1、 WORLDWIDE ENGINEERING STANDARDS Test Procedure GMW15775 Air Conditioning Evaporator Core Condensate Freeze Test Procedure Copyright 2012 General Motors Company All Rights Reserved September 2012 Originating Department: GME Specification Center Page 1 of 12 1 Scope Note: Nothing in this standard sup
2、ercedes applicable laws and regulations. Note: In the event of conflict between the English and domestic language, the English language shall take precedence. 1.1 Purpose. Evaporator Core freeze results in reduced compressor oil circulation and can result in compressor damage. The purpose of this te
3、st is to determine: 1.1.1 In the case of the variable capacity compressor, whether the Pneumatic Control Valve adequately protects the evaporator from condensate freeze (with worst case control variation comprehend). 1.1.2 In the case of fixed capacity compressor systems, whether the control of the
4、compressor cycling (clutch control) adequately protects the evaporator from condensate freeze with production variation in the control system comprehended. 1.1.3 In the case of an Electronically Variable Displacement Control (EVDC) or electrically driven compressor systems, whether the capacity cont
5、rol (either displacement command or compressor speed command) adequately protects the evaporator from condensate freeze with system variation comprehended. Note: The refrigerant charge variation included in this test is not sufficient to evaluate condensate freeze below Operational refrigerant charg
6、e. (i.e., GMW15775 is not a low refrigerant charge evaluation test). 1.2 Foreword. This Test Procedure is intended to be used to collect data during Heating Ventilation and Air Conditioning (HVAC) system validation. 1.2.1 GMW15775 is a vehicle-level or bench test to perform final system verification
7、 around evaporator condensate freeze with production intent sensor designs/placements, controller, software and calibrations under a robust set of vehicle operating conditions while comprehending control system variation 1.2.2 GMW16571 shall be used as a test technique to determine the optimal locat
8、ion of the refrigerant control sensors (Evaporator Air or Fin Temperatures, refrigerant temperature probes or refrigerant pressure transducers). 1.2.3 GMW16571 shall be used during system development testing to define an appropriate factor of safety necessary for a robust system calibration. Frost f
9、ormation data along with a system variation analysis is used to predict expected production variation. 1.2.4. GMW16571 shall be used as a test technique to develop initial calibrations with a proposed sensor placement and production intent control design that will provide robust protection from evap
10、orator condensate freeze under most applicable conditions expected to be encountered for the vehicles intended usage. 1.3 Applicability. This test procedure is intended for use on either a HVAC system test bench or full vehicle tests in Climate tunnels. The following conditions must be met for valid
11、 results of the testing. 1.3.1 Test must be conducted with representative Air Handling conditions at the Evaporator Air Inlet and Exit (typically this means testing with a complete and representative HVAC Module). 1.3.2 Test must be conducted with representative Air Flow conditions at the Condenser
12、Air Inlet and Exit. Typically this means testing with a complete and representative Condenser Radiator Fan Module (CRFM). 1.3.3 Test must be conducted with production intent Compressor and Refrigerant Expansion Devices. 1.3.4 Test must be conducted with production intent refrigerant control software
13、 and calibrations as well as representative refrigerant control sensing devices (Evaporator Air Temperature Sensors, High Pressure transducers, Low Pressure Switches or transducers, etc.) See paragraph 4.1.7. Copyright General Motors Company Provided by IHS under license with General Motors CompanyN
14、ot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15775 Copyright 2012 General Motors Company All Rights Reserved September 2012 Page 2 of 12 Note: Consideration should be applied where the production intent control points change
15、with ambient temperature. The matrix included in this procedure does not comprehend the impact of variable control points in terms of the effective evaporator loading in regards to determining worst case frosting conditions. Using a fixed control point regarding ambient change during system frost co
16、ntrol development may enable a more robust frost control system. 1.3.5 Test shall be conducted with representative refrigerant plumbing (length, diameters and bends production representative). 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 Extern
17、al Standards/Specifications. None 2.2 GM Standards/Specifications. GMW7022 GMW7023 GMW15845 GMW16571 2.3 Additional References. GM Best Practice Documents. (The supplier shall work with the GM DRE to comprehend this requirement). International Organization for Standardization (ISO) Calibration proce
18、dures. 3 Resources 3.1 Facilities. Test to be run at a HVAC system bench and or Climatic Tunnel capable of simulating defined conditions. 3.1.1 Air temperature (0 to +40) C at both the condenser and evaporator. Evaporator humidity control (5 to 95) % RH, humidity control at the condenser not require
19、d. 3.1.2 Condenser Airflow quantity and distribution to simulate (0 to 130) km/h vehicle speeds and (0 to 100) % fan power levels. 3.1.3 Compressor rotational speeds (500 to 5000) min-1 (rpm). 3.2 Equipment. The following minimum instrumentation shall be used per procedure GMW15845 (Test Vehicle Ins
20、trumentation Procedure). 3.2.1 Pressure Taps. 3.2.1.1 Compressor out refrigerant pressure. 3.2.1.2 Evaporator out refrigerant pressure. 3.2.1.3 Compressor in refrigerant pressure. 3.2.1.4 Compressor crankcase refrigerant pressure (if applicable for variable displacement compressor). 3.2.1.5 Before e
21、vaporator core air static pressure. 3.2.1.6 Interior body air static pressure. For bench test use after evaporator air static pressure. 3.2.2 Thermocouples. 3.2.2.1 Evaporator out temperature (refrigerant, stinger). 3.2.2.2 Evaporator in temperature (refrigerant, stinger). 3.2.2.3 Compressor out ref
22、rigerant temperature. 3.2.2.4 Compressor in refrigerant temperature. 3.2.2.5 Thermocouple near (within 5 mm of thermistor element of) Evaporator Air Temperature (EAT) sensor (if applicable) or tube Thermocouple near (within 2 mm of thermistor element in contact with fins of) evaporator fin temperatu
23、re sensor (if applicable). 3.2.2.6 A thermocouple grid at evaporator air exit as described in GMW15845. Optionally, a similar grid measuring the evaporator metal tube temperature at similar locations may be desired. An advantage in using the additional metal tube contact temperature grid is when the
24、 delta temperature (the temperature difference) in thermal couple pairs increases, the data provides a clear identification of local ice formation. In all cases, avoid a situation where a thermocouple wire modifies or blocks the flow of air to the evaporator air grid and or the refrigerant capacity
25、control sensor. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15775 Copyright 2012 General Motors Company All Rights Reserved September
26、 2012 Page 3 of 12 3.2.3 Condensate volume flow rate (optional measurement during full vehicle tests) as captured from HVAC drain (graduated measurement cylinder recording at fixed time interval). 3.2.4 Climate Control Commands. 3.2.4.1 Blower Voltage and Current Draw. 3.2.4.2 For cycling compressor
27、 systems, Compressor clutch voltage. 3.2.4.3 For electrically commanded systems (EVDC or electrically driven compressors), either EVDC Pulse Width Modulated (PWM) duty cycle (%) or electrical compressor speed command (rpm). These will need to be recorded from control diagnostics. Optionally, a shunt
28、 can be used to measure the EVDC compressor control current. 3.2.4.4 If available and/or applicable, all refrigerant control sensor readings from control diagnostics (e.g., High-side and/or Low-side refrigerant pressure transducer(s), High-side and/or Low-side refrigerant temperature probes, Evapora
29、tor Air or Fin Temperature sensors). 3.3 Test Vehicle/Test Piece. 3.3.1 Test Vehicle. Vehicle representative of production intent and equipped as described in GMW15845 (Test Vehicle Instrumentation Procedure). 3.3.2 Components. Prepare compressor and evaporator with minimum set control valve or pres
30、sure switch/thermal switch at their minimum setting for use in the tests (largest positive error). 3.4 Test Time. Calendar time: 3 days Test hours: 16 hours Coordination hours: 4 hours 3.5 Test Required Information. Not applicable. 3.6 Personnel/Skills. Not applicable. 4 Procedure 4.1 Preparation. 4
31、.1.1 All applicable instrumentation shall be checked for certification to the International Organization for Standardization (ISO) calibration procedures. Submit this data sheet with other data sheets when the certification data is not otherwise preserved in the test laboratory records. 4.1.2 Prepar
32、e vehicle instrumentation as described in GMW15845 (Test Vehicle Instrumentation Procedure). 4.1.3 If testing the system on a bench as described in paragraph 4.3.2, a transparent plastic window in the HVAC module case to aid in evaporator core downstream viewing is recommended. Note: GMW16571 typica
33、lly is utilized when completing a bench test. 4.1.4 Climate control temperature setting adjusted to full cold for all tests. 4.1.5 Intake door shall be in the production intent fresh air position (Production Outside Air (P/OSA). (For automatic systems, lock the intake door in the fresh air position
34、unless this is not representative of a customer selectable intake position.) Note: As an option, the test matrix can be run additionally in a locked partial recirculation condition (e.g., 50% re-circulated air); if the HVAC Air handling Module design exhibits a significantly different inlet evaporat
35、or air temperature and moisture content distribution in this condition and partial recirculation is implemented as part of the climate control functionality. Note: This procedure typically applies to the primary evaporator in dual evaporator or evaporator/chiller applications. A chiller application
36、typically uses a glycol heat transfer media and is not subjected to freeze. A secondary evaporator typically has both dryer airflow (operates in a recirculation airflow mode) and a larger refrigerant pressure drop (resulting in a warmer second evaporator refrigerant) resulting in reduced risk for fr
37、ost formation. Where these typical conditions do not apply, then frost control measures and validation shall be executed. 4.1.6 Air Conditioner (A/C) compressor is to operate in all test conditions. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for Res
38、aleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15775 Copyright 2012 General Motors Company All Rights Reserved September 2012 Page 4 of 12 4.1.7 The calibration used for compressor control logic shall represent a worst case production va
39、riation temperature on the evaporator core. For example: A production intent calibration cycles the compressor off at +2.5 C and on at +4.0 C. The control error from the nominal test vehicle to the worst case variation control components (conditions which meet drawing requirements) is +0.8 C, where
40、the test vehicle is known to be centered in the variation band. A freeze test is using a nominal test vehicle; therefore the calibration should be robust to meeting frost requirements at the calibration of +1.7 C off and +3.2 C on. Variation in sensor thermal response (thermal lag) shall also be und
41、erstood. 4.1.8 Multiple evaporator systems shall be tested with only the primary evaporator transferring heat. Additional evaporators are to be connected to the refrigeration circuit but not transferring heat (water pumps or airflow blowers off). This situation enables the non operational evaporator
42、s or chillers to naturally sequester system refrigerant mass during operation, as this represents a typical customer frost environment. 4.2 Conditions. 4.2.1 Environmental Conditions. Thermal conditions (Ambient Air Temperature and Relative Humidity) are specified in Table 2 as part of the total tes
43、t matrix. 4.2.2 Test Conditions. Deviations from the requirements of this standard shall have been agreed upon. Such requirements shall be specified on component drawings, test certificates, reports, etc. Table A1 and Table A2 (Appendix A) shall be completed prior to the test if a HVAC System Test B
44、ench (see paragraph 4.3.2) will be used. 4.2.2.1 Road Load Coefficients. Test weight shall be set to curb weight plus 1 passenger when a vehicle is used for the test. 4.2.2.2 Solar Load. Solar lamps shall not be used during this test. Ambient tunnel lighting is permitted. 4.2.3 Refrigerant Charge Co
45、nditions. Consideration is necessary during bench system testing to account for system charge variation compared to full vehicle tests. The Test conditions of Table 2 shall be tested at: 4.2.3.1 Cycle 1. Critical Charge (Orifice Tube systems) or Operational Charge (TXV and EXV systems) as defined by
46、 GMW7022 (Refrigerant Charge Determination) to represent the refrigerant charge at the end of the vehicle service life. 4.2.3.2 Cycle 2. Production Refrigerant Charge (Operational or Critical charge plus reserve charge) as defined by GMW7022 (Refrigerant Charge Determination). 4.2.3.3 Gear Step or D
47、rive Positions. Table 1: Gear Step or Drive Positions Speed Transmission 50 km/h 80 km/h Speeds 80 km/h Idle Manual Transmission 4 speed. 4. 4. 4. Neutral Manual Transmission 5 speed 4 or 5.Note 1 5. 5. Neutral Manual Transmission 6 speed. 4 or 5.Note 1 5 or 6. Note 2 6. Neutral Automatic Transmissi
48、on. D (Highest Drive Gear) D (Highest Drive Gear) D (Highest Drive Gear) D (Highest Drive Gear) Note 1: Use 5th Gear (exception: use 4th Gear when engine displacement is 25 %, the evaporator is beginning to freeze and control countermeasures are required. Countermeasures include higher control valve
49、 settings (for variable capacity compressors), a higher temperature sensor calibration or pressure switch calibrations (for cycling or electrically controlled compressors) or the relocation of refrigerant control sensor(s). If countermeasures are applied, the test (or a subset of the most freeze-sensitive test points) should be re-run with the new control design. Note that the refrigerant charge variation in paragraph 4.2.3 will provide a difference in the evaporator temperature dis
