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Refrigeration Service Today

Liquid Level Sensor Uses Electromagnetic Pulses
Danfoss introduces the AKS 4100U, a new range of adjustable guided radar liquid level sensors for industrial refrigeration applications.

The sensors use time domain reflectometry (TDR) technology to measure liquid levels of many different refrigerants — including ammonia, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs) and carbon dioxide (CO2) —in vessels, accumulators, receivers, and standpipes. The sensors’ signal converters emit low-intensity, high-frequency electromagnetic pulses with a width of approximately one nanosecond.

The pulses travel at the speed of light along the probe to the liquid surface, where they are reflected, guided back along the probe, received and analyzed by the signal converter, and then converted into a liquid level reading. The AKS 4100U sensors are available in two different versions:

A customizable cable version is suitable for all industrial refrigeration applications, except marine applications. It comes with a 197-inch cable, and a probe length that can be adjusted to suit the needs of each customer. As a result, the customer deals with one rather than multiple part numbers. The sensor is available with or without an HMI display unit. The coaxial version is suitable for all industrial refrigeration applications, including marine applications, and can be supplied in a variety of lengths (from 19.2 in. up to 85 in. (500 mm up to 2200 mm).
- Danfoss
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Penn State Researchers Testing Sound Waves and Helium Gas Refrigerant for Conventional Freezers
Penn State University researchers are designing a freezer that substitutes the use of sound waves and helium gas refrigerant for use in conventional freezers. Called a thermoacoustic chiller, the technology is based on the fact that the pressure oscillations in a sound wave result in temperature changes. Areas of higher pressure raise temperatures, and areas of low pressure decrease temperatures. By carefully arranging a series of heat exchangers in a sound field, the chiller isolates the hot and cold regions of the sound waves. The natural properties of helium are favorable for this application, because it doesn’t burn, explode, or combine with other chemicals. Penn State is working to apply this technology on a large scale. Heatcraft Refrigeration is a partner organization.

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