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If I have the following data (I have updated the data):

  data={{{60, 1852.94}, {65, 178.035}, {70, 7.97143}, {75, 48.9479}, {80, 
  133.561}, {85, 8.65079}, {87, 1.78915}}

How can I fit it to the following equation?

eq = 1/((x*c1)/((Exp[B1/(x - T0)])^0.75)*(1 - Exp[((Tm - x)*c2)/Tm^2])) /. {T0 -> 259.246,B1 -> 2595.89, Tm -> 170 + 273.15}

I am trying the following:

  fun[x_] = NonlinearModelFit[data,eq, {c1, c2}, x] // Normal (*c1=1.07571*10^11, c2=1.67014*10^7*)

Which gives me an erroneous c1 and c2 of c1=1.07571*10^11 & c2=1.67014*10^7. When I do it in excel it gives me a c1 of 313634 and a c2 of -8434.47 which fits the data relative well. Why mathematica is not fitting the data or finding the correct c1 and c2 values?

If I have the following data (I have updated the data):

  data={{{60, 1852.94}, {65, 178.035}, {70, 7.97143}, {75, 48.9479}, {80, 
  133.561}, {85, 8.65079}, {87, 1.78915}}

How can I fit it to the following equation?

eq = 1/((x*c1)/((Exp[B1/(x - T0)])^0.75)*(1 - Exp[((Tm - x)*c2)/Tm^2])) /. {T0 -> 259.246,B1 -> 2595.89, Tm -> 88.2 + 273.15}

I am trying the following:

  fun[x_] = NonlinearModelFit[data,eq, {c1, c2}, x] // Normal (*c1=732975, c2=2.65721*10^6*)

Which gives me an erroneous c1 and c2 of c1=732975 & c2=2.65721*10^6. When I do it in excel it gives me a c1 of -65514626.34 and a c2 of 68.4 which fits the data relative well. Why mathematica is not fitting the data or finding the correct c1 and c2 values?

If I have the following data:

data={{333.15, 3.26786}, {338.15, 2.2505}, {343.15, 0.901536}, {348.15, 1.68973}, {353.15, 2.12568}, {358.15, 0.937056}, {360.15, 0.252647}}

How can I fit it to the following equation?

eq = 1/((x*c1)/((Exp[B1/(x - T0)])^0.75)*(1 - Exp[((Tm - x)*c2)/Tm^2])) /. {T0 -> 259.246,B1 -> 2595.89, Tm -> 170 + 273.15}

I am trying the following:

  fun[x_] = NonlinearModelFit[data,eq, {c1, c2}, x] // Normal (*c1=1.07571*10^11, c2=1.67014*10^7*)

Which gives me an erroneous c1 and c2 of c1=1.07571*10^11 & c2=1.67014*10^7. When I do it in excel it gives me a c1 of 313634 and a c2 of -8434.47 which fits the data relative well. Why mathematica is not fitting the data or finding the correct c1 and c2 values?

If I have the following data (I have updated the data):

  data={{{60, 1852.94}, {65, 178.035}, {70, 7.97143}, {75, 48.9479}, {80, 
  133.561}, {85, 8.65079}, {87, 1.78915}}

How can I fit it to the following equation?

eq = 1/((x*c1)/((Exp[B1/(x - T0)])^0.75)*(1 - Exp[((Tm - x)*c2)/Tm^2])) /. {T0 -> 259.246,B1 -> 2595.89, Tm -> 170 + 273.15}

I am trying the following:

  fun[x_] = NonlinearModelFit[data,eq, {c1, c2}, x] // Normal (*c1=1.07571*10^11, c2=1.67014*10^7*)

Which gives me an erroneous c1 and c2 of c1=1.07571*10^11 & c2=1.67014*10^7. When I do it in excel it gives me a c1 of 313634 and a c2 of -8434.47 which fits the data relative well. Why mathematica is not fitting the data or finding the correct c1 and c2 values?