1、_ SAE 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 patent infringement arising there
2、from, 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 2011 SAE International All rights reserved. No part of this publication m
3、ay 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 Canada) Tel: +1 724-776-4970 (outside U
4、SA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedbackon this Technical Report, please visit http:/www.sae.org/technical/standards/J2772_201102SURFACEVEHICLESTANDARDJ2772 FEB2011 Issued 2011-02 Measurement of Passenger Compart
5、ment Refrigerant Concentrations Under System Refrigerant Leakage Conditions RATIONALE This standard was developed to provide a standard method for measuring refrigerant concentration in a motor vehicle. This is needed to provide consistent inputs to any risk assessment that is done on new refrigeran
6、ts being developed for mobile air conditioning. 1. SCOPE This Standard is restricted to refrigeration circuits that provide air-conditioning for the passenger compartments of passenger and commercial vehicles. This Standard includes analytical and physical test procedures to evaluate concentration i
7、nside the passenger compartment. In the early phases of vehicle evaluation, usage of the analytical approach may be sufficient without performing physical tests. The physical test procedure involves releasing refrigerant from an external source to a location adjacent to the evaporator core (inside t
8、he HVAC-Module). An apparatus is used to provide a repeatable, calibrated leak rate. If the system has multiple evaporators, leakage could be simulated at any of the evaporator locations. This standard gives detail information on the techniques for measuring R-744 CO2 and R-1234yf HFO-1234yf, but th
9、e general techniques described here can be used for other refrigerants as well. 1.1 Purpose The purpose of this SAE Standard is to provide a uniform test procedure to evaluate the refrigerant concentration level inside of a vehicle passenger compartment resulting from leakage of refrigerant from a M
10、obile Air Conditioning system (MAC). This Standard does not establish concentration limits. Refrigerant can leak from the evaporator, hoses, lines, and connectors that are directly exposed to the passenger compartment or the cabin air distribution system. Refrigerant concentration is influenced by l
11、eak size, refrigerant charge, HVAC operation mode, body sealing, and vehicle operation mode. SAE J2772 Issued FEB2011 Page 2 of 112. REFERENCES 2.1 Applicable Documents The following publications form a part of this specification to the extent specified herein. Unless otherwise indicated, the latest
12、 issue of SAE publications shall apply. 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.2.1.1.1 System Design Guidelines SAE J639 Safety Standards for Moto
13、r Vehicle Refrigerant Vapor Compression Systems SAE J2773 R-1234yf and R744 Refrigerant Standard for Safety and Risk Analysis for use in Mobile Air Conditioning Systems SAE J2842 R-1234yf and R-744 Design Criteria and Certification for OEM Mobile Air Conditioning Evaporator and Service Replacements
14、2.1.2 Other Publications Refrigerant Material Safety Data Sheet Safe Use and Handling Guidelines available from refrigerant suppliers 3. VEHICLE SYSTEM DESCRIPTION 3.1 Vehicle Interior Volume The vehicle interior volume is the space available to the occupants. It can change depending on vehicle inte
15、rior variants. It includes volumes such as HVAC housing and duct internal volumes. For the determination of an interior volume, the net free space of the interior of the vehicle as built is to be considered. Net free space is defined as the volume of the interior of the cabin minus all components in
16、side the vehicle, (seats, trim, instrument panel components and structure, steering wheel, etc.). CAE models may be used to determine the vehicle interior volume. Table 1 shows typical vehicle volumes. 3.2 Passenger Volume Considerations To determine the refrigerant concentration of the vehicle inte
17、rior, the volume displaced by passengers shall be considered. Therefore, the effective vehicle interior volume is reduced by 75 L/passenger. For the measurement of the interior concentration, mannequins shall be placed on the seats according to the rated seating capacity of the vehicle. Physical man
18、nequins and the displacement volumes used in testing shall be constructed of impermeable materials (metal, hard plastic) or shall be taped with aluminum foil backed tape or encased in an impermeable plastic material to avoid the possible diffusion of the refrigerant into the mannequins. SAE J2772 Is
19、sued FEB2011 Page 3 of 11TABLE 1 - TYPICAL VEHICLE INTERIOR VOLUMES Vehicle Type InteriorSize m3Number of Seats Adjusted InteriorVolume m3Compact Sports Vehicle 1.6 2 1.4 Sub-Compact Vehicle 1.7 4 1.4 Compact Vehicle 2.4 4 2.1 Full Size Car 2.8 5 2.4 Large size vehicle 3.1 6 2.6 SUV 4.0 3.5 Mini Van
20、 6.0 9 5.2 3.3 Air Exchange Rate Considerations Vehicle cabins are not hermetically sealed in relation to their environment. An additional air exchange with the environment around the vehicle takes place via openings in the vehicle body. These openings include: Pressure Release Valves (PRV), body st
21、ructure gaps, leaking sealing elements, etc. This air exchange is affected by the driving speed and other operating and ambient conditions. The air exchange rate AER expresses the frequency in which the interior air of a vehicle cabin is replaced. Air exchange is also referred to as “body leakage.“
22、Table 2 shows typical air exchange rates. TABLE 2 - TYPICAL AIR EXCHANGE RATES Vehicle operation condition HVAC Status AER h-1Stand still Off 0.5-1.0 IDLE Low Blower, 100% RECIRC 2.0-3.0 Driving Low Blower, RECIRC 4.0-6.0 REF: “Air change rates of motor vehicles and in-vehicle pollutant concentratio
23、ns from second hand smoke”, WAYNE OTT, NEIL KLEPEIS AND PAUL SWITZER, Journal of Exposure Science and Environmental Epidemiology (2007), 114 Table 2 is for reference only. The vehicle OEM can consider the AER to use for physical test and analysis evaluations. In the analysis situation, the locations
24、 for the air exchange shall be specified in the analytical model. 4. REFRIGERANT RELEASED DURING A LEAK 4.1 Nominal Charge The vehicle manufacturer specifies the nominal amount of charge in the refrigerant circuit. The determination of that charge is in context of the development process. It can be
25、determined under high climatic load. The durable nameplate or tag mounted in the engine compartment, as described in SAE J639, contains information about the lubricant type and the amount of refrigerant charge. This may be the starting point for determining the refrigerant charge to use during the t
26、est. This amount can be reduced due to oil absorption, as described below. 4.2 Oil Absorption When the system is charged, part of the refrigerant dissolves into the compressor lubricating oil. This will reduce the amount of refrigerant released during a leak. SAE J2772 Issued FEB2011 Page 4 of 114.3
27、 Factors to Consider Regarding Leaks When a refrigerant leak occurs, only the available refrigerant will be released out of the refrigerant circuit. The refrigerantdissolved in the lubricant remains in the circuit and will be released over a longer period. The OEM shall consider how much refrigerant
28、 may be dissolved in the oil and not released. In a rapid leak e.g., mechanical breakage, collision scenarios more refrigerant will be retained in the system compared to a corrosion leak of refrigerant into the passenger compartment. The amount of oil retained in the system will also be variable and
29、 this should be considered when evaluating retained refrigerant. The refrigerant amount used in test shall be adjusted based on this analysis. Additional factors to be considered may include other component failures releasing refrigerant outside the passenger compartment, collision activated devices
30、 that limit the amount of refrigerant that can be released into the cabin, and/or other HVAC module design features. 4.4 Calculation of Charge Amount Released into Passenger Compartment The following is an example calculation: TABLE 3 - EXAMPLE OF CALCULATION FOR RELEASED REFRIGERANT Charge Consider
31、ation Charge amount, g SAE J639 charge label or an estimate if not yet determined 600 Amount of refrigerant estimated to be retained in the system in a rapid discharge of refrigerant (zero (0) grams for corrosion leaks) -40 Amount not released due to other design feature of the AC system (i.e., syst
32、em internal volume or component layout and design) -50 Amount released by breakage in another component failure -150 Amount discharged into passenger compartment for test: 360 4.5 Passenger Generated CO2Due To Respiration In the case of R-744, a saturated background CO2concentration shall be taken i
33、nto account, due to passenger respiration. The respiration rate of 20 L of CO2per hour per passenger should be considered for determining the background concentration. The saturation value shall be recorded in the test summary. 5. TEST CONDITIONS The refrigerant concentration will vary based on the
34、wind speed over the body, temperature, atmospheric pressure, leak rate and number of occupants in the vehicle. The selected HVAC settings and controls (such as items shown in Table 4 below) also influence the concentration of refrigerant in the vehicle. The OEM shall consider these vehicle design ch
35、aracteristics in determining the expected case for maximum concentration in the vehicle. Table 4 shows an example test plan for evaluating a new vehicle design. Other test parameters should be considered, such as: 1. Unique settings that may be required by individual OEM 2. Unique settings that may
36、be required due to hardware/software limitations or features SAE J2772 Issued FEB2011 Page 5 of 11TABLE 4 - EXAMPLE TEST PLAN CONDITIONS Exterior Wind Velocity HVAC mode Blower RECIRC/Outside Air Temp control 2-3 m/s Foot OFF OSA Full Hot 0 m/s Face/Panel LOW RECIRC Full Cold 2-3 m/s Face/Panel LOW
37、RECIRC Full Cold 2-3 m/s Face/Panel HIGH RECIRC Full Cold 2-3 m/s DEF HIGH OSA Full Hot 0 m/s BI-LEVEL OFF RECIRC 50% 2-3 m/s BI-LEVEL OFF RECIRC 50% NOTE: When in face mode, the outlets should be directed to the face of the mannequins in the vehicle. 5.1 Refrigerant Leakage Rates The rate of refrig
38、erant leakage is a significant parameter influencing the local refrigerant concentration inside a passenger vehicle. The following leakage rates and leak diameters have been determined from field returned evaporator failures. Two alternate refrigerants currently being considered are shown in Table 5
39、. For corrosion leak testing, refrigerant shall flow through an orifice of the diameter shown in Table 5. The pressure across the orifice shall be equal to that of a thermally soaked system at a temperature of 40 C For severed line testing, the instantaneous rate of leakage shall be maintained to wi
40、thin 20% of the value shown in Table 5.Deviation from the prescribed table shall be identified with causal reason in the test report. TABLE 5 - REFRIGERANT FLOW RATES FOR DIFFERENT EVAPORATOR FAILURE MODES. Leak Type Leak diameter mm Vapor flow rate g/sec R-744 R-1234yfCorrosion 0.1 0.10 (average) 0
41、.03 Severed Line Collision 6.35 50 12 5.2 Refrigerant Quality Refrigerant released into the passenger compartment shall be in the vapor phase. 5.3 Operating and Ambient Test Conditions Refrigerant concentration shall be determined for the different HVAC and vehicle operating conditions in the test p
42、lan. The vehicle shall be evaluated with mannequins that represent the prescribed test scenario occupant level and operated at room temperature (22 C 10K). The vehicle OEM is responsible to determine the vehicle conditions to evaluate for refrigerant concentration in the passenger compartment and ma
43、y run at additional ambients but shall evaluate at the ambient above. 6. IN-CABIN REFRIGERANT MEASUREMENT EQUIPMENT AND PREPARATION There are several methods of capturing the concentration measurement in the vehicle passenger compartment that are suitable. For all methods, the time interval between
44、readings can be chosen based on the leak rate and the measurement method used. Two physical methods are described below. Also, details to construct an analytical model are shown. Several apparatus for releasing refrigerant are described. Investigators are not limited to the examples given. SAE J2772
45、 Issued FEB2011 Page 6 of 116.1 Safety Considerations Cylinders used for holding refrigerant shall meet high pressure cylinder requirements and be checked periodically to assure they are safe to use. Refrigerant charge should not fill the cylinder past 80% liquid volume at room temperature. Cylinder
46、s should be equipped with pressure relief devices. Refrigerant concentration testing shall be conducted in a facility with sufficient air exchange rate to assure that the concentration of the refrigerant shall not exceed a toxic or flammable level. If local regulation prohibits the release of refrig
47、erants into the atmosphere, substitute gases with similar properties may be used for testing. At present, suitable substitute gases have not been identified. 6.2 Real-Time Electronic Sensor For detecting the refrigerant concentration inside a vehicle compartment, commercially available sensors with
48、sufficient long-term stability can be used. The output of the sensors shall report the refrigerant concentration in volume percent. The measuring range of the sensor for the refrigerant shall be from 0% by volume up to 20% by volume. The sensor shall maintain accuracy between 10 C and 50 C. The sens
49、or shall have an accuracy of at least 0.2% by volume at 5% volume level. All sensors shall be calibrated against a suitable standard before installing in the test vehicle. Suitable calibration standards are: gas chromatography well mixed calibrated volume with a precise refrigerant mass, and calibrated laminar flow meter controllers. Other calibration standards are allowed if it is traceable to one or m
