A diffusion model for drying of a heat sensitive solid under multiple heat input modes

To obtain optimal drying kinetics as well as quality of the dried product in a batch dryer, the energy required may be supplied by combining different modes of heat transfer. In this work, using potato slice as a model heat sensitive drying object, experimental studies were conducted using a batch heat pump dryer designed to permit simultaneous application of conduction and radiation heat. Four heat input schemes were compared: pure convection, radiation-coupled convection, conduction-coupled convection and radiation-conduction-coupled convection. A two-dimensional drying model was developed assuming the drying rate to be controlled by liquid water diffusion. Both drying rates and temperatures within the slab during drying under all these four heat input schemes showed good accord with measurements. Radiation-coupled convection is the recommended heat transfer scheme from the viewpoint of high drying rate and low energy consumption.     

Experimental Investigation of Drying Behavior of Carrots in a Fluidized Bed with Energy Carrier

A pilot scale fluidized bed dryer with inert particles as energy carrier was used to investigate the drying characteristics of carrot in this type of dryer. Glass beads, hollow steel balls and pieces of dry carrot were used as inert materials. The effects of sample diameter, inert material type, inert material diameter, amount of inert material, air velocity and temperature on the rate of drying were studied. It was found that the presence of inert particles enhances the rate of drying. The results of this study also revealed that, although the rate of drying increased with decreasing sample diameter, increasing of inert material thermal conductivity, and increasing of air temperature, but the inert material diameter and air velocity did not have any significant effect on the rate of drying. The independence of the rate of drying on air velocity in well fluidized systems, indicates that external diffusion is not the controlling step in this process. It was also found that the presence of inert materials caused the drying material to reach its final internal temperature more rapidly. The internal temperature of the drying material, also increased with increasing diameter and thermal conductivity of the inert materials.     

Dispersibility in water of dried nanocrystalline cellulose

Dispersibility is important for nanocrystalline cellulose (NCC) because recovering the unique suspension and particle properties is essential after the product has been dried for storage or transport. It is our goal to produce dried NCC that redisperses in water to yield colloidal suspensions without the use of additives or a large energy input. In contrast with the as-prepared acidic form of NCC (H-NCC), suspensions of neutral sodium-form NCC (Na-NCC) dried by evaporation, lyophilization, or spray-drying are readily dispersible in water. Suspension properties and NCC particle size determined by light scattering were used as indicators of dispersion quality. The neutral counterion content, drying technique, freezing action, drying and redispersion concentrations, and moisture content in the dried NCC were all found to influence dispersibility. When a minimum of 94% of the H(+) counterion is exchanged for Na(+), the neutral salt form is fully dispersible in water even when fully dried. Mild sonication is generally sufficient to recover measured particle sizes identical to those in the never-dried Na-NCC sample. A threshold moisture content of 4 wt % was found, above which dried H-NCC is fully dispersible in water.     

Drying of Tribenuron,a Thermosensitive Biochemical

The extension of microwave use in the biochemical industry was explored by drying tribenuron, a thermosensitive biochemical, in a microwave oven and in a thermal vacuum oven. Tribenuron wet cakes, containing a mixture of solvents, methanol and water, were heated at 40 °C in both ovens. Nitrogen purge was used to prevent the decomposition of tribenuron from prolonged heating. Microwave heating dried tribenuron in twenty minutes while the vacuum oven heating required eighteen hours to dry the wet cakes. In addition, the tribenuron quality was maintained under microwave drying, but deteriorated in the thermal vacuum oven. Therefore, microwave technology is more effective in drying tribenuron than conventional vacuum ovens. The results of this study are important for the use of microwave drying on a large scale in biochemical companies.     

Physical characteristics of decolorized chitosan as affected by sun drying during chitosan preparation

Some physical characteristics of decolorized chitosan as affected by sun drying, which was used to replace a bleaching step during chitosan preparation, were evaluated. One bleached and four unbleached chitosans were prepared and dried for 4 h by heat treatment at 60 °C or sun drying. The moisture content of chitosans dried by heat treatment was lower than that of chitosans dried by sun drying. Decoloration of the chitosan could be achieved more effectively by sun drying after deacetylation than by using a bleaching agent in the chitin preparation. Use of a bleaching agent significantly reduced the viscosity of the chitosan solution. A sequence of heat drying and sun drying in chitin and chitosan production (without using a bleaching agent) generally produced a whiter chitosan with higher viscosity without affecting water- and fat-binding capacities, compared to the bleached chitosan.     

Effect of drying methods on retention of moist sucralfate gel properties

The aim of this work was to find a drying procedure for moist sucralfate gel capable of producing dried sucralfate gel that retains the original gel properties of bioadhesion, rheology, and micromeritics. Spray-drying and microwave-drying procedures were employed. Mannitol was used as a gel-protective substance during the drying processes. The spray drying of moist sucralfate gel gave rise to a powder whose water suspensions showed significantly reduced viscosity. The bioadhesion of spray-dried sucralfate gel was strongly reduced by drying. When mannitol was used as a gel protector, the spray-dried sucralfate in part maintained the original bioadhesion of moist sucralfate gel. The preparation of a dried sucralfate gel retaining the bioadhesion characteristics, avoiding the use of mannitol, was made possible using the microwavedrying procedure. The microwave-dried product possesses a granular morphology suitable for direct compression because it is a free flowing and strongly coherent granular powder.     

成熟度与烘干温度对结球甘蓝种子质量的影响

以结球甘蓝品种冬升种子为材料,研究了不同成熟度和烘干温度下种子秕粒率、千粒重、发芽率、生理活性情况以及不同烘干温度下种子的含水量.结果表明,结球甘蓝冬升开花后45～55 d采收的种子,发芽率均达到了95%以上;随着种子成熟度提高,其种子质量、发芽活力及其超氧化物歧化酶(SOD)、过氧化物酶(POD)、脱氢酶活性显著上升,而相对电导率显著下降.与对照(自然风干)相比,30～50℃的烘干温度对种子千粒重和秕粒率无显著性影响,也仅在50℃下可使种子的发芽活力显著降低;随着烘干温度的升高,种子的SOD、POD和脱氢酶活性逐渐显著下降,相对电导率则逐渐显著上升;30～50℃烘干6 h种子的含水量由13.3%降至5.4%左右.研究发现,结球甘蓝冬升开花授粉后45 d种子已达到了采收程度,30～50℃烘干6 h种子含水量已达到储藏要求,并且愈接近自然干燥温度(30～40℃)的处理,种子发芽能力愈好;甘蓝种子活力与其SOD、POD和脱氢酶活性呈正相关,而与其相对电导率呈负相关.     

Whey valorisation: A complete and novel technology development for dairy industry starter culture production

Whey is the major by-product of the dairy industry, produced in large quantities and usually disposed off causing major environmental pollution, due to its high organic load that makes treatment cost prohibitive. This paper comprises a contribution on the valorisation of this high polluting liquid waste of the dairy industry, based on research for the production of novel dairy starter cultures using whey as raw material. Starter cultures are used for cheese ripening in order to: (i) accelerate ripening, (ii) improve quality and (iii) increase shelf-life. The developed technology involves biomass production from whey followed by thermal drying of cultures. Specifically, Kluyveromyces marxianus, Lactobacillus bulgaricus and kefir yeasts were thermally dried, and their efficiency in lactose and milk whey fermentations was studied. The most suitable culture regarding its technological properties was kefir, which was used for cheese ripening in freeze-dried and thermally dried form. Besides the reduction of production cost, which is an essential requirement for the food industry, the use of thermally dried kefir displayed several other advantages such as acceleration of ripening, increase of shelf-life, and improvement of hard-type cheese quality.     

Effect of decompression drying treatment on physical properties of solid foods

This study used a decompression drying instrument to investigate the effects of a drying treatment on the physical properties of solid foods. Commercial tofu was used as a model food and was treated at different temperature and pressure conditions in a drying chamber. Overall, high temperatures resulted in better drying. Additionally, pressure in the chamber influenced the drying conditions of samples. Differences in physical properties, such as food texture, shrinkage, and color were observed among some samples, even with similar moisture content. This was caused by differences in moisture distribution in the food, which seems to have manifested as a thin, dried film on the surfaces of samples. It caused inefficient drying and changes in physical properties. Control of the drying conditions (i.e. pressure and heat supply) has relations with not only physical properties, but also the drying efficiency of solid foods.     

A role for microwave processing in the dry preservation of mammalian cells

Dry preservation involves removing water from samples so that degradative biochemical processes are slowed and extended storage is possible. Recently this approach has been explored as a method for preserving living mammalian cells. The current work explores the use of microwave processing to enhance evaporation rates and to improve drying uniformity, thereby overcoming some of the challenges in this field. Mouse macrophage cells (J774) were pre-incubated in full complement media containing 50 mM trehalose, for 18-h, to allow for endocytosis of trehalose. Droplets of experimental and control (no intracellular trehalose) cell suspensions were placed on coverslips in a microwave cavity. Water was evaporated using intermittent microwave heating (600 W, 30 s intervals). Samples were dried to various moisture levels, rehydrated, and then survival was assessed after a 45-min recovery period using Calcein-AM/PI fluorescence and Trypan Blue exclusion assays. The metabolic activity of dried cells (4.3 gH(2)O/gdw) was assessed after rehydration using a resazurin reduction assay. Apoptosis levels were also measured. Post- rehydration survival correlated with the final moisture content achieved, consistent with other drying methods. Intracellular trehalose provided protection against injury associated with moisture loss. Metabolic assays revealed normal growth in surviving cells, and these survival levels were consistent with results from apoptosis assays (P > 0.05). Brightfield and fluorescence images of microwave-dried samples revealed a uniform distribution of cells within the dried matrix and profilometry analysis demonstrated that solids were uniformly distributed throughout the sample. Microwave-processing successfully facilitated rapid and uniform dehydration of cell-based samples.     

Near infrared reflectance spectroscopy (NIRS) to predict biological parameters of maize silage: effects of particle comminution, oven drying temperature and the presence of residual moisture

Maize silage nutritive quality is routinely determined by near infrared reflectance spectroscopy (NIRS). However, little is known about the impact of sample preparation on the accuracy of the calibration to predict biological traits. A sample population of 48 maize silages representing a wide range of physiological maturities was used in a study to determine the impact of different sample preparation procedures (i.e., drying regimes; the presence or absence of residual moisture; the degree of particle comminution) on resultant NIR prediction statistics. All silages were scanned using a total of 12 combinations of sample pre-treatments. Each sample preparation combination was subjected to three multivariate regression techniques to give a total of 36 predictions per biological trait. Increased sample preparations procedure, relative to scanning the unprocessed whole plant (WP) material, always resulted in a numerical minimisation of model statistics. However, the ability of each of the treatments to significantly minimise the model statistics differed. Particle comminution was the most important factor, oven-drying regime was intermediate, and residual moisture presence was the least important. Models to predict various biological parameters of maize silage will be improved if material is subjected to a high degree of particle comminution (i.e., having been passed through a 1 mm screen) and developed on plant material previously dried at 60 °C. The extra effort in terms of time and cost required to remove sample residual moisture cannot be justified.     

Changes in quality of Phellinus gilvus mushroom by different drying methods

This study was conducted to investigate the changes in characteristics of the Phellinus gilvus mushroom as influenced by drying methods after harvest. The lowest weight loss rate of P. gilvus mushroom was 75.8% with drying in the shade and 80% by dryer (60°C). The size loss rate of pileus was 19.3% of that in a hot air dryer (60°C). The hardness of dried material context using a hot air dryer (60°C) was the lowest (20 kg/cm²), and that by a dry oven (60°C) was the highest (457 kg/m²). For ΔE value, 4.9 of context and 2.6 of tubes using drying in the shade (20°C) were found to be the lowest. The survival rate of sarcoma 180 treated with P. gilvus dried in the sun was the lowest (51.8%), and this was considered the most effective method for antitumor activity against sarcoma 180.     

Preservation of Bacteria by Circulating-Gas Freeze Drying

Water-washed Serratia marcescens and Escherichia coli were freeze dried in a circulating-gas system at atmospheric pressure. This convective procedure resulted in a substantially higher survival of organisms than could be obtained by the vacuum method of freeze drying. There was little or no decrease in cell viability during convective drying when the residual moisture content was 15% or higher. Below this level, survival declined with decreasing moisture content. A detailed comparison of the convective and vacuum methods indicated that the advantage gained by freeze drying bacteria in air accrues in the early period of sublimation, at which time cells were found to be sensitive to vacuum drying but insensitive to air drying. An explanation for this difference is proposed, based upon the kinetics of water removal in the two processes. In brief, it is suggested that the convective method permits samples to be dried more uniformly; and regional over-drying, which may be deleterious even if transient, is thus avoided in achieving the optimal level of moisture.     

Inactivation mechanisms of lactic acid starter cultures preserved by drying processes

The preservation of lactic acid starter cultures by drying are of increased interest. A further improvement of cell viability is, however, still needed, and the insight into inactivation mechanisms of the cells is a prerequisite. In this present work, we review the inactivation mechanisms of lactic acid starter cultures during drying which are not yet completely understood. Inactivation is not only induced by dehydration inactivation but also by thermal- and cryo-injuries depending on the drying processes employed. The cell membrane has been reported as a major site of damage during drying or rehydration where transitions of membrane phases occur. Some drying processes, such as freeze drying or spray drying, involve subzero or very high temperatures. These physical conditions pose additional stresses to cells during the drying processes. Injuries of cells subjected to freezing temperatures may be due to the high electrolyte concentration (solution effect) or intracellular ice formation, depending on the cooling rate. High temperatures affect most essential cellular components. It is difficult to identify a critical component, although ribosomal functionality is speculated as the primary reason. The activation during storage is mainly due to membrane lipid oxidation, while the storage conditions such as temperature moisture content of the dried starter cultures are important factors.     

Effects of Drying Rates on the Desiccation Tolerance of Citrus maxima ‘Feizhouyou’ Seeds

The effects of drying rates on the desiccation tolerance of Citrus maxima ‘Feizhouyou’ seeds at different developmental stages were studied in this paper. For seeds harvested at 130 days after anthesis (DAA), 190 DAA, 245 DAA and 275 DAA, slow dried seeds had higher desiccation tolerance than those rapid dried, with difference at significant level (P < 005). However, such improvement was little for seeds harvested at 155 DAA and 220 DAA, indicating that effect of drying rate on desiccation tolerance depends on seed developmental stages. These results accorded with previous reports on orthodox soybean seeds and maize embrys. It was suggested that the effects of drying rate on desiccation tolerance of intermediate Citrus maxima ‘Feizhouyou’ seeds mainly resulted from expression and accumulation of some desiccation related proteins induced by slow drying. On the required genetic basis, desiccation tolerance in seeds can be induced only at suitable seed developmental stages.     

微波真空干燥大蒜片数学模型边界条件

本文通过确定大蒜片微波真空干燥的临界水分含量,修正Cu i等提出的胡萝卜片微波真空干燥动力学模型,使其适用于大蒜片,并对大蒜片与胡萝卜片微波真空干燥的临界水分含量不同的机理进行了探讨。采用质构仪和扫描电子显微镜分别对新鲜大蒜片、新鲜胡萝卜片以及干燥至边界条件下的大蒜片、胡萝卜片的质构和超微结构进行了测定。确定了大蒜片微波真空干燥的临界水分含量为Xw=1,在干燥后期对此模型进行了修正,修正系数为k=10.924e-3.2394Xw(0相似文献   

Effect of mild drying on the mineralization of soil nitrogen

Summary Drying soil to –100 kPa increased the subsequent mineralization of nitrogen under optimal moisture conditions. The effect was greater when the soils were dried to –1500 Pa. Mineralization was greater after four cycles of wetting and drying than after one. Depending on the drying conditions, the amount of nitrogen mineralized after drying to –1500 Pa was between 6.8 and 18.2% of that mineralized after chloroform fumigation. After drying the soils the average ratio of CO₂-C respired to min N was 21.1–22.3 depending on the drying conditions, whereas after chloroform treatment and autoclaving the ratio was 6.0 and 9.9 respectively. The effect of drying on nitrogen mineralization is attributed to two causes: the death and subsequent lysis of a small proportion of the soil organisms, and to the desorption of organic substances with a wide C/N ratio.Because of the stimulation of even mild drying conditions, marked differences in mineralization rates of soil nitrogen between cropping seasons must be expected.     

Fluidized-bed drying and storage stability of Cryptococcus flavescens OH 182.9, a biocontrol agent of Fusarium head blight

A method to produce dried granules of Cryptococcus flavescens (formerly Cryptococcus nodaensis) OH 182.9 was developed and the granules evaluated for storage stability. Small spherical granules were produced and dried using a fluidized-bed dryer. A drying and survival curve was produced for the process of fluidized-bed drying at 30°C. The granules were dried to different moisture contents (4, 7, 9 and 12%) and evaluated for storage stability at 4°C for up to a year. These different moisture contents granules had the following respective water activities (0.22, 0.38, 0.47 and 0.57 a _w). The results show the storage stability varied significantly across this moisture content range. The 9% moisture content sample had the best short-term stability (up to 4 months), while 4% moisture content had the best long-term survival (1 year). A desorption isotherm of C. flavescens was determined and modeled. The results of the storage stability and drying studies are interpreted in context of the desorption isotherm.     

New Method for Monitoring the Process of Freeze Drying of Biological Materials

A capacitive sensor was proposed and tested for the monitoring and control of a freeze drying process of a vaccine against the Newcastle disease of birds. The residual moisture of the vaccine was measured by the thermogravimetric method. The vaccine activity was determined by titration in chicken embryos. It was shown that, at the stages of freezing and primary drying, a capacitive sensor measured the fraction of unfrozen liquid phase in a material and allowed one to control the sublimation stage of drying in an optimal way. This prevented the foaming of the material and shortened the total drying time approximately twice. The control range at the sublimation stage of drying expanded up to −70°C. It was found at the final stage of drying that the signal of a capacitive sensor passed through a maximum value. We supposed that this maximum corresponds to the minimum of intramolecular mobility of biological macromolecules and hence to the optimal residual moisture of the material, which ensures long-term preservation of its activity. We also suppose that using the capacitive sensor at the final stage of drying allows one to more precisely detect the time when the residual moisture of dried material reaches the optimal value.KEY WORDS: biological materials, capacitive sensor, freeze drying, optimal residual moistureAt present, most biological materials containing live viruses or bacteria are exposed to lyophilization (i.e., drying from the frozen state); this ensures long-term preservation of their activity. Typically, this process consists of preliminary freezing and subsequent freeze drying. The latter process, in turn, consists of two stages: primary drying and secondary drying. During primary drying or sublimation, frozen water is removed from a biological product under vacuum and at temperatures below 0°C. At this stage, the drying rate is limited because of the foaming of a product that occurs due to its high temperature and the excess amount of liquid phase in it. The secondary drying, or final stage, begins after the end of the sublimation stage and occurs at temperatures above 0°C. The goal of the secondary drying is to bring the residual moisture of a biological product to an optimum level, which provides long-term preservation of its activity. Note that the moisture content both above and below the optimum value reduces the effective life of biological materials (1,2)To increase the shelf life of biological products, the following should be investigated: (1) the influence of the composition of the dried biological product and the residual moisture on the change in its activity over the time (3); (2) it is needed to optimize the sublimation drying process for different types of biological products (4). For the investigation of the of the state of water in the dried biologic drugs and the influence of the humidity of the biological on the change in their activity during shelf life, different physical methods are used such as neutron scattering (5), nuclear magnetic resonance (NMR) (6,7), Raman spectroscopy (8), infrared spectroscopy, differential scanning calorimetry, thermal activity monitor (9), and gravimetric sorption analysis (10). The investigations using these methods allow to find an optimum composition of a protective medium for biologics and to determine its optimal residual moisture.At all stages of the freeze drying, the parameters of the material and the parameters of the drying process (temperature of a material, the shelf temperature, the condenser temperature, the pressure in the sublimation chamber, etc.) are also monitored. According to these data, the mode of the process is selected to conduct him for the minimum time and get the best product quality (11). Usually during the drying process, the temperature is measured in several vials with biologic located on different shelves. The sharp increase of the temperature indicates the end of primary drying and the beginning of the secondary drying. The finish of the sublimation stage is revealed by a sharp decrease of the partial pressure of water vapor in the sublimation chamber (12,13). Note that the partial pressure of water vapor in the sublimation chamber does not characterize the state of the biological product to be dried and it is an indirect parameter. For monitoring and controlling the process of freeze drying, it is important to use the own properties of biological materials. In (14), a resistivity sensor placed in a frozen biological material was proposed to control the primary stage of freeze drying. A disadvantage of this method is that one cannot establish an unambiguous relationship between the amount of liquid phase in the frozen material and the value of resistivity: the resistance of the sensor depends not only on the amount of liquid phase but also on the concentration of dissolved salts. Another disadvantage of the resistivity sensor is that, when the temperature decreases, the resistivity of the material sharply increases to values that are difficult to measure, which makes impossible the control of the sublimation stage with this sensor.In (15,16), the interesting methods for determining the moisture of biological materials during secondary drying were proposed. These methods are based on the measurement of the partial pressure of water vapors in the sublimation chamber by NIR spectroscopy or Raman spectroscopy. Note that this method is indirect and requires laborious calibration to establish a correspondence between the current moisture of the biological material in vials and the pressure of water vapor in the sublimation chamber.It should be noted that one has to carry out a series of long-term experiments to find the optimal residual moisture of a biological product. These experiments result in the lifetimes of biological samples with various residual moistures. As the optimal residual moisture of a biological product, one takes the value that provides the longest term preservation of its activity.However, finding the optimal conditions of freeze drying has traditionally been a process of trial and error and required several experimental runs (17). Note also that the freeze drying process is time-consuming and labor intensive.A promising method for the investigation of the properties of biological materials is dielcometry (18,19). This method is relatively simple and very informative since it gives information about the structure of biological macromolecules and the state and role of water in the biological material, etc. This method was used in (20–22) for monitoring biological materials at the primary stage of freeze drying. In (20), authors had found an anomalous low-frequency dispersion of the dielectric permittivity in the biological under study and explain this phenomenon by the proton transfer among water molecules, connected by hydrogen bonds The dielectric relaxation time turned out to be sensitive to the loss of moisture content in the product, and the authors suggested to use of this phenomenon to determine the end point of the freeze drying process. The authors mounted the electrodes of the capacitive sensor on the outer surface of vials with the material to be dried. This approach allows monitoring the sublimation rate and determining the end of the primary stage of freeze drying. Unfortunately, the sensitivity of the capacitive sensor of this design is not enough for the reliable monitoring of the stage of secondary drying.In this paper, a new design of a capacitive sensor and measurement technique are proposed that enable monitoring all stages of the drying process: the freezing stage, the sublimation stage, and the final stage. During freezing and the sublimation stages, the sensor monitors the amount of liquid phase in the frozen material. This allows an optimal control during the whole sublimation stage which prevents the foaming of the material and significantly reduces the total drying time. The sensor also fixes the end of the sublimation stage and the beginning of the final stage of drying. At this stage, the high sensitivity of the measuring system enables one to discover that there is a certain time interval when the signal of the capacitive sensor passes through a maximum. We believe that this maximum corresponds to the minimum of the molecular mobility of biological macromolecules and the optimal residual moisture of the material to be dried.     

三温模型——基于表面温度测算蒸散和评价环境质量的方法Ⅰ．土壤蒸发

 三温模型是近年提出的测算蒸散量和评价环境质量的一种方法,因为该模型的核心是表面温度、参考表面温度、气温,所以被称为“三温模型”。该文通过理论分析结合实验的方法, 讨论了用三温模型测算土壤蒸发量的方法及其验证。通过引入没有蒸发的参考土壤的概念, 三温模型中用下式计算土壤蒸发量：LE=Rn-G-(Rnd-Gd)(Ts-Ta)/Tsd-Ta 式中,E为土壤蒸发量,L为水汽的汽化潜热,Rn和Rnd为蒸发土壤面和参考土壤面的净辐射, G和Gd为蒸发土壤和参考土壤热通量,Ts、Tsd、Ta分别为蒸发土壤的表面温度、参考土壤表面温度、气温。试验结果表明,在参考土壤和蒸发土壤中,能量通量存在明显差异,参考土壤中的土壤热通量和净辐射通量均小于蒸发土壤,而显热通量则大于蒸发土壤;在一般情况下,参考土壤的表面温度最高,蒸发土壤表面温度次之,大气温度最低,在土壤湿润时,这些差异更为显著。 经过与大型称重式蒸渗仪的实测值比较,三温模型能较好地计算土壤蒸发量,在22 d的实验期间内,绝对平均误差仅为0.17 mm•d^-1,相关系数达r²=0.88。与热电偶测温结果相比较 ,采用红外温度计测温的结果更为精确,和实测值的绝对平均误差仅为每天0.15 mm•d ^-1,相关系数达r²=0.94,表明三温模型有较好的精度。另外,三温模型在计算土壤蒸发量时, 所需要的参数种类少（净辐射、土壤热通量、温度）,不含经验系数,不需要空气动力学阻抗和表面阻抗等参数,因此简便实用,具有较好的应用前景。