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Monday - June 20, 2022

MEMS Sensors Support Efficiency Upgrades for Home Appliances

The cost of energy has risen steadily over the years and has been driven higher recently due to unanticipated events impacting global fuel supplies. This, coupled with the negative effect of fossil fuels on the environment has led to increased interest in energy conservation applications. While electric vehicles typically dominate headlines when it comes to energy conservation and climate change, there are many solutions that can make a big difference behind the scenes.

Improving Refrigerator Defrost Cycles to Maximize Efficiency

Home appliances have become more efficient in the last 20 years as a direct result of tighter energy regulations. However, there are still ways to improve efficiency while also delivering a better user experience. For example, refrigerators used to require periodic, manual defrosting that was very inconvenient for consumers. Today’s models typically utilize an algorithm to trigger an automatic defrost cycle based on the amount of time the door is open, compressor run times and how long it’s been since the last defrost cycle. Some refrigerators also employ thermocouples to sense when ice forms on the evaporator however, this method of detection lacks sensitivity which makes it highly inefficient.

Thermocouples are typically mounted to an evaporator with a metal clip and is used to detect when the temperature of the evaporator core drops to freezing. The problem with this approach is that frost does not accumulate uniformly on the evaporator which makes it difficult to detect accurate freezing temperatures with a thermocouple.

MEMS Sensors Enable Precise Measurement in a Compact Package

To improve efficiency, the refrigerator should be able to precisely determine when the evaporator actually needs to be defrosted. An alternative approach is to measure air flow changes across the evaporator using a refrigeration pressure sensor or differential pressure sensor. At a constant fan speed, an unobstructed evaporator would have a pre-determined pressure drop value. As ice accumulates, it lowers the air flow through the evaporator thus, pressure increases in front of the evaporator while decreasing behind the evaporator. This shift in pressure can be measured using a low differential pressure sensor capable of detecting changes in Pascal.

This solution has only been possible with recent advances in MEMS technology and manufacturing. In the past, low differential pressure sensors were too bulky and expensive to be used in home appliances. MEMS technology has enabled manufacturers to shrink both the size and cost of these sensors making them ideal for compact designs. Our local product engineers can help design a refrigeration pressure sensor to improve energy efficiency while maintaining cooling performance.

Differential Pressure Sensor Applications in Home Appliances

Other appliances can also benefit from the addition of low differential pressure sensor such as clothes dryers. For this application the sensor can be used to notify users when lint builds up in the system and decreases drying efficiency. Stay tuned for the next blog post in this series to learn more about integrating differential flow sensors in clothes dryer applications.

Ohlan Silpachai
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