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Since the invention of fluidized bed systems to augment chemical reactions, numerous innovations were introduced to the system. These innovations result-in substantial improvement to the overall efficiency apart from resulting the fluidized bed system to become more compact. One of the innovations were the introducing of secondary air inside the bed so that a secondary motion in lateral direction can increase the amount of solid-gas interaction. This paper reviews various techniques proposed by researchers in providing secondary air inside the fluidized bed system. In general, four techniques were common in which the bed was named after: vortexing bed, cyclonic bed, rotating bed and swirling bed. Though resemble similarity, each of these beds were unique and comes with different advantageous. In conclusion, a fluidized bed system can be improved by the secondary motion in the bed which provides opportunities for further innovations.

Abstract. With the increasing demand for new and energy efficient drying methods of agricultural products, various techniques were deviced by researchers around the world. This techniques usually developed in laboratory scale prior to scale-up for actual industrial application. During this stage, modeling usually involved to aid scaling up process. This paper presents the modeling of drying kinetics of grated coconut using three semi emperical thin layer model. These models were Logarithmic, Modified Handerson and Pabis, and Verma et al models. Moisture ratio predicted by these models were compared against experimental drying carried out at four temperatures: 50°C, 60°C, 70°C and 80°C. The performance of these models were analyzed statistically using non-linear regression using LabFit software. The statistical parameters analyzed were coefficient of determination (R 2 ), reduced Chi-square (X 2 ), Root Mean Square Error (RMSE) and Residuals. Higher R 2 with lower X 2 , RMSE and Residuals implies good predictability of the models. From the analysis, it was found that Logarithmic model yields the best predictive capability of grated coconut drying kinetics with R 2 = 0.9996387, X 2 =0.505535x10 -3 , RMSE = 0.00623597 and Residuals = 0.0703607. IntroductionCoconut is believed to have its origins in the Indo-Malayan region, from where it spreaded throughout the tropics. Coconut palm is botanically referred to as the Cocos nucifera. It is known with high quality nutricious content and also rich in fiber, vitamins, and minerals. Today, the coconut is a domesticated plant and has become an essential resource for food, shelter, fuel and even medicine [1].Dried coconut is one of the coconut-derived products, and is used in the preparation of various desserts, e.g., donuts and ice cream. Traditionally, a tray dryer is used to produce dried coconut from the wet finely chopped coconut pieces. The process, however, takes very long time and yields a product that is not consistent, both in terms of colour and moisture content. This leads to a high rate of rejection of the dried product by the consumer. The need for an alternative drying technique that can produce a product faster and with higher quality therefore exists [2]. Rotary dryers and fluidized bed dryers are some of the examples of widely used drying techniques [3]. However, these techniques which were usually devided in laboratory scale requires scaling up to meet actual industrial demands, and hence mathematical modeling plays important role. Among these models were thin layer models which were widely used to predict drying kinetics of agricultural products.A comparison of green bell peppers drying and rehydration behaviours were studied on control samples and pre-heated samples with ethyl oleate solution by [4]. It was found that, samples drying time were inversely proportional with drying rate. While, rehydration ratio and drying rate of pre-heated samples was greater than control samples. The effective moisture diffusivity, D eff , were verified and moisture tran...