Research On Heat Transfer Process Of Coil-wound Heat Exchanger

This paper studies for coil- wound heat exchanger technology, which the main contents include: calculation of heat transfer process of a series of coil- wound heat exchangers, examples of relevant parameters change under analysis, the development of MCHE software and the numerical simulation of fluid flow and heat transfer by changing the relevant influential parameters.This paper studies a series of the coil-wound heat exchangers including single-stream and dual-stream. Calculation of heat transfer process of a series of coil-wound heat exchangers also includes: A new design and calculation methods are proposed, and are applied to the series coil-wound heat exchanger technology; A new arrangement and a allocation method of coil-wound pipes are used to establish the initial geometric model of bundles.In the example analysis, under the same conditions, influence of change of these parameters each on heat efficiency is researched. Velocity v, clearance ratio c?/g? and wall thickness δ are included in these parameters. Results show that: By appropriately raising the flow velocity as well decreasing clearance ratio, the overall heat transfer coefficient can be increased, and heat transfer can be enhanced; meanwhile, the length of coil-wound pipes can be decreased, then the effective height of coil- wound heat exchanger can be reduced; Nevertheless under the condition of clearance ratio functioning, the impact factor of coil tube’s Wall thickness on heat transfer effect is not much; Moreover, the different methods for distributing wound pipe will have different effects on coil-wound heat exchanger’s total heat transfer coefficient and total heat exchanger area.In order to improve coil-wound heat exchanger’s design efficiency, MC HE software which is written in C# programming language and in the form of excel generate to a computing report is developed. This software contains design and pressure check calculations for the single- stream and double-stream coil- wound heat exchanger. The results in software are compared with the test data. It turns out using MCHE software to calculate data can be with high precision, and can optimize design. Then this software can be used in engineering design, and has laid the foundation for applications design of the multi-stream coil- wound heat exchangers.By changing the fluid flow pattern and the clearance ratio, numerical simulation for fluid flow and heat transfer within this heat exchanger is studied. The study has used Cosmos(now known as Flow Simulation) as the analysis platform, and used Solid Works to make model. The study has adopted the unit model which is convenie nt to calculate. The results show that: Under the same conditions, the outlet temperature of the shell-side in the countercurrent flow is slightly higher than in the co-current flow; between the inlet in shell and the first surface of pipes, Because of heat transfer in Counter- flow is more uniform than it in co-current flow, counter flow is more advantageous to heat transfer. Appropriately narrowing the gap between coil-wound tubes can reduce the pressure loss of the shell and tube sides, so as to reduce the energy loss in the process of heat transfer; in addition,by this measure, the heat transfer efficiency per unit area is increased, the process of heat transfer is accelerated, and the heat transfer effect is enhanced. So compared to other types of low-temperature heat exchanger, the space occupancy rate and the supplies of equipment are reduced, and initial investment is saved.In this paper, in view of the present situation of the surge in demand for domestic coil-wound heat exchanger market and the basic research started lately, the research on the heat transfer process is the groundwork of serialization and standardization of the wound tube heat exchanger heat transfer process.