The article concerns computer modelling of processes in cooling systems of internal combustion engines. Modelling objectives and existing commercial programs are presented. It also describes Author’s own method of binding graphs used to describe phenomena in the cooling system of a spark ignition engine. The own model has been verified by tests on the engine dynamometer. An example of using a commercial program for experimental modelling of an installation containing a heat accumulator is presented.
Financial management in a capital group is very important for its growth and operation. Liquidity risk management can be analyzed regarding their static and dynamic dimensions. The process can also be facilitated by cash management products offered by financial institutions. One of the mechanisms influencing the increase in cash management efficiency of a capital group examined in this article is cash pooling, notably multicurrency cash pooling. This type of product is based frequently on the virtual consolidation. Its essence is the consolidation of cash available on the accounts of individual system participants. Using this solution the capital group can manage surpluses and shortages achieving the “economies of scale” (cost reduction and maximization of interest income). Available one the banking services market solutions offer consolidation in USD, EUR, CHF, GBP. The article presents the definition of cash pooling and the essence of its operation. Based on the literature analysis, the article lists types of cash pooling and benefits associated with it. Following on from the solution described, the article presents a model of multicurrency cash pooling in a capital group, including steps necessary to implement it and proposed technical solutions. The solution is described, can be also successfully applied in capital groups of energy sector. Using multicurrency consolidation is very useful solution in deposits management for transactions concluded in international commodities exchanges.
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.
Chunky graphite has been recognized for a long time as one of the major problems in production of heavy section nodular cast iron. A great number of studies have been conducted to describe the chunky graphite formation, but a clear understanding of its appearance and a safe mastering of the melt preparation to avoid chunky graphite are not yet available. In the present work the cooling curves were recorded in large cone blocks and standard TA cup. According to measured data from the cone block, melt characteristics and heat transfer coefficient between casting and mould were adjusted in the ProCAST® simulation software. For a near-eutectic nodular cast iron test melt with 0.7 wt. % Ni, relationship between the area of the cone block affected by chunky graphite and simulation software results has been observed, i.e., thermal modulus and time to solidus.
The paper presents the effect of tin on the crystallization process, microstructure and hardness of cast iron with compacted (vermicular) graphite. The compacted graphite was obtained with the use of magnesium treatment process (Inmold technology). The lack of significant effect of tin on the temperature of the eutectic transformation has been demonstrated. On the other hand, a significant decrease in the eutectoid transformation temperature with increasing tin concentration has been shown. It was demonstrated that tin narrows the temperature range of the austenite transformation. The effect of tin on the microstructure of cast iron with compacted graphite considering casting wall thickness has been investigated and described. The carbide-forming effect of tin in thin-walled (3 mm) castings has been demonstrated. The nomograms describing the microstructure of compacted graphite iron versus tin concentration have been developed. The effect of tin on the hardness of cast iron was given.