Kasni Sumeru

Effect of Prior Austenite Grain Size on the Morphology and Mechanical Properties of Martensite in Medium Carbon Steel

In industrial application, unintentional manufacturing line troubles often consequence in heating raw materials excessively, in terms of either time or temperature. One of the effects of such occurrence is a product with a variation of prior austenite grain size, even if after the heat treatment the end result is the same, martensite. The variation of the prior austenite grain size is believed to vary the end results of the martensite. This undesirable variation includes the variation of fatigue resistance, impact strength, yield strength, hardness, etc. This research studies the effect of the prior austenite grain size on the morphology of the martensite microstructure. The results show that within the typical industrial application of temperature and holding time set up, as holding time or the temperature increases, the prior austenite average diameter increases. The block and packet sizes in the martensite also increase. The variation of mechanical property dependence on the grain size is indeed due to the different characteristics reflected in the martensite morphology. With respect to the same area, smaller grain has more blocks and packets, which agrees with higher dislocation density verified with transmission electron microscopic evaluation.

Energy savings in air conditioning system using ejector: An overview

There are two ejector configurations described in the present study: ejector refrigeration cycle and the ejector as an expansion device. The use of waste heat from the car engine and industry as a heat-driven energy for air conditioning system in automobile and building can save energy. Although the ejector refrigeration cycle has a low COP, the use of waste heat as a heat-driven energy incurs a lower operational cost compared with vapor compression refrigeration system. In addition, an ejector as an expansion device can be applied in the vapor compression refrigeration cycle to improve the performance system.

Numerical Study of Ejector as an Expansion Device in Split-Type Air Conditioner

This paper presents a numerical approach for determining the motive nozzle and constant-area of an ejector as an expansion device, based on cooling capacity of the split-type air conditioner using R22 as working fluid. The use of an ejector as an expansion device in split-type air conditioner can enhance the coefficient of performance (COP) system. Typically, the split-type air conditioner may be installed on the geographical area with moderate or high outdoor air temperature using capillary tube. For this reason, the motive nozzle and constant-area diameters of the ejector must be designed according to these conditions. The diameters of the ejector are crucial in improving the COP. The results showed that the motive nozzle diameter is constant (1.14 mm) with variations of the condenser temperature, whereas the constant-area diameter decreases as the condenser temperature increases.

Performance of Ejector Refrigeration Cycle for Automotive Air Conditioning

In this study, two experiments were performed, one with the conventional compression refrigeration cycle (CRC) and the other with an ejector refrigeration cycle (ERC). The CRC system for automotive air conditioning was designed, fabricated and experiments were conducted. The system was then retrofitted with an ejector as the expansion device and experiments were repeated for the ERC system. Calculations of the entrainment ratio, compressor compression ratio and coefficient of performance (COP) were made for each cycle. The calculations showed that ERC has some advantages over the CRC. In this study, an average improvement of 5% in COP has been obtained for the ERC compared with the CRC.

Thermodynamic Analysis of Ejector as an Expansion Device on Split-Type Air Conditioner Using R410A as Working Fluid

Typically the split-type air conditioner uses a capillary tube as expansion device. To enhance the performance of the system, an ejector can be applied as expansion device to replace capillary tube. Based on the numerical modeling, the coefficient of performance (COP) of standard cycle using R410A as working fluid was slightly lower than that of R22. The use of an ejector as an expansion device on a split-type air conditioner using R410 increased the COP by 10.8%. Also, R410A has a lower total GWP impact compared with R22, which reduce negative impact on the environment.

Performance analysis of hydrocarbon mixture to replace R134a in an automotive air conditioning system

At present, most air conditioners in an automotive use R134a as working fluid. Due to the negative impact on the environment, i.e. global warming, the refrigerant must be replaced by environmental friendly working fluid. Hydrocarbons are natural fluids, no effect on the climate, inexpensive and readily available. The hydrocarbon mixture used in the present study is R436A, composed of R290 (propane) and R600a (isobutane) with a mass ratio of 56/44. The results show that the drop-in substitute from R134a to R436A reduced COP by 4.84, 4.74 and 4.64% for the condenser temperature of 40, 45 and 50°C, respectively. To generate COP improvement on the drop-in substitute, subcooling was carried out, and results show that the COP improvement was 4.42, 5.20 and 6.09% for the condenser temperature of 40, 45 and 50°C, respectively.

Performance study of DC compressor for automotive air conditioning system

The automotive air conditioning compressor (AAC) is belt-driven by the engine. The compressor speed is directly proportional to the engine speed. Therefore, the cooling capacity will vary as the engine speed changes. To meet the air conditioning (AC) demand, the compressor continually cycles on and off. In the research, the compressor of the AAC is driven by an electric motor which in turn is operated by electrical battery (12 volt). The use of direct current compressor (DCC) is seen as a solution of the existing system. Using the proposed system, DCC gets significant improvements in energy efficiency. Compared with AAC system, the energy conservation effect is about 77.5% to 86.35%.

Effect of compressor discharge cooling using condensate on performance of residential air conditioning system

This paper presents an experimental investigation on the system performance of a residential air conditioner using condensate as a compressor discharge cooler. The condensate is water produced by the evaporator surfaces. The use of condensate is to reduce the energy consumption and improve the performance of the air conditioning system. The experimental investigation has been carried out on a split-type air conditioner with cooling capacity of 2.5 kW. The utilization of condensate as a discharge cooler decreased the compressor discharge pressure and consequently, reduced the compressor power consumption by 6.3%. In addition, the effect of the decrease in the compressor discharge pressure resulted in the decrement in the temperature of condenser outlet by 2.2°C. The decrease in temperature of condenser oulet leads to the increment in the subcooling and increases in the cooling capacity.This paper presents an experimental investigation on the system performance of a residential air conditioner using condensate as a compressor discharge cooler. The condensate is water produced by the evaporator surfaces. The use of condensate is to reduce the energy consumption and improve the performance of the air conditioning system. The experimental investigation has been carried out on a split-type air conditioner with cooling capacity of 2.5 kW. The utilization of condensate as a discharge cooler decreased the compressor discharge pressure and consequently, reduced the compressor power consumption by 6.3%. In addition, the effect of the decrease in the compressor discharge pressure resulted in the decrement in the temperature of condenser outlet by 2.2°C. The decrease in temperature of condenser oulet leads to the increment in the subcooling and increases in the cooling capacity.

Energy analysis and compressor performance of refrigerator system using programmable logic control (PLC)

This project present an experimental test results on energy consumption of a refrigerator compressor triggered by using thermostat and programmable logic control (PLC). The PLC modulates the speeds of the compressor according to refrigeration load using inverter based on control law written in the PLC memory. The temperature setting for both thermostat and PLC were varied at-8 °C and-10 °C respectively. At-8°C the results indicate PLC consumed 4.45 to 6.79% less energy compared to thermostat setting. While at-10°C, the saving made through PLC is in the range of 6.43 to 12.88%. The fluctuation of freezer compartment is better when PLC controlled. As the energy input to compressor is lower due to the slower speed, this enhanced the coefficient of performance (COP).

Numerical Analysis of Modified Ejector Cycle on Ejector as an Expansion Device on Residential Air Conditioner

The present study describes thermodynamic modeling of a novel cycle of ejector as an expansion device - called modified ejector cycle (MEC) - on residential air conditioner (A/C) to further enhance the COP improvement on standard ejector cycle (SEC). The difference between the SEC and MEC is the separator, namely the SEC uses a separator that has an inlet and two outlets, whereas in modified ejector cycle (MEC), the separator has only an inlet and an outlet in the system. Due to its environmental friendliness of R290 (propane), it is used to replace R22 as a working fluid in the numerical. The modeling results on the residential air conditioner with cooling capacity of 2.5 kW using R290 as working fluid showed that the COP improvement of the MEC was 42.86% at the condenser temperature of 45°C.