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Modeling of an Integrated Internal Heat Exchanger and Accumulator in R744 Mobile Air-Conditioning Applications

University of Illinois at Urbana-Champaign-Wenying Zhang, Predrag Hrnjak
  • Technical Paper
  • 2020-01-0153
To be published on 2020-04-14 by SAE International in United States
Carbon dioxide (R744) is one of the most promising next-generation refrigerants for mobile air-conditioning applications (MAC), which has the advantages of good heating performance in cold climates and environmental-friendly properties. In this paper, a simulation model of an integrated internal heat exchanger (IHX) and accumulator (ACC) was developed using the finite volume method via EES. The results were validated by experimental results from a transcritical R744 mobile heat pump, and the error was within ±5%. The impacts of mass flow rate, evaporator outlet quality and temperatures of high- and low-side streams on the heat transfer rate, effectiveness and charge of the integrated IHX/Acc were studied. Results show that the heat transfer rate of the IHX is mostly sensitive to the evaporator outlet quality. When the evaporator quality decreases from 0.9 to 0.6, the heat transfer rate increases from 1.1 to 2.4 kW and the superheat reduces from 25.8 to 9.4 ℃. As a result, the compressor discharge temperature and the heating capacity can be reduced. To obtain the maximized capacity, especially during the startup, an…
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A Control System for Maintaining Passenger Cabin Air Quality

Chulalongkorn University-Thanin Wangsawangkul, Thiti Maneepipat, Nattapong Sukumdhanakul, Porpin Pungetmongkol, Prabhath De Silva
DENSO International Thailand-Pradit Mahasaksiri
  • Technical Paper
  • 2020-01-1243
To be published on 2020-04-14 by SAE International in United States
This paper presents a control methodology to maintain vehicle cabin air quality within desirable levels, giving particular attention to gaseous contaminants carbon dioxide (CO2) and carbon monoxide (CO). The CO2 is generated by the occupant exhalation while the CO is assumed to be ingested with the incoming fresh air. The system is able to detect and improve cabin air quality by controlling the recirculation flap of the ventilation system to control the amount of fresh air intake. The methodology is demonstrated in the laboratory using controlled experiments with a production level automotive HVAC (Heating Ventilating and Air-Conditioning) module. The results indicated that the designed control system can work automatically and control the CO and CO2 gas concentrations within acceptable levels.
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A study on the effect of different glasses and its properties on vehicle cabin during soaking at hot ambient conditions using 1D simulation

FCA Engineering India Pvt., Ltd.-Karthik Subramanian, Prakashbabuji Danapalan, Saravanan Sambandan
FCA US LLC-Murali Govindarajalu
  • Technical Paper
  • 2020-01-0956
To be published on 2020-04-14 by SAE International in United States
Increase in traffic conditions and global increase in the ambient temperature during the summer season, heat load in the vehicle cabin is also increasing, creating a huge thermal discomfort for the passengers. There are two scenarios in which these adverse conditions can be a problem, one is when driving the vehicle in traffic condition and another one is when the vehicle is parked in the open sun both during the summer season. While for the first scenario, at least the air conditioner can be switched on, for the soaking scenario the cabin temperature can reach alarming levels which may have serious discomfort and health effects on the human entering vehicle. Although there are options of remote switching on of air conditioners, they are restricted to vehicles having an automatic transmission only. Considering the different parts of cabin, the glasses occupy majority of the portion which is exposed to the sunlight and that transmit the heat directly into the cabin, which in turn is absorbed by different materials resulting in alarming temperature levels in cabin when…
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Fuel consumption on different drive cycles: A unified approach based on average power/weight

Ford Motor Company-Patrick Phlips, William Ruona, Thomas Megli, Mrudula Orpe
  • Technical Paper
  • 2020-01-1278
To be published on 2020-04-14 by SAE International in United States
In previous work we have shown that fuel consumption on a particular drive cycle is proportional to traction work, with an offset for powertrain losses. The finding applies to different drive cycles, but with different offsets. Following Soltic (2011), it is shown that if fuel usage and traction work are both expressed in terms of cycle average power, a wide range of drive cycles collapse to a single transfer function. Data for vehicles of different weights further collapses when normalized for weight, i.e. by working in power/weight (P/W). The fuel P/W is primarily a function of traction P/W, and secondarily of displacement/weight. The useful work or power definition is then expanded beyond the traction power to include electrical power for customer functions, and power to drive the air conditioning. With this expanded definition the linear powertrain transfer function can be applied not only to strictly defined regulatory drive cycles and procedures, but also to ‘real driving’ conditions that cover a much broader range of situations. When applied to hybrid electric vehicles, the method clearly shows…
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Use of Partial Recirculation to Limit Build-Up of Cabin Carbon Dioxide Concentrations to Safe Limits per ASHRAE Standard-62

Calsonic Kansei North America Inc.-Gursaran Mathur
  • Technical Paper
  • 2020-01-1245
To be published on 2020-04-14 by SAE International in United States
Carbon dioxide exhaled by occupants remains within the cabin during operation of HVAC unit in recirculation mode. The CO2 inhaled by the occupants goes into their blood stream that negatively affects occupant’s health. ASHRAE Standard-621 specifies the safe levels of carbon dioxide in conditioned space for humans. The CO2 concentration limit per ASHRAE is 700 ppm over ambient conditions on a continuous basis. ASHRAE Standard-62 has an additional requirement for maintaining good air quality within the ambient condition. Per this requirement, we need to introduce a min of 15 cfm/person in the conditioned space to maintain good air quality. Even though this requirement is primarily for elimination the body odors, the author has investigated if this airflow requirement is also sufficient to maintain cabin CO2 concentrations as stated above. The author2 has conducted experimental studies by conducting tests on a vehicle to see if ASHRAE’s additional requirements to maintain good air quality is also sufficient to maintain cabin CO2 concentrations below ASHRAE Standard-62. Detailed results will be presented in the paper. REFERENCES 1. ASHRAE/ANSI, Standard…
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Investigate partial cabin air re-circulation strategy to improve HVAC system's heating performance using 1D simulation

FCA Engineering India Pvt., Ltd.-Saurabh Belsare, Prakashbabuji Danapalan, Saravanan Sambandan
FCA US LLC-Murali Govindarajalu
  • Technical Paper
  • 2020-01-0159
To be published on 2020-04-14 by SAE International in United States
In cold weather conditions, cabin heating performance is critical for retaining the thermal comfort. Heat is absorbed from the engine by circulating coolant through the engine water jacket and same will be rejected by the heater core. A variable speed blower is used to transfer heat from the heater core to the passenger compartment through floor ducts. The time taken to achieve comfortable cabin temperature determines the performance and capacity of heating ventilating and air conditioning (HVAC) system. In current automotive field, the engine options are provided to customers to meet their needs on the same vehicle platforms. Hence few engine variants cannot warm the cabin up to customer satisfaction. To improve the existing warm up performance of system, Positive thermal coefficient heater (PTC), electric coolant PTC heater, auxiliary pump etc. can be used which increases the overall cost of the vehicle. During warm-up, HVAC system operates in 100% fresh mode. In this study, Partial cabin re-circulation is investigated to understand the effect on the cabin warm-up. In order to demonstrate this phenomenon, a one…
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Impact of different types of glazing on Air- Conditioning system performance of vehicle

Maruti Suzuki India, Ltd.-Akshay Bhateja
  • Technical Paper
  • 2020-01-1249
To be published on 2020-04-14 by SAE International in United States
Due to intense peak summer temperatures and sunny summers in tropical countries like India, achieving the required cabin temperature in vehicle without compromising on fuel efficiency is becoming increasingly challenging. The major source of heat load on vehicle is solar load. Therefore, a study has been conducted to evaluate the heat load on vehicle cabin due to solar radiations and its impact on vehicle Air-Conditioning system performance with various combinations of door glasses and windscreen. The glasses used for this study are classified as Green, Dark Green, Dark Gray, Standard PVB (Polyvinyl Butyral) Windscreen and PVB Windscreen having Infrared Cut particles. For each glass, part level evaluation was done to find out the percentage transmittance of light of different wavelengths and percentage transmittance of heat flux through each glass. To verify the effectiveness of each glass, vehicle level Air-Conditioning system performance test was done in All Weather Chassis Dyno Facility for each retrofitted vehicle. Retrofitted vehicle configurations were decided as per regional visible light transmittance regulations. To eliminate the effect of manufacturing variance while evaluating…
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Multi-zone HAVC Development and Validation with Integrated Heated/Vented Seat Control

FCA US LLC-Murad Maghaireh, Michael Hoppe
  • Technical Paper
  • 2020-01-1247
To be published on 2020-04-14 by SAE International in United States
Vehicle multi zone automatic Heating , Venting and Air Conditioning (HVAC) is the advanced form of the traditional air conditioning, the advantage of multi zone automatic HVAC is that it allows the passengers of a vehicle to set a desired temperature for their own zone within the vehicle compartment. This desired temperature is then maintained by the HVAC system, which determines how best to control the available environment data that leads to a higher comfort for the passengers. To achieve ultimate thermal comfort of the occupants in a vehicle, multi zone HVAC takes things a step further by adding heated, vented seats and, steering wheel to the HVAC controller hardware as well as strategies. The heating and cooling of the occupants by this more advance one integrated system is performed by complex control algorithms in form of embedded software programs and private LIN network. This paper describes the approach and tools used to develop, simulate and validate the one integrated climate control system. Included are 1- introduction of an integrated HVAC , steering wheel and…
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Model-Based Calibration of an Automotive Climate Control System

BMW AG-Gerrit Lassahn, Kang Qiu
TU Munich-Patrick Jahn
  • Technical Paper
  • 2020-01-1253
To be published on 2020-04-14 by SAE International in United States
In modern cars the control of heating, ventilation and air-conditioning (HVAC) systems is oftentimes realized by means of a cascade of gain scheduling controllers. The calibration of this control cascade is a complicated and strenuous, hence expensive process. To establish a model based calibration process, a fast executing and accurate model of the HVAC system is required. This paper describes a novel approach for the modelling of an automotive HVAC system. The model consists of a black box model trained with experimental data from a self-developed measurement setup. It is capable to predict the temperature and mass flow of the air entering the vehicle cabin at the different outlets. The measurement setup is based on a combination of temperature and velocity sensors. A measurement fault analysis is conducted to validate the accuracy of the measurement system. As the data collection is done under fluctuating ambient conditions, an extensive analysis of the impact of different ambient conditions on the HVAC unit is performed and incorporated into correction models that account for the different ambient conditions. Different…
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Sound Evaluation of Flow-induced Noise with Simultaneous Measurement of Flow Regimes at TXV Inlet of Automotive Evaporators

University of Illinois-Stefan Elbel
University of Illinois at Urbana-Champaign-Yingyue Zhang
  • Technical Paper
  • 2020-01-1255
To be published on 2020-04-14 by SAE International in United States
In the air conditioning system, flow-induced noise is very disturbing, including the noise generated from the expansion device and the heat exchangers. In the past few decades, most researches related to flow-induced noise focused on the relationship between the flow regimes near the expansion device and the amplitude of flow-induced noise when the measurements are not synced. In this paper, an experimental-based approach is used to explore the simultaneous relationship between flow-induced noise characteristics and flow regimes at the inlet of TXV of evaporators used in automobiles. A pumped R134a loop with microphones and transparent sections is used to simulate the vapor compression system. Also, the paper evaluates the severity of flow-induced noise from not only the amplitude of noise but also the frequency of noise with a parameter called psychoacoustic annoyance (PA). One of the most disturbing flow-induced noise near the TXV is called gurgling noise and distributes around 9 kHz at an amplitude between 40 dB to 50 dB. When the TXV inlet is subcooled, the annoyance of flow-induced noise is substantially reduced.…