Study On The Equalization Characteristics Of Refrigerant In Shell - And - Tube Evaporator

dry type shell-tube evaporator is widely used in the refrigerating industry owing to its small demand of refrigerant and steady operation. The bottleneck restricting its wider application is in ordinary heat transfer performance. There is a view proposed in some study that nonuniform refrigerant distribution between the pipes is a major cause leading to invalid improvement in heat transfer performance.In this paper, characteristic of refrigerant flow distribution for the evaporator is studied through theoretical analysis, experimental research and numerical simulation method respectively. And the optimized methods are put forward.Firstly, the criteria to measure uniformity of flow distribution in dry type shell-tube evaporator is provided in this paper. The heat transfer formula of single tube is obtained by theoretical analysis. The effect of flow change on the evaporator is studied. The results show that the existence of nonuniform distribution of refrigerant in the evaporator has an impact on the heat-exchange performance. Nonuniform flow distribution results in heat transfer enhancement. And the influence is especially greater when wetted perimeter less than 1 under the conditions of flow distribution of evaporator.Then, the experimental facility for fluid distribution is established and the experiments are carried out. Due to the limitation of experimental conditions, simplification with 25 distribution tubes and air-water as medium replacement are taken in the experiment. The following two goals are reached:the distribution of fluid visualization results gotten and the numerical simulation of two phase flow under same conditions validated.A 3D model with the size as the real on is explored to conduct data calculation on the dry type shell-tube evaporator The reason of nonuniform distribution in evaporator is analysised, the stress distribution feature in the entrance of each tube and the turbulence area inside the tube are main factor affecting stream distribution and concluded. This model put up with a plan to improve stream distribution way in this device, and the solution is to design a conetype distributor device. It uses the simplified model conduct data mimetic research on improved stream distributor. During research, in order to avoid the influence of stream speed to stream distribution, it analysis the stream speed, and concluded 1.5m/s is proper inlet stream speed.Based on calculation and analysis of the data in 13 kinds of conetype distributor, it choose the top of cone’s place in beneath center line of distributor inlet, which can reach the best distribution effect. For this conetype distributor, it considered the influence of different cone top height "h" to stream distribution. The result shows, when h=35mm, distribution effect is the best.Results of this study are expected to provide a reference to the dry type shell-tube evaporator performance improvements.