## THERMAL SCIENCE

International Scientific Journal

### EFFECT OF WAVY FIN USAGE ON THERMAL PERFORMANCE OF HEAT EXCHANGER USED IN COMBI BOILERS

**ABSTRACT**

In this study, performance of a heat exchanger used in combi boilers was investigated numerically for different fin geometries. Analyses were performed at the boiler operation conditions. A commercial computational fluid dynamics (CFD) software package (FLUENT) was used for numerical simulations. 3-D steady-state turbulent flow field analysis was carried out and k-ε model was preferred as the turbulence model. In the analysis, it was assumed that the heat transfer phenomenon occurred both by conduction and convection. Flat fin geometry was taken as a reference for the investigation. Variation of the heat transfer and pressure drop values for the wavy fin were compared with the reference geometry. The wave angle and wave radius were taken as the parameters for the wavy fins. For different fin geometries; the outlet temperature of the combustion gases, the heat transfer to the water and the pressure drop were calculated and the results were presented. Compared with flat fin, average decrease for the outlet temperature of hot gases was obtained as 4 K and average increase for the heat transfer to the water was calculated as 0,68 W. On the other hand, the average pressure drop in the heat exchanger with wavy fins was about 70% higher than the flat fin.

**KEYWORDS**

PAPER SUBMITTED: 2018-03-30

PAPER REVISED: 2018-06-13

PAPER ACCEPTED: 2018-06-14

PUBLISHED ONLINE: 2018-09-30

**THERMAL SCIENCE** YEAR

**2020**, VOLUME

**24**, ISSUE

**2**, PAGES [693 - 700]

- Benim, A.C., Cagan, M. and Gunes, D., Computational Analysis Of Transient Heat Transfer In Turbulent Pipe Flow, Int. J. Therm. Sci., 43 (2004), 8 SPEC. ISS., pp. 725-732
- Benim, A.C., Ozkan, K., Cagan, M. and Gunes, D., Computational Investigation Of Turbulent Jet Impinging Onto Rotating Disc, Int. J. Numer. Methods Heat&Fluid Flow, 17 (2007), 3, pp. 284-301
- Chattopadhyay, H., Benim, A.C., Turbulent Heat Transfer Over A Moving Surface Due To Impinging Slot Jets, J. Heat Transfer, 133 (2011), 10, Article number:104502, 5 pages
- Benim, A.C., Chattopadhyay, H. and Nahavandi, A., Computational Analysis Of Turbulent Forced Convection In A Channel With A Triangular Prism, Int. J. Therm. Sci., 50 (2011), 10, pp. 1973-1983
- Bhattacharyya, S., Chattopadhyay, H. and Benim, A.C., Simulation Of Heat Transfer Enhancement In Tube Flow With Twisted Tape Insert, Prog. Comput. Fluid Dyn., 17 (2017), 3, pp. 193-197
- Oclon, P., Lopata, S., Nowak, M. and Benim, A.C.,Numerical Study On The Effect Of Inner Tube Fouling On The Thermal Performance Of High-temperature Fin-and-tube Heat Exchanger, Progess Comput. Fluid Dyn., 15 (2015), 5, pp. 290-306
- Wang, C.C., Fu, W.L. and Chang, C.T., Heat Transfer And Friction Characteristics Of Typical Wavy Fin-and-tube Heat Exchangers, Exp. Therm. Fluid Sci., 14 (1997), 2, pp. 174-186
- Jang, J., Chen, L., Numerical Analysis Of Heat Transfer And Fluid Flow In A Three-dimensional Wavy-fin And Tube Heat Exchanger, Int. J. Heat Mass Transf., 40 (1997), 16, pp. 3981-3990
- Tao, Y.B., He, Y.L., Huang, J., Wu, Z.G. and Tao, W.Q., Numerical Study Of Local Heat Transfer Coefficient And Fin Efficiency Of Wavy Fin-and-tube Heat Exchangers, Int. J. Therm. Sci., 46 (2007), 8, pp. 768-778
- Junqi, D., Jiangping, C., Zhijiu, C., Yimin, Z. and Wenfeng, Z., Heat Transfer And Pressure Drop Correlations For The Wavy Fin And Flat Tube Heat Exchangers, Appl. Therm. Eng., 27 (2007), 11-12, pp. 2066-2073
- Pourahmad, S., Pesteei, S.M., Effectiveness-NTU Analyses In A Double Tube Heat Exchanger Equipped With Wavy Strip Considering Various Angles, Energy Convers. Manag., 123 (2016), pp. 462-469
- Sakr, M., Convective Heat Transfer And Pressure Drop In V-corrugated Channel With Different Phase Shifts, Heat Mass Transf., 51 (2015), 1, pp. 129-141
- Wang, J., Gao, X., and Li, W., Flow And Heat Transfer Characteristics In A Channel Having Furrowed Wall Based On Sinusoidal Wave, Korean J. Chem. Eng., 32 (2015), 11, pp. 2187-2203
- Rashidi, M.M., Hosseini, A., Pop, I., Kumar, S. and Freidoonimehr, N., Comparative Numerical Study Of Single And Two-phase Models Of Nanofluid Heat Transfer In Wavy Channel, Appl. Math. Mech. (English Ed., 35 (2014), 7, pp. 831-848
- Goyal, R., Bhargava, R., EFGM Simulation Of Pulsating Doublediffusive Effect On Transpiration Cooling In Nanofluid Filled Wavy Channel, Int. J. Appl. Comput. Math., 3 (2017), 3, pp. 1847-1860
- Singh, N., Sivan, R., Sotoa, M., Faizal, M. and Ahmed, M.R., Experimental Studies On Parallel Wavy Channel Heat Exchangers With Varying Channel Inclination Angles, Exp. Therm. Fluid Sci., 75 (2016), pp. 173-182
- Bahaidarah, H.M.S., Sahin, A.Z., Thermodynamic Analysis Of Fluid Flow In Channels With Wavy Sinusoidal Walls, Therm. Sci., 17 (2013), 3, pp. 813-822
- Gui, X., Song, X., Li, T. and Tang, D., Analysis On Three-Dimensional Flow And Heat Transfer In A Cross Wavy Primary Surface Recuperator For A Microturbine System, Therm. Sci., 19 (2015), 2, pp. 489-496
- Gülcan, Ö.E., Numerical Analysis of Heat Exchanger Used in Combi Boilers, Postgraduate thesis, Sakarya University, Sakarya, Turkey, 2015
- Ansys, I., ANSYS FLUENT Theory Guide, Knowl. Creat. Diffus. Util., 15317 (2009), November, pp. 724-746
- Cengel, Y.A., Heat And Mass Transfer: A Practical Approach, 2006