Coupled Thermo-electric VTB Simulation Model of Cooling Loop of a Ship System Jamil Khan, Ruixian Fang, A. Monti, Wei Jiang, University of South Carolina Greg Anderson, Mark Zerby, Phil Bernatos NSWC, Philadelphia ESRDC Modeling and Simulation Workshop Tallahassee, FL 14 February, 2006

Outline Problem Statement Models –Thermal –Electrical Simulation Results Conclusions

Problem Statement

Schematic for zone 2 Level 4 Level 3 Level 2 Level 1 FreshWater SeaWater HeatExchanger FreshWater Heatsink HeatExchanger Pipe Pump Valve SeaWater HeatSink Temperature mass flow PCM board Mixing model 2 nd layer of Fw_HEX

Fresh Water- Sea Water Heat Exchanger Number of elements can be changed Governing Eqns for each element: L L/120 Sea_Water Element #i T in Conditions: m*h<=M where M is the mass of fluid of each element, as a special case, e.g., m*h=M, for each time step water in one element totally move into the next element. Where ----Fresh water inlet temperature ----Fresh water temperature at time (t-h) ----Average fresh water mixing temperature at time (t-h ) ----Mass flow rate ----time step ----Mass in control volume of each element Where ----Fresh water temperature at time t ----Sea water temperature at time t Fresh water Sea water

Heat Sink Assume no temperature gradient along the length direction; Governing Eqns : T1,Q1 T2,Q2 Qa We can also build this modal for several parts if necessary, that will take consider of the temperature difference along the length direction. Where ----Inlet heat flow from heat source ---- Outlet heat flow from heatsink ---- heat absorbed by heatsink Where ----Mass of heatsink ---- Heatsink heat capacity

FreshWater- HeatSink Heat Exchanger Each model includes 12 elements; Governing Eqns for each element: The same logic used in this model as shown in Fresh water- Sea water HeatExchanger Conditions: m*h<=M where M is the mass of each element, as a special case, e.g., m*h=M, for each time step water in one element totally move into the next element. m,p Tin Tout Q,T Element model m1,p1m2,p2 Tin T 1, final Tav #1#2 Q1Q2Q3 #3 Q,T from heat sink Where ----heatsink temperature at time t ---- heatsink temperature at time t-h

Other models Water Mixing Chamber Model Valid for 2 entering streams with different mass flow rate and temperature; Governing Eqns : m1T1 m2 T2 m_outT_out Pipe Model Mainly account for the pressure change caused by height elevation; Which can be written as Linear Valve Model Assume pressure drop linearly depends on the throttle opening.

Electrical System Model models can be seamlessly substitute to perform analysis Two different levels of details have been developed for the Electro-thermal model Those two with more or less focus on electrical system waveform

Model 1 The electrical system is represented as a constant power load (the user can specify active and reactive power) The interaction with the thermal system is given by the efficient coefficient Any loss resulting from the efficiency calculation is supposed to be a forcing function for the thermal system

Model 1 Three-phase electrical terminal Thermal port

Model 2 The model includes the power electronics, the control and the electrical machine The power electronics is modeled through an averaged model Switching and conduction losses are estimated from the averaged model

Model 2 PEBB’s with Thermal port Control system Induction machine Controlled rectifier

4 PCM Heat Source 4 Heatsink Temperature Example simulation results for PCM and Heatsink Model

Example simulation results for the freshwater-Seawater HeatExchanger Fresh water inlet Temp. Sea water outlet Temp. Fresh water outlet Temp.

Example simulation results for the freshwater-Seawater HeatExchanger Fresh water Temperature Field #120 Element #110 Element #100 Element #10 Element #20 Element Length direction

Example simulation results for the freshwater-Seawater HeatExchanger #120 Fresh water Temperature #110 Fresh water Temperature #100 Fresh water Temperature #10 Fresh water Temperature #20 Fresh water Temperature

Conclusions A real time coupled thermo-electrical simulation for slice 2 of DDG-51 has been successfully developed in VTB The simulation couples electrical and thermal models Results have been validated with experimental data The simulations can be extended to include chillers Transient responses to changing loads can be studied –Simulation is available for demonstration