Document Type

Restricted Campus Only

Publication Date

4-2013

Abstract

The objective of this project is to decrease the amount of energy consumed by a refrigerator to one quarter of the Federal Standards for a refrigerator of comparable size. In order to achieve this, it was determined that a GE 5 ft3 chest freezer would be converted into a refrigerator rather than starting with an upright refrigerator as the baseline. After the base for the project was determined, a number of modifications were determined to improve the energy efficiency of the prototype. Firstly, the standard foam insulation was replaced with 8 vacuum insulation panels purchased from ThermalVisions. Additionally, a thermostat control kit, manufactured by Johnson Controls, was purchased and installed to allow the prototype to run at refrigeration temperatures (2 to 5°C) unlike the original, freezing temperatures (-15 to -25°C). Finally, sliding doors were added to act as an added layer of insulation when the appliance is in use, and to decrease the amount of heat transfer during opening and closing of the appliance door. Although additional modifications, such as fins and fans were originally postulated, the addition of said modifications was deemed infeasible due to time constraints.

Testing was performed for each modification made to the prototype. In order to verify results, two rounds of testing were completed. Tests were performed to determine how much energy the prototype consumed, as well as to identify the temperature profile within the prototype over time in a number of situations: when the appliance was cooling down from room temperature, when the appliance was operating at steady state conditions, and when it was opened frequently. Tests were completed on the original design and on the modified designs. Initially, once the insulation had been modified, the design temperature of the freezer could not be reached and the compressor continued to run until the appliance was unplugged, unlike the typical on/off cycle of the compressor. Due to the inconclusiveness of the tests with the modified chest freezer, an additional, identical chest freezer was purchased, and testing resumed with the thermostat acquired from Johnson Controls and the new chest freezer. The issue of the insulation was later resolved tlu·ough bleeding out some of the refrigerant to a new operating pressure of 7mmHg (from lOmmHg). This resolved the issue, and testing was again done on the modified prototype with the new insulation.

The original appliance operating at freezing conditions had a compressor cycle that averaged at 100 minutes with the compressor on for 32 minutes per cycle, and the power consumed was calculated to be 301 kW-lu·/yr. The final prototype with all the modifications operating at refrigeration temperatures has a compressor cycle averaged at 150 minutes with the compressor on only about 11 minutes per cycle, and the power consumed is calculated to be 122 kW-lu-/yr.

Comments

Mr. Alex Bernardo, Advisor

ENGR-4381

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