Vortex tube cooling clothing can provide cooling protection for workers working in high temperatures and improve the comfort of the human body's microclimate zone. The cooling methods, principles, characteristics and research progress of various types of cooling suits (gas cooling suits, liquid cooling suits and phase change cooling suits) are analyzed, and the key technologies and development directions of phase change cooling suits are emphasized: research on easy plasticity, Corrosion-resistant packaging materials and corresponding packaging technology can solve the problems of deformation, leakage and water erosion of liquid phase change materials; combine nanotechnology with phase change material microcapsules to develop composite phase change materials with long acting time and good heat dissipation , improve the thermal conductivity of phase change materials; combine phase change cooling technology with other technologies to develop new cooling suits with controllable effects, and at the same time develop equipment or new materials that can quickly activate phase change materials, so that phase change materials can quickly Store cold.

Currently, there are more than 60 high-temperature mines in China, of which 38 have temperatures exceeding 30°C. As shallow coal resources are decreasing day by day, the main body of mining in the future will turn to deep coal resources. Therefore, high-temperature heat damage has become the sixth major disaster after mine gas, fire, coal dust, mine pressure, and water, seriously restricting the rational and effective mining of deep coal resources. On the other hand, the ambient temperature around steel smelting workers can sometimes reach 50°C. Being in a high temperature environment for a long time makes people prone to fatigue and lack of energy, which affects work efficiency. At the same time, water and salt metabolism in the body is disordered. Some physiological systems will lose a lot of water due to high temperature, endangering the physical and mental health and personal safety of workers. Therefore, it is of great significance to study cooling clothing suitable for high temperature environments.

Classification of cooling suits

Classification by clothing structure

Vortex tube localized cooling suit. Local cooling clothing is designed based on the differences in heat production and heat dissipation in different parts of the human body. Research shows that the body's basal metabolism is mainly concentrated in the head and trunk. When the human body is working, different parts of the human body sweat and dissipate heat in different intensities. The trunk has the largest basal metabolism and the highest heat capacity. Therefore, in the current research on local cooling clothing, cooling caps designed for the head and cooling tops or vests designed for the torso account for a large proportion. The early passive cooling vest developed by the U.S. Navy Clothing and Fabric Research Institute and suitable for submarine personnel wore. Its cooling principle is to use the freezing gel pre-placed on the inside of the garment to take away the heat generated by the human body and achieve the purpose of lowering the body temperature; the vest The frozen gel is made of starch, water, alcohol, activator and other raw materials mixed in a certain proportion. It is a colloidal liquid at -22~-18℃, has a large heat capacity, is soft and close-fitting. Guo Yucheng invented a cooling suit that does not require an additional power supply. The main implementation method is to first set up a cold source, arrange a heat-conducting medium flow channel between the cold source and the cooling suit, and arrange a heat-conducting medium flow channel between the heat-conducting medium flow channel and the cold source. Set up a thermoelectric generator with one side facing the cold source and one side facing the heat transfer medium flow channel; a pump or fan is installed in the heat transfer medium flow channel. The heat transfer medium can be transported by a pump or a DC fan. The pump or fan is connected to the thermoelectric generator through a wire. At the same time, the pump Or the energy for the fan to push the heat-conducting medium is provided by the thermoelectric generator. This device uses the temperature difference between the cold source and the heat transfer medium as the energy to promote the flow of the heat transfer medium. It is very convenient for the user without the need for an additional power supply.

Local cooling clothing is widely used in various fields of production and life due to its simple structure, suitable wearability, good cooling effect, and strong practicability.

Total body cooling garment. The advantage of full-body cooling clothing is that it can comprehensively cool down the trunk, limbs and other parts, keeping the overall body in a more comfortable state. Full-body cooling suits are generally suitable for special operations or special environments, such as aerospace workers, environments with extreme heat that require full-body protection, environments with toxic and harmful gases, etc. For example, Zhang Jizhou designed a constant-temperature protective clothing that is suitable for both high-temperature and low-temperature environments and can also be used in harmful gas environments. This protective clothing consists of four parts, namely the clothing body, a constant temperature source, and an air conditioner. Presses and helmets that can be used in harmful gas environments are equipped with several thermostatic panels with S-shaped arrangement and spirally coiled liquid flow pipes in the garment according to the human body shape characteristics, and a distributor with a double-chamber double four-way structure is used. , connect the thermostatic plate pipes placed on the chest and left arm, back and right arm, and both legs in series to form three branch circuits. The constant temperature source, distributor, and thermostatic plate are all connected with hoses to form a closed loop system. As a constant-temperature liquid circulates in a closed-circuit pipe, the temperature inside the garment remains balanced. However, full-body cooling suits also have shortcomings. For example, when used for high-temperature workers with large working ranges and high intensity, such as firefighting, underground mining, and steel rolling, it will affect their work efficiency, work convenience, and clothing comfort.

Classification by cooling medium

Vortex tube gas cooling suit. Gas cooling suits are active cooling. Gas cooling clothing first cools the air with a refrigeration device. After purification, the cold air is discharged into the clothing through pipes or clothing interlayers. The flowing cold air dissipates heat and cools the human body, making the human body's microclimate zone in a relatively comfortable state. Its heat dissipation principle is to accelerate the evaporation of sweat and enhance air convection, thereby achieving the purpose of cooling.

According to different heat dissipation methods, gas cooling suits are divided into evaporative gas cooling suits and convection type gas cooling suits. Evaporative gas cooling clothing has no requirements on ventilation temperature and mainly uses water pressure gradient to promote sweat evaporation and heat dissipation. For example, the British MK1 and K2 and the American MA-3 evaporative full-body ventilation clothing have a good cooling effect when the human body is heated and sweats. Convection gas cooling clothing mainly uses the convection effect of wind flow in a small space to take away heat. The ventilation gas temperature is required to be lower than the average skin temperature, so the wind needs to be pre-cooled in advance. The "Cooling Armor" vest-type air conditioning system developed by USN uses an air conditioner to input conditioned low-temperature air into the duct in the flight suit to cool the human body. This system can reduce the temperature around the pilot by 18°C; the system is independently powered by batteries. , has nothing to do with the aircraft's power supply system and can be used even after the pilot has left. However, under normal circumstances, the ventilation system can better exert its ventilation and heat dissipation effect when the human body is sweating. Therefore, when the cold source is insufficient, the ventilation temperature should not be too low and should be reasonably selected according to the actual needs of the system. Cooling suits with micro-fan and vortex tube technology as the core are also a major feature of gas cooling suits, such as the micro-fan array system human cooling suit developed by Zeng Yanzhang and others, and the air-cooled personal protective suit designed by Liu Yuan and others.

Gas cooling clothing has the advantages of rich gas source, long cooling time, and good cooling effect. However, gas cooling suits also have their own limitations. For example, the interlayer of the clothing is filled with air, which affects the flexibility and maneuverability of the operator, thereby affecting the efficiency of underground operations. On the other hand, the underground equipment has very high explosion-proof requirements, and gas cooling suits and There are dangers associated with its accessory equipment. Therefore, a lot of in-depth research work is needed to promote gas cooling suits underground.

Liquid cooling suit. Liquid cooling clothing, like gas cooling clothing, is an active cooling system. Pipes are usually arranged inside the clothing, and then low-temperature liquid is input into the pipelines, and the circulating flow takes away the heat of the human body to achieve the purpose of cooling the microenvironment inside the clothing. The cooling media of liquid cooling suits mainly include water, ice-water mixture, phase change emulsion and microcapsule emulsion. Liquid cooling suits generally consist of a basic garment part and a pre-cooling device.

In 1962, Burton et al. developed the world's first liquid cooling suit using water as the cooling medium, as shown in Figure 1. Subsequently, liquid cooling suits were applied to NASA's Apollo moon landing program, and the Apollo liquid cooling suits laid the foundation for the development of modern cooling suits.