Ondol is a traditional heating system in Korea. After new building type, apartment was introduced from western world around 1960, there have been dynamic changes in heating system in apartment. At first, designers supposed that apartment should match to the stand-up-living-style and the radiator system regardless traditional life style. Dwellers, however, didn't accept such a heating system even though the increase of the use of standing type furnitures such as bed, sofa, table, sink etc. Nowadays, Ondol is facilitated to the entire of the home even to the living room and dining/kitchen which radiator system was supposed to be accepted by designers. This try and error process shows that heating system is not only the physical facility itself, but also the cultural element reflecting the properties of way of life. And also it prove that one culture can not substitute the other culture, but merely conflict, mediated each other.

Gudul has been used since it was invented, and will be used continuously. But recently, we used rarely. One of the this reason is unequally floor temperature in Gudle because the distribution of heating air is not constant. So flow field in Gudul must be known for uniform temperature in floor. Recently, many fluid engineer have been performed the numerical analysis for the understanding of thermal and flow field based on the development of CFD(Computational Fluid Dynamics). In this paper, to find out the variation of temporal temperature in floor of traditional Gudle, we have performed numerical analysis. Initial temperature in floor is 20 t:' after 880 seconds later, maximum temperature become 2i.Oi t:'. ihour later, maximum temperature in floor become 34.5 t:' because continuously increase from 880 seconds.

As we all know Ondol has been the most efficient and comfortable heating system of the rural residence in the Northeast of China for hundreds of years. But recently, through field survey, it was found that some country people replace the Ondol with homemade heating blindly. The result of this replacement is that heating effect of residence in winter is worse. And at the same time, it aggravates air pollution and increases heating payout. According to our real situation of energy sources reserve, environmental pollution and economic income of rural people, it is not only inpractical but also unreasonable, that in the northeast of China Ondol is replaced by homemade heating completely in winter. Ondol has its unique heating and hygienic efficacy. And it stands for cultural tradition and life custom of the country's cold areas. So we should improve Ondol combining resident structure and material. And it can make the Ondol system flourish with vigor and promote sustainable development of the country's traditional Ondol residence.

A Zikhwa-Gorae(Directfire-Firetunnel) Gudle is composed in the order of Agungi(Fireplace- gate), Agungi-hureongi(Fireplace-in), Bunengki(Fireridge), Gudle-Gaezari(Gudle-Deepplace), Gorae(Firetunnel), Gorae-Gaezari(Firetunnel-Deepplace), Gulduk(Holebank) and Gusae(Chimney ). The detail drawings of a Gudul(traditional Ondol) are showed. Four kinds of the Gudle are Godeon-Gorae(Straight-Firetunnel) Gudle, Doedon-Gorae(Return-Firetunnel) Gudle and Heutn -Gorae(Scatter-Firetunnel) Gudle.