Experimental study of ammonia flow boiling in a vertical tube bundle: Part 3 – Enhanced dimple tube with 2/3rd height solid round PVC nonconductive rod. (February 2022)

• Record Type: Journal Article
• Authors: Ayub, Zahid; Abbas, Ahmad; Ismail, Tauseef; Ayub, Adnan; Li, Wei; Khan, Tariq S.; Ribatski, Gherhardt
• Is Part Of: International journal of refrigeration. Volume 134(2022)
• Page Start: 64
• Page End: 73
• Publication Date: 2022-02
• Subjects: Ammonia -- Annular flow -- Boiling -- Enhanced tubes -- Evaporator -- Refrigeration; Ammoniac -- Ébullition -- Froid [artificiel] -- Évaporateur -- Tubes améliorés -- Écoulement annulaire; Refrigeration and refrigerating machinery -- Periodicals; 621.56
• DOI: 10.1016/j.ijrefrig.2021.11.006
• Languages: English
• ISSNs: 0140-7007

Abstract

Highlights: Boiling of ammonia in a vertical dimpled tube bundle with 33% cut round PVC nonconductive rods. Study of wide range of experimental parameters. Enhanced heat transfer coefficient compared to previous studies. Abstract: This paper presents the experimental results of saturated two-phase flow ammonia in a vertical shell and tube heat exchanger comprising of seven dimpled enhanced tubes with solid PVC nonconductive round rods inserted in the lower 2/3rd section of each tube creating 67% annular section. The source of heat was hot ethylene glycol/water solution flowing on the shell side. The range of saturation temperature for ammonia was -20 °C ≤ T sat ≤ -2 °C, heat flux range 5 kW m −2 ≤ q ˙ ≤ 45 kW m −2, exit vapor quality range 0.1 ≤ x ≤ 0.9 and mass flux 76.9 kg m −2 s −1 ≤ G ≤ 145.7 kg m −2 s −1 . For each saturation temperature, the effects of heat flux and mass flux were studied while the exit vapor quality at each mass flux varied between 0.1 and 0.9. Around 40% increase in heat transfer performance was observed with saturation temperature between –20 and –2 °C at exit vapor quality of 0.7. Heat transfer performance also increased with heat flux at fixed mass flux at each saturation temperature while the performance showed initial increase with quality and then a drop at the onset of dry out.