Research Article. 148 P a g e. Journal of Applied Sciences & Environmental Sustainability 2 (5) , 2016 e-issn ARTICLE INFO

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1 Research Article Thermal Insulation Boards from Camel s Foot (Piliostigma Thonningii L.) Leave Fibres for Lagging Application A. Musa 1, A. Raji 2 and M.A. Hassan *2 National Space Research and Development Agency, Abuja 1, Department of Mechanical Engineering, Modibbo Adama University of Technology, Yola 2 ARTICLE INFO Article history Received: 12/10/2016 Accepted: 02/12/2016 Camel s foot, insulation boards, lagging applications, leave fibres, specific heat, thermal conductivity. A b s t r a c t There has been a growing enthusiasm for renewable and biodegradable thermal insulation materials motivated by the need for energy conservation, global warming and environmental impact of the waste product after their useful life. The synthetic thermal insulation materials currently in use have some negative effects on human health and environment; which necessitated a search for alternative materials from plants and agro-fibres. The potentials of Camel s foot (Piliostigma thonningii L.), a leguminous plant growing abundantly as a wild uncultivated plant resource in many parts of Nigeria was investigated. The leave fibres of the plant were prepared in form of insulation boards of thickness of 10, 20, and 50mm using natural rubber latex as a binder. The ratio of the fibres to the binder in the composition was 1:1, 1:2, 1:3 and 1:4. To determine the suitability of the boards, density, water absorption, thermal conductivity, specific heat and thermal diffusivity were studied. The results of analysis of variance (ANOVA) show that both the composition and thickness level have significant effect on the density which was found to increases as the binder part in the composition increases and it ranges between 388.5kg/m3 and 608.7kg/m3 over thickness level of 10-50mm. The percentage water absorption of the boards differs significantly as binder is increased in the composition with the values ranging between and 6.02%. The thermal conductivity values are between W/mK while the specific heat capacity values are between J/kg.K and J/kg.K. The ANOVA of the thermal conductivity suggest that there is insignificant difference between the boards as binder is increased in the composition while the thickness affected the thermal conductivity significantly. It was concluded that the Piliostigma thonningii fibre boards offer a great potential for use as thermal insulation products having recorded thermal conductivity that is comparable to that of the commercially available products and published research data on biodegradable thermal insulation from plants and Agricultural by-products. Journal of Applied Sciences & Environmental Sustainability. All rights reserved. 148 P a g e

2 1. Introduction In recent time, there has been high increase in the locally fabricated refrigerators, ice-making machines, cold storage rooms and ice coolers as a means of getting cold drinks and beverages and for the storage of perishable food items such as fish, meat, fruits and vegetables for commercial purposes. In the fabrication of these refrigerators and cold storage rooms, large quantities of thermal insulation materials are required. The use of the thermal insulation materials is regarded as one of the effective means of energy conservation. Thus, thermal insulation materials play an important role in achieving energy efficiency resulting in decrease in the cost of cooling/heating as well as decrease in the environmental pollution (Bhatia, 2011; Tangjuank, 2011). In Nigeria, the electricity sector is currently experiencing a serious crisis. With a population of over 140 million, the country generates only about 5000MW which is grossly inadequate to keep up with the demand (United Nations Development Program {UNDP}, 2010). The epileptic supply of electricity has forced Nigerians to locally fabricate refrigerators and cold storage rooms for commercial use. But the operators of these systems rely on diesel and petrol generators as the primary or back-up source of electricity to power them which is not only expensive but a source of environmental pollution. Moreover, substantial amount of the energy generated is wasted in these systems because they are either un-insulated or under-insulated. Manohar (2013) highlighted that in the low temperature insulation technology, low cost foam and polystyrene are the most extensively used. He noted that continuous research has perfected the manufacture and utilization of these materials for specialized applications which covers clothing, industrial and residential buildings, refrigerators and ice-coolers. Hence, Ugwu and Ogbonnaya (2012) also proposed to use the same materials in the design and adaptation of cold storage room for Umudike community and environs. But the use of these conventional insulation materials have some disadvantages due to the fact that they are expensive and may have a negative effect on human health and causes environmental pollution due to non-decomposition abilities after their useful life cycles (Tangjuank and Kumfu, 2011). According to Berge and Johansson (2012), thermal insulation materials such as polyurethane (PUR) foam are filled with ozone depleting chlorofluorocarbon (CFC-11) which demanded research on how to replace them in thermal insulation. For these reasons, there is need to develop alternative insulation materials for these refrigerators and cold rooms that will require less energy to produce, inexpensive and environmentally friendly.the application of 149 P a g e

3 natural fibres has drawn much attention in different engineering fields due to environmental concerns and the need to conserve energy. The use of natural fibres as insulation materials provides optimistic environmental profits with regard to ultimate disposability and better use of raw materials (Raju et al, 2012).Thus, a renewable thermal insulation materials from the locally available natural resources (plants) will significantly reduce the cost of construction of our locally fabricated refrigerators and cold rooms, as well as enhancing their energy efficiency thereby minimizing the environmental pollution resulting from the use of diesel and petrol generators. Panyakaew and Fotios (2008) opined that in addition to the health and environmental benefit, the renewable fibrous thermal insulation materials from plants and agricultural byproducts will generate economic development for farming and rural areas. However, there have been very few studies on the use of uncultivated plants as insulating materials. Therefore, this study investigates the potentials of Camel s foot (Piliostigma thonningii L.), commonly called Kargo in Hausa, which is one of the lignocellulose fibrous plants growing abundantly as a wild uncultivated tree in many parts of Nigeria such as Zaria, Bauchi, Ilorin, Plateau, Lagos and Abeokuta (Madara et al, 2010). The investigation of the thermal insulation properties of this plant is aimed at developing an insulation boards for lagging of cold storage rooms and locally fabricated refrigerators. Manohar (2013) investigated the thermal insulating ability of natural unprocessed coconut fiber by comparative method using three (3) laboratory built ice coolers with coconut fiber insulation and compared with two (2) commercially available coolers; Rubbermaid with foam insulation and polystyrene ice cooler. The results indicated that the coconut fiber ice coolers performed consistently better than the Rubbermaid cooler with foam insulation and the performance is comparable to that of the polystyrene ice cooler. The thermal insulation properties of pineapple leaves were investigated by Tangjuank (2011) in boards form. The thermal conductivity was found to be between and W/mK. He concluded that the thermal insulation boards produced from the pineapple leaves fiber exhibited a considerably good thermal insulation. Tangjuank and Kumfu (2011) also investigated thermal and physical properties of particle board from Papyrus leaves fibres (Typha angustifolial.) as thermal insulation. The boards thermal conductivities obtained are between and W/mK which is lower than that of the commercial insulation materials except polyurethane. Panyakaew and Fotios (2008) investigated the potentials of using agricultural waste materials as thermal insulation focusing on six (6) agricultural wastes; rice hulls, coconut husk, bagasse, corn cob, durian peel and oil palm leaves. They concluded that rice hulls, bagasse and 150 P a g e

4 coconut husk offer greatest potentials for manufacturing into thermal insulation products as their properties can be compared with that of the conventional insulation materials. The thermal conductivity of the oil palm fibre as investigated by Manohar (2012) ranged between W/mK to W/mK which is a good thermal insulator. Marian (2010) investigated the thermal conductivity of straw, the result was found to be between and 0.061W/mK. Paiva et al. (2012) carried out a parametric thermal insulation study of the corn cob particles board in which the impact of its thickness on its thermal insulation performance was investigated and the thermal conductivity value of 0.101W/moC was recorded. Kozlowski et al. (2008) developed flexible, nonwoven environmental friendly thermal insulation composite as filling material and as a facing for housing and transport using hemp fibre, flax fibre and wool. The developed nonwoven composite has excellent insulation performance due to the optimal thermal conductivity value of 0.043W/mK.Luamkanchanaphan, Chotikaprakhan and Jarusombati (2012) studied the physical, mechanical and thermal properties of insulation boards from Narrow-leaved Cattail fibres. The results show that the boards have good physical and mechanical properties with thermal conductivity values ranging between and W/mK which indicate excellent insulating ability for energy savings and are environmentally friendly. 2. Methodology 2.1 Materials The major raw material for this work is the leaves of Camel s foot (Piliostigma thonningii L.) which were collected from Girei Local Government Area of Adamawa State, Nigeria. Other materials include sodium hydroxide (NaOH), distilled Water and Pre-treated natural rubber latex all of analytical grade obtained from Northern Scientific chemicals shop in Yola, Nigeria. 2.2 Materials Preparation and Moulding The major raw material, that is the leaves of Camel s foot (Piliostigma thonningii L.) were mercerized using 5%w/v Sodium Hydroxide (NaOH) solution at room temperature for 24 hours to soften the fibres. The fibres were thoroughly rinsed in a fresh tap water and air dried. The dried samples were ground into small particle sizes using a commercial grinder. Five (5) rectangular wooden moulds or forming boxes of sizes 200mm by 200mm were constructed with different thicknesses of 10, 20, 30, 40 and 50mm. A required quantity of the fibreand the binder was charged into a rotating mixer and continuously mixed until the particles were thoroughly impregnated with the resin and the mixture was then poured into the mould. 151 P a g e

5 A force of 0.25kN was applied to ensure even settling of the product and was allowed to cure under the sun. Four (4) types of boards were produced from each mould with particles to binder ratios of 1:1, 1:2, 1:3 and 1:4. After forming, the board were then cut into various test samples. 2.3 Test To determine the suitability of the particleboards for insulation, the thermal properties are of prime importance. But other physicaland thermo physical properties are also significant. Hence, the following tests were conducted on the particle boards Density The densities of the boards were determined in accordance with the American Society for Testing and Materials (ASTM) C (Standard test method for dimensions and density of preformed block and board type thermal insulation) (ASTM, 2004). From each of the boards prepared, four (4) specimens of 60mm x 60mm were cut. The thickness, length and the width were measured in three (3) different locations, generally near the four corners of each specimen and the average of each was determined and recorded. The volume of each specimen was calculated using equation 1. Volume (m 3 ) = length (mm) x width (mm) x thickness (mm) x 10-9 (1) Each specimen was weighed using a digital weighing balance and the mass recorded. The density of each specimen was then calculated using equation 2 (2) Water Absorption The water absorption test was conducted according to ASTM D1037 (water absorption test method A) (ASTM, 2004). The specimens used in the determination of the density were used since their masses and volumes were recorded.the water absorption was expressed as the percentage increase in volume based on the volume before submersion. The specific gravity of the water was assumed to be 1.0 for this purpose Thermal Conductivity The thermal conductivity of the boards was determined in accordance with ASTM C (Standard Test Method for Steady State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus) (ASTM, 2004).The equipment used for the test was Armfield HT10XC Heat Transfer Service Unit and HT11C Computer Compatible Linear Heat Conduction Accessory. From each of the boards, four (4) specimens were cut in form of a disc of diameter (d) 25±1mm and the thickness (Δx) was measured and 152 P a g e

6 recorded. A specimen was clamped tightly in between two faces of heated and cooled brass sections, the heater voltage (V) was set to 10 volts and the heater current (I) was read from the console and recorded. After HT11C was stabilised, the temperatures T 1, T 2, T 3, T 6, T 7 and T 8 were also read and recorded from the console display. Where T 1, T 2 and T 3 are the thermocouples connected to the heating section of the instrument and T 6, T 7 andt 8 are those connected to the cold section of the instrument. For each set of readings, the derived results were tabulated under the following headings; heat flow Q = IV, cross sectional area /4, temperature of hot face (T hot)and cold face (T cold). Where (3) (4) The temperature difference across the specimen was determined as The thermal conductivity (k) of the specimen was calculated using Fourier rate equation as (6) (5) Specific Heat The specific heat test was conducted according to ASTM C351-92b (Standard test method for mean specific heat of thermal insulation) (ASTM, 2004) Thermal Diffusivity The thermal diffusivity of the material was calculated using equation 7 (Cengel, 2008) as shown (7) Where; are the thermal conductivity, density and the specific heat of the material respectively as obtained from the experiments on thermal conductivity, density and specific heat. 3.0 Results and Discussions 3.1 Density Figure 1 present the average densities of the boards. It reveals that the densities at fibre to binder ratio of 1:1 is between 388.5kg/m 3 and kg/m 3 over thickness range of 10-50mm, for 1:2, the density is between 528.1kg/m 3 and 572.9kg/m 3 and for 1:3, it is from 534.4kg/m 3 to 591.8kg/m 3 while for 1:4, the density is between 538.4kg/m 3 and 608.7kg/m 3 over the thickness range of 10-50mm. It is observed that the 153 P a g e

7 board s densities increase as the part of the binder in the ratio of the binder to the fibre increases in the composition. This may be as result of increase in fluidity of the binder which flows to close the air pores between the fibres on the surfaces of the board, in addition to the fact that lignocellulose fibres have lower densities compared to polymeric materials; therefore, increasing the binder in the composition will reflect increase in density which is in agreement with the studies of Tangjuank and Kumfu (2011).The results of the analysis of variance for leaves fibre boards at 95% confidence level show that the composition (fibre to binder ratio) as well as the thickness has significant effect on the boards densities. Figure 1: Relationship of density and Composition at different thickness levels 3.2 Percentage Water Absorption The results of average water absorption of the boards at fibre to binder ratio of 1:1, 1:2, 1:3 and 1:4 are presented in figure 2. The results indicate that at fibre to binder ratio of 1:1, the water absorption is between and 15.25% over the thickness range of 10-50mm. At 1:2, it is between and 11.63%, and at 1:3, it is between and 9.26% while for 1:4 average water absorption of to 6.02% was obtained over the same thickness range of 10-50mm.The results of analysis of variance for percentage water absorption show that there is significant difference in percentage water absorption of the boards as binder ratio in the composition increases. But on the other hand, the result shows that the thickness has no significant effects on the percentage water absorption. 154 P a g e

8 Figure 2: Percentage water absorption at different compositions From the figure, it can be seen that the percentage water absorption decreases as the binder to fibre ratio increases. Thus, it can be deduced from the figures 1 and 2 that the percentage water absorption is inversely proportional to the density. This is because the lower density boards have higher voids and pores as a result absorbed more moisture. In addition, natural fibres derived from lignocellulose are hydrophilic in nature which contain strongly polarized group, thus, increasing the quantity of the fibre in a composition increases the percentage of water absorption (Rakeshet al, 2011). 3.3 Thermal Conductivity Figures 3 present the results of thermal conductivity of the boards at various compositions. The thermal conductivity values at 1:1 vary between W/mK and W/mK over a thickness range of 10-50mm. At 1:2, the values are between and W/mK, and for 1:3 it is between and W/mK while at 1:4 the values ranges from to W/mK. Hence, the lowest thermal conductivity value occurs at 1:4; 10mm while the highest thermal conductivity occurs at 1:2; 50mm. 155 P a g e

9 Figure 3: Comparison of thermal conductivity at different composition The results of the analysis of variance for thermal conductivity show that there is no significant relationship between the composition and thermal conductivity of the boards. While on the other hand, the change in thickness has a significant effect on the thermal conductivity 3.4 Specific heat Figure 4 presents the results of specific heat of the boards at different fibre to binder ratios. The results show that the boards have specific heat values of J/kg.K to J/kg.K as the composition of fibre to binder ratio increases from 1:1 to 1:4. The results of analysis of variance for the leaves fibre boards show that the binder ratio in the composition has a significant effect on the specific heat values of the boards. Figure 4:Specific heat versus Composition 156 P a g e

10 3.5 Thermal Diffusivity Figure 5 shows the thermal diffusivity values at fibre to binder ratio of 1:1, 1:2, 1:3 and 1:4. The thermal diffusivity values are between 2.03E-8m 2 /s and 8.07E-8m 2 /s. From the Figure, it can be observed that the thermal diffusivity decreases as portion of binder in the fibre to binder ratio increases. This signifies that the thermal diffusivity is inversely proportional to the density.the results of analysis of variance for thermal diffusivity show that there is significant difference in thermal diffusivity of the boards as the binder ratio in the composition increases. Figure 5:Comparison of Thermal diffusivity at different composition 4.0 Conclusion From the results obtained, it can be concluded that the Piliostigma thonningii fibre boards offer a great potential for use as thermal insulation products having recorded thermal conductivity values that are comparable to that of the commercially available products and published research data on biodegradable thermal insulation from plants and Agricultural by-products. REFERENCES American Society for Testing and Materials (ASTM) Standard (2004).ASTM international, 100 Barr Harbor Drive, West Conshohocken, United States. Retrieved from P a g e

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