To increase the efficiency of any heat transfer processes which involves heat recovery from hot fluid or removal of excess heat via processing of cold fluid, the loss in available energy due to various irreversibilities must be analyzed in terms of entropy generation. In the present study, hot or cold fluid is passed through the inclined tubes with a square cross section, and the entropy generation characteristics within the entrapped fluid in triangular space during natural convection is the subject of investigation. The tubes are surrounded by cold fluid while hot fluid is passed through the tubes and vice versa. Thus, hot inclined walls with cold horizontal walls (case 1) and cold inclined walls with hot horizontal walls (case 2) are considered as boundary conditions during convection (Ra = 103 to 105) for various fluids (Pr = 0.015, 0.7, and 1000) within/surrounded by the tubes. Entropy generation maps (Sθ and Sψ) with heat transfer characteristics (ψ and θ) are analyzed for both the cases. Minimum sp...