Single Screw Ammonia Heat Pumps Harness Your Heat... Don t Reject It
Harness Your Heat Don't Reject It Industrial processes consume considerable energy from two primary sources in the production of their products. Mechanical refrigeration applied in the processing and preservation of products consumes electrical energy, while the hot water supplied for clean-up, cooking and process heating employs mostly fossil fuels. The considerable energy absorbed by ammonia in industrial refrigeration is usually discarded to the atmosphere as wasted heat. The entering flow of gas or oil used to produce hot water bypasses the significant energy potential of the exhausted heat of rejection from refrigeration. With a growing interest in conserving energy and renewing their refrigeration system's wasted heat of rejection, industrial processors are tapping into recent screw compressor developments in making the most of their energy resources. End-users are realising the powerful potential of applying industrial heat pumps to their processes and converting their waste heat into useable heat, afforded through the use of the high pressure capabilities of single screw compressor technology. Vilter has extended the Single Screw compressor line with the addition of high pressure heat pump screw compressor models. These screw compressor units, with frames constructed of cast steel, are capable of operating with ammonia at extremely high condensing temperatures. Integrated into existing ammonia refrigeration systems, the heat pump compressors provide a cost effective solution to harnessing and converting your heat of rejection to high grade hot water, up to 90 C. The Vilter high pressure heat pump compressors retain the single screw's inherent design advantages of balanced forces for long life and high reliability, and parallel slides for peak performance at full or part load performance and reliability superior to any twin screw compressor. 2
Heat pumps extract heat from a variety of sources and convert the heat to higher temperatures for use in many industrial applications. The advanced compression capabilities of Vilter's single screw technology have contributed to the development of heat pumps for industrial applications, providing higher capacities and a greater range of temperatures than prior generations of heat pump compressors. Heat Sources Heat Pump (refrigeration cycle) Applications Air Ground Water Process Cooling Process Heating Oil Cooling evaporation expansion condensation District heating Food production Humidity control reheat Pasteurisation Air curtains Sanitation Process drying Desalination Scalding Underfloor heating Commercial HVAC Bottle warming Pharmaceutical Petrochemical Condensing compression Refineries Boiler preheat Single Screw Balanced Loading: Superior Technology for High Pressure Operation The advantage of the Single Screw compressor over other technologies is the fact that there are no net radial or axial forces exerted on the main screw or drive shaft components due to the work of compression. Since compression occurs symmetrically and simultaneously on opposite sides of the screw, the compression forces are canceled out. The only vertical loads exerted on the main screw bearings are due to gravity. Since the discharge end of the screw is vented to suction, the suction gas pressure is exerted on both ends of the screw resulting in balanced axial loads. Radially and Axially Balanced Main Screw Pressurized Seal Chamber for Increased Reliability Electronic Optical Slide Actuator Star Gaterotor Balanced Radial Loads Balanced Axial Loads Variable Volume Slide 1.2 to 7.0 Ratio Variable Capacity Slide 10% to 100% 3
Conventional Heat Recovery vs. Ammonia Heat Pump System Single screw compressor technology allows for sustained operation at higher saturated condensing temperatures than conventional systems, providing for the full use of the system's heat of rejection for high temperature heating. R717 Self-Contained Ammonia Refrigeration Heat Pump 200 100 Available Waste Heat Oil Cooling 40 20 Pressure (bara) 10 4.0 2.0 1.0.40.20 Conventional Conventional Heat Recovery from Ammonia Refrigeration Oil Cooling and Condensing Available Heat.10-200 0 200 400 0 800 1000 1200 1400 10 1800 Enthalpy (Kj/Kg) Conventional heat recovery in industrial refrigeration systems utilise only 10 to 15% of the total heat of rejection including superheat and oil cooling. The majority of the heat is rejected through the condenser. However the temperature of this heat source is typically too low for beneficial use Ammonia Pressure-Temperature Relationship 80 70 Design Limit for Vilter Cast Steel Compressors (76 bar, 110 C) Cast steel frame Pressure (bara) 50 40 30 Compressor Duty Required for Industrial Heat Pumps (28 bar, 63 C to 52 bar, 90 C) Design Limit for Most Compressors (26 bar, C) Ductile iron frame 20 10 Normal Operating range of Refrigeration Compressors (0.4 bar, -50 C to 15 bar, 38 C) Cast iron frame - -40-20 0 20 40 80 100 120 Temperature ( C) 4
Practical Application The use of heat pumps to extract heat from air and water is increasingly popular, largely because the heat they deliver far exceeds the energy they consume. Vilter engineers, collaborating with Star Refrigeration** and Norsk-Kulde, made use of Vilter single screw compressors to produce the pressures and temperatures required for the system. The city of Drammen, Norway is embarking on a novel energy saving plan using an ammonia-based stand-alone heat pump system. When the project comes on line, all of Drammen s hot water heating needs with be supplied with energy extracted from the frigid North Sea, greatly reducing the use and emissions of fossil fuels. The city of Drammen (population,000) needed hot water at 90 C for their new district heating system. Using ammonia refrigerant (R-717) the project is highly efficient, greatly reduces the use of fossil fuels, and has no negative impact on the ozone layer or global warming. 5
Single Stage Scavenging Heat Pump System A scavenging heat pump system is designed to pull heat out of an existing refrigeration system by diverting ammonia discharge gas away from refrigeration system condensers to the suction inlet of the heat pump system. Vilter single screw compressors are designed to handle the high suction pressures required of this duty, and deliver the very high discharge temperature vapors for water heating in order to make use of the refrigeration system s waste heat. In heating water to moderate temperatures, up to 71 C, single stage single screw heat pump systems provide optimal performance (COP s) due to the duty s relatively low differential pressures, up to 24,2 bar. Ammonia heat pump scavenging system R717 Ammonia 200 100 40 Subcooling Condensing Oil Cooling & 20 Pressure (bara) 10 4.0 2.0 1.0.40 Host Oil Cooling &.20.10 Single Stage Ammonia Scavenging Heat Pump Package -200 0 200 400 0 800 1000 1200 1400 10 1800 Enthalpy (Kj/Kg) Existing Refrigeration System Single Stage Heat Pump Scavenging System 6
Two-Stage Scavenging Heat Pump System Two-stage scavenging heat pump systems are utilized where the desired water temperatures are higher than those provided by single stage systems. Higher differential water temperatures correlate to higher differential pressures in heat pump compressors. By splitting the heat pump design from a single stage to a twostage system, superior COP s are realized in achieving very high water temperatures, up to 90 C. Vilter single screw compressors employed to satisfy the high pressures and temperatures of twostage ammonia heat pumps operate reliably and efficiently at such intensive duties due to their naturally balanced axial and radial design. Ammonia heat pump scavenging system R717 Ammonia 200 100 40 20 Subcooling Condensing 2nd Stage Oil Cooling & 1st Stage Oil Cooling & Pressure (bara) 10 4.0 2.0 1.0 Host Oil Cooling &.40.20.10 Two-Stage Ammonia Scavenging Heat Pump Package -200 0 200 400 0 800 1000 1200 1400 10 1800 Enthalpy (Kj/Kg) Existing Refrigeration System Two-Stage Heat Pump Scavenging System 7
Technical Overview Single stage ammonia heat pumps Model VSS-291 VSS-341 VSS-451 VSS-1 Suction Pressure SST Discharge Pressure 32.5 32.2 31.9 31.9 SDT 71 70.5 70 70 Nominal Water Flow 16.4 19.1 28.6 33.9 Heat Recoverd 1429 1658 2503 2946 Total Absorbed Power Barg C Barg C m 3 /hr kw kw 228 264 386 447 COP 6.28 6.28 6.49 6.59 * Based upon compressors operating at 3550 RPM (Hz) Two-stage ammonia heat pumps Model Suction Pressure Barg SST C Discharge Pressure Barg SDT C Power kw Nominal Water Flow m 3 /hr Heat Recoverd kw Total Absorbed Power kw COP Low High VSS-451 VSS-291 24.9 25.2 49.0.5 89.5 286 317 29.5 2571 3 4.27 Low High VSS-1 VSS-341 24.9 25.2 49.0.5 89.5 332 371 35.9 3130 703 4.45 Low High VSS-901 VSS-451 24.9 25.2 49.0.5 89.5 571 573 53.2 4636 1144 4.06 Low High VSS-1051 VSS-1 24.8 25.2 49.0.5 89.5 618 647 61,6 5375 1264 4.25 * Based upon compressors operating at 3550 RPM (Hz) ** Emerson Climate Technologies has a working agreement with Star Refrigeration on providing the European Market with industrial heat pump packages. OTH002-EN-1009 Emerson Climate Technologies - European Headquarters - Pascalstrasse 65-52076 Aachen, Germany Phone: +49 (0) 2408 929 0 - Fax: +49 (0) 2408 929 570 - Internet: www.emersonclimate.eu or www.vilter.com The Emerson Climate Technologies logo is a trademark and service mark of Emerson Electric Co. Emerson Climate Technologies Inc. is a subsidiary of Emerson Electric Co. Copeland is a registered trademark and Copeland Scroll is a trademark of Emerson Climate Technologies Inc.. All other trademarks are property of their respective owners. Information contained in this brochure is subject to change without notification. 2010 Emerson Climate Technologies, Inc.