CHALLENGES AND METHODS IN ANALYZES OF THE HEAT TRANSFER IN POLYMER DRY BEARINGS

Heat generation and dissipation in dry polymer bearings are important aspects in their design and operation, because the overheating may lead to fast wear or product damage. The estimation of the maximum temperature under defined load conditions is crucial, but it is also a challenging task. Firstly, it is difficult to measure temperature directly at the contact surface between the bearing and the shaft. Secondly, thermocouples that are commonly used as the temperature sensors might create measurement errors. The work presented in this paper utilizes the numerical model of a polymer bearing for the analysis of the internal temperature field. The model is validated with use of experimental data; and, in order to mitigate the measurement errors of the thermocouple sensor, their geometry and properties are included in the simulation model. The achieved agreement between simulation and experimental temperatures is 10% on average, and it is judged that the numerical model may be applied for thermal analysis of the polymer bearing. The obtained results confirm the influence of the thermocouples with metallic sheaths on the temperature distribution inside the tested polymer bearing. It is shown that the value of the measurement errors depends on the layout of thermocouples and might be significantly reduced by their proper arrangement. It is believed that the presented approach for the analysis of thermal performance of dry polymer bearings might be applied to similar cases, which are characterized by large temperature gradients and require temperature sensors, that are made of the materials of high thermal conductivity.

Precise linear measurements using a calibrated reference workpiece without temperature measurements

We suggest a procedure for the correction of the errors caused by thermal expansion of a workpiece and the scale of a linear measuring instrument (coordinate measuring machines, length measuring machines, etc.) when linear measurements are performed at nonstandard temperature. We use a calibrated reference workpiece but do not require temperature measurements. An estimation of the measurement uncertainty and application examples are given.

A multi-channel cooling system for multiple heat source

High-power electronic devices with multiple heating elements often require temperature uniformity and operating within their functional temperature range for optimal performance. A multi-channel cooling experiment apparatus is developed for studying heat removal inside an electronic device with multiple heat sources. It mainly consists of a computer-controlled pump, a multi-channel heat sink for multi-zone cooling and the apparatus for measuring the temperature and pressure drop. The experimental results show the system and the designed multi-channel heat sink structure can control temperature distribution of electronic device with multiple heat sources by altering coolant flow rate.

Study on Improvement of Surface Temperature Uniformity by Bubble Stabilization in Flat-Plate Heat Pipe Hot Chuck

In the precision hot plate for wafer processing, the temperature uniformity of upper plate surface is one of the key factors affecting the quality of wafers. Precision hot plates require temperature variations less than ±1.5% during heating to 120°C. In this study, we have manufactured the flat plate heat pipe hot chuck of circle type (300mm) and investigated the operating characteristics of flat plate heat pipe hot chuck experimentally. Various screen mesh (40, 80, 120) were used as the structure and chamber was changed.

A High Temperature, Frequency Output Silicon Temperature Sensor

Precision high temperature sensors often require temperature compensation. Quartzdyne pressure transducers use a temperature sensitive quartz crystal for compensation. In an effort to shrink transducer packaging, and increase reliability; a prototype frequency output temperature sensor was designed using a 0.8um silicon bulk CMOS process. The 250°C operational sensor is based on a PTAT current generator. The design uses high temperature design techniques that were proven reliable in prior Quartzdyne ASIC's. The output frequency is 34kHz at 30°C, with a sensitivity of 100Hz/°C and achievable accuracy of ±0.3°C from 25°C to 200°C. This paper will review the sensor's characteristics, including the output linearity, hysteresis, accelerated aging and temperature cycling to demonstrate the performance and long term reliability and repeatability of the sensor.

A SHORT-TERM TEMPERATURE FORECASTER BASED ON A NOVEL RADIAL BASIS FUNCTIONS NEURAL NETWORK

Many applications dealing with electric load forecasting in buildings require temperature prediction. A new method for short-term temperature forecasting based on a Radial Basis Functions Neural Network, initialized by a Regression Tree, is presented. In this method, each terminal node of the tree contributes one hidden unit to the RBF network. The forecaster uses the current coded hour and the temperature as inputs, and predicts the next hour temperature. The results demonstrate this predictor can be used for load forecasting.