The paper presents the numerical study on the influence of inner tube surface fouling on the thermal performance of a high temperature fin-and-tube heat exchanger. The heat exchanger is used to cool down the hot flue gas. In order to simplify the heat transfer model, only the gas flow through the passage formed by the six consecutive fins is analysed. Fouling on the inner surface of the tube wall in a form of scale can cause large decline in heat transfer ability. Since the gas in the outer space is, then, not cooled efficiently, the temperature on the outer wall can increase, even above the allowable strength limits. Because the gas flow path through passages formed between fins is complex, the CFD simulations were conducted in order to determine the velocity and temperature variations for flue gas flow in the inter-tubular space of a cross-flow heat exchanger. The total heat transfer rate, outlet gas temperature and the maximum temperature of tube wall for various gas inlet velocities were determined.

Solar photovoltaic (PV) energy is one of the most viable renewable energy sources, considered less polluting than fossil energy. However, the average power conversion efficiency of PV systems is between 15% and 20%, and they must operate with high efficiency. Photovoltaic cells have non-linear voltage–current characteristics that are dependent on environmental factors such as solar irradiation and temperature, and have low efficiency. Therefore, it becomes crucial to harvest the maximum power from PV panels. This paper aims to study and analyze the most common and well-known maximum power point tracking (MPPT) algorithms, perturb and observe (P&O) and incremental conductance (IncCond). These algorithms were found to be easy to implement, low-cost techniques suitable for large- and medium-sized photovoltaic applications. The algorithms were tested and compared dynamically using MATLAB/Simulink software. In order to overcome the low performance of the P&O and IncCond methods under time-varying and fast-changing solar irradiation, several modifications are proposed. Results show an improvement in the tracking and overall system efficiencies and a shortened response time compared with original techniques. In addition, the proposed algorithms minimize the oscillations around the maximum power point (MPP), and the power converges faster.

In this paper, the effect of various shapes of ribs used in Solar Air Heaters (SAHs) was discussed. The review is concentrated on the geometry of the rib and its location on the SAH panel. Both numerical and experimental works were considered for discussion with dry air and Nano fluids as a working fluid. The influence of various shapes, such as an L shape, W shape, V shape, Multiple V shape, V shape with a gap, detachable & attachable ribs etc., was analyzed. The common fact observed from this analysis is that the implementation of artificial roughness in the absorber plate results in a considerable increase in the rate of heat transfer. Further, it is observed that ‘Multiple V-shaped with open between the ribs’ results in the maximum thermal enhancement when compared to the other shapes.