Numerical prediction of the stratification performance in domestic hot water storage tanks
Numerical prediction of the stratification performance in domestic hot water storage tanks
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DOI：
10.1016/j.renene.2020.03.090
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发表时间：
2020-07
期刊：
影响因子：
8.7
通讯作者：
Yogender Pal Chandra;T. Matuška
中科院分区：
文献类型：
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作者：
Yogender Pal Chandra;T. Matuška
高效的存储可以保留热分层并提高放电性能。热水和冷水之间的湍流混合是分层破坏的主要来源。本文根据温度分布、MIX 数和理查森数实现了湍流缺失的量化。评估的参数包括流量、ΔT 和扩散器设计，从此建立了每个参数之间的直接相互依赖性。为了找到放电模式下的最佳工作条件，开发了各种 CFD 模型并在试验台上进行了实验验证。数值结果证明，通过适当选择进口装置可以优化罐体工况。例如，开槽式入口装置即使在湍流流入和低ΔT等不利条件下也能保持最大分层。穿孔和简单的入口装置仅在200升/小时的低流速下才能提供最佳排放效率，并且对ΔT的依赖性不显着。然而，随着流量增加，ΔT依赖性增加。考虑到开槽入口装置和降低ΔT的复合优势，得出的结论是，开槽入口装置在高流量和低ΔT以及高流量和高ΔT这两种不利条件下都提供了相对更好的热性能，但是，在低流量和低ΔT以及低流量和高ΔT下，未能超越其他入口装置。这些研究结果可以作为优化储罐设计的指南，更具体地说，是基于入口设备与加热系统集成的设计，因为热分层和加热系统的性能系数（例如热泵）具有内在的相关性。热泵是高流量和低ΔT设备，而太阳能系统是低流量和高ΔT设备，因此，针对特定运行条件准确选择入口设备至关重要。
An efficient storage retains thermal stratification and improves the discharging performance. Turbulent mixing between hot and cold water is the prime source of stratification destruction. In this paper quantification of turbulent missing was achieved on the basis of temperature profile, MIX number, and Richardson number. The evaluated parameters include flow rate,ΔT, and diffuser design, henceforth a direct interdependence between each was thus established. Various CFD models were developed and experimentally validated on the test rig in order to find the optimal working conditions in discharge mode. The results proved numerically that the tank working conditions can be optimized by proper selection of inlet device. For instance, slotted type inlet device sustained maximum stratification even in as adverse a condition as of turbulent inflow & lowΔT.Perforated and simple inlet devices were capable of delivering best discharge efficiency only at low flow rate of 200 l/h and were showing insignificant dependency onΔT. However, as flow rate is increased,ΔTdependency increased. Seeing the compounded benefits of slotted inlet devices and decreasedΔT, it was concluded that slotted inlet device delivered comparatively better thermal performance at both adverse conditions i.e. high flow & lowΔTand high flow & highΔT, however, failed to outshine the rest of the inlet devices at low flow rate & lowΔT, and low flow rate & highΔT. These research findings can serve as guidelines to optimize the storage tank design – more specifically, inlet device based design integrated with heating system, as thermal stratification and COP of heating system – heat pumps, for example, are inherently correlated. Heat pumps are high flow rate and lowΔTdevices, while, solar systems are low flow rate and highΔTdevices, Thus, opting for accurate choice of inlet device for a particular operating condition is critical.