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应用于食品干燥的热泵性能实验研究 总被引:5,自引:1,他引:4
在热泵干燥系统中,热泵性能对干燥能耗和干燥食品品性有显著影响。热泵干燥系统的干燥温度是干燥过程的关键参数之一。本文对比测试各种升温方式的基础上,主宰了带辅助蒸发器在热泵干燥机组不仅升温速度快,能耗低,除湿效果显著,而且可以满足不同食品干燥要求。 相似文献
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复合相变蓄热器在空调系统冷凝热回收中的应用 总被引:1,自引:0,他引:1
介绍了一种复合相变蓄热器的工作原理和结构形式,提出了应用中所存在的问题.利用相变材料放出潜热提高供水温度,在不需用热水时,压缩机不必停机从而加热融化相变材料以储存热量.采用相变材料回收空调冷凝热,既具有节能又具有环保的特点. 相似文献
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为探究相变温度对相变材料回填地埋管换热器传热性能的影响,建立管内流体换热、回填区域相变换热及土壤换热的三维耦合传热数值模型,利用焓-多孔介质模型对相变区域相变问题进行处理,研究夏季间歇运行工况下不同相变温度回填材料对埋管换热器传热性能的影响。结果表明:添加PCM,可有效提高换热量,短期内缓解埋管周围热积聚,利用相变温度18℃的PCM回填,单位井深换热量至少比普通材料回填提高49.54%;在间歇运行初期,换热量随相变温度的升高逐渐减小,低相变温度的PCM可明显改善埋管换热量,但随着时间的进行,较高相变温度PCM回填对换热器换热量的改善效果优于前期低相变温度。此外,在运行期间,不同相变温度的PCM表现出不同的熔化、凝固特性,当PCM的熔化、凝固过程交替进行时,可减缓土壤温度在运行期间内波动幅度。 相似文献
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介绍了太阳能与热泵联合干燥系统的组成与工作原理.通过理论分析与实验研究探讨了太阳能与热泵联合运行的优化匹配,当太阳能供热量能满足木材干燥所需热量时,由太阳能系统供热;否则由太阳能与热采联合供热;阴雨天和夜间由热泵供热.当太阳能送风温度低,但高于环境温度时,低温太阳能向热泵送风,可以提高热泵的供热系数和供热量.对应于一定的环境温度,太阳能向热泵送风有一个相匹配的最低温差.例如当环境温度为24℃时,通过理论和实验求得太阳能向热泵送风与环境温度间的最低送风温差分别为4℃和6℃. 相似文献
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正挪威东南部海港城市德拉门盛行安装氨热泵机组以从水或空气中获取热量,供热效果良好。采用热泵提供的热量远远超出机组消耗的能量,大大减少了对矿物燃料的依赖及对其他可再生能源的需求。为确保达到理想效果,德拉门市制定了增加容量的目标——(1)要求热泵机组的供水温度达到90oC。(2) 相似文献
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通过测试一间有一面是相变材料另一面是保温材料的新型动态Trombe墙体的房屋全尺寸模型,对该墙体的热性能进行实验研究。以墙体和房间的空气温度以及通过墙体的热流量和气流速率来评估其性能。结果表明:在相变过程中,温度变化相对平缓;墙体从玻璃获得的热量占其获得总热量的26.2%,且利用其储存的90.1%的热量对房间进行加热;在相变材料放热期间,该墙体可降低室内温度的分层且房间中部的温度至少比室外温度高3.2℃。 相似文献
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Thermal performance parameters for a solar-assisted heat pump (SAHP) drying system with underground thermal energy storage (TES) tank and heat recovery unit (HRU) are investigated in this study. The SAHP drying system is made up of a drying unit, a heat pump, flat plate solar collectors, an underground TES tank, and HRU. An analytical model is developed to obtain the performance parameters of the drying system by using the solution of heat transfer problem around the TES tank and energy expressions for other components of the drying system. These parameters are coefficient of performances for the heat pump (COP) and system (COPs), specific moisture evaporation rate (SMER), temperature of water in the TES tank, and energy fractions for energy charging and extraction from the system. A MATLAB program has been prepared using the expressions for the drying system. The obtained results for COP, COPs, and SMER are 5.55, 5.28, and 9.25, respectively, by using wheat mass flow rate of 100 kg h−1, Carnot efficiency of 40%, collector area of 100 m2, and TES tank volume of 300 m3 when the system attains periodic operation duration in fifth year onwards for 10 years of operation. Annual energy saving is 21.4% in comparison with the same system without using HRU for the same input data. 相似文献
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Drying is one of the most energy intensive and common operations in the chemical and process industries. Scope for energy recovery is substantial, particularly from the latent heat of the exhaust moist air. Using real operating data from a major Swedish mill, optimal energy conservation strategies were investigated using different heat pump systems in paper drying. Simulation results are compared for compressor-driven and absorption heat pump systems. An absorption heat transformer was also investigated. A CH3OH–LiBr double-lift cycle would have a low COP value due to the low temperature of the moist air stream and the restricted temperature of the cooling water available. A total of 30 MW thermal equivalent is currently needed in the mill at a temperature of 75°C for mixing-pits, district heating and a log store. Exhaust humid air at a temperature of 54°C from only three of the paper machines was used in this study. SHPUMP simulations revealed that installing a mechanical heat pump unit using HFC 134a would result in a recovery of 22 MW due to the temperature level of this application. On the other hand, 12 MW can be recovered with an absorption heat pump. To optimize the operating conditions, H2O–NaOH was selected as the best of three based on exergy index criteria. Assuming a steam cost of 22 $/MW h and an electricity cost of 32 $/MW h, the pay-off periods would be 3·3 and 2·9 years for compressor-driven and absorption heat pump alternatives, respectively. © 1997 by John Wiley & Sons, Ltd. 相似文献
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为缩短枸杞干燥时间,提高干制枸杞的质量,减少能源消耗,本文提出了一种新型太阳能–空气源热泵联合干燥系统。该系统主要由太阳能集热器和空气源热泵机组等设备组成,可以实现太阳能单独干燥、热泵单独干燥和太阳能–空气源热泵联合干燥三种工作模式。本文根据枸杞的干燥特性,分段设定最佳的干燥温度,进行了热泵单独运行和太阳能–热泵联合运行两种工作模式下干燥枸杞的对比实验。结果表明,干燥50 kg枸杞,太阳能–热泵联合运行比热泵单独运行节省了2.9 kW?h电能,若同时除去系统本身的耗能,节省的电能占热泵单独运行耗电量的29.5%。同时,与太阳能单独干燥相比,太阳能–热泵联合干燥具有较高的除湿能耗比,两者最大差值为0.71 kg/(kW?h)。本文提出的太阳能–热泵联合干燥系统具有提高干燥产品的品质、缩短干燥时间和节约干燥成本等优点,适宜推广。 相似文献
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空气回热闭式热泵干燥系统实验研究 总被引:7,自引:0,他引:7
空气闭式热泵干燥装置和加装空气回热器的空气闭式热泵干燥装置的对比试验表明,后者比前者除湿能耗比SPC在某些工况下降低达20%。对两者的循环作了理论分析。 相似文献
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介绍了太阳能.热泵联合干燥的目的、意义、设备组成与工作原理,列出了联合干燥设备的主要参数与性能测试数据。绘出了太阳能干燥与联合干燥的工艺曲线。将太阳能-热泵联合干燥与常规蒸汽干燥(又称热风干燥)进行了经济分析对比,联合干燥的节能率在70%左右。 相似文献
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