Laser Induced Transient Photothermal Radiometry in Opaque Samples

A radiometer system has been designed and constructed for measurements of optical, thermal and related properties of two distinct categories of opaque samples. It was used exclusively for highly light absorbing and/or diffusing samples (protective coatings and ceramics) and highly reflecting samples (metals and its alloys). In the measurements, the signals were initially generated by localised pulsed laser heating of the sample. The signals were then monitored directly by detecting changes in infrared radiation or indirectly by measuring the deflection of the reflected probe beam. The underlying theory behind the technique and the design criteria for the radiometer are discussed. The theory has been described for the case of direct signal detection and as well as for the case of indirect signal detection. The performance of each type of detection was duly evaluated and found that the indirect detection displayed much higher signal-to-noise ratio for the respective intended application

Microwave application for the detection of biodiesel-glycerine and biodiesel-water interfaces in the biodiesel production

In biodiesel industry there is a need to detect interfacing layer between biodiesel and glycerine after the transesterification and interfacing layer between water and biodiesel after the washing process. The detection of these two interfaces is important for separation process. In this work, a simple, low cost, and accurate microwave reflection type system for production of coconut biodiesel has been applied for the detection these interfaces. A module that works at 10.7 GHz, consisting of a microwave generator and a detecting diode, is used to measure the microwave reflection coefficient at various positions through the tank. The experimental results show the ability of the system to detect the level or height of these interfaces at the accuracy of 0.1 mm

Development of planar microwave moisture sensors for hevea rubber latex and oil palm fruits

A review of the several moisture sensors using planar structures such as microstrip, conductor-backed coplanar waveguide (CBCPW) and microstrip antenna is described. These sensors are used for determination of moisture content in hevea rubber latex and oil palm fruit. This study includes the state of the art of sensor design by which the dielectric constant and dielectric loss of the hevea latex and oil palm are taking into consideration. A prototype developed known as microwave reflection type latexometer is able to measure the moisture content of hevea latex with the accuracy of less than 1% and suitable to be used at latex collecting center and latex dipping industries for process control. A close relationship has been found between insertion loss and moisture content in the mesocarp of oil palm fruit for the CBCPW sensor. This relationship will give the possibility of using this sensor to gauge fruit ripeness or oil content in the mesocarp

Numerical solution of transient temperature for pulsed heating in a single spherical particle model

The transient temperature for pulsed heating in a single spherical model has been derived using the Laplace transform algorithm based on Fourier series. We assumed that the substrate is a thermally bad conducting surface and then head conduction at the interface can be neglected. The computation for the transient surface temperature of the particle was performed in such a way as to obtain a straightforward deviation of the analytical solution (12) from the numerical result. It has been proved that for some particles (α < 0.005) the analytical solution provided a reasonably accurate description of the model, otherwise the numerical solution should be used in the general case

Dual frequency microstrip antenna sensor for water content measurements independent of temperature variation

Temperature variation causes errors in all indirect moisture measurement methods. To increase the accuracy of moisture content determination and to reduce the influence of temperature, a two-parameter measurement is used. The method uses the magnitude of reflected waves at two microwave frequencies in the X-band region. A dual frequency sensor system is developed to measure moisture content of dielectric-lossy liquids. The experiment is based on measurements of far-field reflection magnitudes at two different frequencies 8.48 GHz and 10.69 GHz using circular microstrip antennas. A calibration equation is sought that instantly gives temperature-independent moisture content of the samples under consideration. The sensor is integrated with a data acquisition card to record the detected reflection signals. The data analysis and error-correction technique are implemented using custom designed software. The system is tested using diluted rubber latex with moisture content ranging from 39.8% to 91.2% wet basis. The moisture content was predicted with a standard error less than 1.3% for the temperature range of 25 °C to 63 °C compared to the standard oven-drying techniqu

Application of surface plasmon resonance in biodiesel characterization

Surface plasmon resonance is a versatile technique for characterizing biomaterials. In this work the optical parameter and Lorentz-Lorenz constant for biodiesel were determined. According to the experimental data for biodiesels base on palm oil and coconut oil mixture with methanol the accuracy and sensitivity of SPR for these materials is limited by the measurement resolution of 0.001

Thermal diffusivity measurement of BSCCO superconductor (85 to 300 K) using PVDF transducer

Thermal diffusivity measurement of the Bi-Pb-Sr-Ca-CII-O superconducting ceramic sample is reported. In this work camera flash and polyvinylidene difluoride (PVDF) film were respectively used as heating source and pyroelectric detector. The theoretical signal calculation based on Dirac- function approximation for camera flash temporal profile was used to deduce the thermal diffusivity. The measurement was done from 85 K to room temperature. The thermal diffusivity curve shows a dip at the resistive transition onset temperature and a cusp at the zero-resistance temperature. Thus, we found that the PVDF transducer is very effective in determining the normal-to-superconductor transition phenomena and also for the measurement of the thermal diffusivity of the superconducting samples at low temperatures

Application of the pyroelectric sensor for study of porosity effect on thermal diffusivity of nickel copper zink ferrite

An investigation was carried out to study the effect of the porosity on thermal diffusivity of Nickel Copper Zinc Ferrite. The experimental technique employed to measure thermal diffusivity was the photoflash technique, and the measurements were carried out at room temperature. The heating source consists of camera flash having approximately 5ms pulse duration and a thin film of polyvinylidene difluoride (PVDF) attached to the back of the samples was used as detector. Six different porosity levels were obtained by varying the grinding time following the presintering process and preceding the sintering process at 1350°C. The porosity range obtained for the Ni0.3Cu0.1Zn0.6Fe2O4 samples was 1.8-7%. The thermal diffusivity was determined from the experimental thermal transient signal. For the fitting of the experimental results, the analytical model used was based on the approximation that the pulse duration of the camera flash can be considered as Dirac-δ function. Thermal diffusivity values for Ni0.3Cu0.1Zn0.6Fe2O4 samples were in the range (7.8-8.7) × 10-7 m2/s

Selection and evaluation of materials for solar heater boxes and their capacity in trapping solar energy

The selection and evaluation of solar heaters for trapping and using solar energy to disinfest legume grains are described. The effectiveness of five materials (cardboard, plywood, Perspex timber and metal) in collecting heat as temperature from the sun was investigated two different linings materials were used to coat solar heater boxes aluminium foil, and black paint. Solar heater boxes were covered with clear plastic to trap solar radiation. Cardboard and plywood were the best materials to construct the solar heater boxes as they trap and retained more heat due to their high thermal diffusivity compared to perspex and timber solar heater boxes. In addition, these materials are cheaper and easier to handle compared to metal. It was also concluded that, aluminium foils combined with black paint was the best lining than aluminium foil or black paint used separately. The effect of seed depth on solar energy collection inside cardboard and plywood solar heater boxes was also evaluated. Temperatures trapped in cardboard solar heater boxes with 7 kg of seeds was 13.9% higher than temperatures trapped in plywood solar heater boxes. Therefore, cardboard solar heater boxes were better than plywood solar heater boxes