Spiral Plate Heat Exchanger Of Honeycomb Type

A spiral plate heat exchanger of honeycomb type was developed by the author of this dissertation. This kind of heat exchanger is applicable to high pressure and has compact structure, low metal consumption, and high heat exchanger effectiveness. The construction features, design method, manufacturing process, heat transfer property and pressure drop, structural strength of the heat exchanger were studied comprehensively. The main research work and result are summarized as follows:(1) A novel heat exchanger was developed in this paper, which integrates the advantage and eliminates the disadvantage of the plate type heat exchanger, the plate-fin heat exchanger and the spiral plate heat exchanger. It improved the general spiral heat exchanger by using 1mm in thickness embossed stainless steel plate to replace the thick ferrite steel spiral plate. The distance between the adjacent plates is equal to the depth of the dimple, therefore, the plate contact each other tightly through the pressed embossing bulbs, the heat exchanger synchronously has the spiral plate heat exchanger-structure in macro view and the honeycomb structure in the view of heat exchanger face. Through producing the first spiral plate heat exchanger of honeycomb type, the related technology for designing and manufacturing of the novel heat exchanger was proposed.The novel heat exchanger has the following advantages. Firstly, it is high pressure resistant and instability resistant because of compressive cylindrical macro-structure and compact dimple micro-structure. Secondly, it has large flow velocity,low resistance and high heat exchanger effectiveness. As the result of homogeneous distribution of vast dimples, the heat transfer area is markedly increased and stagnation regions are eliminated. Finally, reaching the same heat exchanger area, it has simple manufacturing technology with low cost because of compact structure, saving in space and material, light in weight, automatic processing dimple plate without welding.(2) A calculation method is presented in this thesis, which is adoption of hydromechanics calculation software for estimation, for the calculation of heat transfer coefficient and flow resistance of spiral heat exchanger with compact dimple. Because of the periodic micro-structure of the heat exchanger, the flow state and heat transfer will become stable after several periodic channel. Thus, it can be studied by using the periodic flow calculating function of the software Fluent for heat transfer calculation. And two kinds of experiments verified its feasibility supporting as an effective method for heat-transfer surface design calculation. As the frustum dimple structure example, the factors of heat transfer and flow resistance are investigated, which include distribution of dimple, size of dimple, curvature of the flow passage, conicity of dimple, structure of outside concave pit, and so on. It can be investigated by the similar method for any other structure, including rectangle and roundel, with periodic structure. This method also provides effective means for evaluating dimple structure coefficient and optimizing the structure of dimple.(3) By studying the structural strength of dimple spiral plate, the complex stressed structure can be simplified as an analyzable mechanical model. And then, two kinds of design method are proposed for calculating the structural strength of dimple spiral plate in this paper. The first one is an engineering algorithm based on most conservative plate theory. The second one is an advance and accurate algorithm based on ultimate load, with which the shape and structure of the dimple were taken into account. Both are mutually supplemented, if must be cautions to select for application based on the adapted condition of the algorithm.(4) The destructive mechanism of the dimple plate is studied in this paper. It was found that the vulnerability is the connection of the plate and the concave pit for all the dimple structures including frustum, rectangle and roundel. And the upper plate is the vulnerability at high pressure. Therefore, it is sufficient for the safety of dimple plate to analyze the ultimate load of the upper plate. The ultimate load is approximately linear to the square of the thickness of the plate. This conforms to the conclusion of Appendix 17 of ASMEâ…§-1. The dimple spiral plate has high structural strength. Therefore, the thickness of the plate is generally recommended as 0.8-1.0 mm.