STUDIES ON THE EFFECTS OF PARTICLE CIRCULATION DURING DRYING OF SUSPENSIONS IN A MECHANICALLY SPOUTED BED DRYER WITH INERT PACKING

ABSTRACT

A comparison was made between alternate air conditioning methods used to dry large round forage bales. Energy consumption durin drying and the final nutritional qualit of the bales were measured durin ti% study. The methods used to increase tge drying potential of the air incfuded using a desiccant to dehumidify the drying air; a gasoline engine to drive the fan and heat the drying air and the use of direct electric heat to increase the temperature of the dr ing air.

The results from the study indicate that the energy consumption was least with the use of a desiccant but the regeneration ma only be economically feasible where waste heat is available to provide tKe enery The gasoline engine was less efficient than the application of electric;. No difference in the nutritional quality of the forage due to heat damage during the drying process was noted.     

COMPARISON Of STRATEGIES FOR AMBIENT-AIR DRYING OF LARGE ROUND BALES

A comparison of the drying efficacy of ambient-air drying of large forage bales was made between positive and negative pressure systems. Both systems effectively dried the bales to the desired average moisture content, but regions of higher moisture content within the bales were measured with the two systems. Energy consumption as expressed as the ratio of the energy consumed/weight of moisture removed was similar for both drying systems. Final configuration of the drying system will depend on whether heat is required to speed the drying process in order to meet the capacity of the harvesting system.     

COMPARISON Of STRATEGIES FOR AMBIENT-AIR DRYING OF LARGE ROUND BALES

ABSTRACT

A comparison of the drying efficacy of ambient-air drying of large forage bales was made between positive and negative pressure systems. Both systems effectively dried the bales to the desired average moisture content, but regions of higher moisture content within the bales were measured with the two systems. Energy consumption as expressed as the ratio of the energy consumed/weight of moisture removed was similar for both drying systems. Final configuration of the drying system will depend on whether heat is required to speed the drying process in order to meet the capacity of the harvesting system.     

Performance of a recirculating dryer equipped with a desiccant wheel

This article reports the incorporation of a rotary desiccant wheel unit into an air recirculated convective dryer and testing it by drying corn kernels. Experiments were conducted with and without the desiccant wheel at air temperatures of 50, 60, and 70°C and flow rates of 1, 1.4, and 1.8 kg/min. The effect of drying temperature, air flow rate, and desiccant wheel on drying time, drying rate, energy consumption, and specific moisture extraction rate were investigated. Statistical analysis of data showed that air drying temperature and air flow rate had significant effects on drying time and drying rate and the effect of desiccant wheel on drying time was significant. Results indicated that a desiccant wheel is an economical and useful system to utilize in dryers because it decreases drying time while increasing the drying rate and has a positive influence on energy consumption.     

Low Temperature Peanut Drying Using Liquid Desiccant System Climatic Conditions

Field-dried peanuts having 25% average moisture content have been dried by using a liquid dasiccant drying system. This system cansirts of climate simulation subsystem, closed loop air drying subsystem, and regeneration subsystem. The closed loop drying subsystem used in this investigation provides low temperature drying with a little increase in drying air temperature. Regeneration temperature, liquid desiccant concentration, and air flowrate in the drying subsystem have heen kept unchanged during the experiments, but air of different humidity have been used to regenerate the liquid desiccant. Experimental measurements of the system performance have been carried out utilizing a new cost effective desiccant mixrure (CELD) which is composed of equal portions by weight of lithium chloride and calcium chloride. The drying process has been performed using different climatic canditions in the regeneration process. Experimental rasults demonstrate that drying peanuts by the use of a liquid desiccant system is promising.     

ENERGY CONSUMED IN LOW TEMPERATURE CORN DRYING

Data collected on corn drying bins employing unheated air and bins utilizing electric heat for small air temperature rises indicate better energy efficiency when the energy is used to provide more air as compared to using a portion of the energy to increase the temperature of a smaller quantity of air. Unheated air drying of shelled corn was accomplished with an average of about 6.0 kWh per metric ton per percentage point of moisture removed as compared to an average of about 12.0 kWh/t- % when electric heaters were used to increase the air temperature. Final corn moisture content was approximately the same for both methods since the unheated air drying systems, with more air per unit of grain, completed drying earlier. Early fall weather, as contrasted to late fall, is generally more favorable to drying and the existence of lower average daily relative humidities permit the drying of corn to 15% or less, wet basis, without the addition of heat.     

Low Temperature Peanut Drying Using Liquid Desiccant System Climatic Conditions∗

ABSTRACT

Field-dried peanuts having 25% average moisture content have been dried by using a liquid dasiccant drying system. This system cansirts of climate simulation subsystem, closed loop air drying subsystem, and regeneration subsystem. The closed loop drying subsystem used in this investigation provides low temperature drying with a little increase in drying air temperature. Regeneration temperature, liquid desiccant concentration, and air flowrate in the drying subsystem have heen kept unchanged during the experiments, but air of different humidity have been used to regenerate the liquid desiccant. Experimental measurements of the system performance have been carried out utilizing a new cost effective desiccant mixrure (CELD) which is composed of equal portions by weight of lithium chloride and calcium chloride. The drying process has been performed using different climatic canditions in the regeneration process. Experimental rasults demonstrate that drying peanuts by the use of a liquid desiccant system is promising.     

热湿条件下溶液除湿空调的性能分析

基于温-湿度独立控制理论,结合热湿地区的气候特点,设计了复合型太阳能溶液除湿空调系统(CSLDAS),通过建立热质传递控制方程,模拟分析了CSLDAS的除湿/再生性能和运行能耗。结果表明,CSLDAS能够综合利用多种可再生能源,有效降低空调能耗,并可有效增强除湿器/再生器的除湿/再生能力,减小对太阳辐射强度的依赖。本研究可为溶液除湿空调在热湿地区的节能设计提供理论指导。     

压缩空气溶液除湿中不同除湿剂除湿性能比较

在压缩空气溶液除湿实验平台上,分别以LiBr和LiCl水溶液作为除湿剂,实验研究了两种溶液在压缩空气溶液除湿系统中的除湿性能。以溶液表面水蒸气分压力作为比较基准,压缩空气出口含湿量和除湿量作为除湿性能的评价指标,对二者的除湿能力进行比较分析。同时基于压缩空气溶液除湿器传热传质模型,结合实验数据,研究了LiBr、LiCl溶液与压缩空气间的传质系数大小以及变化规律。结果表明：在相同的处理工况下,采用LiCl溶液对压缩空气进行除湿能得到更低的空气出口含湿量和更高的除湿量,LiCl溶液除湿过程的传质系数也高于LiBr溶液,即在压缩空气溶液除湿系统中LiCl溶液具有更优的除湿能力和传质性能。     

ENERGY REQUIREMENTS FOR DRYING LARGE ROUND BALES

Uniform density and softcore large round forage bales were dried under a variety of airflow and temperature regimes. The energy required to operate the fans and heaters was measured as the bales dried to an average final moisture content of 18 percent, wet basis. The energy requirement for drying both types of bales was found to be 33 kWh/tonne dry matter/moisture point reduction.

The soft-core bales tended to dry at a faster rate than the uniform density bales. Also, the final moisture content variation within the softcore bales was less than that within uniform density bales.     

ENERGY REQUIREMENTS FOR DRYING LARGE ROUND BALES

Uniform density and softcore large round forage bales were dried under a variety of airflow and temperature regimes. The energy required to operate the fans and heaters was measured as the bales dried to an average final moisture content of 18 percent, wet basis. The energy requirement for drying both types of bales was found to be 33 kWh/tonne dry matter/moisture point reduction.

The soft-core bales tended to dry at a faster rate than the uniform density bales. Also, the final moisture content variation within the softcore bales was less than that within uniform density bales.     

Simulation design and evaluation of hybrid PV/T assisted desiccant integrated HA-IR drying system (HPIRD)

The aim of this research is to make a simulation design for a hybrid PV/T assisted desiccant integrated HA-IR drying system (HPIRD) which has two components: a photovoltaic air collector (PVAC), and a desiccant silica gel bed (DB). The PVAC and DB have been improved by fins and different bed shapes for improved performance of the drying system. The designed simulation system used TRNSYS and CFX programs with new PVAC and DB components. The two new models were used to develop a new drying system and compared it with a common system. The drying test chose the optimal simulated case and compared it with the experimental results.The simulation results indicated that the PVAC_AF and v-shape DB were suitable, and they also indicated consistent results when compared to the experiment. Thus, the HPIRD used the optimal case to develop a system. The performance evaluation studies indicated that the HPIRD drying test at 60 °C and velocity of 0.6 m/s reduced the drying time by 44% with less energy consumption (63%) compared to hot air drying. HPIRD drying also gave better results over hot air-infrared drying. Finally, drying time, drying rate and energy consumption were reduced considerably with the hybrid drying system.     

Impact of alcohol-gasoline fuel blends on the performance and combustion characteristics of an SI engine

In this study, the effects of ethanol-gasoline (E5, E10) and methanol-gasoline (M5, M10) fuel blends on the performance and combustion characteristics of a spark ignition (SI) engine were investigated. In the experiments, a vehicle having a four-cylinder, four-stroke, multi-point injection system SI engine was used. The tests were performed on a chassis dynamometer while running the vehicle at two different vehicle speeds (80 km/h and 100 km/h), and four different wheel powers (5, 10, 15, and 20 kW). The results obtained from the use of alcohol-gasoline fuel blends were compared to those of gasoline fuel. The results indicated that when alcohol-gasoline fuel blends were used, the brake specific fuel consumption increased; cylinder gas pressure started to rise later than gasoline fuel. Almost in the all test conditions, the lowest peak heat release rate was obtained from the gasoline fuel use.     

DESICCANT GRAIN APPLIED TO THE STORAGE OF SOLAR DRYING POTENTIAL

Sorption storage of solar heat using a layer of wheat as the desiccant was analyzed by means of a deep-bed drying model. Intended to be applied to solar-assisted in-storage drying of agricultural bulk materials, the probability of the persistence of unfavorable weather periods was quantified statistically for Potsdam for the month of August, as an example. Simulation results demonstrate that a relative humidity of the drying air of 65 % can be maintained day and night for weeks without combustion of fossil fuels. Using a simple strategy of control, periods with insufficient solar radiation can be bridged over. The desiccant grain is not endangered by mold growth as a matter of principle. Simple solar air heaters can be used to avoid economic losses due to overdrying and to reduce the danger of decay to a minimum even at unfavorable climatic conditions.     

Experimental investigation on compressed air drying performance using pressurized liquid desiccant

As a new compressed air-drying method, the compressed air dehumidification using a pressurized liquid desiccant was proposed in our previous study. The pressurized dehumidifier is a complex and core component of the drying system. The mass transfer performance between the compressed air and LiCl aqueous solution is experimentally studied in a counter-flow pressurized dehumidifier filled with structured packing. The humidity ratio of outlet compressed air, vapor removal of processed compressed air, moisture removal rate, and dehumidification efficiency were selected as the performance indices. The results show that the minimum humidity ratio of processed compressed air could reach 0.23 g/kg under 0.71 MPa. Compressed air-drying performance could be remarkably enhanced through increasing the air pressure and liquid desiccant inlet concentration while the influence of liquid desiccant temperature is negative. Furthermore, in order to ensure high compressed air-drying performance, reduce the power consumption of the air compressor and liquid desiccant pump, and the possibility of carryover, the optimum ratio of liquid to compressed air flow rate is recommended to be around 1.5 under pressure around 0.50 MPa. Meanwhile, the energy consumption for per-gram moisture removal of a liquid-desiccant-based compressed air-drying system can reach 1.42 kJ/g lower than cooling dehumidification under 0.3 MPa, which is 16.0% lower than a compressed air-cooling dehumidification system.     

DESICCANT GRAIN APPLIED TO THE STORAGE OF SOLAR DRYING POTENTIAL

ABSTRACT

Sorption storage of solar heat using a layer of wheat as the desiccant was analyzed by means of a deep-bed drying model. Intended to be applied to solar-assisted in-storage drying of agricultural bulk materials, the probability of the persistence of unfavorable weather periods was quantified statistically for Potsdam for the month of August, as an example. Simulation results demonstrate that a relative humidity of the drying air of 65 % can be maintained day and night for weeks without combustion of fossil fuels. Using a simple strategy of control, periods with insufficient solar radiation can be bridged over. The desiccant grain is not endangered by mold growth as a matter of principle. Simple solar air heaters can be used to avoid economic losses due to overdrying and to reduce the danger of decay to a minimum even at unfavorable climatic conditions.     

Saffron Drying with a Heat Pump–Assisted Hybrid Photovoltaic–Thermal Solar Dryer

Saffron is the most expensive spice and Iran is the largest producer of this crop in the world. Saffron quality is profoundly affected by the drying method. Recent research has shown that hybrid photovoltaic–thermal solar power systems are more efficient in comparison with individual photovoltaic and thermal systems. In addition, heat pump dryers are highly energy efficient. Furthermore, they are suitable for heat-sensitive crops such as saffron. Therefore, in the present study, the performance of a hybrid photovoltaic–thermal solar dryer equipped with a heat pump system was considered for saffron drying, in order to obtain a high-quality product and reduce fossil fuel consumption. The effect of air mass flow rate at three levels (0.008, 0.012, and 0.016 kg/s), drying air temperature at three levels (40, 50, and 60°C), and two different dryer modes (with and without the heat pump unit) on the operating parameters of the dryer was investigated. The results of the investigation showed that total drying time and energy consumption decreased as air flow rate and drying air temperature increased. Applying a heat pump with the dryer led to a reduction in the drying time and energy consumption and an increase in electrical efficiency of the solar collector. The average total energy consumption was reduced by 33% when the dryer was equipped with a heat pump. Maximum values for electrical and thermal efficiency of the solar collector were found to be 10.8 and 28%, respectively. A maximum dryer efficiency of 72% and maximum specific moisture extraction rate (SMER) of 1.16 were obtained at an air flow rate of 0.016 kg/s and air temperature of 60°C when using the heat pump.     

循环转轮空调系统变工况除湿特性

转轮除湿空调系统可回收船舶余热将其作为转轮再生热源并改善舱室内空气品质,有望实现低能耗高效除湿。为此,建立了一种新型循环转轮除湿空调系统,定量研究了变工况条件下系统的除湿特性,获得了不同循环分流系数（45%～85%）、处理空气温度（28～40℃）、处理空气相对湿度（50%～85%）、再生空气温度（130～160℃）对系统除湿效果的影响。结果表明：所提出的转轮除湿空调系统相比常规海水直接冷凝除湿方式可有效提高除湿率;在相同循环分流系数下,系统的除湿率随着处理空气温湿度以及再生空气温度的升高而逐渐增大;系统的除湿率存在最优值,其对应的最佳循环分流系数为50%～75%,该系数随着处理空气温湿度的增大而减小,随着再生空气温度的升高而增大。     

Drying Kinetics of Tomato by Using Electric Resistance and Heat Pump Dryers

Drying kinetics of tomato was studied by using heat pump dryer (HPD) and electric resistance dryers with parallel and crossed airflow. The performance of both systems was evaluated and compared and the influence of temperature, air velocity, and tomato type on the drying kinetics was analyzed. The use of HPD showed to be adequate in the drying process of tomatoes, mainly in relation to the conversion rate of electric energy into thermal energy. The heat pump effective coefficient of performance (COP_HT,EF) was between 2.56 and 2.68, with an energy economy of about 40% when compared to the drying system with electric resistance. The Page model could be used to predict drying time of tomato and statistical analysis showed that the model parameters were mainly affected by drying temperature.     

热泵和除湿板结合的固体除湿新风机组特性

提出一种热泵驱动的住宅用固体除湿新风机组。该机组采用两级除湿和再生,每级由两个除湿板组成,分别位于被处理空气侧和再生空气侧,通过相互交换位置实现连续除湿。热泵系统的制冷量和排热量分别用于冷却被处理空气及加热再生空气。针对该机组建立相应数值模型并进行实验验证,模拟分析各级除湿板位置交换模式(模式1:同时交换位置;模式2:交替交换位置)、转换间隔(TI)、新风进口状态和级数对机组COP的影响。结果表明:该机组存在最优TI,模式2的最优TI是模式1的一半,风量为300 m³·h^-1 时模式1的最优TI为8 min,风量为500 m³·h^-1时模式1的最优TI为4 min;随着级数增加,机组COP增加;新风进口越干燥、温度越低,机组COP越高。在北京夏季工况和ARI夏季工况下,COP分别高于3.5和5.5。