冷风机蒸发器的设计计算方法

冷风机蒸发器是冷库中常用的制冷设备,设计计算中要确定蒸发器的结构、运行参数以及风机的选型。冷风机的蒸发器一般在结霜工况下运行。由于翅片表面结霜,传热情况复杂,使设计计算要考虑的因素较多,而且相互耦合。本文基于下列几点考虑,进行冷风机蒸发器的设计。     

蒸喷制冷机遥测、遥控、自动调整装置

上棉十九厂在武汉冷冻机厂协作下,试制安装成功了150万大卡蒸喷制冷机遥测、遥控、自动调整装置,使用以来收到了良好的效果。 这套装置可用于下列几个方面:1.温度遥测:主要测定冷凝器、蒸发器分仓温度及五台水泵进水温度。2.压力遥测:主要测定三组主喷嘴及两个辅助喷嘴前的蒸汽压力。3.真空度遥测:主要测定蒸发器、冷凝器分仓及辅助系统的真空度。4.水池水位的遥测和自控:主要     

CFD预测风机摆设形式对冷库的影响

为保证货品贮藏品质,本试验利用计算流体力学技术,三维模拟并分析3种不同风机摆设形式(主流面对式、主流背对式、主流接力式)对冷库运行时气流场和温度场的影响。结果表明,冷风机在3种不同摆设方式下,冷库内温度场达到稳定的时间分别为50,45,60min,并结合数值模拟得出的3种气流分布,提出大型冷库较理想的风机摆设方式的建议,即为方案二的风机背对吹风式。     

如何解决“熊猫”单台型制冷机的自身矛盾

恒温恒湿机制冷部分有两种作用:一是通过制冷机的热交换,使实验室内空气中的热量传递给冷凝物质,使实验室温度下降;二是制冷机从蒸发器上流过的制冷剂温度远远低于空气的露点温度,迫使空气中的含水以露点的形式析出,使实验室空气的湿度下降。恒温恒湿机加湿器也有两种作用:一是热蒸汽扩散到空气中增加实验室空气的含湿量;二是热蒸汽的热量传递给空气而使实验室的温度上升。     

一起空冷风机变频器跳闸原因分析及控制措施

随着发电厂对空冷风机系统整体水平的要求越来越高,风机变频器安全运行尤为重要。文章通过时一起空冷高频变频器跳闸原因进行分析,更好的提出故障处理的方法。     

焓差法试验室制冷系统优化设计和试验研究

焓差法试验在采用直接蒸发冷却式变风量空调系统.该系统将直接蒸发冷却式变频制冷系统的蒸发器,应用于变风量空调系统的空气处理箱,取代了水为载冷剂的二次能耗环节,制冷机直接蒸发对变风量空气进行热湿处理,最终实现制冷系统与变风量空调系统的有机结合、协调控制和稳定运行.……     

焓差法试验室制冷系统优化设计和试验研究

焓差法试验在采用直接蒸发冷却式变风量空调系统.该系统将直接蒸发冷却式变频制冷系统的蒸发器,应用于变风量空调系统的空气处理箱,取代了水为载冷剂的二次能耗环节,制冷机直接蒸发对变风量空气进行热湿处理,最终实现制冷系统与变风量空调系统的有机结合、协调控制和稳定运行.……     

蒸汽喷射制冷机的特性

蒸汽喷射制冷机与压缩式制冷机都是利用液体在低压时蒸发吸热的相变过程来制冷的,它们都有蒸发器和冷凝器,不同的是蒸     

堆垛方式及送风功率对冷库制冷效果的影响

目的：合理规划移动冷库内货物堆放方式，合理设计风机的送风功率，降低冷库能耗、提高经济效益。方法：以某冷库为研究对象，建立了冷库的三维物理模型和k-ε数学模型，采用Fluent软件对冷库内货物不同堆垛方式、不同送风功率下的温度场进行模拟。结果：在相同工况下，货物横置时平均库温为2.014 ℃，货物竖置时平均库温为2.006 ℃，均达到设计要求，且货框横置可以堆放162个，竖置可以堆放180个，竖置堆放可以让空间利用率最大化。在不同送风功率，运行15 min后，功率100%时平均库温为2.006 ℃；功率70%时平均库温为2.129 ℃；功率50%时平均库温为2.410 ℃，在3种不同风扇功率情况下冷库温度都达到了设计要求。实际选型功率过大，50%功率即可满足冷库满载运行的设计要求。结论：竖置的堆垛方式可以提高冷库的空间利用率，冷风机选型可以降低运行成本，提高经济效益。     

纺织实验室的空调与制冷(三) 第二部分 空调制冷

制冷装置基本工作原理空调制冷的目的是使恒温恒湿室内温度低于环境温度,并使之维持特定温度。在制冷装置从低温处吸取热量后到高温处放出热量,主要是依靠在装置中循环的制冷剂液体变成蒸汽时吸收大量热量来实现的。纺织实验室一般采用活塞式压缩制冷机,主要由压缩机、蒸发器、冷凝器和膨胀     

Studies on aeration with refrigerated air—III. Chilling of wheat with a modified chilling unit

Two trials on the cooling of grain with refrigerated air are described. The chilling unit had the fan positioned after the evaporator to lower relative humidity of the cooled air entering the grain. A bin containing 699 metric tonnes of wheat was cooled in summer from 30–37°C to 18–19°C in 160 hr at an energy consumption of 4·6 kW/hr/tonne. The second bin containing 863 tonnes of wheat was cooled in winter from temperatures of up to 42°C to 15–21·5°C in 236 hr at an energy consumption of 4·7 kW/hr/tonne. It was shown that grain was not moistened as a result of cooling. The importance of controlling both air temperature and humidity in the cooling system are discussed and this method is compared with aeration using ambient air.     

Evaluating two different evaporative cooling management systems for dairy cows in a hot, dry climate.

Milk production, rectal temperature, live weight gain, reproductive performance, and weather data were obtained on 150 Holstein cows managed under two cooling systems on a large dairy farm in Saudi Arabia during the summer months. Cows were paired at the onset of the trial according to days postpartum, lactation number, and current milk production. Females were then allocated either to a system that forced air, precooled by evaporative cooling, over the cows or to a system that alternately showered a fine mist onto the surface of the cows and then forced air at ambient temperature over them. The cows receiving evaporative cooling and those with spray and fan cooling were on sand and on slatted concrete floor, respectively, during the periods of cooling. The onset of estrus was observed during the night when the cows preferred the unshaded corral. For the 120-d trial period, 84% (62 of 75) of the cows receiving evaporative cooling and 60% (44 of 75) of the cows receiving spray and fan cooling became pregnant. In the evaporative cooling system, the pregnancy rate per insemination was 35.2% (179 inseminations) versus 23.2% (194 inseminations) for spray and fan cooling. The mean postpartum interval to pregnancy was 117.6 d for the evaporative cooling cows and 146.7 d for spray and fan cooling cows. The evaporative cooling system, with its open shades and sand bedding, enhanced reproductive performance and milk production compared with that of cows cooled with a spray and fan system with slatted flooring in this hot climate.     

制冷机组冷却水温度控制系统的改进

在不同负荷、不同季节和不同环境温度下,制冷机组的冷却塔风机恒速运行无法使冷却水温度控制在需要范围内。采用变频调速技术对冷却水控制系统进行了改进,选用热敏元件作为温度传感器在线检测冷却水温度,通过水温信号控制变频器的输出频率,调节风机转速和冷却塔散热量,从而将冷却水温度控制在允许范围内。     

平房仓不同风机降温通风对比试验

分别选用两种风机,对高大平房仓进行降温通风对比试验,将两种不同风机降温变化情况进行比较。结果表明,选用轴流风机降温通风,具有耗电低、能耗少、水分损耗低、降温均匀和操作简便等特点,适用于高大平房仓早期降温通风;选用离心风机降温通风,具有降温迅速、操作简便等特点,适用于高大平房仓紧急情况下的降温降水通风。     

Energy consumption, rate of cooling and weight loss in beef chilling in UK slaughter houses

The energy consumption, cooling rate and weight loss were measured in 14 beef chillers in commercial use. Beef sides were removed from the chillers between 24 and 48 h after loading but a deep leg temperature of 7°C or less on unloading was achieved in only 4 of the chillers. The weight loss was between 1·1 and 2% after 24 h and between 1·5 and 2·3% after 48 h and its value was 20 times the cost of the energy used.

Energy consumption was related to ambient temperature and evaporator fan energy. Mean annual UK specific energy consumption was 116 kJ/kg and the estimated total UK consumption is 113 TJ. A target consumption of 70 kJ/kg is possible with existing technology and if achieved by all UK plants would save 42 TJ per year and increase profits in the industry by 26%.     

Modelling Cooling of Packaged Fruit Using 3D Shape Models

This study presents a novel methodology to model the cooling processes of horticultural produce using realistic product shapes rather than commonly used simplified 3D shapes, such as spheres. Variable 3D apple and pear models were created by means of a validated geometric model generator based on X-ray computed tomography images. The fruit were randomly stacked into a geometrical model of a corrugated fibreboard box using the Discrete Element Method. A forced-air cooling process was simulated for three such apple filling patterns using CFD and the results were compared to those obtained with fruit represented by equivalent spheres. No significant difference in average aerodynamic resistance between the real apple shape and its spherical representation was found. The main contributor to the overall pressure drop was the package design rather than product shape. However, large differences in local air velocity and convective heat transfer coefficients were found between the two representations. The degree of cooling uniformity between individual fruit was overestimated when using simplified product shapes: real apple fruit shapes cooled less uniform. This difference between real and simplified product shapes was even larger for a box filled with pear fruit that are more different from a spherical shape. These results demonstrate that improved computer-aided design approaches help in simulating more accurate convective cooling processes. In a next step, such simulations will be used for multi-objective optimization of packaging in terms of cold chain efficiency and cooling uniformity.     

降温方法对不同成熟度鸭梨冰温贮藏中有机酸含量的影响

为了研究不同处理方式对鸭梨中有机酸含量的影响,现采用急速降温和缓慢降温方法对早、中、晚三种不同成熟度的鸭梨进行处理并于冰温下贮藏,在贮藏期间使用高效液相色谱法(high performance liquid chromatography, HPLC)对鸭梨果肉、果皮中的有机酸含量进行测定。研究结果表明：鸭梨果实中主要的有机酸为苹果酸、莽草酸、柠檬酸、草酸,其中有机酸含量主要表现为苹果酸和莽草酸含量最高,柠檬酸含量次之,草酸含量最少。三种采收成熟度鸭梨中四种有机酸含量在冰温贮藏期间总体呈现逐渐降低的趋势。缓慢降温处理后的早、中期采收的鸭梨中主要有机酸含量较急速降温处理高,且与早、晚期采收的鸭梨相比，中期采收的鸭梨中有机酸含量适中。因此,缓慢降温处理结合中期采收的鸭梨能够更好的保持果实中的有机酸含量,从而提高鸭梨品质。     

A Cooling System with Water Recycle for Blanched Vegetables

A water conserving cooling system with water recycle for blanched vegetables was designed to complement a previously developed water recycling blancher. The two stage cooler consisted of an evaporative cooling section with forced air and water sprays and a flume cooler with water, which was both refrigerated and recycled. A pilot scale blanching and cooling system was constructed, and broccoli spears were processed. The cooling system was effective at lowering the product temperature rapidly while maintaining the quality of the product at a high level as determined by ascorbic acid concentration, percentage of total solids, percentage of retained chlorophyll, and microbial counts.     

混合油负压蒸发工艺探讨

浸出毛油的品质随着加热温度的升高和时间的延长显著降低,混合油负压蒸发工艺是使一蒸、二蒸、汽提在负压状态下操作,同时,利用蒸脱机的二次蒸汽作为一蒸的热量来源.一方面在负压状态下可以减少油脂与空气中氧分子的接触;另一方面可以降低混合油中溶剂的沸点,以达到降低蒸发温度的目的.可以节约能源、节省钢材、提高毛油质量.在负压蒸发工艺设计中要注意合理配备冷凝面积,降低冷却循环水的温度,防止蒸脱机气相产生正压,控制蒸脱机二次蒸汽量,合理操作第二蒸发器,使用湿式粕末捕集器,加大第一蒸发器面积,列管适当加长加大,并选用不锈钢材质,选择蒸汽喷射泵,合理选择真空度,搞好余热利用和尾气回收.     

用管式急冷加工机生产片状酥皮玛琪琳

酥皮玛琪琳要具备塑性和稳固性。用急冷管式冷冻加工机可以灵活改变工艺流程。油脂深加工过程中，冷冻对结晶有决定性的影响。不同配方的产品要有不同的生产工艺和熟成条件。