大气压强对舱内空气流动与传热特性的影响研究

发布时间：2018-08-25 11:50

【摘要】：自主研发南极科考支撑平台对于可靠保障我国在南极内陆地区开展科学研究具有重要的战略意义。支撑平台主要包括发电舱和仪器舱两部分,其中,发电舱负责实现科考支撑平台的能源供给,仪器舱则主要实现气象探测、数据通讯、现场控制等功能。发电舱和仪器舱内均集成了大量的设备及器件。对于南极高寒环境下的平台运行,其首要任务就是保温。舱内设备在工作过程中产生大量热,可为平台舱体的保温提供重要热源。但是,倘若不对舱内空气流动进行合理组织,舱内热空气上升而冷气体集聚在舱体下部,这将导致舱内温度分布失衡,使舱内出现局部过冷或过热现象,进而影响舱内仪器设备的正常工作。再者,目前对于舱内设备器件传热特性的研究多集中在常压环境条件,环境压强变化对舱内空气流动与换热的影响机制尚不清晰,涉及南极低温、低气压环境条件下舱内设备器件的多热源耦合传热研究更是鲜见报道。为此,本文基于南极Dome A地区典型的极寒、低气压的环境特点,建立了南极科考支撑平台发电舱和仪器舱舱内空气流动传热及设备器件换热的理论模型并进行数值求解,获得了环境条件、功耗等因素对舱内温度场与速度场的影响特性。为进一步揭示低气压环境下舱体内的传热机理,本文设计搭建低压环境电子器件换热特性测试平台,实验研究了影响舱内器件换热特性的多个因素。概况起来,本论文的主要研究内容和取得的主要结论如下：南极科考支撑平台舱体(发电舱与仪器舱)内空气流动与传热的数值研究表明：(1)在发电舱内,随环境压强的减小,柴油机组附近空气温度逐渐升高。在竖直方向上,越靠近舱体顶部,截面平均温度越高。发电舱内空气温度受舱体所处的环境压强、柴油机发热量以及外部环境温度等因素影响。柴油机散热量增加、环境温度升高时,舱内空气温度升高。(2)在仪器舱内,随环境压强的减小,舱内空气对流换热能力减弱,散热设备的表面温度呈升高趋势。仪器舱内外气体交换主要靠空气对流完成,相比于发电舱,空气流量较小,因此舱内温度水平较高。在仪器舱内增加电加热器后,舱内空气温度随电加热功率的增加而升高。低压环境下舱内电子器件换热特性的实验研究表明：(1)大气压强降低的直接体现是空气密度减小,这将导致电子器件与环境之间对流换热能力减弱,使得器件工作稳定后表面温度增加。且压强越低,对流换热的能力衰减越快。(2)低压工况下强制对流能显著增强器件换热能力,降低器件表面最大温度。采用强制对流换热时,空气流动性增强可弥补因压强减小而造成的散热弱化。(3)随环境压强的减小,空气的对流换热能力减弱,这使得器件与环境之间达到热平衡所用的时间增加,故器件热响应的时间常数增大。导热系数及热容当量比是影响器件热时间常数的内在因素。具体来讲,导热系数越大、热容当量比越小,器件热响应过程的时间常数越小。本文较为深入地研究了南极科考支撑平台发电舱及仪器舱舱内空气流动与传热过程,揭示了环境压强变化对舱内空气流动与换热的影响机制,并实验获得了环境压强对舱内器件表面温度及热响应过程的影响规律,对于保障南极科考支撑平台设计与运行具有重要意义。
[Abstract]:Independent research and development of Antarctic scientific research support platform is of great strategic significance to ensure the reliable development of scientific research in the Antarctic inland area of China.The support platform mainly includes two parts: power generation cabin and instrument cabin. A large number of equipments and devices are integrated in the power cabin and the instrument cabin. The primary task of the platform operation in the Antarctic cold environment is to keep warm. The equipment in the cabin generates a lot of heat during the work process, which can provide an important heat source for the insulation of the platform cabin. However, if the air flow in the cabin is not properly organized, Hot air rises in the cabin and cold gas gathers in the lower part of the cabin, which will lead to the unbalanced temperature distribution in the cabin, which will lead to local overcooling or overheating in the cabin, and then affect the normal operation of the cabin instruments and equipment. Moreover, the current research on the heat transfer characteristics of the cabin equipment and devices is mainly focused on atmospheric environmental conditions, and the change of environmental pressure in the cabin. The influence mechanism of air flow and heat transfer is still unclear, and it is rare to study the multi-heat source coupled heat transfer of equipment and devices in the cabin under the conditions of Antarctic low temperature and low atmospheric pressure. The theoretical models of air flow heat transfer and equipment heat transfer are solved numerically, and the effects of environmental conditions, power consumption and other factors on temperature field and velocity field in cabin are obtained. In general, the main research contents and conclusions of this paper are as follows: The numerical study of air flow and heat transfer in the cabin of Antarctic scientific research support platform (power cabin and instrument cabin) shows that: (1) in the power cabin, with the decrease of ambient pressure, the air temperature near the diesel engine set decreases. In the vertical direction, the nearer to the top of the cabin, the higher the average temperature of the section. The air temperature in the power cabin is affected by the environmental pressure, the heat of the diesel engine and the temperature of the external environment. The gas exchange inside and outside the instrument cabin is mainly accomplished by air convection. Compared with the power generation cabin, the air flow rate is smaller, so the cabin temperature level is higher. The experimental results show that: (1) the decrease of atmospheric pressure is directly reflected by the decrease of air density, which will weaken the convective heat transfer capability between electronic devices and the environment, and increase the surface temperature after the device works stably. Forced convection can significantly enhance the heat transfer capability and reduce the maximum surface temperature of the device under low pressure. When forced convection is used, the enhancement of air fluidity can compensate for the weakening of heat dissipation caused by the decrease of pressure. (3) With the decrease of ambient pressure, the convective heat transfer capability of the air decreases, which makes the device reach a heat balance with the environment. Thermal conductivity and heat capacity equivalent ratio are the internal factors affecting the thermal time constant of the device. Specifically, the larger the thermal conductivity, the smaller the heat capacity equivalent ratio, and the smaller the time constant of the thermal response process of the device. The influence mechanism of ambient pressure on the air flow and heat transfer in the cabin is revealed. The influence of ambient pressure on the surface temperature and thermal response of the devices in the cabin is obtained experimentally, which is of great significance to the design and operation of the Antarctic scientific research support platform.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK124

【相似文献】