Thermal Insulation

Glacier Bay Insulation Testing

Introduction

As mentioned in our General Discussion of Insulation Testing, finding accurate thermal ratings ("R" values) for specific insulation products can be very difficult.  As manufacturers of cooling systems and insulation products as well as thermal engineering consultants, Glacier Bay has found it counterproductive to rely on unverified "R" value claims in designing and specifying equipment for our customers.  For this reason, we maintain our own ongoing test program to accurately quantify the thermal performance of various insulations under the tightly controlled (ASTM 518) conditions.

In releasing this data to the general public is not our intention to either endorse, or discredit, the products or thermal claims of any manufacturer.  Rather, it is our desire that visitors to this site will find a reliable, highly accurate resource for estimating the true effective insulation value of the products tested.  It should be recognized by all viewers that these tests were conducted under thermal conditions which most simulate those which exist in refrigerator and freezer boxes.  The test method used will also be found to moderately resemble the heat transfer characteristics of vehicle passenger compartments and some medical and electronic devices but may not reflect the performance of these insulations in other environments.

The test results are presented in catagories broken down by insulation type and provided in the Test Result Table along with relevant notations. 

Our Test Method - (Scientific)

All testing reported here is conducted in accordance with ASTM 518 standard for "Steady-State Heat Flux Measurements and Thermal Transmission Properties".   Thermocouples are NIST calibrated and accurate to +/- .1 degree C (point one) over the test range.  Test samples are shielded agains edge loss.  To further increase accuracy and eliminate the potential for miscalibration, the Glacier Bay thermal conductivity test instrument is designed so as to describe the performance of test samples in terms continually referenced to the thermal conduction of a NIST standard thermal reference material (SRM 1453).

The test sample size varies from as large as 330mm x 330mm to as small as 260mm x 255mm x 305 mm.  Hot plate temperature is +37.8 degrees C (100 degrees F).  The cold plate temperature is -17.8 degrees C (0 degrees F). 

Our Test Method - (Layman)

In the Glacier Bay thermal conductivity test instrument, an insulation test sample is placed between two temperature controlled plates - one hot and one cold.  Since nearly all insulations vary in "R" value when the temperature rises or falls, these plates are maintained at temperatures which simulate the internal and external temperature of a freezer box in a tropical environment.

The material is held between the two plates until the rate of heat flow (from the hot plate to the cold plate) has stablized.  This can take from 1 to 4 hours depending on the conduction rate of the material.  Once stablized, the rate of heat flow is measured to determine the thermal conductivity (and "R" value) of the test sample.  To ensure maximum accuracy, the test instrument references the resulting "R" value to that of a "known" standard reference material which is tested simultaniously.

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