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In order to obtain a higher heat transfer coefficient of refrigerant flow, the diameter of tubes tends to be smaller and smaller, which leads to large pressure drop of the refrigerant flow. Therefore, multiple numbers of parallel refrigerant passages are employed by using distributors. It is very important to distribute the two-phase refrigerant evenly into each tube, otherwise the thermal performance is significantly deteriorated. The performance reduction by flow mal-distribution could be as large as 20–25%. The goal of this paper is to investigate the influence of different configurations to the performance of refrigerant distributors by experiments and computational fluid dynamic code. The effects of mass flow rate and quality of distributor inlet on the characteristics were also quantitatively considered. In this study, an experiment test rig was built to measure the mass flow rate and quality of four circuits after using distributors under different conditions respectively. Refrigerant R410A was used as working fluids. Three classic types (jet, cyclone and reservoir) of distributors with four paths were manufactured and tested under relevant operating conditions. The inlet temperature was 4°C, mass flow rate range was 50–100 kg/h and the quality range was 0.1–0.3. Experimental results show that the maximum deviation of mass flow rate for jet, cyclone and reservoir type is 13.0%, 21.6% and 10.9%, respectively; the maximum deviation of quality was 0.08, 0.10 and 0.05, respectively. In addition, the standard deviation of mass flow rate and quality over four paths were selected to evaluate the performance of different type distributors. The results show that the performance of jet and reservoir are better than cyclone. The flow behavior of two-phase refrigerant such as phase distribution and separation phenomena was studied by Computational Fluid Dynamics (CFD). The flow pattern of inlet for R410A was investigated and used in the present model. The results in the present model show good and reasonable approximation with experimental data which validate the CFD simulation. CFD simulation analysis elucidates the mechanics which shows how the configuration and operation conditions affect the refrigerant distribution.

Flow mal-distribution of refrigerant in small diameter tube heat exchangers is a great concern, which may lead to a 25% efficiency loss. Two-phase refrigerant distributors are set before evaporators to separate refrigerant into parallel paths uniformly. In this paper, a new type of distributor with two barrels is proposed. Experimental test and numerical simulation were both carried out to evaluate the performance and to understand internal hydrodynamic flow behavior. Compared with the previous distributor, it is found that the double-barrel distributor with proper parameters performs better. The relative error between experimental and simulation results is less than 15%, which proves the reliability of the established simulation model. Computation fluid dynamics (CFD) calculation indicates that the distribution performance is improved with properly larger bottom and top barrel diameters. With the increase of the bottom barrel diameter, beneficial reflux of refrigerant occurs in bottom barrel and when top barrel diameter is larger, little refrigerant flows directly into outlet capillary tubes without mixture or reflux. In addition, parameters such as top barrel diameter, top barrel height, bottom barrel diameter, bottom barrel height, mass flow rate and quality are studied by Taguchi Method to analyze the parameter sensitivity. The effect of the parameters listed below ranges from biggest to smallest: mass flow rate, bottom barrel height, quality, top barrel height, bottom barrel diameter and independent top barrel diameter. An optimized two-barrel distributor is achieved with proper top and bottom barrel diameters and larger bottom and top barrel heights.

The performance of an ejector as an expansion device rather than the conventional expansion valve or capillary tube in a vapor compression system is experimentally analyzed. Experiments have been conducted using 28 ejectors of different dimensions at the same condenser and evaporator temperatures, and it has been observed that for utmost performance, an optimum area ratio of the ejector is required. One of the ejector geometry has been experimented further for a wide range of condenser and evaporator temperatures. The coefficient of performance is found to be enhanced by at least 10% in comparison to the conventional vapor compression system for the considered range of condenser and evaporator temperatures and the maximum improvement in COP obtained is 12.83% at 14.3^∘C evaporator temperature and 32.4^∘C condenser temperature with 17.9211 ejector area ratio. The refrigerant R134a has been used as the working substance.

A mathematical model was set up to simulate the heat transfer process and performance of the molten salt phase change heat storage tank of the solar power and cooling system driven by Linear Fresnel reflector(LFR). Meanwhile, an experiment is also built to validate the model. For this thermal storage tank, mature industrial intermediate-temperature ternary salt is selected. ANSYS software is utilized to simulate the performance of heat transfer process of phase change based on the enthalpy method. Heat transfer characteristics and factors are analyzed according to the results of the simulation and experiment. The results show that the data coming from the simulation and the test fit each other well and the simulation is acceptable.