Physics, 19.10.2019 05:10 carmenala2
Standards for firewalls may be based on their thermal response to a prescribed radiant heat flux. consider a 0.25-m-thick concrete wall ( 2300 kg/m^3, 880 j/kg·k, 1.4 w/m·k), which is at an initial temperature of 25°c and irradiated at one surface by lamps that provide a uniform heat flux of 0.75·104 w/m^2. the absorptivity of the surface to the irradiation is 1.0. if building code requirements dictate that the temperatures of the irradiated and back surfaces must not exceed 325°c and 25°c, respectively, after 30 min of heating, will the requirements be met?
Answers: 3
![T( 0, 30) = 25 + \frac{2(.75\times 10^4)[\frac{(6.92\times 10^{-7} \times 1800}{\pi}]^{0.5}}{1.4} exp (\frac{-0^2}{4(6.92\times 10^{-7} \times 1800)} - \frac{(0.7\times 10^{4} 0}{k} erfc(0)](/tpl/images/0333/5681/be036.png)
![T(0.25, 30) = 25 + 213.34 [exp (\frac{0.25^2}{4\times 6.92\times 10^{-7} \times 1800})] - \frac{0.75\times 10^4(0.25)}{1.4} erfc(\frac{0.25}{2\sqrt{6.92\times 10^{-7} \times 1800}})](/tpl/images/0333/5681/b4156.png)
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