MrRogers1987
Aerospace
I am working on designing a thermal control system for an array of telescopes that need to be kept at very cold temperatures, and within a very tight tolerance. Constant conductance heat pipes are being used to bus waste heat from the telescope detectors to a deep space radiator. Each detector has an interface pad on the evaporator of the heat pipe loop.
A recent requirement change now has it so that 1 telescope in the array needs to be kept much colder than the rest. Notionally the plan is to use a TEC on the single telescope that needs to be kept colder. It will interface with the same heat pipe evaporator as the other units, and it's hot-side reject temperature will be similar to the temperature the other units needs to be maintained at. So the desire is to have the evaporator operating at the same temperature, but more heat will be input and a larger radiator will be used at the condenser to compensate.
I am not very familiar with detailed heat pipe design other than understanding the underlying principles of the two-phase capillary flow. I am concerned there could potentially be an issue though, since the heat flux into the heat pipe evaporator will now be highly non-uniform down its length. Instead of having ~1W coming in at each interface there will now be close to 4W at one of the interfaces, and ~1 at the rest. Will this lead to any undesirable temperature gradients within the evaporator, or irregular flow rates? Or potentially some other issues that would bring operation out of ideal conditions?
A recent requirement change now has it so that 1 telescope in the array needs to be kept much colder than the rest. Notionally the plan is to use a TEC on the single telescope that needs to be kept colder. It will interface with the same heat pipe evaporator as the other units, and it's hot-side reject temperature will be similar to the temperature the other units needs to be maintained at. So the desire is to have the evaporator operating at the same temperature, but more heat will be input and a larger radiator will be used at the condenser to compensate.
I am not very familiar with detailed heat pipe design other than understanding the underlying principles of the two-phase capillary flow. I am concerned there could potentially be an issue though, since the heat flux into the heat pipe evaporator will now be highly non-uniform down its length. Instead of having ~1W coming in at each interface there will now be close to 4W at one of the interfaces, and ~1 at the rest. Will this lead to any undesirable temperature gradients within the evaporator, or irregular flow rates? Or potentially some other issues that would bring operation out of ideal conditions?