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Refrigeration Lubricants
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
Mark R. Baker, Michael G. Foster
This sector covers lubricants used in automotive air-conditioning compressors. This market traditionally used R-12 as a refrigerant. In developed markets, the transition to HFCs has been completed. 2011 saw the introduction of a low GWP refrigerant into the market called R-1234yf. This initiative was driven by a European to use low GDP refrigerants. POE and PAG lubricants are compatible with this new technology. Double end-capped PAGs are especially preferred due to their excellent stability and the fact that they are currently used for R-134a systems (hence minimum changeover issues). Some modification in additive packages and manufacturing specifications of the double and capped PAGs are required to compensate for the lower stability of R-1234yf when compared with R-134a. EV and hybrid systems prefer higher flash point POE lubricants due to flammability concern with lubricant leaks.
Internal Convective Condensation
Published in Van P. Carey, Liquid-Vapor Phase-Change Phenomena, 2018
Note that for a given saturation pressure, the properties of the saturated liquid and vapor in Eqs. (11.71) and (11.72) are specified. Thus, this crude annular flow model indicates that for a given fluid at a specified quality and saturation pressure, the film thickness decreases and the heat transfer coefficient increases as the tube diameter is reduced. These general trends are, in fact, observed in the performance of highperformance compact condensers used in automotive air-conditioning applications. Early condenser designs for this type of application typically used round tubes with inside diameters of about 10 mm. More modern designs use flow passages with much smaller hydraulic diameters. The flow passages in an automotive condenser design developed by Modine Manufacturing Company [11.20] is an example of this strategy. The cross section of this passage is shown schematically in Fig. 11.10. The patent for this design specifies optimal mean hydraulic diameters for the passage in the range of 380 to 1000 μm.
Applications
Published in Raj P. Chhabra, CRC Handbook of Thermal Engineering Second Edition, 2017
Joshua D. Ramsey, Ken Bell, Ramesh K. Shah, Bengt Sundén, Zan Wu, Clement Kleinstreuer, Zelin Xu, D. Ian Wilson, Graham T. Polley, John A. Pearce, Kenneth R. Diller, Jonathan W. Valvano, David W. Yarbrough, Moncef Krarti, John Zhai, Jan Kośny, Christian K. Bach, Ian H. Bell, Craig R. Bradshaw, Eckhard A. Groll, Abhinav Krishna, Orkan Kurtulus, Margaret M. Mathison, Bryce Shaffer, Bin Yang, Xinye Zhang, Davide Ziviani, Robert F. Boehm, Anthony F. Mills, Santanu Bandyopadhyay, Shankar Narasimhan, Donald L. Fenton, Raj M. Manglik, Sameer Khandekar, Mario F. Trujillo, Rolf D. Reitz, Milind A. Jog, Prabhat Kumar, K.P. Sandeep, Sanjiv Sinha, Krishna Valavala, Jun Ma, Pradeep Lall, Harold R. Jacobs, Mangesh Chaudhari, Amit Agrawal, Robert J. Moffat, Tadhg O’Donovan, Jungho Kim, S.A. Sherif, Alan T. McDonald, Arturo Pacheco-Vega, Gerardo Diaz, Mihir Sen, K.T. Yang, Martine Rueff, Evelyne Mauret, Pawel Wawrzyniak, Ireneusz Zbicinski, Mariia Sobulska, P.S. Ghoshdastidar, Naveen Tiwari, Rajappa Tadepalli, Raj Ganesh S. Pala, Desh Bandhu Singh, G. N. Tiwari
The rotating vane rotary compressor, shown in Figure 4.11.11, has a rotor with slots that contain several vanes. The vanes slide in and out of the rotor and are centrifugally pressed against the cylinder wall as the assembly rotates. The shaft center is eccentric from the center of the cylinder; therefore, the gas volumes in the pockets between the rotor, vanes, and cylinder vary as the unit rotates. Suction gas enters through a suction port. Discharge gas flow is commonly controlled with a discharge valve. The rotating vane compressor is subject to wear at several sealing surfaces, but is somewhat self-compensating for the wear. It can be more tolerant to contamination than the rolling piston compressor. This type of compressor has cooling capacities ranging from 12,000 to 120,000 Btu/h (3.5–35 kW). It is used primarily in automotive air conditioning applications.
Optimal design of cyclic-stress accelerated life tests for lognormal lifetime distribution
Published in Quality Technology & Quantitative Management, 2023
An automotive air-conditioning system is a closed loop system that involves cycles of compression, condensation, expansion and evaporation of the refrigerant. It systematically controls heating and cooling, thereby maintaining a constant temperature inside a vehicle. The major components of the system incorporate a compressor, condenser, expansion valve, and evaporator. Among them, the evaporator, serving as the heat absorption component, converts the low-pressure and low-temperature liquid refrigerant into vapor through thermal exchanges with the ambient air. The evaporator also acts as a dehumidifier. The moisture contained in the air condenses on their surface and is drained off in that the fins or tubes of the evaporator are usually colder than the ambient air. During the dehumidifying process, the water on the surface can freeze and block off the air when the surface temperature is below 0°C, which leads to performance reduction of the air-conditioning system. In order to provide efficient transfer of heat at the evaporator while preventing it from freezing, the evaporator temperature is detected by the thermistor. It switches the compressor on and off periodically, which results in a repeated, cyclic, hydraulic pressure of the refrigerant to the evaporator. This can cause cracks in fins or tubes of the evaporator and induce leakage.