A theoretical study based on the Penalty factor(PF)method by Cavallini et al.is conducted to show that the pressure drop occurring in a wire-on-tube heat exchanger can be converted into a temperature difference for tw...A theoretical study based on the Penalty factor(PF)method by Cavallini et al.is conducted to show that the pressure drop occurring in a wire-on-tube heat exchanger can be converted into a temperature difference for two types of refrigerants R-134a and R-600a typically used for charging refrigerators and freezers.The following conditions are considered:stratified or stratified-wavyflow condensation occurring inside the smooth tube of a wire-on-tube condenser with diameter 3.25,4.83,and 6.299 mm,condensation temperatures 35℃,45℃,and 54.4℃ and cover refrigerant massflow rate spanning the interval from 1 to 7 kg/hr.The results show that the PF variation is not linear with vapor quality and attains a maximum when the vapor quality is 0.2 and 0.18 for the R-134a and R-600a refrigerants,respectively.The PF increases with the refrigerant massflow rate if the inner diameter and saturation temperature constant,and it decreases on increasing the inner diameter to 6.299 mm for constant refrigerant massflow rate and saturation temperature.The PF for R-600a is higher than that for R-134a due to the lower saturation pressure in thefirst case.Furthermore,a stratifiedflow produces higher PF in comparison to the annularflow due to the effect of the surface tension.展开更多
The surface tension of molten tin was determined by a set of self-developed digital equipment with sessile drop method at oxygen partial pressure of 1.0×10 -6MPa under different temperatures, and the dependence...The surface tension of molten tin was determined by a set of self-developed digital equipment with sessile drop method at oxygen partial pressure of 1.0×10 -6MPa under different temperatures, and the dependence of surface tension of molten tin on temperature was also discussed. The emphasis was placed on the comparison of surface tension of the same molten tin sample measured by using different equipments with sessile drop method. Results of the comparison indicate that the measurement results with sessile drop method under the approximate experimental conditions are coincident, and the self-developed digital equipment for surface tension measurement has higher stability and accuracy. The relationships of surface tension of molten tin and its temperature coefficient with temperature and oxygen partial pressure were also elucidated from the thermodynamic equilibrium analysis.展开更多
In order to ensure the safety of the non-heating gathering and transportation processes for high water fraction crude oil,the effect of temperature,water fraction,and flow rate on the flow characteristics of crude oil...In order to ensure the safety of the non-heating gathering and transportation processes for high water fraction crude oil,the effect of temperature,water fraction,and flow rate on the flow characteristics of crude oil with high water fraction was studied in a flow experimental system of the X Oilfield.Four distinct flow patterns were identified by the photographic and local sampling techniques.Especially,three new flow patterns were found to occur below the pour point of crude oil,including EW/O&W stratified flow with gel deposition,EW/O&W intermittent flow with gel deposition,and water single-phase flow with gel deposition.Moreover,two characteristic temperatures,at which the change rate of pressure drop had changed obviously,were found during the change of pressure drop.The characteristic temperature of the first congestion of gel deposition in the pipeline was determined to be the safe temperature for the non-heating gathering and transportation of high water cut crude oil,while the pressure drop reached the peak at this temperature.An empirical formula for the safe temperature was established for oil-water flow with high water fraction/low fluid production rate.The results can serve as a guide for the safe operation of the non-heating gathering and transportation of crude oil in high water fraction oilfields.展开更多
In this work an experimental investigation was carried out in order to explore the possibility of realizing a domestic heating system by throttling hydraulic oil. Considering the continuous increasing price of diesel ...In this work an experimental investigation was carried out in order to explore the possibility of realizing a domestic heating system by throttling hydraulic oil. Considering the continuous increasing price of diesel oil, this work gains unique importance. Generating heat directly by throttling is realized using a simple environment friendly system which does not require oil transportation and storage, and eliminates the need for chimneys and annual preventive maintenance, as it is the case with heating by utilizing oil burners, which is prevailing in Jordan. Experimental results show that it is possible to raise the room temperature up to 70?C during 15 minutes which is not a limit value. Experimental results show that temperature rate could be increased by selecting the appropriate pump power and by connecting a number of throttles in parallel.展开更多
文摘A theoretical study based on the Penalty factor(PF)method by Cavallini et al.is conducted to show that the pressure drop occurring in a wire-on-tube heat exchanger can be converted into a temperature difference for two types of refrigerants R-134a and R-600a typically used for charging refrigerators and freezers.The following conditions are considered:stratified or stratified-wavyflow condensation occurring inside the smooth tube of a wire-on-tube condenser with diameter 3.25,4.83,and 6.299 mm,condensation temperatures 35℃,45℃,and 54.4℃ and cover refrigerant massflow rate spanning the interval from 1 to 7 kg/hr.The results show that the PF variation is not linear with vapor quality and attains a maximum when the vapor quality is 0.2 and 0.18 for the R-134a and R-600a refrigerants,respectively.The PF increases with the refrigerant massflow rate if the inner diameter and saturation temperature constant,and it decreases on increasing the inner diameter to 6.299 mm for constant refrigerant massflow rate and saturation temperature.The PF for R-600a is higher than that for R-134a due to the lower saturation pressure in thefirst case.Furthermore,a stratifiedflow produces higher PF in comparison to the annularflow due to the effect of the surface tension.
文摘The surface tension of molten tin was determined by a set of self-developed digital equipment with sessile drop method at oxygen partial pressure of 1.0×10 -6MPa under different temperatures, and the dependence of surface tension of molten tin on temperature was also discussed. The emphasis was placed on the comparison of surface tension of the same molten tin sample measured by using different equipments with sessile drop method. Results of the comparison indicate that the measurement results with sessile drop method under the approximate experimental conditions are coincident, and the self-developed digital equipment for surface tension measurement has higher stability and accuracy. The relationships of surface tension of molten tin and its temperature coefficient with temperature and oxygen partial pressure were also elucidated from the thermodynamic equilibrium analysis.
基金financially supported by the National Natural Science Foundation of China (Grant No.51674281)the Opening Fund of Shandong Provincial Key Laboratory of Oil&Gas Storage (Study on low temperature flow characteristics of oil and water in gathering pipeline)the Transportation Safety and the Fundamental Research Funds for the Central Universities
文摘In order to ensure the safety of the non-heating gathering and transportation processes for high water fraction crude oil,the effect of temperature,water fraction,and flow rate on the flow characteristics of crude oil with high water fraction was studied in a flow experimental system of the X Oilfield.Four distinct flow patterns were identified by the photographic and local sampling techniques.Especially,three new flow patterns were found to occur below the pour point of crude oil,including EW/O&W stratified flow with gel deposition,EW/O&W intermittent flow with gel deposition,and water single-phase flow with gel deposition.Moreover,two characteristic temperatures,at which the change rate of pressure drop had changed obviously,were found during the change of pressure drop.The characteristic temperature of the first congestion of gel deposition in the pipeline was determined to be the safe temperature for the non-heating gathering and transportation of high water cut crude oil,while the pressure drop reached the peak at this temperature.An empirical formula for the safe temperature was established for oil-water flow with high water fraction/low fluid production rate.The results can serve as a guide for the safe operation of the non-heating gathering and transportation of crude oil in high water fraction oilfields.
文摘In this work an experimental investigation was carried out in order to explore the possibility of realizing a domestic heating system by throttling hydraulic oil. Considering the continuous increasing price of diesel oil, this work gains unique importance. Generating heat directly by throttling is realized using a simple environment friendly system which does not require oil transportation and storage, and eliminates the need for chimneys and annual preventive maintenance, as it is the case with heating by utilizing oil burners, which is prevailing in Jordan. Experimental results show that it is possible to raise the room temperature up to 70?C during 15 minutes which is not a limit value. Experimental results show that temperature rate could be increased by selecting the appropriate pump power and by connecting a number of throttles in parallel.
