A Study on Manufacturing Technique and Alloy Characteristics of Bronze Mirrors from Jeollanam-do Region in the Three Kingdoms Period

This study analyzed the microstructures and chemical composition of three samples of bronze mirrors excavated in the Jeollanam-do region, particularly Goheung and Damyang. Under x-ray irradiation, the analysis results confirmed the broken parts and pores caused by cracks, casting, and corrosion. Major and minor elemental analysis were performed on three mirrors by Scanning electron microscopy (SEM) with Energy dispersive x-ray spectrometry (EDS) and Inductively coupled plasma mass spe ctrome try (ICP-MS). The re sult shows that the bronze mirrors containe d Cu-Sn-Pb alloys. Alpha phase and eutectic phase were observed in the microstructure, confirming that the casting was performed without additional heat treatment. Notably, Three bronze mirrors were made early Three Kingdoms period in Korea.

Thermo-elastostatic analyzes of new dampers made of polymer springs with negative thermal expansion

The article presents original results of research of the dampers with passive and semi-active damping using polymer springs (also artificial muscles or nylon springs) with negative thermal expansion. Passive damping can be ensured by the strong damping effects of polymer springs. Semi-active damping can be provided by heating the springs from an additional heat source. According to design such dampers, mathematical models for analytical elastostatic and thermoelastostatic analyzes of dampers for selected load cases are processed in the paper. The permissible values of mechanical and thermal load of the dampers are determined. The obtained results are verified by numerical analysis using the finite element method. The elastostatics of the passive damper and its damping functionality have been verified on a real model of the damper. The compiled mathematical models can be used in the design of polymer dampers as well as in their automatic control. Designed and analysed dampers can be used in smaller mobile or stationary systems such as scooters, small car kits and the like. The elastodynamic functionality of the dampers with passive and semiactive damping will be presented and discussed in our further paper.

Simplified Infinite Fin Method to Model the Heat Transfer Associated with Slab Edges and Balconies

As building codes become more stringent in terms of thermal performance of building envelopes, and higher insulated wall assemblies are becoming more common, the heat flow due to major thermal bridges can contribute to a significant portion of the total heat transfer through a building façade. Characterizing different thermal bridging elements is essential not only to capture the thermal resistance of wall assemblies and understand the thermal efficiency of buildings, but also in terms of understanding the impact of each thermal bridging element and mitigation strategies that can be used. Numerical simulations are used widely to characterize different thermal bridging elements. However, not all designers have access, technical skills or time to complete numerical simulations to calculate the heat transfer loss through thermal bridges. In this study we propose an analytical method to integrate the effect of adding a slab edge/balcony/eyebrow into a clear-field wall assembly. The additional heat transfer due to the slab edge is calculated by considering the slab edge to be an infinite fin. The additional heat transfer is integrated into the clear-field as a quasi-convective heat transfer coefficient. The overall thermal resistance of the wall assembly is calculated by employing the parallel path method. Comparing the results obtained from this method with the numerical simulations which were benchmarked against guarded hot box results, an overall deviation of 1 to 8 percent was observed.

The additional heat flux due to adhesion at a partially immersed rotating drum heat exchanger for latent heat storage

Latent heat storages can be used to store thermal energy at a constant temperature. By actively removing the solidified phase change material from the heat exchanger surface during the discharge process, the heat flux can be kept constant and a separation of power and capacity is possible. In the presented rotating drum concept, a cooled drum is partially immersed in a tub of liquid phase change material and rotates in it. Phase change material solidifies at the submerged part of the drum. In addition, adhering liquid phase change material solidifies after the surface has left the tub. In this paper, the additional heat transfer due to adhesion is examined by determining the solidified layer thickness as well as the heat transfer by comparing measurements with adhesion and while eliminating the adhesion with a rubber lip. The measured adhering layer thickness differs by 33% from a presented analytical approach. The transferred heat is increased up to 26 % due to the adhesion.

PROVIDING THERMAL COMFORT OF THE DISTAL SEGMENTS OF THE LOWER LIMBS BY USING AN AUTONOMOUS ELECTRIC HEATING SYSTEM

Introduction. Work in low temperatures can lead to both general and local cooling of the human body. Local cooling of the distal parts of the legs can limit the motor activity of the employee even with sufficient thermal insulation of the body general surface. Therefore, the use of an additional heat source in special shoes (autonomous electric heating system (AEHS)) can compensate heat losses in the distal parts of the legs and provide thermal comfort in conditions of low temperatures throughout the work. The purpose of the study: physiological and hygienic assessment of the additional heat sources (AEHS) influence on the thermal insulation of special shoes in conditions of low temperatures. Materials and methods. To assess the heat-protective properties of the special shoes experimental sample with an AEHS, a heat flux density and skin temperature meter ITP-MG 4.03/30 "POTOK" (LLC SKB Stroypribor, Chelyabinsk) was used. The presented sample was tested with the participation of 5 volunteers in three modes of autonomous electric heating in a microclimatic chamber for 60 minutes for each mode separately. The average air temperature in the chamber during the study was 2.5±0.5 °C. Based on the obtained data, the thermal insulation of special shoes with an AEHS was calculated. Results. The thermal insulation of the special shoes experimental sample without electric heating was 0.460±0.013 °C m2/W; and 0.512±0.01 and 0.549±0.01 °C m2/W using the minimum and medium electric heating modes-, respectively, which allows us to recommend the presented sample of special shoes with an autonomous electric heating system for work in a "Special" climatic zone when performing moderate-severity work. The thermal insulation of a special shoes sample with the maximum electric heating mode was 0.615±0.01 °C m2/W, which makes it possible to work with it in the IV climatic zone. Conclusions. The use of an AEHS increases the thermal insulation of special shoes, which provides sufficient protection for the distal parts of the legs, allows to expand the scope of its operation in strict compliance with the work and rest regime and can be a prevention of the occupational diseases development in workers at low temperatures.

Thermoelectric building temperature control: a potential assessment

This study focuses on thermoelectric elements (TEE) as an alternative for room temperature control. TEE are semi-conductor devices that can provide heating and cooling via a heat pump effect without direct noise emissions and no refrigerant use. An efficiency evaluation of the optimal operating mode is carried out for different numbers of TEE, ambient temperatures, and heating loads. The influence of an additional heat recovery unit on system efficiency and an unevenly distributed heating demand are examined. The results show that TEE can provide heat at a coefficient of performance (COP) greater than one especially for small heating demands and high ambient temperatures. The efficiency increases with the number of elements in the system and is subject to economies of scale. The best COP exceeds six at optimal operating conditions. An additional heat recovery unit proves beneficial for low ambient temperatures and systems with few TEE. It makes COPs above one possible at ambient temperatures below 0 $$^\circ $$ ∘ C. The effect increases efficiency by maximal 0.81 (from 1.90 to 2.71) at ambient temperature 5 K below room temperature and heating demand $$\dot{Q}_h={100} W$$ Q ˙ h = 100 W but is subject to diseconomies of scale. Thermoelectric technology is a valuable option for electricity-based heat supply and can provide cooling and ventilation functions. A careful system design as well as an additional heat recovery unit significantly benefits the performance. This makes TEE superior to direct current heating systems and competitive to heat pumps for small scale applications with focus on avoiding noise and harmful refrigerants.

The Grell–Freitas (GF) convection parameterization: recent developments, extensions, and applications

Recent developments and options in the GF (Grell and Freitas, 2014; Freitas et al., 2018) convection parameterization are presented. The parameterization has been expanded to a trimodal spectral size to simulate three convection modes: shallow, congestus, and deep. In contrast to usual entrainment and detrainment assumptions, we assume that beta functions (BFs), commonly applied to represent probability density functions (PDFs), can be used to characterize the vertical mass flux profiles for the three modes and use the BFs to derive entrainment and detrainment rates. We also added a new closure for nonequilibrium convection that improved the simulation of the diurnal cycle of convection, with a better representation of the transition from shallow to deep convection regimes over land. The transport of chemical constituents (including wet deposition) can be treated inside the GF scheme. The tracer transport is handled in flux form and is mass-conserving. Finally, the cloud microphysics have been extended to include the ice phase to simulate the conversion from liquid water to ice in updrafts with resulting additional heat release and the melting from snow to rain.

Thermally Induced Reduction of Hot Cracking Susceptibility in Electron Beam Welding of CuCr1Zr: A Numerical Approach

Electron Beam Welding (EBW) is a highly effective and accurate welding process that is being increasingly used in industrial work and is of growing importance in manufacturing. In the current study, solidification cracking in EBW of a CuCr1Zr cylindrical geometry was explored. To investigate and prevent occurrence of hot cracking, a thermomechanically coupled numerical model was developed using Finite Element Method (FEM). An additional heat source was considered, in order to influence the resulting residual stress state, namely to minimize tensile stresses in the fusion zone during solidification. Hence, a methodical assessment of relevant parameters, such as the power, the diameter of the additional heat source and the distances between both heat sources was employed using Design of Experiments (DoE). It was found that for a particular parameter configuration, solidification cracking most likely could be averted.

Experimental study on the backdraft phenomenon of solid fuel

In this study, a series of small-scale experiments were conducted to investigate the backdraft phenomenon in a compartment (1.1 × 0.4 × 0.75 m) with woodblocks as fuel. This research focused on the effects of compartment window woodblock areas on backdraft time, with a video recording of the experimental phenomena. Thermocouples and a gas analyzer were used to measure the temperature and the concentration of gas components in the compartment, respectively. There was no additional heat source or ignition source pre-set in the compartment at the beginning of the experiments; the experimental processes only depended on the heat released from the burning or smoldering of woodblocks. When compartment ventilation improved, smoldering of woodblocks became intense, and backdraft occurred. The results show that backdraft time is shorten with increases of compartment window and woodblock areas, and opening the upper window of a compartment could avoid the backdraft phenomenon. The results help to understand the backdraft phenomenon of solid fuel and, more importantly, could help firefighters adopt reasonable fire-fighting strategies for restraining backdraft occurrence.