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Designing for Thermal Control

Designing for Thermal Control. Sam Rodkey February 14 th , 2005 Project Management Project Manager. MHV Heat Pump Cycle Design. MHV Active Thermal Control System. Calculated using cycle analysis in EES with R134 based on peak estimated heat loads.

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Designing for Thermal Control

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  1. Designing for Thermal Control Sam Rodkey February 14th, 2005 Project Management Project Manager

  2. MHV Heat Pump Cycle Design

  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: 83.02 m2 (Volume = ~ 5 m3) • 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

  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

  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).

  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.

  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)

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