Local heat transfer coefficients during the evaporation of 1,1,1,2-tetrafluoroethane (R-134a) in a plate heat exchanger

The evaporation heat transfer coefficient of the refrigerant R-134a in a vertical plate heat exchanger was investigated experimentally. The area of the plate was divided into several segments along the vertical axis. For each of the segments, the local value of the heat transfer coefficient was calculated and presented as a function of the mean vapor quality in the segment. Owing to the thermocouples installed along the plate surface, it was possible to determine the temperature distribution and vapor quality profile inside the plate. The influences of the mass flux, heat flux, pressure of system and the flow configuration on the heat transfer coefficient were also taken into account and a comparison with literature data was performed

Gustine i viskoznosti binarnih sistema sa N,N-dimetilanilinom i tetra etilen glikolom dimetil etrom ili N-metil-2-pyrolidonom, kao potencijalni rastvarači za procese odsumporavanja dimnih gasova

Sulfur oxides are emitted as one of the products in the process of combusting solid fossil fuels in thermal power plants, especially the Kolubara and Kostolac lignites in the Republic of Serbia. In order to reduce the emission level of the indirect Greenhouse gases (GHG) from stationary sources, it is inevitable to implement flue gas desulfurization (FGD) technology. In addition to the classic limestone process, technological procedures based on the physical or chemical absorption of sulfur oxides in the solvent and its thermal regeneration are becoming increasingly common. In order to properly design and optimize the process, it is significant to precisely determine the thermophysical properties of pure components and their mixtures. The paper presents the results of determining the density and viscosity of two binary mixtures, N,N-Dimethylaniline (N,N-DMA) + Tetra Ethylene Glycol Dimethyl Ether (TEGDME) and N,N-Dimethylaniline (N,N-DMA) + N-methyl-2-pyrrolidone (NMP). Measurements were made using a densitometer Anton Paar DMA 5000 and Stabinger viscometer Anton Paar SVM 3000/G2, at atmospheric pressure. The obtained experimental results are presented as a function of temperature and N,N-DMA mole fraction. N,N-DMA belongs to the group of amines, and it has been used as a sorbent for purification of flue gases in processes with thermal regeneration (CANSOLV, Sulphidine and ASARCO processes). The other two organic solvents are TEGDME and NMP. Special attention was paid to NMP due to its low cost and low viscosity, with its favorable properties, making it competitive as a solvent for FGD. TEGDME is a polar solvent, but it is not selective to SO2 and other gaseous components, so NMP has been suggested as an alternative solution. A regenerative process for SO2 removal, with TEGDME, has already found commercial application (Solinox process). NMP is already industrially used as a solvent in Lurgi's Purisol process, due to its nature for selective desulfurization of flue gases.Oksidi sumpora emituju se kao jedan od proizvoda u procesu sagorevanja čvrstih fosilnih goriva u termoelektranama, posebno kolubarskog i kostolačkog lignita u Republici Srbiji. Da bi se smanjio nivo emisije indirektnih gasova staklene bašte (GHG) iz stacionarnih izvora, neizbežna je primena tehnologije odsumporavanja dimnih gasova (FGD). Pored klasičnog krečnjačkog postupka, sve su češć i tehnološki postupci zasnovani na fizičkoj ili hemijskoj apsorpciji sumpornih oksida u rastvaraču i njegovoj termičkoj regeneraciji. Da bi se pravilno dizajnirao i optimizovao proces, važno je precizno odrediti termofizička svojstva čistih komponenti i njihovih smeša. U radu su prikazani rezultati određivanja gustine i viskoziteta dve binarne smeše, N,N-dimetilanilin (N,N-DMA) + tetra etilen glikol dimetil etar (TEGDME) i N,N-dimetilanilin (N,N-DMA) + N-metil-2-pirolidon (NMP). Merenja su vršena pomoću gustinomera Anton Paar DMA 5000 i Stabinger viskozimetra Anton Paar SVM 3000/G2, na atmosferskom pritisku. Dobijeni eksperimentalni rezultati su prikazani kao funkcija temperature i molskog udela N,N-DMA. N,N-DMA pripada grupi amina, a korišć en je kao sorbent za prečišć avanje dimnih gasova u procesima sa termičkom regeneracijom (CANSOLV, Sulphidine i ASARCO procesi). Druga dva organska rastvarača su TEGDME i NMP. Posebna pažnja je posveć ena NMP-u zbog niske cene i niskog viskoziteta, sa svojim povoljnim svojstvima, što ga čini konkurentnim kao rastvarač za FGD. TEGDME je polarni rastvarač, ali nije selektivan ka SO2 i druge gasovite komponente, pa je NMP predložen kao alternativno rešenje. Regenerativni proces za uklanjanje SO2, sa TEGDME, već je našao komercijalnu primenu (Solinox proces). NMP se već industrijski koristi kao rastvarač u Lurgi's Purisol procesu, zbog svoje prirode za selektivno odsumporavanje dimnih gasova.Procesing '24 : 37. Međunarodni kongres o procesnoj industriji : zbornik radova - Proceedings, 29-31. maj 2024, Beogra

Viskoznost binarne smeše DMA + 2-butanol za potencijalnu upotrebu kao rastvarača za regenerativne procese odsumporavanja dimnih gasova

Sulfur dioxide (SO2) is an environmental pollutant with multiple harmful effects on biological world. One of the main emission sources are industrial activities in thermal power plants, foundries and steel mills which involve combustion of fossil fuels containing sulfur, such as coal and oil. Initial step towards removal of SO2from flue gases was the so-called limestone process, a wet non-regenerative process that even today is the mostused flue gas desulfurization method. However, wet regenerative processes with gas absorption in liquid organic solvent and thermal regeneration recently have found practical application. Processes based on n,n-dimethylaniline (DMA) have alre-ady been patented and industrially applied. This solvent has high selectivity towards SO2in compa-rison to the other components of flue gas like CO2, and excellent binding capability by the 214• 32ndINTERNATIONAL CONGRESS ON PROCESS INDUSTRYmechanisms of chemical absorption, but main disadvantage is its high toxicity. On the other hand, in more ambient friendly 2-butanol binding of sulfur-dioxide occurs by means of physical absorption. Investigations have shown that mixtures of physical and chemical solvents usually show better cha-racteristics regarding binding capacityand selectivity than traditionally used aqueous solutions of amines, due to the synergetic effect.One of the most important thermophysical properties of solvents, necessary for process and equipment design is dynamic viscosity. In this investigation viscosity of binary mixture DMA + 2-butanol is experimentally determined in temperature and concentration range and correlated afterwards using different literature models. These correlations present useful method to acquire reliable data necessary for fluid flow analysis and mass and heat transfer calculations, since experi-mental values for desired process conditions are often not available. In this study, two or three-pa-rameter Eyring-UNIQUAC, Eyring-NRTL and McAllister models were used, while model that co-uples Eyring equation, Peng-Robinson equation of state and van der Waals mixing rule, was tested for simultaneous calculation of density and viscosity. The obtained results are presented and discu-ssed regarding potential application, limitations and complexity of used approach and models.Sumpor dioksid (SO2) je zagađivač životne sredine sa višestrukim štetnim efektima na biološki svet. Jedan od glavnih izvora emisije su industrijske aktivnosti u termoelektranama, livnicama i železarama, koje uključuju sagorevanje fosilnih goriva koja sadrže sumpor, kao što su ugalj i nafta. Početni korak u uklanjanju SO2 iz dimnih gasova bio je takozvani krečnjački postupak, mokri neregenerativni proces koji je i danas najčešće korišćen metod odsumporavanja dimnih gasova. Međutim, mokri regenerativni procesi sa apsorpcijom gasa u tečnom organskom rastvaraču i termalnom regeneracijom nedavno su našli praktičnu primenu. Procesi zasnovani na n,n-dimetilanilinu (DMA) su već patentirani i industrijski primenjeni. Ovaj rastvarač ima visoku selektivnost prema SO2 u poređenju sa drugim komponentama dimnog gasa kao što je CO2, i odličnu sposobnost vezivanja mehanizmima hemijske apsorpcije, ali glavni nedostatak je visoka toksičnost. S druge strane, u, sa stanovišta životne sredine prihvatljivijem, 2-butanolu do vezivanja sumpor-dioksida dolazi fizičkom apsorpcijom. Istraživanja su pokazala da smeše fizičkih i hemijskih rastvarača obično pokazuju bolje karakteristike u pogledu mogućnosti vezivanja i selektivnosti od tradicionalno korišćenih vodenih rastvora amina, zbog sinergetskog efekta. Jedno od najvažnijih termofizičkih svojstava rastvarača, neophodno za simulaciju procesa i proračun opreme, je dinamička viskoznost. U ovom istraživanju, viskoznost binarne smeše DMA + 2-butanol eksperimentalno je određena u temperaturnom i koncentracionom opsegu i nakon toga korelisana korišćenjem različitih literaturnih modela. Ove korelacije predstavljaju korisnu metodu za dobijanje pouzdanih podataka potrebnih za analizu protoka fluida i proračune prenosa mase i toplote, jer eksperimentalne vrednosti za željene uslove procesa često nisu dostupne. U ovom istraživanju korišćeni su dvo- ili troparametarski modeli Eyring-UNIQUAC, Eyring-NRTL i McAllister, dok je model koji povezuje Eyring jednačinu, Peng-Robinson jednačinu stanja i van der Waals pravilo mešanja testiran za istovremeno izračunavanje gustine i viskoznosti. Dobijeni rezultati su prikazani i diskutovani u pogledu potencijalne primene, ograničenja i složenosti korišćenog pristupa i modela

Volumetric and Viscometric Study of 1-Hexanol-Based Binary Systems: Experimental Determination and Modeling

Density, viscosity, and refractive index of four binary mixtures with 1-hexanol are experimentally determined at seven temperatures, in the temperature range from 288.15 to 318.15 K and at atmospheric pressure. The choice of mixtures was based on their potential for applications in flue gas cleaning processes. From experimental data, excess molar volume, viscosity deviation, excess molar Gibbs free energy of activation of viscous flow, deviation in refractive index, and partial and excess partial molar volumes are calculated, correlated with the Redlich-Kister equation, and used for better understanding of molecular interactions between the mixture components. Since the mixtures were investigated both from the theoretical point of view and with the aspect for practical applications, modeling of two key properties, viscosity and excess molar volume, was performed with different models and approaches and the results are compared with experimental values

Density, Viscosity, and Refractive Index Data for a Ternary System of Wine Congeners (Ethyl Butyrate plus Diethyl Succinate plus Isobutanol) in the Temperature Range from 288.15 to 323.15 K and at Atmospheric Pressure

Density, viscosity, and refractive index data for the ternary system ethyl butyrate + diethyl succinate + isobutanol and binary system ethyl butyrate + diethyl succinate have been measured in the temperature range 288.15-323.15 K, with temperature step of 5 K, and at atmospheric pressure. The measurements were performed on an Anton Paar DMA 5000 digital vibrating tube and, Anton Paar SVM 3000 digital viscometer, an Anton Paar RXA 156 refractometer. Based on the corresponding binary data as well as ternary data, presented in this work, excess molar volumes (V-E), viscosity deviations (Delta eta), and refractive index deviations (Delta n(D)) were determined and fitted by the Redlich-Kister and Nagata-Tamura polynomial equations. The influence of mixture composition on values of excess molar volume, deviation functions, and the molecular interactions present in the mixtures was further discussed

Volumetric and viscometric study and modelling of binary systems of diethyl tartrate and alcohols

Density, viscosity, refractive index and speed of sound have been measured for the pure ester diethyl tartrate at atmospheric pressure and over the temperature range from 288.15 K to 323.15 K. Detailed investigation regarding volumetric and viscometric properties was conducted under the same conditions for three binary mixtures: diethyl tartrate +1-propanol or +1-butanol or +1-hexanol. Excess and deviation functions have been calculated from experimental data and correlated with the Redlich-Kister equation. These functions were further discussed in terms of molecular interactions existing in the mixtures as well as the temperature influence on them. Additionally, excess molar Gibbs energies of activation of viscous flow and partial and excess partial molar volumes were determined for investigated systems. Modelling was performed for viscosity and excess molar volume and the obtained results were analyzed taking into account the applied approaches and models

Organic solvents review for sulphur-dioxide absorption from flue gases for regenerative processes with physical absorption

In addition to lime / limestone process, the most common procedure for sulfur-dioxide (SO2) removal from flue gases, separation processes with physical absorption and liquid organic solvent thermal regeneration recently gained importance. Organic liquid solvent selection, ahead of other process parameters, is crucial for process separation efficiency, in terms of the amount of SO2 absorbed by the solvent. The paper presents literature review and analysis of SO2 solubility in currently used and potential liquid organic solvents, polyethylene glycols (PEG 200 and PEG 400), tetraethylene glycol dimethyl ether (TEGDME), 1-methyl-2-pyrrolidone (NMP) as well as their binary mixtures with other components. The solvents in question bind SO2 by physical absorption mechanism, with the exception of NMP which binds SO2 by two parallel mechanisms, physical and chemical absorption. Research have even shown that mixtures of physical and chemical solvents or presence of both absorption mechanisms sometimes show better characteristics regarding binding capacity and selectivity. The importance of ionic liquids, as future solvents for separation processes, is particularly highlighted, due to their favorable thermophysical properties.Pored najrasprostranjenijeg, krečnjačkog postupka, za uklanjnje sumpor-dioksida (SO2) iz dimnih gasova, u novije vreme sve veći značaj dobijaju separacioni postupci sa fizičkom apsorpcijom i termičkom regeneracijom tečnog organskog solventa. Izbor solventa, ispred drugih procesnih parametara, ključan je za efikasnost procesa u pogledu stepena izdvajanja SO2. U radu je dat literaturni pregled i analiza rastvoljivosti SO2 u trenutno korišćenim i potencijalnim tečnim organskim solventima, polietilen glikolima (PEG 200 i PEG 400), tetraetilen glikol dimetil etru (TEGDME), 1-metil-2-pirolidonu (NMP) i za njihove binarne smeše sa drugim komponentama. Razmatrani solventi vezuju SO2 mehanizmom fizičke apsorpcije, sa izuzetkom NMP-a kod koga su prisutna dva paralelna mehanizma, fizička i hemijska apsorpcija. Istraživanja su čak pokazala da smeše fizičkih i hemijskih solvenata ili smeše u kojima su prisutni mehanizmi i fizičke i hemijska apsorpcije ponekad pokazuju bolje karaktristike u pogledu stepena izdvajanja i selektivnosti. Posebno je istaknut značaj jonskih tečnosti kao solvenata budućnosti za separacione proces, zbog svojih povoljnih termofizičkih svojstava.Power Plants 2016 : Proceeding of International Conference; November 23-26, 2016, Zlatibor, Serbi

Instrument za određivanje toplotne provodljivosti tečnih fluida na atmosferskom pritisku

Na polju toplotnog inženjerstva veliki napori su učinjeni u oblasti unapređenja konstrukcije opreme za prenos toplote, gde je visoka toplotna provodljivost tečnosti potrebna da bi se povećao prenos toplote. U mnogim oblastima gde postoji zahtev za hlađenjem, kao što je slučaj u automobilskoj, avio-industriji i mikroelektronici, jedan od ključnih faktora je upotreba specijalnih tečnosti sa povećanom toplotnom provodljivošću. U takvim okolnostima merenje toplotne provodljivosti tečnosti je važno u ocenjivanju efikasnosti prenosa toplote u toplotnim i rashladnim uređajima. Merenje toplotne provodljivosti tečnosti je u metrološkom smislu veći izazov od merenja toplotne provodljivosti supstanci u čvrstom stanju. Merenje toplotne provodljivosti moguće je kada je temperaturno polje nehomogeno, jer to izaziva transport toplote. Međutim, usled relativno slobodnog kretanja molekula u tečnosti i zavisnosti gustine svih supstanci (pa i tečnosti) od temperature, u tečnostima dolazi do spontanog strujanja tečnosti – tj. do prirodne konvekcije – što menja oblik temperaturnog polja i vrlo brzo otežava i na kraju praktično onemogućava merenje. Ovaj problem se može rešiti na više načina tako da postoje brojne merne metode koje su prilagođene merenju toplotne provodljivosti supstanci u tečnom agregatnom stanju