Chul Woo Roh

VAPOR REFRIGERANT INJECTION TECHNIQUES FOR HEAT PUMP SYSTEMS: THE LATEST LITERATURE REVIEW AND DISCUSSION

This paper reviews the latest and major research on vapor refrigerant injection techniques. Various vapor refrigerant injection techniques are discussed and compared. Compared to the basic vapor injection (VI) cycle, double-expansion VI cycle, accumulator-VI cycle and the VI cycle in a cascade system are briefly explained. Studies about these various VI cycles do not only prove the performance of VI cycles, but also show variations of VI cycles. Discussions about the fundamental issues of the VI cycle are also presented.

MACROSCOPIC SPRAY BEHAVIOR AND ATOMIZATION CHARACTERISTICS OF R407C INJECTION

This study investigated the spray behavior and atomization characteristics of refrigerant R407C injection in a high pressure chamber under various ambient pressure conditions using a spray visualization system and image processing methods. In order to observe the spray behavior of refrigerant R407C, the spray images were analyzed in time series after the start of injection. From images of spraying features, spray characteristics, for example, the spray tip penetration and cone angle were investigated by using the contour map of the light intensity levels. By using these processes, qualitative properties of refrigerant, when it is discharged from the valve, were quantified.

Study on the Power-Grid Impact and Optimal Charging Control Strategy with PHEV Market Penetration

Plug-in hybrid electric vehicle (PHEV) with capability of being recharged from the power-grid will reduce oil consumption. Also, the PHEV will affect the utility operations by adding additional electricity demand for charging. In this research, the power-grid impact by demand of PHEV charging is presented and the optimal charging control strategy for utility operators is proposed with simulated data. The penetration of PHEV is assumed to be 50% in the circumstances of Korean passenger car market and Korean power-grid market limitedly. To obtain smooth load shape and utilize the surplus electricity in power-grid at midnight and dawn, the peak of charging demand should be controlled to be located before 4:00 a.m., and the time slot which can supply the electricity power to PHEV should be allowed between 1:00 a.m.7:00 a.m.

Study on the Fueling Economic Feasibility of Plug-in Hybrid Electric Vehicle

Abstract The most concerning issue of these days is the energy crisis caused by increasing threat of dependence on imported oil and volatile market trend. Under these circumstances, the PHEV(plug-in hybrid electric vehicle) is drawing attention for the next generation’s car which could give a chance to decrease the dependence on imported oil and reduce the environmental impact of vehicle. The fueling cost of PHEV, one of the core factor of decision about buying car, should be calculated in the circumstances of Korea to make sure that PHEV has competitive power in real market. The fuel cost saving of PHEV versus CV(conventional vehicle) is simulated and discussed in the condition of increasing gasoline cost, electricity rate, and city-gas rate. In conclusion, the PHEV60-FS shows the best economic feasibility when gasoline price goes up. The PHEV20 has the most stable economic feasibility as electricity rate increases. The fuel cell cogeneration system for RPG could be an alternative for charger of PHEV in the near future.