Two long concentric cylinders exchange heat by radiation. The inner cylinder having a diameter of 10 cm has T1 = 1000 K and ε1=0.65 while the outer cylinder having a diameter of 20 cm has T2 = 500 K and ε2=0.40. Calculate the net heat transfer between the two cylinders per unit length

Apiping systems consists of 6 m of 6-std type k and 12 m of 4-std type k, both drawn copper tubing. the system conveys ethylene glycol at a rate of 0.013 m3/s. the pressure drop across the system is to be calculated. there are two 90° elbows in the 6-in pipe, a reduction from the 6-in pipe to the 4-in pipe and four 90° elbows in the 4-in pipe. all fittings are soldered (same as flanged) and regular. the inlet and outlet of the system are at the same height.