Experimental testing of solar-based air heater roughed with discrete V-down rib and staggered element.

A rough rectangular channel of solar-based air heater (SBAH) is made and tested. The work consists of an effort to perceive the proportion of heat discharge and frictional behavior of air passing over a roughened rectangular channel. The absorber surface of SBAH is roughed with discrete V-down rib and staggered element roughness having different values of relative rib pitch (P/e) that ranged from 6 to 14. Fixed parameters such as relative gap size (g/e), relative staggered element pitch (P'/P), numeral of gaps (Ng), relative staggered element size (r/g), and relative rib height (e/D) are considered 4, 0.4, 3,1, and 0.0433, respectively, all throughout the study. The flow Reynolds number (Re) changes from 4000 to 14,000; consequently the Nusselt number (Nu) and friction factor (f) reach up to 2.16 and 2.73 times, respectively, with respect to plane surface. The optimum rise in terms of thermal-hydraulic performance (THP) is gained analogous to a P/e of 10. The correlation for heat transfer function, R(e+), and roughness function, G(e+), is given to anticipate the performance of roughness.

A critical review on different roughness geometries and their effect on heat transfer and friction factor.

Solar air heater (SAH) is simple and the greatest effective approach to utilize and convert solar energy into thermal energy for heating utilizations. The employment of artificial roughness under side of the observer surface is the key technique for augmenting heat transfer with minimal friction factor penalty. Current paper summarized different kinds of artificial roughness used in SAH, which augments its performance. In this review article, 96 research papers are cited, which provide detailed information about the effect of different geometrical parameters on heat transfer and friction factor. This paper also brings the information about the optimum roughness parameters and heat transfer and friction factor correlation developed by different investigators in tabular form. Optimum roughness parameters and empirical correlations are used for comparative analysis of heat transfer, friction factor, and thermo-hydraulic performance parameter (THPP) of different roughness geometries. The best performing roughness geometry is reported on the basis of comparative analysis. Mathematical model is developed for predicting the thermal efficiency (ηth) of roughened SAH duct.

Performance analysis of multi-gap V-roughness with staggered elements of solar air heater based on artificial neural network and experimental investigations.

Among all renewable energy sources, solar power is one of the major sources which contributes for pollution control and protection of environment. For a number of decades, technologies for utilizing the solar power have been the area of research and development. In the current research, thermal performance parameters of multi-gap V-roughness with staggered elements of a solar air heater (SAH) are experimentally investigated. The artificial neural network (ANN) is also utilized for predicting the thermal performance parameters of SAH. Experiments were executed in a rectangular channel with one roughened side at the top exposed to a uniform heat flux. A significant rise in thermal efficiency performance was reported under a predefined range of Reynolds number (Re) from 3000 to 14000 with an optimized value of relative roughness pitch ratio (P/e) and relative staggered rib length (w/g) as 12 and 1, respectively. The maximum thermal efficiency was attained in the range from 42.15 to 87.02% under considered Reynolds numbers for optimum value of P/e as 12 and w/g as 1. A multilayered perceptron (MLP) feed-forward ANN trained by the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm was utilized to predict the thermal efficiency (ηth), friction (f), and Nusselt number (Nu). The thermal performance parameters such as P/e, w/g, Re, and temperature at the inlet, outlet, and plate were the critical input parameters/signals used in the ANN method. The optimum ANN arrangement/structure to predict the Nu, f, and ηth demonstrate higher accurateness in assessing the performance characteristics of SAH by attaining the root mean squared error (RMSE) in prediction and the Pearson coefficient of association (R2) of 1.591 and 0.994; 0.0012 and 0.851; and 0.025 and 0.981, respectively. The prediction profile plots of the ANN demonstrate the influence of various input parameters on the thermal performance parameters.

Effect of fabricated V-rib roughness experimentally investigated in a rectangular channel of solar air heater: a comprehensive review.

Solar power is one of the main sources of renewable energy which helps for protecting the environmental and reducing pollution. Technologies and systems for utilizing solar power are the area of research and development for a number of decades. In a solar air heater (SAH), use of fabricated irregularities on its wide face is an effective technique to augment heat discharge for flowing air with a moderate rise in frictional conduct. The necessary conditions for building an effective roughness design are to pick roughness patterns and its geometrical factors such that they may govern the nature of fluid flow with a rise in the heat discharge and lowering pumping losses. Continuous efforts are being carried out by various researchers to optimize the roughness parameters that deliver high heat release rates with low cost of pressure penalty or better thermo-hydraulic performance parameter (THPP). The researchers dominantly studied V-shaped of roughness design because of its better performance characteristics. The main intent of the present paper is to appraise or compile the influence of various V-shaped rib roughness on the thermal behavior of SAH. The outcomes of different V-designed rib roughness in terms of Nusselt number (Nu), and friction factor (f), statistical correlations established related to geometrical parameters and THPP are summarized. A comparative study using different V-designed ribs are also discussed to guide the future research and improvements.