Results The temperatures for heating and cooling the wood and resin blocks were plotted againsttime, as shown in the two figures below. In the two procedures, the time it takes for the materials to reach steady-state is inconclusive about their conductivity and diffusivity. In the heating procedure, the resin reaches steady-state much faster than that of the wood block. In the cooling procedure, however, the wooden block reached steady state a little faster compared to the resin block. The experimenters stopped taking-in temperature readings if no temperature change was observed after 20 data points. That is, if there were no temperature changes after 100 seconds. The cooling process took much more time compared to the heating process, despite the two graphs looking quite similar to each other. 65 60 55 Temperature (C) 50 45 40 35 30 25 20 0 500 1000 Time(s) 1500 Resin Heating Wood Heating Figure 1a. Temperature versus time plot for heating. 35 30 Temperature (°C) 25 20 15 10 5 0 0 1000 2000 Time (s) 3000 Resin Cooling Wood Cooling Figure 1b. Temperature versus time plot for cooling. The temperature decrease rate might have been very-very small such that a long time is required to actually reach thermal equilibrium.1 °C Time. and the Fourier Number or dimensionless time. Convection has been neglected for ease of calculation. as the calculated thermal diffusivities will be different from that of literature values.5 Cooling medium Resin Wood 1. These voids were filled with air. °C 60 58. a possible source of error was that the cube was not totally immersed in the cooling medium. Y.2 2. Calculations for thermal diffusivities will not directly use the temperature versus time plots. the ice bath or chamber had voids it. The quantities are defined in the equations below: . s 3485 3345 final temp. °C 2. steady-state has not been achieved at all. s Resin 1280 Wood 1555 final temp.Table 1. from the center of the cube to its surfaces. Meanwhile. with both surface and probe temperatures reaching 60°C. but two dimensionless quantities.6 The “final” values of temperature and time after steady-state has been achieved have been tabulated above. Convection has been neglected in the calculation procedures and will contribute to error. which was not in thermal equilibrium with the ice. Different temperature gradients are therefore present. In contact with air In contact with ice Figure 2. The cube surface which is in contact with two media. The expected temperature of the cube will be different from that of the temperature of the ice blocks. because of the presence of hot water and cool air as media. or rather. In the calculations for thermal diffusivity. Final Values for Heating and Cooling proccesses Heating medium 60°C Time. It should be noted that convection also takes place. The surfaces of the cubes were then in contact with two media. For the cooling of the cubes. which was ice. thermal equilibrium for the cooling of the blocks has not been achieved. Since the medium was of different small solids. Thermal equilibrium has been achieved in the heating of the blocks. which were of different temperatures. it was assumed that conduction was the dominant form of heat transfer. 5 -2 -2. The graphs below show the “linearized” plots Y versus Fo. α.0.5 -3 Fo y = -0. Figure 3. and will be compared to a similar plot.06456236 R² = 0.5 log Y -1 -1. called the Williamson-Adams Chart to solve for the diffusivity. Plotting the logarithm of Y versus the dimensionless number will give a linear plot. which is the ratio of the volume to the surface area.93285362 0 5000000 10000000 15000000 20000000 25000000 . The Williamson-Adams Chart.(1) (2) The actual lengths of the cubes were converted to a characteristic length.00000008x . Resin Heating 0.5 0 -0. 2 -0.2 -1.07156368 R² = 0.8 Fo 10000000 20000000 30000000 40000000 y = -0.6 -1.4 -1.0.99870383 Fo 0 20000000 40000000 60000000 80000000 Figure 4b. .8 -1 -1.Figure 4a.4 -1.8 -1 -1.4 -0.6 log Y -0.6 y = -0.98428994 Figure 4c. Y versus Fo plot for wood heating.00000005x .00000002x .2 -1. Y versus Fo plot for resin heating. Y versus Fo plot for resin cooling Wood Heating 0 -0.4 -0.6 log Y -0. Resin Cooling 0 -0.0.2 0 -0.01001831 R² = 0. Using a graphical method presents a significant amount of error since it does not only involve the uncertainties of the graphing instruments.99121E-08 Α.4 Fo 0 20000000 40000000 60000000 80000000 y = -0.13216E-07 -4.Wood Cooling 0 -0.93638E-08 -1. From the Williamson-Adams Chart: ( Using the experimental data: ( Dividing the two equations: ) ) The solution requires a graphical method. and was found to be -3. which is rise-over-run is taken from the semi-logarithmic chart. but also the experimenters’ judgment.4 log Y -0. Calculated Diffusivities based from slopes of graphs -3.88115E-08 α.01678701 R² = 0.99826706 Figure 4d.00000002x . m2/s 3. The slope. m2/s 5.6296E-09 5.38E-08 Cooling slope -2.201E-08 1.6 -0.2 -1.8 -1 -1.537. Y versus Fo plot for wood cooling. Since the two plots are similar to each other. since no digital version with values for the Williamson-Adams chart is available. a ratio of their respective slopes will give the thermal diffusivities of each material.537 Heating slope -1.63E-09 .0. W-A slope resin wood Table 2.2 -0. The %errors ranges from 47% to as much as 200%. the calculated diffusivities are very far from those of the expected values. The type of wood and resin was not specified in the experiment. A different actual hot bath temperature may be involved. then convection cannot be neglected. Adding cold water to the ice bath reduces the temperature gradient between the two media.1506049 5.42E-07 90. Vernier LabPro) and a much more efficient way of producing the said plots. Recommendations Using computer-connected thermocouples will help produce a more accurate temperature versus time graph (ie.2E-08 1. These very large errors may be attributed to calculation procedures.63E-09 1.3865 1.28150966 5.07E-08 199. The water used in the hot bath must be clean/distilled since impurities “obstruct” the sensor of the heating machine when scaling occurs. This may cause a certain degree of error since it was observed that majority of the top surface of the woodblock was covered with adhesive.Table 3. Experimental and Theoretical Values of Diffusivities heating α. and the data lacks as well. m2/s resin wood exptl theo %error exptl theo %error 3. great caution must be taken in specifying crucial parameters. Given that the diffusivities has now been calculated. While this method is probable way of determining diffusivities and conductivities.62964E-09 1. It will be helpful to specify what type of wood and from what plant the resin came from since the data obtained here will be of no use if one is to compare to literature values without exactly knowing the type of wood and resin used. thus allowing a more uniform temperature throughout the cooling medium.42E-07 96. If the substance has high conductivity.03546 Conclusion Based from the theoretical values given by the project proponents. or the selection of theoretical values for the materials involved.. The adhesive has different thermal properties from that of wood. This is beyond the scope of the experiment. The thermal conductivity is acquired by multiplying the diffusivity by the substance’s density and isobaric heat capacity. .38E-08 1. one can obtain the thermal conductivities of the materials. Liquid water has better thermal conductivity than air. It will also be helpful to determine what type of adhesive was used in sealing the probe in the wood block. Such knowledge of the conductivity will allow experimenters to judge whether convection plays a major role in heat transfer. m2/s cooling α.07E-08 47. J. Wenzel. & Andersen. C. Inc. L. Clump.. New York: John Wiley & Sons. J. Inc. 8th Ed.References Foust. Geankoplis.. Maus. 2nd Ed. Principles of Transport Processes and Separation Processes. Principles of Unit Operations. 4th Ed.. Inc.. (2003). Perry's Chemical Engineers' Handbook. Maloney. New Jersey: Pearson Education. B. C. (2008). (1980). . New York: Mc Graw-Hill. L. A.