Effect of Vapor-dam Treatment and End-coating Treatment on the air Circulating oven Drying Characteristics of Green Stocks for Korean Traditional Double-headed Drum

수증기댐처리 및 엔드코팅처리가 장고용 초갈이재의 송풍오븐건조 특성에 미치는 영향

This study was conducted to investigate the effects of End-coating (CO) treatment and Vapor-dam (V) treatment on the air circulating oven drying characteristics of green stock (Paulownia tomentosa) for drum. The reduction of the weight of specimens was greatly displayed in order of control (C-NC) treatment, End-coating (C-CO) treatment, Vapor-dam (V-NC) treatment and Vapor-dam/End-coating (V-CO) treatment after the beginning of drying. The V-CO treated specimen showed smoother temperature gradient compared with the V-NC treated specimen throughout whole drying stage and there was little temperature gradient between the inner and outer part of the cylindrical stock. The C-CO treated specimen showed higher value of vapor pressure in both the inner and outer part of the cylindrical stock until the middle stage of drying, while after the middle stage of drying only the inner part of the cylindrical stock presented higher value compared with the C-NC treated specimen. The distribution of the absolute vapor pressure of the V-CO treated specimen was similar to that of the V-NC treated specimen during the initial stage of drying. However, the former showed a large distribution in order of the hollow, the outer part, the inner part of the cylindrical stock after the initial stage of drying, which was entirely different model of distribution from that of the V-NC treated specimen. Surface checks and ring failures were not observed for all of the specimens, while end checks were severely occurred for the C-NC treated specimen and the V-NC treated specimen.

본 연구에서는 수증기댐처리 또는 횡단면 코팅처리 등이 오동나무 장고용 초갈이재의 송풍오븐건조 특성에 미치는 영향을 구명코저하였다. 건조개시 직후의 중량감소량은 무처리(C-NC treatment), 엔드코팅처리(C-CO treatment), 수증기댐처리(V-NC treatment), 수증기댐-엔드코팅처리(V-CO treatment)재의 순으로 크게 나타났다. V-CO처리재는 V-NC처리재와 비교하여 전(全)건조기간에 걸쳐 더 완만한 온도경사를 보였으며 내층과 외층간에 온도경사가 거의 존재하지 않았다. C-CO처리재의 경우 C-NC처리재와 비교하여 건조중기까지는 외층과 내층의 수증기압 모두가, 그리고 건조중기 이후에는 내층의 수증기압이 더 높게 나타났다. V-CO처리재의 경우 건조초기에는 V-NC처리재와 유사한 분포를 보였으나, 건조초기 이후 통공, 외층, 내층의 순으로 절대수증기압이 큰 분포를 보이면서 V-NC처리재와는 전혀 다른 분포모형이 관찰되었다. 재면할렬과 윤할은 모든 처리재에서 전혀 발생하지 않았으나 엔드코팅을 실시하지 않은 C-NC와 V-NC에서는 횡단면할렬이 심하게 발생하였다.