Low temperature defrost cycle.
GE Call for Innovation
LOW-TEMPERATURE INTRINSICALLY SAFE DEFROST SYSTEM
Nearly 100% of US household refrigerators use R-134a as a refrigerant. However, in many other countries throughout the world, R-600a (isobutane) is used. The benefits of R-600a include: 1) significantly lower global warming potential (GWP), 2) typically lower sound level, and 3) lower energy usage (approximately 4%). The technical specifications and service procedures required to use R-600a as a refrigerant in the US have been developed. Nevertheless, the current barrier-to-entry for manufacturers to use R-600a is the cost of complying with UL 250 (Standard for Safety for Household Refrigerators and Freezers) to ensure customer safety. Specifically, because R-600a is an A3 refrigerant (i.e., low toxicity and high flammability) all electrical devices need to be spark resistant and no surface temperature should exceed 680°F.
During operation of a refrigerator, moisture from the air condenses and freezes on the evaporator. For the forced convection (frost-free) products that make up the entire population of US primary household refrigerators, a defrost heater is used to remove this frost from the evaporator coil. The heater is cycled at regular intervals to maintain cooling performance. In a typical configuration, a defrost heater is placed between the evaporator and a drain pan. The defrost heater warms the evaporator and melts the frost until a pre-determined temperature is reached. The melt water is removed from the refrigerator via a drain line connected to the drain pan. While effective, surface temperatures of the defrost heater may reach 1000 to 1400°F.
The challenge is to develop a low-cost system to remove ice from the evaporator while conforming to UL 250 Flammable Refrigerants Addendum. Specifically, the defrost system
- Must not require substantial physical changes to the existing evaporator or evaporator compartment
- Must meet standard 20-year life requirements (assume 1 defrost per day)
- Must be able to raise an unfrosted evaporator from -10°F to 40°F in 15 minutes or less
- Must be spark resistant and surface temperatures should not exceed 680°F.
- Should be able to raise an unfrosted evaporator from -10F to 40F in 15 minutes or less.
A cash award of $3,000 will be sponsored by GE for the top selected technology submission. The idea submitter will also be invited to discuss future collaboration with GE and ORNL technical experts. Depending on the needs identified:
- ORNL may provide in-kind technical support of $10,000 - $20,000 to enable ORNL staff to provide prototype development, testing, 3rd party validation, or other defined needs.
- Participation in the DOE Small Business Voucher (SBV) pilot will also be discussed; ORNL may provide in-kind technical support of up to $300K through the SBV program, if SBV approved.
Idea Submission Deadline
Idea Submission Period Ends: Friday, April 8, 2016 at 11:59 PM EST
Why can't external air temperature be utilized to cool and defrost refrigerant units? Consider the ramifications in most every climate in the world.
Reducing temperature in defrost cycle to allow use of R-600a
The challenge is to develop a low-cost system to remove ice from the evaporator while conforming to UL 250 Flammable Refrigerants Addendum.
Summary We describe a low-cost system using current technology for deicing an evaporator while conforming to the UL 250 flammable refrigerants addendum. The system uses light emitting diode arrays to radiatively transfer energy to the ice without requiring heating above 680◦F, as with resistively heated thermal radiators. Description Typically heaters for evaporator defrosting consist of a resistively heated filament ...more »
Air conditioner condensers suffer a large loss of performance at above 100F. High SEER AC units do not cool well at 100F as they are designed for the 82F of the SEER test. They often use undersized compressors to lower energy draw and oversized condensers to provide cooling capacity. This works ok at the 82F test but once 100F is reached they often perform less than the older unit they replace. And the new R 410 ...more »
after my knowledge of the profession, and when there is a defrost problem, the first sollution that I use before surgery is pulvirisation with tap water, so my sollution will be based on the spraying of hot water on the evaporator, a stainless steel tray on the top of the compressor is sufficient to heat the amount of water needed. when the defrost cycle has arrived hot water will be sprayed into the evaporator using ...more »