Fire pump bearing box heating temperature different reasons

In order to find out the cause of the fire pump bearing box different heating temperature, through the numerical calculation of heat transfer, volume loss is the main factors influencing the degree of hot pump bearing box transfer case. As a result, the structure size is improved. In running a large fire pump in the process of bearing box, usually the temperature of the heated to above 70 oc. High temperature will affect the performance of the lubricating oil. Tests show that even with a batch of bearing products manufacturers, the highest temperature is high and low, by changing the bearing model, adjust the installation of radial thrust bearing clearance, unable to control temperature. Therefore, the temperature of the root causes of uncertainty that need to be found and effective control. Through numerical calculation of bearing the conjugate heat transfer of heat transfer in the oven, CHT） Find out the main cause of overheating. Conjugate heat transfer problems calculation area can be divided into two, namely the fluid filling zone and solid zone. In the process of energy transfer between two regions through the diffusion process. The finite element method ( 有限元法) Very suitable for the pure solid heat transfer problems in discrete calculation method. Based on the finite element of finite volume method ( 有限体积法) The conjugate heat transfer problem involving fluid is more effective. In this paper, the finite volume method. 1, the heat transfer calculation results computing grid model, ignoring the oil in the tank to the influence of heat transfer and heat transfer to the influence of the air density difference. This problem is one of the axisymmetric problem, so a sector can be calculated, in which a and b is the installation position of bearing, wire frame for water, the rest for the housing and shaft, box, contact part of the air shaft and air convection heat transfer boundary. 2 is calculated as a result, the warm color is high temperature, cool color is low temperature. Although the computer has a strong ability of calculation and analysis, but the actual engineering problem is complicated, sometimes related calculation parameters also have some similarities. The accuracy of calculation, should fully understand in the calculation. Based on the analysis of calculation results, the attention should be paid to the influence of the boundary conditions of uncertainty. Heat transfer calculation in bearing box, water convective heat transfer is caused by the pump volume losses forced convection heat transfer. The heat transfer coefficient associated with the volume loss of the pump, should be controlled by design. Size of the manufacturing process, however, changes in uncertainty of volume loss, lead to the uncertainty of convective heat transfer coefficient of water. Calculation shows that heat transfer coefficient changed a lot. For fire pump speed is greater than the ns = 76, when the volumetric efficiency between 90% to 98%, the heat transfer coefficient is equal to the flow, 390 w/m2oC ~ 1240 w/m2 ℃ range. Air convection heat transfer is a kind of natural convection heat transfer, the heat transfer coefficient and the environment of the pump, so the uncertainty. Considering the fire pump is usually installed in the indoor air flow rate change is not very big, so the heat transfer coefficient won't have too big change. If the wind speed from 0 to 6 m/s change. 4 / s, according to the empirical formula, the average heat transfer coefficient of air for 5 w/m2. OC to 25 W/m2 & deg; C water convection heat transfer coefficient is greater than air convection heat transfer coefficient, this is the main factors influencing the heat transfer, and forced convection heat transfer can be controlled by the designer. Therefore, as shown in figure 3, watching water convection heat transfer coefficient and the average air convection heat transfer coefficient of the two parameters, the influence of the see them on the result of calculation. As shown in figure 3 temperature is the highest temperature of bearing box, usually located close to leave bearing pump impeller. Single bearing heating power 1000 w, 20 oc ambient temperature. Thus, because the water change range of convective heat transfer coefficient is bigger than the average range of air convection heat transfer coefficient, so water convection influence the highest temperature of bearing box. Effective temperature control measures in order to control temperature can reduce the volumetric efficiency, if the highest temperature is not higher than 70 oc, so water convection heat transfer coefficient should not be less than 500 ℃ w/m2, and calculate the volumetric efficiency of pump and the corresponding parts size.