共查询到19条相似文献,搜索用时 203 毫秒
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阐述了我国碳排放现状及节能减排的紧迫感。以传统的热风炉粮食干燥的和传统的木材蒸汽干燥为例,分析了传统干燥热效率不高的主要因素,指出排气余热回收是传统干燥作业节能减排的主要途径之一,采用普通换热器、热泵及热管换热器回收排气余热,均有明显的节能效果。采用普通换热器平均节能12.4%,采用热泵平均节能40%左右,采用热管换热器居二者之间。介绍了太阳能干燥、太阳能与热泵组合干燥、热风与真空微波组合干燥、超声波与热风干燥组合等各种低碳干燥技术。建议逐渐推广用生物质能源作为干燥的热源,有利于实现低碳干燥。 相似文献
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热泵干燥木材的技术现状与发展趋势 总被引:2,自引:0,他引:2
热泵与常规热风干燥的区别在于前者的干燥系统中空气为闭式循环,依靠制冷原理对空气降湿;后者为开式循环,依靠换气使空气降湿。对热泵干燥木材进行了节能分析,其节能率在40%~70%之间。文中介绍了热泵在木材干燥工业中的国内外应用概况,分析了热泵干燥的优点、局限性与适用范围,指出了今后热泵干燥木材的发展趋向是与常规能源联合干燥或作为二段干燥中的预干燥。同时还指出,热泵也宜推广用于干燥种子、水产品及热敏类化工原料等适于低温干燥的物料。 相似文献
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我国木材干燥技术与研究动态 总被引:1,自引:0,他引:1
阐述了我国木材干燥技术应用状况及面临的问题,介绍了我国木材干燥学术活动的情况和理论研究动态。指出以蒸汽为热源的常规干燥仍将占木材干燥的主导地位,约在80%以上;真空干燥、热泵除湿干燥、微波与高频干燥、高温干燥、加压干燥等其它干燥方法都在各自适用的范围内有一定的发展。木材的渗透性、木材干燥过程的水分迁移机理等有关木材干燥的传热传质方面的基础理论研究正在加强;高效节能的木材干燥技术是目前研究的重点课题。我国木材干燥技术正由经验型转向以干燥理论为基础的科学型方向发展。 相似文献
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污泥热泵干燥速率及能耗的实验研究 总被引:1,自引:0,他引:1
利用小型热泵干燥试验台,对污泥干燥过程含水率、空气参数(温度、相对湿度)及热泵参数(制冷工质参数、排水量、能耗等)的变化进行了试验测试,并着重对干燥速率、能量回收率及影响因素进行了分析。试验显示,依靠外热源预热后,污泥干燥过程仅依靠热泵回收的排气余热供热,干燥箱内平均温度可达63℃,最高迭71℃。干燥箱内温度的高低取决于受制冷工况影响的热泵供风温度。污泥干燥速率随空气温度升高和相对湿度的降低而增大,湿基含水率从42.6%到18.74%的平均干燥速率为0.123%/(m·min)。热泵干燥回收排气余热的节能效果显著,并随热泵排水量的增加而增大。平均能量回收率为39.1%,最大值为48.9%和最小值为23.6%,分别发生在热泵排水量最大和最小的阶段。 相似文献
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鱿鱼热泵-热风联合干燥节能研究 总被引:4,自引:0,他引:4
以热泵干燥阶段的温度、分阶段干燥的水分转换点、后期热风干燥阶段的温度为影响因素,以单位能耗除湿值(SMER)和总挥发性盐基氮值(T—VBN)两者的综合指标Y为最终评价指标进行响应面优化分析,得出了联合干燥最佳工艺参数:热泵干燥温度(X1=54.3℃)、水分转换点(X2=32.3%)和热风干燥温度(X3=43.5℃)。在最优工艺条件下比较HPD、HPD+AD、AD三种干燥方式下的样品品质和耗能,联合干燥得到的鱿鱼干品质高于热风干燥,而且降低了干燥能耗38.67%。 相似文献
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ABSTRACT Solar–;dehumidification wood drying kilns attract more and more interest due to their energy saving characteristics. However. such dryers are only available for small effective drying volume capacities. less than 30 m3, and for low drying temperature under 65 °C, for Chinese domestic products. In fact, wood drying kilns over 60 m3and high drying temperatures upto 95 °C or even higher are commonly desired from economic and process technology points o f view. For instance, if the drying temperature is below 60 °C. a long drying period will result in high operational costs and may also cause mould as well colour changes on the lumber surface. It is also known that the anti- decay ability of the seasoned lumber is lhus reduced. As such. the design of the solar–dehumidification wood drying kiln with an effective drying volume capacity of 60 m3 and a drying temperature upto 95 0C was made. Two compression processes for dehumidification and heat pump systems were adopted. The refrigerant of R1(2). which has low RODP and RGE, was utilized as the actuating medium. The values of COP. PER and SMER were 4.42. 1.19 and 3.08 kg ( H20) /( kWh) for the dehumidification system. The valucs of COP and PER were 3.05 and 0.824 for the heat pump (heat supply) system. The averaged total COP and PER over the both were 3.74 and 1.01 respectively. 相似文献
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光伏-太阳能环形热管/热泵复合系统将太阳能环形热管循环模式和太阳能热泵循环模式有机结合,两者采用相同的工质,共用一个PVT蒸发器和冷凝器。当太阳辐照强度较强,工质在PVT蒸发器中的温度高于冷凝器中的温度时,可以利用环形热管模式制热;当太阳辐照强度较弱或工质在PVT蒸发器中与冷凝器中的温差无法满足环形热管模式运行时,可以利用热泵模式制热。两种模式既能够独立运行,又可以互相切换,确保热能的稳定供应,同时能够明显降低系统耗电量。搭建了光伏-太阳能环形热管/热泵复合系统实验平台,对复合系统在环形热管模式和热泵模式独立运行时的瞬时性能和全天性能进行了实验研究。 相似文献
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设计了太阳能流化床干燥的试验装置,通过试验的方法研究了流化干燥特性和太阳能利用的效益。对冷热态,不同流量,不同物料层高等参数变化,进行了测试,对比进行了多次试验,得到了不同参数的试验结果。分析总结了各参数对物料干燥的影响,表明空气流量,料层高度和冷热态均会影响物料干燥程度,且热管传递的热量只有部分传递给了物料。应用Fluent商用计算软件,对热管换热开展了数值模拟,获得了换热效率的变化,研究结果说明数值计算与试验结果符合较好。 相似文献
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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. 相似文献
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Thin-layer drying experiments under controlled conditions were conducted for green sweet pepper in heat pump dryer at 30, 35, and 40°C and hot air dryer at 45°C with relative humidities ranging from 19 to 55%. The moisture content of sweet pepper slices reduced exponentially with drying time. As the temperature increased, the drying curve exhibited a steeper slope, thus exhibiting an increase in drying rate. Drying of green sweet pepper took place mainly under the falling-rate period. The Page equation was found to be better than the Lewis equation to describe the thin-layer drying of green sweet pepper with higher coefficient of determination and lower root mean square error. Drying in heat pump dryer at 40°C took less time with higher drying rate and specific moisture extraction rate as compared to hot air drying at 45°C due to lower relative humidity of the drying air in a heat pump dryer though the drying air temperature was less. The retention of total chlorophyll content and ascorbic acid content was observed to be more in heat pump–dried samples with higher rehydration ratios and sensory scores. The quality parameters showed a declining trend with increase in drying air temperature from 30 to 45°C. Keeping in view the energy consumption and quality attributes of dehydrated products, it is proposed to dry green sweet pepper at 35°C in heat pump dryer. 相似文献
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Effect of ambient conditions on drying of herbs in solar greenhouse dryer with integrated heat pump 总被引:1,自引:0,他引:1
Thing Chai Tham Mei Xiang Ng Shu Hui Gan Lee Suan Chua Ramlan Aziz Luqman Abdullah Chuah 《Drying Technology》2017,35(14):1721-1732
An even span solar greenhouse dryer was built and applied to dry Java tea (Orthosiphon aristatus) and Sabah snake grass (Clinacanthus nutans Lindau). Findings showed that the solar greenhouse dryer performs satisfactorily during clear weather except at nighttime and rainy day due to product rehydration which is heavily influenced by high relative humidity from ambient air. Integrating of heat pump into the solar greenhouse dryer has successfully reduced the room relative humidity by 10–15%. Also, heat pump has mitigated the product rehydration issue by maintaining room relative humidity at maximum of 65% throughout the drying period. The drying rate of Java tea was improved three to fourfold, i.e., from 0.004–0.008 to 0.018–0.025?g H2O/g DM min, whereas 10% of drying time was saved for both Java tea leaf and Sabah snake grass leaf with the assistance of heat pump system. Meanwhile, the supply of dry air from the heat pump system with a magnitude of 0.25–0.50?m/s helps in enhancing the drying rate of the herbs as well as minimizing the nonuniformity of drying temperature and relative humidity inside the solar greenhouse dryer. 相似文献
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Vasile Minea 《Drying Technology》2013,31(14):1630-1643
This article presents a 13-m3 wood dryer coupled with a 5.6-kW (compressor power input) heat pump. Drying tests with hardwood species such as yellow birch and hard maple were completed in order to determine the system's energy performance. Supplementary heating to compensate for the dryer heat losses was supplied using electrical coils or steam exchangers. The heat pump running profiles and dehumidification performance in terms of volumes removed and water extraction rates, coefficients of performance, and specific moisture extraction rates were determined for two all-electrical and two hybrid drying tests. The hardwood drying curves, share of the final moisture content, and final quality of the dried wood stacks, as well as total drying energy consumption and costs, were determined for each drying run. Finally, the total energy consumption of the drying cycles using a heat pump was compared with that of a conventional drying cycle using natural gas as a single energy source. 相似文献