Heat Pump Evaporator
Cold-Side Evaporator Heat Exchanger
The cold-side evaporator heat exchanger is a thermal control component constructed from aluminum cold plates, copper tubing, or finned assemblies that extracts waste heat from equipment zones by evaporating refrigerant. Within the lunar Active Thermal Control System, the unit maintains target setpoints and uses superheat control to ensure complete vaporization before refrigerant reaches the compressor. Implementation is constrained by the lunar operating environment: in external vacuum zones, the evaporator must couple to equipment solely through conductive cold plates, whereas pressurized habitats utilize forced air over coils. Operational controls must prevent evaporator freeze-up during low-load conditions and manage frost formation inside pressurized volumes.
Evaporator absorbing heat from cooled zone transferring it to refrigerant
Purpose
Extract thermal energy from equipment zones maintaining target temperature setpoints
Context
Child of L2-TCS-HPMP in the Active Thermal Control System
Principles
- ▸Evaporation of refrigerant absorbs latent heat providing efficient cooling
- ▸Fin-tube or plate evaporator geometry maximizes contact with cooled surface/air
- ▸Superheat control ensures fully vaporized refrigerant exits evaporator protecting compressor
- ▸Multiple evaporator zones can be served with individual expansion valves
Typical implementations
- ▸ISS Common Cabin Air Assembly heat exchangers
- ▸Space-rated cold plate evaporators
- ▸Fan-coil evaporator units for pressurized habitats
Lunar considerations
- ▸In vacuum sections, evaporator couples to equipment via conduction only (cold plates)
- ▸In pressurized sections, forced air over evaporator coils possible
- ▸Frost formation not a concern in vacuum but possible in pressurized zones
- ▸Must avoid evaporator freeze-up during low-load conditions
Specifications
Functional
| primary function | Evaporator absorbing heat from cooled zone transferring it to refrigerant |
Physical
| materials | Aluminum cold plates, Copper tubing, Aluminum fins |
Interfaces
Provides
- Active cooling of equipment thermal zones
Requires
- Temperature setpoint and valve position commands
Cite this entry
Lunar Ark Codex. "Heat Pump Evaporator" (L3-TCS-HPMP-EVAP). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-TCS-HPMP-EVAP
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.