Appliance Design - April 2008 - (Page 19)

COOLING TECHNOLOGIES Fig. 3. SC-TC04 low cost FPSC. Fig. 2. M100 FPSC. 4Industrial process testers. 4Environmental monitoring equipment. 4Controlled rate freezers targeted at the biotech industry. 4Ultra-low temperature transport and storage freezers. 4The Cryopen, a liquid-nitrogen-free, cryosurgical device used to treat skin lesions through outpatient surgery. FPSCs offer several distinct advantages over conventional cooling and heat pump technologies. At temperatures between –40 DegC/104 DegF and 54 DegC/130 DegF, FPSCs can out-perform other cooling methods in power density, efficiency, performance and environmental friendliness. A typical FPSC has 15 percent to 50 percent less mass than a Rankine system with similar lift capacity. (See Graph 2.) The lowest efficiency FPSCs available today roughly match the heat lift performance of typical vapor-compression units, while the highest performance FPSCs can out perform high-efficiency compressors and double the performance of an average compressor. (See Graph 3.) FPSCs also have the ability to fully modulate their cooling capacity from 100 percent down to nearly 0 percent while maintaining high efficiencies. (See Graph 4.) This ability enables them to use only the amount of power necessary to maintain the set temperature and offset the heat leak into the cooled space. It also eliminates the need to size the system’s electrical capacity for large start-up current demands, while at the same time providing more precise temperature control. This is all accomplished using environmentally benign helium as the www.applianceDESIGN.com refrigerant or working fluid. In addition to those advantages, FPSCs have a virtually unlimited operational ambient temperature and low-temperature capability. The Stirling cycle is theoretically only limited by the temperature range at which the working fluid remains stable in phase. While the operational ambients are limited in practice by the survivability of the materials available, FPSCs have already been designed and built at Global Cooling that demonstrate as much as 150 W of heat lift in a 280 DegC/536 DegF ambient using conventional materials. By transitioning to exotic materials, such as ceramics, it would be possible to significantly increase this ceiling to well above 600 DegC. As for low temperature capabilities, current FPSC designs have acceptor or cold side temperature capabilities ranging from 35 K/-238 DegC/-396 DegF in a 30 DegC/86 DegF ambient to 423 K/150 DegC/302 DegF in a 280 DegC/536 DegF ambient, with heat-lift capacities ranging from fractional Watt to more than 600 W. One way to understand how an FPSC like the M100 can compete in the high temperature cooling market, is to compare it to a Rankine system operating at –100 DegC/-148 DegF with a desired 50 W of heat-lift capacity. (A two-compressor cascade configuration is required for a Rankine system to reach this temperature.) The Rankine system could require an input power exceeding 2 kW to achieve the desired lift capacity while the M100 would require only slightly more than 100 W of power to do the same amount of work. A comparison against a small, single- Fig. 4. Twinbird portable refrigerator/freezer. Fig. 5. Twinbird CoolCargo. applianceDESIGN April 2008 19 http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - April 2008

Appliance Design - April 2008 Contents Editorial Shipments/Forecasts News Watch A Variant of Thermoacoustic Refrigeration Known as Acoustic-Stirling is Expanding Its Range Outside Cryocooling Into More Conventional Applications Such As Refrigeration and Air Conditioning Free-Piston, Stirling Coolers Are Now Showing Up in Mainstream Applications As Costs Come Down and Heat Transport Solutions Are Devised Heat Exchanger Innovations Are Helping To Improve the Overall Efficiency of Vapor Compression Systems Environmental Concerns Have Once Again Ignited a Debate Over Refrigerants A New Glass Ceramic Material for Induction Cooktops Can Be Decorated In a Variety of Glimmering Metallic, 3-D Looks That Can Employ a Number of Shades, Patterns, Styles, Colors, Intensities, and Textures Colorful, Reflective Coatings for Glass Create a Variety of Design Options To Help Designers Establish a Unique Look for Their Products Appliance Designers Faced With Different Motor and Drive Options Need To Understand the Differences and Tradeoffs Before Choosing A New MEMS Valve Offers a Number of Advantages Over Solenoids In Certain Applications, Including the Opportunity To Cut Energy Use The AHR Expo Set Attendance Records and Showcased Thousands of Innovative New Products Classifieds Design Marts Advertiser’s Index Association Report: CEA

Appliance Design - April 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.