Effect of Different Plenum-Chamber Coefficients on the Frosting of Air-Cooler

The performance of the air-cooler in refrigeration systems plays a key role in their energy efficiency. Here, the plenum-chamber coefficient was defined to investigate a possible way of enhancing the refrigeration coefficient that reflects the efficiency of the system. To investigate the influence of the plenum-chamber coefficient on the frosting and the cooling system of the air-cooler, three plenum-chamber coefficients (0.74, 0.97, 1.2) were studied under two different relative humidities. The temperature decreasing curve of the environmental chamber, the velocity distribution of the air-cooler, and the frost accumulation under and on the air-cooler were analyzed. We find that the homogeneity of the velocity distribution of the air-cooler and the frost accumulation increase with a growing plenum-chamber coefficient, while the frost accumulation on the fin will first increase and then decrease with the increase in the plenum-chamber coefficient. In general, frosting is more present when the plenum-chamber coefficient is 0.97.

The Design and Building of Medium Capacity Drying House for Bokar

Bokar, processed rubber material, is latex obtained from rubber trees of community plantations. The quality of latex can be identified from its features which are white, relatively soft, and odorless. The purpose of this research was to design a simple rubber sheet drying house and examine the quality of dry rubber under Indonesian National Standard. Bokars are processed using a liquid smoke coagulant with a concentration of 10-15% and it obtained a clean white rubber although it has a slight smoke smell. Before drying, Bokar had ground to gain the thickness of the unsmoked sheet/ USS around 3-5 mm. The components of the drying house include the drying room, heating room, heater, thermometer, blower, plenum chamber, ventilation, drying room door, and electric motor. The capacity of the drying house is 200 kg of rubber sheet, with a drying temperature of 35 – 46oC and 6 hours drying time. The rubber produced has good quality with average dry rubber content (DRC) was 73.75%.

Study on The Effect of Different Plenum Chamber Coefficients on Frosting of Air-cooler

The performance of the air-cooler in the refrigeration system plays a key role in improving the energy efficiency. Here, the plenum chamber coefficient was defined to study a possible way of enhancing the refrigeration system performance. In order to investigate the influence of the plenum chamber coefficient on the frosting and the cooling system of the chillers, three plenum chamber coefficients (0.74,0.97,1.2) were studied under high humidity. The temperature decreasing curve of the environmental chamber, the velocity distribution of the air cooler, and the frost accumulation under and on the air-cooler were analysed. The results show that the frost accumulation on the tube will increase with the increase of the plenum chamber coefficient and the frost accumulation on the fin will increase at first and then decrease with the increase of the plenum chamber coefficient. On the whole, in this study, frosting is the most obvious when the plenum chamber coefficient was 0.97

DESIGN AND DEVELOPMENT OF SEMI-DIRECT COPRA DRYER FOR FLAT TERRAIN

The study was conducted to design and develop a semi-direct dryer for flat terrain. This dryer was designed to provide farmers an alternative to traditional and existing dryers particularly the semi-direct and indirect dryers. The components of the dryer were drying bed, plenum chamber, tunnel and firing chamber. It has a capacity of 2,000 nuts and the husks from the nuts were used as fuel for the dryer. The means of the average drying temperature on the front, middle and rear portions of the drying platform were 56.5 oC, 58.2 oC, and 58.4 oC, respectively. The average time of drying in bringing down the moisture content of the copra from 50% to 12% wet basis was 24 hours using only 66.30% of the husks. As of January 2017, the total cost of the dryer with shed was P 61,100.00 and the computed break-even cost was P 1.82/kg. The performance of the dryer is comparable to the existing dryers.

Investigation on Acoustic Properties of Thruster Chamber with Coaxial Injectors and Plenum Chamber

Based on the URANS equation, a numerical simulation is carried out for acoustic properties of the thruster chamber with coaxial injectors and plenum chamber in a liquid rocket engine. Pressure oscillations with multiacoustic modes are successfully excited in the chamber by using the constant volume bomb method. FFT analysis is applied to obtain the acoustic properties of eigenfrequencies, power amplitudes, and damping rates for each excited acoustic mode. Compared with the acoustic properties in the model chamber with and without an injector as well as with and without the plenum chamber, it can be found that the injector with one open end and one half-open end still can work as a quarter-wave resonator. The power amplitudes of the acoustic mode can be suppressed significantly when its eigenfrequency is close to the tuning frequency of the injector, which is achieved by Cutting down the pressure Peak and Raising up the pressure Trough (CPRT). Compared with the acoustic properties in the model chamber with and without the plenum chamber, it can be found that 1L acoustic pressure oscillation is inhibited completely by the plenum chamber and other acoustic pressure oscillations are also suppressed in a different extent. The injector and plenum chamber have a little effect on the eigenfrequencies and damping rate of each acoustic mode. For multimode pressure oscillation, it is better for tuning frequency of the injector closing to the lower eigenfrequency acoustic mode, which will be effective for suppression of these multiacoustic modes simultaneously.

Aerodynamic characteristics of helicopter engine side air intakes

PurposeAerodynamic characteristics of engine side air intakes for a lightweight helicopter are investigated aiming to achieve an efficient engine airframe integration. Design/methodology/approachOn a novel full-scale model of a helicopter fuselage section, a comprehensive experimental data set is obtained by wind tunnel testing. Different plenum chamber types along with static side intake and semi-dynamic side intake configurations are considered. Engine mass flow rates corresponding to the power requirements of realistic helicopter operating conditions are reproduced. For a variety of freestream velocities and mass flow rates, five-hole pressure probe data in the aerodynamic interface plane and local surface pressure distributions are compared for the geometries. FindingsIn low-speed conditions, unshielded, sideways facing air intakes yield lowest distortion levels and total pressure losses. In fast forward flight condition, a forward-facing intake shape is most beneficial. Additionally, the influence of an intake grid and plenum chamber splitter is evaluated. Originality/valueThe intake testing approach and the trends found can be applied to other novel helicopter intakes in early development stages to improve engine airframe integration and decrease development times.