Interdisciplinary Project with South Texas Project Funded by The Nuclear Power Institute

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Team Members:Matt Langston – CHEN: SeniorKyle Bowzer – MEEN: JuniorRyan Bigelow – MEEN: JuniorMatthew King – MEEN: JuniorRichard Colunga – ELEN: Sophomore Jennifer Banegas – CVEN: FreshmanGeorge Campa – CHEN: FreshmanBrent Mayorga – AERO: Freshman

MentorsGraduate Mentor: Andron CrearyTAMU Mentor: Mr. Cable KurwitzSTP Mentor: Mr Rick Grantom

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Agenda

Motivation & Project Components Project Objectives CFD Analysis Lumped Parameter Simulations Experimental Results Summary Future Work

Motivation & Project Components MotivationMotivation

Provide STP’s Probabilistic Risk Assessment (PRA) Provide STP’s Probabilistic Risk Assessment (PRA) Team with air temperature profile data after a Team with air temperature profile data after a hypothetical loss of HVAC. hypothetical loss of HVAC.

Project ComponentsProject ComponentsCFD AnalysisCFD Analysis

○ Using a SolidWorks created model of room and Using a SolidWorks created model of room and electrical cabinetselectrical cabinets

Analytical CalculationsAnalytical Calculations○ Perform calculations in Matlab using a Lumped Perform calculations in Matlab using a Lumped

Parameter MethodParameter MethodLaboratory ExperimentsLaboratory Experiments

○ Run experiments investigating the heat transfer and Run experiments investigating the heat transfer and energy storage within a solid materialenergy storage within a solid material

Simulation Objectives

Determine air and metal heat up rates during various HVAC failure scenarios

Gain information on when and where the air temperature reaches manufacturer’s critical temperature (104°F)

Investigate the effect of energy storage within metal in the transformers using a cabinet CFD model

CFD - SolidWorks Model

InletsInlets

InletsInlets

OutletsOutlets

Heater RodsHeater Rods

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Distribution of Heat Loss

29935 watts

3131 watts

1966 watts

12596 watts

200 watts

2234 watts

1759 watts

2519 watts

1523 watts

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29935 watts

CFD Simulations Computer Simulations

Case 1: Steady State○ Simulates the EAB

room’s “Normal Operating Conditions” (50°F inlet air temp and 19870 cfm)

Case 2: Transient○ Simulates the loss of one

of the HVAC trains (50% air flow)

Case 3: Transient○ Simulates the HVAC

chiller failure (73°F inlet air temp instead of 50°F)

Case 4: Transient○ Simulates the total loss of

HVAC

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Case 1 - Temperature Profile for “Normal Operating Conditions”

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64°F average

Case 1 - Maximum Temperature “Normal Operating Conditions”

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Max air temp ~78 °F (above main cabinet)

Max air temp between cabinets ~64°F (at 5ft)

5 ft

Case 2 - Temperature Profile “Half-flow Simulation”

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68°F average

SS after ~ 21min

Case 3 - Temperature Profile “HVAC Chiller Failure”

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83°F average

SS after ~ 19 min

Temperature Profile “Total HVAC Failure”

When Critical Temperature (104°F) is Reached

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Critical temperature (104F) location

After ~19 minutes

Final Results Plot

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Case 1Case 1

Case 3Case 3

Case 2Case 2

Case 4Case 4

104°F

Energy Storage in Transformers The HVAC failure problem is more complicated because it

is a transient problem Stored thermal energy flow is important in the temperature history In particular, the heat up of the transformer’s copper windings

and iron cores due to the high specific heat capacity.

Bounding the Specific Heat Based on manufacturer’s specifications of transformer

cabinets in the EAB room, metal mass composition values were assumed: Stainless steel: 15-20% Aluminum: 5-20% Iron: 20-60% Copper: 40-60%

Bounded Values Using Matlab, all

possible mass combinations were computedUsed to determine

max, min, mean of lumped specific heat

Min Cp Avg Cp Max Cp

453.3 J/kg*K 504.1 J/kg*K 554.9 J/kg*K

Transformer Cabinet Model

Cabinet Simulations

Steady state conditions with a uniform air flow across the cabinet’s outer surface

Transient simulation with no forced flow using:Maximum specific heatMinimum specific heat

Cabinet Temperature Profile: Steady State

Front View of Air Velocity Profile:

Steady State

Side View of Air Velocity Profile:

Steady State

Cabinet Simulation Results

Lumped Parameter Simulations (1/5)

Objective:Create a theoretical model of the EAB

room’s thermal activityProvide an alternative solution method that

will predict air heat up rate.○ Provide confidence in computational model.

Allow an additional means of connecting the simulation results with the experimental results.

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In our current analytical approach, the room is reduced to two heat-storing masses, the cabinets and the air. From the basic equation for heat storage,

two differential equations can be derived for the air

temperature and cabinet surface temperature:

Lumped Parameter Simulations (2/5)

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d

dtTair

hA(Tm Tair )M air Cpa

andd

dtTm

Pg hA(Tm Tair )Mm Cpm

Lumped Parameter Simulations (3/5)

The two equations on the previous slide can be arranged in a heterogeneous linear system of equations, which can be solved simultaneously through matrix methods to yield:

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Tair C1 C2e2 t

Pg t

M airCpa MmCpm1

2

PgM airCpa MmCpm

and

Tm C1 C2M airCpaMmCpm

e2 t Pg t

M airCpa MmCpmPg2

M airCpaMmCpm

M airCpa MmCpm

Where: 2air a m m

hA hA

M Cp M Cp

is the second eigenvalue. (λ1 = 0)

Lumped Parameter Simulations (4/5)

To confirm simulation validity, geometric parameters were taken from SolidWorks model

Pg = heat generation = 85700 W = 292400 Btu/hr

Mair = mass of air in room = 5657 lbs

Mm = mass of cabinets = 1638000 lbs

Cpa = air heat capacity = 0.241 Btu/lb °F

Cpm = metal heat capacity = .117 Btu/lb °F

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Lumped Parameter Simulations (5/5)

Once all parameters are known, the constants C1 and C2 can be determined from initial conditions (t = 0). Initial conditions used:

Tair(0) = 63.4 °F and

Tm(0) = 181.3 °F

Once constants are known, equation for Tair = 104°F can be solved for t, which may be used to determine Tm at that time

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From SS simulation under normal operating conditions

Analytical Solution Assumptions Uniform heat generation. The convection coefficient does not

vary spatially. The convection coefficient is fairly

constant over the temperature range.

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Overall Approaches

Three approaches:Perform calculations by hand/in Excel

spreadsheet.Model simplified version in FloWorks with

cabinets lumped together.Use differential equation solver ODE45 in

MATLAB

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Analytical Solution Results Hand Calculations/Excel file (with h = 6

W/m2 °C = 122.4 Btu/hr ft2 °F:

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Analytical Solution Results

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•Simplified FloWorks Simulation (h calculated automatically by FloWorks a CFD package):

Experiment Overview

1. Goal

2. Approach

3. Experimental setup

4. Tests

5. Results

Experiment Goals

Determine thermal conductivity (k) Benchmark the FloWorks CFD package

using experimental results

dx

dTKAQ xx

3.7in

2.5in

2.5in

Experimental Setup ( 1 /2 )

Fourier’s Law

Experiment Setup (2/2 ) Aluminum & steel blocks

2.5x2.5x3.7 in 200 W cartridge heater

Approximately 95% Efficiency

Block system: Cartridge heater and thermocouples are

covered with silicone grease to remove insulating effects of air

4. Tests

Test 1:Insulated aluminum blockPower remains constantDetermine the thermal heat generation and

conductivity (k)

5. Results Test 1:

Temp Deviation at 373.15 (deg C) k avg (W/m*K) k_standard (W/m*K) % Error in k

0.28 190 200 5

Convection experiment using same setup

Conduct testing with different materials Create FloWorks model with the same

material and conditions to benchmark simulation results

Experiment Future Work

Project AccomplishmentsUsed computer simulation results to predict the

heat-up rate of the EAB room.Normal Operating Conditions : ~63°FHalf flow single train failure: ~79°FHVAC chiller failure: ~ 82.6°FTotal HVAC failure: ~19 minutes after total failure

(104°F)Derived equations to analytically calculate the

heat-up rate using lumped parameter model.Heat-up rate: ~7 minutes after total failure (104°F)

Designed an experimental setup that can be easily compared with a Cosmos FloWorks CFD package.

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Andron Creary, Kyle Bowzer, Brent Mayorga, Matthew King, Ryan Bigelow,

George Campa, Jennifer Banegas, Matt Langston, Richard Colunga

QUESTIONS?