EFFECT OF HOLE SPACING AND NUMBER OF PIPE ON DRYER BOX TEMPERATURE

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 11, November 2017, pp , Article ID: IJMET_08_11_105 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed EFFECT OF HOLE SPACING AND NUMBER OF PIPE ON DRYER BOX TEMPERATURE I Gede Bawa Susana, I G. N. K. Yudhyadi, Ida Bagus Alit, Mirmanto and I D.K. Okariawan Department of Mechanical Engineering, Mataram University, Jl. Majapahit no. 62, Mataram, NTB, 83125, Indonesia ABSTRACT This research designed and tested dryers operated using rice husk waste as fuel, and based on heat exchange mechanism. Heat exchangers are placed at the bottom of the chaff pile and forced forcible air through the pipes. The heat exchanger receives heat from the chaff burning in the stove, and then releases the heat in the dryer box. The purpose of this research is to know the influence of hole distance and the number of heat exchanger pipe to drying box temperature. The dimensions of the stove are 500 x 500 x 800 mm, and the drying box is 500 x 500 x 600 mm. The result of this study is the time required to burn 20 kg of husk in the stove that is ranging from 720 to 785 minutes. The amount of dryer box temperature is greatly influenced by the temperature of the heat exchanger pipe. The highest drying box temperature is obtained at the stove with a 50 mm hole spacing, but the heat release time in the dryer box becomes shorter. The more heat exchanger pipe, the higher the temperature on the dryer box. Key words: Dryer, rice husk waste, stove and heat exchanger. Cite this Article: I Gede Bawa Susana, I G. N. K. Yudhyadi, Ida Bagus Alit, Mirmanto and I D.K. Okariawan, Effect of Hole Spacing and Number of Pipe on Dryer Box Temperature, International Journal of Mechanical Engineering and Technology 8(11), 2017, pp INTRODUCTION Drying is a way of removing the water content from a substance that is dried with the aid of natural and artificial heat, Sontakke [1]. The drying process is heat transfer as well as mass transfer in the form of water or moisture from the material to the surface. The energy used in the drying process can be derived from solar energy, electricity, and other fuels. Research on the use of dryers has been widely practiced, such as Moharaj and Candra [2]. They conducted research on the performance of the convection heat-drying solar dryers to dry the peppers. The systems made consist of flat plate solar collectors, centrifugal blowers and drying racks. The blower circulates air with an airflow rate of 0.25 kg/s. The use of dryer efficiency is 21%. Sushrut et al. [3] compared the conventional solar dryers and natural editor@iaeme.com

2 I Gede Bawa Susana, I G. N. K. Yudhyadi, Ida Bagus Alit, Mirmanto and I D.K. Okariawan convection dryers. The designed collector area was 2 m 2, and was used for drying chili and wine. The results showed that the solar dryers with forced convection heat transfer had better drying speed and quality than natural convection. The weakness of the solar dryer is that the drying process is highly dependent on the weather so that drying continuity cannot be maintained. Gunasekaran et al. [4] tested the performance of fluidized bed dryers. This system consists of blower, heater, and dryer rack. The design drum rack is 375mm x 740mm. They used the dryers to dry cassava and corn. The parameters observed were moisture content, air humidity, and drying time. The results show that the higher the drying temperature the shorter the drying time. To reduce the cassava water content from 74% to 11% at 60o drying temperature takes 150 minutes. Artificial dryers often require substantial costs, so artificial dryers become inefficient. The use of waste as an energy source can be one solution. Chaff waste, as a by-product of rice milling can be used as an energy source. In the process of rice milling, the resulting husk waste is as much as 22%, Ajay et al. [5]. Rice husk waste has a high calorific value of 13.9 MJ/kg or equivalent to half the calorific value of coal. Therefore, rice husk is very potential to be used as fuel, Haykiri-Acma [6]. Utilization of rice husk waste as fuel has been developed such as the use of rice husk waste as fuel of briquettes, Efomah and Gbabo [7]. The briquettes are 0.21 m tall, 0.08 m in diameter, 1.1 kg in weight, and 1.1 kg / m3 density. The briquettes are made of good quality because of high volatile matter values (68.2%) and low ash content (16.1%). Srinath [8] investigated the characteristics of rice husk combustion in rectangular fluidized bed combustors. Fluidized bed is operated with kg / h husk feed rate with excess air factor ranging from 20 to 100%. The results showed that the excess air factor of 25-70% had a significant effect on combustion efficiency, except the high excess air factor (> 80%). The highest combustion efficiency was obtained at 95%. Mirani et al [9], examined the use of waste-fueled rice husk gasifies to dry rice. The designed system consists of feeder chaff, combustion chamber, ash chamber, centrifugal fan and drying chamber. The average drying air temperature is 45 C. To reduce the water content of material from 24% to 14% required 3.33 hours with tool efficiency of 58%. However, all of the above dryers have a weakness. The weakness of the dryers is that they cannot be used to dry the fruits or processed food products, because the combustion gas can contaminate the food. To overcome this problem, a dry-fuel chamber exchanger is developed and presented in this current study. Actually, study on the drying box utilizing heat exchangers as the heat source has ever been conducted by Mirmanto et al. [10,11]. They used parallel and serpentine pipe heat exchanger. The hot water was flowed inside the heat exchanger, and then the heat came out from the heat exchanger and heated up the drying box. However, the problem encountered in their study was that the heat released by the heat exchanger was too small so that the efficiency of the drying box was very low. This study try to improve the similar method used by Mirmanto et al. [10,11]. However, in [10,11], the hot water flowing inside the heat exchanger was produced using an electrical power, while in this current study, the working fluid is air heated up using a heat exchanger placed under the combustion chamber, and the heat is gained from rice husk combustion. Based on the above literature survey, a similar study with this study does not yet exist. Therefore, using a heat exchanger as a heat source by utilizing rice husk waste is selected for examination and it indicates a new thing in drying method areas. The objective of this research is to get the effect of the distance of the stove hole and the number of heat exchanger pipes to the dryer temperature editor@iaeme.com

3 Effect of Hole Spacing and Number of Pipe on Dryer Box Temperature 2. EXPERIMENTAL SETUP This study is an experimental study, with a schematic diagram shown in Figure 1-3. The tested system consists of a chamber combustion stove, heat exchanger pipes, dryer box, and fan. The stove has a dimension of 500 x 500 x 800 mm. On the wall of the stove there are air circulation holes. The diameter of the airspace is 50 mm with the distance of the hole varied. The drying chamber has a dimension of 500 x 500 x 600 mm. The drying room wall is made of 6mm plywood and 6mm insulating rubber. Above the dryer box is installed fan to circulate the air in the dryer box. Heat exchanger pipes are made of steel pipe with a diameter of 25.4 mm. The pipes are placed at the bottom of the stove connected to the drying chamber. The air enters through the heat exchanger in the stove and receives heat from the chaff burning, then flows to the dryer box. Figure 1 Schematic diagram of the test facility Figure 2 Hole spacing variaton: (a) 50 mm, (b) 100 mm, (c) 150 mm editor@iaeme.com

4 I Gede Bawa Susana, I G. N. K. Yudhyadi, Ida Bagus Alit, Mirmanto and I D.K. Okariawan Figure 3 Number of heat exchanger pipe variations: (a) 5 pipes, (b) 7 pipes, (c) 9 pipes Put 20 kg of rice husk into the stove, then burn, and record all the temperatures in the heat exchanger pipe, dryer box, and ambient temperature. In addition, it noted a decrease in the surface height of rice husks in the stove per unit of time. In this study, the dryer box is conditioned without load with a fixed air velocity of 2 m/s. The hole distances on the stove wall and the number of heat exchanger pipes are varied to obtain the best dryer performance. 3. RESULTS AND DISCUSSIONS The first experiment was performed by varying the distance of the hole. Three stoves with hole spacing of 50 mm, 100 mm, and 150 mm, were tested using 9 heat exchanger pipes. The combustion air naturally enters through the air holes on the stove wall, while the dryer air enters from the heat exchanger pipe and exits the dryer box by force with the help of the fan placed above the dryer box. The air velocity out of the dryer box is set using a dimmer switch with a speed of 2 m / s. The results are shown in figures 4 through 6. As shown in Figure 4-6, the temperature of both heat exchanger and dryer box increases from 0 to of approximately 225 second, after that the temperature decreases with the time. At the time of more than 600 second the temperature seems to be constant. This indicates that the heating process for both heat exchanger and dryer box are in transient condition. When the fire in the combustion chamber is started, then all components of the test facility also start to be hot. This is indicated by the increase in the temperature. After the heat absorbed by the components gets a maximum value then the system tries to be in equilibrium so that the temperature decreases and tends to be constant at more than 600 second. Furthermore, In the first two hundred minutes, the temperature of the heat exchanger rises, as the combustion of the husk begins at the bottom of the stove just above the heat exchanger. As time progresses, the combustion process propagate upward until all the fuel has been burned. The further burning of chaff from heat exchanger the heat exchange temperature decreases. This phenomenon occurs for all stoves with different hole spacing. Figure 4 Temperature versus time observation for the stove with a hole spacing of 150 mm editor@iaeme.com

5 Effect of Hole Spacing and Number of Pipe on Dryer Box Temperature Figure 5 Temperature versus time observation for the stove with a hole spacing of 100 mm Figure 6 Temperature versus time observation for the stove with a hole spacing of 50 mm The amount of dryer box temperature is greatly influenced by the heat exchange temperature. The temperature of the heat exchanger itself is affected by the combustion process in the furnace. The burning of the husk in the furnace requires the supply of air coming from the hole on the furnace wall, so the hole spacing on the furnace affects the combustion process. The relation of time to the height of rice husk in the furnace is shown in Figure 7. Of the three furnaces tested, the furnace with a 50 mm pit spacing resulted in the quickest drop in the chaff's height. The shorter the distance between the holes the more air holes in the wall of the furnace, so the combustion air more easily get into the furnace. This causes the combustion process faster. The faster combustion process of rice husk leads to a decrease in the chaff's height faster as well. The decrease in husk from the start of burning to the 600th minute is quite rapid, but then slows down in the subsequent minutes; this is because the fuel of the husk is almost burned out. Figure 8 shows the time relation to drying box temperature at the variation of hole spacing. The time taken to burn 20 kg of rice husk in the furnace ranges from 720 to 785 minutes. The highest drying box temperature, obtained at the furnace using a 50 mm hole distance, but the hot release time in the dryer box becomes shorter. Subsequent research is to vary the number of pipes on heat exchangers. The numbers of the pipes used are 5, 7, and 9 pieces. The furnace used is a furnace with a distance of 50 mm hole with air flow velocity in the dryer box of 2 m/s. The highest temperature in the dryer box is generated on the furnace with heat exchanger consisting of 9 pipes, as shown in figure editor@iaeme.com

6 Dryer box temperature ( O C) Dryer box temperature ( O C) I Gede Bawa Susana, I G. N. K. Yudhyadi, Ida Bagus Alit, Mirmanto and I D.K. Okariawan The more pipes in the heat exchanger, the more heat transfer surfaces that occur in the furnace or in the dryer box. The greater the contact surface of the heat transfer in the furnace causes the greater the heating of rice husks to be absorbed by the heat exchanger. Increased heat energy absorbed in the furnace which further increases the heat released in the dryer box. Therefore, the temperature in the dryer box becomes higher Figure 7 Rice husk level versus observation time 50 mm 100 mm 150 mm Time (min) Figure 8 Dryer box temperature versus observation time pipes 7 pipes 9 pipes Time (min) Figure 9 Dryer box temperature versus observation time for the heat exchanger with pipe number variations editor@iaeme.com

7 Effect of Hole Spacing and Number of Pipe on Dryer Box Temperature 4. CONCLUSIONS The time taken to burn 20 kg of rice husk in the furnace ranges from 720 to 785 minutes. The amount of dryer box temperature is greatly influenced by the temperature of heat exchanger pipe. The highest temperature in the dryer box is obtained by using a furnace with 50 mm hole spacing. But the heat release time in the dryer box becomes the shortest. The shorter the distance of the hole, the process of burning rice husk will be faster, so the decrease of rice husk in the furnace is also faster. The more the number of pipes in the heat exchanger, the greater the heat from the burning of rice husks that can be absorbed by heat exchanger. The increased heat energy absorbed in the furnace further increases the heat dissipated in the dryer box, and the dryer box temperature becomes higher. REFERENCES [1] Sontakke, M.S. and Salve, S.P. Solar drying technologies: a review. Int. Refereed J. Engineering and Science, 4 (4), 2015, pp [2] Mohanraj, M. and Chandra, S. Performance of a force convection solar drier integrated with gravel as heat storage material for chili drying. J. Engineering Science and Technology, 4 (3), 2009, pp [3] Sushrut, S.H., Prajwal, S., Naveen, H., Karthik, H. and Siddharth, G. Experimental analysis of solar air dryer for agriculture products. Int. Research J. Engineering and Technology, 2 (3), 2015, pp [4] Gunasekaran, K., Shanmuugan, V. and Suresh, P. Modeling and analytical experimental study of hybrid dryer integrated with biomass dryer for drying coleus forskohlii stems. IACSIT Coimbatore Conferences, 28, 2012, pp [5] Ajay, K., Mohanta, K., Kumar, D. and Parkash, O. Properties and industrial applications of risk husk: a review. Int. J. Emerging Technology and Advanced Engineering, 2 (10), 2012, pp [6] Haykiri-Acma, H. and Yaman, S. Comparison of the combustion behaviors of agricultural wastes under dry air and oxygen. World Renewable Energy Congress, 2011, pp [7] Efomah, A.N. and A. Gbabo, The physical, proximate and ultimate analysis of risk husk briquettes produced from a vibratory block mould briquetting machine. Int. J. Innovative Science, Engineering and Technology, 2 (5), 2015, pp [8] Srinath, S., G.V., S. and Reddy. Combustion and emission characteristics of rice husk in a rectangular fluidized bed combustor. 2 Nd International Conference on Environmental Science and Technology, 6, 2011, pp [9] Mirani, A.A., Ahmad, M., Kalwar, S.A. and Ahmad, T.A. A rice husk gasifier for paddy drying. Science Technology and Development, 32 (2), 2013, pp [10] Mirmanto, M., Sulistyowati, E.D. and Okariawan, I K. D. Effect of radiator type on dryer room temperature distribution and heat transfer rate. JP J. Heat and Mass Transfer, 13 (4), [11] Mirmanto, Syahrul, Emmy Dyah Sulistyowati, I Dewa Ketut Okariawan and Rodian. Effect of inlet temperature and ventilation on heat transfer rate and water content removal of red chilis. J. Mechanic Science and Technology, 31 (3), [12] K Sampath Kumar, U M Praveen, A Prathyusha, V Akhila, P Sasidhar, A Comprehensive Study On Partial Replacement of Cement with Sugarcane Bagasse Ash, Rice Husk Ash & Stone Dust, International Journal of Civil Engineering and Technology, 7(3), 2016, pp [13] Satish Babu B. and Sunder Kumar P., A Report on Partial Substitute of Cement in Concrete using Rice Husk Ash. International Journal of Civil Engineering and Technology, 8(1), 2017, [14] Ch. Eka Sai Kumar and V. Raju, A Study on Replacement of Cement with Rice Husk Ash. International Journal of Civil Engineering and Technology, 8(1), 2017, editor@iaeme.com