我正在编写一个热交换模拟程序。应该生成的值是T_hot_out = 65，T_cold_out = 35，A = 22.26。
下面是我一直在使用的代码。它打印T_hot_out = 36.9和T_cold_out = 64.32。没有引发错误，所以我对计算错误来自哪里以及如何修复它感到困惑。

#problem 4
import numpy as np

# from text (original design assumptions)
T_cold_out0 =35
T_hot_out0 = 65

# from Table 1
T_hot_in = 160.0
T_cold_in = 20.0
Cp_hot = 5.2
Cp_cold = 2.6
w_hot = 1.0
k = 0.05
l = 0.002

# from problem 2
w_cold = 5.555555
A_design = 22.26

def integrate(f, x0, x1, N):
  h = (x1 - x0) / (N-1)
  xvalues = np.linspace(x0,x1,N)
  yvalues = f(xvalues)
  F = np.zeros(N)
  for i in range (1,N):
      F[i] = h/2 * (yvalues[i-1]+yvalues[i])+F[i-1]
  return xvalues,F
  

def bisection(f, y, x0, x1, eps, max_iter=1000):
  x1_n = x1
  x0_n = x0
  T = (x1+x0) / 2.0
  f_T = f(T)
  for i in range(max_iter):
    T_n = (x0_n+x1_n)/2
    f_T_n = f(T_n)
    error = f_T_n - y
    if abs(error) <= eps:
      break
    elif  error > 0:
      x0_n = T_n
      x1_n = x1_n
    elif error < 0:
      x0_n = x0_n
      x1_n = T_n
  return T_n, error, (abs(error)<=eps)

def h_hot(T_n):
    return 0.9*(1+0.015*(T_n-70))
    
def h_cold(T_n):
    return 3.0*(1+0.02*(T_n-40))
    
def h_overall(T_cold, T_hot):
    return 1/((h_hot(T_hot))**-1 + (h_cold(T_cold))**-1 +(k/l)**-1)
    # equation (2) using h_hot() and h_cold()
    

def T_hot(T_cold, T_hot_out):
    return  T_hot_out + ((Cp_cold*w_cold)/(Cp_hot*w_hot))*(T_cold - T_cold_in) # from problem 3
    
def T_cold_out(T_hot_out):
    return  T_cold_in + (Cp_hot*w_hot)/(Cp_cold*w_cold)*(T_hot_in-T_hot_out) # similar to T_hot()
  
def A(T_hot_out):
    def f2(T_cold):
      return ((Cp_cold*w_cold)/h_overall(T_cold, T_hot(T_cold, T_hot_out)))*(1/(T_hot(T_cold, T_hot_out)-T_cold))  # from equation (9)
    T_cold, area = integrate(f2,T_cold_in,T_cold_out(T_hot_out), 1000)
    return area[-1]
  
T_hot_out, err, success = bisection(A, A_design, T_cold_in, T_hot_in, 0.001, max_iter=1000)
if not success:
    print("Bisection has failed!")
    
print("T_hot_out = {:.2f} (instead of {:.2f})".format(T_hot_out, T_hot_out0))
print("T_cold_out = {:.2f} (instead of {:.2f})".format(T_cold_out(T_hot_out), T_cold_out0))
print("A = {:.2f} (error = {:.4e})".format(A(T_hot_out), A(T_hot_out) - A_design))