PRELIMINARY STUDY OF SEAWEED DRYING UNDER A SHADE AND IN A NATURAL DRAFT SOLAR DRYER

Internat. J. Sci. Eng., Vol. 8(1)2015:10-14, January 2015, Hooi-Kim Phang et al. International Journal of Science and Engineering(IJSE) Home page: http://ejournal.undip.ac.id/index.php/ijse Preliminary Study of Seaweed Drying under A Shade and in A Natural Draft Solar Dryer Hooi-Kim Phang#), Chi-Ming Chu, Sivakumar Kumaresan, Md. Mizanur Rahman, Suhaimi Md. Yasir #)Thermal and Environment Research Group,Materials and Minerals Research Unit, Faculty of Engineering, Universiti Malaysia Sabah, Jalan UMS, 88400 Kota Kinabalu, Sabah, Malaysia. Email: Abstract -A solar dryer was designed to study the seaweed drying process under natural convection and compared to a shade drying process. A dewatering pre-treatment process was initially applied to enhance drying process for both methods. The initial weight of seaweed before pre-treatment and after pre-treatment was recorded and the seaweed was then introduced into the solar drying system and shade drying system. The air temperature and relative humidityinside the solar dryer and surrounding were recorded during experiment. A representative sample on each tray was taken or final moisture content determination where the difference of seaweed weight less than 5% for subsequent measurement. The average weight loss of seaweed from pre-treatment was about 54%. The final moisutre content of seaweed for solar drying was in the range of 24-61% (db) and shade drying was in the range of 40-48% (db) with a standard deviation of final moisture content of 20.45% for solar drying and 3.78% for shade drying. The total time for solar drying inclusive of pre-treatment was 6 days and shade drying was 9 days. The drying kinetics of each method was modeled and the results of this study will be utilized to enhance the design and operations of seaweed solar dryers. Keywords—Seaweed, drying, solar drying, shade drying Submission: May 10, 2014 Corrected : June 8, 2014 Accepted: 1 September , 2014 Doi: 10.12777/ijse.8.1.10-14 [How to cite this article: Phang et al.,(2015). Preliminary Study of Seaweed Drying under A Shade and in A Natural Draft Solar Dryer, International Journal of Science and Engineering, 8(1),10-14. Doi: 10.12777/ijse.8.1.10-14] I. INTRODUCTION Department of Fisheries (DOF) in Malaysia aims to alleviate the poverty of coastal area population by transforming the seaweed farming industry from a cottage industry to become a commercial scale industry with a high yield production. The total production of seaweed production is expected to achieve 150,000 metric tonnes which worth RM1.45 billion in 2010 (Economic Transformation Programme, 2013). In order to export the dried raw seaweed to overseas buyers, post-harvest processing to dry fresh seaweed is an essential technique for shipping. The common post-harvest drying method that applied in Semporna is the open sun drying method. The harvested raw seaweed was spread on platform and exposed to sun or hang with rope as shown in Figure 1. The open sun drying method is favorable and performed from generations to generations where proper training in monitoring and operation on advance control panel is not required (Mercer, 2008). The open sun drying method is discouraged for large production due to the larger area is required and it is labour intensive. Product losses or contamination is increased particularly during raining seasons due to humidity reabsorption or remoistening. Figure 1. Seaweed Drying Method at Coastal Area Although an electrically powered convective solar dryer has been designed and tested in Semporna for seaweed drying (Fudholi et al., 2011), the farmers may not able to afford the high construction cost and electrical cost of the device. Consequently, seaweed drying is proposed to be carried out in a natural draft solar dryer and under a shade to investigate the seaweed drying behaviour. 10 © IJSE – ISSN: 2086-5023, 15th January, 2015, All rights reserved Internat. J. Sci. Eng., Vol. 8(1)2015:10-14, January 2015, Hooi-Kim Phang et al. The natural draft solar dryer consists of air opening at the bottom, drying chamber with trays and a draft enhancing chimney fitted with wire mesh at the top. The chimney with wire mesh can prevent cold inflow and has as high as 90% improvement on the efficiency of air velocity if compared to conventional chimney (Chu et al., 2012).This study aims to enhance the drying rate of seaweed through the enhancement of flow with natural convection as well as without fossil fuel and electrical devices. Table 1. Drying models tested for seaweed drying Model Equation Linear MR = -ax + b Lewis MR = exp (-kt) Henderson and Pabis MR = a exp (-kt) The moisture ratio (MR) is difined as the following equation: II. MATERIAL AND METHOD Fresh seaweed was packed into polystyrene boxes in Semporna, Sabah and then shipped from Tawau to Kota Kinabalu. The fresh seaweed was washed and packed into polyethylene (PE) bags before being placed on the cement floor in an open area for one day for dewatering. This dewatering was named as sauna process in mini-estate seaweed farming in Semporna proposed by Universiti Malaysia Sabah. The dehydrated seaweed from PE bag was weighed and then introduced into a room under shade and in a natural draft solar dryer.The seaweed was dried under a naturally ventilated room and a natural draft solar dryer with trays. The air temperature and relative humidity inside the solar dryer and surrounding were recorded using a data logger (Testo 174H, USA) every 10 minutes. The moisture content of seaweed was determined by a representative sample on each tray at top, middle and bottom every 3 hours from 8 am to 5 pm daily is shown in Figure 2. ‫= ܴܯ‬ (1) where MR is the dimensionless moisture ratio, ‫ܯ‬௜ is the moisture content at time i, ‫ܯ‬଴ and ‫ܯ‬௘ are the initial and equilibrium moisture content respectively on dry basis. In order to select a suitable drying model to describe the drying process of seaweed, the non-linear regression was implemented using the least square method for the drying models using Excel 2010. The determination coefficient (R2) and root mean square error (RMSE) were used as statisticalanalysis to observe how satisfactory is the model to describe the seaweed drying in the solar drying and shade drying. ܴଶ = ௌௌோ ௌௌ் =1− ௌௌா (2) ௌௌ் where SSE is the sum of squared error, SSR is the sum of squared residuals and SST is the sum of squared total which explained the proportion of variance accounted for the dependent variable by the model. ଵ RMSE = ൤ ෍ Representative sample ெ೔ ିெ೐ ெబ ିெ೐ ே ே ௜ୀଵ భ ଶ మ ൫‫ܴܯ‬௣௥௘,௜ − ‫ܴܯ‬௘௫௣ ൯ ൨ (3) where ‫ܴܯ‬௣௥௘,௜ is predicted moisture ratio and ‫ܴܯ‬௘௫௣ is the experimental moisture ratio. III. RESULT AND DISCUSSION Figure 2. Representative sample from the plot of tray The final moisture content of seaweed was determined where the difference of seaweed weight less than 5% for the subsequent measurement. The representative sample of seaweed from top, middle a (...truncated)