EXERGY ANALYSIS OF TWO-STAGE WATER TO WATER HEAT PUMP

The paper presents an exergy analysis of the selected two-stage compression water to water heat pump system in heating mode of operation. The foreseen heat source is underground water of constant temperature level. The characteristic exergy values are calculated for the ambient temperature 0 [oC] and ambient pressure 100 kPa. In addition, values of exergy losses, exergy efficiency, exergy loss ratio, exergy loss coefficient and exergy effectiveness (degree of thermodynamic ideality) are also calculated and analyzed. The objective to indicate components and working conditions with increased exergy losses was fulfilled and the obtained results should provide guidance for design and optimization of heat pumps that operate with underground water and are used for water heating applications

Hydrogeological zoning as a basis for hydrogeological heritage zoning distinguishing through example of the territory of Serbia

Correct approach to defining and protection of hydrogeological heritage of Serbia, in the author's opinion, is in a hierarchical series hydrogeological units distinguishing, not only with specific relations of some rock categories expressed, but also with groundwater accumulated in standard permeable media and their discharge through various outcrops. So, in the next stage, for each of the first-order units, selection and ranking of the lower-order interesting hydrogeological units, standard water-bearing formations and characteristic hydrogeological profiles is significantly simplified, and, finally makes a choice of objects (phenomena) characterizing some hydrogeological units easier. As a base for hydrogeological zoning, valud geotectonic classification of the territory of Serbia was used, because the first-order distinguished geotectonic units are characterized by: specific geological composition (columnar section), structural fabric and specific geomorphological and hydrogeological features. Aim of the paper is to perform a review of basic characteristics of such separated units and to direct attention to some lower-order hydrgeological units, water-bearing formations and groundwater occurrences within, interesting from aspects of geological heritage protection. It can be concluded that geotectonic, in other words, hydrogeological zoning of the territory of Serbia, takes important place in strategy of defining hydrogeological heritage to be protected. Further working out of the matter requires contributions of numerous hydrogeologists, experts in some areas within Serbia, as well as coordinating according to some (common) objects with specialities from other fields of the natural sciences (geomorphologists, hydrologists, speleologists, etc). During the initial stage, besides issuing of criteria for hydrogeological objects ranking, modern systematics of geological heritage objects has to be made, according to which fields of work these disciplines would be stated precisely

Energetic and environmental sustainability of sub-geothermal heat pump heating in Serbia

Feasibility of low enthalpy geothermal waters incorporation in Serbian energy source structure has been investigated. Energy potential of ground waters of modest temperature levels is usually neglected since they can not be used for direct heating purposes. Nevertheless, if an appropriate heat pump system is utilised, as described in the paper, energy efficient and environmental friendly heating could be achieved. From the environmental aspect particularly interesting Would be the application of sub-geothermal heat pump in already existing high-temperature residential heating systems as a complete substitution of old, inefficient and highly-polluting central heating of a building or a housing block. The paper observes energy efficiency of the proposed solution, environmental benefits obtained through shutting down of fossil fuel energy sources, as well as the potential environmental risks

Advanced risk assessment in reverse supply chain processes: A case study in Republic of Serbia

© 2019 CPE, University of Maribor. All rights reserved. Management of a reverse supply chain (RSC) often takes place in an uncertain environment, so it is supposed to be analyzed through the proactive approach for avoidance/elimination of risks. Management initiatives based on the assessed risk level and priority of potential failure mode (PFM) should lead to the increase of business effectiveness, the competitive advantage and sustainability of the RSC. Therefore, the focus of this research is set to proposing the reliable method that would be user-friendly and suitable for the determination of risk level and priority of PFMs in RSC. Uncertainties related to the severities of Potential Effect(s) of Failure (PEF) and their frequencies', as well as detection of PFMs are described by pre-defined linguistic expressions and modelled by the interval type-2 trapezoidal fuzzy numbers (IT2TrFNs). The assessment of the relative importance of risk factors is set as a fuzzy group decision-making. The weights vector is calculated based on the procedure of fuzzy number comparison. The value of each risk factor at the level of each PFM is assessed through the predefined linguistic expressions modelled by IT2TrFNs. The rank is obtained by modified Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method. The proposed model is tested on a real-life data from RSC that operates in Serbia. In the domain of practical implications, it may be noticed that the application of the proposed model could decrease the influence of potential causes of failures modes on the overall RSC business activities especially in the terms of strategic management and human resource practices. The novelty of the proposed model may be underlined as it is used for the analysis of different RSC activities and many interconnected issues may be solved by the proposed management measures after conducted analysis

Study of groundwaters using the environmental tritium and hydrochemical data in the Belgrade region

A study of tritium content and some physicochemical parameters has been performed in order to investigate interconnection between surface and atmospheric waters and underground waters in Belgrade area. Samples of the precipitation at Zeleno Brdo-Belgrade meteorological station, the Danube and the Sava river water, and underground water (Ranney wells and piezometers) have been analyzed. The3H content, the content of dissolved ions, total hardness, and electrical conductivity have been measured. The tritium data show existence of two water strata in the aquifer. The upper stratum (about 16 m thick) contains older water (mean monthly3H concentration of 17 TU) and has weak interaction with the river and the precipitation. Below this stratum lies the principal water bearing stratum, strongly connected with the river with the3H concentration similar to that of surface water (mean monthly3H concentration of 50 TU) and spreading out through the entire aquifer. The contribution of the Sava river water and the two water layers at the Ranney well are calculated starting with the hydrological aquifer model, which supposes that three water components are mixed in the pumped Ranney well water. According to calculation results using the3H concentration and physicochemical characteristics as parameters, more than 70 percent of the water pumped by the Ranney well (in 1983) comes from the Sava with a time delay of less that 15 days. Properties of tritium distribution in precipitation, river waters, and underground water in the Belgrade region are established from the results of measurements of3H concentrations in the period 1976-1983