The following question is based on a true story, which occured during IESD surveys of factories.

A textile printing factory requires steam supplied from a boiler house. The steam pipe crosses the carpark and is essentially uninsulated, covered by a layer of paint (and rust). The parts to this question will determine what savings would be made by insulating the outdoor length of the steam pipe.

Shutdown , days	10
hours/day steam , hours	22
steam temp , deg.C	195
ambient temp , deg.C	13
heat transfer coefficient (ho)	6.9
Inside radius (ri)	0.051
paint thickness , m	0.001
total radius (uninsulated) (r), m	0.051
Total radius (insulated) (r), m	0.1
k (uninsulated)	80
k (insulated)	0.06
gas cost (/kWh) ,	0.08
pipe length, m	7

Pi = 3.14159

Assume gas cost takes into account boiler efficiency

This question is broken up into several parts and marks will be awarded for correct answers for each.

A. What is the heat loss per metre for the uninsulated pipe in watts? [a]

B. What is the uninsulated heat loss for the total pipe length in kWh per hour? [b]

C. Assuming a shutdown over Christmas during a 365 day year, the site (and the steam supply) runs for the stated number of hours per day. How many hours per year is steam supplied? [c]

D. What therefore is the cost per year of feeding steam through the uninsulated pipe? [d]

E. What is the heat loss per metre for the insulated pipe in watts? [e]

F. What is the insulated heat loss for the total pipe length in kWh per hour? [f]

G. What therefore is the cost () per year of feeding steam through the insulated pipe? [g]

H. How much money is saved () per year after insulating the pipe? [h]

Answer rating: 100% (QA)

To solve the problem we will calculate each part as follows A Heat loss per meter for the uninsulate... View the full answer