Investigation of Heat Transfer by Natural Convection in an Open Channel
Experimental study of natural convection heat transfer inside smooth and rough surfaces of vertical and inclined equilateral triangular channels of different inclination angles with a uniformly heated surface are performed. The inclination angle is changed from 15º to 90º. Smooth and rough surface of average roughness (0.02mm) are used and their effect on the heat transfer characteristics are studied. The local and average heat transfer coefficients and Nusselt number are obtained for smooth and rough channels at different heat flux values, different inclination angles and different Rayleigh numbers (Ra) 6.48 × 105 ≤ Ra ≤ 4.78 × 106. The results show that the local Nusselt number decreases with increase of axial distance from the lower end of the triangular channel to a point near the upper end of channel, and then, it slightly increases. Higher values of local Nusselt number for rough channel along the axial distance compared with the smooth channel. The average Nusselt number of rough channel is higher than that of smooth channel by about 8.1% for inclined case at θ = 45o and 10% for vertical case. The results obtained are correlated using dimensionless groups for both rough and smooth surfaces of the inclined and vertical triangular channels.
Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1100623Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1852
 Abdul-Aziz M., "Heat transfer by natural convection from the inside surface of a uniformly heated tube at different angles of inclination," M.S. Thesis, Mech. Eng. Dept., Al-Azhar University, Cairo, Egypt, 1991.
 Hussein A. and Yasin K., "Heat transfer by natural convection from a uniformly heated vertical circular pipe with different entry restriction configurations," Energy Conversion & Management, vol.48, 2007, pp.2244-2253.
 Sarhan A., Kamis M. and Moawed M.," Heat transfer by natural convection in vertical and horizontal annuli," Al-Azhar Univ Eng. J. 4, , Cairo, Egypt, 2001.
 Hosseini R., Heyrani-Nobari M.,and Hatam M.,"An experimental study of heat transfer in an open-ended vertical eccentric annulus with insulated and constant heat flux boundaries," Applied Thermal Engineering, vol. 25, 2005, pp.1247-1257.
 Omara M., Elshazly K., Moawed M. and Ibrahim E. ,"Heat transfer by free convection from the inside surface of the vertical and inclined elliptic tube," Energy Conversion & Management, vol.46, 2005, pp. 1443-1463.
 Moawed M. and Ibrahim E. ,"Free convection heat transfer inside vertical and inclined elliptic tubes with different axis ratio and different inclination and orientation angles," Energy Conversion & Management, vol.49, 2005, pp. 587–595.
 Amr O., Emad Z. and Sayed A. "Free convection from a constant heat flux elliptic tube," Energy Conversion and Management, vol.44, 2003, pp. 2445–2453.
 Nada S.A. ,"Natural convection heat transfer in horizontal and vertical closed narrow enclosures with heated rectangular finned base plate," Int. J. of Heat and Mass Transfer,vol. 50 ,2007, pp. 667-679.
 Varol Y., Koca A. and Hakan F.," Natural convection in a triangle enclosure with flush mounted heater on the wall," Int. Commun. In Heat and Mass Transfer, vol.33 , 2006, pp. 951-958.
 Seleem K. and Kamel A. ,"Experimental study of inclination angle and surface area effects for longitudinally finned cylinder on free convection heat transfer in an open enclosure," Journal of Engineering and Technology, Baghdad, Iraq ,vol.27, 2009, pp. 171-179.
 Abdlmonem B. and Michel A., "The effect of surface roughness on the average heat transfer of an impinging air jet," Int Commun in Heat and Mass Transfer, vol.27, 2000, pp. 1-12.
 Majid B., Michael M. and Richard J. "Role of random roughness on thermal performance of microfins", Journal of Thermophysics and Heat Transfer, vol.21, 2007, pp. 153-157.
 Hany A., Omara M., Mahmoud S. and Mohamed F. Experimental study of natural convection heat transfer through horizontal open ended equilateral triangular channels, Journal of Engineering Sciences, University of Assiut, Egypt. , vol.40, 2012, pp. 1091-1103.