A biorefinery uses a central steam plant and a steam loop to supply heat to key operations (e.g. hydrolysis and fermentations). Currently, the steam pipes are insulated with 2 cm thick insulation with an R value of 0.5 m2-K/W, but the plant engineer is concerned about efficiency and is considering moving to 3 cm thick insulation with an R value of 1 m2-K/W. The length of the steam loop is 500 m, ID is 8 cm. The steam exits the boiler at 1 kg/sec at 150°C, and the outside air temperature in winter is 5°C. Assume for this problem that the steam pressure is 0.2 MPa.
Questions:
a) What is the temperature of the steam reaching the fermenter?
b) What are the cumulative heat losses along this stretch of pipe?
c) How does moving to R=1 insulation that is 3 cm thick change these numbers?
d) What percent of heat supply is lost to the environment when using the R=0.5 vs. R=1 insulation?
e) Another means of reducing heat losses is to change the pipe diameter while keeping the R=0.5 insulation – at what pipe diameter is the heat loss equal to the 8 cm pipe with R=1?
DO NOT SOLVE: Just give equations that need to be used
