Analyzing impact of sensor coupling on measurement representativeness of wall surface temperature

Poor thermal-coupling between sensor and surface is one of the most important factors causing inaccuracy in measurement. Different methods had been suggested by scientists to solve this issue. Embedding the sensor into an object was one of these methods. The goal of these simulations was to assess the impact of sensor coupling on measurement representativeness of wall surface temperature. For this purpose, a cylindrically-shaped sensor was embedded into the internal surface of the wall assembly. The levels of tightness varied from 10% to 90%, which corresponded respectively from very loose to very tight conditions. Also, in this process the impact of other factors such size and materiality of the sensors’ accuracy were evaluated and discussed briefly. In this study, the results proved that as the sensor decoupled more from the surrounding environment, more accurate data was generated from it. Also, the results from the simulations signified the importance of the temperature difference between the wall surface and the indoor air temperature. The temperature difference had a direct relationship with sensor accuracy and measurement representativeness, where smaller temperature difference was associated with higher accuracy.

Analyzing impact of sensor coupling on measurement representativeness of wall surface temperature

Poor thermal-coupling between sensor and surface is one of the most important factors causing inaccuracy in measurement. Different methods had been suggested by scientists to solve this issue. Embedding the sensor into an object was one of these methods. The goal of these simulations was to assess the impact of sensor coupling on measurement representativeness of wall surface temperature. For this purpose, a cylindrically-shaped sensor was embedded into the internal surface of the wall assembly. The levels of tightness varied from 10% to 90%, which corresponded respectively from very loose to very tight conditions. Also, in this process the impact of other factors such size and materiality of the sensors’ accuracy were evaluated and discussed briefly. In this study, the results proved that as the sensor decoupled more from the surrounding environment, more accurate data was generated from it. Also, the results from the simulations signified the importance of the temperature difference between the wall surface and the indoor air temperature. The temperature difference had a direct relationship with sensor accuracy and measurement representativeness, where smaller temperature difference was associated with higher accuracy.

Validation of the PALM model system 6.0 in real urban environment; case study of Prague-Dejvice, Czech Republic

The PALM 6.0 model system has been rapidly developed in the recent years with respect to its capability to simulate physical processes within urban environments. In this regard, it includes e.g. energy-balance solvers for building and land surfaces, a radiative transfer model to account for multiple reflections and shading, as well as a plant-canopy model to consider the effects of plants on the (thermo)dynamics of the flow. This study provides a thorough evaluation of modelled meteorological, air chemistry and wall-surface quantities against dedicated in-situ measurements taken in an urban environment in Prague, Dejvice, Czech Republic. Measurements included e.g. monitoring of air quality and meteorology in street canyons, surface temperature scanning with infrared camera and monitoring of wall heat fluxes. Large-eddy simulations (LES) for multiple days within two summer and three winter episodes that are characterized by different atmospheric conditions were performed with the PALM model driven by boundary conditions obtained from a mesoscale model. For the simulated episodes, the resulting temperature, wind speed and concentrations of chemical compounds within street canyons agreed well with the observations, except the LES did not adequately capture nighttime cooling near the surface at certain meteorological conditions. In some situations, less turbulent mixing was modelled resulting in higher near-surface concentrations. At most of the surface evaluation points the simulated wall-surface temperature agreed fairly well with the observed one regarding its absolute value as well as daily amplitude. However, especially for the winter episodes and for modern buildings with multi-layer walls, the heat transfer through the wall is partly not well captured leading to discrepancies between the modelled and observed wall-surface temperature. Furthermore, we show that model results depend on the accuracy of the input data, particularly the temperatures of surfaces affected by nearby trees strongly depend on the spatial distribution of the leaf area density, land-surface temperatures at grass surfaces strongly depend on the initial soil moisture, or wall-surface temperatures depend on the correct prescription of wall material parameters, though these parameters are often not available with sufficient accuracy. Moreover, we also point out current model limitations, here we particularly focus on implications with respect to the discrete representation of topography on a Cartesian grid, complex heterogeneous facades, as well as glass facades that are not well represented in terms of radiative processes. With these findings presented, we aim to validate the representation of physical processes in PALM as well as to point out specific shortcomings. This will help to build a baseline for future developments of the model and for improvements of simulations of physical processes in an urban environment.

Study on Flow and Heat Transfer Characteristics of Supercritical Kerosene in a Round Tube

The finite volume discrete solution of the Navier-Stokes equation and the RNG model of the turbulence model are used to numerically simulate the flow and heat transfer characteristics of supercritical kerosene in a circular tube. The results show that as the inlet mass flow increases, the wall surface temperature and the central flow oil temperature gradually decrease, and the pressure loss becomes larger. As the inlet temperature increases, the wall surface temperature and the central flow oil temperature both increase. When the heat flux density is constant, as the pressure increases, the deterioration of heat transfer will be weakened, and increasing the pressure can improve the effect of convection heat transfer.

Cooling and Energy-Saving Performance of Different Green Wall Design: A Simulation Study of a Block

To mitigate the urban heat island (UHI) and release the low carbon potential of green walls, we analyzed the cooling and energy-saving performance of different green wall designs. Envi-met was applied as the main simulation tool, and a pedestrian street named Yuhou Street was selected as the study object. Four designs of walls were summarized and simulated, demonstrating the living wall system (LWS). Super soil had superiority in cooling and energy saving. Outdoor air temperature, indoor air temperature, outside wall surface temperature, and inside wall surface temperature were analyzed. Apart from the outdoor air temperature, the other three temperatures were all significantly affected by the design of green walls. Finally, energy savings in building cavities were determined. The indoor energy saving ratio of the LWS based on super soil reached 19.92%, followed by the LWS based on boxes at 15.37%, and green facades wall at 6.29%. The indoor cooling powers on this typical day showed that the cooling power of the LWS based on super soil was 8267.32 W, followed by the LWS based on boxes at 6381.57 W, and green facades wall at 2610.08 W. The results revealed the difference in cooling and energy-saving performance of different green walls in this typical hot summer area.

Investigation of ash deposit formation on heat transfer surfaces of boilers using coals and biomass

Combustion of coals and biomass in boiler furnaces leads to formation of fireside deposits on irradiated and convective surfaces. This problem is not a new one, but it became one of the main operational problems in boilers using low rank coal and some sort of biomass. In the paper presented are the results of research of ash deposit processes in laboratory conditions. An experimental furnace was used for these purposes. The experiments were performed on a tubular experimental furnace which ensures appropriate temperature and mass transfer conditions for physical and chemical transformations of the mineral matter of fuel as in real conditions. The main working parameters can be varied in wide ranges. The influence of grinding fineness, excess air and wall surface temperature was analysed. Also, an ash related problems during coal and biomass combustion was considered. Key empirical correlations for slagging and fouling were tested. Two types of Serbian coals (Kolubara and Kosovo) and several biomasses were analysed. It was shown that many sorts of biomass and Kosovo coal have a great propensity to slagging and fouling.

ANALISA PERBANDINGAN SUHU PERMUKAAN DINDING RUMAH VERNAKULAR PANTAI DAN GUNUNG

Research on thermal performance will have implications for building energy savings. The method of discussing thermal performance is varied. In this study will look at the performance of the building envelope in creating thermal comfort of buildings. The study used a field study by comparing the temperature of wall surfaces in vernacular houses in coastal and mountain areas. Measurements were carried out for 5 days in three different periods, namely the dry season to rain, the rainy season and the rainy season to the dry season. The results showed differences in wall surface temperature between vernacular houses on mountains and beaches. This is in accordance with the conditions of climate variables at different locations in height. The location of the beach has a higher tendency than the location of the mountain.Keyword: wall surface temperature, vernacular house, thermal performance Abstrak: Penelitian tentang kinerja termal akan berimplikasi pada penghematan energi bangunan. Metode pembahasan kinerja termal banyak ragamnya. Pada penelitian ini akan melihat kinerja selubung bangunan dalam menciptakan kenyamanan termal bangunan. Penelitian menggunakan studi lapangan dengan membandingkan suhu permukaan dinding pada rumah vernakular di daerah pantai dan gunung. Pengukuran dilakukan selama 5 hari pada tiga periode yang berbeda yaitu musim peralihan kemarau ke hujan, musim hujan dan musim peralihan hujan ke kemarau. Hasil penelitian menunjukkan perbedaan suhu permukaan dinding antara rumah vernakular di gunung dan pantai. Hal ini sesuai dengan kondisi variabel iklim pada lokasi yang berbeda ketinggiannya. Lokasi pantai mempunyai kecenderungan lebih tinggi dibanding lokasi gunung.Kata Kunci: suhu permukaan dinding, rumah vernakular, kinerja termal