[Sumeet Anand]

Hello everyone,
I am simulating the melting and solidification behavior of phase change material (PCM) in the heat pipe for subsequent time cycles. Cold fluid flows in the inner pipe while the PCM is stored in the annulus region of the heat pipe. During the charging process, the flux boundary condition at the outer surface of the heat pipe is applied. In contrast, during the discharging process, the convection boundary condition is given at the outer surface of the heat pipe. For this, I am writing the scheme command so that when the PCM completely melts during the charging process, the convection boundary condition automatically applies. Further, once it completely solidifies during the discharging process, the heat flux boundary condition activates again, and similarly, the convection boundary condition activates when PCM completely melts. So, this melting and solidification process continues for different time periods. The scheme command is written below based on the PCM solidus and liquids temperature, as the melting and solidification time is not known.

(if(ti-menu-load-string (format #f "report/volume-integrals/volume-avg pcm_domain () temperature no"))310 [K])
(
(ti-menu-load-string "define/boundary-conditions/wall outer_glass_cover 0 no 0 no yes heat-flux no 1000 no no 0 no 1)
)
(if(ti-menu-load-string (format #f "report/volume-integrals/volume-avg pcm_domain () temperature no"))315 [K])
(
(ti-menu-load-string "define/boundary-conditions/wall outer_glass_cover 0 no 0 no yes convection no 10 no 300 no no 0 no 1)
)

Where 310 K & 315 K are the PCM solidus and liquids temperature, respectively.
However, an error is showing while executing the scheme command, and the same is attached with this message. Also, in the IF statement, I have also not considered the temperature unit in a square bracket, but the error remains the same.
Can anyone please suggest how to resolve this error.