1、 WORLDWIDE ENGINEERING STANDARDS Test Procedure GMW16571 Air Conditioning Evaporator Core Condensate Freeze Development Procedure for Refrigeration Systems with Temperature Sensors Evaporator Air Temperature (EAT) or Evaporator Fin Temperature (EFT) Copyright 2011 General Motors Company All Rights R
2、eserved November 2011 Originating Department: North American Engineering Standards Page 1 of 11 1 Scope Note: Nothing in this standard supercedes applicable laws and regulations. Note: In the event of conflict between the English and domestic language, the English language shall take precedence. 1.1
3、 Purpose. Evaporator core freeze results in reduced compressor oil circulation and can result in compressor damage. The purpose of this test is to determine whether the control of the compressor cycling (clutch control), variable displacement mechanism (Electronic Variable Displacement Control (EVDC
4、), or compressor speed (Electric Compressor) adequately protects the evaporator from condensate freeze. Note: The refrigerant charge variation included in this test is not sufficient to evaluate condensate freeze below a critical refrigerant charge (as defined by GMW7022), (i.e., GMW16571 is not a l
5、ow refrigerant charge evaluation test). 1.2 Foreword. This test procedure is intended to be used to collect data for vehicle climate control decisions during Heating Ventilation and Air Conditioning (HVAC) system development. As a test technique to develop and verify the optimal location of the refr
6、igerant control sensors (Evaporator Air or Fin Temperatures). A refrigeration bench is required for this evaluation and a clear plastic window or camera to view frost formation on the evaporator (inside the HVAC Module) is required. As a test technique to develop initial calibrations with a proposed
7、 sensor placement and production intent control design that will provide robust protection from evaporator condensate freeze under applicable conditions expected to be encountered for the vehicles intended usage. As a system development test to define an appropriate factor of safety necessary for a
8、robust system calibration. During system development, it is necessary to modify the intended capacity control system and to lower the control set point to the cause of condensate freeze formation. This frost formation data along with component variation analysis is used to predict expected customer
9、satisfaction. Note: GMW15775 is a complementary vehicle level test to perform final system verification around evaporator condensate freeze with production intent sensor designs/placements, controller, software and calibrations under a robust set of vehicle operating conditions. 1.3 Applicability. T
10、his test procedure is intended for use on HVAC systems with temperature based control systems on a climatic test bench. These conditions must be met for valid results of the testing. 1.3.1 Tests must be conducted with representative air handling conditions at the evaporator air inlet and exit (typic
11、ally this means testing with a complete and representative HVAC Module). 1.3.2 Tests must be conducted with representative air flow conditions at the condenser air inlet and exit. Typically this means testing with a complete and representative Condenser Radiator Fan Module (CRFM). 1.3.3 Tests must b
12、e conducted with production intent compressor and refrigerant expansion device(s). 1.3.4 Tests must be conducted with refrigerant control software and calibrations as well as representative refrigerant control sensing devices (Evaporator Air or Fin Temperature Sensors, High Pressure Transducers, Low
13、 Pressure Switches or Transducers, etc.) Note: Consideration should be applied where the production intent control points change 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 r
14、egards to determining worst case frosting conditions. Using a 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 GMW16571 Copyright 2011 Genera
15、l Motors Company All Rights Reserved November 2011 Page 2 of 11 fixed control point regarding ambient change during system frost control development will enable a more robust frost control system. Ambient variation will require additional test conditions as the transition points must also be evaluat
16、ed. 1.3.5 Development testing 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 External Standards/Specifications. None 2.2 GM Stand
17、ards/Specifications. GMW7022 GMW15775 GMW7023 GMW15845 2.3 Additional References. None. 3 Resources 3.1 Facilities. Test to be run at a HVAC system bench capable of simulating defined conditions. A vehicle and climatic wind tunnel can be used where a HVAC system bench is not available. A bench test
18、is recommended due to the expected inability to visualize and quantify ice formation on the evaporator during vehicle operation. This test requires visualization of ice formation on the evaporator core. 3.1.1 Relative humidity air conditions of 5 C to 40 C at 5 to 95% at both the condenser and evapo
19、rator. 3.1.2 Condenser airflow quantity and distribution to simulate 0 to 120 km/h vehicle speeds and 0 to 100% fan power levels. 3.1.3 Compressor rotational speeds 500 to 5000 revolutions per minute (rpm) (or as appropriate for electric drive compressors). 3.2 Equipment. The minimum instrumentation
20、 shall be used per procedure GMW15845 (Test Vehicle Instrumentation 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. 3.2.2 Thermoco
21、uples. 3.2.2.1 Evaporator out temperature (refrigerant, stinger). 3.2.2.2 Evaporator in temperature (refrigerant, stinger preferred). 3.2.2.3 Compressor out refrigerant temperature. 3.2.2.4 Compressor in refrigerant temperature. 3.2.2.5 Thermocouple near (within 5 mm of thermistor element of) Evapor
22、ator Air Temperature (EAT) sensor (if applicable) or tube thermocouple near (within 2 mm of thermistor element in contact with fins of) evaporator fin temperature sensor (if applicable). 3.2.2.6 A thermocouple grid at evaporator air exit as described in GMW15845. Optionally, a similar grid measuring
23、 the evaporator metal tube temperature at similar locations may be desired. An advantage in using the additional metal tube temperature grid is that when the delta temperature (temperature difference) in thermal couple pairs increases, it provides a clear identification of local ice formation at loc
24、ations that may not be visible in the evaporator core viewing window or camera angle. 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 control sensor. 3.2.3 Climate Control Commands. 3.2.3.1 Blower
25、 voltage and current draw. 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 GMW16571 Copyright 2011 General Motors Company All Rights Reserve
26、d November 2011 Page 3 of 11 3.2.3.2 Compressor clutch voltage, if applicable. 3.2.3.3 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 temperat
27、ure probes, evaporator air or fin temperature sensors. 3.3 Test Vehicle/Test Piece. 3.3.1 Test Bench. Components of the refrigeration system representative of production intent and equipped with instrumentation as described in GMW15845 (Test Vehicle Instrumentation Procedure). 3.3.2 Components. Inse
28、rt an evaporator face view window (clear plastic window) or HVAC Module internal camera to allow vision of frost formation on the face of the evaporator core. 3.4 Test Time. Calendar time: 3 days Test hours: 32 hours Coordination hours: 4 hours 3.5 Test Required Information. Not applicable. 3.6 Pers
29、onnel/Skills. Not applicable. 4 Procedure 4.1 Preparation. 4.1.1 Prepare bench instrumentation as described in GMW15845 (Test Vehicle Instrumentation Procedure). 4.1.2 A transparent plastic window or internal camera in the HVAC module case to aid in evaporator core downstream viewing is required. 4.
30、1.3 Climate control temperature setting shall be adjusted to full cold for all tests. 4.1.4 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 unless this is not representative of a
31、customer selectable intake position). 4.1.5 Air Conditioner (AC) compressor is to operate in all test conditions. 4.2 Conditions. 4.2.1 Environmental Conditions. Thermal conditions (Ambient Air Temperature and Relative Humidity) are specified in Table 1. 4.2.2 Test Conditions. Deviations from the re
32、quirements 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 are to be completed prior to the test if a HVAC System Test Bench (4.3.1.2) will be used. 4.2.3 Refrigerant Charge Conditions. T
33、he environmental conditions of Table 1 shall be tested. 4.2.3.1 Cycle 1. Critical Refrigerant Charge as defined by GMW7022. This will represent 70% of production refrigerant charge in many systems, but systems with reduced leakage may have less weight of reserve refrigerant, and a 70% charge would t
34、hen represent a situation where the system performance will not satisfy the customer in terms of AC performance as well as compressor durability (70% would represent operation well below critical charge for low leak systems). 4.2.3.2 Cycle 2. Production Refrigerant Charge (critical charge plus reser
35、ve charge) as defined by GMW7022. 4.3 Instructions. 4.3.1 HVAC System Test Bench Instruction. 4.3.1.1 Acclimation is not required. 4.3.1.2 The bench shall be set up to provide total Condenser Radiator Fan Module (CRFM) flow and compressor speed inputs as measured from prior full vehicle tests. Utili
36、ze Appendix A Table A1 for the input at the required CRFM and compressor conditions. 4.3.1.3 The blower voltage should be compensated to simulate dynamic system airflow in customer selectable Outside Air supply conditions as measured from prior vehicle tests. Utilize Appendix A Table A2 for the data
37、 required for input at the test conditions. 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 GMW16571 Copyright 2011 General Motors Company A
38、ll Rights Reserved November 2011 Page 4 of 11 4.3.1.4 The compressor operation speed shall be representative of 110 km/h unless noted otherwise. 4.3.1.5 Multiple evaporator systems are to be tested with only the primary evaporator transferring heat. Additional evaporators are to be connected to the
39、refrigeration circuit but not transferring heat. This situation is utilized to enable the non-functional evaporators or chillers to naturally sequester system refrigerant mass during operation, as this represents a typical customer frost environment. 4.3.2 Test Instructions to Support Control Sensor
40、 Placement. The test sequence consists of 2 cycles. Two (2) cycles are necessary to ensure the vehicle will meet frost requirements during the vehicle service life. Refrigerant temperature distribution within the evaporator has a strong impact on frost formation, and refrigerant distribution at the
41、local sensor location can change significantly as the system refrigerant charge level is reduced during normal vehicle aging. The two refrigerant charge levels stipulated in this procedure provide the engineer an indication of the functionality inherent with the chosen capacity control method. Note:
42、 Utilize an initial evaporator fin or air temperature freeze control calibration that is expected to cause minor ice formation (7 cm2 area) during some points of the test matrix. Proper placement of the core temperature sensor requires knowledge of the geometry of initial formed ice. This knowledge
43、will be gained during the completion of this procedure. It will be necessary to move the fin or air sensor if the sensor is not responsive after minor ice formation, Minor ice formation shall not block airflow to the sensor and, A proper location shall become cooler once minor ice is formed on the e
44、vaporator core. 4.3.2.1 Charge the refrigeration system as defined in section 4.2.3 accordingly for Cycle 1 or Cycle 2. 4.3.2.2 Stabilize the tunnel or HVAC system bench at Table 1 Test Point 8. Stabilization is defined by compressor outlet pressure stability of 15 kPa and evaporator grid average te
45、mperature stability of 1 C or cyclic peak stability as applicable. 4.3.2.3 After the system has stabilized, record for 60 minutes. Compressor out refrigerant pressure Evaporator out refrigerant pressure Compressor in refrigerant pressure Compressor out refrigerant temperature Evaporator in refrigera
46、nt temperature Evaporator out refrigerant pressure Compressor in refrigerant pressure Before evaporator air static pressure Body air static pressure or after evaporator air static pressure Blower amps Blower volts Evaporator grid temperatures All climate control sensors and commands (temperatures an
47、d/ or pressures) All thermocouple near air/fin sensor temperatures Clutch voltage command View frost formation pattern on evaporator core, capture image with a camera for later analysis. Note: Make sure that all data (less photography) is acquired at a minimum of 1 Hz, so that results from compresso
48、r capacity commands will have adequate resolution. If minor ice formation does not occur, revise the freeze control calibration to obtain approximately 7 cm2 of evaporator ice at some point in the data capture period. 4.3.2.4 Verify the placement of the evaporator sensor. With minor ice formation (7
49、 cm2) present on the face of the evaporator, the sensor shall 1) have no airflow restriction and, 2) remain responsive (trend colder in sensor temperature signal in comparison to no ice formation) to evaporator temperature. 4.3.2.5 Repeat 4.3.2.1 thru 4.3.2.4 for Cycle 2. 4.3.3 Evaluate Sensor Placement. If a) airflow to the sensor is restricted by ice formation and/or b) the measured temperature of the sensor trends warmer after localized
