Thermal Control System

The Three Mechanisms of Heat Transfer

• Conduction - The transfer of heat through a solid– Interface Heat Exchangers– Cold plates

• Convection - Transfer through fluids both liquids and gasses

• Radiation - Transfer through vacuum or empty space– Does not need a vacuum to radiate heat– Radiators

System Overview

• Divided into internal and external loops, as well as per module

• Divided into 35 and 62 degree loops– 35 degree loop cools all critical systems– 62 degree loop cools all non-essential systems

• Maintains a comfortable living and working temperature for the station

Internal TCS system• Cold plates, LCA, Pumps, Interface Heat

Exchangers• All systems use water in case of leaking, as

it is non toxic, and conducts heat very well.

Cold Plates

• Aluminum box conducts heat to water piping within

• No power required, all flow is controlled by pump

• Solenoid valve can bypass flow if necessary

Internal Pump

• Circulates water through the cold plates• Powered by EPS power distribuition• Status, Flow rate, Pressure, Temperature,

Voltage, Amperage

Loop Crossover Assembly (LCA)

• Allows both 35 and 62 degree loops to be connected within a given module

• A single pump can only handle approximately 10 cold plates continuously at a time

• Valves adjust flow to Interface Heat Exchangers

Regenerative Heat Exchanger

• Only in use when the LCA is activated in single loop mode

• The Regenerative Heat Exchanger warms 35 degree loop water before entering 62 degree loop

• This is done to prevent condensation in the 62 degree loop

Interface Heat Exchangers

• Identical internal and external systems• Intertwined spirals of piping allow heat to conduct

between the internal water systems, and the external ammonium systems– Ammonium and water never mix as all heat is

conducted through the walls of the piping• Sensors will alert crew to any leak of ammonium

that would possibly contaminate the water system.

External Thermal Control System

• Interface Heat Exchanger, Pump Package Assembly, TRRJ, Radiator

• Uses ammonium to prevent damage to pipes from extreme temperature differences

• Ammonium has a lower freezing point than water, however in higher concentrations can prove toxic to the crew

Pump Package Assembly (PPA)

• Circulates ammonium through external systems an d water through the internal systems

• Only two external loops, one PPA per loop• Powered by EPS loads• Also known as Pump Module Assembly

(PMA)

Radiators / TRRJ

• Radiators allow heat to radiate into the space environment.

• Thermal Radiator Rotation Joint– Acts as a large loop

crossover for PPAs

Accumulator

• The Accumulator is attached to the PPA

• Helps absorb changes in ammonia volume because of different temperatures

• Resupplies external loop with ammonium if it is lost

Warning signs of a SOBE

• Red indicator lights on the system wall• Increase in ambient temperature and or

humidity• Ammonium smell (very obvious)• Contingency of another SOBE

Things to check during a SOBE

• Flow Rate – If no fluid is moving, then no heat is either

• Loads for faulty pump/PPA– No power = No flow

• Ammonium leaks (sensor info)– Toxic to Crew– Reduces flow in external system