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PLRC Overview Rev2


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PLRC is a isothermal cooling technology that replaces conventional liquid cooling system. It delivering high performance in a smaller, ligher package.

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PLRC Overview Rev2

  1. 1. 978-463-9495(O) HTE Associates, Inc. 42 Middle Rd. 978-270-1407(M) Newbury, MA 01951 OVERVIEW PUMPED LIQUID REFRIGERANT COOLING (PLRC) PLRC Technology
  2. 2. 978-463-9495(O) HTE Associates, Inc. 42 Middle Rd. 978-270-1407(M) Newbury, MA 01951 HTE is searching for defense and industrial opportunities to demonstrate the advantages of Pumped Liquid Refrigerant Cooling (PLRC). PLRC combines the simplicity and reliability of a typical pumped liquid, thermal management and control design with the advantages of a vapor compression cycle. The result is a hybrid thermal management and control technology that transcends both technologies with measured COP values that range between 17 and 70 for air cooled and water cooled condensers, respectively. Figure 1 shows a typical PLRC cooling loop; sub-cooled (liquid) refrigerant is pumped through a cold plate. Here the energy from the load converts the liquid to an isothermal (constant temperature) vapor (figure 2). Finally, the vapor is converted back to sub-cooled liquid via an air condenser. Over the last 10 years, PLRC thermal management and control systems have demonstrated superior performance over currently accepted water, ethylene glycol/water (EGW), and PAO thermal management practices. Figure 3 compares the normalized cooling capacity and flows of the four coolants. Using PAO as the reference, the plot shows that the thermal performance of the PLRC is 30 times greater than the PAO at ~3.4% of the flow. EGW and water are somewhat better than PAO but fall short of the PLRC performance. Figure 4 compares the sensible temperature rise of Water, EGW, and PAO to the latent heat quality (isothermal characteristics) of the PLRC technology. The plot shows that for every 1.0 deg C rise in their temperatures, the refrigerant quality increases by 0.85%. Thus, the value propositions for PLRC technology include the following attributes: • Flow boiling heat transfer coefficients coupled with the cold plates accelerated flow rates maximizes the heat transfer coefficients while minimizing flow requirements, • Latent heat of vaporization produces isothermal heat transfer characteristics • Quality vapor results in a wide operating margin. • Low flow rates result in minimizing weight, packaging envelop, and power consumption. • Fast transient response with temperature control of less than ±1.0 deg C. • PLRC is a non-refrigerant specific technology, tailored to customer’s application.
  3. 3. 978-463-9495(O) HTE Associates, Inc. 42 Middle Rd. 978-270-1407(M) Newbury, MA 01951 Notes: 1. Tf = 0˚C 2. Mass Flow Rate = Constant 3. Hfg=91Btu/Lb (R-134a) 4. ΔT = 0 deg C (R-134a) PLRC Opportunities Phased-array radar designers attempt to eliminate element-to-element and overall temperature differences. To maintain reliable signals, temperature compensating circuits are often added. However, when PLRC thermal management is considered, temperature issues become insignificant, thus, giving the designers greater liberty for circuit design. Other attributes include constant temperature cooling during transient power demands and lower pump power. PLRC’s low power demands, small packaging envelop, and light weight make it especially suited for avionics application. Lasers, electro-optics, photonics, CT-scanners, and MRI are examples of hardware that require a stable precision alignment and control systems. High heat densities, coupled with harsh environments, induce thermal stresses that compromise stability and alignment. PLRC isothermal cooling characteristics, coupled with the advantages of flow boiling heat transfer, provide a simple, low cost solution. PLRC test results on a 212w (~1000w/cm 2) medical laser heat exchanger using 0.03 gal/min of 35⁰C sub-cooled refrigerant resulted in an overall conductance value of 20.8w/cm2-⁰C or about twice the effectiveness of other liquid cooling media. PLRC green opportunities exist in the computer and fermentation industries. Data centers and server farms in the United States and the World consume about 1$2.7B and 1 $7.2B in energy costs annually. Approximately 50% of the cost can be attributed to thermal management and control. A PLRC Enterprise proof-of-concept model showed that over 60% of the cooling cost can be eliminated, thus, saving $0.8B and $4.3B for the USA and the World, respectively. Room environmental temperatures and humidity are often tightly controlled to augment fermentation. However, utilizing PLRC thermal management and control technology at the vat level will reduce the need for additional energy for room air conditioning. 1. Ref: Author Jonathan G. Koomey, Ph. D, title, “Estimating Total Power Consumption by Servers in the U.S. And The World”, Lawrence Berkeley Nation Lab., February 25,2007- Dollar values are for 2005