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2017-04-06
Event
Climate control is a defining vehicle attribute and is associated with brand image. Thermal performance and quality of climate control are both critical to customer satisfaction. The system has strong design interaction with other vehicle systems, while its primary objective is to deliver thermal comfort and occupant safety with low energy consumption. Localized Comfort, Secondary Fluids, Air Quality, Controls, System Sizing and HVAC consumer interface are just a few of the recent advances.
2017-04-05
Event
Climate control is a defining vehicle attribute and is associated with brand image. Thermal performance and quality of climate control are both critical to customer satisfaction. The system has strong design interaction with other vehicle systems, while its primary objective is to deliver thermal comfort and occupant safety with low energy consumption. Localized Comfort, Secondary Fluids, Air Quality, Controls, System Sizing and HVAC consumer interface are just a few of the recent advances.
2017-04-05
Event
Climate control is a defining vehicle attribute and is associated with brand image. Thermal performance and quality of climate control are both critical to customer satisfaction. The system has strong design interaction with other vehicle systems, while its primary objective is to deliver thermal comfort and occupant safety with low energy consumption. Localized Comfort, Secondary Fluids, Air Quality, Controls, System Sizing and HVAC consumer interface are just a few of the recent advances.
2017-03-28
Technical Paper
2017-01-0175
Jing He, Bill Johnston, Debasish Dhar, Loren Lohmeyer
The traditionally used refrigerant in mobile air conditioning (MAC), R134a, has a high GWP of 1,300 and is to be banned in EU market for new passenger cars and light commercial vehicles from January 1, 2017. In US, EPA has listed R134a as unacceptable for new light-duty vehicles beginning in Model Year 2021. The natural refrigerant, R744 (CO2), remains a viable solution to replace R134a due to its environmental friendliness, low cost, non-flammability, and high volumetric heat capacity. One challenge of R744 vapor compression system is reduced efficiency with ambient temperature. Prior research has demonstrated that a parallel or multistage compression cycle represents a superior design to a conventional single-compression cycle in that it not only improves the optimum cooling efficiency, but also brings down the optimum discharge pressure.
2017-03-28
Technical Paper
2017-01-0172
Suhas Venkatappa, Manfred Koberstein, Zhengyu Liu
Due to regulations related to global warming, the auto industry is transitioning to the use of a new refrigerant R1234yf in many markets/regions. This transition to the new refrigerant was considered to be a minor development effort with main focus on improved sealing, improving cooling capacity with adding content such as Internal Heat Exchanger (IHX) to recoup the lower cooling efficiency of R1234yf compared to R134a. There were no redesigns of major refrigerant system components expected with the introduction of R1234yf. The actual implementation of this refrigerant has proven to be more challenging due to several NVH issues. Some of the challenges related to NVH are driven by the differences in refrigerant characteristics – mass flow rate, velocity of sound in refrigerant.
2017-03-28
Technical Paper
2017-01-0183
Mingyu Wang, Timothy Craig, Edward Wolfe, Tim J LaClair, Zhiming Gao, Michael Levin, Danrich Demitroff, Furqan Shaikh
Without the waste heat available from the engine of a conventional automobile, electric vehicles (EVs) must provide heat to the cabin for climate control using energy stored in the vehicle. In current EV designs, this energy is typically provided by electrical energy from the traction battery. In very cold climatic conditions, the driving range of an EV can be reduced by 50% or more. To minimize this EV range penalty, a novel thermal energy storage system has been designed to provide cabin heat in EVs and Plug-in Hybrid Electric Vehicles (PHEVs) using the stored latent heat from an advanced phase change material (PCM). This system is known as the Electrical PCM-based Thermal Heating System (ePATHS). When the EV is connected to the electric grid to charge its traction battery, the ePATHS system is also “charged” by melting the PCM. The stored thermal energy is subsequently deployed for cabin heating during driving.
2017-03-28
Technical Paper
2017-01-0171
Quansheng Zhang, Yan Meng, Christopher Greiner, Ciro Soto, William Schwartz, Mark Jennings
In this paper, the tradeoff relationship between the Air Conditioning (A/C) system performance and vehicle fuel economy for a hybrid electric vehicle during the SC03 drive cycle is presented. First, an A/C system model was integrated into Ford’s HEV simulation environment. Then, a system-level sensitivity study was performed on a stand-alone A/C system simulator, by formulating a static optimization problem which minimizes the total energy use of actuators, and maintains an identical cooling capacity. Afterwards, a vehicle-level sensitivity study was conducted with all controllers incorporated in sensitivity analysis software, under three types of formulations of cooling capacity constraints. Finally, the common observation from both studies, that the compressor speed dominates the cooling capacity and the EDF fan has a marginal influence, is explained using the thermodynamics of a vapor compression cycle.
2017-03-28
Technical Paper
2017-01-0163
Gursaran D. Mathur
In southern states (e.g., Arizona) typically people drive their vehicles in summer by running vehicle’s air conditioning systems in recirculation modes only. Carbon dioxide exhaled by occupants remains within the cabin during operation in recirculation mode. The concentration of carbon dioxide starts increasing in the cabin. The CO2 that is inhaled by the occupants goes into their blood stream that negatively affects occupant’s health. ASHRAE Standard 62 specifies the safe levels of carbon dioxide in conditioned space for humans. The CO2 concentration limit per ASHRAE is 700 ppm over the ambient conditions on a continuous basis. Current global average ambient concentration level of CO2 as of March 2015 (NOAA, 2016) is approximately 401 ppm. Hence, if the CO2 concentration exceeds approximately 1100 ppm inside of a home or a vehicle cabin, then we must introduce outside air into the home or vehicle cabin to reduce the CO2 concentration.
2017-03-28
Technical Paper
2017-01-0169
Ward J. Atkinson, William Raymond Hill, Gursaran D. Mathur
The EPA has issued regulations in the Final Rulemaking for 2017-2025 Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards (420r12901-3). This document provides credits against the fuel economy regulations for various Air Conditioning technologies. One of these credits is associated with increased use of re-circulation air mode, when the Ambient is over 24°C (75°F.). The authors want to communicate the experiences in their careers that highlighted issues with air quality in the interior of the vehicle cabin. Cabin contamination sources may result in safety and health issues for both younger and older drivers. Alertness concerns may hinder their ability to operate a vehicle safely.
2017-03-28
Technical Paper
2017-01-0155
Yongbing Xu, Gangfeng Tan, Xuexun Guo, Xianyao Ping
When it is a bit hot in the vehicle during the driving process, the closed cabin temperature still needs to be cooled down. Though the use of car air-condition can cool down the closed cabin temperature, it needs to start and stop the compressor frequently, which increases the parasitic power of the engine and shorten the life-span of the compressor. With the use of semiconductor auxiliary cooling system to regulate the cabin temperature, the system noise is small and the temperature control precision is high. But the system is inefficiency and the energy consumption is high. This research considered the effects of different body heat producing and transferring characteristics, environment temperature and vehicle speed on the capacity of the system overall, and made the semiconductor auxiliary cooling system in a range of low power consumption under the condition of ensuring human comfort.
2017-03-28
Technical Paper
2017-01-0143
Neelakandan Kandasamy, Steve Whelan
During cabin warm-up, effective air distribution by vehicle climate control systems plays a vital role. For adequate visibility to the driver, major portion of the air is required to be delivered through the defrost center ducts to clear the windshield. Which results in thermal interaction between warm air delivered from the HVAC unit and the cold windshield. This creates thermal losses since the windshield acts as a heat sink, which delays the heating of passenger compartment causing delay in time to providing thermal comfort to the passenger. Thus it becomes essential to predict the effect of different windscreen defrost characteristics and its impact on occupant thermal comfort. In this paper, sensitivity analysis is carried for different windscreen defrosts characteristics like ambient conditions modes of operation; change in material properties along with occupant thermal comfort is predicted. An integrated 1D/3D CFD approach is proposed to evaluate the same.
2017-03-28
Technical Paper
2017-01-0186
Cory J. Kreutzer, John Rugh, Jeff Tomerlin
Increased market penetration of electric drive vehicles (EDVs) requires overcoming a number of hurdles including limited vehicle range and the elevated cost of EDVs in comparison to conventional vehicles. Climate control loads have a significant impact on range, cutting it by over 50% in both cooling and heating conditions. In order to minimize the impact of climate control on EDV range, the National Renewable Energy Laboratory has partnered with Hyundai America and key industry partners to quantify the performance of thermal load reduction technologies on a Hyundai Sonata PHEV. Technologies that impact vehicle cabin heating in cold weather conditions and cabin cooling in warm weather conditions were evaluated. Tests included thermal transient and steady-state periods for all technologies, including the development of a new test methodology to evaluate the performance of occupant thermal conditioning.
2017-03-28
Technical Paper
2017-01-0167
Steven Lambert, William Jamo, Mike Kurtz
Purpose: Determine the effectiveness of flushing a contaminated automotive A/C system with a refrigerant recovery and recharge machine, using refrigerant as a flushing agent. The current flushing method uses solvent flushing. Methodology: Introduce contamination into the vehicle A/C system to induce a compressor failure. Run the vehicle A/C system at various speeds and engine RPM’s until the compressor fails. Certified Arizona Dust is the contaminant chosen for this study. Flush contaminated components using various manufactures A/C recovery and recharge machines using refrigerant as a flush agent. Flush components at different time intervals of 15, 30, 40 and 60 minutes for each machine being tested. Machines that were used for this test had continuous loop flushing capability. The current solvent flush time is 15 minutes flushing and 30 minutes purge for a total time of 45 minutes. Flushed components are evaluated to determine the amount of contamination removal.
2017-03-28
Technical Paper
2017-01-0177
Lili Feng, Predrag Hrnjak
This paper presents the study of refrigerant charge imbalance between A/C mode and HP mode of a mobile reversible system. Sensitivities of cooling and heating capacity and energy efficiency with respect to refrigerant charge are looked into experimentally and numerically. Optimum refrigerant charge level for A/C mode is found to be larger than that for HP mode, primarily due to larger condenser size in A/C mode. Refrigerant charge retention in components at both modes are measured in the lab by quick close valve method. Modeling of charge retention in heat exchangers is compared to experimental measurements. Effect of charge imbalance on oil circulation is also discussed.
2017-03-28
Technical Paper
2017-01-0181
Benny Johnson William, Agathaman Selvaraj, Manjeet Singh Rammurthy, Manikandan Rajaraman, V. Srinivasa Chandra
The modern day automobile customers’ expectations are sky-high. The automotive manufacturers need to provide sophisticated, cost-effective comfort to stay in this competitive world. Air conditioning is one of the major features which provides a better comfort but also adds up to the increase in operating fuel cost of vehicle. According to the sources the efficiency of internal combustion engine is 30% and 70% of energy is wasted to atmosphere. The current Air conditioners in automobiles use Vapour compression system (VCS) which utilizes a portion of shaft power of the engine at its input; this in turn reduces the brake power output and increases the specific fuel consumption (SFC) of the engine. With the current depletion rate of fossil fuels, it is necessary to conserve the available resources and use it effectively which also contributes to maintain a good balance in greenhouse effect thus protecting the environment.
2017-03-28
Technical Paper
2017-01-0162
Jun Li, Lili Feng, Pega Hrnjak
This paper presents the results of an experimental study to determine the effect of vapor-liquid refrigerant separation in a microchannel condenser of a MAC system. R134a is used as the working fluid. A condenser with a separation and a baseline condenser identical on the air side have been tested to evaluate the difference in the performance due to separation. Two categories of experiments have been conducted: the heat exchanger-level test and the system-level test. In the heat exchanger-level test it is found that the separation condenser condenses up to 7.4% more mass flow than the baseline at the same inlet and outlet temperature (enthalpy); the separation condenser condenses the same mass flow to the lower temperature than the baseline condenser does. In the system-level test, COP is compared under the same superheat, subcooling and refrigerating capacity. Separation condenser shows from 1.3% to 6.6% a higher COP than the baseline condenser.
2017-03-28
Technical Paper
2017-01-0161
Dandong Wang, Cichong Liu, Jiangping Chen
This study investigates the cycle performance and potential advantages of the replacement of fin-and-tube evaporator with parallel flow micro-channel evaporator, in R134a roof-top bus air conditioner system. The heat exchanger for the bus system are featured by a stringent space height limitation. Based on the space requirement, micro-channel evaporator with horizontal configuration and vertical configuration are both designed and manufactured. 4 or 6 piece micro-channel evaporators are parallel installed in an 8 m bus air conditioner, instead of the original two piece fin-and-tube evaporators. Additionally, each evaporator employs a single thermostatic expansive valve (TXV) to control outlet superheat, which aims to cope with the problem of refrigerant mal-distribution among multi micro-channel evaporators. Except the replacement of evaporator, TXV and the adjustment of connecting pipe, other cycle components are kept same.
2017-03-28
Technical Paper
2017-01-0173
Stephen Andersen, Sourav Chowdhury, Timothy Craig, Sangeet Kapoor, Jagvendra Meena, Prasanna Nagarhalli, Melinda Soffer, Lindsey Leitzel, James Baker
This paper quantifies and compares the cooling performance and refrigerant and fuel cost savings to automobile manufacturers and owners of secondary-loop mobile air conditioners (SL-MACs) using refrigerants hydrofluorocarbon (HFC)-134 and the available alternatives HFC-152a and HFO-1234yf. HFC-152a and HFO-1234yf are approved for use by the United States Environmental Protection Agency (US EPA) and satisfy the requirements of the European Union (EU) F-Gas Regulations. HFC-152a is inherently more energy efficient than HFC-134a and HFO-1234yf and in SL-MAC systems can generate cooling during deceleration, prolong comfort during idle stop (stop/start), and allow powered cooling at times when the engine can supply additional power with the lowest incremental fuel use. SL-MAC systems can also reduce the refrigerant charge, emissions, and service costs of HFO-1234yf.
2017-03-28
Technical Paper
2017-01-0174
Ravi Rungta, Noori Pandit
A simple, fast, and inexpensive screening corrosion test has been developed that will supplement the currently utilized SWAAT test (ASTM G85) to evaluate relative corrosion performance of condensers from various suppliers and using differing material combinations and manufacturing processes including CAB brazed Silfluxed tube, zinc sprayed tube, and bare folded tube. The SWAAT test is utilized with no failure in 21 days as the “PASS” criterion. Most condensers tend to “pass” this test which makes it difficult to compare corrosion performance of the condensers supplied by various manufacturers. This paper will present the development of test parameters and the initial results. The test replicates the mode of attack observed in SWAAT as well as field returned units.
2017-03-28
Technical Paper
2017-01-0166
Noori Pandit
The effects of substituting a 12 mm thick subcool on top condenser in place of a 16 mm subcool on bottom condenser are evaluated in a vehicle level AC pull down test. The A to B testing shows that a thinner condenser with subcool on top exhibits no degradation in AC performance while resulting in a lower total system refrigerant charge. The results are from vehicle level tests run in a climatically controlled vehicle level wind tunnel to simulate an AC pull down at 43C ambient. In addition to cabin temperature and AC vent temperatures, comparison of compressor head pressures was also done. The conclusion of the study was that a standard 16 mm thick IRD condenser can be replaced by a 12 mm thick subcool on top IRD condenser with no negative effects on performance.
2017-03-28
Technical Paper
2017-01-1444
Mitali Chakrabarti, Alfredo Perez Montiel, Israel Corrilo, Jing He, Angelo Patti, James Gebbie, Loren Lohmeyer, Bernd Dienhart, Klaus Schuermanns
CO2 exposure is a serious health risk for people if the concentration of CO2 is over the acceptable threshold. The severity of the risk depends on the concentration of CO2 and the length of the exposure. In an automobile, where the interior cabin is a closed volume (with minimal venting), the increase in concentration is detrimental to the customer but hard to detect. For applications where CO2 is used as the refrigerant for the air-conditioning system, the risk of CO2 exposure is increased due to the possibility of CO2 leakage into the cabin through the duct system. The initiation of the leak could be due to a crash event or a malfunction of the refrigerant system. In this paper, CFD is used to simulate the concentration of CO2 in the event of a leak. The methodology along with the advantages and limitations will be discussed. The simulations are being carried out in a C-segment car with five occupants in panel recirculation mode, as shown in the picture below.
2017-03-28
Technical Paper
2017-01-0179
Saravanan Sambandan, Manuel Valencia, Sathish Kumar S
Abstract In current automotive industry, the necessity of providing quick warm up of the cabin during extreme cold conditions becomes more challenging to the engineers. A Trade-off between development time, cost and desired performance has to be achieved for deciding the right combination of HVAC (Heating ventilating air-conditioning) components to meet the customer satisfaction. In the HVAC, heater system plays a major role during winter condition to provide passenger comforts as well as to clear windshield defogging/deicing. The heater system consists of heater core, engine coolant as inner medium and air as outer medium. The coolant is circulated by engine coolant/water pump carrying heat from engine and flows across the heater core. The HVAC blower provides air to the cabin by taking heat from the heater core through floor duct systems thus warm up the cabin.
2017-03-28
Technical Paper
2017-01-0164
Venkatesan Muthusamy, S. Sathish Kumar, Saravanan Sambandan
ABSTRACT In an automotive air-conditioning system, the passenger comfort in the vehicle cabin gained importance and designing a right HVAC (Heating Ventilating and Air conditioning system) unit plays a vital role during the upfront design stage. Predicting the performance of cabin cool down rate upfront in the initial design stage will help us to reduce the overall product development time. To meet the customer comfort it is necessary to validate the HVAC performance at vehicle level in the extreme hot or cold ambient conditions. The vehicle which is having higher seating capacity will have higher thermal load and providing the thermal comfort to the passenger is the challenging task for the automotive HVAC industry. The dual HVAC unit is generally used to provide uniform cooling to the larger cabin volume.
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