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Large Scale Shear Box Testing of Interface Between Construction Materials and Soils
(SCIENDO, 2023-12-19) Gago, Filip; Mihálik, Ján; Masarovičová, Soňa; Vlček, Jozef; Boltnar, Vojtěch; Uličný, Lukáš
The interaction between soil and building structures of various materials is defined on the basis of certain assumptions, but these are shown in many cases to be not accurate from the point of view of safe, reliable and economic design of engineering structures. Therefore, as part of our research activities, we decided to better understand the transfer of shear forces and the interaction between soil and other materials. We focused on testing materials in a shear box apparatus, where 3 types of tests were carried out: in the first stage, we tested the shear parameters of the soil in a 900 mm2 box apparatus; in the second stage, the properties of the interaction between soil and concrete were tested, and in the third stage, soil was in contact with the steel plate. The results of the tests are within the expected range of the interface friction angle between the structures and the soils.
Experimental and numerical study on the thermal performance of polycarbonate panels
(Elsevier, 2020-09-13) Čekon, Miroslav; Šikula, Ondřej
Polycarbonate panels are a specific type of transparent insulation material that can be usefully integrated in building envelope structures. As the applications for such systems are increasing, it was necessary to analyse in detail data for materials which are already available to improve their thermal performance. In this paper the experimental campaign was based on the detailed characterization of the equivalent thermal conductivity parameters of several representative polycarbonate panels. The dependence of the equivalent thermal conductivity on the temperature and different angles of inclination are analyzed. Increasing the angle of the investigated polycarbonate panels changed the thermal conductivity parameters to a very minor degree. On the other hand, the effect of temperature on the thermal properties is proved to be significant and the conversion temperature coefficient is provided in this regard. The computational fluid dynamics (CFD) numerical analysis is employed to validate three-dimensional CFD models and simulate the thermal performance of low-e panels for it to theoretically improve their overall thermal parameters. When applying low-e functionality, depending on the type of polycarbonate panel, the equivalent thermal conductivity was found to range from 0.03750W/(m·K) to 0.04172W/(m·K), representing a reduction ranging from 43% to 24%.
A comparative study on the applicability of six radiant floor, wall, and ceiling heating systems based on thermal performance analysis
(ELSEVIER, 2021-04-01) Oravec, Jakub; Šikula, Ondřej; Krajčík, Michal; Arici, Müslüm; Mohapl, Martin
Holistic comparisons of radiant heating systems that would help make an informed decision on the selection of the most convenient system for the specific application are lacking. The applicability of six representative radiant floor, wall, and ceiling heating systems was therefore compared in terms of thermal output and surface area required, controllability, short-term and long-term heat storage, suitability for building retrofit, and investments. Temperature and heat flux distribution in the structure, time constant tau(63), response time tau(90), and the number of operating cycles were computed by a custom-made and verified software tool using the finite volume method. Thermal energy stored was used to determine the ability of energy storage, whereas investment costs indicated affordability. Wall heating with pipes attached to a thermally insulating core had the highest thermal output, was easy to control, suitable for building retrofit, and most affordable while providing limited thermal storage. The performance of the wall system was retained when locating the pipes in plasterboard separated from the core by an air gap. Floor heating performed consistently in all the aspects evaluated. It was demonstrated that inserting a metal fin between pipes and the concrete spread layer improved thermal output, controllability, and storage capacity of the floor system with minor effect on investments. Ceiling with pipes insulated from the core performed well when thermal storage was not required. Ceiling with pipes embedded in the core was only feasible when long-term heat storage was needed.
Heat storage efficiency and effective thermal output: Indicators of thermal response and output of radiant heating and cooling systems
(Elsevier, 2020-12-15) Krajčík, Michal; Šikula, Ondřej
An alternative indicator of thermal response of radiant heating and cooling systems called heat storage efficiency (HSE) has been tested. The heat storage efficiency was compared with established indicators represented by the time constant tau(63), response time tau(95), and thermal energy stored (TES). The comparison was performed for three wall cooling systems with various combinations of pipe location, configuration of material layers, and materials of the thermal core. Considering the whole response curve (HSE) instead of focusing on one specific point on the curve (tau(63), tau(95)) allowed comparing the thermal response of complex systems by a single value. It also permitted predicting thermal response consistently regardless of the system and core material. Thermal energy stored predicted the thermal response of certain systems, but it may not be suitable for comparing the thermal response of radiant systems with different thermal admittance. Besides, a novel indicator of thermal output called effective thermal output (ETO) has been proposed. The effective thermal output considers both the steady-state thermal performance represented by the nominal thermal output and dynamic thermal performance represented by the heat storage efficiency. For thermally active building systems (TABS), effective thermal output was up to 57% lower than the nominal thermal output. (C) 2020 Elsevier B.V. All rights reserved.
Feasibility of Using Energy Performance Contracting for the Retrofit of Apartment Buildings in Slovakia
(Sciendo, 2022-09-01) Gombošová, Veronika; Krajčík, Michal; Šikula, Ondřej
This study is focused on the feasibility of using energy performance contracting (EPC) for the retrofit of two apartment buildings constructed using precast concrete technologies in Slovakia decades ago. The retrofit packages were defined, and their suitability for EPC was evaluated through discounted payback. The uncertainties in the profitability calculations were covered by designing five possible economic developments and defining input ranges instead of just single inputs. The measures in the technical systems were shown to be more feasible than the retrofit of the building envelopes. The potential to finance the selected measures for technical systems through EPC was further evaluated. It was shown that, for at least one of the two buildings studied, the EPC was recommended only for the economic developments with a notable increase in energy prices compared to the baseline that referred to the situation before the Covid-19 pandemic. In the best case, the payback was four years for one building and seven years for the other; thus, both were potentially suitable for EPC. However, for a complex retrofit, the EPC must be combined with a different funding source to also finance other retrofit measures.

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