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首页> 外文期刊>International Journal of Heat and Mass Transfer >Investigation of a new tube-in-tube helical flow distributor design to improve temperature stratification inside hot water storage tanks operated with coiled-tube heat exchangers
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Investigation of a new tube-in-tube helical flow distributor design to improve temperature stratification inside hot water storage tanks operated with coiled-tube heat exchangers

机译：研究一种新的管内螺旋流分配器设计，以改善通过盘管式换热器运行的热水储罐内的温度分层

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摘要

Steady and unsteady heat transfer process and the developed flow and temperature field inside hot water storage tanks have been studied with a helical tube-in-tube flow distributor design. The studied flow distributor consists of two helically coiled pipes. The inner pipe is a common helically coiled tube heat exchanger and the outer pipe is a helically coiled flow distributor which separates the hot water from the significantly colder bulk water of the tank to decrease the entrainment effect induced by natural convection. The flow distributor drives the heated water to a helical flow path along the tube axis which induces additional secondary flow in planes normal to the main flow direction over the outer surface of the inner coiled tube. Different heat exchanger side flow rates, inlet temperatures and two gap size between the outer wall of the helical tube and the flow distributor have been investigated to describe the impact of the modification of these parameters for the developed velocity and temperature field. Comparison of the flow and temperature fields of hot water storage tank with common helical tube and the tube-in-tube flow distributor configuration are discussed. Numerical calculations have been carried out to examine different flow and temperature fields in laminar flow regimes. Calculated results of the inner side heat transfer intensity (Nu) have been compared to existing empirical formulas to test the validity of the numerical results in case of common helical tube heat exchanger. The proposed helical flow distributor ensures a highly stratified temperature field of storage tanks operating with helically coiled heat exchangers. In addition to this the suggested flow distributor geometry makes it possible to apply different heat transfer enhancement tools like spiral tape inserts, different kind of corrugations further improve if it is possible the poor outer side heat transfer rate of common helically coiled tube heat exchangers.
机译：采用螺旋管对流分配器设计研究了稳态和不稳定的传热过程以及热水储罐内部发达的流场和温度场。所研究的流量分配器由两个螺旋盘管组成。内管是普通的螺旋盘管热交换器，而外管是螺旋盘管流量分配器，它将热水与水箱中明显较冷的散装水分开，以减少自然对流引起的夹带作用。流量分配器将加热后的水沿着管子轴线驱动到一个螺旋形的流动路径，从而在垂直于主流动方向的平面内的内部螺旋管的外表面上引起额外的二次流动。已经研究了不同的热交换器侧流率，入口温度以及螺旋管的外壁和流量分配器之间的两个间隙尺寸，以描述修改这些参数对发达的速度和温度场的影响。讨论了具有普通螺旋管的热水储罐的流场和温度场的比较，以及管中管式流量分配器的配置。已经进行了数值计算以检查层流状态下的不同流场和温度场。已将内侧传热强度（Nu）的计算结果与现有经验公式进行了比较，以检验在普通螺旋管式换热器情况下数值结果的有效性。所提出的螺旋流分配器确保了采用螺旋盘绕热交换器的储罐的高度分层温度场。除此之外，建议的流量分配器几何形状使得可以应用不同的传热增强工具，例如螺旋带插入件，如果可能的话，普通螺旋形盘管热交换器的较差的外侧传热率会进一步改善不同种类的波纹。

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