The length to the inside diameter effect of steam pipe on the performance of a closed-loop boiler under vacuum condition

Abstract

A study on the effect of steam pipe size on the performance of closed–loop boiler under vacuum condition, to determine the relationship of heat load to pipe size affecting the saturation temperature and overall performance of the boiler. The Boiler is made of cylindrical copper pipes with a capacity of 3,000 cc. Distilled water is filling as the working fluid in the amount of 10% (300 cc) of capacity volume. The water is boiled by an electric heater of 530, 1085, 1640, 2210, 2780 and 3350W. The steam pipes for tested are made of type L copper pipes of 7 sizes in accordance with ASTM B88 STD with a test section length of 400 mm. Length to the inside diameter (L/d) of pipe is a ratio of 83, 50, 37, 29, 24, 20 and 17. The boiler was under vacuum initial condition in experimental, water cooled condenser with constant temperature of 25 °C and constant flow rate of 1 kg/min. The results showed that the L/d value had an effect on the boiler performance when heated at a constant volume, the saturation temperature increased with the L/d was greater than 20. The total thermal resistance was also decreased with a decrease in L/d. The lowest total thermal resistance of 0.0343 °C/W when the heat load content is 2780W with L/d of 17.