共查询到20条相似文献,搜索用时 203 毫秒
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结垢是影响城市原生污水换热器热工性能的主要原因.以壳管式污水换热器为例,在分析了污垢对换热器性能影响的基础之上,提出了换热器由于传热温差和流动阻力引起的不可逆有效能损失的计算方法,以及污水换热器不可避免(火用)损失的定义及计算方法.分析结果为污水换热器的工程应用和科学研究提供了理论基础. 相似文献
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基于计算流体力学方法对板壳式换热器内部流场进行模拟,建立了板壳式换热器流动及换热计算的模型,模拟了换热器内部流动和换热情况,分析了流道内温度场和压力场及流线的分布情况,对流体的流动和传热进行了详细的描述,分析了换热器内流体流动和传热特性,对实际工程具有一定的指导意义。 相似文献
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A mathematical model is developed to study flow characteristics in non-adiabatic capillary tubes. The theoretical model is based on conservation of mass, energy and momentum of fluids in the capillary tube and suction line. The mathematical model is categorized into three different cases, depending on the position of the heat exchange process. The first case is considered when the heat exchange process starts in the single-phase flow region, the second case is determined when the heat exchange process starts at the end of the single-phase flow region, and the last case is considered when the heat exchange process takes place in the two-phase flow region. A set of differential equations is solved by the explicit method of finite-difference scheme. The model is validated by comparing with the experimental data obtained from previous works. The results obtained from the present model show reasonable agreement with the experimental data. The present non-adiabatic capillary tube model can be used to integrate with system models working with alternative refrigerants for design and optimization. 相似文献
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本文概述了转子组合式强化传热装置的强化传热和自清洁原理。分别通过建立光管及内置多个转子换热管的三维流动模型,对换热管内流场、温度场、压力场以及换热过程进行了模拟,得到了管内流体的流动特性和传热特性。对比模拟结果表明,内置转子换热管管内的三维流动比较复杂,转子与管壁之间缝隙内的流体有着明显的环绕流动,切向速度和径向速度也增大到一定范围,转子旋转半径内的流体整体呈螺旋流动。总的来说,内置转子的换热管内较光管有较强的湍流度,尤其是近壁区域,因此强化了管内的对流换热,传热系数显著提高,从而验证了转子具有强化传热和自清洁的双重功能。 相似文献
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根据螺旋槽管换热器结构特点及传热特性,建立了以水为工质的换热器流动与传热的三维几何模型。运用有限元分析软件ANSYS模拟出换热器在换热过程中速度场与温度场的状况,分别得到了螺旋槽管内壁与外壁的对流换热系数。结果表明:槽深越大,随着Re增大,换热性能越好;当Re较小时,螺距越大,换热效果降低。其与该类光管换热器相比,得出螺旋槽管的换热系数是光管的2.5倍左右,强化了传热,为此产品的进一步理论研究和推广应用提供了依据。 相似文献
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《Applied Thermal Engineering》2014,62(2):845-849
The use of thermal processes for water purification is a good alternative to reduce primary energy consumption. The efficiency in heat exchange process by falling film plays a very important role in the performance of a heat pump. The objective of this paper is to evaluate the efficiency of heat transfer on a tube bank, of a heat transformer designed for water purification with LiBr–H2O as absorbent mixture, by digital image processing. To analyze the wetting area and falling film behavior of the mixture on a bank of sixteen horizontal tubes, of 1.22 cm outer diameter and 30 cm in length, experimental tests were performed. The results show the distribution of absorbent mixture, along the tubes of the bank, with 0 and 5° inclination respect to the horizontal, and different mass flow rates per unit length (0.006–0.034 kg/m s). The film thickness of LiBr–H2O was determined by the digital image processing, obtaining an average value of 0.033 cm. The most regular fall of mixture, through the tubes of the bank, was obtained with the flow of 0.025 kg/m s. This mass flow was the one which gave the best results of efficiency of heat transfer, with values between 80 and 98%. 相似文献
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自激振荡脉冲射流强化换热实验研究 总被引:3,自引:1,他引:3
对自激振荡射流强化换热的机理进行了初步探讨,并对有无共振腔时的换热情况进行了对比实验。实验中发现,由Helmholtz共振腔产生的自激振荡脉冲射流增强了管内流体的掺混,破坏了边界层,从而达到了强化换热的目的。实验中还发现,当共振腔两端的压差增大时,将产生更为强烈的脉动流,明显地提高流体的紊流程度,从而强化了管内流动换热。 相似文献