为解决污水源热泵中换热器防堵和防垢的问题,提出了带引射回流功能的污水旋流防阻机,并进行了砂水和生活污水分离试验。结果表明:该防阻机对砂子(75~250μm)和污杂物(<4 mm)均有较好的分离效果,分离效率分别为98.17%~100%和94.33%~96...为解决污水源热泵中换热器防堵和防垢的问题,提出了带引射回流功能的污水旋流防阻机,并进行了砂水和生活污水分离试验。结果表明:该防阻机对砂子(75~250μm)和污杂物(<4 mm)均有较好的分离效果,分离效率分别为98.17%~100%和94.33%~96.96%。优化的溢流管与圆柱段长度比值的范围大小与离散相密度成正比。并且,引射回流装置的存在不仅实现了防堵和连续排污,还显著减轻了"溢流跑粗"的影响,提高了分离效率。防阻机的能耗基本不随溢流管与圆柱段长度比值的变化而变化,且总的能量损失较小(小于17 k Pa)。在保证较高分离效率的同时,分流比可以控制在较低的水平(小于10%),相比传统污水源热泵中的污水防阻机,可利用污水量大大提高。展开更多
脉动热管是一种结构简单、传热性能突出的新型传热元件,由于运行过程涉及沸腾与冷凝及两相流动,传热及流动机理复杂,因此目前对其运行过程的相关数值模拟尚不成熟。本文采用VOF（volume of fluid）模型,考虑表面张力和壁面接触角的影响...脉动热管是一种结构简单、传热性能突出的新型传热元件,由于运行过程涉及沸腾与冷凝及两相流动,传热及流动机理复杂,因此目前对其运行过程的相关数值模拟尚不成熟。本文采用VOF（volume of fluid）模型,考虑表面张力和壁面接触角的影响,采用数值模拟软件对单环路脉动热管的流动及传热特性进行了研究。数值模拟中,单环路脉动热管的充液率为40%～60%,热端加热功率为10～40W,探讨了热管蒸发段与冷凝段长度比对热管启动及换热性能的影响,并分析了脉动热管运行时流型特征。结果表明：随蒸发段和冷凝段长度比值增大,脉动热管启动时间缩短,且换热性能有一定提高;但在低充液率时,容易出现＂干烧＂现象。在低加热功率时,脉动热管的启动方式为温度突变式;而在高加热功率时,其启动方式为温度渐变式。此外,通过蒸发段的温度振荡特征可以确定脉动热管的启动时间。展开更多
Radial compressive cracking force of two cassava varieties （TMS 30572 and TMS 4（2）1425） was determined. Tubers from plants about 1.5 years old, freshly harvested from the Teaching and Research Farm of Obafemi Awol...Radial compressive cracking force of two cassava varieties （TMS 30572 and TMS 4（2）1425） was determined. Tubers from plants about 1.5 years old, freshly harvested from the Teaching and Research Farm of Obafemi Awolowo University, Ile-Ife, Nigeria, were used for this study. The tubers were cleaned and sliced into different lengths ranging from 25 mm to 150 mm in steps of 25 mm. For each species, slices of a particular length were sorted into 8 diameter groups： 21-30, 31-40, 41-50, 51-60, 61-70, 71-80, 81-90 and 91-100 ram. The cracking force of the sliced tubers was determined using an adapted tensometer. Generally, the cracking force increases with increase in tuber slice length. While the average value across all diameters ranges from 504.65 N to 1,770.19 N as the tuber length varies from 25 mm to 150 mm for TMS 30572, it ranges from 428.32 N to 1,721.95 N for TMS 4（2）1425. Within the same diameter group, the compression cracking force for tubers of small lengths was significantly lower than that required for large tuber lengths. Further, while the average cracking force for TMS 30572 varies between 894.54 N and 1,287.16 N across varying diameter ranges, it varies between 715.47 N and 1,268.82 N for TMS 4（2）1425. The highest values for both varieties occur at diameter range 71-80 mm. The data generated would be useful for the development of an efficient cassava peeling machine, based on the principle of peel-flesh separation by compression and peel removal with knives.展开更多
文摘为解决污水源热泵中换热器防堵和防垢的问题,提出了带引射回流功能的污水旋流防阻机,并进行了砂水和生活污水分离试验。结果表明:该防阻机对砂子(75~250μm)和污杂物(<4 mm)均有较好的分离效果,分离效率分别为98.17%~100%和94.33%~96.96%。优化的溢流管与圆柱段长度比值的范围大小与离散相密度成正比。并且,引射回流装置的存在不仅实现了防堵和连续排污,还显著减轻了"溢流跑粗"的影响,提高了分离效率。防阻机的能耗基本不随溢流管与圆柱段长度比值的变化而变化,且总的能量损失较小(小于17 k Pa)。在保证较高分离效率的同时,分流比可以控制在较低的水平(小于10%),相比传统污水源热泵中的污水防阻机,可利用污水量大大提高。
文摘脉动热管是一种结构简单、传热性能突出的新型传热元件,由于运行过程涉及沸腾与冷凝及两相流动,传热及流动机理复杂,因此目前对其运行过程的相关数值模拟尚不成熟。本文采用VOF（volume of fluid）模型,考虑表面张力和壁面接触角的影响,采用数值模拟软件对单环路脉动热管的流动及传热特性进行了研究。数值模拟中,单环路脉动热管的充液率为40%～60%,热端加热功率为10～40W,探讨了热管蒸发段与冷凝段长度比对热管启动及换热性能的影响,并分析了脉动热管运行时流型特征。结果表明：随蒸发段和冷凝段长度比值增大,脉动热管启动时间缩短,且换热性能有一定提高;但在低充液率时,容易出现＂干烧＂现象。在低加热功率时,脉动热管的启动方式为温度突变式;而在高加热功率时,其启动方式为温度渐变式。此外,通过蒸发段的温度振荡特征可以确定脉动热管的启动时间。
文摘Radial compressive cracking force of two cassava varieties （TMS 30572 and TMS 4（2）1425） was determined. Tubers from plants about 1.5 years old, freshly harvested from the Teaching and Research Farm of Obafemi Awolowo University, Ile-Ife, Nigeria, were used for this study. The tubers were cleaned and sliced into different lengths ranging from 25 mm to 150 mm in steps of 25 mm. For each species, slices of a particular length were sorted into 8 diameter groups： 21-30, 31-40, 41-50, 51-60, 61-70, 71-80, 81-90 and 91-100 ram. The cracking force of the sliced tubers was determined using an adapted tensometer. Generally, the cracking force increases with increase in tuber slice length. While the average value across all diameters ranges from 504.65 N to 1,770.19 N as the tuber length varies from 25 mm to 150 mm for TMS 30572, it ranges from 428.32 N to 1,721.95 N for TMS 4（2）1425. Within the same diameter group, the compression cracking force for tubers of small lengths was significantly lower than that required for large tuber lengths. Further, while the average cracking force for TMS 30572 varies between 894.54 N and 1,287.16 N across varying diameter ranges, it varies between 715.47 N and 1,268.82 N for TMS 4（2）1425. The highest values for both varieties occur at diameter range 71-80 mm. The data generated would be useful for the development of an efficient cassava peeling machine, based on the principle of peel-flesh separation by compression and peel removal with knives.
