Two parallel pipes, each having a diameter of 5 cm, carry steam at 120C and chilled water

Question:

Two parallel pipes, each having a diameter of 5 cm, carry steam at 120ºC and chilled water at 5ºC, respectively, and are buried in an infinite medium of fiberglass blanket (k = 0.04 W/m· ºC). Plot the heat transfer between the pipes per unit length as a function of the centerline spacing between the pipes.