Seal Mechanism of Tip Seal in Scroll Compressor

Scroll compressors are widely used in room air conditioning cycles, package air conditioning cycles, refrigeration, water heater and automobile air conditioning cycles as well as air compressors, helium compressors and vacuum pump. There are two main leakage paths in a compression chamber formed by a fixed scroll and an orbiting scroll. One is the leakage path through a radial clearance between the wraps of fixed and orbiting scroll. The leakage through the radial clearance is prevented by pressing the orbiting scroll radially against the fixed scroll by a mechanism such as a compliance mechanism. Oil inside the compression chamber also has the sealing effect and reduces the leakage through the radial clearance. Another leakage path is an axial clearance which is the clearance between a tip of the scroll wrap and a base plate. A tip seal is often used to prevent the leakage through the axial clearance. Although there have been many studies on the tip seal, the seal mechanism of the tip seal is not thoroughly clarified yet, and the influence of design parameters on efficiency of the tip seal is unclear. In addition, the relationship between the sealing effect and a frictional loss of the tip seal is also not validated well. In this study, a test apparatus which can evaluate the sealing effect and the frictional loss of the tip seal simultaneously is developed. The influence of several design parameters on the sealing effect and the frictional loss is examined with the test apparatus. By measuring pressure distribution around the tip seal in a tip seal groove, the sealing mechanism of the tip seal is clarified and a design guideline of the tip seal groove is obtained

Comparison of sulfur isotope ratio measurements by various techniques, and the δ(34)S values of some sulur standards

Three techniques (combustion of Ag(2)S by Cu(2)O, thermal decomposition of BaSO(4) and KIBA reagent method under vacuum) for sulfur isotope ratio measurements of geological samples are described in detail. The δ(34)S values of three working standards (MSS-2, MSS-3 and MSS-4) obtained by these techniques for the last 13 years were compared (Table 1 and Fig. 3): the most acceptable values of the three standards are +21.5, +3.5 and +4.5‰, respectively

H and K Band Methane Features in an L Dwarf, 2MASS 0920+35

We have obtained near-infrared spectra of three L dwarfs discovered by 2MASS, 1506+13 (L3), 1507-16 (L5), and 0920+35 (L6.5). From the comparison of the H and K band spectra of these L dwarfs, we have found the presence of methane absorption in 0920+35. This implies that detectable methane absorption in the H and K bands, usually considered the signature of a T dwarf, can be present in objects classified optically as late L. Methane detection in L dwarfs is consistent with the presence of a dust layer deep in the atmosphere as the unified model of Tsuji suggests.Comment: Accepted for publication in ApJ Letters; 8 pages, 4 figure

Spectral Classification and Effective Temperatures of L and T Dwarfs Based of Near-Infrared Spectra

We have obtained near-infrared spectra of L dwarfs, L/T transition objects and T dwarfs using Subaru. Resulting spectra are examined in detail to see their dependence on the spectral types. We have obtained bolometric luminosities of the objects with known parallaxes in our sample, first by integrating the spectra and second by K band bolometric correction. We derive the relation between effective temperature and spectral type.Comment: To appear in May 20, 2004 issue of ApJ There is a companion paper by Tsuji, Nakajima and Yanagisaw

Dust in the Photospheric Environment II. Effect on the Near Infrared Spectra of L and T Dwarfs

We report an attempt to interpret the spectra of L and T dwarfs with the use of the Unified Cloudy Model (UCM). For this purpose, we extend the grid of the UCMs to the cases of log g = 4.5 and 5.5. The dust column density relative to the gas column density in the observable photosphere is larger at the higher gravities, and molecular line intensity is generally smaller at the higher gravities. The overall spectral energy distributions (SEDs) are f_{J} < f_{H} < f_{K} in middle and late L dwarfs, f_{J} f_{K} in early T dwarfs (L/T transition objects), and finally f_{J} > f_{H} > f_{K} in middle and late T dwarfs, where f_{J}, f_{H}, and f_{K} are the peak fluxes at J, H, and K bands, respectively, in f_{nu} unit. This tendency is the opposite to what is expected for the temperature effect, but can be accounted for as the effect of thin dust clouds formed deep in the photosphere together with the effect of the gaseous opacities including H_2 (CIA), H_2O, CH_4, and K I. Although the UCMs are semi-empirical models based on a simple assumption that thin dust clouds form in the region of T_{cr} < T < T_{cond} (T_{cr} = 1800K is an only empirical parameter while T_{cond} about 2000K is fixed by the thermodynamical data), the major observations including the overall SEDs as well as the strengths of the major spectral features are consistently accounted for throughout L and T dwarfs. In view of the formidable complexities of the cloud formation, we hope that our UCM can be of some use as a guide for future modelings of the ultracool dwarfs as well as for interpretation of observed data of L and T dwarfs.Comment: 43 pages, 13 figures, to appear in Astrophys. J. (May 20, 2004) Some minor corrections including the address of our web site, which is now read

Evaluation of Wettability of Solid Surface with Oil/Refrigerant Mixture

A part of lubrication oil stored in an oil sump of a refrigeration compressor becomes fine oil mist in a compressor shell. Although some of the oil mist is separated from refrigerant in the compressor shell, a certain amount of the oil mist is discharged with refrigerant into a refrigeration cycle. The oil circulated with refrigerant in the cycle degrades the heat transfer efficiency of heat exchangers, increases pressure drop in lines and the heat exchangers and sometimes reduces reliability of the compressor when an oil return from the cycle to the compressor is insufficient. It is therefore important to reduce the oil discharge from the compressor to the cycle. In order to decrease the oil amount discharged from the compressor, development of a superior oil separator should be done and many researches were focused on it. More basically, since the separation efficiency of the oil separator strongly depends on droplet size of the oil mist, factors associated with the droplet size such as generation mechanism of the oil mist in the compressor, the droplet behavior on solid surface in the compressor and surface tension of the oil in which the refrigerant is dissolved should be clarified. However, the surface tension of the oil mixed with refrigerant and wettability of solid surface with the oil/refrigerant mixture which influences the droplet behavior have not been reported sufficiently. In this study, the surface tension of the PAG oil/CO2 mixture is measured by a pendant drop method and the wettability of the solid surface is evaluated as the fundamental study for discussing the generation mechanism of the oil mist in the compressor. The measurements of the surface tension of the oil/refrigerant mixture and contact angle of the mixture on the solid surface are achieved under high pressure and temperature condition. It is found that the surface tension of oil/refrigerant mixture decreases steeply with increasing the refrigerant concentration in the oil. The contact angle on solid surface decreases with the refrigerant concentration due to the reduction of surface tension. The contact angle on Aluminum surface is smaller than that on the PTFE surface and decreases with elapsed time. With using Ohnesorge number which is a ratio of viscous force to inertia force and surface tension force to evaluate the oil droplet behavior on the metal surface, Ohnesorge number is estimated to be very small under discharge condition in the compressor and it suggest that the oil droplet of oil/refrigerant mixture will spread immediately on the metal surface

Observations of High Energy Cosmic-Ray Electrons from 30 GeV to 3 TeV with Emulsion Chambers

We have performed a series of cosmic-ray electron observations using the balloon-borne emulsion chambers since 1968. While we previously reported the results from subsets of the exposures, the final results of the total exposures up to 2001 are presented here. Our successive experiments have yielded the total exposure of 8.19 m^2 sr day at the altitudes of 4.0 - 9.4 g/cm^2. The performance of the emulsion chambers was examined by accelerator beam tests and Monte-Carlo simulations, and the on-board calibrations were carried out by using the flight data. In this work we present the cosmic-ray electron spectrum in the energy range from 30 GeV to 3 TeV at the top of the atmosphere, which is well represented by a power-law function with an index of -3.28+-0.10. The observed data can be also interpreted in terms of diffusive propagation models. The evidence of cosmic-ray electrons up to 3 TeV suggests the existence of cosmic-ray electron sources at distances within ~1 kpc and times within ~1x10^5 yr ago.Comment: 38 pages, 10 figures, 3 tables, Accepted for publication in Ap

Pervasive social deficits, but normal parturition, in oxytocin receptor-deficient mice

The oxytocin receptor (OXTR) and its ligand, oxytocin (OXT), regulate reproductive physiology (i.e., parturition and lactation) and sociosexual behaviors. To define the essential functions of OXTR, we generated mice with a null mutation in the Oxtr gene (Oxtr-/-) and compared them with OXT-deficient (Oxt-/-) mice. Oxtr-/- mice were viable and had no obvious deficits in fertility or reproductive behavior. Oxtr-/- dams exhibited normal parturition but demonstrated defects in lactation and maternal nurturing. Infant Oxtr-/- males emitted fewer ultrasonic vocalizations than wild-type littermates in response to social isolation. Adult Oxtr-/- males also showed deficits in social discrimination and elevated aggressive behavior. Ligand Oxt-/- males from Oxt-/- dams, but not from Oxt+/- dams, showed similar high levels of aggression. These data suggest a developmental role for the OXT/OXTR system in shaping adult aggressive behavior. Our studies demonstrate that OXTR plays a critical role in regulating several aspects of social behavior and may have important implications for developmental psychiatric disorders characterized by deficits in social behavior