1、AEROSPACE RECOMMENDED PRACTICEARP731REV.CIssued 1963-05Revised 2003-01Superseding ARP731B(R) General Requirements for Application of Vapor Cycle Refrigeration Systems for AircraftTABLE OF CONTENTS1. SCOPE .32. REFERENCES .32.1 Applicable Documents .32.1.1 SAE Publications .32.1.2 U.S. Government Pub
2、lications.32.1.3 ARI Publications.2.1.4 ASME Publications 2.2 Related Publications 43. SYSTEM DESIGN RECOMMENDATIONS 43.1 Introduction 43.2 System Definition .43.2.1 Basic System .43.2.2 Additional Elements .53.3 Performance Characteristics53.3.1 Required Performance.53.3.2 Performance Analysis 63.3
3、.3 Off Design Performance.63.3.4 Evaporator Temperature 63.3.5 Optimum System Design Considerations 63.3.6 Evaporator Water Carryover 63.3.7 Extreme Tempertures and Pressures.63.3.8 Service Period73.4 Refrigerant Selection .73.4.1 Refrigerant Selection Consideration 73.4.2 Materials Compatibility.83
4、.4.3 Regulations 9Reaffirmed 2010-01SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any
5、 patent infringement arising therefrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2010 SAE International All rights reser
6、ved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canad
7、a) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedbackon this Technical Report, please visit http:/www.sae.org/technical/standards/ARP731CCopyright SAE International Provided by IHS under licens
8、e with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP731 Revision C- 2 -TABLE OF CONTENTS (Continued)3.4.4 Refrigerant Recovery .93.4.5 Lubricants.103.4.6 Refrigerant Properties103.5 Pressure Loads113.5.1 Maximum Design Pressure113.5.2 Proof Pressure .1
9、13.5.3 Burst Pressure .113.5.4 Externally Induced Loads.113.5.5 Fatigue Strength.123.5.6 Vacuum Loads .123.5.7 Refrigerant Leakage 123.6 Failure Protection.123.6.1 Overpressure Protection 123.6.2 Rotor Failure 123.6.3 Compressor Protection 123.6.4 Loss of Condenser Heat Sink 133.7 System Control 133
10、.7.1 Control Configuration .133.8 Packaging and Installation .144. COMPONENT DESIGN RECOMMENDATIONS154.1 Refrigerant Compressor.154.1.1 Configuration154.1.2 Positive Displacement Compressors .154.1.3 Centrifugal Compressors .174.1.4 Compressor Lubrication.174.2 Evaporator .174.3 Condenser .185. DESI
11、RABLE DESIGN FEATURES .196. NOTES20FIGURE 1 Typcal Vapor Cycle Refrigeration System Schematic 5TABLE 1 Properties of Commonly Used Refrigerants.11Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE A
12、RP731 Revision C- 3 -1. SCOPE:The purpose of this SAE Aerospace Recommended Practice (ARP) is to establish recommendations for the design, installation and testing of air vehicle vapor cycle refrigeration systems. These recommendations are representative of the refrigerant cycles.2. REFERENCES:2.1 A
13、pplicable Documents:The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between th
14、e text of this document and references cited herein the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained.2.1.1 SAE Publications: Available from SAE, 400 Commonwealth Drive, Warrrendale,
15、 PA 15096-0001.ARP85 Air Conditioning Systems for Subsonic AirplanesARP292 Air Conditioning Systems for HelicoptersARP987 Control of Excess Humidity in AvionicsAIR1168/3 SAE Aerospace Applied Thermodynamic Manual, Section 3: Aerothermodynamic Systems Engineering and Design2.1.2 U.S. Government Publi
16、cations: Available from DODSSP, Subscription Services Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094.A-A-58060 Fluorocarbons and Other Refrigerants, Department of Defense, Washington, DC, September 3, 1996VV-L-825C Lubricating Oil, Refrigerant Compressor, Uninhibited, Department
17、of Defense, Washington, DC, March 18, 1997MIL-STD-461E Requirements fort the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment, Department of Defense, Washington, DC, August 20, 1999MIL-STD-704E Aircraft Electric Power Characteristics, Department of Defense, Washing
18、ton, DC, November 15, 1991MIL-STD-810F Environmental Engineering Consideration and Laboratory Test, Department of Defense, Washington, DC, January 1, 2000MIL- HDBK -310 Global Climatic Data for Developing Military Products, Department of Defense, Washington, DC, June 23, 1997 (supersedes MIL-STD-210
19、)MIL-HDBK-454 General Guidelines For Electronic Equipment, Department of Defense, Washington, DC, April 28, 1995, Notice 1, May 28, 1997 (supersedes MIL-STD-454M)Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license fr
20、om IHS-,-,-SAE ARP731 Revision C- 4 -2.1.3 ARI Publications: Available from Air-Conditioning however, there are many factors to consider. Some of these factors are: equipment availability, system operation and quantity and boiling point of refrigerant. Many times it is possible to recover liquid fir
21、st and then finish the recovery process in vapor form. By employing liquid recovery first, recovery will take a shorter time. After the maximum quantity of liquid is recovered, vapor recovery will complete the process.3.4.5 Lubricants: Since HFC-based refrigerants are not miscible with the tradition
22、al mineral oils used as lubricants in CFC systems, new lubricants were developed to ensure the efficiency and long-term reliability of HFC systems. To meet this need, lubricant suppliers developed Polyolester-based oil (POE) and Poly Alkylene Glycol (PAG). POE and PAG lubricants are compatible with
23、most materials used in refrigeration systems and inhibit wear on the various parts inside the compressor. Because of its various desirable characteristics POE-based oil is the current lubricant of choice in HFC (R-134a in particular) vapor cycle applications in both retrofitted and new equipment.3.4
24、.6 Refrigerant Properties: Table 1 shows the critical properties of refrigerants available for consideration for use in various Vapor Cycle refrigeration systems.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license fr
25、om IHS-,-,-SAE ARP731 Revision C- 11 -TABLE 1 - Properties of Commonly Used Refrigerants3.5 Pressure Loads:3.5.1 Maximum Design Pressure: A maximum design pressure should be determined for each system component with due consideration given to the component internal and external temperatures and the
26、pressure versus temperature strength characteristics of the materials involved. The maximum design pressure in the refrigeration circuit may be induced either by extreme limits of normal system operation or by extreme high ambient temperatures with the system not operating (storage).3.5.2 Proof Pres
27、sure: All system components which are subjected to internal pressures, including the refrigerant piping, should be designed to be capable of withstanding a minimum proof pressure of 1.5 times (or factor acceptable to the regulatory agency) the maximum design pressure taking in to effect the operatin
28、g temperatures on material properties which can occur in the component without permanent deformation.3.5.3 Burst Pressure: All system components subjected to internal pressure should be designed to be capable of withstanding a minimum pressure of 3.0 times (or factor acceptable to the regulatory age
29、ncy) the maximum design pressure taking in to effect the operating temperatures on material properties. Permanent deformation is allowed.3.5.4 Externally Induced Loads: The system must be designed to withstand all externally induced loads incident to its installation in an air vehicle. These externa
30、l loads include up and down, fore and aft and sideways acceleration loads, vibration, shock and gyroscopic loads induced in components with rotating parts caused by air vehicle roll, yaw, or pitch. The design shall consider superimposition of internal pressure loads with external loads. In addition,
31、 consideration must be given to loads imposed by air vehicle structural and thermal deflections both during flight to withstand crash landing.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP73
32、1 Revision C- 12 -3.5.5 Fatigue Strength: The fatigue strength of the system components should be sufficient to provide operation for the design life of the air vehicle.3.5.6 Vacuum Loads: All system components designed to contain refrigerant should be capable of withstanding repeated collapsing pre
33、ssure differentials of 102 kPa (30 in Hg) without deformation or failure.3.5.7 Refrigerant Leakage: The system leakage rate should be essentially zero. For systems that incorporate components with dynamic external seals that cannot meet zero leakage, a minimum of 1200 hours (or specified in procurem
34、ent specification) or four calendar months of system operation without requiring replenishing is recommended. These systems should incorporate special provisions to allow rapid and accurate replenishing. A criteria of establishing a leakage of less than 14 g/year (0.5 oz/year) can also be considered
35、.3.6 Failure Protection:3.6.1 Overpressure Protection: The system shall incorporate a positive overpressure device designed to relieve pressure within an acceptable margin below proof pressure. A rupture disc (overpressure rupturing device) or a relief valve (automatic resetting device) shall be con
36、sidered. The overpressure device shall be easily accessible when the equipment is installed in the air vehicle.3.6.2 Rotor Failure: Failure of any high-energy rotor incorporated in the system shall not result in fire or other hazardous conditions. The rotor case or auxiliary protective shield shall
37、be sufficiently strong to contain a three segment rotor hub burst at the highest rotor speed expected either in normal operation or as a result of any single control element failure. Other elements of the refrigeration system may be arranged to provide this protection in military applications contai
38、nment within the case or housing will be required. In addition, if an electric drive is used, a motor protector shall be incorporated to prevent rotor case penetration in the event of an electrical fault.3.6.3 Compressor Protection:3.6.3.1 Pneumatic Drive: The refrigerant compressor and drive shall
39、incorporate a separate overspeed shut-off device, in addition to any modulating control that may be required for normal system operation, where damage or permanent deformation can occur due to overspeed The detecting element of an over speed shut-off device shall be located on the driver unit. Requi
40、rements for rotating equipment containment must be considered.3.6.3.2 Electric Drive: The electric driven refrigerant compressor shall incorporate motor overload, phase differential and phase open motor protection. Phase order protection should be added, to prevent running in wrong sense.Copyright S
41、AE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP731 Revision C- 13 -3.6.4 Loss of Condenser Heat Sink: In the event of a condenser failure, the system shall be designed to prevent permanent damage or acc
42、umulation of un-condensable refrigerant allowing the system to operate without a condenser heat sink. The design of the emergency shutdown system shall be included in the aircraft hazard analysis. Such operation results in excessively high refrigerant temperatures and pressures that may represent a
43、hazardous condition to the air vehicle and its occupants. A refrigerant pressure switch should be considered to activate system shut down under these conditions. Certain commonly used halogenated hydrocarbon refrigerants experience a violent exothermic reaction in the presence of aluminum and other
44、metals at high super critical temperatures and may cause fire or explosion. The Underwriters Laboratory states “that the products of decomposition of fluorinated refrigerants have a very acrid, irritating odor, and their presence is intolerable in concentrations below the toxic level. Under practica
45、l conditions, the amounts of decomposition products formed are so small that they do not create a hazard in the use of these refrigerants.”3.7 System Control:3.7.1 Control Configuration: Selection of the system control elements and arrangements is dependent to a large extent on the system configurat
46、ion and the cooling system in which the refrigeration system is incorporated. Generally, the major control elements that may be required are:a. Evaporator refrigerant temperature, pressure or airflowb. Condenser subcooling, or evaporator superheatc. Compressor speed (pneumatically /electrically driv
47、en centrifugal machines)d. Compressor inlet pressure (electrically driven centrifugal machines)e. Condenser heat sink control and discharge pressuref. Compressor surge control (centrifugal machines)g. Compressor lubrication control (positive displacement machines)h. Economizeri. Temperature Control
48、for the heat transfer media3.7.1.1 Cockpit: Sufficient sensor input from the cooling system interface should be provided with corresponding cockpit display to indicate normal operation of the refrigeration system to the aircrew and provide for fault detection and isolation for the various components
49、. A duplicate of this display on the cooling machine itsels can also be provided. Adequate instrumentation shall be installed to allow the required system operation.3.7.1.2 Service Connections: For maintenance sufficient ports should be incorporated in the system to allow rapid troubleshooting during ground maintenance. Variables to be measured may include compressor suction and dischar
