Radiative Heat Transfer Coefficient in Heated Room : Part 2-Approximate Method for Estimation of MeanRadiative Heat Transfer Coefficient

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  • 熱負荷計算における室内ふく射熱伝達率に関する基本的検討 : 第2報-平均ふく射熱伝達率の簡略的推定法および非定常熱負荷計算法の検討
  • 熱負荷計算における室内ふく射熱伝達率に関する基本的検討-2-平均ふく射熱伝達率の簡略的推定法および非定常熱負荷計算法の検討
  • ネツ フカ ケイサン ニ オケル シツナイ フクシャネツ デンタツリツ ニ カ

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In the previous paper of this series, it was shown that the value conventionally used of the mean radiative heat transfer coefficient makes serious errors for the estimation of the heat losses from a heated room under certain conditions. However, this calculation algorithm is widely used in many calculation program. Therefore, if a simple approximate method for the estimation of the proper value of the mean radiative heat transfer coefficients are found, that is very useful. In this paper, an approximate method to estimate the proper value of the mean radiative heat transfer coefficient is proposed. This method is composed of the following processes: firstly the objective room is approximated as a simple room composed of only 2 surfaces, then the mean radiative heat transfer coefficient is estimated for the simplified room from the exact solution which was discussed in the previous paper. Regarding to this method, the division method of n-surfaces into two groups and the averaging method of properties of the walls in each group are discussed. In this method a proper value of the mean radiative heat transfer coefficient can be estimated as the solution of a quardratic equation. By the approximate method mentioned above, the approximate value of the exact mean radiative heat transfer coefficient for warm air heating and unheated room without ventilation can be estimated. However, for radiative heating with and without ventilation, this approximate method can not be recommended because it makes some errors under certain conditions. Moreover, a calculation method for unsteady thermal load of the heated room are discussed. This method uses the constant mean radiative heat transfer coefficient throughout the calculation period, which is obtained by using the mean weather data under steady state condition. Based on many calculations of the unsteady heat losses under various conditions, it is concluded that this method has sufficient accuracy for the estimation of the unsteady thermal losses.

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