Hello guys, I'm stuck with this question for some time. For my equation, I need to use WolframAlpha for my data. Firstly, I fix my initial water temperature as 500 Kelvin. Eg:

Twater = 300
Cwater = QuantityMagnitude[
  ThermodynamicData["Water", 
   "ThermalConductivity", {"Temperature" -> 
     Quantity[Twater, "Kelvins"]}]]

With Cwater determined, I can implement the next 2 functions

Dwater = (5 Cwater)/\[Pi]
Ewater = Dwater^3 + 2 Cwater

Then by using ParametricNDSolveValue, I can determine the value of Z

ClassicalRungeKuttaCoefficients[4, prec_] := 
  With[{amat = {{1/2}, {0, 1/2}, {0, 0, 1}}, 
    bvec = {1/6, 1/3, 1/3, 1/6}, cvec = {1/2, 1/2, 1}}, 
   N[{amat, bvec, cvec}, prec]];

f = ParametricNDSolveValue[{Derivative[1][y][x] == 
     Piecewise[{{(y[x] + x^3 + 3 z - 120*Ewater), 0 <= x <= 1},
       {(y[x] + x^2 + 2 z), 1 <= x <= 2},
       {(y[x] + x + z), 2 <= x <= 3}}],
    y[0] == 0},
   y[3.],
   {x, 0., 3.},
   z,
   Method -> {"ExplicitRungeKutta", "DifferenceOrder" -> 4, 
     "Coefficients" -> ClassicalRungeKuttaCoefficients}, 
   StartingStepSize -> 1/10];

point = {z /. FindRoot[f[z] == 100., {z, 1}, Evaluated -> False], 
   100.};

FindRoot[f[z] == 100., {z, 1}, Evaluated -> False]

Lastly, to find the new temperature of water

Tnew = 170 + 1.89*z /. 
  FindRoot[f[z] == 100., {z, 1}, Evaluated -> False]

I wanted to repeat Twater with Tnew until Twater=Tnew->True and the loop stop. I need to start Twater with a value, (only to replace Twater=Tnew after the first equation and keep press shift+enter repeatedly)

I've tried some Do Loop or For Loop and even FixedPoint but still don't know how to combine multiple functions/equations into 1 loop.... I apologize because I've been asking this question a few times, or maybe some of you have answered me in some way, but I still did not understand how to do this. Thank you very much for your time.