Rheological Properties of TiO2/POE Nanolubricant for Automotive Air-Conditioning System

The enhancement of nanolubricant rheological properties can improve the performance of automotive air-conditioning systems. The rheological properties of the TiO2/POE nanolubricant were investigated in this study at 0.01 to 0.1% volume concentrations and temperatures ranging from 0 to 100°C. TiO2 nanoparticles were dispersed in the base lubricant of Polyol-ester (POE RL68H) lubricant in two steps. The dynamic viscosity was measured with an Anton-Paar Rotational Rheometer. According to the findings, the TiO2/POE nanolubricant behaved as Newtonian fluids at all volume concentrations and temperatures. The dynamic viscosity increment of nanolubricants up to 1.75% only occurred for 0.1% volume concentration and temperature of 90 to 100°C. Meanwhile, when compared to POE lubricant, nanolubricants with volume concentrations of 0.01 and 0.05% showed a decrement trend in dynamic viscosity of up to 1.8%. Finally, the TiO2/POE nanolubricant improved the rheological properties of the POE lubricant for use in automotive air-conditioning systems.

Test and Analysis of Stepper Motor’s Noise in HVAC’s Ventilation Valve

With the application of automotive air conditioning being more popular, higher requirements on automotive air conditioning’s comfort have been put forward, noise is an important criterion about comfort. BDC motor controlling ventilation valve’s noise is mainly caused by brush and commutator, but stepper motor doesn’t have it and stepper motor is cheap and easy-controlling. In this paper, the principle of microstepping drive technology is discussed in detail, the control circuit block diagram and the application of the stepping motor’s control system are introduced. The noise of BDC motor and stepper motor controlling ventilation valve is measured in the semi-anechoic room, BDC motor produces peak noise at the start and stop during the working of motor, stepper motor’s noise is slight and smooth-going; current waveforms have been measured in the microstepping drive, the results show microstepping drive makes current waveform more smooth-going and stepper motor’s noise is lower. So it is a tendance stepper motor will replace BDC motor to control ventilation valve, and the microstepping drive can meet different requirements for merchant’s control.

Performance of flow distribution in a microchannel parallel flow gas cooler with stepped protrusion depth header

Microchannel parallel flow gas cooler is commonly used in transcritical carbon dioxide automotive air conditioning system. To investigate the influence of the flat tube protrusion depth on fluid distribution, a numerical calculation model of microchannel parallel flow gas cooler with D-shaped header is established. With the object of even flow distribution, a novel stepped protrusion depth header is proposed. The effects of new header on the flow distribution of gas cooler were studied by numerical simulation. The results show that the flow distribution performance of gas cooler can be improved by changing the flat tube protrusion depth. Changing the protrusion depth of three groups of flat tubes simultaneously can achieve a better flow distribution performance of gas cooler than changing the protrusion depth of only one or two groups of flat tubes. When compared with the protrusion depth of all flat tubes is 0, the novel stepped protrusion depth header reduces the total flow distribution nonuniformity of gas cooler by 34–51%. The research in this paper provides a method for improving the flow distribution performance of gas coolers.