refactor: change defaults to guesses in Thermal

Author: SebastianM-C

src/Thermal/HeatTransfer/ideal_components.jl

@@ -24,8 +24,8 @@ Lumped thermal element storing heat
         C, [description = "Heat capacity of element"]
     end
     @variables begin
-        T(t) = 273.15 + 20
-        der_T(t)
+        T(t), [guess = 273.15 + 20]
+        der_T(t), [guess = 0.0]
     end
 
     @equations begin

src/Thermal/utils.jl

@@ -1,6 +1,6 @@
 @connector HeatPort begin
-    T(t) = 273.15 + 20.0
-    Q_flow(t), [connect = Flow]
+    T(t), [guess = 273.15 + 20.0]
+    Q_flow(t), [guess = 0.0, connect = Flow]
 end
 Base.@doc """
     HeatPort(; name, T = 273.15 + 20.0, Q_flow = 0.0)
@@ -35,8 +35,8 @@ flow rate through the element from `port_a` to `port_b`, `Q_flow`.
         port_b = HeatPort()
     end
     @variables begin
-        dT(t)
-        Q_flow(t)
+        dT(t), [guess = 0.0]
+        Q_flow(t), [guess = 0.0]
     end
     @equations begin
         dT ~ port_a.T - port_b.T
@@ -69,8 +69,8 @@ flow rate through the element from `solid` to `fluid`, `Q_flow`.
         fluid = HeatPort()
     end
     @variables begin
-        dT(t)
-        Q_flow(t)
+        dT(t), [guess = 0.0]
+        Q_flow(t), [guess = 0.0]
     end
     @equations begin
         dT ~ solid.T - fluid.T