研发了一种适用于数据中心等电子设备全天候环境控制的新型高效制冷机组HKF-60FH,其集成蒸气压缩制冷系统、分离式热管系统于一体,具有压缩制冷、复合制冷和热管制冷三种工作模式。压缩制冷单元由4台涡旋式压缩机两两并联构成2个独立的...研发了一种适用于数据中心等电子设备全天候环境控制的新型高效制冷机组HKF-60FH,其集成蒸气压缩制冷系统、分离式热管系统于一体,具有压缩制冷、复合制冷和热管制冷三种工作模式。压缩制冷单元由4台涡旋式压缩机两两并联构成2个独立的制冷回路,通过变容量控制实现制冷量调节;热管单元使用第二制冷剂,由液泵驱动强制循环;风冷侧采用组合式换热器,其由热管单元的换热器、压缩制冷单元的冷凝器和风机构成。高温季节运行压缩制冷模式,压缩制冷系统的第一制冷剂通过冷凝蒸发器为第二制冷剂提供全部冷量;过渡季节运行复合制冷模式,热管单元满负荷工作,不足冷量由压缩制冷单元提供;低温季节运行热管模式,全部使用自然冷源。HKF-60FH配套应用于某高性能计算机的空调系统,蒸发器设置在服务器桁架内,采用水平送风、闭式循环的气流组织方式,回风温度设定为33℃。性能测试显示:制冷工况(环境温度35℃)和热管工况(环境温度10℃)的制冷量/COP分别为61.3 k W/3.23和59.8 k W/11.3。展开更多
Characteristics of R22 and its new alternative refrigerant R200 flowing through adiabatic capillary tubes are investigated based on the homogeneous model. Extensive flow variables along tube length such as pressure, t...Characteristics of R22 and its new alternative refrigerant R200 flowing through adiabatic capillary tubes are investigated based on the homogeneous model. Extensive flow variables along tube length such as pressure, temperature, viscosity, velocity. Reynolds number, friction factor and vapor quality etc are compared between the two fluids under the same operating condition. Two cases are considered, namely, either the same tube length or the same mass flow rate as inlet condition. The results show that the mass flow rate in the capillary tube of R290 is 40% lower than that of R22 due to the differences of physical properties between the two fluids. Further. a parametric analysis is performed and it appears that effects of geometric and thermodynamic parameters on mass flow rate of R290 are weaker than that of R22. When the condensing temperature is increased from 40℃ to 50℃ C. the mass flow rate for R22 is increased by 16%. while the increasing rate for R290 is 13%.展开更多
Using near-azeotropic refrigerant R410A as the working fluid, the experimental studies on the horizontal micro-fin tubes were conducted. Several factors affecting heat transfer coefficients were analyzed, and the char...Using near-azeotropic refrigerant R410A as the working fluid, the experimental studies on the horizontal micro-fin tubes were conducted. Several factors affecting heat transfer coefficients were analyzed, and the characteristics of flow boiling of the refrigerant in the horizontal micro-fin tubes were discussed. The local heat transfer coefficients increase with mass flux, heat flux and quality. And the heat transfer enhancement factor of those testing tubes is about 1.6 to 2.2.展开更多
A heat exchanger that arranges flat tubes horizontally has a vertical header that distributes the refrigerant to each tube. When the heat exchanger works as an evaporator, differences in flow conditions at each branch...A heat exchanger that arranges flat tubes horizontally has a vertical header that distributes the refrigerant to each tube. When the heat exchanger works as an evaporator, differences in flow conditions at each branch, such as the ratio and distribution of vapor and liquid, due to the differences in densities and momentums of vapor and liquid in the two-phase flow make equal distribution difficult. This paper describes the distribution characteristics of a four-branch header that has a rectangular cross-section without the internal protrusion of flat tubes in the case of the inflow of the refrigerant R32 from the bottom of the header by using an equipment that can estimate the distribution ratio of the liquid and vapor phase to each branch. This paper also discusses the distribution characteristics on the basis of the flow visualization in the header. The flow visualization shows that a liquid level that contains vapor phase exists in the header and affects the distribution greatly.展开更多
The effects of different refrigerants on heat transfer performance of pulsating heat pipe(PHP) are investigated experimentally.The working temperature of pulsating heat pipe is kept in the range of 20℃-50℃.The start...The effects of different refrigerants on heat transfer performance of pulsating heat pipe(PHP) are investigated experimentally.The working temperature of pulsating heat pipe is kept in the range of 20℃-50℃.The startup time of the pulsating heat pipe with refrigerants can be shorter than 4 min,when heating power is in the range of 10W-100W.The startup time decreases with heating power.Thermal resistances of PHP with filling ratio 20.55% were obviously larger than those with other filling ratios.Thermal resistance of the PHP with R134a is much smaller than that with R404A and R600a.It indicates that the heat transfer ability of R134a is better.In addition,a correlation to predict thermal resistance of PHP with refrigerants was suggested.展开更多
Falling film generation process in lithium bromide absorption refrigeration generation system is researched in thispaper. To describe the coupled heat and mass transfer of laminar falling film in vertical generation t...Falling film generation process in lithium bromide absorption refrigeration generation system is researched in thispaper. To describe the coupled heat and mass transfer of laminar falling film in vertical generation tube, a mathematicalmodel is developed, in which the effect of mass transfer on heat transfer is carefully evaluated. Moreover,an equation related Re number with solution volume flow was also obtained in given conditions. We carried outthe experiments with the mass fraction of the inlet solution LiBr being 49.5% and obtained an empirical correlationof heat transfer with the film Re number and heat flux in different volume flow. Specifically, when 5kW/m2<qw<25kW/m2 and Re<500 the heat transfer correlation is given as: h=14009.87qw0.0764Re-0.5391.展开更多
Forced convective heat transfer in micro-rectangular channels can be described by a group of twodimensional differential equations. These equations take the conduction in microchannel wb along the direction of flow of...Forced convective heat transfer in micro-rectangular channels can be described by a group of twodimensional differential equations. These equations take the conduction in microchannel wb along the direction of flow of coolants into account, which are more generalized than those which neglect the conduction. For the same reason, they are suitable particularly for gases-cooled microchannels.With only numerical solution to the equations till today, an approximate analytic solution is derived here. From this solution, a rather simple formula can be introduced bober, by which the differences between considering the conduction and neglecting it are easily found. In addition, the rcasonableness of the classical fin method is also discussed. An experimental example of air-cooled microchannels is illustrated.展开更多
文摘研发了一种适用于数据中心等电子设备全天候环境控制的新型高效制冷机组HKF-60FH,其集成蒸气压缩制冷系统、分离式热管系统于一体,具有压缩制冷、复合制冷和热管制冷三种工作模式。压缩制冷单元由4台涡旋式压缩机两两并联构成2个独立的制冷回路,通过变容量控制实现制冷量调节;热管单元使用第二制冷剂,由液泵驱动强制循环;风冷侧采用组合式换热器,其由热管单元的换热器、压缩制冷单元的冷凝器和风机构成。高温季节运行压缩制冷模式,压缩制冷系统的第一制冷剂通过冷凝蒸发器为第二制冷剂提供全部冷量;过渡季节运行复合制冷模式,热管单元满负荷工作,不足冷量由压缩制冷单元提供;低温季节运行热管模式,全部使用自然冷源。HKF-60FH配套应用于某高性能计算机的空调系统,蒸发器设置在服务器桁架内,采用水平送风、闭式循环的气流组织方式,回风温度设定为33℃。性能测试显示:制冷工况(环境温度35℃)和热管工况(环境温度10℃)的制冷量/COP分别为61.3 k W/3.23和59.8 k W/11.3。
基金Supported by the Fund of"985 Project"of Tianjin University (TD2001011).
文摘Characteristics of R22 and its new alternative refrigerant R200 flowing through adiabatic capillary tubes are investigated based on the homogeneous model. Extensive flow variables along tube length such as pressure, temperature, viscosity, velocity. Reynolds number, friction factor and vapor quality etc are compared between the two fluids under the same operating condition. Two cases are considered, namely, either the same tube length or the same mass flow rate as inlet condition. The results show that the mass flow rate in the capillary tube of R290 is 40% lower than that of R22 due to the differences of physical properties between the two fluids. Further. a parametric analysis is performed and it appears that effects of geometric and thermodynamic parameters on mass flow rate of R290 are weaker than that of R22. When the condensing temperature is increased from 40℃ to 50℃ C. the mass flow rate for R22 is increased by 16%. while the increasing rate for R290 is 13%.
基金Shanghai Leading Academic Discipline Project(No.T0503)
文摘Using near-azeotropic refrigerant R410A as the working fluid, the experimental studies on the horizontal micro-fin tubes were conducted. Several factors affecting heat transfer coefficients were analyzed, and the characteristics of flow boiling of the refrigerant in the horizontal micro-fin tubes were discussed. The local heat transfer coefficients increase with mass flux, heat flux and quality. And the heat transfer enhancement factor of those testing tubes is about 1.6 to 2.2.
文摘A heat exchanger that arranges flat tubes horizontally has a vertical header that distributes the refrigerant to each tube. When the heat exchanger works as an evaporator, differences in flow conditions at each branch, such as the ratio and distribution of vapor and liquid, due to the differences in densities and momentums of vapor and liquid in the two-phase flow make equal distribution difficult. This paper describes the distribution characteristics of a four-branch header that has a rectangular cross-section without the internal protrusion of flat tubes in the case of the inflow of the refrigerant R32 from the bottom of the header by using an equipment that can estimate the distribution ratio of the liquid and vapor phase to each branch. This paper also discusses the distribution characteristics on the basis of the flow visualization in the header. The flow visualization shows that a liquid level that contains vapor phase exists in the header and affects the distribution greatly.
基金supported by National Natural Science Foundation of China(No.51376019)
文摘The effects of different refrigerants on heat transfer performance of pulsating heat pipe(PHP) are investigated experimentally.The working temperature of pulsating heat pipe is kept in the range of 20℃-50℃.The startup time of the pulsating heat pipe with refrigerants can be shorter than 4 min,when heating power is in the range of 10W-100W.The startup time decreases with heating power.Thermal resistances of PHP with filling ratio 20.55% were obviously larger than those with other filling ratios.Thermal resistance of the PHP with R134a is much smaller than that with R404A and R600a.It indicates that the heat transfer ability of R134a is better.In addition,a correlation to predict thermal resistance of PHP with refrigerants was suggested.
文摘Falling film generation process in lithium bromide absorption refrigeration generation system is researched in thispaper. To describe the coupled heat and mass transfer of laminar falling film in vertical generation tube, a mathematicalmodel is developed, in which the effect of mass transfer on heat transfer is carefully evaluated. Moreover,an equation related Re number with solution volume flow was also obtained in given conditions. We carried outthe experiments with the mass fraction of the inlet solution LiBr being 49.5% and obtained an empirical correlationof heat transfer with the film Re number and heat flux in different volume flow. Specifically, when 5kW/m2<qw<25kW/m2 and Re<500 the heat transfer correlation is given as: h=14009.87qw0.0764Re-0.5391.
文摘Forced convective heat transfer in micro-rectangular channels can be described by a group of twodimensional differential equations. These equations take the conduction in microchannel wb along the direction of flow of coolants into account, which are more generalized than those which neglect the conduction. For the same reason, they are suitable particularly for gases-cooled microchannels.With only numerical solution to the equations till today, an approximate analytic solution is derived here. From this solution, a rather simple formula can be introduced bober, by which the differences between considering the conduction and neglecting it are easily found. In addition, the rcasonableness of the classical fin method is also discussed. An experimental example of air-cooled microchannels is illustrated.
