Investigation of Micro CT based method for porosity estimation of sintered-wick heat pipes.

The use of sintered-wick heat pipes in heat exchanger performance-related studies gained popularity owing to the simplicity and affordability of heat pipes. Evaluation of the system performance may be based on various arrangements and numbers of heat pipes applicable to the literature. Wick porosity and permeability are critical parameters for the investigation of wick capillary pumping, which will ultimately determine heat pipe performance. Despite the significance of these parameters to thermal performance, they are difficult to obtain, as the methods for obtaining these parameters before installing the heat pipes are time-consuming and destructive. This study aims to investigate the feasibility of Micro Tomography (Micro CT) to observe the porosity of copper sintered-wick heat pipes. Visual data from three heat pipe samples, namely HP1, HP2, and HP3 are quantified and analyzed. Analysis of the average porosity of HP1 and HP2 samples showed a similar value of 47.6 and 48.1%, respectively; however, the value of porosity along the length of the scanned area shows a bigger range of 42-54%. The accuracy of Micro CT was tested by testing three porosity samples with designed porosity of 26%, 22.3%, and 16.6% which were 3D printed using atomic diffusion additive manufacturing technology. Each sample was designed with pore shapes hexagonal, circular, and elliptical, respectively. Micro CT visualization and analysis showed the porosity reduction of the 3D printed porosity samples compared to the CAD design. Due to the smallest reduction of porosity after the sintered process, the 3D printed sample with a hexagonal pore shape, and the designed porosity of 26%, this sample was recommended for sintered wick fabrication using this technology and to test the accuracy of Micro CT.

Development of indirect evaporative cooler based on a finned heat pipe with a natural-fiber cooling pad.

Evaporative cooler is one of the methods that have been used to keep buildings at a comfortable temperature since ancient times. This type of cooler is particularly suitable for hot and arid areas. This research examines the design and testing of an indirect evaporative cooler system utilizing heat pipes as heat exchangers and natural fibers as cooling pads. An experiment was performed on a laboratory scale with three different types of natural fiber cooling pad materials: pineapple leaf, ramie, and luffa fibers. The air temperatures to be conditioned was 40 °C, with three variations of the intake airflow velocities of 0.4, 1.1, and 1.8 m/s. According to the results of this experiment, an indirect evaporative cooler system utilizing pineapple leaf fiber as a cooling pad performs better than those employing luffa and ramie fibers as cooling pads. The maximum wet bulb effectiveness of the system using pineapple fiber was 85%, maximum dew point effectiveness was 65%, and maximum energy efficiency ratio was 52.5 Btu/W.As a passive heat exchanger, the performance of finned heat pipes is also investigated, with a maximum heat absorption of 527.6 W and a temperature reduction of 9.9 °C.

Design, synthesis and antiamoebic activity of dysprosium-based nanoparticles using contact lenses as carriers against Acanthamoeba sp.

PURPOSE: Contact lenses have direct contact with the corneal surface and can induce sight-threatening infection of the cornea known as Acanthamoeba keratitis. The objective of this study was to evaluate the dysprosium-based nanoparticles (Dy-based NPs), namely Fe3 O4 -PEG-Dy2 O3 nanocomposites and Dy(OH)3 nanorods, as an active component against Acanthamoeba sp., as well as the possibility of their loading onto contact lenses as the drug administering vehicle to treat Acanthamoeba keratitis (AK). METHODS: The Dy-based NPs were synthesized, and they were loaded onto commercial contact lenses. The loading content of the NPs and their release kinetics was determined based on the absorbance of their colloidal solution before and after soaking the contact lenses. The cytotoxicity of the NPs was evaluated, and the IC50 values of their antiamoebic activity against Acanthamoeba sp. were determined by MTT colorimetric assay, followed by observation on the morphological changes by using light microscopy. The mechanism of action of the Dy-based NPs against Acanthamoeba sp. was evaluated by DNA laddering assays. RESULTS: The loading efficiencies of the Dy-based NPs onto the contact lens were in the range of 30.6-36.1% with respect to their initial concentration (0.5 mg ml-1 ). The Dy NPs were released with the flux approximately 5.5-11 µg cm-2  hr-1 , and the release was completed within 10 hr. The emission of the NPs consistently showed a peak at 575 nm due to Dy3+ ion, offering the possible monitoring and tracking of the NPs. The SEM images indicated the NPs are aggregated on the surface of the contact lenses. The DNA ladder assay suggested that the cells underwent DNA fragmentation, and the cell death was due most probably to necrosis, rather than apoptosis. The cytotoxicity assay of Acanthamoeba sp. suggested that Fe3 O4 -PEG, Fe3 O4 -PEG-Dy2 O3 , Dy(NO3 )3 .6H2 O and Dy(OH)3 NPs have an antiamoebic activity with the IC50 value being 4.5, 5.0, 9.5 and 22.5 µg ml-1 , respectively. CONCLUSIONS: Overall findings in this study suggested that the Dy-based NPs can be considered as active antiamoebic agents and possess the potential as drugs against Acanthamoeba sp. The NPs could be loaded onto the contact lenses; thus, they can be potentially utilized to treat Acanthamoeba keratitis (AK).

The use of beeswax as heating element in non-electric infant incubator.

Non-electric infant incubators are needed in remote areas that have no access to electricity to reduce infant mortality nationwide. In previous studies, non-electric infant incubators have been developed using phase change material of beeswax as the heating element. This study aims to improve the performance of beeswax non-electric infant incubator to obtain a more reliable and practical one. The design of the original beeswax cartridge in the form of copper boxes was modified into tubes of stainless steel. The geometry and location of the air holes were also modified. Wood that was previously used as the body material was replaced with polyurethane to reduce the weight of the incubator. The beeswax cartridges were heated using boiling water until the beeswax melted. For temperature measurement, five 0.5 mm k-type thermocouples were placed inside of the incubator according to the National Industrial Standard of SNI 16-4221. The beeswax cartridge arrangement was varied to obtain the best performance. The results showed that polyurethane provides infant incubator lighter and more practical to use. The new design of non-electric infant incubator was capable of providing a temperature of 32-36 °C for 2 h.