关于latex编译问题

我写好了一个tex文件，编译的时候总是出错，请教高手帮忙。
overfull\hbox(25.14069pt too wide)in paragraph at lines 199-203
\OT1/txr/m/n/12 ing
overfull\hbox(39.34868pt too wide)in paragraph at lines 199-203
\OT1/txr/m/n/12 tower
latex warning:command\t invalid in math mode on input line 228.
(c:\ctex\texmf\tex\latex\txfonts\omltxr.fd)
latex warning:command\t invalid in math mode on input line 228.
!missing $ inserted.
(inserted text)
源代码是In order to describe the heat and mass transfer performance of wet
cooling tower, the output layer has six nodes involved in this BP
model, including tower, the output layer has six nodes involved in
this BP model, including cooling temperature difference $\Delta t$

\end{multicols}

, air gravity wind velocity $g_{air} $

, evaporative loss proportion ${Q_L } \mathord{\left/ {\vphantom {{Q_L }
{Q_W }}} \right. \kern-\nulldelimiterspace} {Q_W }$

, the heat transfer coefficient $\alpha _v $

, mass transfer coefficient $\beta _{xv} $

\end{multicols}

, and cooling efficiency $\eta $

. The input layer has four nodes, including relative humidity of
inlet air $\Phi _{1} $

, circulating water inlet temperature $\t _{1} $

文档第 228 行，命令 \t 要改为 $\t$.