Thermal performance of TAPS heat pipes with non condensable gas blockage

Over 124,300 heat pipes were installed in vertical support members on the Trans-Alaska Pipeline System. During infrared, IR, surveys in the early 1980's it was observed that cold topping was occurring on some of these heat pipes. The cold topping was due to an accumulation of non-condensable gases, a by-product of corrosion or chemical dissociation of anhydrous ammonia, in the problem heat pipes. Alyeska Pipeline Service Company under took an experimental program, beginning in the fall of 2000, to measure the heat transfer performance of NCG blocked heat pipes. Results of this test program are presented and discussed showing the reduction in heat transfer performance of the heat pipes as a function of hydrogen blockage levels. Infrared images are also presented showing the increase in cold topping as the amount of hydrogen in the heat pipe is increased. These IR images are correlated with the degradation in heat transfer performance. A thermodynamic analysis is also presented showing the relationship between the mass of hydrogen within the heat pipe and apparent blockage as a function of evaporator and condenser temperatures.