Work on increasing the efficiency of heat exchangers used in car air conditioning systems may lead to a partial change in the construction of refrigeration systems. One of such changes is the use of smaller gas coolers, which directly translates into a reduction in the production costs of the entire system. The article presents the use of computational fluid dynamics methods to simulate the impact of changing the shape of an internal heat exchanger on the cooling efficiency with R744 as the refrigerant. Internal heat exchangers with different geometry of the outer channels were subjected to numerical analysis. The obtained results of calculations show temperature changes in inner and outer channels on the length of the heat exchanger.
W pracy opisano skomplikowaną i bujną historię budynku dawnego dworu Gorajskich przy ul. Bernardyńskiej 12 w Lublinie. Uwzględniono powszechnie znane fakty i dokumenty historyczne z życia budynku jak i te dopiero poznane. Przy uwzględnieniu istniejących prac badawczych i projektów oraz oględzin i badań własnych udało się wykonać analizę architektoniczną, z wykonaniem rozwarstwienia i określenia faz przekształceń budynku. Praca ta pozwoliła na umieszczenie dworu Gorajskich jako jednego z zapomnianych ale ciągle zachowanych dworów magnackich powstałych w XVII wieku na lubelskim Żmigrodzie.
Determined were direction and intensity of influence of alloying additions on the number of eutectic graphite colonies in austenitic cast iron Ni-Mn-Cu. Chemical composition of the cast iron was 1.7 to 3.3% C, 1.4 to 3.1% Si, 2.8 to 9.9% Ni, 0.4 to 7.7% Mn, 0 to 4.6% Cu, 0.14 to 0.16% P and 0.03 to 0.04% S. Analysed were structures of mottled (20 castings) and grey (20 castings) cast iron. Obtained were regression equations determining influence intensity of individual components on the number of graphite colonies per 1 cm2 (LK). It was found that, in spite of high total content of alloying elements in the examined cast iron, the element that mainly decides the LK value is carbon, like in a plain cast iron.
In the paper, a relationship between chemical composition of Ni-Mn-Cu cast iron and its structure, hardness and corrosion resistance is determined. The examinations showed a decrease of thermodynamic stability of austenite together with decreasing nickel equivalent value, in cast iron solidifying according to both the stable and the metastable systems. As a result of increasing degree of austenite transformation, the created martensite caused a significant hardness increase, accompanied by small decline of corrosion resistance. It was found at the same time that solidification way of the alloy and its matrix structure affect corrosion resista
In the research, relationships between matrix structure and hardness of high-quality Ni-Mn-Cu cast iron containing nodular graphite and nickel equivalent value were determined. Nickel equivalent values were dependent on chemical composition and differences between them resulted mostly from nickel concentration in individual alloys. Chemical compositions of the alloys were selected to obtain, in raw condition, austenitic and austenitic-martensitic cast iron. Next, stability of matrix of raw castings was determined by dilatometric tests. The results made it possible to determine influence of nickel equivalent on martensite transformation start and finish temperatures.
A research of wear resistance of an austenitic cast iron with higher resistance to abrasive-wear and maintained corrosion resistance characteristic for Ni-Resist cast iron is presented. For the examination, structure of raw castings was first formed by proper selection of chemical composition (to make machining possible). Next, a heat treatment was applied (annealing at 550 °C for 4 hours followed by air cooling) in order to increase abrasive-wear resistance. One of the factors deciding intensity of wear appeared to be the chilling degree of castings. However, with respect to unfavourable influence of chilling on machining properties, an important factor increasing abrasivewear resistance is transformation of austenite to acicular ferrite as a result of annealing non-chilled castings. Heat treatment of non-chilled austenitic cast iron (EquNi > 16%) resulted in much higher abrasive-wear resistance in comparison to the alloy having pearlitic matrix at ambient temperature (EquNi 5.4÷6.8%).
Determined was quantitative effect of nickel equivalent value on austenite decomposition degree during cooling-down castings of Ni-MnCu cast iron. Chemical composition of the alloy was 1.8 to 5.0 % C, 1.3 to 3.0 % Si, 3.1 to 7.7 % Ni, 0.4 to 6.3 % Mn, 0.1 to 4.9 % Cu, 0.14 to 0.16 % P and 0.03 to 0.04 % S. Analysed were castings with representative wall thickness 10, 15 and 20 mm. Scope of the examination comprised chemical analysis (including WDS), microscopic observations (optical and scanning microscopy, image analyser), as well as Brinell hardness and HV microhardness measurements of structural components.
Within the presented work, the effect of austenite transformation on abrasive wear as well as on rate and nature of corrosive destruction of spheroidal Ni-Mn-Cu cast iron was determined. Cast iron contained: 3.1÷3.4 %C, 2.1÷2.3 %Si, 2.3÷3.3 %Mn, 2.3÷2.5 %Cu and 4.8÷9.3 %Ni. At a higher degree of austenite transformation in the alloys with nickel equivalent below 16.0%, abrasive wear resistance was significantly higher. Examinations of the corrosion resistance were carried out with the use of gravimetric and potentiodynamic method. It was shown that higher degree of austenite transformation results in significantly higher abrasive wear resistance and slightly higher corrosion rate, as determined by the gravimetric method. However, results of potentiodynamic examinations showed creation of a smaller number of deep pinholes, which is a favourable phenomenon from the viewpoint of corrosion resistance.
Land consolidation procedures are an attempt to comprehensively change the existing spatial structure of land in rural areas. This treatment also brings many other social and economic benefits, contributing to the development of consolidated areas. Land consolidation in mountain areas differs in many respects from those implemented in areas with more favorable conditions for the functioning of agriculture. The unfavorable values of land fragmentation indices, terrain conditions and lower than the average soil quality affect both the dominant forms of agricultural activity and the limited opportunities to improve the distribution of plots in space, parameters of shape, and the area as a result of land consolidation. For this reason, the effectiveness of land consolidation in mountain areas can be achieved by improving the quality of transportation network and the accessibility of the plots, arranging ownership issues and improving the quality of cadastral documentation. This article presents the evaluation of the measures of effectiveness of land consolidation realized in mountain areas on the example of Łetownia Village in the Małopolska Province, located in the southern part of Poland. Selected village is an area with unfavorable conditions for the functioning of agriculture and high values of land fragmentation indices.
The paper presents influence of soaking parameters (temperature and time) on structure and mechanical properties of spheroidal graphite nickel-manganese-copper cast iron, containing: 7.2% Ni, 2.6% Mn and 2.4% Cu. Raw castings showed austenitic structure and relatively low hardness (150 HBW) guaranteeing their good machinability. Heat treatment consisted in soaking the castings within 400 to 600°C for 2 to 10 hours followed by air-cooling. In most cases, soaking caused changes in structure and, in consequence, an increase of hardness in comparison to raw castings. The highest hardness and tensile strength was obtained after soaking at 550°C for 6 hours. At the same time, decrease of the parameters related to plasticity of cast iron (elongation and impact strength) was observed. This resulted from the fact that, in these conditions, the largest fraction of fine-acicular ferrite with relatively high hardness (490 HV0.1) was created in the matrix. At lower temperatures and after shorter soaking times, hardness and tensile strength were lower because of smaller degree of austenite transformation. At higher temperatures and after longer soaking times, fine-dispersive ferrite was produced. That resulted in slightly lower material hardness.
Within the presented research, effect of annealing on nature of corrosion damages of medium-nickel austenitic nodular cast iron castings, containing 5.5% to 10.3% Ni, was determined. Concentration of nickel, lower than in the Ni-Resist cast iron, was compensated with additions of other austenite-stabilising elements (manganese and copper). In consequence, raw castings with austenitic matrix structure and gravimetrically measured corrosion resistance increasing along with nickel equivalent value EquNi were obtained. Annealing of raw castings, aimed at obtaining nearly equilibrium structures, led to partial austenite-to-martensite transformation in the alloys with EquNi value of ca. 16%. However, corrosion resistance of the annealed alloys did not decrease in comparison to raw castings. Annealing of castings with EquNi value above 18% did not cause any structural changes, but resulted in higher corrosion resistance demonstrated by smaller depth of corrosion pits.
In this paper, the effect of changes the parameters of heat treatment on the structure and the degree of elements segregation was determined, in the context of corrosion resistance of ductile iron Ni-Mn-Cu, containing 7.2% Ni, 2.6% Mn and 2.4% Cu. In the condition after casting, castings of austenitic matrix and 160HBW hardness were obtained. The achieved castings were soaked at 450, 550 and 650°C for 4, 8 and 12 hours, then cooled down at the ambient air. In most cases, the heat treatment resulted in a change in the castings matrix, had the consequence of increasing their hardness in comparison to raw castings. Increasing the temperature and prolonging soaking time resulted in increasing the degree of transformation of austenite, while reducing the degree of elements segregation. This led to the formation of slightly bigger number of pitting due to corrosion, but not so deep and more evenly distributed in comparison to raw castings. Wherein the results of corrosion tests show that heat treatment of castings did not significantly change their corrosion resistance in comparison to raw castings, in contrast to the significant increase in mechanical properties.
Evolution of many high technologies such as microelectronics, microsystem technology and nanotechnology involves design, application and testing of technical structures, whose size is being decreased continuously. Scanning probe microscopes (SPM) are therefore increasingly used as diagnostic and measurement instruments. Consequently the demand for standardized calibration routines for this kind of equipment rises. Up to now, there has been no in generally accepted guideline on how to perform SPM calibration procedure. In this article we discuss calibration scheme and focus on several critical aspects of SPM characterization e.g. the determination of the static and dynamic physical properties of the cantilever, the influence factors which need to be considered when plotting a scheme for the calibration of the force and displacement sensitivity.