Solar drying of Andrographis paniculata using a parabolicshaped solar tunnel dryer Academic research paper on "Agriculture, forestry, and fisheries"

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Procedía Engi neering 32 (2012) 839 - 846

Procedía Engineering

www.elsevier.com/Iocate/procedia

I-SEECn011

Solar drying of Andrographis paniculata using a parabolic-

shaped solar tunnel dryer

N. Srisittipokakunab*, K. Kirdsiriab, J. Kaewkhaoabc

aCenter of Excellence in Glass Technology and Materials Science (CEGM), Faculty of Science and Technology, Nakhon Pathom Rajabhat University, Nakhon Pathom, 73000, Thailand bScience Program, Faculty of Science and Technology, Nakhon Pathom Rajabhat University, Nakhon Pathom, 73000, Thailand cThailand Center of Excellence in Physics, CHE, Ministry of Education, Bangkok 10400, Thailand

Elsevier use only: Received xx xx xxxx; Revised: xx xx xxxx; Accepted:xx xx xxxx

Abstract

Solar drying experiments of Andrographis paniculata were conducted in Nakhon Pathom, Thailand. For this purpose, a new type parabolic-shaped solar tunnel dryer was designed and manufactured. Solar dryer consisted of a flat-plate solar collector and a drying tunnel. The collector and the drying tunnel were covered with polycarbonate plates to reduce heat losses and placed in series. Heated air in solar air collector was forced through Andrographis paniculata by DC-fans driven by 15 W solar cell modules. The total area of the collector was 108 m2. During the drying period, drying air temperature, relative humidity, air flow rates, solar radiation, and lose of mass were measured at different parts of the dryer for every 10 minutes. To investigate its performance, the dryer was used to dry 100 kg of Andrographis paniculata. The dryer could be used for Andrographis paniculata of 75% (wb) moisture content, and they could be dried within 2-3 days, with 7% (wb) remaining moister. The products being dried in the dryer got the heat from both the sunlight and the collectors. They were completely protected from rain, animals, insects and the dried products are of high quality. However, the temperature of the drying air was varied between 35 - 75 oC, depends on the weather conditions.

© 2010 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of I-SEEC2011

Keywords: Tunnel dryer; Solar drying; Andrographis paniculata; parabolic-shaped

* Corresponding author. Tel.: +6-684-700-0851; fax: +6-634-261-005. E-mail address: nattapon_g@hotmail.com.

1877-7058 © 2012 Published by Elsevier Ltd. doi:10.1016/j.proeng.2012.02.021

1. Introduction

Thailand is an agricultural country, and its products range from world famous jasmine rice to various vegetables, fruits and herbs. Most of the products need some kind of preservation to enhance their shelf life since the production usually exceeds market demand at the harvest season. Drying is one of the most used methods for product preservation, and as a result, it adds higher value to the products. A dryer can achieve this purpose by supplying more heat which in turn increases the vapor pressure of the moisture in the product, reduces relative humidity of the air, then increases its moisture loading capacity and ensures sufficiently low equilibrium moisture content. Solar energy can be used as an important and environmental compatible source of renewable energy. The use of solar energy for drying effectively reduces the problems arising from generating energy by convention method. This is because the use of the conventional energy source for drying purposes is costly and hazardous to environment. Solar drying system may be classified into direct, indirect and mixed modes. In direct solar dryers, the air heater contains the product and solar energy passes through a transparent cover and is absorbed by the product. Essentially, the heat required for drying is provided by radiation to the upper layers and then conducted to the product bed. In indirect drying system, solar energy is collected in separate equipment, called solar air heater, and the heated air then passes through the product bed [1].

Andrographis paniculata is an annual plant with characteristic white-purple or spotted purple flowers that flourishes in South-East Asia, China and India. It has been valued for centuries by herbalists as a treatment for upper respiratory infections, fever, sore throat and herpes. Other reported applications include its use in cases of malaria, dysentery and even snakebites. Now, important new research has confirmed a host of pharmacological benefits for this herb, including potent anti-inflammatory, antibacterial and anti-viral effects. In addition, scientists have discovered that Andrographis paniculata helps boost the immune system, protects against cancer, prevents blood clots and maintains efficient digestive functioning [2]. The purpose of this paper is to present the developments and potentials of solar drying technologies for drying Andrographis paniculata.

1.1. Design /f S/lcr Dryer

To carry out design calculation and size of the tunnel dryer. The mass of water to be removed during drying, Mw kg [3];

where mw is mass of water to evaporation, (kg), mt is mass of the dried product, (kg), Mt is initial moisture of product, (%, wb) and Mf is final moisture of product, (%, wb), then calculate the amount of heat required from the equation [3];

when Qdrying is amount of heat required, (MJ) and L is heat required to evaporate water 1 kg, (MJ/kg). In the final step, calculated area of collector from the equation [3];

mw = (Mi - Mf)/(100 - Mf) x mt

A = Qdrying /( n x Ht x Nd)

where A is total area of collector, (m2), n is efficiency of collector, (decimal), HT is intensity of solar radiation on the ground, (MJ/m2- day) and ND is number of days required for drying

1.2 Characteristics of the dryer

The solar tunnel dryer, is 12.20 meter long and 1.22 meter wide. The solar tunnel dryer consists of a solar collector, drying tunnel, and three radial flow fans to drive the moist air out of the drier. The product to be dried is placed as a single layer inside the drying tunnel. Air entering the solar collector is heated and is forced on the products placed in the drying tunnel using three fans at the air inlet of the solar collector. For experiments with DC power from solar PV panels could be used. Metal plates are curved to be S-shaped and used as side walls. Moreover, top of the dryer is covered by transparent materials. The characteristics of the solar dryer as shown in Fig. 1, 2.

Polycarbonate Polycarbonate

Fig. 1. The characteristics of solar dryer (a) The solar collector and (b) the product container

Fig. 2. Illustration of solar dryer.

2. Performance of the dryer

To investigate the performance of the dryer, the full-scale experiments of dryer have been conducted on 100 kg of Andrographis paniculata. The instruments and method which used during the experiment are following.

2.1 Instruments and devices

To measure the solar radiation and another parameters that effect on the performance of dryer, different devices were employed. A pyranometer (Kipp & Zonen model CM 11, accuracy ± 0.50%) was placed on the top of dryer to measure solar radiation. Relative humidity from ambient and in any parts of dryer were employed, used hygrometer (Electronik, model EE23, accuracy ± 2%). Temperatures in the collectors, product container, air duct and ambient were measured by Thermocouple Type K (accuracy ± 0.1°C). Moreover, the air speed in the dryer also measured by anemometers (Airflow, model TA5, accuracy ± 2%) [4]. All voltage data from pyranometer, hygrometer and Thermocouple Type K devices were recorded by data logger (Yokogawa, model DC100) every ten minutes. For air speed was manually monitored at 3-hour intervals during the experiment. The performance of the drier was evaluated by conducting tests at by loading with pandanus tectorius, by measuring the following parameters: (a) radiation incident on the collector (ID), (b) air temperatures at various locations in the collector (Ti-Ti2) and dryer, (c) relative humidity (Hi-H3) and weight of samples. To measure the temperature of air at various locations of the collector and dryer, K-type thermocouples were installed at various points along the length and breadth of the solar tunnel dryer, as shown in Fig. 3. All temperature data were registered at an interval of ten minutes by a data logger. Drying test was started at 8:00 hours and stopped at 17:00 hours. Moreover, the sample products were also prepared and placed on product container parts (Exi -Ex8) and outside (Exout). Every 3-hour intervals, the samples were brought to weight until the end of process and they were taken in an oven to bake at 103C for 24 hours to determine the moisture content of the products. The relative humidity of air inside the dryer was determined from the dry bulb and wet bulb temperatures recorded by a data logger.

In, I' V

T Ex, T E.x3 T6. EX5 T8 Ex7 t H . 7 10' 2 »

Ti' H1 T3* E.x2 T5. E.X4 T7. Ex6 T9_ Ex8 T,i' H3>

Fig. 3. Position of thermocouples in the solar tunnel dryer

2.2 Materials

Andrographis paniculata has been used for centuries in China, India, and Thailand to successfully treat upper respiratory tract infection, fever, sore throat, herpes, and an array of other infectious and chronic diseases. Therefore Andrographis paniculata is chosen to investigate the performance and then compare data with natural sun drying. The performance tests were carried out two times during June, 2011 and weight 100 kg of Andrographis paniculata were used for each test. In the morning, cut Andrographis paniculata were manually loaded into the product containers to be dried and the fans were started at the

same times, from 8 a.m. and stopped at 5 p.m. All process was repeated in order to dry Andrographis paniculata until the final moisture was reached 8% (wb).

Moreover, the sample products were also prepared and placed on any parts of the dryer and outside. Every 3-hour intervals, the samples were brought to weight until the end of process and they were taken in an oven to bake at 105C for 24 hours to determine the moisture content of the products.

3. Results and Discussion

The two experiments were carried out during the 19th-20th June, 2011. In each experiment, Andrographis paniculata weight 100 kg was used for drying and the weather was clear sky day and windswept with the maximum global radiation of 1,050 W/m2 (Fig. 4).

8:00 11:00 14:00 17:00 8:00 11:00 14:00 17:00

Fig. 4. Variations of global solar radiation during the experiment

At the middle of the dryer, the drying air temperatures at the top and the bottom of the tray were found to varied in the range of 35 - 75 oC during 9:00 a.m.-5:00 p.m. Temperature from the top (T6) and bottom (T7) of solar collector were compared with ambient temperature (Ta) and shown in Fig. 5.

8:00 11:00 14:00 17:00 8:00 11:00 14:00 17:00

Fig. 5. Variations of the ambient temperature (Ta) and temperature of the outlet air at top (T6) and bottom (T7) dryer

As the fans were powered by a solar cell module, the air flow varied with solar radiation. This flow rate help to control the drying air temperature in the dryer. Electrical current and voltage that produced from solar panel were also considered, From Fig. 6 and Fig. 7 were found that the variations of these values depend on the solar radiation.

8:00 11:00 14:00 17:00 8:00 11:00 14:00 17:00

Fig. 6. Variations of the electrical current from solar panel

17:00 8:00 Time

Fig. 7. Variations of the voltage from solar panel

The relative humidity values at 10 a.m-4 p.m. were quite low, but they got increasing in the evening. This is not as seen with Fig. 8 because the humidity is the highest in the morning.

90. 80. 70. f 60.

Ь 50. &

J 30. №

20. 10. 0.

0 0 0 0 0 0 0 0 0 0 8:00

19 June 2011

Ambient

-л-1-1-1-1-1-1-1-1——I-1-1-1-1-1-1-1-1-1—

11:00 14:00 17:00 8:00 11:00 14:00 17:00

Fig. 8. Variations of the relative humidity of the ambient air and the air at top and bottom dryer

The drying rate of Andrographis paniculata in the dryer is significantly higher than that of the natural sun dryer. The variations of moisture of Andrographis paniculata was shown in Fig. 9. After two days of drying, the remaining weight of Andrographis paniculata was about 25 kg. The quality of dried Andrographis paniculata in terms of color, texture and taste is as good as high quality dried Andrographis paniculata in markets.

oooooooiooo poooooo.ooo ^ CN en ^»n^b ^¡00 c^o

o o o o o o o p o o o o o o ^ ^t h

Fig. 9. Comparison of the moisture changes inside solar tunnel dryer (Si - S8) and open sun drying (Sout) during drying of Andrographis paniculata

4. Conclusion

The performance of a collector solar tunnel dryer for drying Andrographis paniculata has been investigated in June. Two experiments were carried out 100 kg of Andrographis paniculata can be dried in 2 days. It was found that its performance is better than natural sun drying. The dryer could be used for Andrographis paniculata of 75% (wb) moisture content, and they could be dried within 2 days, with 7% (wb) remaining moister. Temperatures in the drying chamber varied from 35° C to 75° C. The problem of losses due to a contamination by insect and animal and rewetting by rain was overcome. The dried products of high quality were obtained.

Acknowledgements

N. Srisittipokakun, J. Kaewkhao and K. Kirdsiri special thanks to National Research Council of Thailand (NRCT) for funding this research.

[1] Moradi M, Zomorodian A. Thin Layer Solar Drying of Cuminum Cyminum Grainsby Means of Solar Cabinet Dryer. Americcn-Eurcsicn J. Agric. & Envir/n. Sci. 2009; 5(3): 409-413.

[2] Jarukamjorn K, Nemoto N. Pharmacological Aspects of Andrographis paniculata on Health and Its Major Diterpenoid Constituent Andrographolide. JHeclth Science 2008; 54(4): 370-381.

[3] Bolaji BO, Analysis of Moisture Transport in the Solar Drying of Food Items. The Pacific J Science end Techn/l/gy 2008; 9(2): 640-646.

[4] Janjai, S, Srisittipokakun, N. Experimental and modelling performances of a roof-integrated solar drying system for drying herbs and spices. Energy 2008; 33: 91-103.

References