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1.
Gonilni mehanizmi kavitacijskega vrtinca v vstopnem vodu radialne črpalke
Andrej Predin, Ignacijo Biluš, 2001, original scientific article

Abstract: V prispevku je podana analiza gonilnih mehanizmov in tlačnih utripanj povezanih s pojavom kavitacijskega vrtinca v vstopnem vodu radialne črpalke. Kavitacijski vrtinec je rezultat interakcije številnih zapletenih sekundarnih tokovnih pojavov, ki nastopijo kot posledica obratovanja s podoptimalnimi pretoki v kavitacijskem obratovalnem režimu. Izvedene in predstavljene so tudi meritve tlačnih utripanj v vstopnem vodu radialne črpalke na različnih razdaljah od rotorskega ustja na sklenjeni kavitacijski merilni progi. Meritve so izvedene pri različnih vrtilnih hitrostih in različnih tlakih nad spodnjo vodno gladino. Podani so tudi rezultat frekvenčne analize posnetih tlačnih utripanj.
Keywords: radial pumps, cavitation, swirl, operating regime, pressure pulsation measurements
Published: 10.07.2015; Views: 739; Downloads: 14
URL Link to full text

2.
Analysis of two-stage high- temperature heat pump efficiency
Milovan Jotanović, G. Tadić, Jurij Krope, Darko Goričanec, 2012, original scientific article

Abstract: The paper shows the potential benefit of using low temperature heat sources with high temperature pumps. Two-stage heat pumps with flash unit and heat exchanger are described. To determine the characteristic parameters of the twoheat pumps a computer program was designed, with which we could determine the dependence of COP and compressor pressure ratios from evaporating temperature. An economic analysis of the justification of the use of heat pumps was made.
Keywords: heat transfer, high temperature heat pumps, computer programme, economic analysis
Published: 10.07.2015; Views: 926; Downloads: 43
URL Link to full text

3.
Prerotation flow measurement
Andrej Predin, Ignacijo Biluš, 2003, original scientific article

Abstract: Different measuring methods relating to the prerotation flow in the entrance pipe of radial pumps are analyzed. The appearance of the prerotation flow is a result of the complicated fluid flow model, which appears as a consequence of the pump operating out of design limits and reduces pump efficiency. The goal of this contribution is in estimating the best measuring method, taking into account the inconvenience of conventional hot-wire and laser-Doppler anemometry. Therefore, two measuring systems - multiblade (ASB) and single blade (ASSB) anemometer - are introduced, analyzed and compared. The advantages of the introduced measuring system -ASB- are in its simple construction and simple use and its low price. The direction and swirl flow intensity in the entrance pipe of radial pumps and fans could be measured using this method.
Keywords: radial pumps, prerotation flow, anemometer with straight blades, anemometer with single straight blade
Published: 01.06.2012; Views: 1225; Downloads: 77
URL Link to full text

4.
Long-term performance of central heat pumps in Slovenian homes
Milan Marčič, 2004, original scientific article

Abstract: Due to limited availability of natural resources exploited for heating and in order to reduce the environmental impact, people should strive to use renewable energy sources. Heat pumps allow the conversion of ambient heat, available in almost unlimited quantities, to heating energy. The paper describes an energy-saving house provided with good thermal insulation and heated by an air-to-water split-type heat pump. The condenser is located in the attic and the evaporator in the boiler room of the house. The house heating up to the ambient temperature of 0 °C was provided by an air-to-water heat pump and a condensing oil heating furnace if the ambient temperature dropped to below 0 °C. The results of the nine-year testing showed that the heat pump was used during most of the heating season. The average coefficient of performance (COP) of the air-to-water heat pump in nine heating seasons was3.16, indicating that over 68% of the heat was obtained from the ambient air. The comparison between COP of air-to-water heat pumps in energy-saving house and of water-to-water heat pumps fitted in houses dealt with under otherprojects indicates that water-to-water heat pumps have higher COPs. The heat pumps obtain heat from groundwater, hence they are capable of operating throughout the heating season, and possess the highest COP. The advantage of an air-to-water heat pump, however, lies in its simple design and a wide rangeof applications. Due to limited availability of natural resources exploited for heating and in order to reduce the environmental impact, people should strive to use renewable energy sources. Heat pumps allow the conversionof ambient heat, available in almost unlimited quantities, to heating energy. The paper describes an energy-saving house provided with good thermal insulation and heated by an air-to-water split-type heat pump. The condenser is located in the attic and the evaporator in the boiler room of thehouse. The house heating up to the ambient temperature of 0 °C was providedby an air-to-water heat pump and a condensing oil heating furnace if the ambient temperature dropped to below 0 °C. The results of the nine-year testing showed that the heat pump was used during most of the heating season. The average coefficient of performance (COP) of the air-to-water heat pump in nine heating seasons was 3.16, indicating that over 68% of the heat was obtained from the ambient air. The comparison between COP of air-to-water heatpumps in energy-saving house and of water-to-water heat pumps fitted in houses dealt with under other projects indicates that water-to-water heat pumps have higher COPs. The heat pumps obtain heat from groundwater, hence they are capable of operating throughout the heating season, and possess the highest COP. The advantage of an air-to-water heat pump, however, lies in its simple design and a wide range of applications. In comparison to the furnace, the heat pump yielded considerable saving in fuel and monry, which justifies its home heating application in the Central European climatic area. The analys
Keywords: heating, energy saving houses, heat pumps, therodynamics, refrigeration
Published: 01.06.2012; Views: 1546; Downloads: 91
URL Link to full text

5.
Pressure control in hydraulic systems with variable or constant pumps?
Darko Lovrec, Samo Ulaga, 2007, original scientific article

Abstract: The paper deals with electrohydraulic supply systems with variable (adjustable( supply pressures. Two control concepts are used in practice: the pressure control concept using a variable pump and constant speed of the driving electric motor as the commonly used concept, and the pressure control concept with a constant pump and a speed-controlled electric motor as the alternative concept. The typical features and the applicability of both conceps, as well as their dynamic responses are studied in this work.
Keywords: automatic control engineering, hydraulic systems, pressure control, constant pumps
Published: 31.05.2012; Views: 1413; Downloads: 0

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