https://etalpykla.vilniustech.lt/handle/123456789/160180 2026-04-28T15:29:56Z 2026-04-28T15:29:56Z Valančius, Rokas Jurelionis, Andrius https://etalpykla.vilniustech.lt/handle/123456789/160406 2026-04-28T13:10:43Z 2011-01-01T00:00:00Z

Influence of unsteady thermal state on productivity in office buildings Valančius, Rokas; Jurelionis, Andrius Indoor air temperature has a significant effect on productivity of the employees in office buildings. It may reduce work performance and cause financial losses in a long term perspective. However, sudden variations of air temperature during the work day may have an impact on the work performance as well. The aim of this study was to assess the change of office work performance of the same individuals affected by unsteady air temperature. Laboratory tests were performed in the test chamber. Office work was simulated in the chamber with two workplaces and two persons at the time. 48 individuals of age 19 to 30 were divided into three groups and took participation in performing productivity tests. A case with the temperature rise from +22 to +26 °C as well as case with the temperature drop from +22 to +18 °C was analyzed. The same tests were performed with the placebo group with a steady indoor climate conditions (constant air temperature of +22 °C). Results of the study showed that overall accuracy of the execution of the tasks increased with the second fulfilment in the placebo group by 1,4 %. In case of the air temperature rise, performance reduced by 0,2 % and overall productivity improved by 4,1 % in case of air temperature drop.

2011-01-01T00:00:00Z Streckienė, Giedrė Martinaitis, Vytautas Vaitiekūnas, Petras https://etalpykla.vilniustech.lt/handle/123456789/160405 2026-04-28T12:43:52Z 2011-01-01T00:00:00Z

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.

2011-01-01T00:00:00Z Sokas, Algirdas Vdovinskienė, Sonata https://etalpykla.vilniustech.lt/handle/123456789/160404 2026-04-28T11:51:54Z 2011-01-01T00:00:00Z

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.

2011-01-01T00:00:00Z Rusowicz, Artur Ruciński, Adam https://etalpykla.vilniustech.lt/handle/123456789/160403 2026-04-28T11:29:59Z 2011-01-01T00:00:00Z

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.

2011-01-01T00:00:00Z