Thermal insulation performance test of various industrial furnaces, heating pipes, buildings, cold storage, etc. It is usually called energy-saving monitoring (energy-saving detection or energy-saving test). For this kind of test, China has corresponding national standards, such as GB/T 4272-2008 "Technical General Rules for Insulation of Equipment and Pipelines" and GB/T 8 174-2008 "Testing and Evaluation of Insulation Effect of Equipment and Pipelines". GB/T 10295-2008 determination of steady-state thermal resistance and related characteristics of thermal insulation materials; heat flow meter GB/T 17357-2008 field measurement of surface heat loss of insulation layer of equipment and pipelines; heat flow meter method and surface temperature method. . Including radiation heating source, solar radiation intensity and solar equipment, fire occurrence and protection, thermal intensity and distribution of gunpowder, explosives and propellants, thermal intensity and distribution of various combustion chambers, thermal comfort test and control of artificial environment, high temperature wind tunnel test and so on.
In this test, some projects may need to consider simultaneous thermal convection test.
Some of these tests also have corresponding national standards, such as GB/T 1 1785-2005. As the heat flow sensor is the sensitive element of the heat flow meter, the development process of the heat flow sensor determines the development process of the heat flow meter.
19 14 years, the first heat flow sensor for directly measuring heat flow in the field appeared. At that time, Professor Henky from Germany wanted to measure the heat flow through the floor in the brewery. He covered the ground with a cork board with a thickness of 10 cm, measured the temperature difference between the upper and lower sides of the cork board, and calculated the heat flux.
In 1924, Schmidt designed a strip heat flow sensor composed of thermopiles wound on rubber belts, which was used to measure the heat flow density of pipes with insulation layers. It is generally believed that this is the first practical heat flow sensor. At present, the widely used thermal resistance heat flow sensor has always followed the basic type of thermopile sensor. The thermopile on Schmidt heat flow sensor is made by welding, and the process is complicated. In 1939, in order to overcome the difficulty of making multipoint thermopiles, Gier and Boelter made thermopiles (or wire-wound thermal resistors) for heat flow sensors by silver plating on constantan wire. In the future, this method will be gradually extended to make various heat flow sensors. The problem of low accuracy of this kind of wire-wound thermal resistance heat flow sensor is that only two ends of a strip are in contact, so it can't be standardized, and each circle can't be flat, and one probe has hundreds of turns, which makes each probe vary widely. In addition, the coil must be bare wire for electroplating, so it is easy to touch the wire in the manufacturing process, thus changing the performance, requiring multi-point series welding between coils, and the solder joints are different and there are many solder joints. Due to the structural form and processing method, the performance of each sensor is very discrete In order to ensure the linearity of each sensor, high precision, narrow measuring range and wide temperature range are required.
Because it is made by hand, the consistency (line length, resistance, capacitance, inductance, etc. ) is not very high, the resolution is low, especially on the basis of ensuring linearity, there can only be a very narrow range.
1969, with the demand of high-precision heat flow measurement, the thermopile, a sensitive element of semiconductor material heat flow sensor, is proposed. Thermopile is prepared on silicon film by using integrated circuit technology, diffusion and particle implantation, silicon epitaxy, anodic oxidation, porous silicon corrosion, physical or chemical vapor deposition of insulating medium and other technologies. This sensor has the characteristics of consistent line length, consistent resistance, capacitance and inductance, so it has high sensitivity, measuring range and working temperature range. It provides an economical, practical and high-precision heat flow detection instrument for general fields.
Due to the adoption of semiconductor manufacturing technology, consistency (line length, resistance, capacitance, inductance, etc. ) and the performance of each heat flow sensor (such as working temperature, measuring range, resolution and response time) have been greatly improved, especially it can have good linearity in a large measuring range.
In 2002, the thin film heat flow sensor with higher measurement accuracy appeared, which met the needs of higher precision measurement in aerospace and military science and made it possible to measure small thermal changes. It is a new patent (EU patent: PCT/FR02/04033) technology: it is a device composed of metal sheets coated with low thermal conductivity and high thermal conductivity on both sides. One side of the coating material is irradiated by energy, while the back of the other side is covered with a thermal barrier. The energy flow difference of irradiation causes an electric potential energy, which is easy to produce a small current. This current is proportional to the energy flow.
Due to the adoption of new patented technology, the thin film heat flow sensor is very thin, with a typical thickness of 0.4mm；; Consistency (line length, resistance, capacitance, inductance, etc. ) and the performance of each heat flow sensor (such as range, resolution and response time) is higher, especially to ensure its good linearity in a large range; The typical response time is 25ms, so they can be used for transient measurement, such as unstable heat flow or detecting sudden radiation heat flow. Compared with traditional sensors, the ultra-thin thickness also makes them insensitive to air gaps when installed on the surface.
The above is the development process of thermal resistance heat flow sensor for measuring heat conduction.
In developed countries such as Europe and America, wire-wound thermal resistance heat flow sensor has been replaced by semiconductor thermopile heat flow sensor and thin film heat flow sensor with higher performance. Schmidt Boelter and other forms of radiant heat flow meters are gradually being replaced by radiant heat flow sensors composed of fast response thin film heat flow sensors. The Garden heat flow sensor used for high-speed transient rapid measurement (10 ~ 20 ms) has been used up to now. This is because the response time of the latest fast response thin film heat flow sensor can not exceed 20 ms
The display instrument of heat flow meter has developed from millivoltmeter and digital voltmeter to high-precision data recorder and data acquisition system. The circular foil radiation heat flux sensor for rapid transient measurement (10 ~ 20 ms) has been manufactured and used in China's military enterprises.
In the early 1980s, in order to meet the needs of China's energy-saving work, the State Investment and Beijing Institute of Automation Technology (now Beijing Institute of Automation Technology) undertook the imitation of the HFM- 10 1 and HFM-15 heat flow meters and supporting wire wound heat flow sensors of Showa Electric Company of Japan. The domestic model is CHF, which has been produced and sold so far.
In recent years, some domestic research institutes have developed thin-film heat flow sensors and achieved success, but it is a pity that they have not been industrialized so far.