So far, there has been a little imperfection in the analytical theory of radiation heat transfer. Although there is a calculation formula for non-transparent bodies, more universal calculation formulae for partially transparent bodies have not yet been found.

Today, various types of plastic films are most commonly used to cover greenhouses. However, plastic films are partially transparent to long-wave thermal radiation. Up to now, the radiation heat transfer in the buildings like solar greenhouses has been analyzed using the repeated reflection method.

Preceding authors calculated the radiation heat transfer of radiation systems containing partially transparent bodies such as glasses or films by using different methods, but they did not perform detailed quantitative and qualitative analyses of radiation components when radiation passes through partially transparent bodies. Also, the number of determinants increased considerably because different studies developed formulae with individual radiation components. Therefore, only computer-based calculations were able to determine heat fluxes of resultant radiation or transmission radiation, and some calculation time was required. Furthermore, studies on the determination of radiation heat fluxes using the multiple reflection method and the ray tracing method were more complex than using the effective radiation method. Introduction of computers into technical calculations enabled calculation of radiation heat fluxes in greenhouses by the repeated reflection method, but programming also required a lot of effort. In a word, it was more complex and less intuitive than the effective radiation method.

Kim Chol Gon, a researcher at the Faculty of Thermal Engineering, derived universalized formulae to briefly and explicitly calculate radiation heat fluxes in radiation systems with partially transparent bodies including solar greenhouses and solar collectors, using the effective radiation method (i.e., the radiosity method). Then, he proved that calculated characteristics of the daily temperature variation in a single-roofed solar plastic film greenhouse by using derived formulae are the same as those calculated by using the repeated reflection method.

These formulae can be fully applied to calculating radiation heat fluxes in all radiation systems with partially transparent bodies such as solar greenhouses and solar collectors. They can also be effectively applied to radiation heat calculations of public houses and buildings with windows.

For more information, please refer to his paper “The formula for calculating radiative heat fluxes in systems with partially transparent structures” in “Thermal Engineering” (SCOPUS).

Soda ash, one of the most important basic chemical raw materials, is widely used in chemicals, detergent and soap, petrochemical, pulp and paper, glass, metal, ceramic and food industries. Soda ash is mainly produced from natural trona and other sodium carbonate-containing minerals, in addition to the ammonia-soda and ammonium sulfate-soda methods. In the production of soda ash based on mirabilite, the ammonium sulfate-soda method is considered the most suitable one because of its high utilization degree of mirabilite, low energy consumption, and production of ammonium sulfate as a byproduct.

The depletion of nonrenewable energy resources and the high cost associated with it have made energy conservation and more efficient use of energy an urgent matter. Consequently, it is important to find a way of reducing energy consumption in the production of soda ash.

The solution is exergy analysis, which helps understand the energy distribution, detect the location of energy consumption and provide a direction for energy saving of a system.

The difficulty in exergy analysis of electrolyte systems is to accurately estimate the chemical exergy of substances or species involved in aqueous electrolyte solution. Furthermore, as for the soda ash production process by the ammonium sulfate-soda method, the gas-liquid reaction and salt precipitation reaction occur simultaneously in the Na₂SO₄-NH₃-CO₂-H₂O electrolyte system, so exergy analysis cannot be carried out using the chemical exergy of elements and substances presented by preceding researchers.

Pak Kyong Song, a researcher at the Faculty of Chemical Engineering, has proposed a novel approach to calculate the chemical exergy of an aqueous electrolyte system accompanied by gas-liquid reaction and salt precipitation reaction, based on the Pitzer equation.

He simulated a soda ash production process using Aspen Plus and performed an exergy analysis based on the thermodynamic data obtained from the simulation.

The result showed that the exergy destruction of the entire process is 99.945kW and exergy efficiency is 59.57%. In addition, he found that the units with low exergy efficiency in the process are condenser and absorption towers such as NH₃ absorption tower, carbonation tower and water washing tower, which are the primary targets of energy saving.

For more details, you can refer to his paper “Study on Exergy Analysis of the Soda Ash Production Process by the Ammonium Sulfate-Soda Method” in “ACS Omega” (SCI).

In general, FGM structures are subjected to various external excitations such as earthquakes, winds, thermal load and jet noise in their operation. Therefore, studying the dynamic behavior of composite structures under different types of external load is considered an important task.

Kim Jin Mi, a student at the Faculty of Mechanical Science and Technology, analyzed the free vibration and stationary stochastic response of functionally graded (FG) rectangular plates with varying thickness in supersonic flow and thermal environment.

She investigated two types of material property variations of FG plates with varying thickness: variations along the direction perpendicular to the mid-surface and the bottom surface.

Considering the effects of aerodynamic pressure and thermal load, she derived governing equations of motion of FG plates with varying thickness using Hamilton’s principle within the framework of first-order shear deformation theory. Then, she constructed a meshfree Jacobi radial point interpolation (Jacobi-RPI) shape function by combining the Jacobi polynomials and radial basis to approximate the displacement components of the plate.

She confirmed the accuracy and reliability of the proposed approach through sufficient comparisons with numerical results from the published literature and the finite element software ABAQUS.

For more information, please refer to her paper “Meshfree Dynamic Analysis of Functionally Graded Rectangular Plates with Varying Thickness in Supersonic Flow and Thermal Environment” in “Acta Mechanica Solida Sinica” (SCI).