical or analytical, have been proposed to analyze the thermal response of vertical heat exchangers that are used in ground coupled heat pump systems (GCHP). In both approaches, most of the models are valid after few hours of operation since they neglect the heat capacity of the borehole. In this paper, we present for three various multiple borehole configurations a comparison between g-functions, which will be calculated after an analytical model of final line source and g-functions, obtain with numerical model derived from the work of Eskilson. A case study is presented to show how the ground temperature changes with time for various multiple borehole configurations.
Keywords: geothermal heat exchanger, heat transfer, heat conduction, thermal influence
Published: 31.05.2012; Views: 1109; Downloads: 24
URL Link to full text

3.
Economic analysis of geothermal heat source for residential area project
Sašo Poberžnik, Darko Goričanec, Jurij Krope, 2007, original scientific article

Abstract: The article discusses the economic analysis of heat source for residential area project. The energy source is geothermal energy. Every house has its own borehole heat exchanger (BHE) and heat pump in basement. In this system low temperature floor and wall heating was carried out. The economic analysis was performed as a pilot study for real system with all installation needed to runthe system. The analysis has been done using the method of the net present value. In the research the coefficient of profitability and the period of timein which the investment is going to return itself were established. The system has been compared to the conventional system that uses fossil fuel (Liquidized naphtha gas- LNG) to heat the building and domestic hot water.
Keywords: geothermal heat, area projects, borehole heat exchanger, economic analysis
Published: 31.05.2012; Views: 986; Downloads: 24
URL Link to full text

4.
SYNTHESIS OF PROCESSES AND PROCESS SUBSYSTEMS FOR ENTIRE LIFETIME
Andreja Nemet, 2015, doctoral dissertation

Abstract: Economically viable process designs should be, in addition to other criteria, profitable over their entire process lifetimes not only at the present time. An improved process design can be achieved by establishing an appropriate trade-off between product income, raw material, operating costs, and investment. The full lifetime of the processes and future prices have to be considered rather than optimising them on a yearly basis using current prices. Single-period optimisation and synthesis models for processes reflects current prices only. The prices can fluctuate rather quickly and the optimal solution may be very different from one year to the another. Therefore, the traditional superstructural synthesis approach applying a mixed-integer nonlinear programming model was upgraded: i) over time, by considering an entire lifetime, which can be described by a multi-period model and ii) the whole field of variation regarding uncertain future prices. A stochastic approach considering the statistical distribution of price projections over an entire lifetime was used on different case studies instead of the traditional deterministic approach accounting for nominal future price projection. The objective was the maximisation of the expected net present value of a process or the expected incremental net present value of different process subsystem. The heat exchanger network has been one of the subsystem, which can significantly contribute to operating costs due to savings of external utility consumption. For this subsystem a deterministic and stochastic multi-period mixed-integer nonlinear programming (MINLP) synthesis models have been developed in order to account for future price projections. Considering higher energy prices gives rise to larger initial investments compared to solutions obtained with current prices. However, due to the uncertainties of utility prices' forecasts, retrofitting using an extension of HEN during future years of the lifespan might be a better strategy. The objective is to identify a design that is the most suitable for effective future extensions and preferably with the lowest sensitivity to energy price fluctuations, as there can be various designs featuring similar initial investment. The results supports that it is economically beneficial to consider future utility prices as the incremental investment is not only paid-off but additional savings are achieved. Process-to-process Heat Integration can also significantly affect the trade-off between investment and operating cost. The aim of Total Site (TS) HEN synthesis was to develop a model synthesis for the TS that, besides many other important features, would also consider future utility prices. Two strategies for TS synthesis have been developed: i) sequential, when HI is performed within a process during the first step and then after a process-to-process HI has been performed, and ii) simultaneous, where the HI is performed within and between processes simultaneously. The second strategy can reveal additional opportunities for heat recovery that might not be identified when applying the first strategy. Comparison of the results obtained at consideration of current utility prices and forecasted utility prices indicates that is worth to account for future utility prices. The separation processes also consume a significant amount of energy. The synthesis of a distillation column sequence integrated within its heat exchanger network was used as a case study for the separation of a multi-component stream into pure component products by considering future utility prices. This analysis has been performed in order to evaluate the magnitude of the influence of forecasted utility prices. It can be concluded that forecasted utility prices can be beneficial, however, the technical limits of the systems should be carefully observed. The price fluctuation can also be observed for other prices not only utility prices, e.g. raw material cost, product price, etc
Keywords: future prices, forecasted prices, stochastic optimisation, mathematical programming, Heat Exchanger Network, Total Site, distillation column sequence, methanol production
Published: 04.05.2015; Views: 871; Downloads: 80
.pdf Full text (4,74 MB)

5.
Fault detection of an industrial heat-exchanger
Dejan Dragan, 2011, original scientific article

Abstract: One of the key issues in modelling for fault detection is how to accommodate the level of detail of the model description in order to suit the diagnostic requirements. The paper addresses a two-stage modelling concept to an industrial heat exchanger, which is located in a tyre factory. Modelling relies on combination of prior knowledge and recorded data. During the identification procedure, the estimates of continuous model parameters are calculated by the least squares method and the state variable filters (SVF). It is shown that the estimates are largely invariant of the bandwidth of the SVFs. This greatly reduces the overall modelling effort and makes the whole concept applicable even to less experienced users. The main issues of the modelling procedure are stressed. Based on the process model a simple detection system is derived. An excerpt of the results obtained on operating records is given.
Keywords: industrijski prenosniki toplote, zaznavanje napak, nadzor procesov, odkrivanje napak na osnovi modela, modeliranje, identifikacija, industrial heat exchanger, fault detection, condition monitoring, model-based detection, modelling, identification
Published: 10.07.2015; Views: 719; Downloads: 7
URL Link to full text

6.
Direct enthalpy exchange between process utilities
Zorka Novak-Pintarič, Peter Glavič, 2002, professional article

Abstract: This paper presents an application of the improved pinch methodology by performing a simplified exergy analysis in a real-size ammonia plant. Besides the well known pinch technics like composite curves and grand composite curve, the improved approach with the extended grand composite curve was implemented. The latter presents the most energy intensive units in the process separated from the process background as well as the direct transfer of enthalpy from hot utilities to cold utilities. Based on this presentation the synthesis of modified heat exchanger network was performed which results in considerable decrease of utilities demand.
Keywords: chemical engineering, process design, exergy analysis, ammonia plant, pinch methodology, extended hrand composite curve method, enthalpy exchange, distillation column, heat exchanger network
Published: 10.07.2015; Views: 667; Downloads: 35
.pdf Full text (182,17 KB)
This document has many files! More...

Search done in 0.09 sec.
Back to top
Logos of partners University of Maribor University of Ljubljana University of Primorska University of Nova Gorica