réalité post-adoption des parents ayant réalisé une adoption internationale d'enfants plus âgés /

Abstract

Tpropert ies of refrigerants, arranged for the occasional user. The refrigerants have a thermodynamic property chart on pressure-enthalpy coordinates with an abbreviated set of tabular data for sat-urated liquid and vapor on the facing page. In addition, tabular data in the superheated vapor region are given for R-134a to assist stu-dents working on compression cycle examples. For each cryogenic fluid, a second table of properties is pro-vided for vapor at a pressure of one standard atmosphere; these data are needed when such gases are used in heat transfer or purge gas applications. For zeotropic blends, including R-729 (air), tables are incremented in pressure, with properties given for liquid on the bubble line and vapor on the dew line. This arrangement is used because pressure is more commonly measured in the field while servicing equipment; it also highlights the difference between bub-ble and dew-point temperatures (the " temperature glide " experi-enced with blends). Most CFC refrigerants have been deleted. Tables for R-11, R-13, R-113, R-114, R-141b, R-142b, R-500, R-502, R-503, and R-720 (neon) may be found in the 1997 ASHRAE Handbook—Fundamen-tals. R-12 has been retained to assist in making comparisons. Re-vised formulations have been used for many refrigerants; these conform to international standards, where applicable. Thermody-namic properties of R-12, R-22, R-32, R-123, R-125, R-134a, R-143a, R-152a, R-717 (ammonia), and R-744 (carbon dioxide) and refrigerant blends R-404A, R-407C, R-410A, and R-507 conform to ISO/DIS Draft Standard 17584, Refrigerant Properties. Reference states used for most refrigerants correspond to the inter-national convention of 200 kJ/kg for enthalpy and 1 kJ/(kg·K) for entropy, both for saturated liquid at 0°C. Exceptions are water and fluids with very low critical temperatures (e.g., ethylene, cryogens). These data are intended to help engineers make preliminary comparisons among unfamiliar fluids. For greater detail and a wider range of data, see the sources in the References.