Research On The Heat Transfer Characteristics Of The Multi-Thread Coil Tube Generator

The multi-thread coil tube generator is one of the most important devices in the absorption-compression hybrid refrigeration cycle, which occupies about half heat transfer area of the cycle. The heat transfer characteristic of generator and the flue gas from the engine have important effects on the mixed refrigerant cycle.R124-DMAC is selected as the working solution of the generator. The generator is simplified as a two-dimensional model with staggered tube bundle. And then the pressure drop of the gas through it is obtained by simulating with the CFD software. The size of the generator is achieved with31mm as its tube pitch and2.5m-as its heat transfer area under the condition that the pressure drop of the gas is no more than2kPa. The height and the helical number are0.9m and17respectively.The three-dimensional model of the coil tube and the multi-thread coil tube generator are simulated by the CFD software with water as working solution. The temperature and the pressure of the water are same with the R124-DMAC. The temperature of the gas inlet and outlet the generator is lineated along the height of the generator. The results show that the heat transfer load of the multi-thread coil tube generator is almost equal with the total load of each tube and the error is no more than2%. So the simulation of the generator can be instead by the simulation of the single coil tube. And the amount of the simulation calculation and the compute cycles can be reduced.In order to obtain the heat transfer characteristic of the working solution inside the tube, the generator is simplified as a one-dimensional model with straight tube. Then the model is simulated by theoretical calculations. The results show that the temperature of the working solution, the heat transfer coefficient and the heat transfer load of the generator are gradually increased with the rise of the gas temperature, and the mass fraction of the working solution decreased with that.The mixed cycle is simulated using the simplified model and the results show that the refrigerating capacity of the mixed cycle can be provided by the absorption cycle when the power of the vehicle is no less than180kW and the COPab、of the absorption cycle is about0.40. And when the power is no more than40kW. the cycle of the absorption has no refrigerating capacity. When the power of the vehicle is100kW. the refrigeration capacity of two sub-cycles is the same.