IMPACT OF OIL ON FLOW BOILING OF AMMONIA AND OF R723 IN SMOOTH HORIZONTAL TUBES
The average flow boiling heat transfer coefficients during the evaporation of the natural refrigerant ammonia (R717) and of the azeotropic mixture “ammonia/dimethylether (R723) are summarized, thus including the impact of a frequently-used fully-synthetic oil (PAO ISO-VG 68).Tests were run in a 24 m long serpentine type evaporator equipped with smooth horizontal tube sections of 14 mm inner diameter connected by U-bends. The flow boiling of both refrigerants was studied at evaporation temperatures from -10 to +10℃, with mass velocities ranging from 40 to 260 kg/(m2 s), while average heat fluxes varied between 10 and 60 kW/m2.Small quantities of PAO-oil, which is immiscible with ammonia and miscible with R723 under the test conditions, cause a considerable reduction of the boiling heat transfer coefficient mainly in the regions with annular two-phase flow regime. This paper gives an overview of the present applied research work.
Tahsin BOYMAN
Lucerne School of Engineering and Architecture (HTA Luzern) Lucerne University of Applied Sciences and Arts (FHZ) Technikumstrasse 21, CH - 6048 Horw, Switzerland
国际会议
The 22nd International Congress of Refrigeration(第22届国际制冷大会)
北京
英文
2007-08-21（万方平台首次上网日期，不代表论文的发表时间）