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This AIR is arranged in the following two sections: 2E - Thermodynamic Characteristics of Working Fluids, which contains thermodynamic diagrams for a number of working fluids currently in use and supplied by various industrial firms. 2F - Properties of Heat Transfer Fluids, which contains data, primarily in graphical form, on fluids that are frequently used in fluid heat transfer loops. Other properties of the environment, gases, liquids, and solids, can be found, as follows, in AIR1168/9: 2A-Properties of the Natural Environment 2B-Properties of Gases 2C-Properties of Liquids 2D-Properties of Solids

Many different computer programs have been developed to determine performance capabilities of aircraft environmental control systems, and to calculate size and weight tradeoffs during preliminary design. Many of these computer programs are limited in scope to a particular arrangement of components for a specific application. General techniques, providing flexibility to handle varied types of ECS configurations and different requirements (i.e., during conceptual or preliminary design, development, testing, production, and operation) are designated “company proprietary” and are not available for industry-wide use. This document describes capabilities, limitations, and potentials of a particular computer program which provides a general ECS analysis capability, and is available for use in industry. This program, names AECS1, was developed under the sponsorship of the U.S. Air Force Flight Dynamics Laboratory (References 1 and 2).

This AIR is arranged in the following two sections: 2E - Thermodynamic Characteristics of Working Fluids, which contains thermodynamic diagrams for a number of working fluids currently in use and supplied by various industrial firms. 2F - Properties of Heat Transfer Fluids, which contains data, primarily in graphical form, on fluids that are frequently used in fluid heat transfer loops. Other properties of the environment, gases, liquids, and solids, can be found, as follows, in AIR1168/9: 2A-Properties of the Natural Environment 2B-Properties of Gases 2C-Properties of Liquids 2D-Properties of Solids

Many different computer programs have been developed to determine performance capabilities of aircraft environmental control systems, and to calculate size and weight tradeoffs during preliminary design. Many of these computer programs are limited in scope to a particular arrangement of components for a specific application. General techniques, providing flexibility to handle varied types of ECS configurations and different requirements (i.e., during conceptual or preliminary design, development, testing, production, and operation) are designated "company proprietary" and are not available for industry-wide use. This document describes capabilities, limitations, and potentials of a particular computer program which provides a general ECS analysis capability, and is available for use in industry. This program, names AECS1, was developed under the sponsorship of the U.S. Air Force Flight Dynamics Laboratory (References 1 and 2).

These specifications are written to cover automatic temperature controls under three classifications, namely: A AUTOMATIC TEMPERATURE CONTROLS - GENERAL - Dealing with features applicable to all types and uses. B AUTOMATIC TEMPERATURE CONTROLS - MILITARY AND COMMERCIAL - Covering features applicable to military aircraft and commercial aircraft. C DESIRABLE DESIGN FEATURES - General information for use of those concerned in meeting the requirements contained herein.

A life support system (LSS) is usually defined as a system that provides elements necessary for maintaining human life and health in the state required for performing a prescribed mission. The LSS, depending upon specific design requirements, will provide pressure, temperature, and composition of local atmosphere, food, and water. It may or may not collect, dispose, or reprocess wastes such as carbon dioxide, water vapor, urine, and feces. It can be seen from the preceding definition that LSS requirements may differ widely, depending on the mission specified, such as operation in Earth orbit or lunar mission. In all cases the time of operation is an important design factor. An LSS is sometimes briefly defined as a system providing atmospheric control and water, waste, and thermal management.

This SAE Aerospace Information Report (AIR) provides Nuclear, Biological and Chemical (NBC) protection considerations for environmental control system (ECS) design. It is intended to familiarize the ECS designer with the subject in order to know what information will be required to do an ECS design where NBC protection is a requirement. This is not intended to be a thorough discussion of NBC protection. Such a document would be large and would be classified. Topics of NBC protection that are more pertinent to the ECS designer are discussed in more detail. Those of peripheral interest, but of which the ECS designer should be aware are briefly discussed. Only radiological aspects of nuclear blast are discussed. The term CBR (Chemical, Biological, and Radiological) has been used to contrast with NBC to indicate that only the radiological aspects of a nuclear blast are being discussed.

This SAE Aerospace Information Report (AIR) provides Nuclear, Biological and Chemical (NBC) protection considerations for environmental control system (ECS) design. It is intended to familiarize the ECS designer with the subject in order to know what information will be required to do an ECS design where NBC protection is a requirement. This is not intended to be a thorough discussion of NBC protection. Such a document would be large and would be classified. Topics of NBC protection that are more pertinent to the ECS designer are discussed in more detail. Those of peripheral interest, but of which the ECS designer should be aware are briefly discussed. Only radiological aspects of nuclear blast are discussed. The term CBR (Chemical, Biological, and Radiological) has been used to contrast with NBC to indicate that only the radiological aspects of a nuclear blast are being discussed.

This publication is applicable to liquid cooling systems of the closed loop type and the expendable coolant type in which the primary function is transporting of heat from its source to a heat sink. Most liquid cooling system applications are oriented toward the cooling of electronics. Liquid cooling techniques, heat sinks, design features, selection of coolants, corrosion control, and servicing requirements for these systems are presented. Information on vapor compression refrigeration systems, which are a type of cooling system, is found in Reference 1.

Heat transfer is the transport of thermal energy from one point to another. Heat is transferred only under the influence of a temperature gradient or temperature difference. The direction of heat transfer is always from the point at the higher temperature to the point at the lower temperature, in accordance with the second law of thermodynamics. The fundamental modes of heat transfer are conduction, convection, and radiation. Conduction is the net transfer of energy within a fluid or solid occurring by the collisions of molecules, atoms, or electrons. Convection is the transfer of energy resulting from fluid motion. Convection involves the processes of conduction, fluid motion, and mass transfer. Radiation is the transfer of energy from one point to another in the absence of a transporting medium. In practical applications several modes of heat transfer occur simultaneously.

Heat transfer is the transport of thermal energy from one point to another. Heat is transferred only under the influence of a temperature gradient or temperature difference. The direction of heat transfer is always from the point at the higher temperature to the point at the lower temperature, in accordance with the second law of thermodynamics. The fundamental modes of heat transfer are conduction, convection, and radiation. Conduction is the net transfer of energy within a fluid or solid occurring by the collisions of molecules, atoms, or electrons. Convection is the transfer of energy resulting from fluid motion. Convection involves the processes of conduction, fluid motion, and mass transfer. Radiation is the transfer of energy from one point to another in the absence of a transporting medium. In practical applications several modes of heat transfer occur simultaneously.

The discipline of heat transfer concerns itself basically with the three modes of transferring thermal energy (convection, conduction, and radiation) and their inter-relations. In any phase of aerospace vehicle design, the importance of any of these basic modes will vary depending upon the natural and induced environment the mission imposes as well as the vehicle configuration.

These recommendations apply to the user's manual for any computer program pertaining to aircraft ECS. This includes computer programs for: a Cabin air conditioning and pressurization performance. b Avionics equipment cooling system performance. c Engine bleed air system performance. d Compartment and equipment thermal analysis. e Environmental protection system performance. These recommendations apply to user's manuals for generalized computer programs as well as those for a specific component or system.

This SAE Aerospace Recommended Practice (ARP) provides symbols to schematically represent aerospace vehicle environmental system components on functional flow schematic drawings and graphical computerized output. The symbols are for use on simplified diagrams that provide basic information about an environmental system. Symbols are provided to represent basic types of components used in environmental systems. Simple variations of basic symbol types are provided. Words on the schematic diagram, special symbol codes, or symbols that combine basic symbol types (Section 5) can be used to augment the basic symbols when appropriate. Special or combined symbols not contained in this document should be defined on the schematic diagram. An example of a complete schematic is given in Section 6. A bibliography of other documents on environmental system symbols is found in Appendix A.

This SAE Aerospace Recommended Practice (ARP) provides symbols to schematically represent aerospace vehicle environmental system components on functional flow schematic drawings and graphical computerized output. The symbols are for use on simplified diagrams that provide basic information about an environmental system. Symbols are provided to represent basic types of components used in environmental systems. Simple variations of basic symbol types are provided. Words on the schematic diagram, special symbol codes, or symbols that combine basic symbol types (Section 5) can be used to augment the basic symbols when appropriate. Special or combined symbols not contained in this document should be defined on the schematic diagram. An example of a complete schematic is given in Section 6. A bibliography of other documents on environmental system symbols is found in Appendix A.

This SAE Aerospace Recommended Practice (ARP) discusses design philosophy, system and equipment requirements, environmental conditions, and design considerations for rotorcraft environmental control systems (ECS). The rotorcraft ECS comprises that arrangement of equipment, controls, and indicators which supply and distribute dehumidified conditioned air for ventilation, cooling and heating of the occupied compartments, and cooling of the avionics. The principal features of the system are: a A controlled fresh air supply b A means for cooling (air or vapor cycle units and heat exchangers) c A means for removing excess moisture from the air supply d A means for heating e A temperature control system f A conditioned air distribution system The ARP is applicable to both civil and military rotorcraft where an ECS is specified; however, certain requirements peculiar to military applications—such as nuclear, biological, and chemical (NBC) protection—are not covered.

This report contains background information on life cycle cost elements and key ECS cost factors. Elements of life cycle costs are defined from initial design phases through operational use. Information on how ECS designs affect overall aircraft cost and information on primary factors affecting ECS costs are discussed. Key steps or efforts for comparing ECS designs on the basis of LCC are outlined. Brief descriptions of two computer programs for estimating LCC of total aircraft programs and their use to estimate ECS LCC, are included.

This report contains background information on life cycle cost elements and key ECS cost factors. Elements of life cycle costs are defined from initial design phases through operational use. Information on how ECS designs affect overall aircraft cost and information on primary factors affecting ECS costs are discussed. Key steps or efforts for comparing ECS designs on the basis of LCC are outlined. Brief descriptions of two computer programs for estimating LCC of total aircraft programs and their use to estimate ECS LCC, are included.

The Engineering Analysis SYstem (EASY) computer program is summarized in this report. It provides techniques for analysis of steady-state and dynamic (transient) environmental control system (ECS) performance, control system stability, and for synthesis of optimal ECS. General uses of a transient analysis computer program for ECS design and development, and general features of EASY relative to these uses, are presented. This report summarizes the nine analysis options of EASY, EASY program organization for analyzing ECS, data input to the program and resulting data output, and a discussion of EASY limitations. Appendices provide general definitions for dynamic analysis, and samples of input and output for EASY.