AAE 450 – Spacecraft Design Sam Rodkey 1 Designing for Thermal Control Sam Rodkey February 14 th, 2005 Project Management Project Manager

AAE 450 – Spacecraft Design Sam Rodkey 2 MHV Heat Pump Cycle Design

AAE 450 – Spacecraft Design Sam Rodkey 3 MHV Active Thermal Control System  Calculated using cycle analysis in EES with R134 based on peak estimated heat loads.  Estimated Mass : 2000 kg (~1250 kg for radiators, 750 kg for support hardware and coolant, this represents 75% reduction in mass from previous estimates of the system)  Estimated Emitting Area: m 2 (Volume = ~ 5 m 3 )  Max Total Heat Rejected: 105 kW (at approx 350 K)  Max Total Heat Pumped from Interior : 80 kW (at approx 283 K, 50 F)  Max Total Power Consumed: 25 kW  System can be adjusted to deal with lower heat loading by lowering mass flow rate of coolant.  Future versions of this script will look at other coolant choices, more detailed heat exchanger analysis, piping head loss

AAE 450 – Spacecraft Design Sam Rodkey 4 What is this script doing? The program takes the following inputs:  Maximum ambient atmospheric temperature (T_inf)  Maximum desired temperature at the heat exchanger (T_max_evap)  Compressor pressure ratio (pratio)  Coolant fluid  Estimate of Radiator Material average density  Estimate of Radiator material thermal conductivity

AAE 450 – Spacecraft Design Sam Rodkey 5 What is the script doing? The program then performs the following algorithm:  Calculates weighted average atmospheric conditions based upon Mars atmospheric composition  Sets up vapor compression cycle constraint equations and calculates states with estimated coolant flow rates and heat transfer.  Relates those equations to an estimation of total radiator area and mass based upon free-convection correlations for vertical flat plates (a worst case heat transfer scenario).

AAE 450 – Spacecraft Design Sam Rodkey 6 Future additions to the script  Comprehensive study of different coolant choices  An analysis of the water cooling system  More detailed solution of radiative heat transfer  Effect of the Shape of the Fins/Radiators  Analysis of frictional effects and compressor requirements  Detailed low temperature heat exchanger design and sizing using NTU and LMTD relations.

AAE 450 – Spacecraft Design Sam Rodkey 7 References About EES  Engineering Equations Solver (EES) is an implicit equation solver which has fluid property information and thermo-physical functions that allow for optimization of cycles.  This program allows users to set cycle constraints that will implicitly to solve for states. References  Fundamentals of Heat and Mass Transfer by Incropera, Dewitt, Fourth Edition (ME 315 Text)  Fundamentals of Engineering Thermodynamics by Moran, Shapiro, Fifth Edition (ME 200, ME 300 Text)