Determination of Thermal Properties of Coriander Seeds Anditsvolatile Oil (Coriandrumsativum)

The effect of temperature and moisture content on the thermal properties such as thermal conductivity, specific heat andbulk thermal diffusivity was evaluated. The thermal conductivity was measured by the transient technique using a line heat source. The maximum slope method was used to analyse the line source heating data for thermal conductivity determination. The specific heat capacity was measured by different scanning calorimetry and ranged from 730 to 4014 J/kg k at 3 to 15% mc (w.b.). The thermal conductivity of coriander seeds ranged from 0.0406 to 0.0989 W /m k and increased with moisture content in the range of 8 to 16 % mc (w.b.). Thethermal diffusivity ranged from9.67823E-08to 1.68255E-07 m2/s at 8% mc (w.b.).such Thermal properties are useful in designing and fabrication of ambient and cryogenic grinding system for spices and other similar commodities. Introduction: Corianders seeds are dried when they are ripe .They have an aromatic odor and agreeable spicy test. The seed consist of moisture 11.2percent, protein 14.1percent, fat 16.1percent, minerals 4.4percent, fiber 32.6percent and carbohydrates 21.6percent per 100 grams. Their mineral and vitamin content are calcium, Iron, phosphorous, carotene, thiamine, riboflavin, niacin. Coriander juice is highly beneficial in deficiencies of Vitamin A, B1, B2, C and iron. Thermal conductivity, thermal diffusivity andspecific heat capacity are three important engineeringproperties of a material related to heat transfercharacteristics. These parameters are essential in studying heating, drying and cooling processes for coriander seeds,Measurement of the thermal conductivity of agricultural products of various types such as granular materials byK. K. DUA and T.P. OJHA(1969), Physical properties of coriander reported by YalcinCoskuner and ErsanKarababa (2006). Specific heatmeasurement method, differential scanning calorimetry (DSC) has been the most accurate and rapid method. Develop relationship between specific heat,temperature and moisture content ofborage seeds and described DSC by Yang et al. (2002), Most of the methods have been employed by researcher in determining the specific heat of food, seeds and agricultural materials by Mohsenin N N[5]. Thermal properties of cumin seed are determined by K.K. Singh and T.K. Goswami (2000).The objective of this study is to determine the thermalconductivity, specific heat capacity and thermal diffusivity of coriander seeds as a function of seed moisture content and temperature. 1. Materials and methods 1.1 Sample preparation Coriander seeds for analysis were obtained from a CIPHET. The seeds were conditioned to five different moisture contents ranging from 3 to15 w.b.For lower moisture content of the sample, the predetermined quantity of coriander seed was dried down to the desired moisture content. The calculated amount of distilledwater was added to achieve higher moisture content. The samples were dried in vacuum drying oven at 72C (recording mc at every 15 min interval) to achieve below 11.2 percent mc. Samples were stored in sealed, moisture free and water proof flexible polythene bags. The samples were kept at five oC in arefrigerator for one week to allow the moistureto uniformly distribute into the Coriander seeds. The moisture contents of the samples were determined using the HB43S Halogen Moisture Analyser. 1.2 Thermal conductivity measurement Thermal conductivity, k, is the property of a material's ability to conduct heat. Thermal conductivity is measured in watts per meter kelvin (W/(m·K)) or W·m·K.Thermal conductivity is primarily dependent on composition, but also on any factor that affects the heat flow paths such as porosity and shape, size and arrangement of void spaces, homogeneity, fibers and their orientation (Sweat 1986). The line source method is the most widely used transient-state method.The thermal conductivity was measured by using Quick Thermal Conductivity MeterKemtherm QTM-D3, (Kyoto Electronics, Manufacturing (KEM) Co.Ltd,Tokyo, Japan). In this uses a thermal conductivity probe as a heating source, and estimates the thermal conductivity based on the relationship between the sample core temperature and the heating time. In principle, the heat is generated in a hot wire at a rate q in W: Q = IR ...............(1) Vijay singh Sharanagat/ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 2, March -April 2013, pp.1767-1773 1768 | P a g e Where I is the electric current in A and R is the electric resistance in ohm/m. To make a measurement, the probe was put on the material of interest. From thermal equilibrium, the probe heater was energized and heated the medium with constant power. The temperature rise at the heat source was monitored. Following a brief transient period, the plot of the temperature versus the natural logarithm of time became linear. The slope was equal to Q/(4πk). The thermal conductivity could be calculated from the relation: k = Q(ln t2−t0 t1−t0 )/4π(T2 − T1).................(2) Where k = thermal conductivity of sample [W/m°C] Q = power dissipation by heater wire [W/m] t1 = time since probe heater was energized [s] t2 = time since probe heater was energized [s] t0 = time correction factor [s] T1 = temperature of probe thermocouple at time t1 [°C] T2 = temperature of probe thermocouple at time t2 [°C] The time correction factor t0 compensates for the finite size of the probe and for differences in properties between sample and probe material. Its value is calculated from the data. Equation (2) shows a linear relationship between (T2 – T1) and ln(t) with the slope s = Q/4πk. The slope S can be obtained from the experimental data of (T2-T1) versus ln(t) by linear regression, and the thermal conductivity can then be calculated from the linear slope S: