In order to further improve the thermal efficiency of the box-type sun-dried solar water heater in collecting solar radiant energy, based on the analysis of the thermosiphon convective heat transfer mechanism of the water molecular fluid in the box after the box-type sun-dried water heater is heated at the top of the box, Some experts tried to add a baffle made of heat-insulating material on the inner and back side of the heat collecting panel of the original box-type sun-dried water heater, as shown in Figure 1.
This heat-insulating baffle is used to cut off the water molecules that are close to the heat-collecting panel and are first heated by the heat-collecting metal panel by thermal conduction, and the lateral mixing channel between the water molecules at the back of the box and more low-temperature water molecules; forcing the heated The water molecules use their own temperature to increase and their specific gravity decreases, and the obtained thermosiphon pressure moves upward along the baffle to move up the temperature difference. After reaching the top of the box, they push the upper part of the box according to the thermal power of their own molecules. Under the action of its own gravity, the low-temperature water molecules move in the downward direction along the side wall of the box; finally, they pass through the reserved gap channel at the bottom of the box and are forced to enter the heated interlayer between the deflector and the heated panel of the box. , Accept the solar radiant heat transferred by the heat-collecting metal panel in the “thermal conduction” heat exchange method. When the low-temperature water molecules are heated again in this channel, their specific gravity becomes smaller, and a new thermosiphon pressure is obtained, and they float up along the baffle channel again, pushing other water molecules with relatively low temperature, and they have experienced it with themselves. The journey is the same, along the same flow direction uninterrupted directional movement, repeating the mistakes of convection cycle heat exchange; this cycle starts again and again, under the continuous heating of solar radiant heat, the water molecules in the box go through many cycles. After that, the whole tank of water is finally heated to a higher usable temperature.
For the water molecules in the box that were originally in the sweltering state, the addition of a baffle to form a thermosyphonic convective heat exchange effect is more chaotic and disorderly than the chaotic and disorderly thermal movement of the water molecules in the original sweltering state. The light-heat heat exchange efficiency has undergone a fundamental change. Because water molecules themselves are poor conductors of heat, the efficiency of heat energy transfer and exchange only through the disordered thermal movement between water molecules is extremely limited. After adding a baffle plate to the box-type sun-dried solar water heater, the water molecules in the water heater can be transformed from a disorderly conduction heat exchange state to an orderly temperature difference convective cycle heat exchange state within the entire tank fluid; thus greatly The light-heat conversion efficiency of the box-type sun-dried solar hot water system is improved. It can be said that the emergence of the deflector has laid the foundation for the birth of another new type of solar hot water system-the integration of storage and “diversion circulation” solar water heater.
Integration of collection and storage and separation of collection and storage are two completely different solar water heating systems. Both of these systems were once the two strategic goals that people have pursued separately in the development of domestic solar hot water system technology. It should be said that the two have their own specialties and professional uses in different places, different needs and different conditions of use. In the early stages of the development of solar water heaters in China, domestic water heaters were more developed and utilized as a system that integrates storage and storage. Because the biggest advantage of this type of system is its strong integrity, compact structure, and low price. The entire system consists of a compact integral part; there are up to 2 to 4 nozzles on the box (the cold water inlet, respectively, Hot water outlet, vent and overflow); there are many integrated storage water heaters, and the cold and hot water inlet and outlet are combined into one; the vent and overflow pipe are used for two purposes. The biggest limitation of this system is that the system cannot be made too large, because the too large “collection and storage in one” solar water heater is not convenient to transport and install; it lacks flexibility in specific use. In the initial stage of China’s reform and opening up, due to the low proportion of urban residents’ tap water supply and the low penetration rate of household toilets; therefore, the integrated storage system was once very popular. In fact, in the special working environment with greater mobility, or in remote agricultural and pastoral villages, it should be said that the integrated storage system still has extremely unique and irreplaceable advantages and its use value.
China’s “diversion circulating domestic solar water heater” series products first appeared in the mid-1980s. This high-efficiency solar hot water system that integrates storage and storage, under the production conditions of the year, only used two 1 x 2m2 galvanized thin plates (or aluminum plates) after stamping and processing, and then two symmetrical forming plates on the top and bottom. In between, cold work riveting and welding on a heat-insulating baffle, and then using special equipment to seal the end caps on both sides of the water tank and the bottom of the collector and the four sides of the periphery on both sides with a crimping non-welding process ( as shown in Figure 2). Although the effective area of the new type “diversion circulating domestic solar water heater” collector is only about 1.5m2; the volume of the water tank is 130L; the thermal efficiency is more than 60%; the installation angle of the system can be infinitely between 10° and 60°. Adjustable; if water is used in different periods, the daily output of hot water above 45°C of the system is ≥200L/d. Only hot water is installed in the water tank of the system; cold and hot water are in and out by a single pipe; when the system is remotely replenishing water on separate floors, the system is equipped with a simple water full alarm device, reflecting the delay time of no more than 3 seconds. After the product was put into production, due to the constraints of anti-rust materials and processing technology, it failed to form a large industrial scale. In the history of domestic solar water heating system development in China (Yunnan), this water heater is the first to integrate the high-efficiency natural circulation heat exchange process between the collector and the heat storage; thus, the pipeline of the natural circulation system is greatly simplified. The structure reduces the heat loss of the system and the circulating water resistance, improves the light-to-heat conversion efficiency and the available hot water output; and eliminates the restriction on the installation angle of the circulating pipeline, and is the first to realize the stepless and simple adjustment of the system installation angle. Special features of advanced technology.
In the mid-to-late 1980s, he also successfully developed a variety of portable solar water heaters for different purposes. At that time, the goal of design and manufacture was to develop a series that could be supplied to Chinese guards on the reefs of the Xisha and Nansha Islands in the South China Sea. We use new solar energy utilization devices for heatstroke prevention and cooling, seawater desalination, floating swimming and domestic hot water supply.
“Portable Multifunctional Solar Water Heater” is a multifunctional natural circulation solar water heater that integrates storage and is made of flexible waterproof and air-tight materials. Since the system is equipped with a simple isolation and diversion device, an air cushion insulation layer, an air cushion pillow and an air cushion insulation support for adjusting the position of the water chamber, it can effectively use solar radiation energy to heat under the conditions of the living environment in the wild Low temperature domestic hot water. Through optimized design, this product can provide domestic hot water for field workers, border soldiers or travel companions, or be used as a travel mattress for heat dissipation, heat preservation, and moisture prevention, and a life-saving raft for drifting and swimming. The new product was also restricted by materials, processing methods, and the market, and failed to form a mass production application.
At the beginning of 1988, a model called “thermal diode solar water heater” was developed (as shown in Figure 3); this is also a portable solar low-temperature heat utilization product that integrates storage and storage. The goal is to provide field workers and travel friends. , Solar water heaters used by herders or workers under emergency rescue conditions. This water heater is composed of a heat-collecting metal panel stamped and formed by a thin aluminum plate, a rectangular plastic shallow basin, a foldable inflatable (or sponge) insulation cover and a removable simple bracket. The total weight of a single system is about 6~8kg; the heat collecting plate surface is 0.7m2; the heating water volume is about 60L at a time; it can provide domestic hot water for 2~3 people. The system can be packaged by parts, and 6 sets can be packed and transported at a time. After arriving at the destination, the system can be assembled into an independent system with supporting special tools. It can also be connected in series to form a small shared solar hot water system.
This type of water heater is an updated product of the box type sun-dried solar water heater with diversion and circulation device. Although this product is still a one-way solar thermal utilization device that integrates storage and storage, it uses a non-metallic flat plate with heat insulation and an aluminum panel coated with a selective heat absorption layer after anodizing process. The combination is a set of high-efficiency heat collection-heat exchange device. The device is organically connected with the plastic hot water storage tank through a rubber sealing strip and completely sealed as a whole, and a one-way automatic control valve that can prevent the reverse flow of hot water is installed on the non-metal heat insulation board. Therefore, the natural circulation light-to-heat conversion efficiency can be effectively improved, and the heat dissipation loss caused by the reverse circulation of the system can be effectively reduced. All parts and components of this product can be produced in a moulded assembly line, and the bulk parts are packaged and transported. The water storage tank itself is a multi-purpose shallow pool plastic basin. It only needs to be temporarily used when collecting solar heating water. The assembly parts of the “heat collection-heat exchange-one-way circulation” panel, and several large portable parts such as a large plastic basin and an inflatable thermal insulation jacket sewn with plastic cloth. Water; align the sun and put it on a simple stand to put it into use. The product has low metal consumption, compact structure, low price and excellent performance. It is especially suitable for disaster relief and rescue. After field workers arrive at the temporary camp, they are randomly combined and used as a simple solar hot water equipment. The product prototype was tried in remote mountain villages and received unanimous praise and welcome; however, due to the shortage of large-scale mold processing and large-scale injection molding equipment in China that year, industrialized mass production and application were not realized.
The above-mentioned series of natural circulation solar water heaters with integrated storage and storage have been changed into history, but their technical feasibility, advanced structure and product practicability have not lost their actual use value. Our brief introduction here is just to explain that the integration of collection and storage is also a structural form of solar water heating system with a wide range of uses. It can also play its unique role in certain special occasions. With the development of China’s national economy, the improvement of people’s living standards, and the popularization of family cars and RVs, it is believed that similar tourism products or disaster relief emergency products also have huge potential market space and value for promotion and application.