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Thermoelectric properties of silicon hexaboride prepared by spark plasma sintering method
KwangBoShim,KyoungHunKim,J.Matsushita,K.Niihara,KeunHoAuh,DaeWoongLee 한양대학교 세라믹연구소 2002 Journal of Ceramic Processing Research Vol.3 No.3
Silicon hexaboride is attractive for various industrial applications because of its high temperature capability, high hardness and excellent electrical conductivity, in particular it is a promising material for use as a thermoelectric semiconductor at high temperature. We have used a spark plasma sintering technique to produce silicon hexaboride ceramics. The Seebeck coefficient, electrical conductivity and thermal conductivity were measured and the effect of additives, phase composition and microstructure on the thermoelectric properties were discussed. The approximate value of Z (figure of merit value) of the SPS specimen reached about 9.6×10-6/K at 1273 K. The thermoelectric properties (Z) of the SPS specimen are improved in comparison with the specimen by hot-pressing. The effect of the addition of lanthanum and boron on thermoelectric properties of SiB6 were also evaluated.
NUMERICAL STUDY OF PRE-VENTILATION EFFECTS ON CABIN TEMPERATURE USING SOLAR SUNROOF
Daewoong Lee,Hoseong Lee 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.6
When a vehicle is parked under the summer sun, to avoid the passenger discomfort caused by high cabin temperature, the performance of forced ventilation, which is called pre-ventilation, using a solar sunroof integrated with a photovoltaic (PV) cell to reduce cabin thermal load is investigated numerically in this study. The vehicle pre-ventilation system is composed of a solar sunroof, DC/DC converter, and air handling system. The indoor thermal load is reduced by the hot cabin air that moves when outside air is supplied to the cabin. The simulation model is established with the component and system model approach using Dymola, and the numerical analysis results are compared with the experimental data. Using the validated model, pre-ventilation performance is analyzed with 40-, 80-, and 120-W PV cells in each solar sunroof system. The results indicate that the 40-W PV cell in the solar sunroof is sufficient for this pre-ventilation application considering cost and cabin thermal comfort performance. Further, the effects on cabin space and DC/DC converter efficiencies were investigated. The analysis results show that cabin volume slightly affected cabin temperature, whereas the efficiency of DC/ DC converter was not significantly affected by cabin temperature reduction.
COOLING AND HEATING PERFORMANCE IMPROVEMENT OF ENHANCED CLIMATE CONTROL SEATS
Daewoong Lee,Eunwoung Lee 한국자동차공학회 2018 International journal of automotive technology Vol.19 No.5
The goal of this research is to investigate the application of low-cost climate control seats (CCSs) using a Heating, Ventilation and Air-conditioning system (HVAC). CCSs are being vigorously developed because demands on passengers’ thermal comfort are increasing recently. Nevertheless, current CCSs−thermo-electric devices (TED) that have been applied for both heating and cooling systems, have been used in limited luxury cars only. HVAC-type CCSs are proper for effective delivery of conditioned air due to thermal comfort and close proximity to passengers. In this study, experimental results show that HVAC-type CCSs have superior cooling performance and slightly worse heating performance than that of TED-type CCSs. In the case of HVAC-type CCSs, compared to TED-type CCSs, airflow volume was increased approximately 3.7−7.3 m3/h and surface temperature of seats was reduced by about 5 °C. And the maximum cool-down performance of HVAC-type CCSs was similar to the Base (Non HVAC-type CCSs). In addition, in passengers’ subjective evaluation, the HVAC-type CCSs, the former recorded twelve minutes to reach the comfort rate five both in cooling and heating test, meanwhile, TED-type CCSs are nineteen minutes and ten minutes each both in the cooling and heating test.
Daewoong Lee,Seung Yong Hwang 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.1
This study investigates the performance of vehicle cabin supplemental cooling and heating systems equipped with a 1 kW thermoelectric module (TEM) heat exchanger. The TEM heat exchanger comprises 96 hermoelectric modules, the heat sink with a louver fin and water cooling jacket, attached on the thermoelectric modules both hot and cold side. The cooling and heating performance experiment was conducted under various conditions, considering parameters such as air flow volume, air inlet temperature, water inlet temperature, water flow rate, and intake voltage to the TEM heat exchanger. The calorimeter experimental results demonstrate that the cooling capacity and coefficient of performance (COP) were 1.63 kW and 1.6, while the heating capacity and COP are 4.44 kW and 4.4, respectively. An air-conditioning system level evaluation was then conducted using system bench apparatus, considering the environmental conditions when vehicles were in use; a rear air-handing unit (AHU) with a 1 kW TEM heat exchanger was employed to determine both cooling and heating performance.