Go to the Acoustics' website Go to the Penn State Thermoacoustics website Go to Penn State's website Home

 

SETAC project: Shipboard Electronics Thermoacoustic Chiller

SETAC was used to cool the CV-2095 Radar Azimuth Converter (two racks of electronics) on board the USS Deyo (DD-989), a Spruance-class destroyer in the Atlantic Fleet. SETAC was installed on Easter Sunday, 1995, in Norfolk, VA, and was removed in Annapolis, MD one week later.

History

The Shipboard Electronics ThermoAcoustic Chiller (SETAC) started out as a NASA-funded project to replace the Life Sciences Laboratory Experiment Refrigerator/Freezer (LSLE). The LSLE was installed in the Life Sciences Module on the mid-deck of the Space Shuttle and employed a mist-lubricated Freon 502 vapor-compression unit to provide refrigeration for cold storage of biological samples in the temperature range from 4 °C (39 °F) to -22 °C (-8 °F). The LSLE was capable of absorbing heat at the rate of 700 BTU/hr (205 W) at the higher temperature and 400 BTU/hr. (117W) at the lower temperature with a steady-state electrical power consumption 450W. This refrigerator was unreliable and some countries refused to use it in their experiments.

The thermoacoustic replacement for the LSLE was to be the ThermoAcoustic Life Sciences Refrigerator (TALSR). To provide redundancy, TALSR was to have two electrodynamic loudspeakers driving opposite ends of a half-wavelength resonator that contained two stacks and four internal heat exchangers. The overall thermoacoustic system was designed by Steven Garrett, Sound Advise Acoustical Consulting, under contract to General Electric Government Services (GEGS), the prime contractor for NASA’s Life Sciences Division in Houston, TX. After approval of the Preliminary Design Study [NASA Tech. Report No. LS-10114 (30 October 1991)], Sound Advise received a follow-on contract for the design of the heat exchangers. That design report was completed submitted to NASA and GEGS on 14 June 1992.

TALSR was fabricated at the Naval Postgraduate School in Monterey, CA. Half-way through the project, all funding was recalled by NASA and the TALSR project was stopped. The official reason for the termination was “lack of funds”. Six months after termination, the Federal Bureau of Investigation (FBI) revealed a two-year, multi-million dollar “sting” operation that uncovered an alleged fraud and kickback scheme among private contractors and government officials at the National Aeronautics and Space Administration's Houston center [See LA Times story at http://tech.mit.edu/V113/N62/nasa.62w.html] Among the eleven employees pleading guilty was NASA’s TALSR Project Manager, David Proctor.

Subsequently, General Electric Corporation and Martin Marietta agreed jointly to reimburse the United States Government $1 million for expenses incurred in conducting their portion of the undercover investigation [see www.ezez.com/hss/ols/press1.html], GEGS lost their contract for NASA Houston operations, and responsibility for refrigeration for Life Sciences Division projects was removed from Houston and transferred to the Glenn Research Center. Unfortunately, these revelations of fraudulent project management practices did not lead to the reinstatement of the TALSR Project funds.

This photograph shows the half-TALSR at the time NASA recalled the project’s funding. The thermoacoustic chiller was operating with only one driver since funding for the second driver was contingent on the operation that is demonstrated in this photograph. Frost can be seen extending from the bottom of the one cold heat exchanger through the entire U-shaped section of the resonator.

TALSR was “rescued” by the US Navy. During the 1st Gulf War, the USS Princeton (CG-59) hit a mine that disabled the ship’s refrigeration system. ADM J. P. Reason, the Commander of the Atlantic Surface Fleet, was searching for a way to cool critical electronic systems so that such an incident might not disable a fighting ship. His Science Advisor, Dr. Jeanie H. McCain, saw the half-TALSR during a visit to the Naval Postgraduate School and she informed ADM Reason who authorized the project to convert TALSR to a shipboard chiller for critical electronics. Funding was provided by the Naval Science Assistance Program through the Office of Naval Research, and TALSR was reborn as the Shipboard Electronics ThermoAcoustic Chiller (SETAC).

Overview of SETAC Design and Operation

  

Cross-sectional diagram of SETAC. Two custom-made electrodynamic drivers are coupled to the U-shaped resonator using two dual-convolution electroformed nickel bellows to provide a flexible seal for the pistons. The resonator was “bent” to fit into a standard 19” electronics rack. The resonator included two stacks (red); each stack had two fluid-backed finned heat exchangers with serpentine tubes (blue) that carried the water used as the heat transport fluids for both the hot and cold exchangers. The resonator was pressurized to 20 atmospheres (2.07 MPa, ~300 psia) with a mixture of 94.4% Helium and 5.6% Argon.

   The moving-coil electrodynamic loudspeakers used in SETAC were the first loudspeakers designed and built specifically for a thermoacoustic application. At the center is the piston (truncated cone) that is surrounded by the 15 “legs” of the upper suspension spring made from 17-7 PH stainless steel. The lower suspension, partially visible below the upper suspension, has 18 similar legs. The mechanical resonance frequency of the driver was 320 Hz. With a force factor, Bl = 18 N/A, a voice-coil electrical resistance, Rdc = 1.7 Ohm, and mechanical damping, Rm = 2.2 kg/sec, the driver had a maximum electroacoustic efficiency of 80%.

The full thermoacoustic system was tested extensively in the laboratory and at sea. While at sea, it produced a maximum cooling power of 419 W and at the lowest temperature which could be achieved using water as the cold-side heat exchange fluid (4 °C = 39 °F), it produced 294 W of useful cooling. Detailed power flow diagrams for both of these operating points are provided in the following figures.

  
This figure shows the flow of power at the highest power operating point where the driver’s electroacoustic efficiency is 51%. Since the heat exchangers were designed for the 205 W maximum cooling power required by NASA, the heat exchanger temperature deficits reduce the refrigerator’s coefficient-of-performance relative to Carnot (COPR) from 21% to only 8%.  

At the cold heat exchanger temperature specified by NASA, SETAC produced 294 W of useful cooling power (50% more than required by NASA) at an overall COPR = 17%.

A commercial prototype intended for use in a home refrigerator/freezer, based on the SETAC design, was produced for Coolsound Investments (Pty) Ltd. of Cramerview, South Africa. The design, provided by Sound Advice Acoustical Consulting under contract with Coolsound Investments, was fabricated by CSIR, Division of Manufacturing and Aeronautical Systems Technology in Pretoria, South Africa [see G. W. Swift, “Thermoacoustic Engines and Refrigerators,” Physics Today, pg. 26, Fig. 4 (July, 1995)].

  
The CSIR straight-prototype is shown during testing at Los Alamos National Laboratory using two of the SETAC drivers attached at either end.

  Two CSIR engineers and the U-shaped prototype attached to a conventional domestic refrigerator/freezer.

Personnel

Prof. Steven L. Garrett, Principal Investigator; David Perkins, Engineer; James A. Mayfield, Project Manager; D. Felipe Gaitan, Postdoctoral Researcher (Dual-driver control); Ashok Gopinath, Postdoctoral Researcher (Heat exchange); Glenn Harrell, Machinist; David Rigmaiden, Electronic Engineer, LCDR Richard A. Russell, USN, Master’s Thesis Student (Temperature Control); LT Dennis McKelvey, USN, Master’s Thesis Student (Fabrication, Programming and Shipboard Testing); LT Stephen Ballister, USN, Master’s Thesis Student (Fabrication and Shipboard Testing).

  
Principal Investigator’s face framed by the resonator section of SETAC.   LT Dennis McKelvey, Prof. Steven Garrett, and LT Stephen Ballister describe operation of SETAC to Thomas Gilmore – Code 822, an engineer employed by the Naval Surface Warfare Center, when he was visiting the USS Deyo while anchored off of Annapolis, MD.

Publications

S. L. Garrett, “High power thermoacoustic refrigerator,” U. S. Pat. No.5,647,216 (July 15, 1997); South African Letters Patent No. 96/6512 (31 July 1996); Indian Pat. App. No. 1686/Del/96, pending.

Technical Reports and Theses

Steven L. Garrett, “ThermoAcoustic Life Sciences Refrigerator: A Preliminary Design Study,” NASA Technical Report No. LS-10114 (30 October 1991). 43 pages, 15 figures, 2 tables, 22 references.

Steven L. Garrett, “ThermoAcoustic Life Sciences Refrigerator: Heat Exchanger Design and Performance Prediction.” Limited distribution. 65 pages, 11 figures, 17 tables, 22 references.

Richard A. Russel, “Exergy Analysis of the ThermoAcoustics Life Sciences Refrigerator,” Masters of Science in Aeronautical Engineering, March, 1994. DTIC Report No. AD B185-185.

Dennis J. McKelvey and Stephen C. Ballister, “Shipboard electronic thermoacoustic cooler,” Masters of Science in Engineering Acoustics and Master of Science in Applied Physics, June, 1995. DTIC Report No. AD A300-514.