As a general understanding from home appliance market, the consumers wish to purchase refrigerators/freezers with large storage volume, high-energy efficiency, good food freshness maintaining ability, low noise and deodorizing function. Door openings would affect the increase of energy consumption and thus reduced food freshness, which make direct impact to refrigerator/freezer performance. Therefore, the door opening/closing effect is truly a major concern to many consumers, and there were many literatures to study this effect in the past decades. Japanese refrigerator test standards [5] and [6] include door-opening method, which does not appear in other national testing standards of household refrigerators/freezers. From the website of National Consumer Affairs Center of Japan (NCAC)