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It is often necessary in fluid flow systems to simultaneously decelerate and turn the flow. This can be achieved by employing turning diffusers in the fluid flow systems. The flow through a turning diffuser is complex, apparently due to the expansion and inflexion introduced along the direction of flow. The flow characteristics of 3-D turning diffuser by means of varying inflow Reynolds number are presently investigated. The flow characteristics within the outlet cross-section and longitudinal section were examined respectively by the 3-D stereoscopic PIV and 2-D PIV. The flow uniformity is affected with the increase of inflow Reynolds number due to the dispersion of the core flow throughout the outlet cross-section. It becomes even worse with the presence of secondary flow, 22% to 27% of the mean outlet velocity. The flow separation takes place within the inner wall region at the point very close to the outlet edge and the secondary flow vortex occurs dominantly within half part of the outlet cross-section. [ABSTRACT FROM AUTHOR]

A feasibility study was performed on a two-evaporator system for humidity control. The two-evaporator system considered requires the addition of a reheat coil to the conventional unit. The reheat coil serves to reheat the cooled air leaving the cooling coils, thereby controlling the relative humidity. An experimental study was performing using a modified commercial ceiling concealed air conditioning unit. Results from the experiments show that the dehumidification capability is improved by 11%. However, the cooling performance was reduced by 13%. It is possible to control the relative humidity of the leaving air by adjusting the refrigerant temperature at the inlet of the reheat coil but at the cost of cooling performance. [ABSTRACT FROM AUTHOR]

The cross flow fan is a unique type of turbo machinery where the air stream flows transversely across the impeller, passing the blades twice. Due to its complex geometry, and highly turbulent and unsteady air-flow, a numerical method is used in this work to conduct the characterization study on the performance of a cross flow fan. A 2D cross-sectional model of a typical indoor air conditioning unit has been chosen for the simulation instead of a three dimensional 3D model due to the highly complex geometry of the fan. The simplified 2D model has been validated with experiments where it is found that the RMS error between the simulation and experimental results is less than 7%. The important parameters that affect the cross flow fan performance, i.e. the internal and external blade angles, the blade thickness, and the casing design, are analyzed in this study. The formation of an eccentric vortex is observed within the impeller. [ABSTRACT FROM AUTHOR]

Corrosion, erosion and plugging of the downstream equipments by tar and ash particle and, low energy content of syngas are the main problems of biomass gasification process. This paper attempts to review the findings of literature on the effect of temperature on syngas quality, and in alleviating the tar and ash problems in the gasification process. The review of literature indicates that as the gasification temperature increases, concentration of the resulting H2 and carbon conversion efficiency increase, the amount of tar in the syngas decreases. For the same condition, CH4 and CO concentration do not show consistent trend when the feedstock and gasification process varies. These necessitate the need for conducting an experiment for a particular gasification process and feedstock to understand fully the benefits of controlling the gasification temperature. This paper also tries to propose a method to improve the syngas quality and to reduce the tar amount by using preheated air and superheated steam as a gasifying media for oil palm fronds (OPF) gasification. [ABSTRACT FROM AUTHOR]

Fluidized bed drying has become one of the preferred techniques in drying of agricultural products due to its thorough mixing ability and almost uniform moisture transfer from the product. This paper reports experimental studies on drying characteristics of chopped oil palm frond (OPF) when dried in a swirling fluidized bed dryer (SFBD). Unlike conventional fluidized beds, the SFBD is capable of fluidizing agricultural products which are fibrous and irregular in size and geometry, such as chopped OPF. Experiments were conducted to study the effect of hot air temperature ranging from 50°C to 80°C at a flowrate of 450 m3/hour, for two bed loadings. The OPF which consists of leaves and petiole (petiole) has different initial moisture contents of 57% and 70% respectively and dried to a final moisture content of 15%. Although higher temperatures of hot air result in rapid initial migration of moisture from the chopped OPF, the surface hardening due to shrinkage also becomes faster and hence limits further moisture removal prom the product. The OPF leaves and petiole exhibited different drying curves, suggesting the need for drying them separately unlike the current industrial practice for optimizing the drying process. [ABSTRACT FROM AUTHOR]

An experimental study on the heat transfer performance of a fin-tube heat exchanger due to mechanical expansion of the tube by bullets has been reported in this paper. The manufacture of a fin-tube heat exchanger commonly involves inserting copper tubes into a stack of aluminium fins and expanding the tubes mechanically. The mechanical expansion is achieved by inserting a steel bullet through the tube. The steel bullet has a larger diameter than the tube and the expansion provides a firm surface contact between fins and tubes. Five bullet expansion ratios (i.e. 1.045 to 1.059) have been used in the study to expand a 9.52mm diameter tubes in a fin-tube heat exchanger. The study is conducted on a water-to-water loop experiment rig under steady state conditions. In addition, the effects of fin hardness and fin pitch are investigated in the study. The results indicate that the optimum heat transfer occurred at a bullet expansion ratio ranging from 1.049 to 1.052. It is also observed that larger fin pitches require larger bullet expansion ratios, especially with lower fin hardness. As the fin pitch increases, both fin hardness (i.e. H22 and H24) exhibit increasing heat transfer rate per fin (W/fin). With the H22 hardness temper, the increase is as much as 11% while H24 increases by 1.2%. [ABSTRACT FROM AUTHOR]

Oil palm frond is the most abundant yet untapped biomass waste in Malaysia. This paper investigates the characteristics of raw oil palm fronds and its ash to evaluate its potential utilization as a biomass fuel for gasification process using single throat downdraft gasifier. The morphological nature, elemental content, proximate and ultimate analysis and calorific value were studied. Field emission scanning electron microscopy and x-ray fluorescence were used to investigate the surface morphology, elemental and mineralogical nature of oil palm frond and its ash. The results were compared with other agricultural and forestry biomass wastes. From proximate analysis volatile matter, fixed carbon and ash were found to be 83.5%, 15.2% and 1.3%, respectively on dry basis. From ultimate analysis result values of 44.58%, 4.53%, 0.71% and 0.07% for carbon, hydrogen, nitrogen and sulfur were found respectively on dry basis. Oxygen was determined by difference and found to be 48.81%. The proximate and ultimate analysis results indicate that oil palm frond is better than agricultural wastes and less than most forestry wastes to use as a feedstock in the gasification process in order to get a better quality of syngas. The amount of ash content in OPF was found to be much less than in agricultural wastes and higher than most forestry wastes. From x-ray fluorescence analysis CaO and K2O were found as the major oxides in oil palm fronds and rice husk ash with the amount of 28.46% and 15.71% respectively. The overall results of oil palm fronds were found to be satisfactory to use as a feedstock for the process of gasification. [ABSTRACT FROM AUTHOR]