Effect of Ga modification on different pore size silicas in synthesis of LLDPE by copolymerization of ethylene and 1-hexene with [<Emphasis Type="Italic">t</Emphasis>-BuNSiMe<Subscript>2</Subscript>Flu]TiMe<Subscript>2</Subscript>/MMAO catalyst

Copolymerization of ethylene and 1-hexene for obtaining the linear low-density polyethylene was conducted along with silicas as supports for [t-BuNSiMe₂Flu]TiMe₂/MMAO catalyst. Two silicas with different pore sizes were used to investigate the effect of pore sizes on copolymerization. In addition, gallium was also introduced into both silicas to improve their properties and enhance the catalytic activities of the system. It was found that before modification, the larger pore silica exhibited higher catalytic activity than the smaller one due to low internal diffusion resistance. After modification, both silicas exhibited higher catalytic activity comparing to their pristine condition. However, 1-hexene incorporation in the obtained copolymers was lower. The reduced surface area of silica after modification was the main reason for the decrease in 1-hexene incorporation. The properties of the copolymers by means of differential scanning calorimetry, gel permeation chromatography, and ¹³C NMR spectroscopy were further discussed in more detail.     

Natural working fluids for solar-boosted heat pumps

The option of using natural working fluids as a substitute of R-22 for solar-boosted heat pumps depends not only upon thermal performance and hazardous rating but also on potential impacts on the environment. This paper presents the comparative assessment of natural working fluids with R-22 in terms of their characteristics and thermophysical properties, and thermal performance. Some justification is given for using natural working fluids in a solar boosted heat pump water heater. The results show that R-744 is not suitable for solar-boosted heat pumps because of its low critical temperature and high operational pressures. On the other hand, R-717 seems to be a more appropriate substitute in terms of operational parameters and overall performance. However, major changes in the heat pumps are required. R-290 and R-1270 are identified as candidates for direct drop-in substitutes for R-22.     

Synthesis of polyethylene/coir dust hybrid filler via in situ polymerization with zirconocene/MAO catalyst for use in natural rubber biocomposites

In This study, polyethylene/coir dust hybrid filler was synthesized by in situ polymerization using a zirconocene/MAO catalytic system. The obtained hybrid filler was then used for the production of natural rubber biocomposites. The synthesis process of the filler was investigated with variation of coir dust loadings. It was found that increasing the amount of coir dust decreased the catalytic activities due to negative supporting effects. After introducing the PE/coir dust hybrid filler into natural rubber, SEM micrographs showed that the PE/coir dust filler were more compatible with the natural rubber matrix than the pure coir dust. This is owing to the hydrophobicity of the polyethylene in the hybrid filler. The results from a dynamic mechanical analysis showed that the natural rubber biocomposites with the hybrid filler provided a greater storage modulus than that with the pure coir dust. This suggests that the enhanced stiffness of the natural rubber biocomposites is probably due to the strong interaction between the hybrid filler and the natural rubber matrix. The strong interaction in the biocomposite can be confirmed by the low value of a loss factor (tan δ), which indicates a low degree of molecular mobility of the polymer chains, resulted from good adhesion on the filler surfaces.     

Trihalomethanes formation potential of shrimp farm effluents

Shrimp farm effluents along the Bangpakong River in the Chachoengsao Province of Thailand were evaluated for their trihalomethane formation potential (THMFP) and related parameters. The dissolved organic carbon (DOC), salinity and bromide ion concentrations of shrimp farm effluents were in the ranges of 12-14 mg/L, 0.1-14.5 ppt, and 0-14 mg/L, respectively. The dissolved organic matter was fractionated into hydrophobic and hydrophilic fractions having a range concentration of 3-5 and 8-10mg/L, respectively. The THMFP for all shrimp farm effluents analyzed was in the range of 810-3100 microg/L. The hydrophilic organic fraction was found to be a more active precursor of trihalomethanes (THMs) with 700-966 microg/L THMFP obtained from this fraction, while only 111-363 microg/L THMFP was derived from the hydrophobic fraction. The experimental results showed that salinity and bromide played crucial roles in the formation of THMs. At low salinity and bromide levels, chloroform was the dominant THM species, whereas at high salinity and bromide levels, bromoform became the dominant species. A Fourier Transform Infrared (FTIR) spectrum analysis of the samples before and after chlorination illustrated that the functional groups involved in the THM formation reaction were phenolic compounds, amines, aromatic hydrocarbons, aliphatic bromo-compounds, and aliphatic chloro-compounds.     

Wind power potential and characteristic analysis of Chiang Mai,Thailand

An investigation of wind characteristics and wind energy potential at Chiang Mai Province, Thailand was studied. Wind data taken from the weather station at Chiang Mai International Airport between 2001–2006 was analyzed in order to obtain the potential energy generated by a Vertical Axis Wind Turbine (VAWT). It was found that the yearly average wind velocity was 5.7 meters per second with a standard deviation value of 2.2 meters per second. The analysis assumed that wind blew in the S.W. to N.E. direction. Two parameters for the local wind, the shape parameter (k) and scale parameter (c) were obtained at 2.928 and 6.381 meters per second, respectively. The estimated power that could be generated by a Vertical Axis Wind Turbine was 183.09 W/m² at 30 meters above ground level. This particular site corresponds to class 1 wind power. This level of power density may be adequate for non-connected electrical and mechanical applications, such as battery charging and water pumping.     

Solar heat pump systems for domestic hot water

Vapour compression heat pumps can upgrade ambient heat sources to match the desired heating load temperature. They can offer considerable increase in operational energy efficiency compared to current water heating systems. Solar heat pumps collect energy not only from solar radiation but also from the ambient air. They can operate even at night or in totally overcast conditions. Since the evaporator/collector operates at temperatures lower than ambient air temperature it does not need glazing or a selective coating to prevent losses. Currently, however, they are not used much at all in domestic or commercial water heating systems. In this paper comparison is made of a conventional solar hot water system, a conventional air source heat pump hot water system and a solar heat pump water heating system based on various capital city locations in Australia. A summary is given of specific electricity consumption, initial and operating costs, and greenhouse gas generation of the three systems dealt with in this paper. The ultimate choice of unit for a particular location will depend heavily on the solar radiation, climate and the local price paid for electricity to drive or boost the unit chosen.     

Catalytic performance of ZnO nanoparticle in formation of LLDPE/ZnO nanocomposites

ZnO nanoparticle was used for preparing supported catalyst, which was applied in copolymerization of ethylene and 1-octene to obtain LLDPE/ZnO nanocomposite. There were two different impregnation methods (in situ and ex situ) in preparing the nano-ZnO supported catalyst. The investigation to compare both methods was conducted by employing various 1-octene initial concentrations in copolymerization. It was found that a heterogeneous catalytic system comprised a supported catalyst, prepared by in situ impregnation, provided higher catalytic activities and 1-octene incorporations compared to those of ex situ impregnation under similar condition perhaps due to closer similarity to a homogeneous system. For the ex situ impregnation, it was found that when zirconocene was directly impregnated onto the support, the catalytic activity decreased. This was due to zirconocene close vicinity to the supports and even deep into the support structure proved by XPS and TGA measurements. Therefore, it was more inaccessible to monomer attack and reducing the catalytic activity. The separate study on each catalytic system relating to the comonomer effect was also conducted by applying initial comonomer concentrations varied between 0 and 18?mmol. The increase in catalytic activity with increasing comonomer concentration can be considered as a positive comonomer effect, and the opposite was true for a negative comonomer effect. It was found that both positive and negative comonomer effects occurred in in situ impregnation and ex situ impregnation systems with Zn/(Al?+?Zr) support, whereas only positive comonomer effect was found in an ex situ impregnation system with Zn/Al support. This suggested that the comonomer effect was varied according to the nature of each system. The polymer properties, such as relative crystallinity and thermal properties were also investigated and found to alter with 1-octene concentration.     

Effect of nano-SiO2 particle size on the formation of LLDPE/SiO2 nanocomposite synthesized via the in situ polymerization with metallocene catalyst

Here, we revealed the effect of particle size of the nanoscale SiO₂ on catalytic and characteristic properties of LLDPE/nano-SiO₂ composites synthesized via the in situ polymerization with a zirconocene/MAO catalyst. In the experiment, SiO₂ (10 and 15 nm) was first impregnated with MAO. Then, copolymerization of ethylene/1-hexene was performed in the presence of nano-SiO₂/MAO to produce LLDPE/nano-SiO₂ composites. It was found that the larger particle exhibited higher polymerization activity due to fewer interactions between SiO₂ and MAO. The larger particle also rendered higher insertion of 1-hexene leading to decreased melting temperature (T_m). There was no significant change in the LLDPE molecular structure by means of ¹³C NMR.     

Comparison of Conventional Flat-Plate Solar Collector and Solar Boosted Heat Pump Using Unglazed Collector for Hot Water Production in Small Slaughterhouse

This study presents simulated results of solar water heating systems in a small slaughterhouse using two techniques. The first one is a normal solar water heating system using a flat-plate solar collector and the second one uses a solar-boosted heat pump system having a corrugated metal sheet roof as a solar collector. The number of solar collector units is between 1 and 5, and the volume of water in a storage tank is 300–1200 L. The heat pump in this work uses refrigerant mixture R22:R124:R152a of 20%:57%:23% as the working fluid. The weather conditions of Chiang Mai, Thailand, are taken as the input data. In the case of the normal solar water heating system, the shortest payback periods for 300, 600, 900, and 1200 L water are 3.63, 3.12, 2.95, and 2.82 yr, respectively. The suitable number of collectors for 300 L water is 1 unit with 600–900 L water storage; 2 units of collectors is suitable in the case of 1200 L water, and 3 units of collectors gives the shortest payback period. However, in the case of a solar heat pump system, the suitable payback periods for 300, 600, 900, and 1200 L water are 2.74, 1.79, 1.83, and 1.88 yr, respectively. In our case, 1 unit of this collector gives the shortest payback period.