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2017-04-04
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
2017-01-0161
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
2017-01-0164
Venkatesan Muthusamy, Sathish Kumar S, 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.
2017-03-28
Technical Paper
2017-01-0178
Mark Hepokoski, Allen Curran, Sam Gullman, David Jacobsson
Passive sensor (HVAC) manikins have been developed to obtain high resolution measurements of environmental conditions across a representative human body form. These manikins incorporate numerous sensors that measure air velocity, air temperature, radiant heat flux, and relative humidity. The effect of a vehicle’s climate control system on occupant comfort can be characterized from the data collected by an HVAC manikin. Equivalent homogeneous temperature (EHT) is often used as a first step in a cabin comfort analysis, especially since it reduces a large data set to a single intuitive number. However, the applicability of the EHT for thermal comfort assessment is limited since it does not account for human homeostasis, i.e., that the human body actively counter-balances heat flow with the environment in order to maintain a constant core temperature.
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
2017-01-0170
Aditya Velivelli, David Marquette
ABSTRACT
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 system performance and vehicle fuel economy for electrified vehicles during SC03 drive cycle is presented. First, an air conditioning system model was integrated into the Vehicle Model Architecture (VMA) and Simulink-CVSP (S-CVSP) according to the locations of subsystems and control features. Then, an open-loop sensitivity study is performed on the stand-alone ACDC simulator without controller incorporated at a fixed time step as well as over a drive cycle by formulating a static optimization problem minimizing the total actuator energy use and maintains identical cooling capacity as the benchmark. Afterwards, a closed-loop sensitivity study conducted on a ModeFrontier project with respect to three types of formulations of cooling capacity constraints.
2017-03-28
Technical Paper
2017-01-0180
Jun Li, Pega Hrnjak
This paper introduces the concept of separation of two-phase flow in condenser as a way to improve condenser efficiency. The benefits of vapor-liquid refrigerant separation and the reason why it will improve the condenser performance are explained. Numerical studies are presented on the effects of separation on performance of an R134a microchannel condenser. A modeling comparison with a baseline parallel flow microchannel condenser demonstrates that the separation condenser can condense a higher flow rate. The condenser refrigerant outlet temperature of the separation condenser is lower than the baseline by up to 0.7°C at the same refrigerant inlet state, based on the model prediction. In addition, condenser pass circuiting with pre-assumed separation results in the header is investigated by the model and results are presented.
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
2017-01-0181
Benny Johnson William, Manjeet Singh Rammurthy, Agathaman Selvaraj, Manikandan Rajaraman, Srinivasa Chandra V
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
2017-01-0177
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
2017-01-0162
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
2017-01-0176
B. Vasanth
The main function of mobile air conditioning system in a vehicle is to provide the thermal comfort to the occupants sitting inside the vehicle at all environmental conditions. Passenger thermal comfort is mainly influenced by the inside cabin temperature and airflow flows through the duct system. The function of ducts is to get the sufficient airflow from the HVAC system and distribute the airflow evenly throughout the cabin. The main focus for all OEMs is to optimize the design of the duct system and satisfy the target requirements such as airflow, velocity and temperature. In this paper, the focus is to optimize the rear passenger floor duct system to meet the target requirements through design for six sigma (DFSS) methodology. Normally floor duct design is evaluated by the target airflow, velocity and temperature achieved at passenger leg locations.
2017-03-28
Technical Paper
2017-01-0179
Saravanan Sambandan
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
2017-01-0163
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
2017-01-0168
B. Vasanth
In current scenario, there is an increasing need to have faster product development and achieve the optimum design quickly. In an automobile air conditioning system, the main function of HVAC third row floor duct is to get the sufficient airflow from the rear heating ventilating and air-conditioning (HVAC) system and to provide the sufficient airflow within the leg locations of passenger. Apart from airflow and temperature, fatigue strength of the duct is one of the important factors that need to be considered while designing and optimizing the duct. In the vehicles having third row seat, floor duct is connected to the rear HVAC and it is routed under the seat below the carpet to provide the airflow. Passenger would keep the luggage in the third row carpet area by unfolding the seat and there is a chance that passenger might walk over the duct routing carpet area. Due to the overloading of luggage, duct might get damaged or deformed.
2017-03-28
Technical Paper
2017-01-0165
Jingwei Zhu, Stefan Elbel
Expansion work recovery by two-phase ejector is known to be beneficial to vapor compression cycle performance. However, one of the biggest challenges with ejector vapor compression cycle is that the ejector cycle performance is sensitive to working condition changes which are common in real world applications. Different working conditions require different ejector geometries to achieve maximum performance. Slightly different geometries may result in substantially different COPs under the same conditions. Ejector motive nozzle throat diameter (motive nozzle restrictiveness) is one of the key parameters that can significantly affect COP. This paper presents the experimental investigation of a new motive nozzle restrictiveness control mechanism for two-phase ejectors used in vapor compression cycles, which has the advantages of being simple, potentially less costly and less vulnerable to clogging.
2017-03-28
Technical Paper
2017-01-0448
Prakash T. Thawani, Stephen Sinadinos, John zvonek
Prakash Thawani, Steve Sinadinos and John Zvonek DENSO International America Inc. Southfield, MI Abstract With the advent of EVs/HEVs and implementation of Idle-Stop-Start (ISS) technologies on internal combustion engine driven cars/trucks to improve fuel economy and reduce pollution, refrigerant sub-system (RSS) induced noise phenomena like, hissing, gurgling and tones become readily audible and can result in to Customer complaints and concerns. One of the key components that induces these noise phenomena is the Thermal Expansion Valve (TXV). The TXV throttles compressed refrigerant through the evaporator that results in air-conditioning (A/C) or thermal system comfort and defogging when needed. Under certain operating conditions, the flow of gas and/or liquid/gas refrigerant at high pressure and velocity excites audible acoustical and structural modes inherent in the tubing/evaporator/HVAC case.
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
2017-01-0172
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
2017-01-0174
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
2017-01-0182
Gautam Peri, Saravanan Sambandan, Sathish Kumar S
The intended primary objective of a passenger vehicle air conditioning system is to ensure thermal comfort to the passengers seated inside at all prevailing conditions. Presently 1D analysis plays a major role in determining the conformation of the selected system to achieve the desired results. Virtual analysis thus saves a lot of time, cost and effort in predicting the system performance in the initial development phase of the vehicle HVAC systems. A variety of parameters play an important role in achieving the above thermal comfort. In order to optimize the simulation, predicting the duct losses and cabin interior temperatures plays a vital role. Physical and geometrical parameters of the cabin are accurately modelled by considering all the parameters such as glass and sheet metal surfaces, air gaps, solar angles, solar intensity, instrumentation panel, firewall etc.
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