pump motor thermal transnt

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Robert Fritz EngineeringGlendale, CA 91206

Document: RJ F-001

Revision NC

THERMAL ANALYSIS REPORT

for a

PUMP MOTOR, TWO POLE

Date: XXXX

Prepared for:

XXXXX

XXXXX

Approvals

Originator ______________________ _____________

Robert Fritz Date

Customer _______________________ _____________XXXX XXXX Date


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Doc No: RJF-001 PAGE 2

TABLE OF CONTENTSSECTION TITLE PAGE

1. INTRODUCTION 31.1 Purpose of Analysis 3

1.2 Summary 32. DESCRIPTION OF ANALYSIS 33. SOFTWARE AND REFERENCES 64. DETAIL THEORETICAL ANALYSIS 64.1 Heat Generated by the Pump Motor 64.2 Rough Order of Magnitude Motor Temp. after 300 Seconds Operating -

No Cooling6

4.3 Heating Values used in the FEA 64.4 Material Properties used in the FEA 74.5 Average Temperature Rise of Coolant 74.6 Thermal Gradient Across the Coolant Convection-Film 8

LIST OF FIGURESFIGURE TITLE PAGE

1. Coolant Temperature vs. Coolant Flow Rate 42. Maximum Temperature of Pump Motor Coil vs. Coolant Rate 43. Transient Solution FEA Thermal Gradient Output of the Pump

Motor at 300 Seconds of Operation5

5. Steady-State Results of the FEA Model 7

LIST OF TABLESTABLE TITLE PAGE

I Material Properties Used in the FEA 7II Temperature Rise of the Coolant at Various Flow Rates 8III Temperature Rise Across the Coolant Convection-Film at Various

Flow Rates8

LIST OF APPENDICIESAPPENDIX TITLE PAGE

A Transient Solution FEA Thermal Gradients of Previous Designs A1-A5


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1. INTRODUCTION

1.1 Purpose of Analysis

This report presents the thermal design analysis for a Two-Pole Pump Motor. The

primary task of the Pump Motor is to pump coolant. The Pump Motor is a 198 horsepowerpump motor designed to perform in continuous operation for a period of 300 seconds from start-up. It has an efficiency of 97.1% and an operating speed of 27,487 rpm. It is desirable to keep

the maximum temperature of the areas of the motor in contact with coolant to less than 59. Thecoolant was assumed to be at 29 initially.

The results of the thermal analysis include maximum heat generated, maximum predictedthermal gradients and graphs of critical hot areas of the motor vs. flow rate of the coolantthrough the pump motor.

1.2 Summary

The results of the thermal analysis show the operation of the Pump Motor as a viable designsolution per the requirements of its function. The optimum design depends on a certain amountof coolant to cool the pump motor. Figure 1 shows a graph of the flow rate of the coolant vs. thetemperature of the coolant. Figure 2 shows a graph of the flow rate of the coolant vs. themaximum coil temperature of the Pump Motor. Figure 3 is a transient solution FEA thermalgradient output of the Pump Motor at 300 seconds of operation. The coolant is assumed to bean infinite heat sink for this solution. The coolant temperature is adjusted in figure 1 to accountfor the heat transfer from the Pump Motor itself. The maximum coil temperature was adjusted

in figure 2 to account for both the rise in the coolant temperature and the temperature rise acrossthe forced-convection film of the coolant flow. Figure 4 shows the design layout of the PumpMotor.

Appendix A shows prior designs as analyzed and the transient solution FEA at the end of 300seconds of operation. Again, these solutions assumed an infinite heat sink in place of the liquidhydrogen cooling passages.

2. DESCRIPTION OF THE ANALYSIS

The detail theoretical analysis describes the fundamentals and procedure by which the final

results were obtained. As previously mentioned, the coolant in the cooling passages of thePump Motor housing was initially assumed to be an infinite heat sink in order to simplify theFEA model. The theoretical analysis was used to derive two other thermal gradients which werecombined with the values in the FEA. The two other thermal gradients are the temperature risein the coolant and the thermal gradient across the forced-convection film of the coolant.


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Figure 2. Maximum Temperature of Pump Motor Coil vs. Coolant Flow

225

230

235

240

245

250

255

260

265

270

275

0 5 10 15 20 25 30 35 40 45

Coolant Flow in GPM

MaxTemperatureofCoil

Figure 1. Coolant Temperature vs. Coolant Flow Rate

29

31

33

35

37

39

41

43

45

47

49

51

0 5 10 15 20 25 30 35 40 45

Coolant Flow in GPM

CoolantTemperature


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Figure 3. Transient Solution FEA Thermal Gradient Output of the Pump Motor at300 Seconds of Operation

2. DESCRIPTION OF ANALYSIS (Cont.)

It was assumed that the entire system starts at 29 prior to the operation of the pump. As soon asthe pump is started and it begins pumping coolant, the pump motor coils begin to heat up.Initially, the entire heat generated by the coils is absorbed by the thermal capacitance of thepump motor housing material. As the material begins heating up, a proportionally increasingamount of heat reaches the outer part of the housing where the coolant passages are located. Acontrolled amount of coolant is used to provide the pump motor with a means of extracting someof the heat away from its coils. The results were derived in order to provide the end user withenough information to perform a reasonable trade-off study and arrive at an appropriate coolant

flow rate.

The resultingT of the analysis varies from 203 to 241, which is very much in the ballpark of239 which was calculated in section 5.2. This validates the FEA results.


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3. SOFTWARE AND REFERENCES

Finite Element Analysis Software: Algor MECH/E Integrator; 9/23/96Algor Heat Transfer Analysis Extender; 9/23/96

Algor Inc.Pittsburgh, PA

Graphing Software: Excel, version 7.0Microsoft Corp.

Theoretical Analysis References: Marks Standard Handbook for Mechanical Engineers,Eighth Edition, Baumeister; 1978

Cooling Techniques for Electronic EquipmentDave S. Steinberg; 1980

4. DETAIL THEORETICAL ANALYSIS

4.1. Heat Generated by the Pump Motor

Q =(power)(efficiency) =(198 hp)(745.7 watts/hp)(3.413 Btu/hr/watt)(.029) =14614 Btu/hr

4.2. Rough Order of Magnitude Motor Temp. after 300 Seconds Operating - No Cooling

E =wCPTE is heat energy input

w is weight of mass being heatedCP is specific heat of the mass being heated

T is the change in temperature

E =Qt =(14614 Btu/hr)(300 seconds)/(3600 sec/hr) =1218 Btuw =51 lb

CP .1 Btu/lb-F

T 239 temperature rise oraverage temperature =268 after 300 seconds with no cooling.This value is important, as it is a check to validate the FEA results with a ballpark value.

4.3. Heating Values used in the FEA

Volume of Coils =32.4 in3; Volume of Lamination =150 in3It was assumed that 25% of the heat generated came from the coil in the axisymmetric model ofthe FEA and 75% came from the laminations. Therefore,(q/vol)laminations =(10961 Btu/hr)/(150 in

3) =73.1 Btu/hr- in3(q/vol)coils =(3654 Btu/hr)/(32.4 in

3) =113 Btu/hr- in3


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Qtransient =Qsteady-state(T transient/ T steady-state)T transient =228 - 29 =199T steady-state=909 - 29 =880

Qtransient =14614 Btu/hr(199/880) =3305 Btu/hr

Now, from the initial equation, WT =Q/CP =(3305 Btu/hr)/(2.4 Btu/lbm-F) =1377 lbm-F/hrH2 =(4.42 lbm/ft

3)/(7.481 gal/ft3) =.591 lbm/gal

WT =(1377 lbm-R/hr)/( .591 lbm/gal)/(60 min/hr) =38.8 gpm-F

Table II. Temperature Rise of the Coolant at Various Flow RatesFlow rate (gpm) 2.5 5 10 20 40

T 16 7.8 3.9 1.9 1.0

4.6. Thermal Gradient Across the Liquid Hydrogen Convection-Film

T =Q/hcA, which is the change in temperature across a forced-convection film

hc is the liquid forced-convection coefficient =J C GC

KP

P

2 3/

J is the Colburn factor =.

( ) .025

02NRfor turbulent flow conditions, or NR >7000.

G =W/AXC where W is the weight flow of the liquid and AXC is the cross section area of theflow

The following are constant values used throughout:

AXC =.0152 ft2

D is the hydraulic diameter =2ad

a d=.0565 ft

is the viscocity of coolant =.024 lbm/ft-hr

K is the thermal conductivity of coolant =.0726 Btu/hr-ft-R

A is the surface area of the coolant passage =1.97 ft2

Q is the heat leaving =3305 Btu/hr

Table I II. Temperature Rise Across the Coolant Convection-Film at Various Flow Rates

Flow rate (gpm) 2.5 5 10 20 40Weight flow rate, W (lbm/hr) 89 178 355 710 1420

Weight flow velocity, G (lb/hr-ft2) 5839 11678 23355 46711 93421

Reynolds Number, NR (dimensionless) 13745 27491 54981 109963 219926

Colburn factor, J (dimensionless) .00372 .00324 .00282 .00245 .00214

Forced-convection coeff., hc (Btu/hr-ft2-F) 73.7 128 224 389 679

T (R) 23 13 7.5 4.3 2.5


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APPENDIX A

Transient Solution FEA Thermal Gradients of

Previous Designs


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Report #RJF-001 Page A1

Initial Design No Forced Cooling

Design #1 Thermal Gradient without Coils


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Design #2 Thermal Potting Around Coils


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Design #3 L iquid Cooling In J acket, No Heat Sink Around Coils

Design #3 Thermal Gradient without Coils


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Design #4 L iquid Cooling In J acket With Heat Sink Around Coils


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Design #6 No Heat Sink or J acket Complete Immersion in Coolant

pump motor thermal transnt

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