An accurate prediction of the flow structure and heat distribution in rhombic configurations are of greater importance due to its significant engineering i.e. cooling of electronics devices as well as natural applications i.e. geothermal extraction. Heatline method is used to analyze natural convection in porous rhombic enclosures with various inclination angles, phi for differential (case 1) and Rayleigh-Benard heating situations (case 2). Increase in phi (phi = 90 degrees) results in pure conduction dominant heat transfer with stagnant fluid condition for phi = 90 degrees at Da = 10(-5) and a slight perturbation of phi at higher Da (Da >= 4 x 10(-5)) leads to convection based dynamic solution for phi = 90 degrees in case 2 irrespective of Pr. At Da = 10(-3), strength of fluid and heat flow increase with phi due to enhanced convection effect and phi = 90 degrees shows maximum magnitude of streamfunction (psi(max)) and heatfunction (Pi(max)) values in both cases except convection based solution at phi = 90 degrees for Pr = 7.2. Both cases are compared based on local (Nu) and average Nusselt numbers ((Nu) over bar) and those are adequately explained based on heatlines. Also, (Nu) over bar increases with Da in both cases except convection based solution at phi = 90 degrees for Pr = 7.2. Overall, (Nu) over bar is higher for case 2 at phi <= 45 degrees whereas case 1 shows larger (Nu) over bar for phi >= 45 degrees irrespective of Pr at Da = 10(-3). Hence, phi = 45 degrees is the critical rhombic angle which demarcates the heating strategies of case 1 and case 2 to achieve higher heat transfer rates ((Nu) over bar) in various applications. (C) 2012 Elsevier Ltd. All rights reserved.