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Nickel-Metal Hydride Battery Cooling System Research For Hybrid Electric Vehicle

Posted on:2008-04-02Degree:MasterType:Thesis
Country:ChinaCandidate:Y Y LouFull Text:PDF
GTID:2132360212976450Subject:Refrigeration and Cryogenic Engineering
Abstract/Summary:PDF Full Text Request
With the increasing attention of environment protection and energy shortage, Hybrid Electric Vehicle(HEV)has been the most feasible choice. Many vehicle enterprises are involved in the HEV development over the world.HEV is enslaved to the performance of battery pack, which is greatly affected by temperature. The target of Nickel-Metal hydride battery cooling system for HEV is to make battery work in its optimum temperature range 20 oC~40 oC and less than 5 oC temperature difference, in order to keep its formal performance and extend its life.The main jobs in this thesis include:(1) Experiment of single Nickel-Metal hydride battery to get its thermal character in the charge and discharge process. The charge process is exothermal, and battery temperature increases gradually. Oxygen evolution reaction takes place at the charge end, sending out a lot of heat, and make temperature increase much more quickly. Temperature variation in the discharge process is decided by the current. Therefore, satisfying heat model is helpful for battery pack design by software way. By experiment and theoretical analysis, we got some necessary parameters for single battery, built the thermal model, and programmed to simulation the heat process. The simulated results coincided well with the experiment data.(2) Battery pack structure is enslaved to the available space of vehicle. Cinquefoil battery pack offers tight and efficient heat dissipation battery cell for HEV. It is constituted by 5 long modules, which are in cinquefoil shape as a battery cell, whose total voltage is 36V. Use metallic bearing to make use of its heat dissipation by conduction. Electric isolated thermal gasket is then laid between battery and bearing. However, because of the machining craftshortage, module concentricity can not be ensured. Gasket structure and its effect to the conduction efficiency are discussed. Battery heat dissipation efficiency analysis is based on extreme condition for the complication of actual vehicle operation. Under forced ventilation condition, the simulated results fit the cooling target.(3) Experiment of cinquefoil type prototype of battery pack to validate and improve the design. With fan, battery temperature and temperature decreasing profile are close to the simulated results, but temperature difference is bigger. The operation temperature is in the optimal range, but the temperature difference is not. So the structure still needs to be improved. Fluid velocity around batteries varies little because of the short fluid path. Fluid temperature is increasing, however, which worsens heat transfer effect away from fan. So it will be better if the lower bearing passage area be decreased to increase the local velocity. Fluid scanning area of modules represents the local heat transfer ability, so equal passage length in bearing will better the equalization. Temperature increase is unavoidable with large current, and can't be dissipated by forced ventilation in time, but still good choice.(4) When the available space is relative large, we can use battery pack with more batteries—wave type box for battery pack. Wave type box for battery pack is constituted by 20 long modules, the total voltage is 144V. Inlet case is in wave shape, which can lower the power lose and conduct more fluid to take away the heat of inside modules. The top case is in square shape, which can strengthen heat dissipation of fringe modules. The inlet flow is divided into two parts, responsible for the right-up field and right field respectively. The inlet channel is narrowed along the flow to increase the lower fluid pressure and the modules can be cooled equally by number. Under forced ventilation condition, the simulated results fit the cooling target.
Keywords/Search Tags:Hybrid Electric Vehicle, Battery pack, Cooling, Structure Design, Optimization
PDF Full Text Request
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