| Under the background of "carbon peak,carbon neutral",the research and development of efficient green refrigeration system has become a research hotspot.In large and medium-sized industrial refrigeration systems,the direct cooling system is limited in some areas due to its use safety and large refrigerant charge,especially in the regulatory background of "ammonia color change",the indirect refrigeration system has been widely concerned.Subject to indirect refrigeration system as the research object,indirect refrigeration system thermodynamic analysis and experimental research,the air side heat balance method is used to measure the refrigerating capacity of the system by adjusting the flow to change cold agent use and system operation condition,the contrast analysis of the four kinds of single-phase secondary refrigeration,LM-1 LM-4,LM-8 and glycol in indirect refrigeration system operation,The influence of its physical properties on the performance of the whole system was explored,and the optimal use scheme and operation condition of the refrigerant under different working conditions were obtained,which provided a reference for the practical engineering design of the indirect refrigeration system.In view of the traditional tube heat exchanger cooling speed is slow,the use of refrigerant is large and so on.In this paper,the traditional tube structure is optimized,and the multi-finned tube heat exchanger is experimentally studied.Based on the multi-finned tube heat exchanger,a new type of annular channel multi-finned tube heat exchanger is proposed,and the theoretical exploration is carried out.The results show that:(1)In the 0 ℃ storage temperature stability experiment,the performance of LM-1and LM-8 secondary refrigerant is better than that of ethylene glycol,and the performance of LM-4 secondary refrigerant is similar to that of ethylene glycol.The comprehensive performance coefficients of the system using LM-1 and LM-8 secondary refrigerants were3.17% and 6.06% higher than those using ethylene glycol secondary refrigerants.(2)The performance of LM-8,LM-1 and LM-4 secondary refrigerant is better than that of ethylene glycol in the temperature stability experiment at-18 ℃.The comprehensive performance coefficients of the system using LM-8,LM-1 and LM-4secondary refrigerant increased by 12.3%,3.9% and 1.7%,respectively,compared with those using glycol secondary refrigerant.(3)The fin length has some limitations.With the increase of fin length,the fin efficiency decreases.In the same multi-fin row heat exchanger,the horizontal and vertical fin efficiency is higher.(4)Through theoretical calculation and analysis,a comparison was made between the new annular passage tube heat exchanger and the traditional tube heat exchanger,and it was found that the liquid filled type was not the most optimal liquid filling way,and the new structure reduced the working medium consumption by 31.7%-45.3% compared with the traditional structure.The convective heat transfer coefficient of the new type of tubular heat exchanger is 6.29%-24.78% higher than that of the traditional tubular heat exchanger.This conclusion has only been theoretically analyzed and needs further experimental study.(5)The comprehensive experimental test results show that the performance of LM-1and LM-8 is better than that of ethylene glycol,LM-1 has low flash point and hidden safety problems,and LM-8 has the best performance but high price.LM-4 is very similar to ethylene glycol.In the existing system,LM-4 coolant with lower price can be used to directly replace ethylene glycol on the basis of cost,safety and other factors.Theoretically,the performance of the new annular channel tube heat exchanger is improved significantly. |
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