Taeyoung Han

Virtual Thermal Comfort Engineering

Simulation of passenger compartment climatic conditions is becoming increasingly important as a complement to wind tunnel and field testing to help achieve improved thermal comfort while reducing vehicle development time and cost. Delphi Harrison Thermal Systems has collaborated with the University of California, Berkeley to develop the capability of predicting occupant thermal comfort to support automotive climate control systems. At the core of this Virtual Thermal Comfort Engineering (VTCE) technique is a model of the human thermal regulatory system based on Stolwijk’s model but with several enhancements. Our model uses 16 body segments and each segment is modeled as four body layers (core, muscle, fat, and skin tissues) and a clothing layer. The comfort model has the ability to predict local thermal comfort level of an occupant in a highly non-uniform thermal environment as a function of air temperature, surrounding surface temperatures, air velocity, humidity, direct solar flux, as well as the level of activity and clothing type of each individual. VTCE takes into account the geometrical configuration of the passenger compartment including glazing surfaces, pertinent physical and thermal properties of the enclosure with particular emphasis on glass properties. Use of Virtual Thermal Comfort Engineering (VTCE) will allow for exploration of different climate control strategies as they relate to human thermal comfort in a quick and inexpensive manner.

Effects of spray conditions on coating formation by the kinetic spray process

The kinetic spray coating process involves impingement of a substrate by particles of various material types at high velocities. In the process, particles are injected into a supersonic gas stream and accelerated to high velocities. A coating forms when the particles become plastically deformed and bond to the substrate and to one another upon collision with the substrate. Coating formation by the kinetic spray process can be affected by a number of process parameters. In the current study, several spray variables were investigated through computational modeling and experiments. The examined variables include the temperature and pressure of the primary gas, the cross-sectional area of the nozzle throat, the nozzle standoff distance from a substrate, and the surface condition of nozzle interior and the powder gas flow. Experimental verification on the effects of these variables was performed primarily using relatively large-size aluminum particles (63–90 µm) as the feedstock material. It was observed that the coating formation is largely controlled by two fundamental variables of the sprayed particles: particle velocity and particle temperature. The effects of different spray conditions on coating formation by the kinetic spray process can be generally interpreted through their influences on particle velocity and/or particle temperature. Though it is limited to accelerate large particles to high velocities using compressed air or nitrogen as carrier gas, increasing particle temperature provides an additional means that can effectively enhance coating formation by the kinetic spray process.

Ultrasonic Air Temperature Sensing for Automatic Climate Control - Vehicle Test

An ultrasonic air temperature sensor, intended to help improve automatic climate control (ACC), has been demonstrated in a vehicle. Ideally, ACC should be based on inputs correlated with thermal comfort. Current ACC systems do not measure the air temperature best correlated to thermal comfort — at breath level in front of an occupant. This limits the thermal comfort that ACC can provide under transient conditions. An ultrasonic sensor measures the bulk air temperature, is transparent to the driver, and can use commercially available components. In a proof-ofconcept test, we monitored the thermal transients in a vehicle during cool-down after a hot soak and also during warm-up after a cold soak. The ultrasonic path was along the roof console. The ultrasonic temperature always agreed to ±1 oC with the air temperature measured by a thermocouple at the midpoint of the ultrasonic path. Compared to breath-level temperature, there was good agreement for the winter test but, for the summer test there was a 5 oC constant shift. Thermocouple data taken at the two locations showed the same effect. The ultrasonic sensor is rapid and precise, and it is a good candidate for improving ACC.

Ultrasonic Air Temperature Sensing for Automatic Climate Control - Sensor Development

Automatic climate control could be improved by measuring air temperature ultrasonically. Thermal comfort correlates better with bulk air temperature than with the temperature measured by the in-car sensor. The time of flight of an ultrasonic pulse through the air gives the bulk air temperature. In a proof-of-concept experiment, it is accurate to ′ 0.5 °C from -40 to +60 °C. Two operational modes are demonstrated: pulse-echo in which a single transducer creates a pulse and detects its return from a reflector, and single-pass in which a source transducer creates a pulse that travels directly to a separate transducer.

Experimental Evaluation of Reformate-Assisted Diesel NOx Trap Desulfation

NO, adsorber catalysts are leading candidates for improving NO, aftertreatment in diesel exhaust. The major challenge in the use of adsorbers that capture NO, in the form of nitrates is their susceptibility to sulfur poisoning. Sulfur, which is present in diesel fuel, adsorbs and accumulates as sulfate (SO -2 4 ) at the same adsorption sites as NO,, and, since it is more stable than nitrates, inhibits the ability of the catalyst to adsorb NO,. It is found that high temperature (> about 650 °C) in the presence of a reducing gas is required to release sulfur rapidly from the catalyst. Since the peak temperatures of diesel engine exhaust are below 400 °C, additional heat is required to remove the sulfur. This work describes a reformate-assisted sulfur purge method, which employs heat generated inside the NO, trap catalyst by exothermic chemical reactions between the oxygen in diesel exhaust and injected reformate (H 2 + CO). Our results with a laboratory gas bench system show that catalyst desulfation is successful following a desulfation schedule with an inlet gas temperature of about 300 °C. In addition, we have examined impact of temperature, duration of exposure, and reformate-based gas compositions employed for rich-gas desulfation on NO, adsorber efficiency.