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The existing Chinese solar greenhouse (CSG) had different spatial structure types, which spatial structure can make the greenhouse fully utilize solar energy and obtain the best thermal performance effect is worthy of further research. This paper took the CSG in the Shenyang area as the research object. A mathematical model was established to simulate the three-dimensional dynamic thermal environment of CSG at the crop level by combining experimental and computational fluid dynamics (CFD) numerical simulation. The model can well describe the heat transfer process in the greenhouse. Based on this model, the effects of variation of multiple structural parameters on the temperature distribution, solar energy interception, heat storage and release performance of CSG were quantitatively specified. The simulation results demonstrated that for the CSG with a span of 10 m in the Shenyang area, the optimal ridge height was 6.2 m, the optimal north wall height was 4.4 m and the optimal horizontal projection length of the north roof was 2.0 m. Furthermore, the spatial structure parameters of CSG with an 8 m–12 m span were obtained for the Shenyang area. This paper can provide theoretical guidance for the design and optimization of spatial structure parameters of CSG in the Shenyang area. • A CFD model was established to simulate the thermal environment of crop level in CSG. • The CFD model can accurately depict the dynamic heat and mass exchange process in CSG. • The effect of structural parameters on the thermal environment of CSG was expounded. • The structural parameters of CSG with 8 m–12 m span were obtained for the Shenyang area. [ABSTRACT FROM AUTHOR]

Abstract This paper aimed to develop a computational fluid dynamics simulation for an industrial boiler. The industrial boiler is used for the sulfuric acid production. A numerical model is carried out using the commercial code "ANSYS-FLUENT". The simulations are developed for the case of the industrial boiler and a new proposed design. A clear understanding of the combustion phenomenon and the fluid flow within the boiler is provided from the simulations. The local characteristics of the fluid flow and the heat transfer such as the temperature; the velocity magnitude and the density distributions are presented and analyzed. The comparison between the numerical results and the experimental data is performed and a good agreement is found. Highlights • A numerical simulation is developed for an industrial boiler. • The fluid flow and the heat transfer characteristics are analyzed and discussed. • The numerical model is validated by comparison between numerical results and industrial measurements. [ABSTRACT FROM AUTHOR]

The project reported in this paper used CFD as a tool to investigate the effect of multi-pass on the shell side heat transfer of a heat exchanger system. The heat exchanger system is equipped with six vertical thermosyphons transferring thermal energy from a heat source (air) to a heat sink (water). The CFD model has been experimentally validated. The two-phase change processes inside the thermosyphons were not modelled during the simulation. Instead, the thermosyphons were treated as solid rods with a constant thermal conductivity, which was calculated theoretically by applying the thermal resistance analogy with the aid of convection, boiling and condensation correlations found in the literature. The heat source consists of multiple air passes on the evaporator section of the thermosyphons and two water passes on the condenser section. Three different arrangements on the evaporator section were investigated with one, two or three shell passes and the thermal performance compared for the three configurations. The investigation was performed at various inlet conditions: a range of air inlet temperatures (100, 150, 200 and 250 °C) and mass flow rates (0.05, 0.08, 0.11 and 0.14 kg/s). The water inlet conditions were kept constant (a temperature of 15 °C and a mass flow rate of 0.08 kg/s). The overall rate of heat transfer was obtained by both CFD and a theoretical model, and the results lay within 15% of the experimental data. The numerical predictions demonstrated that the k − ε Realizable turbulence model is a reliable tool for predicting heat transfer and fluid flow in such heat exchangers. [ABSTRACT FROM AUTHOR]

Abstract: The present paper describes the application of computational fluid-dynamics (CFD) to the design and characterization of a medium scale energy storage unit for district heating systems. The shell-and-tube LHTES unit contains a technical grade paraffin (RT100) as phase change material (PCM) and uses water as heat transfer fluid (HTF). The system has been designed to transfer heat from the district to the building heating networks. After an initial description of the LHTES unit and a wide literature overview on the subject, the paper discusses the need for thermal enhancement to improve the thermal conductivity of the PCM. A solution based on a paraffin-graphite composite with a 15% graphite volume fraction has been found to be well performing in this particular application. Several operating scenarios characterized by heat requests ranging between 130 kW and 400 kW have been explored and the main outputs presented as function of Re and St numbers. The timewise variations of other significant quantities such as liquid fraction, sensible and latent energy content, HFT outlet temperature and heat fluxes have been also presented and discussed. A final discussion on the possible system configurations shows that in comparison to traditional water storage systems for district heating, LHTES systems provide, depending on the chose alternative, higher energy storage densities. [Copyright &y& Elsevier]

Abstract: Combustion of pulverized coal in oxy-combustion technology is one of the effective ways to reduce the emission of greenhouse gases into the atmosphere. The process of transition from conventional combustion in air to the oxy-combustion technology, however, requires a thorough investigations of the phenomena occurring during the combustion process, that can be greatly supported by numerical modeling. The paper presents the results of numerical simulations of pulverized coal combustion process in swirl burner using RANS (Reynolds-averaged Navier–Stokes equations) and LES (large Eddy simulation) methods for turbulent flow. Numerical simulations have been performed for the oxyfuel test facility located at the Institute of Heat and Mass Transfer at RWTH Aachen University. Detailed analysis of the flow field inside the combustion chamber for cold flow and for the flow with combustion using different numerical methods for turbulent flows have been done. Comparison of the air and oxy-coal combustion process for pulverized coal shows significant differences in temperature, especially close to the burner exit. Additionally the influence of the combustion model on the results has been shown for oxy-combustion test case. [Copyright &y& Elsevier]

The paper presents a numerical study of a heat transfer process realized in a three draughts low power heating boiler for solid fuels combustion equipped with an afterburning chamber. The main reason for the proposed research is to define the character of an exhaust gas flow through the special construction of heating device at different levels of the heat loading. Heating boiler construction allows for dividing stream of the flue gases into two separated streams. One part of the stream is transferred directly to the afterburning chamber and omits first two draughts of the heating boiler, where the rest of exhausts is directed to. Authors simulated the limitation of exhaust streams division into the afterburning chamber in order optimize the heat transfer process. Obtained results showed that the character of exhaust gas flow strongly depends on the amount of heating power of the heating device. Changes in exhaust gas flow caused increasing of heating power obtained for the nominal load by 4.2%. Similar effect was not visible during heating boiler work with minimal level of the heat load. [ABSTRACT FROM AUTHOR]