Flow And Heat Transfer In Liquid Cooling Garment And Its System Development

When the ambient temperature is above37℃, the human body’s self-regulation is not sufficient to dissipate the metabolic heat generated by the activities, which will lead to the accumulation of heat in the body, resulting in heat stress and lower attention, and likely causing accidents. Staying for a long time in the heat stress can lead to the dysfunction of body thermal regulation, causing symptoms of heat exhaustion or heat stroke, aggravation of cardiovascular disease and even death. The development and research of liquid cooling garment (LCG) have important practical significance to maintain human health, improve work efficiency and reduce the accident rate. This dissertation mainly focuses on the design of LCG system and the studies of flow and heat transfer in it, and has achieved some innovative works as follows:1) A micropump was developed to fulfill the specific application needs of LCG The flow resistance and the pipe network characteristic curve LCG system were analyzed according to the features of LCG A micropump was designed based on the classical velocity coefficient method, combined with specific optimization theories such as great flow design method, partial emission pump design method and area ratio principle. The main parameters of the micropump were determined by the theory. The unsteady flow field characteristics was analyzed using numerical simulation; performance tests of micropump were carried out, obtaining an error less than15%between the simulation and experimental results and verifying the validity of the numerical simulation and optimization. The final prototype of micropump has a pressure head of58.58KPa and a max flowrate of899.2ml/min, with a size of22×22×34mm3and a mass of21g.2) A theoretical heat transfer model was built for human-LCG-environment system. Based on the thermal balance equation of human body, the heat transfer process in the LCG system was analyzed along with the heat transfer path. Expressions were given to calculate the corresponding thermal resistance of various parts. The human-LCG-environment heat transfer model was established and validated by the experimental results with an error less than10%. Heat transfer research on an element tube model revels the correlations between the temperature of the coolants and the pipe length. The overall cooling capacity of LCG is expressed as a function of the volume flow. the ambient temperature, the inlet temperature and associated heat transfer coefficients.3) The whole system design was carried out and an LCG prototype was developed. A process-oriented design steps for LCG development were proposed to and the design objectives of LCG were obtained by application-oriented analyzation. The importance of three core components of LCG system, namely the micropump the pipe network, and the cooling source apparatus was demonstrated. The design process of pipe network and cooling source apparatus were introduced in detail. The LCG prototype was completed with a cooling capacity of243.2W/m2, a sustainable work time of3.36hr. and a mass of only about2kg.4) A simplified temperature-controlled manikin test method was proposed and corresponding test apparatus was built. Advantages and disadvantages of applying the popular manikin test method and sweating guarded hotplate method to the LCG were analyzed. Based on this, a simplified thermostat manikin test was proposed. Two parts of thermal resistance were defined to achieve a more precise description of LCG. The two thermal resistances are:the thermal resistance R1from the human skin to the LCG and the thermal resistance R2form the environment to the LCG. A concept of specific work duration time was proposed, defined as the ratio of the maximum sustainable working time and the system mass. It was used to evaluate the mass cost performance of the sustainable work time of LCG,and can serve as criteria for design optimization and comparison of different LCG prototypes.