To my knowledge there were no sublimators on the vehicles themselves, though I could be wrong.
The Apollo CSM ECS did not use a sublimator. It did, however, incorporate an auxiliary chiller in the form of a glycol evaporator. It works according to many of the same principles as a sublimator.
The closed-loop water-glycol coolant cycle was largely self-sustaining, requring only a few watts of electrical power to run its pump. As such it could continue rejecting heat effectively so long as it was provided with electricity. The radiators had a significant margin of heat rejection capacity. In fact, under nominal loads, not all the coolant was even sent to the radiators; some bypassed it and was remixed with the radiator outlet volume. That's to keep some equipment from getting too cold.
During peak heat loads the bypass was closed and all the coolant went through the radiator. During excessive heat loads, the evaporator was activated.
The glycol evaporator passes the water-glycol coolant into an exchanger in a jacket that is vented partially to space vacuum. A valve controls the air pressure in the evaporator jacket. The evaporator does not actually evaporate the glycol, as the name implies. Instead, water from the fuel cells is introduced into the evaporator outer jacket, which is the chamber partially vented to space. At lower pressure the water evaporates more readily. Water vapor escapes to space at a controllable rate through the pressure vent tube. Each unit mass of water that evaporates draws from the water-glycol loop heat equivalent to the heat of vaporization of water, at a rate dictated by the rate of evaporation.
This is very similar to the mechanism used in the suit sublimator. The heat rejection there is through heat of sublimation -- greater per unit mass than the heat of vaporization. And the mechanism of introducing the water to the vacuum is different in the sublimator; through a porous plate into raw vacuum rather than in liquid form through a valve as occurs in the evaporator.
But both transfer the heat from the working fluid into a sacrificial material that is subjected to a heat-consuming state change. Both the evaporator and the sublimator techniques require a supply of water, thus limiting their duty cycle to water on hand. Hence the evaporator was considered only for incidental or emergency use.
Does anyone have a technical description of the apparatus?
Yes, but only in print. Someone else may have a link if that's what you want.
I believe, with this post, that all of IDW's questions have been answered so far.
|