An empirical study on the effect of metal foam inserts on the pressure drop of R۱۳۴a flowboiling in horizontal tubes

Efforts to enhance two-phase heat transfer in heatexchangers are always accompanied by pressure droppenalties. Metal foams have been presented as potentialmaterials for improving heat transfer. The current studyintends to evaluate the boiling of R۱۳۴a refrigerant invarious ۱۰ and ۲۰ PPI copper foam configurations usedwithin ۸ mm internal diameter tubes. The impacts ofseveral factors on flow boiling pressure drop areinvestigated, including mass velocity, average vaporquality, and metal foam inserts. Experiments are carriedout at three different mass velocities of ۹۰, ۱۱۰, and ۱۳۰kg/m۲s, a constant heat flux of ۵.۰۲ kW/m۲, and fourdifferent vapor qualities ranging from ۰.۱۵ to ۰.۷۵. Despitetheir interesting capability in heat transfer augmentation,the results of the present work reveal that the pressure dropin presence of metal foams can be an order of magnitudegreater than in plain tubes, which limits their applications.Moreover, it was noted that in the presence of metalfoams, the pressure drop caused by acceleration isnegligible against the frictional term of pressure drop. Allthree parameters of mass flux, vapor quality, and metalfoam PPI, increasingly influence the pressure drop.

Keywords:

Metal foam , R۱۳۴a , Pressure drop , Boiling , Enhancement , Experimental.