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Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Heat exchangers serve as pivotal components in heat exchange systems. Compared with the straight channels, spiral channels have better performance due to the curvature of the centrifugal force generated by the secondary flow. Consequently, heat exchangers employing spiral channels find widespread application in agricultural engineering, including greenhouse air conditioning, water circulation systems, and agricultural product processing and storage for effective heat management. In this paper, we propose enhancing the heat transfer efficiency of spiral channels by introducing corrugations with longitudinal fins on the outer channel wall. To elucidate the impact of corrugation, we establish three-dimensional models of smooth spiral channels, corrugated spiral channels, and corrugated spiral channels with longitudinal fins. Initially, we investigate the influence of corrugated number on flow and heat transfer performance numerically. Through comparative analysis involving the development and variation of velocity and vorticity fields, average Nusselt number Nu, fanning friction factor f, average Dean number Dnm, secondary flow intensity Se under different corrugated numbers, and the Performance Evaluation factor of heat exchanger based on Comprehensive (PEC0), insights are drawn. Subsequently, longitudinal fins are integrated into the corrugated spiral channel, and a numerical study is conducted to assess the effect of varying geometric parameters of the longitudinal fin on the fluid flow and heat transfer performance inside the channel. Analysis of different longitudinal fin widths and heights on velocity and temperature fields, Nu, f, and Performance Evaluation factor of heat exchanger based on Comprehensive (PECw) of the channel is performed. The findings indicate that corrugated spiral channels outperform smooth spiral channels in heat transfer and flow performance. With increasing corrugated number n, secondary flow intensity within the corrugated spiral channel intensifies. Notably, at a Reynolds number of 550, a multi-vortex structure emerges in the corrugated spiral channel with a corrugated number of 21. At Reynolds number 750 and corrugated number 21, the Nusselt number of corrugated spiral channel increases by 47.08% compared to the smooth spiral channel. At the same time, the resistance loss in the channel also increases, and the Fanning friction factor of the corrugated spiral channel increases by 59.20%. When the Reynolds number is 750, the PEC0 of the corrugated spiral channel with 18 corrugations is the highest, which increases by 27.66% compared to the smooth spiral channel. On this basis, longitudinal fins are added to the corrugated spiral channel, and it is observed by numerical simulation that symmetrical longitudinal vortices are induced by the fins. Further, the longitudinal fins induce symmetrical longitudinal vortices, enhancing flow and heat transfer in the channel's middle section. Under the condition of constant fin width and increasing fin height, the comprehensive heat transfer performance of the channel has a maximum value, that is, when fin width w=1/3W, fin height h=1/6H and Reynolds number Re=250, the highest PECw is 1.157. When the fin height is fixed, increasing the fin width w will also make the PECw of the channel first increase and then decrease. The correlation formulas for Nusselt number Nu, Fanning friction factor f and secondary flow intensity Se in corrugated spiral channel are fitted, with deviations within ±14.0%, ±10.2% and ±4.4%, respectively. This provides a certain reference for the application of corrugated spiral channels with longitudinal fins in the thermal design and usage of heat exchangers. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In high latitude region of western China, the environment is in harsh condition that it is cold and dry in winter and has long ice period, which causes many water resource problems. In order to relieve the serious water shortage condition in cold and dry region, a large number of long distance water diversion projects were established to improve the water resource condition, such as increasing farm irrigation, human and animal drinking. While the ice damage occurs frequently under severe ice conditions in cold and dry region, especially in ice period in winter and thawing period in spring, it is easy to form drift ice with different velocities, different plan sizes and different thicknesses, which produces different extrusion forces or impact forces to damage tunnel lining, causing project failure. The failure project could not realize the original planning and construction goal, giving rise to the water allocation pressure. The water allocation would cause water shortage which influences diversion irrigation and farming production in spring. Based on the intense researches on the collision simulation problem of the interaction between drift ice and diversion tunnel, this paper used the symmetric penalty function in the finite element contact-impact algorithm to conduct the theoretical study on collision simulation problem between drift ice and water diversion tunnel. ANSYS/LS-DYNA was adopted as the platform to establish tunnel model and drift ice model. LS-DYNA SOLVER was used as the solver to solve and analyze the damage degrees of drift ice on tunnel. The physical model tests were conducted to verify and reveal the impact damage mechanism of drift ice on diversion tunnel. The physical model was constructed by the geometric scale of 28, which is the ratio of the experiment facility to the prototype in the test. The results show that tunnel lining surface will form varying degrees of deformation and failure when the tunnel lining is impacted by the drift ice with different velocities, different plane sizes and different thicknesses. It is also discovered that the impact stress increases with the flow velocity and their relationship presents linear variation. The impact stress also increases with the drift ice’s plane size and their relationship presents nonlinear variation. The impact stress increases with the drift ice thickness when the drift ice thickness is less than 0.5 m. While the drift ice thickness is greater than 0.5 m, the maximum stress value shows little change. The relationship between drift ice’s plane size and maximum stress shows approximately linear variation. Meanwhile, the software simulation and test observation results are almost the same. The impact of drift ice on the tunnel lining would cause the deformation of lining, but the deformation has little influence on the tunnel stability. The drift ice’s long time erosion would cause the tunnel lining surface to fall off, and further break the strength and stability of the tunnel structures. The study supplies theoretical support and technical guarantee for water diversion project security in cold and dry region of western China. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to obtain more information about the clearance flow in a centrifugal pump and provide further reference for the design of centrifugal pumps, this paper researched and analyzed the distribution of radial force and pressure fluctuation of the impeller in a centrifugal pump via using the methods of the numerical simulation and the verification of experiment. Numerical calculations and experiments were carried out with different seal ring clearances which were respectively 0.25, 0.5 and 0.75 mm. The special speed of model pump was 69. On the one hand, after numerical simulation the influence of different seal ring clearances on the impeller radial force was obtained by calculating and analyzing the pressure of outer surface of impeller. On the other hand, the pressure pulsation signals were obtained by experimental measuring at monitoring points that included 8 locations. Of those, 6 monitoring points were arranged at the seal ring and volute, and 2 monitoring points were arranged at the impeller inlet. According to the clearance size of model pump seal ring (0.25, 0.5 and 0.75 mm), there were 3 cases. The comparison of 2 head curves from the numerical calculation and the experiment showed they had good agreement. The influence of the seal ring clearance on the pressure pulsation of the model pump could be changed obviously with the changing of the condition and the location of the monitoring points. And there was an optimum size of the seal ring clearance with which the pressure pulsation amplitude under the design condition was the smallest. At the inlet of the front cavity, the pressure pulsation amplitude of the case of 0.25 mm was about 3.1 times that of the case of 0.5 mm, and about 1.3 times at the impeller outlet. When the seal ring clearance was 0.25 mm, the mean pressure pulsation amplitude of the wear-ring was the minimum. At this time the pressure pulsation amplitude of the case of 0.75 mm was about 1.24 times that of the case of 0.5 mm. At the impeller inlet and its upstream, the pressure pulsation amplitude of the case of 0.75 mm was about 0.67 times that of the case of 0.25 and 0.5 mm. The radial force of the impeller was changed by the changing of the seal ring clearance. With the increasing of the seal ring clearance, the leakage of the fluid flow increased, which not only changed the pressure fluctuation at the impeller inlet and outlet, but also induced the pressure fluctuation at the inlet of the front cavity. For the pressure fluctuation under the design condition, there was an optimum value of the seal ring clearance, with which the pressure fluctuation amplitude was the minimum. At the same time, the radial force of the impeller changed with the changing of the pressure along the outer surface of the impeller, and the total radial force changed nonlinearly. The traditional design of the centrifugal pump has been carried out by studying the pressure fluctuation and the radial force induced by different seal ring clearances. By studying the changing of pressure pulsation signals and radial forces, this paper provides the reference for the traditional design of centrifugal pumps. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Silo is widely used in grain, logistics, electric power, metallurgy and other industries. Therefore, the reasonable design of silo structure is the key. China is a large country of grain production, with application of the modern granary environmental protection, energy saving, green and other concepts, the cylinder wall is higher, and larger diameter, occupies less land, saves resources of the silo and is more and more in line with the future development trend of granary, and with the trend of rapid development around the world. With the increasing height and diameter of silo, the problem of failure in silo discharging is becoming more prominent. The dynamic lateral pressure of grain silo during discharging is the major cause of silo failure. In this paper, based on the indoor grain silo discharging model test, the whole process of the silo center emptying was recorded with high-speed camera, the flow pattern of grain was analyzed with image processing technology, and the dynamic pressure generated during the discharge process was measured. Based on this test, the particle flow code (PFC3D) was used to carry out numerical simulation to track the movement of specific particles in the test. By comparing the results of the experiment and the numerical simulation, the mechanism of overpressure in the discharge of the silo was explored. Through this study, in the process of discharging in the center, there were two kinds of flow states, the mass flow and the tubular flow. At the beginning of the discharge, the stored material flowed as mass flow. After a period of time, the upper part of the material flowed as mass flow, the bottom of the storage was a tubular flow, and the mass flow was in the high diameter ratio close to 1 of the height position to convert to tubular flow. When the discharging height reached 1.1m, the stored material flowed in tubular flow until the discharge was completed. Both the dynamic lateral pressure and the static lateral pressure increased with the depth of the measuring point, and the dynamic lateral pressure was greater than the static lateral pressure. At the beginning of the discharge, the dynamic lateral pressure measured by the silo suddenly increased, and then the dynamic lateral pressure value decreased with the continuous reduction of the storage height. The overpressure coefficient measured by the three groups of sensors was larger in the height range of the high diameter ratio close to 1, and the overpressure phenomenon was obvious. In the process of silo discharging, the speed of tubular flow of the bottom stored material was greater than the speed of the mass flow of the middle and upper stored material. There was a pressure arch at the junction of the two flow states, and the existence of the pressurized arch hindered the normal flow of the upper stored material, which led to the self-weight of the stored material and the additional force caused by the change of momentum was almost entirely by the arch, resulting in the increase of the dynamic lateral pressure and a significant overpressure phenomenon. [ABSTRACT FROM AUTHOR]

Sprinkler irrigation is one of the main water-saving irrigation methods at home and abroad. As a common water-saving irrigation equipment, impact sprinkler is widely used in landscaping and agricultural irrigation fields. The traditional impact sprinkler with circle spray filed has the disadvantages of overlap spray, excessive spray and missing spray. In response to above disadvantages, impact sprinkler with square spray field has been improved but it remains facing many problems such as complicated mechanical structure, excessive head loss, and it’s spray shape deviates from square. In order to reduce the local head loss, the inner passageway of spray’s flow regulator consist of hollow shaft and threaded pipe was optimized with streamline. To achieve the goals of accurate square spray field, the docking port between hollow shaft and threaded pipe was reshaped with diamond shape as entry end connect to threaded pipe and star shape as export end connect to hollow shaft. The improvement above can effectively reduced the head loss that was unfavorable to the spray shape, and improved the range and spray shape factor. To evaluate the drag reduction effect in passageway of sprinkler, the flow regulator was divided into four part according to it’s inner flow state. Then the head loss formulas for each part were derived by energy equation and momentum equation of hydrodynamics. The whole head loss of the optimized flow regulator was expressed as sum of the four parts head loss related to their flow velocity and loss coefficient effected by passageway’s shape at last. The flow velocity of each part could be obtained by simulating which was conducted in this paper. This work provided a theoretical basis for the selection of the flow regulator inlet and outlet and flow passage optimization of the square spray field impact sprinkler. For global flow analysis and provide flow velocity result for head loss calculation, the three-dimensional unsteady numerical simulation of the inner flow path of the square spray field impact sprinkler was carried out. The 3D geometric model of flow regulator was established using Pro/E software. The distribution regularities of velocity and pressure were simulated by FLUENT software with the RNG k-ε turbulence model. Pressure inlet was set as the inlet boundary condition in the model, with the working pressure 250, 300, 350, 400, 450 and 500 kPa respectively. According to the relationship between the flow rate and the range of the same type of Rain Bird impact sprinkler without the flow regulator, the range of four corners of a square spray field sprinkler with optimized flow regulator was calculated. According to the working equation of the square spray impact sprinkler, the variation rule of the range under different rotation angles can be obtained. Finally, comparting with the same type of Rain Bird sprinkler, the optimization effect of the square sprinkler was evaluated by the variation of the head loss, flow rates, range change and spray shape, and the reliability of the results was verified. The results show that the new type of square spray field sprinkler is simple in structure, hydraulic automatic control, energy saving, durable and convenience, and has standard spraying shape with small head loss. Compared with the square spray field sprinkler before optimized, the head loss of the optimized square spray field sprinkler in the rated working pressure reduced by 25.8%. The flow regulator range of the improved sprinkler is enlarged, with maximum flow rate increasing by 12.87% and minimum decreasing by 12.83% respectively. In addition, the spray shape factor is 86.89% which rises 15.5% and the out spray reduces 9.85%. This provides a theoretical reference for the design, manufacture and application of the square spray field sprinkler. [ABSTRACT FROM AUTHOR]

Cracks are common in nature and affect a number of soil properties. They increase the permeability, reduce the soil strength and stability, and thus affect the growth of plant roots. This paper presented a model for crack formation which was introducing the correlation length to constructing the soil critical strain random field to optimize the cracking model. The model was based on a lattice of Hookean springs with finite strength and the critical strain. The concept of correlation length was introduced to constructs the critical strain random field, the correlation length was used for reflects the spatial continuity of the soil. The critical strain random fields were generated using program written by Fortran language. The model reproduced the dynamics characteristic of the development of crack network in nature, and some of the parameters of the model represented the physical properties of the soil. We processed the digital images to quantitatively analyze the geometric characteristics of cracks. The typical procedure of digital image processing included: the color image of the crack patterns was converted into a gray one, the gray image was further changed into a binary one with the threshold division method. After the process, the cracks and aggregates were simply distinguished in a black-white image, in which the black lines and the white areas represent the crack networks and the aggregates, respectively. We optimized the threshold to make the binary images as clear as possible, and processed the images through binarization, noise removal and edge extraction of crack for extraction of morphological properties. Finally, the influence on model simulation cracking of spatial correlation length, heterogeneity in random field was analyzed. Comparison of crack area, crack length, Euler number density by calculating experiment and simulation images, it could be drawn that crack morphology could be described by Minkowski area, length, Euler number density effectively. By calculating the average μ, standard deviation δ of cracks area, length, Euler number density, the images of average density value μ and μ±δ are basically the same in the change trend between experimental and simulated process. After calculation, the coefficients of determination R2 for the area, length and Euler number density are all larger than 0.5, and the root mean square error and deviation are small enough. The consistency index IA quite approach to 1, which indicating that the calibration results are satisfactory. The two models are compared, among them the determination coefficient R2 is between 0.889-0.968, the consistency index IA is between 0.964-0.993, which reflecting the dynamic cracking process of cracks well. The greater the correlation length and the smaller the variance, the lower the discretization degree of the random field, that the more uniform the soil cracking. On the contrary, there are mainly isolated cracks. And the mean value is too small, the whole strain of the random field is low, the simulated crack does not consistent with the development of the natural crack. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Solar liquid desiccant air-conditioning system has attracted many attentions owing to the advantages of utilizing low grade thermal energy such as solar energy, in which the solar collector and regenerator can be designed respectively. In addition, solar collector and solution regenerator can be combined together to construct solar collector/regenerators (C/Rs) that have better performance of regeneration. Solar C/Rs are the key component of system, because the cooling capacity of system is determined mainly by the regeneration efficiency. Moreover, in order to reduce top heat losses and eliminate contamination of the solution by dust, the C/Rs can be covered with the glazing plate. An experimental study on the effect of glazing plate height of solar C/Rs indicated that the optimum glazing plate height is 0.07 m, and the performance of the optimally glazed C/R is better than an unglazed C/R for hot humid climates. Analysis based on experimental data and numerical simulation was presented, and the results show a higher inlet solution temperature can increase the performance of regeneration. So the method of preheating the inlet solution was adopted to increase the efficiency of solar C/R, and solution heat recovery device was used to preheat the inlet solution by recovering the heat from the outlet solution. However, there have not been sufficient studies on the effect of various parameters on C/R performance with solution heat recovery. In this paper, the solution heat recovery device, by recovering heat from the outlet solution to preheat the inlet solution, was adopted to increase the efficiency of solar C/R. The numerical simulation method was adopted for analyzing the effects of the glazing plate height, solution parameters, air parameters, solar radiation intensity and other factors on the regeneration efficiency of solar C/R with solution heat recovery. Several physical assumptions were made, followed by modeling of counter-flow regeneration. And the previous experimental data were used for the comparison with the numerical results to validate numerical model. In the simulation conditions, the results show: Using a heat recovery device can improve the regeneration efficiency by 93.6% equivalent to adding 0.8 m length of C/R; the higher efficiency of heat recovery device causes the higher regeneration performance; the flow rates have an optimum value, which yields a maximum rate of water evaporation and regeneration efficiency. The optimum values of flow rates of solution (or air) increased with the increase in air flow rate (or solution flow rate), and the optimum ranges of flow rates of solution and air are 8-15 and 100-150 kg/h, respectively. The optimum range of glazing plate height is 0.08-0.1 m when flow rates are in the optimum ranges; higher inlet temperature of solution or air both can increase regeneration efficiency, but the method of heating solution is much more effective than heating air; the decrease of inlet concentration of solution or relative humidity of air both can be in favor of solution regeneration; the higher solar radiation intensity yields better performance of regeneration for the solar CR with heat recovery. All these results can provide guidance for the design and performance analysis of the solar CR. [ABSTRACT FROM AUTHOR]

Preferential flow refers to such a flow transport pattern that water and solute flow round soil matrix, which accelerates soil water movement. Soil cracks are a part of reasons that lead to preferential flow. This study aimed to analyze soil preferential flow pattern in order to establish a model of preferential model based on soil fracture network. A field color tracer experiment was carried out in Ningxia University from July to September in 2015 under precipitation intensity of 20 and 50 mm/h, and rainfall duration of 20-60 min. The results showed that when the rainfall intensity was 20 mm/h, the water infiltration depth increased with the increase of rainfall duration and the preferential flow began to develop, but it was still overall-matrix flow and the preferential flow was only locally developed. When precipitation intensity was 50mm/h and the duration of rainfall was 20min, water flows bypassed the soil matrix and preferential flow phenomena was observed obviously. The infiltration depth exceeded the fracture depth after duration of rainfall increased to 50min, soil fracture had not play a major role in the soil water movement, and the flow patterns were overall-matrix flow. The results showed that the flow patterns were mainly matrix flow under lower rainfall or irrigation intensity, and preferential flow under higher rainfall or irrigation intensity. A coupling model of soil matrix and fracture network for simulating preferential flow was established (CP model). In this model, the soil medium was divided into matrix and fracture networks formed by flow channels, each having its own saturated hydraulic conductivity and water movement equation. These equations were solved by using the control volume finite element method, and the nonlinear equations were linearized by Newton-Raphson methods to improve the convergence, and shorten the operation time. Equation of water movement in matrix and fracture network flow equation were coupled using global approach which solved the problems of the flow mutual influence caused by the cross-fracture network, and improved the computational efficiency. The validity of the proposed model was tested by the analysis of the soil moisture content between the simulated and the observed values. The results showed that the root mean squared error (RMSE) of soil moisture was 0.016-0.025, R2 of soil moisture was above 0.78, bias was 0.020-0.026, index of agreement (IA) was 0.918-0.938, indicating good simulation by the CP model. In the end, different crack structure but statistically equivalent networks was generated to validate the model simulation and produced well simulation results. These numerous fractures had stable effect on the variances of soil moisture. The results of this paper can provide valuable information for analyzing preferential flow and the coupling mechanism of the water content and solute transport between soil dry shrinkage crack and soil matrix. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)