Ing. Jiří Hejčík, Ph.D.
E-mail:   hejcik@fme.vutbr.cz  Dept.:   Energy Institute Dept. of Thermodynamics and Environmental Engineering Position:   Department Secretary Room:   A2/412 Dept.:   Energy Institute Dept. of Thermodynamics and Environmental Engineering Position:   Assistant Professor Room:   A2/412

Supervised courses:

• Air Conditioning and Heat Pumps (0KT)
• Air Conditioning and Heat Pumps (0KT-A)
• Compact Heat Exchangers (IKV)
• Heat Pumps (LTC)
• Year Project (IRP)

Publications:

• HEJČÍK, J.; CHARVÁT, P.; KLIMEŠ, L.; ASTROUSKI, I.:
  A PCM-water heat exchanger with polymeric hollow fibres for latent heat thermal energy storage: A parametric study of discharging stage
  journal article in Web of Science
• TUHOVČÁK, J.; HEJČÍK, J.; JÍCHA, M.:
  Comparison of heat transfer models for reciprocating compressor, Elsevier
  journal article in Web of Science
• TUHOVČÁK, J.; HEJČÍK, J.; JÍCHA, M.:
  Modelling of fluid flow and heat transfer in a reciprocating compressor,
  9th International Conference on Compressors and their Systems, pp.1-10, (2015), IOP Conference Series
  conference paper
  akce: 9th International Conference on Compressors and their Systems, London, 07.09.2015-09.09.2015
• CHARVÁT, P.; ŠTĚTINA, J.; KLIMEŠ, L.; OSTRÝ, M.; HEJČÍK, J.:
  Experimental investigation of the thermal behaviour of a water-PCM heat exchanger for stabilization of water temperature,
  Sborník příspěvků konference 24th International Symposium on Transport Phenomena 2013, pp.280-283, (2013), Tokyo University of Science Yamaguchi
  conference paper
  akce: International symposium on transport phenomena, Yamaguchi, 01.11.2013-05.11.2013
• Charvát Pavel, Pech Ondřej, Hejčík Jiří:
  Experimental investigations of the performance of a solar air collector with latent heat thermal storage integrated with the solar absorber
• HEJČÍK, J.; JÍCHA, M.:
  Vliv parametrů výměníku na výkonnost klimatizačního systému malých letadel a vrtulníků,
  Strojárstvo/Strojírenství, Vol.2009, (2009), No.6, pp.67-68, ISSN 1335-2938, Media/ST s.r.o
  journal article - other
• HEJČÍK, J.; SUNDÉN, B.; WANG, L.:
  PIV Measurement of Separated Flow in a Square Channel With Streamwise Periodic Ribs on One Wall,
  JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME, Vol.129, (2007), No.7, pp.834-841, ISSN 0098-2202, ASME
  journal article - other

List of publications at Portal BUT

Abstracts of most important papers:

• HEJČÍK, J.; CHARVÁT, P.; KLIMEŠ, L.; ASTROUSKI, I.:
  A PCM-water heat exchanger with polymeric hollow fibres for latent heat thermal energy storage: A parametric study of discharging stage
  journal article in Web of Science
  The paper presents a theoretical parametric study into latent heat thermal energy storage (LHTES) employing polymeric hollow fibres embedded in a phase change material (PCM). The polymeric hollow fibres of five inner diameters between 0.5 mm and 1.5 mm are considered in the study. The effectiveness-NTU method is employed to calculate the thermal performance of a theoretical LHTES unit of the shell-and-tube design. The results indicate that the hollow fibres embedded in a PCM can mitigate the drawback of low thermal conductivity of phase change materials. For the same packing fraction, the total heat transfer rates between the heat transfer fluid and the PCM increase with the decreasing diameter of the hollow fibres. This increase in the heat transfer rate and thus the efficiency of the heat exchange to some extent compensate for the energy consumption of the pump that also increases with the decreasing fibre diameter.
• TUHOVČÁK, J.; HEJČÍK, J.; JÍCHA, M.:
  Comparison of heat transfer models for reciprocating compressor, Elsevier
  journal article in Web of Science
  • Comparison of integral heat transfer models. • Influence of heat transfer model on volumetric and isentropic efficiency. • Various gases used as working fluid.
• Charvát Pavel, Pech Ondřej, Hejčík Jiří:
  Experimental investigations of the performance of a solar air collector with latent heat thermal storage integrated with the solar absorber
  The paper deals with experimental investigations of the performance of a solar air collector with latent heat thermal storage integrated with the solar absorber. The main purpose of heat storage in solar thermal systems is to store heat when the supply of solar heat exceeds demand and release it when otherwise. A number of heat storage materials can be used for this purpose; the phase change materials among them. Short-term latent heat thermal storage integrated with the solar absorber can stabilize the air temperature at the outlet of the collector on cloudy days when solar radiation intensity incident on a solar collector fluctuates significantly. Two experimental front-and-back pass solar air collectors of the same dimensions have been built for the experimental investigations. One collector had a "conventional" solar absorber made of a metal sheet while the solar absorber of the other collector consisted of containers filled with organic phase change material. The experimental collectors were positioned side by side during the investigations to ensure the same operating conditions (incident solar radiation, outdoor temperature).
• HEJČÍK, J.; SUNDÉN, B.; WANG, L.:
  PIV Measurement of Separated Flow in a Square Channel With Streamwise Periodic Ribs on One Wall,
  JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME, Vol.129, (2007), No.7, pp.834-841, ISSN 0098-2202, ASME
  journal article - other
  In this study, particle image velocimetry (PIV) is used to investigate the physical process of separated flow in a square channel roughened with periodically transverse ribs on one wall. The ribs obstruct the channel by 15% of its height and are arranged 12 rib heights apart. The Reynolds number, based on the bulk-mean velocity and the corresponding hydraulic diameter of the channel, is fixed at 22,000. Assuming flow periodicity in the streamwise direction, the investigated domain is between two consecutive ribs. The emphasis of this study is to give some insight into the turbulence mechanism associated with separation, reattachment, and subsequent redevelopment. Results are included for mean velocity, friction coefficient, vorticity thickness, Reynolds shear stress, anisotropy parameter, and production of turbulent kinetic energy and shear stress. Based on the two-point correlation profiles, Taylor microscales are derived to reveal the sizes of the turbulence structure in the longitudinal and lateral directions. Moreover, Galilean decomposition is applied to the instantaneous velocity fields. The result shows that the separated shear layer is dominated by the large-scale, unsteady vortical structures.
• HEJČÍK, J.; JÍCHA, M.:
  CFD Designing of the micro turbine recuperator,
  Heat Transfer in Components and Systems for Sustainable Energy Technologies, Proceedings of the Heat-SET 2005 conference, pp.151-158, ISBN 2-9502555-0-7, (2005), CEA-Grenoble
  conference paper
  akce: Heat Transfer in Components and Systems for Sustainable Energy Technologies, Grenoble, 05.04.2005-07.04.2005
  For high-speed micro gas turbine plants for electrical power and heat generation, a recuperator is needed to obtain a high thermal efficiency. The recuperator receives heat from the exhaust gas and preheats the compressor discharge air before it enters the combustion chamber. Such plants contribute to an ecological and environmental-friendly energy production. (Muley, Sundén, 2003) This paper deals with the computer modelling of the recuperator where a commercial Computational Fluid Dynamics (CFD) code STAR-CD is being used for this purpose. The first part of the paper shows CFD ability to appreciate various heat transfer surfaces. Three different surfaces (cross corrugated surface, dimpled and rifled tube) are selected, modelled and compared. Next part of this paper describes the CFD evaluation of the required recuperator efficiency (92 percent). The last part of the paper considers simulations of the inlet/outlet manifolds where two construction variants are modelled and contrasted. Simulation results obtained are presented and discussed.