Prediction of the Thermal Elongation of the Ball Screw Mechanism under Various Rotational Speeds

In numerical control machines, the thermal elongation of the ball screw influences the position accuracy. Different rotational speeds lead to different temperature changes at different positions in a ball screw system. In this paper, a new method is proposed to calculate the temperature rise of different positions when the ball screw is in the thermal equilibrium state. The thermal transmission of ball screws is analyzed, and the heat generation and transfer coefficient are calculated based on the laws of thermodynamics. The function between the temperature rise and position is built by solving the thermal equilibrium differential equations. The thermal elongation is obtained after the temperature rise is calculated. In order to prove the validity of this model, a series of detection tests are conducted to obtain the temperature rise of a ball screw and the thermal elongation under different rotational speeds. The experimental results show that the realistic temperature rise and the thermal elongation agree well with the theoretical values.

Utilization of updated version of heat flux model for the radiative flow of a non-Newtonian material under Joule heating: OHAM application

This study reports the thermal analysis and species transport to manifest non-Newtonian materials flowing over linear stretch sheets. The heat transfer phenomenon is presented by the Cattaneo–Christov definition of heat flux. Mass transportation is modeled using traditional Fick’s second law. In addition, the contribution of Joule heating and radiation to thermal transmission is also considered. Thermo-diffusion and diffusion-thermo are significant contributions involved in thermal transmission and species. The physical depiction of the scenario under consideration is modeled through the boundary layer approach. Similar analysis has been made to convert the PDE model system into the respective ODE. Then, the transformed physical expressions are calculated for momentum, thermal, and species transport within the boundary layer. The reported study is a novel contribution due to the combined comportment of thermal relaxation time, radiation, Joule heating, and thermo-diffusion, which are not yet explored. Several engineering systems are based on their applications and utilization.

A measurement system for the long-term diagnostics of the thermal and technical properties of wooden houses

<p class="Abstract"><span lang="EN-US">To reduce construction costs and to increase energy savings and indoor environmental quality in a wooden house, an energy consumption measuring system for the diagnostics of the thermal and technical properties of building envelopes has been developed. At present, the vast majority of calculations for the thermal and technical characteristics of buildings are based on simple mathematical models of building envelope behavior, and these are derived primarily from the thermal transmission of individual materials. However, thermal transmission is measured in a stable laboratory environment. Therefore, the measured values may not match the real behavior of materials in continually changing climatic conditions. The energy consumption measuring system was installed in seven wooden houses in different climatic areas to diagnose the thermal and technical properties of a building envelope. The power consumption, temperature, and humidity of the air as well as of the wood; CO₂ concentration; the temperature of the individual layers of the envelope sandwich structure; and wind speed and direction were measured. Thanks to the sets of real measurements of the measured thermal and technical behavior, the actual dependence of the indoor environment quality on the outdoor climatic conditions can be ascertained. The presented system can reveal imperfections in the heat capacity and hygroscopicity of materials used for the construction of a wooden house. Based on this measurement, the materials can be revised to save construction costs and energy; to increase the indoor environment quality; and to reduce the impact on the environment by decreasing the amount of used materials. </span></p>

EXPERIMENTAL STUDIES OF THERMAL TRANSMISSION THROUGH A MOBILE HEAT EXCHANGE SURFACE

Experimental studies of heat transfer in a heat exchanger of the "pipe-in-pipe" type with a rotating tube have been performed. It is established that in the investigated range of hot coolant flow rate, the rotation of the pipe makes it possible to increase the values of the heat transfer coefficients by 19-28%.