Abstract
In this paper, three-dimensional numerical simulation was taken on a Linear Fresnel solar receiver tube using molten salt as heat transfer fluid (HTF), in which the porous media was filled to enhance the heat transfer efficiency. The simulation was to analyze the influence of the different conditions (filling rate, porosity and thermal conductivity) on heat transfer effect and wall temperature difference. The results revealed that the Nu (Nusselt number) increased firstly and then decreased with the increasing filling rate in both center filling and annular filling types. The optimal thermal performance were obtained when filling rate were 0.8 and 0.2 in center filling and annular filling, respectively. The Nu were about 1.7 and 1.5 times as the clear receiver. The circumferential temperature difference decreased firstly and then increased with filling rate increasing in both center filling and annular filling types. The lowest circumferential temperature differences were achieved at the filling rate 0.8 and 0.4 in center filling and annular filling types, and temperature difference decreased 15.88°C and 22°C compared with clear receiver, respectively. The Nu and PEC both decreased with porosity increasing. However, the thermal conductivity of porous media had little influence to the Nu and circumferential wall temperature.
Highlights
The solar energy thermal power generation is attracting more and more attention due to its advantage of low cost and clean characteristics, under the background of increasingly serious global environmental pollution and energy issues[1]
The maximum error of calculated f was less than 10% compared to the Filonenko correlation. These results indicated that the numerical simulation was effective to analyze the heat transfer characteristics in the molten salt-type receiver tube by using this modal and grid system
This study analyzed the characteristics of heat transfer enhancement and wall temperature in the solar receiver tube by inserting porous media with different conditions in Linear Fresnel receiver tube using molten salt as heat transfer fluid (HTF)
Summary
The solar energy thermal power generation is attracting more and more attention due to its advantage of low cost and clean characteristics, under the background of increasingly serious global environmental pollution and energy issues[1]. The non-uniform heat flux distribution can cause the large temperature field in the receiver tube, even damage of component and decrease of working life. Compared with trough-based receiver, traditional Linear Fresnel Reflector, with no rotating joint in high temperature parts, is of low cost and high safety property [2]. Because the receiver tube is non-uniformed distributed on the surface, the flow heat transfer characteristics is to be studied in order to ensure the safety of practical operation. The following assumptions were used to the calculations: (1) Steady flow; (2) Neglecting the natural convection and radiation heat transfer in the tube and heat loss outside the tube; (3) The porous media is uniform and isotropic; (4) The porous framework and fluid satisfy local heat balance; (5) Neglecting thermal contact resistance between receiver tube and porous media in out-filling situation
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