Thermal-hydraulic experimental study of louvered fin-and-flat-tube heat exchanger under wet conditions with variation of inlet humidity ratio

• Published in: Applied thermal engineering Vol. 183; p. 116218
• Main Authors: Ayad, F., Benelmir, R., Idris, M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 25.01.2021; Elsevier BV; Elsevier
• Subjects: Aerodynamics; Air intakes; Cooling coils; Dehumidification; Dehumidifying; Engineering Sciences; Evaporators; Experimental study; Fin-and-tube heat exchanger; Fluid dynamics; Fluid flow; Friction factor; Heat conductivity; Heat exchangers; Heat transfer; Humidity; Louvered fins; Mathematical models; Relative humidity; Thermal-hydraulic performance; Tube heat exchangers; Thermal-hydraulic performance; Experimental study; Dehumidifying; Louvered fins; Fin-and-tube heat exchanger
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2020.116218

•Performance of louvered fin, used in an automotive evaporator, is experimentally characterized.•Colburn ‘j’ and Fanning ‘f’ factor curves are plotted, under wet condition, for various inlet humidity ratio.•At low Reynolds number, unlike fwet factor, jwet factor is insensitive to the humidity ratio variation.•As Re increases, with inlet humidity increasing, jwet reduces (up to 23%) while fwet increases (up to 43%). An experimental study for air-side thermal-hydraulic performance of louvered fin-and-flat-tube heat exchanger under dehumidifying conditions has been performed. The louvered fin studied, used for an automotive evaporator, is geometrically defined by a flow depth of 47 mm, a high louver angle of 50° and a louver pitch of 1.1 mm. The test was conducted for frontal air velocity ranging from 1.1 to 4.5 m/s. The heat exchanger was tested first in dry condition, working as a heater. In wet conditions, the cooling coil was tested for three air inlet temperatures, Ta, and for various inlet relative humidity, RH, organized as follows: Ta = 30 °C (RH = 40 to 70%), Ta = 35 °C (RH = 30 to 60%), and Ta = 40 °C (RH = 20 to 60%); which correspond to a variation of the inlet humidity ratio from 9.2 to 27.7 gwater/kgdry-air. It was found that, for all inlet conditions, the wet friction factor is higher than that for dry surface (up to 43%). Concerning the heat transfer performance, at low Reynolds number, the sensible Colburn ‘j’ factor is insensitive to the surface conditions. However, as Re number increases, the sensible wet j factor decreases (up to 23%) compared to the dry one. This degradation is more and more pronounced as the inlet humidity ratio increases.