Experimental Measurement and Modeling of Oil Holdup

Often in air conditioning and refrigeration vapor compression systems the working fluid is mixed with lubricating oil, which flows through the system as it operates. The effects of this oil in the system include the possible degradation of heat transfer, increased pressure drop, insufficient lubrication for the compressor and the possibility of flooding the compressor suction ports with oil should the compressor valve fail. In order to quantitatively evaluate these effects on the system, a better understanding of the flow of oil through various operating conditions is required. The purpose of this investigation is the measurement of oil retention in small diameter round copper tubes with various internal geometries. Test sections include an internally smooth, an axially microfinned and a helically microfinned tube, all with an outer diameter of 9.53 mm (3/8???). Mass fluxes of 75 to 300 kg/m2s are tested, with an emphasis on 75 and 150 kg/m2s, and qualities of 0% to 100% are reached. The refrigerant/oil mixtures examined include R134a with a polyol ester, R134a with a polyalkylene glycol, R134a with an alkylbenzene, R22 with an alkylbenzene and R410A with a polyol ester. Additionally, it is important to examine the void fraction and flow visualization of the mixtures to determine if the oil has an effect in these areas. Finally, two models have been developed for oil holdup prediction. The first is based on the test section???s liquid volume fraction and is used at mid to low-range qualities, while the second, with the Blasius turbulent flow formula as a basis, is used to predict holdup at high qualities.Air Conditioning and Refrigeration Project 15

Visitor satisfaction analysis as a tool for park managers: a review and case study

Visitor satisfaction has been an important area for leisure research since the 1960s and more recently for park management. A number of approaches have been adapted from consumer research including importance-performance analyses, gap analyses, threshold performance targets and overall satisfaction. This paper reviews these approaches with respect to park management. It then draws on focus group research with protected area agency staff to obtain their views on the usefulness and robustness of the analyses associated with these approaches. Yanchep National Park (Western Australia) was used as a case study, with the results from a recent visitor survey providing the data for satisfaction analyses. To provide a more accurate summary of the range in results, confidence intervals accompanied the results to illustrate the variation in responses. The analyses emphasize the importance for park managers of accessible, usable data on visitor satisfaction