Impact of neglecting the variations in the relative surface roughnesses of capillary tubes on the accuracy of a capillary tube model

Lorbek, Luka (avtor), Katrašnik, Tomaž (avtor), Kitanovski, Andrej (avtor)

Capillary tube models frequently rely on friction factor correlations, which are functions of the Reynolds number, and the tube's relative surface roughness. However, this study shows that explicitly correlating the friction factor with the relative surface roughness is unnecessary, at least when the latter is lower than 0.0025. To test this a correlation was fitted directly onto friction factor measurements obtained in an adiabatic flow of R600a, through nine capillary tubes from three manufacturers. The friction factor was correlated exclusively as a function of the Reynolds number, meaning that the impacts of the relative surface roughnesses on the friction factor were averaged, and included only implicitly. This correlation, and an existing correlation, which allows the specification of the relative surface roughness, were then implemented in a capillary tube model. The accuracy of the capillary tube model, using either the developed or existing correlation was then evaluated by comparing the results to experimental data. No significant decrease in the accuracy of the model was observed when the relative surface roughnesses, ranging from 0.0012 to 0.0025, were not individually specified for each capillary tube. To further verify this, the procedure was repeated on a larger database of friction factor and mass flow rate measurements, which also consisted of data from independent studies. Similar conclusions were drawn, as the average accuracy of the model differed only by 1 to 3% among different studies, and not always in favor of the correlation where the relative surface roughnesses could be specified.

• Jezik: Angleški jezik
• Ključne besede: vapor-compression system, refrigerant flow, capillary tubes, relative surface roughness, friction factor correlation
• Vrsta gradiva: Članek v reviji
• Tipologija: 1.01 - Izvirni znanstveni članek
• Organizacija: FS - Fakulteta za strojništvo
• Status publikacije: Objavljeno
• Različica publikacije: Recenzirani rokopis
• Leto izida: 2021
• Št. strani: Str. 194-203
• Številčenje: Vol. 129
• PID: 20.500.12556/RUL-128036
• UDK: 621.56:519.8(045)
• ISSN pri članku: 0140-7007
• DOI: 10.1016/j.ijrefrig.2021.04.022
• COBISS.SI-ID: 61519619
• Datum objave v RUL: 01.07.2021

Gradivo je del revije

• Naslov: International journal of refrigeration
• Skrajšan naslov: Int. j. refrig.
• Založnik: Elsevier Science
• ISSN: 0140-7007
• COBISS.SI-ID: 9140997

Licence

• Licenca: CC BY-NC-ND 4.0, Creative Commons Priznanje avtorstva-Nekomercialno-Brez predelav 4.0 Mednarodna
• Povezava: http://creativecommons.org/licenses/by-nc-nd/4.0/deed.sl
• Opis: Najbolj omejujoča licenca Creative Commons. Uporabniki lahko prenesejo in delijo delo v nekomercialne namene in ga ne smejo uporabiti za nobene druge namene.
• Začetek licenciranja: 19.04.2021

Sekundarni jezik

• Jezik: Slovenski jezik
• Ključne besede: parno-kompresijski sistemi, tok hladiva, kapilarne cevi, relativna hrapavost, faktor trenja

Projekti

• Financer: ARRS - Agencija za raziskovalno dejavnost Republike Slovenije
• Program financ.: Mladi raziskovalci