This paper presents the thermohydraulic performance of rectangular solar air heater duct equipped with V-shaped rectangular perforated blocks attached to the heated surface. The V-shaped perforated blocks are tested for downstream (V-down) to the air flow at Reynolds number from 2000 to 20000. The perforated blocks have relative pitch ratio ( ) from 4 to 12, relative blockage height ratio ( ) from 0.4 to 1.0, and open area ration from 5% to 25% at a fixed value of angle of attack of 60° in a rectangular duct having duct aspect ratio ( ) of 12. Thermohydraulic performance is compared at different geometrical parameters of V-shaped perforated blocks for equal pumping power which shows that maximum performance is observed at a relative pitch of 8, relative rib height of 0.8, and open area ration of 20%. It is also observed that the performance of V-shaped perforated blocks was better than transverse-perforated blocks. 1. Introduction Degradation of fossil, fuels due to increasing world population, industrialization and urbanization gives rise to develop highly efficient and compact thermal systems. Moreover, there is a serious need to stimulate the contribution of renewable energy resources by enhancing the performance and developing the more compact economic viable thermal systems. From many renewable energy resources, solar energy is one of the brightest and nonexhaustible sources of energy which can only supply the increasing demand of energy. In the last few decades, performance of upgradation of energy exchange devices utilized for collection of solar energy is increasing rapidly. Flat plate solar energy collector is incontrovertible one of the simplest and cheapest heat exchanger widely used for air heating applications. Flat plate collector is heated by exposing the solar radiation on it, which transfers heat to the air flowing through the system mainly by convection. Due to low heat transfer coefficient between absorber plate and flowing air, the performance of solar air heater is poor. In order to make solar air heater efficient, heat transfer rate from absorber plate to flowing air needs to be increased in solar air heater duct. An artificial roughness in the form of small wires is widely used method for the enhancements of convective heat transfer which creates turbulence at heat transfer surface. Earlier studies carried out on artificial roughness in the form of small wires of different geometries like transverse ribs [1, 2], W-shaped ribs [3], arch shaped ribs [4], protruded roughness [5], inclined discrete ribs [6], V-shaped ribs [7],
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