Search results

Filters

  • Journals
  • Authors
  • Keywords
  • Date
  • Type

Search results

Number of results: 25
items per page: 25 50 75
Sort by:
Download PDF Download RIS Download Bibtex

Abstract

The potential applications of loop heat pipes (LHPs) are the nuclear power space systems, fuel cell thermal management systems, waste heat recovery systems, medium temperature electronic systems, medium temperature military systems, among others. Such applications usually operate in temperature ranges between 500–700 K, hence it is necessary to develop an LHP system that will meet this requirement. Such a thermal management device require to meet various technical problems and challenges currently existing in the development of LHP working in medium temperatures, including: (1) selection of appropriate working fluid; (2) selection of appropriate LHP construction material; (3) construction of suitable test rig capable of testing at elevated temperatures; (4) development of new testing methods. Currently, there are no proven working fluids that can be used in LHPs in medium temperature ranges. Water can be applicable only at temperatures up to 570 K. Caesium can be applicable at temperatures above 670 K. Organic fluids usually tend to generate non-condensable gasses and/or decompose at elevated temperatures and their viscosity dramatically increases. For halides, most of them are very reactive or toxic and their full property data are not available or the majority of the physical properties are predicted, also live tests and their environmental impact data are not adequate. As for casing/LHP construction material, there are no full chemical compatibility tables with most of the medium temperature working fluids and the reactivity of fluids significantly limits the potential materials. Also, testing such an LHP is an endeavour as the reactivity of medium temperature fluids and the use of obscure metals create new challenges. Altogether creates multiple challenges in the development, testing, handling and operating of LHP in the medium temperature range.
Go to article

Bibliography

[1] Zohuri B.: Heat Pipe Design and Technology. Modern Applications for Practical Thermal Management (2nd Edn.). Springer, 2016.
[2] Zhang Y. (Ed.): Heat Pipes: Design, Applications and Technology. Nova, 2018.
[3] Anderson W.G., Bland J.J., Fershtater Y., Goncharov K.A., Nikitkin M., Juhasz A.: High-temperature loop heat pipes. IECEC AP-18, ASME 1995.
[4] Anderson W.G., Rosenfeld J.H., Angirasa D., Mi Y.: Evaluation of heat pipe working fluids in the temperature range 450 to 700 K. AIP Conf. Proc. 699(2004), 20.
[5] Anderson W.G., Bienert W.: Loop heat pipe radiator trade study for the 300– 550 K temperature range. AIP Conf. Proc. 746(2005), 946.
[6] Anderson W.G.: Intermediate temperature fluids for heat pipes and loop heat pipes. In: Proc. 5th Int. Energy Conversion Engineering Conf. Exhib. (IECEC), 25–27 June 2007, AIAA 2007–4836.
[7] Faghri A., Buchko M., Cao Y.: A study of high-temperature heat pipes with multiple heat sources and sinks: Part I – Experimental methodology and frozen startup profiles. J. Heat Transf. 113(1991), 4, 1003–1009.
[8] Faghri A., Buchko M., Cao Y.: A study of high-temperature heat pipes with multiple heat sources and sinks: Part II – Analysis of continuum transient and steadystate experimental data with numerical predictions. J. Heat Transf. 113(1991), 4, 1010–1016.
[9] https://www.1-act.com/merit-number-and-fluid-selection/ (accessed 10 Sept. 2021).
[10] NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP), Version 10. https://www.nist.gov/srd/refprop/ (accessed 10 Sept. 2021).
[11] Blauciak K., Szymanski P., Mikielewicz D.: The influence of loop heat pipe evaporator porous structure parameters and charge on its effectiveness for ethanol and water as working fluids. Materials 14(2021), 7029.
[12] Nikitkin M.N., Bienert W.B., Goncharov K.A.: Non condensable gases and loop heat pipe operation. SAE Tech. Pap. 981584. In: Proc. 28th Int. Conf. on Environmental Systems, 1998.
[13] Wrenn K.R., Wolf D., Kroliczek E.J.: Effect of non-condensible gas and evaporator mass on loop heat pipe performance. SAE Tech. Pap. 2000-01-2409. In: Proc. 30th Int. Conf. on Environmental Systems, 603–614, 2000.
[14] Ishikawa H., Ogushi T., Nomura T., Noda H., Kawasaki H., Yabe T.: Heat transfer characteristics of a reservoir embedded loop heat pipe (2nd report, influence of noncondensable gas on heat transfer characteristics). Heat Transf. Asian Res. 36(2007), 8, 459–473.
[15] Singh R., Akbarzadeh A., Mochizuki M.: Operational characteristics of the miniature loop heat pipe with non-condensable gases. Int. J. Heat Mass Tran. 53(2010), 17–18, 3471–3482.
[16] He J., Lin G., Bai L., Miao J., Zhang H.: Effect of non-condensable gas on the operation of a loop heat pipe. Int. J. Heat Mass Tran. 70(2014), 449–462.
[17] Prado-Montes P.: Development of an elevated temperature loop heat pipe for space applications and investigation of non-condensable gas impact on its performance. PhD thesis, Polytechnic University of Madrid, Madrid 2014.
[18] Devarakonda A., Xiong D., Beach E.D.: Intermediate temperature water heat pipe tests. AIP Conf. Proc. 746(2005), 158.
[19] Mishkinis D., Prado P., Sanz R., Radkov A., Torres A., Tjiptajardja T.: Loop heat pipe working fluids for intermediate temperature range: from –40°C to +125°C. In: Proc. 1st. Int. Conf. on Heat Pipes for Space Applications, Moscow, Sept. 2009.
[20] Mikielewicz D, Błauciak K.: Investigation of the influence of capilary effect on operation of the loop heat pipe. Arch. Thermodyn. 35(2014), 3, 59–80.
Go to article

Authors and Affiliations

Paweł Szymański
1
Dariusz Mikielewicz
1

  1. Gdansk University of Technology, Faculty of Mechanical Engineering and Ship Technology, Narutowicza 11/12,80-233 Gdansk, Poland
Download PDF Download RIS Download Bibtex

Abstract

The paper presents a thermodynamic analysis of the integration of a cryogenic air separation unit into a negative CO 2 emission gas power plant. The power cycle utilizes sewage sludge as fuel so this system fits into the innovative idea of bioenergy with carbon capture and storage. A cryogenic air separation unit integrated with the power plant was simulated in professional plant engineering and thermodynamic process analysis software. Two cases of the thermodynamic cycle have been studied, namely with the exhaust bleed for fuel treatment and without it. The results of calculations indicate that the net efficiencies of the negative CO 2 emission gas power plant reach 27.05% (combustion in 95.0% pure oxygen) and 24.57% (combustion in 99.5% pure oxygen) with the bleed. The efficiencies of the cycle without the bleed are 29.26% and 27.0% for combustion in 95.0% pure oxygen and 99.5% pure oxygen, respectively. For the mentioned cycle, the calculated energy penalty of oxygen production was 0.235 MWh/kgO 2 for the lower purity value. However, for higher purity namely 99.5%, the energy penalty of oxygen production for the thermodynamic cycle including the bleed and excluding the bleed was indicated 0.346 and 0.347 MWh/kgO 2, respectively. Additionally, the analysis of the oxygen purity impact on the carbon dioxide purity at the end of the carbon capture and storage installation shows that for the case with the bleed, CO 2 purities are 93.8% and 97.6%, and excluding the bleed they are 93.8% and 97.8%, for the mentioned oxygen purities respectively. Insertion of the cryogenic oxygen production installation is required as the considered gas power plant uses oxy-combustion to facilitate carbon capture and storage method.
Go to article

Authors and Affiliations

Maja Kaszuba
1
Paweł Ziółkowski
1
Dariusz Mikielewicz
1

  1. Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk, Poland
Download PDF Download RIS Download Bibtex

Abstract

Detailed studies have suggested that the critical heat flux in the form of dryout in minichannels occurs when the combined effects of entrainment, deposition, and evaporation of the film make the film flow rate go gradually and smoothly to zero. Most approaches so far used the mass balance equation for the liquid film with appropriate formulations for the rate of deposition and entrainment respectively. It must be acknowledged that any discrepancy in determination of deposition and entrainment rates, together with cross-correlations between them, leads to the loss of accuracy of model predictions. Conservation equations relating the primary parameters are established for the liquid film and vapor core. The model consists of three mass balance equations, for liquid in the film as well as two-phase core and the gas phase itself. These equations are supplemented by the corresponding momentum equations for liquid in the film and the two-phase core. Applicability of the model has been tested on some experimental data.

Go to article

Authors and Affiliations

Dariusz Mikielewicz
Jan Wajs
Download PDF Download RIS Download Bibtex

Abstract

In the paper presented is the analysis of the results of calculations using a model to predict flow boiling of refrigerants such as R134a, R600a and R290. The latter two fluids were not used in the development of the model semiempirical correction. For that reason the model was verified with present experimental data. The experimental research was conducted for a full range of quality variation and a relatively wide range of mass velocity. The aim of the present study was also to test the sensitivity of developed model to a selection of the model of two-phase flow multiplier and the nonadiabatic effects. For that purpose two models have been analysed namely the one due to Müller-Steinhagen and Heck, and Friedel. In addition, the work shows the importance of taking surface tension into account in the calculation of the flow structure.
Go to article

Authors and Affiliations

Dariusz Mikielewicz
Blanka Jakubowska
Download PDF Download RIS Download Bibtex

Abstract

In the paper presented is a novel concept to utilize the heat from the turbine bleed to improve the quality of working fluid vapour in the bottoming organic Rankine cycle (ORC). That is a completely novel solution in the literature, which contributes to the increase of ORC efficiency and the overall efficiency of the combined system of the power plant and ORC plant. Calculations have been accomplished for the case when available is a flow rate of low enthalpy hot water at a temperature of 90 °C, which is used for preliminary heating of the working fluid. That hot water is obtained as a result of conversion of exhaust gases in the power plant to the energy of hot water. Then the working fluid is further heated by the bleed steam to reach 120 °C. Such vapour is subsequently directed to the turbine. In the paper 5 possible working fluids were examined, namely R134a, MM, MDM, toluene and ethanol. Only under conditions of 120 °C/40 °C the silicone oil MM showed the best performance, in all other cases the ethanol proved to be best performing fluid of all. Results are compared with the "stand alone" ORC module showing its superiority.
Go to article

Authors and Affiliations

Dariusz Mikielewicz
Jarosław Mikielewicz
Download PDF Download RIS Download Bibtex

Abstract

In the paper presented are the issues related to the design and operation of micro heat exchangers, where phase changes can occur, applicable to the domestic micro combined heat and power (CHP) unit. Analysed is the stability of the two-phase flow in such unit. A simple hydraulic model presented in the paper enables for the stability analysis of the system and analysis of disturbance propagation caused by a jump change of the flow rate. Equations of the system dynamics as well as properties of the working fluid are strongly non-linear. A proposed model can be applicable in designing the system of flow control in micro heat exchangers operating in the considered CHP unit.
Go to article

Authors and Affiliations

Dariusz Mikielewicz
Jarosław Mikielewicz
Download PDF Download RIS Download Bibtex

Abstract

In the paper a research on cost-effective optimum design boiling temperature for Organic Rankine Cycle utilizing low-temperature heat sources is presented. The ratio of the heat exchanger area of the boiler to the power output is used as the objective function. Analytical relations for heat transfer area as well power of the cycle are formulated. Evaporation temperature and inlet temperature of the heat source medium as well its mass flow rate are varied in the optimization method. The optimization is carried out for three working fluids, i.e. R 134a, water and ethanol. The objective function (economics profitability, thermodynamic efficiency) leads to different optimal working conditions in terms of evaporating temperature. Maximum power generation in the near-critical conditions of subcritical ORC is the highest. The choice of the working fluid can greatly affect the objective function which is a measure of power plant cost. Ethanol exhibits a minimum objective function but not necessarily the maximum cycle efficiency.
Go to article

Authors and Affiliations

Dariusz Mikielewicz
Jarosław Mikielewicz
Download PDF Download RIS Download Bibtex

Abstract

Flow boiling and flow condensation are often regarded as two opposite or symmetrical phenomena. Their description however with a single correlation has yet to be suggested. In the case of flow boiling in minichannels there is mostly encountered the annular flow structure, where the bubble generation is not present. Similar picture holds for the case of inside tube condensation, where annular flow structure predominates. In such case the heat transfer coefficient is primarily dependent on the convective mechanism. In the paper a method developed earlier by the first author is applied to calculations of heat transfer coefficient for inside tube condensation. The method has been verified using experimental data from literature on several fluids in different microchannels and compared to three well established correlations for calculations of heat transfer coefficient in flow condensation. It clearly stems from the results presented here that the flow condensation can be modeled in terms of appropriately devised pressure drop.
Go to article

Authors and Affiliations

Dariusz Mikielewicz
Rafał Andrzejczyk
Download PDF Download RIS Download Bibtex

Abstract

In the paper presented are studies on the investigation of the capillary forces effect induced in the porous structure of a loop heat pipe using water and ethanol ad test fluids. The potential application of such effect is for example in the evaporator of the domestic micro-CHP unit, where the reduction of pumping power could be obtained. Preliminary analysis of the results indicates water as having the best potential for developing the capillary effect.

Go to article

Authors and Affiliations

Dariusz Mikielewicz
Krzysztof Błauciak
Download PDF Download RIS Download Bibtex

Abstract

In the paper presented are the results of calculations using authors own model to predict heat transfer coefficient during flow boiling of carbon dioxide. The experimental data from various researches were collected. Calculations were conducted for a full range of quality variation and a wide range of mass velocity. The aim of the study was to test the sensitivity of the in-house model. The results show the importance of taking into account the surface tension as the parameter exhibiting its importance in case of the flow in minichannels as well as the influence of reduced pressure. The calculations were accomplished to test the sensitivity of the heat transfer model with respect to selection of the appropriate two-phase flow multiplier, which is one of the elements of the heat transfer model. For that purpose correlations due to Müller-Steinhagen and Heck as well as the one due to Friedel were considered. Obtained results show a good consistency with experimental results, however the selection of two-phase flow multiplier does not significantly influence the consistency of calculations.

Go to article

Authors and Affiliations

Dariusz Mikielewicz
Blanka Jakubowska
Download PDF Download RIS Download Bibtex

Abstract

The evaporation temperature is regarded as one of the major parameters influencing the organic Rankine cycle (ORC) efficiency. Majority of contributions in literature for ORC cycle analyses treat the heat source as if it had an infinite heat capacity. Such analyses are not valuable as the resulting temperature drops of the heat source needs to be small. That leads to the fact that the heat source is not well explored and in the case of waste heat utilization it can prove the poor economics of the ORC. In the present study cooperation of the ORC cycle with the heat source available as a single phase or phase changing fluids is considered. The analytical heat balance models have been developed, which enable in a simple way calculation of heating fluid temperature variation as well as the ratio of flow rates of heating and working fluids in ORC cycle. The developed analytical expressions enable also calculation of the outlet temperature of the heating fluid.

Go to article

Authors and Affiliations

Dariusz Mikielewicz
Jarosław Mikielewicz
Download PDF Download RIS Download Bibtex

Abstract

The economics of an ORC system is strictly linked to thermodynamic properties of the working fluid. A bad choice of working fluid could lead to a less efficient and expensive plant/generation unit. Some selection criteria have been put forward by various authors, incorporating thermodynamic properties, provided in literature but these do not have a general character. In the paper a simple analysis has been carried out which resulted in development of thermodynamic criteria for selection of an appropriate working fluid for subcritical and supercritical cycles. The postulated criteria are expressed in terms of non-dimensional numbers, which are characteristic for different fluids. The efficiency of the cycle is in a close relation to these numbers. The criteria are suitable for initial fluid selection. Such criteria should be used with other ones related to environmental impact, economy, system size, etc. Examples of such criteria have been also presented which may be helpful in rating of heat exchangers, which takes into account both heat transfer and flow resistance of the working fluid.

Go to article

Authors and Affiliations

Dariusz Mikielewicz
Jarosław Mikielewicz
Download PDF Download RIS Download Bibtex

Abstract

This work aims to determine and compare heat generation and propagation of densely packed gold nanoparticles (Au NPs) induced by a resonant laser beam (532 nm) according to the Mie theory. The heat flux propagation is transferred into the materials, which here are: silica glass; soda-lime-silica glass; borosilicate glass; polymethyl methacrylate (PMMA); polycarbonate (PC); and polydimetylosiloxane (PDMS). This analysis aims to select the optimum material serving as a base for using photo-thermoablation. On the other hand, research focused only on Newtonian heat transfer in gold, not on non-Fourier ones, like the Cattaneo approach. As a simulation tool, a computational fluid dynamics code with the second-order upwind algorithm is selected. Results reveal a near-Gaussian and Gaussian temperature distribution profile during the heating and cooling processes, respectively. Dependence between the maximum temperature after irradiation and the glass thermal conductivity is observed confirming the Fourier law. Due to the maximum heating area, the borosilicate or soda-lime glass, which serves as a base, shall represent an excellent candidate for future experiments.
Go to article

Bibliography

[1] Dash S., Mohanty S., Pradhan S., Mishra B.K.: CFD design of a microfluidic device for continuous dielectrophoretic separation of charged gold nanoparticles. J. Taiwan Inst. Chem. Eng. 58(2016), 39–48.
[2] Paruch M., Mochnacki B.: Cattaneo-Vernotte bio-heat transfer equation. Identification of external heat flux and relaxation time in domain of heated skin tissue. Comput. Assist. Meth. Eng. Sci. 25(2018), 2–3, 71–80.
[3] Alia M.E., Sandeep N.: Cattaneo-Christov model for radiative heat transfer of magnetohydrodynamic Casson-ferrofluid: A numerical study. Results Phys. 7(2017), 21–30.
[4] Paruch M., Majchrzak E.: The modelling of heating a tissue subjected to external electromagnetic field. Acta Bioeng. Biomech. 10(2008), 2, 29–37.
[5] Feng B., Li Z., Zhang X.: Prediction of size effect on thermal conductivity of nanoscale metallic films. Thin Solid Films 517(2009), 8, 2803–2807.
[6] Wang B.-X., Zhou L.-P., Peng X.-F.: Surface and size effects on the specific heat capacity of nanoparticles. Int. J. Thermophys. 1(2006), 27, 139–151.
[7] Mie G.: Beträge zur Optik trüber Medien, speziell kolloidaler Metalösungen. Annalen der Physik 330(1908), 3, 377–445.
[8] Pezzi L., De Sio L. Veltri I., Placido T. et al.: Photo-thermal effects in gold nanoparticles dispersed in thermotropic menamic liquid crystals. Phys. Chem. Chem. Phys. 17(2015), 31, 20281–20287.
[9] Pierini F., Tabiryan N., Umeton C., Bunning T.J., De Sio L.: Thermoplasmonics with Gold Nanoparticles: A new weapon in Modern Optics and Biomedicine. Adv. Photonics Res. 2(2021), 8, 1–17.
[10] Annesi F. et al.: Biocompatible and biomimetic keratin capped Au nanoparticles enable the inactivation of mesophilic bacteria via photo-thermal therapy. Colloid. Surface. A 625(2021), 126950.
[11] Bohren C.F., Huffman D.R.: Absorption and Scattering of Light by Small Particles: Wiley-VCH, 1998.
[12] Guglielmelli A. et al.: Biomimetic keratin gold nanoparticle-mediated in vitro photothermal therapy on glioblastoma multiforme. Nanomedicine 16(2021), 2, 121– 138.
[13] Black S.E.: Laser ablation: Effects and Applications. Nova Science, New York 2011.
[14] Radhakrishnan A., Murugesan V.: Calculation of the extinction cross section and lifetime of a gold nanoparticle using FDTD simulations. AIP Conf. Proc. 1620(2014), 52–57.
[15] Giannini V, Fernandez-Domínguez A.I., Heck S.C., Maier S.A.: Plasmonic nanoantennas: fundamentals and their use in controlling the radiative properties of nanoemitters. Chem. Rev. 111(2011), 6, 3888 – 3912.
[16] Louis C., Pluchery O. (Eds.): Gold Nanoparticles for Physics, Chemistry and Biology. Imperial College, London 2012.
[17] Martin R.J.: Mie scattering formulae for non-spherical particles. J. Mod. Optic. 12(1993), 40, 2467–2494
[18] Myers T.G.: Why are the slip lengths so large in carbon nanotubes? Microfluid. Nanofluid. 10(2011), 1145–1145.
[19] Whitby M., Cagnon L., Thanou M., Quirke N.: Enhanced fluid flow through nanoscale carbon pipes. Nano Lett. 8(2008), 9, 2632–2637.
[20] Maxwell J.C.: On stresses in rarified gases arising from inequalities of temperature. Philos. T. R. Soc. Lond. 170(1879), 231–25.
[21] Ziółkowski P., Badur J.: A theoretical, numerical and experimental verification of the Reynolds thermal transpiration law. Int. J. Numer. Method H. 28(2018), 1, 64–80.
[22] Ziółkowski P.: Porous structures in aspects of transpirating cooling of oxycombustion chamber walls. AIP Conf. Proc. 2077(2019), 020065-1–020065-9.
[23] Badur J., Freidt M., Ziółkowski P.: Neoclassical Navier–Stokes equations considering the Gyftopolous–Beretta exposition of thermodynamics. Energies 13(2020), 1656, 1–32.
[24] Mikielewicz D.: Hydrodynamics and heat transfer in bubbly two-phase flows. Int. J. Heat Mass Tran. 46(2002), 2, 207–220.
[25] Muszynski T., Mikielewicz D.: Comparison of heat transfer characteristics in surface cooling with boiling microjets of water, ethanol and HFE7100. Appl. Therm. Eng. 93(2016), 1403–1409.
[26] Badur J.: Concept of Energy Evolution. Wydawn. IMP PAN, Gdansk 2009 (in Polish).
[27] Smoluchowski M.: On conduction of heat by rarefied gases. Phyl. Mag. 46(1898), 192–206.
[28] Smoluchowski M.: On conduction of heat in pulverized solids. Pol. Ac. Art. Sci. 2(1927), 1, 66–77.
[29] Docherty S.Y., Borg M.K., Lockerby D.A., Reese J.M.: Multiscale simulation of heat transfer in a rarefied gas. Int. J. Heat. Fluid. Fl. 50(2014), 114–125.
[30] Stephenson D., Lockerby D.A., Borg M.K., Reese J.M.: Multiscale simulation of nanofluidic networks of arbitrary complexity. Microfluid. Nanofluid. 18(2015), 5– 6, 841–858.
[31] Lockerby D.A., Patronis A., Borg M.K., Reese J.M.: Asynchronous coupling of hybrid models for efficient simulation of multiscale systems. J. Comput. Phys. 284(2015) 261–272.
[32] Sobieski W., Zhang Q.: Multi-scale modeling of flow resistance in granular porous media. Math. Comput. Simulat. 132(2017), 159–171.
[33] Johnson P.B., Christy R.W.: Optical constants of the noble metals. Phys. Rev. B. 6(1972), 12, 4370–4379.
[34] Narottam P.B.: Handbook of Glass Properties. Academic Press, New York 1986.
[35] Agari Y., Ueda A., Omura Y.: Thermal diffusivity and conductivity of PMMA/PC blends. Polymer 38(1997), 4, 801–807.
[36] Cahill D.G., Olson J.R., Fischer H.E., Watson S.K., Stephens R.B., Tait R.H., Ashworth T., Pohl R.O.: Thermal conductivity and specific heat of glass ceramics. Phys. Rev. B 44(1991), 22, 226–232,
[37] James E.M. (Ed.): Polymer Data Handbook. Oxford University Press (1999), 131, 363–367, 411–435, 655–657.
[38] Dixon M.C., Daniel T.A., Hieda M., Smilgies D.M., Chan M.C., Allara D.L.: Preparation, structure, and optical properties of nanoporous gold thin films. Langmuir 23(2007), 5, 2414–2422.
[39] Harvey B.S.: Hyperthermia. New Engl. J. Med. 329(1993), 483–487.
[40] Barichello L.B., Siewert C.E.: A discrete-ordinates solution for a non-grey model withcomplete frequency redistribution. J. Quant. Spectrosc. Ra. 2(1999), 2, 665–675.
[41] Koniorczyk P., Zmywaczyk J.: Analysis of thermal conductivity reduction in grey medium using a discrete ordinate method and the Henyey–Greenstein phase function for absorbing, emitting and anisotropically scattering media. Arch. Thermodyn. 29(2008), 2, 47–60.
[42] Filkoski R.V.: Radiation heat transfer modeling and CFD analysis of pulverizedcoal combustion with staged air introduction. Arch. Thermodyn. 30(2009), 4, 97–118.
[43] Dabrowski P.: Selected studies of flow maldistribution in a minichannel plate heat exchanger. Arch. Thermodyn. 38(2017), 3, 135–148.
Go to article

Authors and Affiliations

Piotr Radomski
1
Paweł Ziółkowski
1
Luciano de Sio
2
Dariusz Mikielewicz
1

  1. Gdansk University of Technology, Faculty of Mechanical Engineering and Shipbuilding, Energy Institute, Narutowicza 11/12, 80-233 Gdansk, Poland
  2. Sapienza University of Rome, Department of Medico-Surgical Sciencesand Biotechnologies, Center for Biophotonics, Piazzale Aldo Moro 5,00185 Roma, RM, Italy
Download PDF Download RIS Download Bibtex

Abstract

In the paper presented are experiences from operation of three different expansion devices for possible implementation in the domestic micro CHP. These were the modified scroll expander and two designs based on the variable working chamber volume pneumatic devices. Experiments showed the superiority of both "pneumatic devices" over the scroll expander, indicating the possible internal efficiencies in the range of 61 82Such efficiencies are very attractive, especially at the higher end of that range. The volume of these devices is much smaller than the scroll expander which makes it again more suitable for a domestic micro CHP. Small rotational velocities enable to conclude that connection to electricity grid will also be simpler in the case of "pneumatic devices". The "pneumatic devices" under scrutiny here could be an alternative to the typical vapour turbine in the ORC cycle, which is in the process of development at the IFFM.

Go to article

Authors and Affiliations

Dariusz Mikielewicz
Jarosław Mikielewicz
Jan Wajs
Download PDF Download RIS Download Bibtex

Abstract

The paper presents investigation into the single water microjet surface cooling producing evaporating film. Reported tests were conducted under steady state conditions. Experiments were conducted using the nozzle size of 70 and 100 μm respectively. In the course of investigations obtained were experimental relations between heat flux and wall superheating. It was proved that the phenomenon is similar to that of pool boiling but the boiling curves are showing a smaller value of critical heat flux (CHF) that the stagnant pool boiling. Values of CHF are also reduced with decreasing liquid subcooling. Theoretical model of surface cooling by evaporating microjet impingement in the stagnation point was described theoreticaly. Results of experiments were compared with predictions by the model showing a good consistency.
Go to article

Authors and Affiliations

Dariusz Mikielewicz
Jarosław Mikielewicz
Tomasz Muszyński
Download PDF Download RIS Download Bibtex

Abstract

The paper describes issues related to pressure drop that accompanies the phenomenon of maldistribution of working fluid between the channels of a model minichannel plate heat exchanger. The research concerns a single exchanger’s plate containing 51 (in every geometry) parallel rectangular minichannels of hydraulic diameters 461 μm, 571 μm, 750 μm, and 823 μm. In addition, more complex geometry has been investigated, equipped with additional diagonal channels (so called extended geometry). The moment of the liquid phase transition through the heat exchanger was recorded at the flow rates ranging from 0.83 g/s to 13.33 g/s in the inlet manifold. The paper discusses the total pressure drop as a function of the flow rate and the characteristic dimension of minichannels, as well as the pressure drop as a function of the time of the fluid passage through the main part of the measuring section in which measurements were done. The resulting profiles correlate with the images of the flow distribution between channels recorded using the fast shutter speed camera, that allows to draw a further conclusions about the specifics of the maldistribution process. The impact of the total pressure drop on the actual range of optimum operating conditions of the heat exchanger was analyzed.
Go to article

Authors and Affiliations

Michał Klugmann
Paweł Dąbrowski
Dariusz Mikielewicz
Download PDF Download RIS Download Bibtex

Abstract

Analysis of the state of-the-art in research of minichannel heat exchangers, especially on the topic of flow maldistribution in multiple channels, has been accomplished. Studies on minichannel plate heat exchanger with 51 parallel minichannels with four hydraulic diameters, i.e., 461 μm, 574 μm, 667 μm, and 750 μm have been presented. Flow at the instance of filling the microchannel with water at low flow rates has been visualized. The pressure drop characteristics for single minichannel plate have been presented along with the channels blockage, which occurred in several cases. The impact of the mass flow rate and channels’ cross-section dimensions on the flow maldistribution were illustrated.

Go to article

Authors and Affiliations

Paweł Dąbrowski
Dariusz Mikielewicz
Michał Klugmann
Download PDF Download RIS Download Bibtex

Abstract

The objective of the paper is to analyse thermodynamical and operational parameters of the supercritical power plant with reference conditions as well as following the introduction of the hybrid system incorporating ORC. In ORC the upper heat source is a stream of hot water from the system of heat recovery having temperature of 90 °C, which is additionally aided by heat from the bleeds of the steam turbine. Thermodynamical analysis of the supercritical plant with and without incorporation of ORC was accomplished using computational flow mechanics numerical codes. Investigated were six working fluids such as propane, isobutane, pentane, ethanol, R236ea and R245fa. In the course of calculations determined were primarily the increase of the unit power and efficiency for the reference case and that with the ORC.

Go to article

Authors and Affiliations

Dariusz Mikielewicz
Jarosław Mikielewicz
Paweł Ziółkowski
Download PDF Download RIS Download Bibtex

Abstract

The Organic Flash Cycle (OFC) is suggested as a vapor power cycle that could potentially improve the efficiency of utilization of the heat source. Low and medium temperature finite thermal sources are considered in the cycle. Additionally the OFC’s aim is to reduce temperature difference during heat addition. The study examines 2 different fluids. Comparisons are drawn between the OFC and an optimized basic Organic Rankine Cycle (ORC). Preliminary results show that ethanol and water are better suited for the ORC and OFC due to higher power output. Results also show that the single flash OFC achieves better efficiencies than the optimized basic ORC. Although the OFC improves the heat addition exergetic efficiency, this advantage was negated by irreversibility introduced during flash evaporation.
Go to article

Authors and Affiliations

Dariusz Mikielewicz
Jan Wajs
Jarosław Mikielewicz
Download PDF Download RIS Download Bibtex

Abstract

A tendency to increase the importance of so-called dispersed generation, based on the local energy sources and the working systems utilizing both the fossil fuels and the renewable energy resources is observed nowadays. Generation of electricity on industrial or domestic scale together with production of heat can be obtained for example through employment of the ORC systems. It is mentioned in the EU directive 2012/27/EU for cogenerative production of heat and electricity. For such systems the crucial points are connected with the heat exchangers, which should be small in size but be able to transfer high heat fluxes. In presented paper the prototype microjet heat exchanger dedicated for heat recovery systems is introduced. Its novel construction is described together with the systematical experimental analysis of heat transfer and flow characteristics. Reported results showed high values of the overall heat transfer coefficient and slight increase in the pressure drop. The results of microjet heat exchanger were compared with the results of commercially available compact plate heat exchanger.
Go to article

Authors and Affiliations

Elżbieta Fornalik-Wajs
Dariusz Mikielewicz
Jan Wajs
Michał Bajor
Download PDF Download RIS Download Bibtex

Abstract

In the paper a method developed earlier by authors is applied to calculations of pressure drop and heat transfer coefficient for flow boiling and also flow condensation for some recent data collected from literature for such fluids as R404a, R600a, R290, R32,R134a, R1234yf and other. The modification of interface shear stresses between flow boiling and flow condensation in annular flow structure are considered through incorporation of the so called blowing parameter. The shear stress between vapor phase and liquid phase is generally a function of nonisothermal effects. The mechanism of modification of shear stresses at the vapor-liquid interface has been presented in detail. In case of annular flow it contributes to thickening and thinning of the liquid film, which corresponds to condensation and boiling respectively. There is also a different influence of heat flux on the modification of shear stress in the bubbly flow structure, where it affects bubble nucleation. In that case the effect of applied heat flux is considered. As a result a modified form of the two-phase flow multiplier is obtained, in which the nonadiabatic effect is clearly pronounced.

Go to article

Authors and Affiliations

Dariusz Mikielewicz
Jarosław Mikielewicz
Rafał Andrzejczyk
Blanka Jakubowska
Download PDF Download RIS Download Bibtex

Abstract

The results of investigations conducted on the prototype of vapour driven micro-CHP unit integrated with a gas boiler are presented. The system enables cogeneration of heat and electric energy to cover the energy demand of a household. The idea of such system is to produce electricity for own demand or for selling it to the electric grid – in such situation the system user will became the prosumer. A typical commercial gas boiler, additionally equipped with an organic Rankine cycle (ORC) module based on environmentally acceptable working fluid can be regarded as future generation unit. In the paper the prototype of innovative domestic cogenerative ORC system, consisting of a conventional gas boiler and a small size axial vapour microturbines (in-house designed for ORC and the commercially available for Rankine cycle (RC)), evaporator and condenser were scrutinised. In the course of study the fluid working temperatures, rates of heat, electricity generation and efficiency of the whole system were obtained. The tested system could produce electricity in the amount of 1 kWe. Some preliminary tests were started with water as working fluid and the results for that case are also presented. The investigations showed that domestic gas boiler was able to provide the saturated/superheated ethanol vapour (in the ORC system) and steam (in the RC system) as working fluids.

Go to article

Authors and Affiliations

Dariusz Mikielewicz
Jan Wajs
Michał Bajor
Zbigniew Kneba

This page uses 'cookies'. Learn more