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Planar radiant air conditioning with capillary networks is a type of concealed air conditioning system that is typically installed within walls or ceilings. It features a small temperature difference with the room temperature, a large heat exchange area, and combines heating and cooling functions in one system. It represents the most advanced heating and cooling technology available today and embodies the future direction of air conditioning technology. I. Introduction to Planar Radiant Air Conditioning with Capillary Networks: Capillary networks mimic the mechanism of plant veins and human capillaries; they consist of capillaries with an outer diameter of 3.5–5.0 mm (and a wall thickness of around 0.9 mm) sowie main supply and return pipes with an outer diameter of 20 mm (and a wall thickness of 2 mm or 2.3 mm). A planar radiant air-conditioning system using capillary networks generally consists of a heat exchanger, a distribution station equipped with a circulation pump, a temperature control system, and capillary networks; it is also accompanied by a dehumidification system, etc. Heat is transferred through water or other media, and room temperatures are regulated in a radiant manner. The key technologies related to capillary network fittings have been subject to patent applications for invention and utility model by Beijing Pulefu Environmental Technology Co., Ltd. The insulation layer, heat dissipation layer, and capillary network are used together to form a capillary network heat exchanger, **which enhances the heat dissipation capacity of the capillary network structure alone and broadens its applications, while also protecting the capillary tube walls from damage. In May 2007, this product was tested at the Air Conditioning Research Institute of the China Building Science Academy (**Air Conditioning Equipment and Grain Storage Supervision and Inspection Center**). Taking the test of a certain node as an example, the results are as follows: 1. At an experimental pressure of 105 Mpa, there is no leakage ； 2. At a supply water temperature of 45°C, a return water temperature of 40°C, a reference temperature of 20°C, and △T=22.5°C, the heat dissipation per unit area of the sample is Qdr=240.88 W/m2 ； 3. At a supply water temperature of 15°C, a return water temperature of 20°C, and a reference temperature of 26°C, with a ΔT of 8.5°C, the cooling capacity per unit area of the sample is Qdl = 122.84 W/m2. II. Structure of the capillary network heat exchanger The capillary network heat exchanger is composed of a capillary network, an insulation layer, and a heat dissipation layer. 1. The piping system is of the parallel distribution type, with the main pipes having a diameter that is more than 6.4 times that of the branch pipes; this allows water to flow evenly through all the branch pipes while simultaneously eliminating any air present within the pipes ； 2. A reasonable wall thickness design ensures that the pressure-bearing capacity of the entire system is 2 to 3 times the design pressure of the system ； 3. Capillary tube networks are used for heat exchange; they provide a large heat exchange area and a small spacing between the heat exchange tubes, which allows heating or cooling to be achieved with a small temperature difference. This is of great significance for energy savings in low-temperature applications ； 4. The installation thickness of capillary tube heat exchangers can be as low as 5 mm, allowing them to be easily installed in floors, ceilings, and the surrounding interior walls ； 5. Used indoors, the capillary network heat exchanger acts as a \"skin\" that provides external insulation and internal temperature regulation; when used in conjunction with a temperature control system, it enables high levels of intelligence in residential buildings ； 6. Designed for outdoor use, it is the most efficient collector when buried in the soil in combination with ground-source heat pump technology. III. Main performance indicators of capillary tube heat exchangers Content Items Products and technologies Structural design: A composite structure consisting of an insulation layer, capillary tubes, and a heat dissipation layer Raw materials: High-quality PPR raw materials from Nordic countries as well as domestically produced PPR raw materials Pipe specifications: Main pipe: 20/16 ； Branch pipes: 4.3/3.5; long-term pressure resistance of 20 kgf/cm2, capable of withstanding a pressure of 1.5 MPa; maximum temperature tolerance of 110°C, and it can sustain a working temperature of 65°C over the long term. The heat exchange capacity ensures that a supply and return water temperature of 16/18°C is sufficient to achieve the desired comfort level; this system’s performance is 50% that of traditional central air conditioning systems ； A supply water temperature of 28/32°C is sufficient to achieve the effect of a radiator. Its applications include ceiling radiation systems, fluid-regulated interior insulation walls, ultra-thin floor heating systems, and the heat collectors used in ground-source heat pumps. IV. Advantages of capillary tube network-based radiant air conditioning: High efficiency and energy savings – Capillary tube networks have a large surface area for heat dissipation; they provide heating and cooling through radiation. For heating, the supply water temperature should be 28–32°C, while for cooling it should be 16–18°C, resulting in high efficiency and energy savings. The combination of capillary networks with ground/water source heat pumps achieves the highest thermal efficiency, saving over 70% more energy compared to traditional central air conditioning systems. Ultra-high comfort: Radiant heating and cooling ensure rapid and even temperature changes in the room, with a gentle and quiet operation, free from air movement and equipment noise. Space-saving and does not increase the load on the building: The installation thickness of capillary tube networks is generally less than 5 millimeters, and the weight of water filled in them is between 600–900 grams per square meter; they can be easily installed on ceilings, floors, or walls, making installation very convenient. For example, in a 20-story building that uses traditional central air conditioning, the use of capillary tube systems can save 2 floors of space, resulting in significant economic benefits. Planar radiant air conditioning with capillary networks is suitable not only for new buildings, but also holds irreplaceable value for the energy-saving renovation of old buildings compared to traditional air conditioning systems. Eco-friendly: The system operates in a closed loop, producing no wastewater or waste gases that cause pollution. The raw materials are hygienic and non-toxic, and can be recycled. No air convection, no dust or noise. Long service life: The system operates at low temperatures and pressures, preventing pipeline damage caused by high temperatures and pressures, and no scale forms on the inner walls. The system uses entirely corrosion-resistant materials such as PP-R and red copper, and it is separated from the main circulation by an alloy steel heat exchanger; thus, oxygen penetration does not cause corrosion or accumulation-related blockages. High-quality PP-R capillary networks can remain in excellent condition for 50 years when used under normal temperature and pressure conditions. Maintenance-free: Generally, each pipe network is subjected to rigorous testing at 10 times the operating pressure (2 MPa) for an extended period before leaving the factory. After installation, the entire system is tested at a pressure of 1 MPa; any leaks that occur can be safely repaired using hot melt welding. It generally does not get damaged in normal use, so no maintenance is required. V. Market prospects for planar radiant air conditioning using capillary networks. At present, China has the highest emissions of sulfur dioxide in the world, the second-highest emissions of carbon dioxide, and the second-highest energy consumption levels globally. However, its per capita consumption of commercial energy is half of the world average and one-tenth of that in the United States. Our country is in a stage of rapid industrialization and urbanization; the growth of industry and the upgrading of consumers’ spending patterns have led to an even greater demand for energy. Energy will play a very crucial role in the development of **; if energy issues are not addressed properly, they could hinder the overall development of **. In particular, building energy consumption accounts for 40–50% of total energy consumption, with heating in winter and cooling in summer being the main components of this energy use. In addition to using exterior wall insulation and advanced door and window systems, continuous improvements and innovations in heating and cooling methods will be key to saving energy. As we enter an era of energy shortage, the Renewable Energy Law of the People’s Republic of China came into effect on January 1, 2006. Subsequently, the Ministry of Construction issued the Draft Regulations on Building Energy Efficiency Management. Saving energy is an important strategic goal for our country at present, and energy-saving technologies and products face huge market demand. Planar radiant air conditioning using capillary networks is not only efficient and energy-saving, but also features environmental friendliness, space savings, and high comfort, which gives it great prospects for market development. Since the completion of Tsinghua University’s energy-saving demonstration building, in just over a year, although most people still lacked understanding of capillary tube technology and were deterred by its cost, some high-end residential and office buildings were among the first to adopt this technology, such as the Innovation Building run by the Beijing Science and Technology Commission, the Wanwanshu Villa Complex in Beijing, and the Fengshang Community in Nanjing. It is understood that the capillary tube network radiant air conditioning technology is also widely used in foreign countries such as Germany, the United Kingdom, and Brazil. Planar radiant air conditioning with capillary networks will replace traditional central air conditioning or conventional underfloor heating as the mainstream method for heating and cooling in buildings in the future.