M.W. Kareem

A Review of Solar Air Heater for Drying of Agricultural Products

Bulk of farm products need to be preserved because of their perishable nature. The cheapest and environmental friendly means is indirect usage of solar irradiance to reduce the moisture content of these products to a level that cannot sustain the activities of micro-organisms. The research on solar collector has gained its popularity over the years due to mans quest for green energy which has led to increase in demand for the utilization of solar energy. Harnessing of solar energy by man for drying purposes was predominantly by direct method which reduces the quality and quantity of the dried products. This work presents the most recent contributions on solar air heater of flat plate absorber category. Various models, material of component parts and performance efficiency of these air heaters were discussed and there is need for collector optimization. The study was concluded with a focus on multiple pass approach of solar harvesting.

Numerical modelling of multi-pass solar dryer filled with granite pebbles for thermal storage enhancement

In this paper, a theoretical modelling of a cheap solar thermal dryer for small and medium scale farmers with multi-pass approach has been investigated. Comsol Multiphysics modelling tool was employed using numerical technique. The rock particles were used to enhance the thermal storage of the drying system. The local weather data were used during the simulation while parameters and coefficients were sourced from literature. An improvement on efficiency of up to 7% was recorded with error of 10-5 when compared with the reported double pass solar collector. A fair distribution of hot air within the cabinets was also achieved. Though the modelling tool used was robust but the characterization of the system materials need to be done to improve the system accuracy and better prediction.

Dynamic Modeling of Solar Air Collector with Thermal Storage Material

The investigation of solar air heater using SIMULINK tool to predict the transient state of solar thermal collector is presented in this article. The modeling is primarily centered on the solar crop drying system for small and medium scale farmers. Double transparent walls and sensible heat storage rocks were used in the modeling to aid the performance efficiency of the flat plate solar collector. The simulation was run with variable steps solver of relative tolerance of 0.001 using Dormand-Prince technique. The outcome of this investigation revealed the time trend of solar irradiance, effects of laminar forced convection on thermal coefficient, and early performance efficiency ratio. However, the model required improvement for it to accurately predict the system efficiency ratio after long period of operation.

Numerical and experimental investigation of direct solar crop dryer for farmers

This article presents a theoretical and experimental investigation on effects of weather on direct solar crop drying technique. The SIMULINK tool was employed to analyze the energy balance equations of the transient system model. A prototype of the drying system was made and data were collected between the months of June and July in Perak, Malaysia. The contribution of intense sunny days was encouraging despite the wet season, and the wind velocity was dynamic during the period of investigation. However, high percentage of relative humidity was observed. This constitutes a hindrance to efficient drying process. The reported studies were silent on the effect of thick atmospheric moisture content on drying rate of agricultural products in tropic climate. This finding has revealed the mean values of insolation, wind speed, moisturized air, system performance efficiency and chili microscopy image morphology. The predicted and measured results were compared with good agreement.

Lumped Components Modeling of Double Pass Solar Collector with Porous Matrixes

In this report, the modeling and simulation of a double pass solar air absorber was carried out using combination of Simscape and Simulink modeling tools. The solar system air mass flow rate and the porous media were critically investigated by using local weather data of Seri Iskandar, Perak, Malaysia. Optimal inlet air flow rate of 0.034kgm-2s-1 was obtained and one of the packed beds, sandstone extended the thermal transfer period of solar collector system by 1150s which displayed good agreement with the reported model and experimental outcomes. The results obtained have shown that it is a promising alternative tool for solar thermal experimentation modeling.