• The KSFM Journal of Fluid Machinery
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• v.10 no.2 s.41
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• pp.16-21
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• 2007

Potential advantages of using vapor injection in a two stage rotary compressor for a $CO_2$ heat pump water heater system were addressed in this paper by numerical simulation. Vapor separated from a flash tank in the middle of the expansion process can be used for injection into the second stage suction plenum of the compressor to improve the system performance. Vapor injection increases the intermediate pressure between the two stages, thus increasing the first stage compressor work and reducing that of the second stage. As a whole, however, the compressor input power increases due to injected mass flow rate for the second stage. Computer simulation showed that increment of the cooling capacity by vapor injection exceeded that of the compressor work, thus improving the system performance. COP improvement by vapor injection was calculated to be about 5-14% for normal operating conditions. With vapor injection, a maximum COP was found when the displacement volume of the second stage becomes 90-95% of that of the first stage of the compressor.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.6
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• pp.592-598
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• 2015

In this study, we experimentally investigate the performance characteristics of a high-performance summer-cooling heat pump for an R410A by applying an air-cooled-type vapor-injection (VI) cycle. The devices used for the experiment consist of a VI compressor, condenser, oil separator, plate-type heat-exchanger, economizer, evaporator, and re-cooler. The experimental conditions employed for the cooling performance were divided into three cycles. First, in Cycle A, we apply a VI cycle and with no heat exchange between the evaporator outlet refrigerant and the VI cycle suction refrigerant in the re-cooler. For Cycle B, there is heat exchange, and for Cycle C, there is neither a VI cycle nor heat exchange between the evaporator outlet refrigerant and the VI cycle suction refrigerant. From the analysis results, we observe that the performance was highest in the VI cycle with heat exchange between the evaporator outlet refrigerant and the VI cycle suction refrigerant (Cycle B), while it was lowest in Cycle C without application of the VI cycle. Moreover, the cooling coefficient of Performance ($COP_C$) averaged 3.5 in Cycle B, which was 8.6% higher than the corresponding value in Cycle A, and 33% higher than that in Cycle C.

• Journal of the Korean Solar Energy Society
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• v.35 no.6
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• pp.25-33
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• 2015

In this study, heating performance of the air-cooled heat pump with vapor-injection (VI) cycles, re-heater and solar heat storage tank was investigated experimentally. Devices used in the experiment were comprised of a VI compressor, re-heater, economizer, variable evaporator, flat-plate solar collector for hot water, thermal storage tank, etc. As working fluid, refrigerant R410A for heat pump and propylene glycol (PG) for solar collector were used. In this experiment, heating performance was compared by three cycles, A, B and C. In case of Cycle B, heat exchange was conducted between VI suction refrigerant and inlet refrigerant of condenser by re-heater (Re-heater in Fig. 3, No. 3) (Cycle B), and Cycle A was not use re-heater on the same operating conditions. In case of Cycle C, outlet refrigerant from evaporator go to thermal storage tank for getting a thermal energy from solar thermal storage tank while re-heater also used. As a result, Cycle C reached the target temperature of water in a shorter time than Cycle B and Cycle A. In addition, it was founded that, as for the coefficient of heating performance($COP_h$), the performance in Cycle C was improved by 13.6% higher than the performance of Cycle B shown the average $COP_h$ of 3.0 and by 18.9% higher than the performance of Cycle A shown the average $COP_h$ of 2.86. From this results, It was confirmed that the performance of heat pump system with refrigerant re-heater and VI cycle can be improved by applying solar thermal energy as an auxiliary heat source.

• Journal of Power System Engineering
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• v.19 no.4
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• pp.69-75
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• 2015

In this study, the characteristics of heating performance of a high-performance air-cooled heat pump with vapor-injection(VI) cycle using re-heater was investigated experimentally. Devices used in the experiment is consist of a VI compressor, condenser, oil separator, refrigerant (economizer outlet refrigerant) re-heater, economizer, evaporator. And R410A was used as a working fluid. The experiment was conducted with two cycles(cycles A and B) for investigating heating performance. In case of cycle B, heat exchange was conducted by re-heater between outlet refrigerant of compressor and suction refrigerant of the VI system(Fig.1, re-heater). But the re-heater was not used in case of cycle A. As a result of this experiment, discharge temperature of refrigerator in compressor was shown higher value, when the cycle B was conducted, because of the heat exchange between suction refrigerant of VI cycle and outlet refrigerant of compressor in the re-heater than cycle A that was not use re-heater. it means that liquid hammer and the decrement of heating performance can be decreased by using re-heater. Also, Heating coefficient of performance(COPh) was shown about 2.98 in Cycle B which was 4% higher than Cycle A and from these results, It was confirmed that the improvement of the heating performance of heat pump with VI cycle can be achieved by applying re-heater.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.58-64
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• 2003

Dimethyl Ether(DME) has been considered as one of the most attractive alternative fuels for compression ignition engine. Its main advantage in diesel engine application is high efficiency of diesel cycle with soot free combustion though conventional fuel injection system has to be modified due to the physical properties of DME. Experimental study of DME and conventional diesel spray employing a common-rail type fuel injection system with a 5-hole sac type injector was performed in a constant volume vessel pressurized by nitrogen gas. Spray cone angles and penetrations of the DME spray were characterized and compared with those of diesel. For evaluation of the evaporating characteristics of the DME, shadowgraphy technique employing an Ar-ion laser and an ICCD camera was adopted. Tip of the DME spray was formed in mushroom-like shape at atmospheric chamber pressure, which disappeared in higher chamber pressure. Spray tip penetration and spray cone angle of the DME became similar to those of diesel under 3MPa of chamber pressure. Higher injection pressure provided wider vapor phase area while it decreased with higher chamber pressure condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.73-80
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• 2002

Dimethyl ether (DM) is one of the most attractive alternative fuel far compression ignition engine. Its main advantage in diesel engine application is high efficiency of diesel cycle with soot free combustion though conventional fuel injection system has to be modified due to the intrinsic properties of DME. Experimental study of DME and conventional diesel spray employing a common-rail type fuel injection system with a 5-holes sac type injector (hole diameter 0.168 ㎜/hole) was performed in a high pressure chamber pressurized with nitrogen gas. A CCD camera was employed to capture time series of spray images followed by spray cone angles and penetrations of DME were characterized and compared with those of diesel. Under atmospheric pressure condition, regardless of injection pressure, spray cone angles of the DME were wider than those of diesel and penetrations were shorter due to flash boiling effect. Tip of the DME spray was farmed in mushroom like shape at atmospheric chamber pressure but it was disappeared in higher chamber pressure. On the contrary, spray characteristics of the DME became similar to that of diesel under 3MPa of chamber pressure. Hole-to-hole variation of the DME spray was lower than that of diesel in both atmospheric and 3MPa chamber pressures. At 25MPa and 40MPa of DME injection pressures, regardless of chamber pressure, intermittent DME spray was observed. It was thought that vapor lock inside the injector was generated under the two injection pressures.

• Journal of the Semiconductor & Display Technology
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• v.20 no.3
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• pp.22-26
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• 2021

Thin-film encapsulation (TFE) technology is most effective in preventing water vapor and oxygen permeation in the organic light emitting diodes (OLED). Of those, a laminated structure of Al₂O₃ and MgO were applied to provide efficient barrier performance for increasing the stability of devices in air. Atomic layer deposition (ALD) method is known as the most promising technology for making the laminated Al₂O₃/MgO and is used to realize a thin film encapsulation technology in organic light-emitting diodes. Atomic layer deposited inorganic films have superior barrier performance and have advantages of excellent uniformity over large scales at relatively low deposition temperatures. In this study, the control system of the MgCP₂ precursor for the atomic layer deposition of MgO was established in order to deposit the MgO layer stably by the injection time of second level and the stable heating temperature. The deposition rate was obtained stably to be from 4 to 10 Å/cycle using the injection pulse times ranging from 3 to 12 sec and a substrate temperature ranging from 80 to 150 ℃.

• Transactions of the Korean hydrogen and new energy society
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• v.5 no.2
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• pp.91-98
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• 1994

In this study hydrogen gas and oxygen gas are used to make a pollution-free engine which is a closed system with the components such as a combustor, two turbines, a radiator and a compressor. One of the two turbines produces main power, and the other is used to drive a compressor to compress unburned gases and to return them to the combustor. Some of the water from the radiator is pumped to cool down the internal wall of the combustor and to be used as a working fluid which expands from liquid state to vapor state to get more expansion work. The possibility of operating the whole system is checked by the thermodynamic analysis to make the closed engine system. The calculations in the thermal analysis are based on the Brayton cycle and the Rankine cycle. The closed system in this study shows similar efficiency as usual internal combustion engines, but it produces water only without air pollution such as $NO_x$ and soot.

• Journal of the Semiconductor & Display Technology
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• v.21 no.1
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• pp.67-70
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• 2022

In order to prevent water vapor and oxygen permeation in the organic light emitting diodes (OLED), Al₂O₃ thin-film encapsulation (TFE) technology were investigated. Atomic layer deposition (ALD) method was used for making the Al₂O₃ TFE layer because it has superior barrier performance with advantages of excellent uniformity over large scales at relatively low deposition temperatures. In this study, the thickness of the Al₂O₃ layer was varied by controlling the numbers of the unit pulse cycle including Tri Methyl Aluminum(Al(CH₃)₃) injection, Ar purge, and H₂O injection. In this case, several process parameters such as injection pulse times, Ar flow rate, precursor temperature, and substrate temperatures were fixed for analysis of the effect only on the thickness of the Al₂O₃ layer. As results, at least the thickness of 39 nm was required in order to obtain the minimum WVTR of 9.04 mg/m²day per one Al₂O₃ layer and a good transmittance of 90.94 % at 550 nm wavelength.

• Plant Journal
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• v.11 no.2
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• pp.32-38
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• 2015

This study was conducted on combined cycle power plant consisting of HRSG with integral deaerator type to avoid tube failures of low pressure evaporator tubes. Based on the observation of pH variation at the discharge of boiler feed water pump by continuous pH measurement for a period of time, it was identified that pH of feed water is getting reduced as ammonia is distributed into vapor and liquid depending on the distribution ratio of ammonia in the LP drum after the deaerator. To solve this problem, the counterplan was prepared by reexamination of ammonia injection point and quantity. In conclusion, it was accomplished that 9.2~9.6 is the optimized pH range for boiler feed water by arranging additional piping for ammonia to inject directly to LP drum.