Heat transfer and fluid flow behaviour of a rectangular duct roughened with V-ribs with symmetrical gaps

Abstract

In the present work artificial roughness in the form V-ribs with symmetrical gaps have been applied on the heated surface to enhance the heat transfer in the limbs of V-ribs. Symmetrical gaps on both legs were provided by varying the relative gap width from 1 to 5 and number of gaps from 1 to 5. The relative roughness pitch, relative roughness height and aspect ratio of the rectangular duct are kept constant to the value of 10, 0.0433 and 12, respectively. The Nusselt number and friction factor of the artificially roughened absorber plates has been determined experimentally and corresponding values were compared with that of the smooth duct for the range of flow Reynolds number 4000-18000. The maximum enhancement in Nusselt number was reported for relative gap width of 4 and Number of gaps of 3. The thermohydraulic enhancement factor was found to be in order of the 1.54-2.39. IntroductionThe demand of producing more and more energy and depleting fossil fuels due to increasing population, industrialization and urbanization gives rise to develop highly efficient renewable thermal systems. Out of many renewable energy resources, solar energy is one of the most conspicuous and non exhaustible sources of energy source and have potential to fulfil daily energy need. Flat plate solar energy collector is the most elementary and the cheapest heat exchanger widely used for air heating applications. Flat plate collector is heated by exposing it to solar radiation and heat is transferred to the air flowing through the system mainly by convection. Due to low heat transfer coefficient between absorber plate and flowing air, the efficiency of solar air heater is considerably low. To make solar air heater more efficient, heat transfer rate from the absorber plate to flowing air need to be increased.

A detailed review on research, technology, configurations and application of wire ribs as artificial roughness in rectangular solar air heater duct

“…6.5. V-shape ribs [23][24][25][26][27][28][65][66][67][68][69]74 are of the shape of the English alphabet V, and its apex meets at the center of the duct. It has two inclined ribs meeting at halfway of the duct.…”

“…Maithani and Saini 27,69 carried out their investigation for V-ribs with symmetrical gaps roughness geometries. They have investigated the heat transfer and pressure drop of roughened SAH duct which is shown in supplementary Fig.…”

Enhanced Heat Transfer Performance in a Solar Air Heater using discrete V-Rib Geometry with Gap

“…They found maximum THP at P I /p = 0.6, r/e=3.5 and W/w = 7. Maithani et al [29] examined using V-shaped ribs with evenly spaced gaps as a type of artificial coarseness in a duct of a SAH. They reported that V-ribs with evenly spaced gaps artificial coarseness exhibited Superior performance compared other rib geometries.…”

Numerical modeling of an innovative arc shape rib based solar air heater

“…Moreover, some correlations have been presented for the Nusselt number and pressure drop in the proposed SAH with a AE 10% deviation. Maithani and Saini 43 presented a new design of SAH integrating V-ribs with symmetrical gaps. The maximum enhancement in terms of Nusselt number was obtained for a relative gap width of 4 and 3 gaps.…”