https://etalpykla.vilniustech.lt/handle/123456789/160180 Tue, 28 Apr 2026 12:43:26 GMT 2026-04-28T12:43:26Z https://etalpykla.vilniustech.lt/handle/123456789/160405 Simulation of thermal stratification in the heat storage for CHP plant Streckienė, Giedrė; Martinaitis, Vytautas; Vaitiekūnas, Petras Thermal stratification phenomenon is successfully used to store and retrieve thermal energy from heat storages. The aim of this study is to compare two simulation models for describing thermal stratification in the heat storage tank used in the cogeneration (CHP) plant at any time. In this paper analytical and numerical analyses have been carried out to show temperature fields inside the heat storage. The first analytical model is done using an energy balance which is created and solved for each layer of the stratified heat storage. This model shows a simple onedimensional approach to theoretical analysis of thermal stratification. The other numerical model is implemented using a multi-purpose computation fluid dynamics (CFD) software PHOENICS. Two-dimensional transient model was created and solved numerically. The validation of simulated results is made successfully by the comparison against the actual data gathered from Hvide Sande CHP plant in Denmark. A good agreement with actual data is observed. The average relative discrepancy varied from 0.22 % to 5.00 % in analytical modelling and from 0.21 % to 3.66 % in numerical simulation, when the duration of simulated processes lasts from 15 min to 6 hours. Sat, 01 Jan 2011 00:00:00 GMT https://etalpykla.vilniustech.lt/handle/123456789/160405 2011-01-01T00:00:00Z https://etalpykla.vilniustech.lt/handle/123456789/160404 The house plan drawing and heating system automated design Sokas, Algirdas; Vdovinskienė, Sonata The heating system design is directly related to the building’s plan drawings. The article reviews the possibility of programming a way to find the necessary information directly from the drawing and using it for designing the heating system. Automated objects recognition is very relevant to computer science. The building contours and windows positions are found in the plan of the premise. The heating system is automatically designed based on the found data. This article explores the drawing’s graphical objects rectangular setting. All the lines forming a rectangular are assembled into an array and numbered to determine their dependence on a particular rectangular. From that information the room’s area is calculated. Windows positions on the plan determine the geometry of the windows blocks. Specific creation features of the house heating automated design system are discussed and conclusions are made. Sat, 01 Jan 2011 00:00:00 GMT https://etalpykla.vilniustech.lt/handle/123456789/160404 2011-01-01T00:00:00Z https://etalpykla.vilniustech.lt/handle/123456789/160403 The mathematical modelling of the absorption refrigeration machines used in energy systems Rusowicz, Artur; Ruciński, Adam In the paper the authors present the possible usage of absorption refrigeration machines in air-conditioning systems and tri- and cogeneration processes. One-stage and multi-stage absorption refrigeration cycles are described. The influence of temperature of cooling water or chilled water on refrigeration plant’s COP is analyzed. The series of thermodynamic parameters are taking into consideration - the temperature of feeding medium of the desorber, the temperature of cooling water and the use of various energy carriers to drive absorption devices including biogas from organic and communal waste matter. Some comparative calculations of COP are presented to find the optimal absorption cycle for building energy systems. Sat, 01 Jan 2011 00:00:00 GMT https://etalpykla.vilniustech.lt/handle/123456789/160403 2011-01-01T00:00:00Z https://etalpykla.vilniustech.lt/handle/123456789/160402 Temperature efficiency of rotary heat recovery units in ventilation and air conditioning Parfentyeva, Natalia; Samarin, Oleg; Lushin, Kirill; Paulauskaitė, Sabina; Valančius, Kęstutis The article focuses on processes in rotary heat recovery ventilation and air conditioning units. Here we offer approximated engineering formula of thermal efficiency based on dimensionless parameters and further analysis of final results within all possible range of values. The results are illustrated graphically and with calculated data. Sat, 01 Jan 2011 00:00:00 GMT https://etalpykla.vilniustech.lt/handle/123456789/160402 2011-01-01T00:00:00Z