Application of microwave drying wood
It is an important means to ensure the quality of wood products by drying wood with a certain moisture content. Therefore, in the 1970s, China began to study the use of microwave drying equipment, drying before use.
At present, wood microwave equipment is generally used.
In 1977, Shanghai Changzheng Wood Products Factory and the former Northeast Forestry College developed a tunnel wood microwave dryer which heated the wood from the outside with hot air and made its surface water evaporate 915 MHz, regardless of the heat source, such as the assistance of the relevant units. The formation of surface and internal moisture content gradient leads to the drying test of water from inside to outside.
At that time, the H.Resch of Japan and Yoshida Maya of the United States spread to dry wood. If the surface evaporation rate is balanced with the internal and W.R.Mcalister diffusion rates, the wood is heated uniformly, the temperature and humidity are appropriate, and the wood is irradiated continuously or intermittently, resulting in internal cracks and deformations, and the wood can be quickly dried. Therefore, in order to inhibit the initial stage of wood drying, it is necessary to repeat the drying process. Desiccation dozens of times, the actual production can not be used, but their surface moisture diffusion, should be high temperature and humidity method to increase the heat conduction system are fully affirmed: if can solve the microwave heating uniformity, so that the number of wood, but because of the poor thermal conductivity of wood itself, this method is difficult to achieve wood in a few hours, rather than a few minutes of time. Drying can solve the problem of internal cracking of wood drying.
This rapid drying method: 1. Select the tensile strength of o-45 steel tubing, take = 580 MPa according to the flow and pressure check manual, choose No. 45 seamless steel tubing, in the above calculation of wall thickness is generally very small, taking into account the actual structure of the need for frequent work activities, choose the standard HC-406-75 two-layer steel wire to check (JB1068-67), according to the calculation of 6 swing cylinder, internal diameter. Take the braided pipe and calculate: suction pipe diameter d, = 14.72 mm; pressure pipe 4cm, external diameter 5cm, piston rod diameter 1.6 m pipe diameter d = 9.31 mm; return pipe diameter d, = 12.0 mm; pressure oil pump outlet pressure P pipe wall thickness, = 0.29 mmP = P + 2P = 6.3 + 0.5 = 6.8 MPa check manual, choose (YB231-70) 45 cold-drawn steel pipe, the calculation formula: 2P for the system pressure loss, take P = 0.21 MPa 5 MPa pipe diameter roundness for the standard diameter, take the suction pipe diameter of 14 mm, pressure pipe 4 pump outlet flow Q diameter of 10 mm return pipe diameter of 12 mm Q 2 = KQ = 1.2 X 0.78 = 9.36 L / min auxiliary calculation can be carried out according to the method in the hydraulic design manual: K - leakage coefficient, take K = 1.2