Yongseok Jeon

Experimental Analysis on the Performance Characteristics of an Ejector according to Inlet Pressure and Nozzle Position

In this study, the performance of an ejector in the refrigeration cycle was experimentally studied using R600a. The performance of the ejector is analyzed according to the inlet pressure and nozzle position. The increase in the primary nozzle pressure decreased the pressure difference across the ejector. In the low entrainment region, the increased suction flow pressure led to an increase in the pressure difference. In the high entrainment region, the pressure difference was inversely proportional to the suction pressure. The effects of nozzle position () were also analyzed and for , the decreased suction chamber volume led to a large pressure drop with the small increase in the suction mass flow rate. For >, the increased disturbed the primary nozzle flow and thus an increase in the primary nozzle flow increased the pressure lifting effect. In contrast, the increased suction mass flow rate decreased the pressure difference. When the nozzle outlet was located at the mixing part entrance (

Analytical Study on the Performance Characteristics of an Instant Cooling Type Water Purifier with the Design Parameters of the Cooling Tank

L_n

Judging Dynamic Co-Existence with Smartphone Magnetometer Traces

The objective of this study is to analyze the effect on the energy consumption of an instant cooling type water purifier by the design parameters of the cooling tank. Initially, the simulation program was developed and verified. The simulation results showed that the energy consumption was reduced by replacing the shape of the cooling tank from a rectangular to a cube, increasing the evaporator length, decreasing the volume of the cooling tank, and increasing the performance of the insulator. The order of the effect magnitude on the energy consumption was as follows; volume of the cooling tank, conductivity and thickness of the insulator, shape of the cooling tank, length of the evaporator, and length of the water tube.

Experimental Study on the Performance Characteristics of a Vapour Compression Refrigeration Cycle using an Ejector

Smartphone magnetometer traces can be used to check if the owners moved in proximity. Using time-lagged cross-correlation of the traces, a fine-resolution judgement can be made within a few meters in any formation. The technique works indoors and outdoors, with no communication infrastructure, with less power and higher resolution than GPS, and with less privacy violation than beaconing. Research and practice on human interactions, such as epidemiology and sociology that need fine contact tracing between complete strangers, can harness the technique.

Simulation-based optimization of an integrated daylighting and HVAC system using the design of experiments method

Extended Abstract Recently, it is desired to reduce power usage for air-conditioning in public buildings. Extensive studies have been carried out to enhance energy efficiency of a refrigeration cycle. Generally, a conventional vapour compression refrigeration cycle uses capillary, TXV, or EEV as an expansion device. The expansion process through these devices is assumed to be an isenthalpic process. Along the process, energy loss occurs due to friction and swirl motion of the flow. In order to recover the potential kinetic energy in the expansion process, various possible methods of the expansion process have been proposed. An ejector, which is a possible replacement of conventional expansion devices such as a capillary tube and thermostatic expansion valve, has been proposed to save energy during the expansion process in the refrigeration cycle. The ejector is designed to recover the throttling energy loss (Mahesh and Valiya, 1999), which may lead to an isentropic process. The objective of this study is to investigate the performance characteristics of an ejector designed for a vapour compression cycle. The performance of the vapour compression cycle using the ejector was measured by varying operating conditions and ejector geometries. The compressor is a reciprocating type with a variable speed inverter ranging from 25 Hz to 45 Hz by an inverter driver and a cylinder volume of 15*cm3 per revolution. The double tube type heat exchanger was used condenser and a heater was used as an evaporator. This study mainly discussed pressure lifting ratio in terms of entrainment ratio. The pressure lifting ratio means the ratio of the exit pressure to the suction pressure, and the entrainment ratio indicates the mass flow rate ratio of the secondary to the total flow. The pressure lifting ratio and total mass flow rate decreased with the increase in the entrainment ratio due to the decreased effect of the primary nozzle and the decreased compressor suction pressure. The pressure lifting ratio and total mass flow rate increased with the increase in the compressor speed due to the accelerated motive flow with the compressor speed. At the low entrainment ratio, the pressure lifting ratio of smaller mixing section diameter was higher than that of larger mixing section diameter. At the high entrainment ratio, the pressure lifting ratio of larger mixing section diameter was higher than that of smaller mixing section diameter.