United States Air and Radiation EPA/430/R-92/009 Environmental Protection (ANR-445) October 1992 Agency 

# EPA Finite Element Analysis of Heat

Transfer Through the Gasket Region of Refrigerator/Freezers

Printed on Recycled Paper 

# &EPA UnitedStates EnvironmentalProtection Agency AirandRadiation (ANR-445) EPAl430/R-921009 October1992 

# FiniteElementAnalysisofHeat TransferThroughtheGasket Regionof'Refrigerator/Freezers

@ PrintedonRecycledPaperFinite Element Analysis of Heat Transfer through the Gasket Region of Refrigerator/Freezers

BY Shirley Flynn and Keith Rouch Department of Mechanical Engineering University of Kentucky, Lexington, KY 40506
and H. Alan Fine Global Change Division U.S.-E.P.A., Washington, DC 20460

October 1992 Finite ElementAnalysis ofHeat Transfer through the Gasket Region of Refrigerator/Freezers

BY Shirley Flynn and Keith Rouch Department of Mechanical Engineering University of Kentucky, Lexington, KY 40506
and H. Alan Fine Global change Division U.S.-E.P.A., Washington, DC 20460

october 1992Finite Element Analysis of Heat Transfer through the Gasket Region of Refrigerator/Freezers

ABSTRACTHeat flow through the gasket region of a refrigerator/freezer (R/F) cabinet is a significant fraction of the total R/F thermal load. Reductions in this mode of heat transfer will thus result in lower R/F energy consumption. Finite element analyses (FEA) of two gasket used in U. S.R/Fs are developed. These models show that the thermal properties of the gasket have little influence on heat transfer in the gasket region, while heat flow down the metal door and cabinet flanges greatly impacted the overall rate of heat transfer into the cabinet. Gasket designs incorporating the modifications suggested by the FEA were developed and tested in prototype R/Fs. Total R/F energy consumption reductions of 5 to 8 percent were achieved. These reductions were slightly less than the 5 to 11 percent reductions predicted by the models.

ii 

### FiniteElementAnalysis ofHeatTransfer through theGasketRegionofRefrigerator/Freezers

ABSTRACT Heat flow through the gasketregion of a refrigerator/freezer (R/F) cabinet is a significant fraction of the total R/F thermal load. Reductions in thismode of heat transfer will thus result in lowerR/F energy consumption. Finite element analyses (FEA) of two gasket used in U. S. R/Fs are developed. These models show that the thermal properties of the gasket have little influence on heat transfer in the gasket region, while heat flow down the metal door and cabinet flanges greatly impacted the overall rate of heat transfer into the cabinet. Gasket designs incorporating the modifications suggested by the FEA were developed and tested in prototype R/Fs. Total R/F energy consumption reductions of 5 to 8 percent were achieved. These reductions were slightly less than the 5 to 11 percent reductions predictedby the models.

iiContents

Abstract ..................................................... ii Figures ...................................................... iv Tables ..................... v .................................. Introduction, ......... o ... o .............. o ................. 1 Finite Element Models ... ........... o ............. oo .......... 2 FEA Results

- Current Designs ................................ 6 FEA Results

- New Designs...: 14 Measurements
- New Designs ................................... 26 Conclusions .................................................. 28 Acknowledgements ............................................. 29 References ................................................... 29

iii contents

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# . . .. . Introduction. Finite Element Models..•. Current Designs. • • • • • • • • • • • • • • • • • • • • 0 • • • • • • • • • • FEA Results FEA Results Measurements New Designs
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### v 1 2 6 14 26 Conclusions.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Acknowledgements.

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iii 29 29Figures

Number 1 Finite element model of SubZero gasket region ............. 3 2 Finite element model of GE gasket region .................. 4 3 Temperature profiles in SubZero gasket . ................... 8 4 Temperature profiles in SubZero gasket without decorative cover .................................. 10 5 Finite element model for the GE gasket including the foam in the door and cabinet ................ 11 6 Temperature profiles in GE gasket ......................... 12 7 Finite element model and temperature profiles for modified SubZero gasket containing a low conductivity gas .......................................... 15 8 Finite element model and temperature profiles for modified GE gasket containing a low conductivity gas ...... 16 9 Finite element model and temperature profiles for uncoupled heat flow in modified SubZero gasket ............ 18 10 Finite element model and temperature profiles for modified SubZero gasket region which includes a plastic clip and approximately half plastic door and cabinet flanges ...................................... 20 11 Finite element model and temperature profiles for modified GE gasket region which includes a plastic clip and approximately half plastic door and cabinet flanges .................................................. 21 12 SubZero gasket region load reductions for various flange modifications ...................................... 22 13 GE gasket region load reductions for various flange modifications ............................................ 25

iv Figures Number 1 Finite element model of SubZero gasket region.........•.•. 3 2 Finite element model of GE gasket reg10n.................. 4 3 Temperature profiles in SubZero gasket.... 0 •••••••• 0 •••••• 8 4 Temperature profiles in SubZero gasket without decorative cover.................................. 10 5 Finite element model for theGE gasket including the foam in the door and cabinet.•.•....•...•... 11 6 Temperature profiles in GE gasket•..•..••....••........... 12 7 Finite element model and temperature profiles for modified SubZero gasket containing a low conductivity gas.......................... 0 • • • • • • • • • • • • • • • 15 8 Finite element model and temperature profiles for modified GE gasket containing a low conductivity gas..•... 16 9 Finite element model and temperature profiles for uncoupled heat flow inmodified SubZero gasket•••........• 18 10 Finite element model and temperatureprofiles for modified SubZero gasket region which includes a plastic clip and approximatelyhalf plastic door and cabinet flanges...................................... 20 11 Finite element model and temperature profiles for modified GE gasket regionwhich includes a plastic clip and approximatelyhalf plastic door and cabinet flanges........ 0 •••••••••••••••••••••••••••••••••••• CI • • • • 21 12 SubZero gasket region load reductions for various 

### flange modifications...................................... 22 13 GE gasket region load reductions for various flange modifications......................... 0 • • • • • • • • • • • • • • • • • • 25

ivTables

Number 1 Properties of Materials ................................... 5 2 Variation of SubZero Gasket-Region U-value with R/F Temperatures .................................... 6 3 Variation of SubZero Gasket-Region U-Values with Heat Transfer Coefficients
........................... 7 4 Effect of Flange/Foam Boundary Condition on Overall Gasket Heat Transfer Coefficient
.................. 13 5 Comparison of U-values for'Gaskets containing Air and Krypton ........................................... 14 6 Comparison of U-values for the SubZero Gasket with Coupled and Uncoupled Flanges .
....................... 17 7 U-Values for SubZero Gasket Region with a Portion of the Flanges changed to Plastic
......................... 23 8 U-Values for GE Gasket Region with a Portion of the Flanges changed to Plastic ............................ 24 9 Effect of Flange/Foam Boundary Condition on U-Value of Modified GE Gasket Region ...................... 26

v Tables Number 1 Properties ofMaterials....................... . . . . . . . • . . • . 5 2 Variation of SubZero Gasket-Region U-value with R/F Temperatures...•.................. 0 • • • • • • • • • • • • • 6 3 Variation of SubZero Gasket-Region U-Values with Heat Transfer Coefficients....••••.•..•.•.•......**~...** 7 4 Effect of Flange/FoamBoundary Condition on Overall Gasket Heat Transfer Coefficient.....•............ 13 5 comparison of U-values for'Gaskets containing Air and Krypton.. III ••••••••••••••••••••••••• 0 •••• III •• 0 • • • • • • 14 6 Comparison ofU-values for the SubZero Gasket with Coupled and Uncoupled Flanges.•.•.......•.........•.. 17 7 U-Values for SubZero Gasket Region with a Portion of the Flanges changed to Plastic...........•...........•. 23 8 U-Values for GE Gasket Region with a Portion of the Flanges changed to Plastic.........................•.. 24 9 Effect of Flange/FoamBoundary Condition on U-Value of Modified GE Gasket Region.•................•... 26



### vINTRODUCTION

Heat transfer through the gasket region significantly contributes to the thermal load through the refrigerator/freezer (R/F) cabinet
. Recent finite element analyses of refrigerator/freezers to assess the impact of the addition ofsuper insulation on the energy consumption of R/Fs showed approximately 25 percent of the total thermal load entered the cabinet through the gasket region, i.e. the gasket and flanges. (1) This load increased to over 35 percent of the total for a cabinetthat was nearly completely covered with super insulation. Clearly, heat transfer through the gasket region is an important portion of the overall heat transfer flux, and becomes even more important as the rest of the cabinet becomes more insulated.Analyses and tests performed in the design of a super efficient R/F in 1980 (2) demonstrated that the heat flow through the gasket region could be halved with the addition of a second gasket. Difficulties in implementing the double-gasket concept, however, have prevented its use in production units. This report presents the results of finite element analysis (FEA) of heat flow through two gasket/flange designs employed in 1991 in U.S. refrigerator/freezers
. Modifications to the designs that could yield significant R/F thermal load reductions are also presented and evaluated.

1 INTRODUCTION

Heat transfer through the gasket region significantly contributes to the thermal load through the refrigerator/freezer (R/F) cabinet. Recent finite element analyses of refrigerator/freezers to assess the impact of the addition of super insulation on the energy consumption of R/Fs showed approximately 25 percent of the total thermal load entered the cabinet through the gasket region,**i~e.** the gasket and flanges. (1) This load increased to over 35 percent of the total for a cabinet thatwas nearly completely coveredwith super insulation. Clearly, heat transfer through the gasket region is an important portion of the overall heat transfer flux, and becomes even more important as the rest of the cabinetbecomes more insulated. Analyses and tests performed in the design of a super efficientR/F in 1980 (2) demonstrated that theheat flow through the gasket region could be halved with the addition of a second gasket. Difficulties in implementing the double-gasket concept, however, haveprevented its use inproduction units. This report presents the results of finite element analysis (FEA) of heat flow through two gasket/flange designs employed in 1991 in U.s. refrigerator/freezers. Modifications to the designs that couldyield significantR/F thermal load reductions are also presented and evaluated.

1FINITE ELEMENT MODELS

Two gasket designs were selected for analysis in this study, a gasket employed in SubZero side by side models and a gasket used in General Electric top-mount freezer units. These gaskets represent the extremes of complexity of cross section designs for gaskets found in U.S. R/Fs. Gasket dimensions were obtained for the finite element analyses by cutting the gaskets perpendicular to their length. Photographic transparencies of the cross sections were then made and projected onto a sheet of paper
. The approximately seven times enlarged images were then traced and measured
. Correct dimensions were achieved by including a scale in the photographs of the gaskets. Gasket thicknesses of 0.48 and 0.56 inches were found for the SubZero and GE gaskets, respectively.

Analyses were performed for the gasket region which included the gasket, mounting clip, flanges and a small portion of the outer steel case. A small portion of the liner and foam insulation was also included in several analyses of the GE gasket region. Flanges, mounting clip, case and liner were assumed to have a thickness of 0.024 inches. The finite element models of the Subzero and GE gasket regions are shown in Figures 1 and 2. The thermal conductivity for the plastic gasket material and liner, flexible gasket magnet, air contained within the gasket, and metal flanges, clip and case used in this analysis are shown in Table 1. Engineering units and the values used by the finite element code ANSYS are given.

2 FINITE ELEMENT MODELS

Two gasket designs were selected for analysis in this study,
a gasket employed in SubZero side by side models and a gasket used in General Electric top-mount freezer units. These gaskets represent the extremes of complexity of cross section designs for gaskets found inU.S. R/Fs. Gasket dimensions were obtained for the finite element analyses by cutting the gaskets perpendicular to their length. Photographic transparencies of the cross sections were then made and projected onto a sheet of paper. The approximately seven times enlarged images were then traced and measured. Correct dimensions were achievedby including a scale in thephotographs of the gaskets. Gasket thicknesses of 0.48 and 0.56 inches were found for the SubZero and GE gaskets, respectively. Analyses were performed for the gasket region which included the gasket, mounting clip, flanges and a small portion of the outer steel case. A small portion of the liner and foam insulationwas also included in several analyses of the GE gasket region. Flanges, mounting clip, case and liner were assumed to have a thickness of 0.024 inches. The finite element models of the SubZero and GE gasket regions are shown in Figures 1 and 2. The thermal conductivity for the plastic gasket material and liner, flexible gasket magnet, air contained within the gasket, and metal flanges, clip and case used in this analysis are shown in Table 1. Engineering units and the values used by the finite element codeANSYS are given.

2Figure 1. Finite element model of SubZero gasket region. Black
areas within model represent metal components, dark gray are plastic and light gray are air.

3 Figure 1. Finite element model of SubZero gasket region. Black
areas withinmodel represent metal components, dark gray are plastic and light gray are air.

3Figure 2. Finite element model of GE gasket region. Black areas within model represent metal components, dark gray are plastic and light gray are air.

4 Figure 2. Finite element model of GE gasket region. Black areas withinmodel represent metal components, dark gray are plastic and light gray are air.

4Table 1. Properties of Materials

M t i l Thermal Conductivity a er a Engineering Units ANSYS Units

(BTU*in)/(hr*ft2*°F) (BTU*in)/(hr*in2*OF) Plastic 1.016 0.007055 Magnet 1.016 0.007055 Air 0.18 0.00125 Metal 315.0 2.1875

Convection heat transfer boundary conditions were employed for the inner and outer surfaces. In most calculations, heat transfer from the flanges or case to the foam insulation whichfills the R/F doors and walls was assumed to be negligible compared to that along the metal piece. The foam/metal surfaces were, thus, assumed adiabatic
. Convection within the gasket pockets was also assumed to be negligible. Total heat flow rates through the gasket and flanges were calculated in the postprocessing module of ANSYS by summing the fluxes out of the elements which would constitute the surfaces of the gasket and flanges on the inside of the R/F. The overall heat transfer coefficient, U or U

-value, was calculated from the following equation:

U=Q / dTwhere Q was the total heat transfer rate out of the gasket region, and dT was the overall temperature difference.

5 Table 1. Properties ofMaterials Thermal Conductivity Material Engineeringunits ANSYS units (BTU*in)/(hr*ft2*oF) (BTU*in)/(hr*in2*oF) Plastic 1.016 0.007055 Magnet 1.016 0.007055 Air 0.18 0.00125 Metal 315.0 2.1875

Convection heat transfer boundary conditions were employed for the inner and outer surfaces. In most calculations, heat transfer from the flanges or case to the foam insulation which fills the R/F doors and walls was assumed to be negligible compared to that along the metal piece. The foam/metal surfaces were, thus, assumed adiabatic. Convection within the gasket pockets was also assumed to be negligible. Total heat flow rates through the gasket and flanges were calculated in the postprocessingmodule of ANSYS by summing the fluxes out of the elementswhichwould constitute the surfaces of the gasket and flanges on the inside of the R/F. The overall heat transfer coefficient, U or U-value, was calculated from the following equation:
U

## =Q / dT where 

### Qwas the total heat transfer rate out of the gasket region, and dT was the overall temperature difference.

5FEA RESULTS - CURRENT DESIGNS

The SubZero gasket region was analyzed with the steel case extended to form the decorative gasket cover found on production units, as shown in Figure 1, and with this piece removed. The results of these analyses and those performed on the GE gasket follow. SubZero Gasket
- Four combinations of R/F interior temperature, Tin, and ambient temperature,Tout, were analyzed. Since the thermal conductivities were assumed to be independent of temperature, the heat transfer rate should be proportional to Tout-Tin; and U should be independent of the temperature difference. Table 2 shows the results for heat transfer coefficients of 2 Btu/(hr*ft2*°F) at the inner and outer surfaces
. The effectof heat transfer coefficient on the overall heat transfer coefficient is shown in Table 3.

Table 2. Variation of SubZero Gasket-Region

U-Values with R/F Temperatures Temperature Total Heat Overall Heat Tin 1FTout Transfer Rate Btu/(hr*in) Trans. Coef f . , U Btu/(hr*in*°F) 0 & 70 0.2825 4.036E-3 0 & 90 0 .3632 4.036E-3 40 & 70 0 .1211 4 .036E-3 40 & 90 0.2018 4.036E-3

6 FEA RESULTS

- CURRENT DESIGNS

The SubZero gasket region was analyzed with the steel case extended to form the decorative gasket cover found on production units, as shown in Figure 1, and with this piece removed. The results of these analyses and those performed on the GE gasket follow. SubZero Gasket

- Four combinations of R/F interior temperature, Tin' and ambient temperature,Tout' were analyzed. Since the thermal conductivities were assumed to be independent of temperature, the heat transfer rate should be proportional to Tout-Tin; and U should be independent of the temperature difference. Table 2 shows the results for heat transfer coefficients of 2 Btu/(hr*ft2*oF) at the inner and outer surfaces. The effect of heat transfer coefficient on the overallheat transfer coefficient is shown in Table 3.

Table 2. Variation of SubZero Gasket-Region U-Values with R/F Temperatures Temperature Total Heat Overall Heat

Tin & Tout TransferRate Trans. Coeff., of Btu/(hr*in) Btu/(hr*in*oF) 0 & 70 0.2825 4.036E-3 0 & 90 0.3632 4.036E-3 40 & 70 0.1211 4.036E-3 40 & 90 0.2018 4.036E-3

6 UTable 3. Variation of SubZero Gasket-Region U-Values with Heat Transfer Coefficients Surface Heat Trans. Coefficient Btu/ (hr*ft2 * °F) Overall Heat Trans. Coeff., U Btu/(hr*in*°F) Percent Heat Flow through Clip & Flanges 1 2 5 10 2.407E-3 4. 036E-3 7. 347E-3 11.22E-3 17.5 21.0 28.8 37.0

The percentage of heat flow through the two metal flanges plus the metal clip shown in Table 3 is the percentage of the total energy entering the R/F cabinet from the gasket region as a result of convection from the ends of the two flanges and the clip. The heat flow rates from each of these three surfaces were nearly identical, and thus contributed equally to the total. As shown in Figure 3 for the 90 °F to 0°F temperature combination and heat transfer coefficients equal 2 Btu/(hr*ft2*°F), all three surfaces attain the same temperature . As all three were assumed to have the same thickness, equal heat transfer rates should result. The nonlinear nature of the isotherms shown in Figure 3 indicates that the percentage of heat flow through the flanges and clip is not indicative of the importance of their influence on the overall heat transfer process . In fact, nearly all of the heat entering the outer surface of the gasket region flows down the metal pieces avoiding the gasket . The heat flow then disperses across the gasket near the inner surface of the R/F, and then is transferred into the R/F by convection. Removing the decorative metal cover,- i.e. the extension of

7 Table 3. Variation of SubZero Gasket-RegionU-Values with Heat Transfer Coefficients SurfaceHeat Overall Heat Percent Heat Trans. Coefficient Trans. Coeff., U Flowthrough

Btu/(hr*ft2*oF) Btu/(hr*in*oF) Clip 

### &Flanges 1 2.407E-3 17.5 2 4.036E-3 21.0 5 7.347E-3 28.8 10 11.22E-3 37.0

The percentage of heat flow through the two metal flanges plus the metal clip shown in Table 3 is the percentage of the total energy enteringtheR/F cabinet from the gasket region as a result of convection from the ends of the two flanges and the clip. The heat flow rates from each of these three surfaces were nearly identical, and thus contributed equally to the total. As shown in Figure 3 for the gooF to OaF temperature combination and heat transfer coefficients equal 2 Btu/(hr*ft2*OF), all three surfaces attain the same temperature. As all three were assumed to have the same thickness, equal heat transfer rates should result. The nonlinear nature of the isotherms shown in Figure 3 indicates that the percentage of heat flow through the flanges and clip is not indicative of the importance of their influence
on the overall heat transferprocess. In fact, nearly all of the heat entering the outer surface of the gasket region flows down the metal pieces avoiding the gasket. The heat flow then disperses across the gasket near the inner surface of the R/F, and then is transferred into theR/F by convection. Removing the decorative metal cover,·i.e. the extension of
7Figure 3. Temperature profiles in SubZero gasket with 00 and90°F temperature extremes and heat transfer coefficients at the inner and outer surfaces of 2 Btu / (hr*ft2*OF).

8 Figure 3. Temperature profiles in SubZero gasket with 0° and gooF temperature extremes and heat transfer coefficients at the inner and outer surfaces of 2 Btu / (hr*ft2*oF).

8the metal case over the gasket shown in Figure 1, had an insignificant effect on the temperature profile, as shown in Figure 4. The minor changes which occurred were primarily in the higher temperature isotherms and the overall heat transfer coefficient increased by less than one percent to 4.069E-3 Btu/(hr*in*OF) at surface heat transfer coefficients of 2 Btu/(hr*ft2*OF). The overall heat transfer coefficient increased by about 0.03 Btu/(hr*in*OF) and the percentage of heat flow through the flanges and clip increased by about 0.1 percent regardless of the surface heat transfer coefficients. GE Gasket

- The GE gasket, shown in Figure 2, consists of the same materials as the SubZero gasket. Calculations were made with boundary conditions similar to those for the Subzero gasket, i.e. convection on the inner and outer surfaces and adiabatic surfaces at the flange/foam and case/foam surfaces. A second set of calculations in which foam was assumed to conduct heat through the cabinet and door adjacent to the gasket region was also performed. The model for this analysis is shown in Figure 5. The results of the calculations for the 00 to 90°F temperature extremes and heat transfer coefficients of 2 Btu/(hr*ft2*OF) differ by approximately two percent, see Table 4. The temperature profiles for the gasket region with adiabatic flange/foam surfaces are shown in Figures 6.

9 

### the metal case over the gasket shown in Figure 1, had an insignificant effect onthe temperatureprofile, as shown in Figure 4. The minor changes which occurred were primarily in the higher temperature isotherms and the overall heat transfer coefficient increased by less than one percent to 4.069E-3 Btu/(hr*in*oF) at surface heat transfer coefficients of 2 

### Btu/(hr*ft2*oF). The overall heat transfer coefficient increased by about 0.03 Btu/(hr*in*oF) and the percentage of heat flow through the flanges and clip increasedby about 0.1 percent regardless ofthe surfaceheat transfer coefficients. GE Gasket

- The GE gasket, shown in Figure 2, 

### consists of the same materials as the SubZero gasket. Calculations weremade with boundary conditions similarto those for the SubZero gasket, i.e. convection on the inner and outer surfaces and adiabatic surfaces at the flange/foam and case/foam surfaces. Asecond set of calculations inwhich foamwas assumedto conductheat through the cabinet and door adjacent to the gasket region was also performed. The model for this analysis is shown in Figure 5. The results of the calculations for the 0° to 90°F temperature extremes and heat transfer coefficients of 2 

### Btu/(hr*ft2*oF) differ by approximately two percent, see Table 4. The temperature profiles for the gasket region with adiabatic flange/foam surfaces are shown inFigures 6.

9Figure 4. Temperature profiles in SubZero gasket without its decorative cover at 00 and 90°F temperature extremes and heat transfer coefficients at the inner and outer surfaces of 2 Btu / (hr*ft2*°F).

10 Figure 4. Temperature profiles in SubZero gasket without its decorative cover at 0° and gooF temperature extremes and heat transfer coefficients at the inner and outer surfaces of 2 Btu / (hr*ft2*oF).

10Figure 5. Finite element model for the GE gasket including the foam in the door and cabinet adjacent to the flanges.

11 Figure 5. Finite elementmodel for the GE gasket including the foam in the door and cabinet adjacent to the flanges.

11Figure 6. Temperature profiles in GE gasket with 00 and 90°F temperature extremes and heat transfer coefficients at the inner and outer surfaces of 2 Btu / (hr*ft2*OF).

12 Figure 6. Temperatureprofiles in GE gasket with 0° and gooF temperature extremes and heat transfer coefficients at the inner and outer surfaces of 2 Btu / (hr*ft2*oF).

12Table 4. Effect of Flange/Foam Boundary Condition on Overall Gasket Heat Transfer Coefficient Flange/Foam Overall Heat Overall Heat Heat Transfer Transfer Rate Trans. Coef f . , U Assumption Btu/(hr*in) Btu/(hr*in*°F) GE adiabatic 0.5940 6.600E-3 conduction 0.5810 6.456E-3 SubZero adiabatic 0.3632 4.036E-3

Heat flow through the metal flanges was again approximately 20 percent of the total. The rate from the cabinet flange was nearly identical to that for the Subzero gasket. The rate for the door flange was nearly four times higher. This was as ex-. pected, however, as the door flange extended beyond the gasket into the R/F and increased its surface area for convection by about a factor of four. Convection from the appendage on the inside of the R/F near the cabinet side on the GE gasket accounted for about 25 percentof the total heat flow through the gasket/flange region. Excluding heat flow from the flanges and the appendage yields a total heat flux of 0.3217 Btu/(hr*in). This rate is twelve percent higher than that for the SubZero gasket, excluding heat flow through the metal clip and flanges. The GE gasket was 16 percent thicker than the SubZero gasket. Thus comparable heat flow rates per unit thickness'would occur, if the gaskets had similar cross sections.

13 

### Table 4. Effect of Flange/FoamBoundary Condition on Overall Gasket Heat Transfer Coefficient Flange/Foam Overall Heat Overall Heat Heat Transfer TransferRate Trans. Coeff.,

Assumption Btu/(hr*in) Btu/(hr*in*oF) GE adiabatic 0.5940 6.600E-3 conduction 0.5810 6.456E-3 SubZero adiabatic 0.3632 4.036E-3 U



### Heat flow through the metal flanges was again approximately 20 percent of the total. The rate from the cabinet flange was nearly identical to that for the SubZero gasket. The rate for the door flange was nearly four times higher. This was as expected, however, as the door flange extended beyond the gasket into the R/F and increased its surface area for convection by about a factor of four. Convection from the appendage on the inside of the R/P near the cabinet side on the GE gasket accounted for about 25 percent of the total heat flow through the gasket/flange region. Excluding heat flow from the flanges and the appendage yields a total heat flux of 0.3217 Btu/(hr*in). This rate is twelve percent higher than that for the SubZero gasket, excludingheat flow through the metal clip and flanges. The GE gasket was 16 percent thicker than the SubZero gasket. Thus comparable heat flow rates per unit thickness'would occur, if the gaskets had similar cross sections.

13FEA RESULTS - NEW DESIGNS

Modifications to the current gasket designs including changing the gas inside the gasket and changing the flange design were evaluated. The results of these calculations are presented below. Low Conductivity Gas - Low conductivity gases, such as krypton, have been proposed as alternatives to polyurethane foams insulation materials. (3) If the air pockets within the gasket contribute significantly to reduce the U-value of the gasket, switching the gas within these pockets to a low conductivity gas could significantly reduce the U-value of the gasket. The modified SubZero and GE gasket designs showing the pockets which contain low conductivity gas are presented in Figures 7 and 8 . A comparison of the U-values with air and with krypton in these pockets is shown in Table 5. The conductivity of krypton was assumed to equal 0.067 (Btu*in)/(hr*ft2*°F), or about 37 percent that of air, and heat transfer coefficients of 2 Btu/(hr*ft2*°F) were used for these calculations.

Table 5. Comparison of U-values for Gaskets containing

Air and Krypton
G k t U-Value [Btu/(hr*in*OF)] containing as e Air Krypton SubZero 4.036E-3 3.859E-3 GE 6.600E-3 6.180E-3

14 FEA RESULTS

- NEW DESIGNS

Modifications to the current gasket designs including changing the gas inside the gasket and changing the flange design
were evaluated. The results of·these calculations are presented below. Low Conductivity**~** - Low conductivity gases, such as krypton, have beenproposed as alternatives topolyurethane foams insulationmaterials. (3) If the airpockets within the gasket contribute significantly to reduce the U-value of the gasket, switching the gas within these pockets to a low conductivity gas could significantlyreduce theU-value of the gasket. The modified SubZero and GE gasket designs showing the pockets which contain low conductivity gas are presented in Figures 7 and 8. A comparison of the U-values with air and with krypton in these pockets is shown in Table 5. The conductivity of krypton was assumed to equal 0.067 (Btu*in)/(hr*ft2*OF), or about 37 percent that of air, and heat transfer coefficients of 2 Btu/(hr*ft2*OF) wereused for these calculations.

Table 5. Comparison of U-values for Gaskets containing Air and Krypton U-Value [Btu/(hr*in*oF)] containing Gasket Air Krypton SubZero 4.036E-3 3.859E-3 GE 6.600E-3 6.180E-3

14Figure 7. Finite element model and temperature profiles for modified SubZero gasket containing a low conductivity gas (white areas within gasket).

15 Figure 7. Finite element model and temperature profiles for modified SubZero gasket containing a low conductivity gas (white areas within gasket).

15Figure 8. Finite element model and temperature profiles for modified GE gasket containing a low conductivity gas (white areas within gasket).

16 Figure 8. Finite elementmodel and temperature profiles for modified GE gasket containing a low conductivity gas (white areas within gasket)
.

16The overall SubZero and GE gasket heat transfer coefficients

were reduced by 4.4 and 6.4 percent, respectively. While-the reductions are significant, it is relatively small compared to the 63 percent reduction in the thermal conductivity of the gas in the pockets
. As pointed out earlier, the temperature profiles within the gasket indicate that heat flows down the metal flanges and then across the inner portion of the gasket
. Thus, changing the rate of heat flow through the flanges and not the thermal resistance of the gasket by changing the gas within it, should have a larger impact on the gasket

-region U-value. Flange Modifications - The hypotheses that heat flow down the flanges was of primary importance to the overall heat flow problem was tested by uncoupling the flanges from the SubZero gasket. This was accomplished in the model by "inserting" an adiabatic surface between the flanges and the gasket
. The result was a nearly 50 percent reduction in the U-value of the gasket region, see Table 6.

Table 6. Comparison of U-values for the SubZero Gasket

with Coupled and Uncoupled Flanges

t Ga k U-Value [Btu/(hr*in*°F)] containing s e Air Krypton coupled 4.036E-3 3.859E-3 uncoupled 2.139E

-3 1.949E-3

The temperature profiles for the uncoupled model presented in Figure 9 show that heat must now flow through the gasket when the flanges are uncoupled from the gasket. Furthermore, while

17 The overall SubZero and GE gasket heat transfer coefficients
were reduced by 4.4 and 6.4 percent, respectively. While'the reductions are significant, it is relatively small compared to the 63 percent reduction in the thermal conductivity of the gas in the pockets. As pointed out earlier, the temperatureprofiles within the gasket indicate thatheat flows down the metal flanges and then across the inner portion of the gasket. Thus, changing the rate of heat flow through the flanges and not the thermal resistance of the gasket by changing the gas within it, should have a larger impact on the gasket-regionU-value. Flange Modifications

- The hypotheses that heat flow down the flanges was of primary importance to the overall heat flow problem was tested by uncoupling the flanges from the SubZero gasket. This was accomplished in the model by "inserting" an adiabatic surface between the flanges and the gasket. The result
was a nearly 50 percent reduction in the U-value of the gasket region, see Table 6.

Table 6. Comparison of U-values for the SubZero Gasket with Coupled and Uncoupled Flanges U-Value [Btu/(hr*in*oF)] containing Gasket Air Krypton coupled 4.036E-3 3.859E-3 uncoupled 2.139E-3 1.949E-3

The temperature profiles for the uncoupled model presented in Figure 9 show that heat must now flow through the gasket when the flanges are uncoupled from the gasket.- Furthermore, while
17Figure 9. Finite element model and temperature profiles foruncoupled heat flow,in modified SubZero gasket. (Adiabatic surfaces between flanges and gasket not shown.)

18 Figure 9. Finite element model and temperature profiles for uncoupledheat flow"inmodified SubZero gasket. (Adiabatic surfaces between flanges and gasket not shown.)

18uncoupling reduced the U-value by about a factor of two, replacing the air within the gasket with krypton reduces the U-value by. only an additional ten percent. Uncoupling heat flow between the flanges and gasket can not, in practice, be accomplished by placing adiabatic surfaces between the flanges and gasket. Replacing the metal clip which holds the gasket in place and part of the metal flanges with plastic as shown in Figures 10 and 11 could be implemented in production and could produce the same result. Modifications to the SubZero gasket region shown in Figure 10 include changing the metal retaining clip to plastic, changing the portion of the door flange between the mounting socket and interior of the R/F to plastic and changing the portion of the cabinet flange between the end of the gasket magnet and interior of the R/F to plastic. The U-value resulting for the modified gasket region was 1.775E

-3 Btu / (hr*in*°F), a nearly 60 percent reduction. As it may not be possible to make such drastic changes in practice on all models, calculations were performed for flangedesigns which embodied a fraction of the above described modifications. U

-values which resulted from changing the clip and/or a fraction of the above metal portions of the flanges to plastic are summarized in Table 7 and plotted in Figure 12.

19 uncoupling reduced the U-value by about a factor of two, replacing the airwithin the gasketwithkryptonreduces the U-value by
. only an additional tenpercent. Uncouplingheat flow betweenthe flanges and gasket can not, in practice, be accomplished by placing adiabatic surfaces between the flanges and gasket. Replacing the metal clip which holds the gasket in place and part of the metal flanges with plastic as shown in Figures 10 and 11 could be implemented in production and couldproduce the same result. Modifications to the SubZero gasket region shown in Figure 10 include changingthemetal retaining cliptoplastic, changing the portion of the door flange between the mounting socket and interior of the R/F to plastic and changing the portion of the cabinet flange between the end of the gasket magnet and interior of the R/F to plastic. The U-value resulting for the modified gasket region was 1.77SE-3 Btu / (hr*in*oF), a nearly 60 percent reduction. As it may not be possible to make such drastic changes in practice on all models, calculations were performed for flange designs which embodied a fraction of the above described modifications. U-values which resulted from changingthe clip and/or a fraction of the above metal portions of the flanges to plastic
are summarized in Table 7 and plotted in Figure 12.

19Figure 10. Finite element model and temperature profiles for modified SubZero gasket region which includes a plastic clip and approximately half plastic door and cabinet flanges.

20 Figure 10. Finite element model and temperature profiles for modified SubZero gasket region which includes a plastic clip and approximatelyhalf plastic door and cabinet flanges.

20Figure 11. Finite element model and temperature profiles for modified GE gasket region which includes a plastic clip and approximately half plastic door and cabinet flanges.

21 Figure 11. Finite element model and temperature profiles for modified GE gasket region which includes a plastic clip and approximatelyhalf plastic door and cabinet flanges.

21

### 60 7

W 

### 50 O



### 30-I 0



### 0.25 0

.50 0.75 1.00 

# . Fraction Plastic 1.25

Figure 12. SubZero gasket region load reductions for various

flange modifications. Door & Cabinet

22 

### Figure 12. SubZerogasketregion loadreductions for various flange modification"s.

22Table 7. U-Values for SubZero Gasket Region with a Portion of the Flanges changed to Plastic % Proposed Modification U- l % Reduction va ue clip I door I cabinet 0 0 0 4.036E-3 0 100 0 0 3.977E-3 1.5 100 25 0 3.677E-3 8.9 100 50 0 3.409E-3 15.5 100 75 0 3.240E-3 19.7 100 100 0 3.138E-3 22.2 100 0 25 3.459E-3 14.3 100 0 50 3.114E-3 22.8 100 0 75 2.905E-3 28.0 100 0 100 2.780E-3 31.1 100 25 25 3.151E-3 21.9 100 50 50 2.504E-3 38.0 100 75 75 2. 068E-3 48.8 100 100 100 1.775E-3 56.0
Changing the metal clip to plastic has a relatively small effect of 1.5 percent. Changing either the door or cabinet flange can reduce the heat flow by approximately 25 percent. Similarly making half of the proposed changes to the door and cabinet flanges will produce almost a 40 percent reduction. The effects are also additive as shown by the open circles in Figure 12, which correspond to the sum of the individual reductions. (Note: When adding values in Table 7, 1.5% must be subtractedfrom the sum so that the effect of the clip is not double counted.) Modifications to the GE gasket region consisted of changing the clip from metal to plastic, changing the portion of the door flange from the center of the clip to the interior of the R/F from metal to plastic and changing the portion of the cabinet flange from the center of the clip to the interior of the R/F from metal to plastic. Similar reductions to those for the

23 

### Table 7. U-Values for SubZeroGasketRegionwith a Portion of the Flanges changedto Plastic % ProposedModification U-value %Reduction clip door cabinet

0 0 0 4.036E-3 0 100 0 0 "3.977E-3 1.5 100 25 0 3.677E-3 8.9 100 50 0 3.409E-3 15.5 100 75 0 3.240E-3 19.7 100 100 0 3.138E-3 22.2 100 0 25 3.459E-3 14.3 100 0 50 3.114E-3 22.8 100 0 75 2.905E-3 28.0 100 0 100 2.780E-3 31.1 100 25 25 ." 

### 3.151E-3 21.9 100 50 50 2.504E-3 38.0 100 75 75 2.068E-3 48.8 100 100 100 1.775E-3 56.0 Changing the metal clip to plastic has a relatively small effect of 1.5 percent. Changing either the door or cabinet flange can reduce the heat flow by approximately 25 percent. Similarly making half of the proposed changes to the door and cabinet flanges will produce almost a 40 percent reduction. The effects are also additive as shown bythe open circles in Figure 12, which correspond to the sum of the individual reductions. (Note: When adding values in Table 7, 1.5% must be subtracted from the sum so that the effect of the clip is not double counted.) Modifications to the GE gasket region consisted of changing the clip from metal to plastic, changing the portion of the door flange from the center of the clip to the interior of the R/F from metal to plastic and changing the portion of the cabinet flange from the center of the clip to the interior of the R/F from metal to plastic. Similar reductions to those for the 23Subzero gasket are shown in Table 8 and Figures 13.

Table 8. U

-Values for GE Gasket Region with a Portion of

the Flanges changed to Plastic % Proposed Modification U-v lu % R d ti a e uc on

e clip I door I cabinet 0 0 0 6.600E-3 0 100 0 0 6.382E-3 3.3 100 25 0 6. 015E-3 8.9 100 50 0 5.304E-3 19.6 100 75 0 5.040E-3 23.6 100 100 0 4.865E-3 26.3 100 0 25 5.479E-3 17.0 100 0 50 5.022E-3 23.9 100 0 75 4.790E-3 27.4 100 0 100 4.695E-3 28.9 100 25 25 5.110E-3 22.6 100 50 50 3. 923E-3 40.6 100 75 75 3.376E-3 48.8 100 100 100 3. 070E-3 53.5

As with the SubZero gasket, the clip has a minor effect on the U

-value, a 3.3 percent reduction. Modifications to the door flanges produced up to a 26 percent reduction, and up to 29 percent reductions were calculated for modifications to the cabinet only. Reductions of over fifty percent were, also, possible and the reductions were cumulative, as shown by the open circles in Figure 13. A final calculation was made to determine if heat flow through the foam adjacent to the flanges would significantly affect the reductions described above. A model similar to that shown in Figure. 5 but with the clip and portions of the flangesdescribed above changed to plastic, was employed in this calculation. As shown in Table 9, including the heat flow through the

24 SubZero gasket are shown inTable 8 and Figures 13.

Table 8. U-Values for GE Gasket Region with a Portion of the Flanges changedto Plastic % ProposedModification U-value 9,- 0 Reduction clip door cabinet

0 0 0 6.600E-3 0 100 0 0 6.382E-3 3.3 100 25 0 6.015E-3 8.9 100 50 0 5.304E-3 19.6 100 75 0 5.040E-3 23.6 100 100 0 4.865E-3 26.3 100 0 25 5.479E-3 17.0 100 0 50 5.022E-3 23.9 100 0 75 4.790E-3 27.4 100 0 100 4.695E-3 28.9 100 25 25 5.110E-3 22.6 100 50 50 3.923E-3 40.6 100 75 75 3.376E-3 48.8 100 100 100 3.070E-3 53.5

As with the SubZero gasket, the clip has a minor effect on the U-value, a 3.3 percent reduction. Modifications to the door flanges produced up to a 26 percent reduction, and up to 29 percent reductions were calculated for modifications to the cabinet only. Reductions of over fifty percent were, also, possible and the reductions were cumulative, as shown by the open circles in Figure 13. A final calculation was made to determine if heat flow through the foam adjacent to the flanges would significantly affect the reductions described above. Amodel similar to that shown in Figure 5 but with the clip and portions of the flanges described above changed to plastic, was employed in this calculationa As shown in Table 9, including theheat flow through the 24

### 60 --1 Door & Cabinet

30-I

0 -i ,f 0.00 Cabinet Only

0.25 0

.50 0.75 1.00 

# Fraction Plastic 1.25

Figure 13. GE gasket region load reductions for various flange

modifications.

25 

### 60 

## tR Door & 

### Cabinet**~** 0**~** 

### 50 0 0 .1""'"1**~.**

() 

### ;::J 40 

### 'D Q) 

### 0::: 'D cd 30 

### Cabinet Only 0**~** 

### Door Only**~** 

### 20 0 .1""'"1

OJ) Q)**~** 

### 10**~** Q)**~** lfl 

### 0 

### cd 0.00 0.25 0.50 0.75 1.00 1.25 C,) 

# Fraction Plastic
Figure 13. GE gasket region load reductions for various flange modifications.

25foam adjacent to the door and cabinet flanges increased the Uvalue of the gasket region by less than 2 percent.
Table 9. Effect of Flange/Foam Boundary Condition on

U-Value of Modified GE Gasket Region Flange/Foam Overall Heat Overall Heat Heat Transfer Transfer Rate Trans. Coeff., U Assumption Btu/(hr*in) Btu/(hr*in*OF) adiabatic 0.2763 3. 070E-3 conduction 0.2801 3.119E-3

MEASUREMENTS
- NEW DESIGNS

A method to measure the total heat flux through the gasket region of a R/F cabinet does not exist
. Measurements of the total energy consumption of two prototype R/Fs were thus used in conjunction with the EPA Refrigerator Analysis (ERA) model (4) to determine if the predicted energy reductions could be achieved in practice. Both prototypes had gasket cross sections similar to the Subzero gasket, but neither had the decorative metal gasket cover shown in Figure 1. Other notable differences to the model shown in Figure 1 were that the cabinet flange was not as wide as the gasket for both prototypes and that the plastic liner and not a metal clip was used to hold the gasket in place in prototype B. Prototype A - The cabinet flange for this unit ended at the inside edge of the gasket magnet as is shown in Figure 10. The remainder of the flange was, however, not plastic but rather a small air gap. Still air would produce the same effect as having

26 foam adjacent to the door and cabinet flanges increased the Uvalue of the gasket regionby less than 2 percent. Table 9. Effect of Flange/FoamBoundary Condition on U-Value ofModified GE GasketRegion Flange/Foam Overall Heat Overall Heat Heat Transfer TransferRate Trans. Coeff.,

Assumption Btu/(hr*in) Btu/(hr*in*oF) adiabatic 0.2763 3.070E-3 conduction 0.2801 3.119E-3

MEASUREMENTS

- NEW DESIGNS U

Amethod to measure the total heat flux through the gasket region of a R/F cabinet does not exist. Measurements of the total energy consumption of two prototype R/Fs were thus used in conjunctionwith the**~PA** RefrigeratorAnalysis (ERA) model (4) to determine if thepredicted energyreductions could be achieved in practice. Both prototypes had gasket cross sections similar to the SubZero gasket, but neither had the decorativemetal gasket cover shown in Figure 1. Other notable differences to the model shown in Figure 1 were that the cabinet flange was not as wide as the gasket for both prototypes and that the plastic liner and not a metal clipwas used tohold the gasket inplace inprototype B. Prototype A - The cabinet'flange for this unit ended at the inside edge of the gasket magnet as is shown in Figure 10. The remainder of the flange was, however, not plastic but rather a small air gap. still airwouldproduce the same effect as having

26plastic in this region
. If, however, convection to the R/F

interior occurred in this gap, the flange would behave exactly as that shown in Figure 1. The exact configuration shown in Figure 10 was then easily obtained by placing plastic insulating tape between the end of the metallic flange and the inside of the R/F. No modifications were made to the door flange in prototype A. The calculations presented in Table 7 suggest that a 30 percent decrease in the total heat flux for the gasket region would results from this modification, if convection was present in the air gap. Reducing the gasket heat load by this amount in the ERA model predicted a 9 percent energy reduction
. Measurements yielded 7 to 8 percent. The agreement between the measurement and models is very good. It is possible even better agreement would be obtained by employing a lower heat transfer coefficient in the air gap. This would be warranted, as some restriction to air flow is likely. Prototype B - The door flange was changed in this unit by removing the portion of the flange located under the gasket and between the liner mounting screws
. This portion of the flange accounts for about 80 percent of the heat transfer path and should produce about that fraction of the 22 percent reduction for this modification shown in Table 7. Reducing the gasket heatflow by this amount in the ERA model predicted a 5 percent reduction in total energy consumption for this unit
. This result is in excellent agreement with the 4 to 5 percent that was measured. The cabinet flange in this model was similar to that in prototype A, i. e. it did not extend the entire length of the gasket. It did, however, extend beyond the magnet approximately

27 

### plastic in this region. If, however, convection to the 

### RIF interior occurred inthis gap, the flange would behave exactly as that shown in Figure 1. The exact configuration shown in Figure 10 was then easily obtained by placing plastic insulating tape betweenthe end of themetallic flange and the inside of the

### R/F. No modifications weremade to the door flange inprototypeA. The calculations presented in Table 7 suggest that a 30 percent decrease in the total heat flux for the gasket region would results from this modification, if convection was present in the air gap. Reducing the gasket heat load by this amount in the ERA model predicted a 9 percent energy reduction. Measurements yielded 7 to 8 percent. The agreement between the measurement and models is very good. It is possible even better agreement would be obtained by employing a lowerheat transfer coefficient in the air gap. This would bewarranted, as some restriction to air flow is likely. Prototype**~** 

### - The door flange was changed inthis unit by removing the portion of the flange located under the gasket and between the liner mounting screws. This portion of the flange accounts for about 80 percent of the heat transfer path and should produce about that fraction of the 22 percent reduction for this modification shown inTable 7. Reducing the gasketheat flow bythis amount inthe ERA model predicted a 5 percent reduction in total energy consumption for this unit. This result is in excellent agreement with the 4 to 5 percent thatwas measured. The cabinet flange in this model was similar to that in prototype A, i. e. it did not extend the entire length of the gasket. It did, however, extend beyond the magnet approximately 27one sixth of the way in the freezer and one third of the way in

the fresh food section. As with prototype A, plastic tape was employed to fill in the air gap in both the freezer and fresh food sections. Table 7 would suggest an 18 percent reduction for the fresh food section and a 30 percent reduction for the freezer section
. As this modification was done after the door flange was changed the total reductions should be 36 and 48 percent. The ERA model was again used to simulate the R/F with the reduced gasket heat input and predicted an.11 percent energy reduction
. Measurements showed a 7 to 8 percent reduction. As noted above, better agreement would have been attained with a lower convective heat transfer coefficient in the air gap. Agreement was, however, quite good.

CONCLUSIONS

• Heat flow through the gasket region of refrigerator/freezers is modeled using finite element analysis. • Heat flow through the gasket and flanges is highly coupled. • Decreasing the thermal resistance of the gasket by incorporating a low conductivity gas in the pockets of the gasket has a modest effect on the gaskets thermal performance. • Replacing about half of,either the metal door flange or cabinet flange with plastic can reduce the heat flow through the region by 25 percent. Replacing about half of the door and cabinet flanges with

28 

### one sixth of the way in the freezer and one third of the way in the fresh food section. As with prototype A, plastic tape was employed to fill in the air gap in both the freezer and fresh food sections. Table 7 would suggest an 18 percentreduction for the fresh food section and a 30percentreduction for the freezer section. As this modificationwas done afterthe door flange was**chan~ed** 

### the total reductions shouldbe 36 and 48 percent. The ERA model was again used to simulate the R/F with the reduced gasket heat input ahd predicted an.11 percent energy reduction. Measurements showed a 7 to 8 percent reduction. As noted above, better agreement would have been attained with a lower convective heat transfer coefficient in the air gap. Agreementwas, however, quite good.

CONCLUSIONS



### Heat flow throughthegasketregion of refrigerator/freezers ismodeled using finite element analysis. Heat flow through the gasket and flanges ishighly coupled. Decreasing the thermal resistance of the gasket by incorporating a lowconductivitygas inthepockets of the gasket has a modest effect on the gaskets thermal performance. Replacing about half of·either themetal door flange or cabinet flange withplasticcanreduce the heat flow through

the region by 25 percent. Replacing about half of the door and cabinet flanges with

28plastic can reduce the U-value of the gasket region by half.

• Measured and predicted reductions in total R/F energy consumption resulting from modified gasket designs are in good agreement.

ACKNOWLEDGEMENTS The authors wish to thank Mr. Qin Zhou, Mr
. Kwangil Kim, Dr. Sungpil Won and Prof
. Reinhardt Radermacher of the Department ofMechanical Engineering at the University of Maryland for performing the energy testing on the prototype refrigerator/freezers.

REFERENCES
1. H. A. Fine, G
. J. Haworth and R. Srikanth, "Performance Test Results for Refrigerator/Freezers containing Vacuum Insulation Panels", Proceedings of the International Conference on CFCs and Halons, Berlin, Germany, February 24 - 26 , 1992, FGU Berlin, pp. 305 - 15. 2. W. D. Lee, Development of a High Efficiency, Automatic Defrost Refrigerator/Freezer: Phase I - Design and Development, ORNL/Sub-7255/2, Oak Ridge National Laboratory, Oak Ridge, Tenn., 1980. 3. B. T. Griffith, D. Arastah and S. Selkowitz, HighPerformance Non-CFC-Based Thermal Insulation: Gas Filled Panels, California Institute for Energy Efficiency , Berkeley, Calif., 1992. 4. R. L. Merriam, EPA Refrigerator Analysis Program, U.S. Environmental Protection Agency, Washington, DC, 1992.

29 plastic can reduce the U-value of the gasket region byhalf. Measured and predictedreductions intotal R/F energy consumption resulting from modified gasket designs are in good agreement.
ACKNOWLEDGEMENTS The authors wish to thankMr. Qin Zhou, Mr. Kwangil Kim, Dr. Sungpil Won and Prof. Reinhardt Radermacher of the Department of Mechanical Engineering at the University ofMaryland for performingthe energytesting on theprototyperefrigerator/freezers.

REFERENCES 1. H. A. Fine, G. J. Haworth and R. Srikanth, "PerformanceTest Results for Refrigerator/Freezers containing Vacuum Insulation Panels", Proceedings of the International Conference on CFCs and Halons, Berlin, Germany, February 24

- 26, 1992, FGU Berlin, pp. 305

- 15. 2. W. D. Lee, Development of 

### £ High Efficiency, Automatic Defrost Refrigerator/Freezer: Phase I

# = Design and Development, ORNL/Sub-7255/2, Oak Ridge National Laboratory, Oak Ridge, Tenn., 1980. 3. B. T. Griffith, D. Arastah and S. Selkowitz, HighPerformance Non-CFC-Based Thermal Insulation: Gas Filled Panels, California Institute for Energy Efficiency, Berkeley, Calif., 1992. 4. R. L. Merriam, EPA Refrigerator Analysis Program, U.S. Environmental ProtectionAgency, Washington, DC, 1992.

29