Prevent dry heating tube efficiency and general electric heat pipe that high?
First of all, the efficiency of heat pipe and the dry not too big relations
Efficiency and material factors such as electric heating tube, the use of 316 l stainless steel material, electric heating tube is relatively good
To introduce the following factors restricting the efficiency of the electric heating tube and improve method
Using 316 l stainless steel material, electric heating tube is relatively good
One of three factors, the material
The purity of 1, magnesium powder problem: magnesium oxide size directly determines the coefficient of thermal conductivity of sinter and purity, the greater the coefficient of thermal conductivity, the smaller the thermal resistance. The higher the heat transfer efficiency.
2, the density of magnesium powder problem: density by filling density, size shrinkage tube or plastic density to determine the density of electric heat pipe end. The greater the density value, the higher the heating efficiency, lower instead.
3, the selection of electric heat pipe pipe
(1) the selection method of pipe when choosing diameter must calculate correctly, namely through the area of the rate of change of compression ratio to estimate the final density electric heating tube whether meet the minimum requirement of 3.05 g/cm after, for example a phi 9.4 x 0.6 stainless steel tube, eventually into a tube for phi 8, try to demonstrate the feasibility of this scheme, the basic evaluation calculation is as follows:
(1) within the atc cross-sectional area S1 = 52.81 mm material squared
(2) pipe after forming sectional area S2 = material was 36.32
(3) tube area of compression ratio for A material of 0.688
In the process of filling, the collocation of magnesium powder particles and ideal equipment matching, in principle, guarantee of 2.35 g/cm after index can be achieved, and in the final 3.05 g/cm after minimum tube density index, the density of the added value of for: 1.297 times.
And through the area of compression ratio calculated A = 0.688, that area is reduced by 31.2%. Therefore, relative to the magnesium powder density increased by 31.2%, and the tube of the real density value theory of 2.35 x 131.2% = 2.35 g/cm after, so can judge this choice is right, of course, the above conclusion is correct shrinkage process of tube wall does not pull thin as before.
(2) magnesium powder mesh collocation and packing density
At present in the application of magnesium powder in the table, the basic particles in all the instructions are marked as the range of 40 ~ 325 mesh, all kinds of mesh proportion is not at the same time, its velocity is completely different results; In the process, is a manufacturer (magnesium powder) is tie-in, according to the proportion of actual use test data of basic problems of coarse sand and fine sand exceeds bid badly; Second, the product will appear in the process of long-distance transportation points of different mesh sand screen phenomenon, before use, such as not to mix and use directly into the powder storehouse, cannot ensure the velocity; Three is filling machine which we introduced in the process of shock will cause sand powder storehouse sieve, so why when operating the same tube has a big difference is that the filling weight for the above three factors, of course, factors influencing the velocity of except mesh match ratio, moistureproof agent wet sex is have a considerable effect on flow velocity, this also must be real time to the magnesium powder factory attention to a detail.
Second, the structure design
It is well known that spiral heat wire diameter to the metal shell inner wall of the greater the distance, its electrical insulating pressure value is high, but the heat transfer path increases, the increase of the path is concatenated in the heat transfer path a attenuator, inevitably led to a decline in heating efficiency, the existing drawbacks and shorten the creepage distance is a decline in the normal pressure value will be larger, the key now is how to evaluate electric heating efficiency is low and influence on electric heat pipe performance and eventually make trade-offs.
Heat wire per unit time heat is generated by a constant value, due to various factors led to the decrease of the heat transfer efficiency, and generate heat accumulation in the tube, once the phenomenon happens, in addition to accelerate moistureproof materials rapid carbonization, thermal state breakdown ratio will increase dramatically, and with the increase of temperature of the tube, pipe thermal fatigue procedures also exacerbate the decrease in the strength of a rigid, increase the rate of tube phenomenon is the result of a dangerous, the tube temperature increases, except CT effect led to the decrease of the on-line power will also lead to accelerated by increase working environment temperature of heat wire high temperature oxidation, so as to shorten the life of a series of problems, from the results of the author in this paper the above content, improve accuracy to ensure concentricity at the same time, in order to reduce creepage distance of improving the efficiency of electric power has very great realistic meaning, and it is the trend of The Times.
Above with magnesia as object describes the characteristics and creepage distance on the relationship between the electric heating efficiency, but in addition to the above content has a greater effect on heating efficiency, and the last part of the heat transfer path, namely the shell material, in addition to the wall thickness of thermal resistance are linked, but also pay attention to in the present thermal resistance of the big four applied materials from small to large the basic order of:
Copper to aluminum, iron, stainless steel, according to the actual permit conditions as far as possible with good thermal conductivity materials, this to improve the performance of electric heating efficiency and heating tube life have a certain role in promoting