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Papers by Frantisek Miksik

Proceedings of International Exchange and Innovation Conference on Engineering & Sciences (IEICES)

Selection and peer-review under responsibility of the scientific committee of the 13th Int. Conf.... more Selection and peer-review under responsibility of the scientific committee of the 13th Int. Conf. on Applied Energy (ICAE2021).

The Proceedings of the International Conference on Power Engineering (ICOPE)

International Journal of Sustainable Energy, 2021

ABSTRACT This paper presents a comparative analysis of the potential working fluids for a promisi... more ABSTRACT This paper presents a comparative analysis of the potential working fluids for a promising thermodynamic cycle (Thermal Power Pump cycle) for the utilisation of low-grade heat. The cycle was analyzed along with nucleate boiling correlations and film condensation analysis for variable heat source temperatures (50–150°C) using nine potential working fluids. The working fluids showed varying degrees of cycle performance and system size requirements. Among the working fluids, cyclopentane seems to be an attractive choice of working fluid, due to its superior cycle performance over the wide range of heat source temperatures with moderate system size requirements. For temperatures above 146°C and below 60°C, water and n-pentane are selected, respectively. Working fluids with stronger molecular forces seem to approach the properties of an ideal working fluid for better performance of the system.

IOP Conference Series: Materials Science and Engineering, 2021

The study aims to achieve energy savings of air conditioning systems using desiccant dehumidifica... more The study aims to achieve energy savings of air conditioning systems using desiccant dehumidification with low-cost adsorbent. For this purpose, two existing activated carbons were evaluated in terms of water adsorption capacity. The theoretical calculation of effective adsorption from the water adsorption isotherms revealed that the studied activated carbons have promising potential in dehumidification application. In addition to that, the improvement of cooling COP of air conditioners was predicted by simulation of heat pump cycle. The results showed that the COP improved by 50%, which was equivalent to the reduction of electricity input by 30%, with the raise of evaporation temperature from 8.5°C to 18.5°C. The results encouraged the separation of dehumidification load from air conditioners to achieve large energy savings.

International Journal of Refrigeration, 2021

Thermodynamic analysis and impact of thermal masses on adsorption cycles using Max-sorbIII/R245fa... more Thermodynamic analysis and impact of thermal masses on adsorption cycles using Max-sorbIII/R245fa and SAC-2/R245fa pairs,

Applied Sciences, 2021

In this study, we evaluated the performance of low Global Warming Potential (GWP) refrigerant R12... more In this study, we evaluated the performance of low Global Warming Potential (GWP) refrigerant R1234yf on the activated carbon (MSC-30) for adsorption heating applications. The adsorption isotherms of MSC-30/R1234yf were measured using a constant-volume–variable-pressure (CVVP) method from very low relative pressure to the practical operating ranges. The data were fitted with several isotherm models using non-linear curve fitting. An improved equilibrium model was employed to investigate the influence of dead thermal masses, i.e., the heat exchanger assembly and the non-adsorbing part of the adsorbent. The model employed the model for the isosteric heat of adsorption where the adsorbed phase volume was accounted for. The performance of the heat pump was compared with MSC-30/R134a pair using the data from the literature. The analysis covered the desorption temperature ranging from 60 °C to 90 °C, with the evaporation temperature at 5 °C and the adsorption temperature and condensation ...

Energies, 2020

A new model of adsorption isotherms Type IV and V is proposed as a basis for theoretical calculat... more A new model of adsorption isotherms Type IV and V is proposed as a basis for theoretical calculations and modelling of adsorption systems such as adsorption heat storage and heat pumps. As the current models have decent yet limited applicability, in this work, we present a new combined model with universal use for micro-mesoporous silica/water adsorption systems. Experimental measurement of adsorption isotherm of water onto seven different samples of micro and mesoporous silica and aluminium-silica were used to fit new adsorption models based on a combination of classical theories and a distribution function related to the pore-size distribution of the selected materials. The fitting was conducted through a repeated non-linear regression using Trust Region Reflective algorithm with weighting factors to compensate for the scalability of the adsorption amount at low relative pressure with optimization of the absolute average deviation fitting parameter. The results display a significa...

The Proceedings of the Symposium on Environmental Engineering, 2020

Energy Reports, 2020

Adsorption thermal energy storage plays a vital role in supporting the availability of renewable ... more Adsorption thermal energy storage plays a vital role in supporting the availability of renewable energy. Activated carbons produced from local waste biomass have been attracting considerable attention in adsorption technology due to their unique properties and sustainability. However, their limitation in water vapor uptake hinders the practical application of this material. In this work, acorn nutshells were utilized as a base material to produce activated carbon. Air oxidation was performed as a versatile and low-cost technique to enhance the material's properties and water adsorption capacity. By applying air oxidation as a post-treatment during material production, the amount of active functional groups and the water adsorption on activated carbon has been successfully enhanced. From the theoretical calculation, it is found that activated carbon-water working pairs shown promising performance to be used for adsorption thermal energy storage applications. The adsorption of water vapor on the post-treated-activated carbon releases the isosteric heat between 2400 kJ/kg to 2500 kJ/kg. Moreover, this study's working pair can be driven by a temperature of less than 50 • C. From the results, it is confirmed that by controlling the adsorbent's surface properties, activated carbon-water working pairs can be a promising way to provide alternative material and reduce the energy demand for driving the system.

Microporous and Mesoporous Materials, 2019

A detailed investigation on the main characteristics was conducted on a novel and unique group of... more A detailed investigation on the main characteristics was conducted on a novel and unique group of industrially produced mesoporous silica material. Six materials from a TMPS group were selected in the respect to their pore size ranging from 1.8 nm up to 4.2 nm. Four of the selected samples were also made with silica doping making them potentially attractive for water adsorption applications with the advantage of the pore-tuning possibilities for specific use. The surface area, pore volume and pore size distribution of these materials were established by standard nitrogen adsorption at T = 77.4 K showing typical values of mesoporous silica materials such as high surface area in the range from 600 to 750 m 2 g −1 and pore volumes reaching 0.38 cm 3 g −1 in the case of the smallest TMPS-1.5A and 0.98 cm 3 g −1 in the case of the largest TMPS-4R. The wall thickness was found out regular around 1.5~2 nm with lower values attributed to bigger pore sized samples promising good structural integrity. Specific heat showed regular values through all the samples at~0.85 J g −1 K −1. Additional information on the structural characteristics and the effect on the amount of silanol group presence and the difference on regular and aluminium-doped samples were studied by means of 29 Si DD/MAS NMR. Additionally, elemental analysis by EDS was conducted as well. All the characteristics of the TMPS materials were compared to the standard mesoporous silica materials SBA-15 and MCM-41.

Adsorption, 2019

Six samples from the TMPS family of mesoporous silica nano-materials from Taiyo Kagaku Co., Ltd. ... more Six samples from the TMPS family of mesoporous silica nano-materials from Taiyo Kagaku Co., Ltd. were studied for their potential as a medium for the adsorption thermal energy storage. Selected specimens are distinguished by their pore size from 1.9 to 4.1 nm and aluminium doping. As the adsorbate for the adsorption pair was selected water with the most advantageous properties of high latent heat and safe chemical properties. The tested materials doped with aluminium show high affinity towards the selected adsorbate and high uptakes. The theoretical storage energy density of the materials spans from 700 to 1700 kJ kg −1 based on the adsorption heat. The storage capacity depends mostly on the pore volume and partially on the pore size. The theoretical estimation shows the temperature gain of the adsorption potential as high as T = 23 • C for the material TMPS-1.5A with the smallest pore diameter and aluminium doping and as low as T = 6 • C for the TMPS-4R with the biggest pore diameter and without aluminium doping.