Determination of wall decay times by use of a polynomial equation

作者：Karmele Urbikain M; Davies Morris G

来源：International Journal of Heat and Mass Transfer, 2010, 53(19-20): 3692-3701.

DOI：10.1016/j.ijheatmasstransfer.2010.04.019

• Decay times
• Polynomial equations
• Response factors

The determination of the thermal decay times of the wall of a building is an essential step in calculating the wall's thermal transfer coefficients. The series of decay times z(j) is normally found by varying time z and searching for zeros of e(12). one of the four elements of the wall transmission matrix. It is demonstrated here that they can be efficiently found by expressing e(12) as a polynomial as a function of time z and then solving the polynomial for e(12) = 0. The method is illustrated by wall examples whose decay times are known by other means. A simple procedure is demonstrated to check whether any solutions have been missed. The article summarises an existing procedure to check for missing roots of e(12) by also finding solutions to e(11) = 0 and in an appendix shows the structure of the solutions which are found when all four values of e(ik) of the transmission matrix are set equal to zero.

• 出版日期2010-9