How can solve this error: Output 'Taout' declared with unit expression that contains an affine unit: 'degC'. Affine units are not allowed when declaring members of this type.

I am trying to model a Tablet coater thermodynamic model to account for the change in thermodynamic properties with temperature of moist air and thermal liquid (water). For this, I want to make a costumized block which will solve the balanced equation relating inlet temperature and exhaust temp. i.e., Taout = (Mai*Cpa*Tai+Xw*Mcoat*Cpw*Tcoat-Xw*Mcoat*Hlv+Xorg*Mcoat*Cporg*Tcoat-Xorg*Mcoat*Hvorg+HLF*Trt)/(Mai*Cpa+Xw*Mcoat*Cpw+Xorg*Mcoat*Cporg +HLF).

when I applied the code to an unspecified component block in simscape, above mentioned error occured. how can I solve this.

component Tablet_coater
% This is a thermodynamic model of tablet film coater
% which gives the relationship between inlet temperature and exhaust 
%temperature


parameters
   % Add parameters here
    HLF = { 150 , 'kJ/s*K' }; % Heat Loss Factor 
    Trt = {298  , 'degC'}; % Ambient temperature 
end

nodes
    b = foundation.moist_air.moist_air; % b:left
    c = foundation.thermal_liquid.thermal_liquid; %c:left
end

outputs
    Taout = { 0 , 'degC'}; %exhaust temperature:right
end
    
variables
    Tin_b = {value={273,'degC'}};
    Tcoat_c = {value={273,'degC'}};
end

variables 
         Mai_b = { 0 , 'g/min' };
         Cpa_b = { 0 , 'kJ/(kg*K)' };
         Xw_c = 0;
         Xorg_c = 0;
         Cporg_c = { 0 , 'kJ/(kg*K)' };
         Cpw_c = {0 , 'kJ/(kg*K)' };
         Mcoat_c = { 0 , 'g/min' };
         Hlv_c = { 0 , 'kJ/kg' };
         Hvorg_c = {0 , 'kJ/s*K' };
end

branches
    Mai_b : b.Mai -> *;
    Cpa_b : b.Cpa -> *;
    Xw_c : c.Xw -> *;
    Xorg_c : c.Xorg -> *;
    Cporg_c : c.Cporg -> *;
    Cpw_c : c.Cpw -> *;
    Mcoat_c : c.Mcoat -> *;
    Hlv_c : c.Hlv -> *;
    Hvorg_c : c.Hvorg -> *;
    
end

equations
   % Add equations here
    
     
    Taout == fcn(Mai,Cpa,Xw,Xorg,Cporg,Cpw,Mcoat,Tcoat,Tai,Hlv,Hvorg);
    
    Taout == (Mai*Cpa*Tai+Xw*Mcoat*Cpw*Tcoat-Xw*Mcoat*Hlv+Xorg*Mcoat*Cporg*Tcoat-Xorg*Mcoat*Hvorg+HLF*Trt)/(Mai*Cpa+Xw*Mcoat*Cpw+Xorg*Mcoat*Cporg +HLF);
end

end

Answer 1

[Yifeng Tang]

Declare temperatue units in K. That's what the error message is saying. The numerical value of the temperature may be overridden either by initial conditions you set or when the solver try to initialize. But it's still a good idea to put a value in the right range.