fzero error using a root
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Q_i = S*tau*e_paint*A_pt;
Q_rad = @(T_pt)(e_paint*sigma*A_pt*(T_pt^4 - T_sun^4));
Q_conv = @(T_pt, T_air)((1.68*(T_pt-T_air)^(1/2))*A_pt*(T_pt-T_air));
Q_heat_plate = @(T_pt, T_pt_LAST)((m_p*c_a+m_t*c_c)*(T_pt -T_pt_LAST));
Q_water = @(T_w,T_pt)(h_w*A_inside*(T_pt - T_w));
solver_T_pt = @(T_pt)(Q_rad(T_pt) + Q_conv(T_pt, T_air) + Q_heat_plate(T_pt, T_pt_LAST) + Q_water(T_water_average, T_pt) - Q_i);
T_pt_num = fzero(solver_T_pt, 293); %[K] temperature aluminiumplate and tube
q_heat_air = Q_conv(T_pt_num, T_air); %Determining the energy to the air through convection
T_air_num = (q_heat_air)/(m_air*c_air_p) + T_air; %[K] New Temperature of air
I am using a fzero function here to solve this problem, however in line 3 an error eccors when using ^1/2. When I use ^2 for example the function works fine so the fzero probably goes bad on the root but how do I fix this?
回答（1 个）
madhan ravi
2020-6-4
0 个投票
.* .^
5 个评论
Tim Pijnacker
2020-6-4
编辑：Tim Pijnacker
2020-6-4
madhan ravi
2020-6-4
编辑：madhan ravi
2020-6-4
Did you say what error occurred? Did you define the variables? Did you think others could run the code without providing the datas? fzero(...) expects numeric input and not symbolic.
doc fzero
Tim Pijnacker
2020-6-4
Steven Lord
2020-6-4
That doesn't look like the whole error message. Can you show us all the text displayed in red when you run your code? There should be something displayed before the "Error in plate_v2" line.
Tim Pijnacker
2020-6-4
You are right! I actually missed that bit thanks. Could the problem be that T_pt and T_air are to close at the start which makes it infinitely small, or should this then also be a problem when squaring it?
(For a bit more background on the code, it is a tempertature model for a solar collector. At the start T_pt and T_air are both room temperature and after that they both rise due to radiation of the sun but T_pt rises faster then T_air)
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