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Low GWP 혼합 냉매의 열역학 물성치를 위한 상태방정식의 선정
이공훈,김동호,김우경,김진섭,김영,류진우 대한기계학회 2022 大韓機械學會論文集B Vol.46 No.10
Low GWP refrigerants are required to manufacture the refrigeration systems owing to the worldwide global warming issue. The refrigerant replacements for most refrigeration systems have been developed with a GWP value of less than 150. However, the replacement for R410A with a GWP value of less than 150 has not been developed to date. Thus, an attempt has been made to develop the refrigerant replacement as a mixture refrigerant. To develop this refrigerant, the thermodynamic properties must be calculated with the equation of state (EOS) to investigate its performance. In the present study, several types of EOS have been investigated to calculate the thermodynamic properties for pure fluids and mixtures, and the Helmholtz energy explicit EOS showed the best results. 전세계적으로 지구온난화가 급속히 진행되면서 GWP 규제가 진행되고 있고, 냉동기 및 히트펌프에 대한 low GWP 냉매 사용이 당면한 문제가 되고 있다. 대부분의 냉동기에 대한 low GWP(<150) 냉매 후보들이 개발되어 있으나 건물 냉난방용으로 사용하는 히트펌프 냉매 R410A에 대한 low GWP(<150) 냉매 후보는 현재까지 개발되지 않았고, 최근에 이 냉매 후보를 개발하기 위한 연구가 진행되고 있다. 냉매를 개발하기 위해서는 냉매 물질의 개발과 함께 냉매의 열역학 물성치를 평가할 수 있어야 한다. 본 연구에서는 새로운 냉매 개발에 대비하여 순수 냉매 및 혼합 냉매의 물성치를 평가하는데 필요한 여러 가지 상태방정식(EOS: equation of state)들을 조사, 분석하였고, 물성치 계산의 정확도를 보장하기 위해서는 Helmholtz 에너지 상태방정식을 사용하는 것이 적절함을 보였다.
마이크로 열전냉각기의 열성능에 대한 열전소자 두께의 영향
이공훈,김욱중 대한설비공학회 2006 설비공학 논문집 Vol.18 No.3
The three-dimensional numerical analysis has been carried out to figure out the effect of the thermoelectric element thickness on the thermal performance of the thermoelectric micro-cooler. The small-size and column-type thermoelectric cooler is considered. It is known that tellurium compounds currently have the highest cooling performance around the room temperature. Thus, in the present study, Bi2Te3 and Sb2Te3 are selected as the n- andp-type thermoelectric materials, respectively. The thermoelectric leg considered is less than 20 m thick. The thickness of the leg may affect the thermal and electrical transport through the interfaces between the leg and metal conductors. The effect of the thermoelectric element thickness on the thermal performance of the cooler has been investigated with parameters such as the temperature difference, the current, and the cooling power.
이공훈,홍용주,김욱중 대한설비공학회 2006 설비공학 논문집 Vol.18 No.8
Analysis of drying characteristics has been carried out with one-dimensional model in the dryer using the principle of the refraction of radiation. The dryer is composed of hot water tank, plastic film conveyer belt, drying material, etc. The model considers the conduction and radiation within the plastic film and drying material. The film is semitransparent to radiation and the drying material is assumed to be semitransparent or opaque to radiation. The results show that the effect of radiative transfer on the drying rate is relatively large when the thickness of drying material is small and the water temperature is high. When the material is thin, the drying rate due to conduction is also enhanced and the drying time can considerably be reduced.
비직교좌표계에 대한 P-1 근사법 및 유한체적법을 이용한 주유동 중의 원형실린더 주위의 복사열전달 해석
이공훈,이준식,최만수 대한기계학회 1995 대한기계학회논문집 Vol.19 No.3
A study of radiative heat heat transfer has been done in the non-orthogonal coordinate system utilizing the finite volume method and the P.1 approximation. Radiation of absorbing, emitting and scattering media in a concentric annulus has been solved using the non-orthogonal coordinate and the calculations were compared with the existing results. The results obtained from the analysis using the finite volume method are in good agreement with the existing calculations for all optical thicknesses. It was also shown that for only optically thick cases, P-1 approximation can be used in a non-orthogonal coordinate. Convective heat transfer analysis has been carried out to obtain the temperature fields in a cross flow around a circular cylinder and the finite volume method was applied in the non-orthogonal coordinate system to analyze radiative heat transfer. Effects of the optical thickness, the ratio of the surface temperature of the cylinder tot he free stream temperature, and the scattering albedo on radiation have been presented.