What Factors Affect the Price of Wire Mesh?

The wire mesh regenerator is a typical porous medium, which is formed by forming and stacking the wire mesh sheet first. The metal wire mesh has excellent heat exchange and flow properties, and is easy to manufacture and inexpensive, thus becoming the filler of the heat regenerator Preferred material.

The wire mesh regenerator is a typical porous medium. It is formed by wire mesh sheets first being stacked, and is generally cut into circular shapes by wire cutting or die. Its advantages are relatively convenient filling, low cost and simple processing. Due to the good lateral thermal conductivity of the metal mesh and the randomness of the processing and filling process, the metal wires are staggered with each other, resulting in large flow resistance. In low-frequency thermoacoustic systems, we usually use screen-stacked regenerators, but in high-frequency systems, cluttered screens can cause large gas resistance at the regenerator, so other types of regenerative heat are generally used. Device. ^[1]

(1) Regenerator packing

For wire mesh regenerators, the choice of filler and the way of filling are diversified. The numerical simulation method is an effective method to study the flow and heat transfer in porous media, but the physical model of the wire mesh is not easy to establish, which brings some difficulties to the analysis. The heat transfer performance of the regenerator is greatly affected by the physical properties of the wire mesh, the flow resistance in the regenerator, the heat exchange surface area, and the surface heat transfer coefficient. The above factors are related to the mesh number, wire diameter and The materials are closely related. ^[3]

Screen regenerator regenerative low temperature refrigerator

In order to ensure that the heat stored in the filler during the cold blowing period of the regenerator can be transferred from the inside to the surface and from the edge of the gas flow channel to the center of the flow channel, the heat in the gas can be transferred from the center of the air flow channel during the hot blowing period. Handed to the edge of the flow channel, and transferred from the surface of the regenerative packing to the interior, the selection of the regenerator packing and the filling structure should meet the following conditions:

(1) The volume specific heat capacity of the regenerator packing is much larger than that of the working gas;

(2) The equivalent diameter of the flow path of the filler of the regenerator should be smaller than the depth of thermal penetration of the working gas to ensure sufficient heat exchange between the gas and the filler. However, the equivalent diameter of the flow channel should not be too small, too small will increase the flow resistance of the regenerator and affect the performance of the refrigerator. That is, the thermal penetration depth and viscous penetration depth of the working gas operating at a specific frequency jointly determine the upper and lower limits of the equivalent diameter of the pore channel of the regenerator packing;

(3) The equivalent diameter of the regenerator packing should be less than the thermal penetration depth close to the packing. The thermophysical and hydraulic characteristics of the regenerator have a decisive influence on the efficiency of the regenerator. Therefore, the regenerator packing is required to have characteristics such as large specific surface area, high specific heat capacity, low thermal conductivity, small hydraulic diameter, and low flow resistance. At present, the pulse tube refrigerator regenerator packing mostly uses metal materials, mainly stainless steel, lead, copper or copper alloy, magnetic cold storage materials, etc., the common types are also mostly concentrated in wire mesh, fiber, spherical, slit coil, Plate-like and so on. With the development of science and technology, some non-metal materials are also gradually used as fillers in regenerators in engineering. ^[2]

The wire mesh regenerators with different mesh numbers and wire diameters and different physical properties are used as objects. The heat transfer performance of the regenerators can be measured by using multiple index parameters such as specific heat capacity, axial thermal conductivity, regenerative efficiency and comprehensive performance parameters. Optimization, we get the following conclusions:

(1) Optimization based on available specific heat capacity. The larger the specific heat capacity and density of the regenerator packing, the larger the available specific heat capacity, the larger the cooling capacity; when the available specific heat capacity is the same, the cooling capacity with a large thermal penetration depth is small; the available specific heat capacity also increases with the increase in radial thermal conductivity Large, but the cooling capacity is reduced accordingly. Therefore, the regenerator filler should choose a material with a large specific heat capacity and density and a relatively low thermal conductivity to improve the comprehensive heat exchange capacity of the regenerator.

(2) Optimization based on axial thermal conductivity. When the axial radial thermal conductivity a is set to 0.1, the refrigerating capacity of the refrigerator is 0.5 to 2.0 W higher than that when the regenerator is treated isotropically. It can be seen that the refrigerating capacity calculated by considering non-isotropic factors in the general model will be partial Small, choose a relatively low thermal conductivity of the filler material or by changing the screen filling method (such as the insulation between the screen pieces) to reduce the radial heat transfer ratio of the regenerator shaft, can reduce axial heat leakage.

(3) Optimization based on heat recovery efficiency and comprehensive performance parameters. By controlling the filling ratio of different mesh screens (such as 75% 200 mesh at the hot end and 25% 250 mesh at the cold end), and the cold end is a multi-stage regenerator with a stainless steel mesh with low thermal conductivity, its heat recovery efficiency and The comprehensive performance parameters can all be improved, so as to obtain a better heat transfer effect. ^[3]

Wire mesh regenerator thermoacoustic regenerator

Because the specific surface area and thermal conductivity of the filler have different effects on the heat loss and the overall efficiency of the regenerator, the performance of the multi-segment wire mesh regenerator has a higher overall efficiency than the single-stage regenerator. Selecting a wire mesh with a lower particle size at the hot end and using a filler with lower thermal conductivity at the cold end can greatly improve the heat transfer efficiency of the regenerator. ^[4]

Experimental research by Qiu Limin, Jiang Ning, Chen Guobang, etc. of Zhejiang University found that the optimal filling rate of the wire mesh regenerator is 1.15 pieces / mm. In addition, a variety of combinations of different wire diameters, different meshes, and different screen materials are used. The greater the comprehensive parameter of the regenerator, the better the effect. Gao Fan, He Yaling and others from Xi'an Jiaotong University have better thermal acoustics by using a wire mesh heat exchanger with a lower thermal conductivity. For general wire mesh regenerators, the filling rate can be changed by increasing each wire mesh. The gap between them reduces the axial heat conduction of the regenerator and guarantees the temperature gradient at both ends of the regenerator, so that the thermoacoustic conversion efficiency is better. ^[1]

Under the same inflation pressure and heating power, the pressure ratio achieved by the thermoacoustic heater of the plate stack regenerator is the highest, the ceramic regenerator is the lowest, and the screen regenerator is between the same. Easy start-up, that is, the lowest start-up temperature is required, followed by plate stack reheaters, and honeycomb ceramics are more difficult to start-up. Taking a plate stack recuperator as an example, the thermoacoustic system starts to vibrate at , and the temperature difference between the vibrations is about , which is feasible for the use of heat sources such as low and medium temperature waste heat in industry. ^[1]