Simplified Surface Temperature Modelling Jun Hao Koh, W. S. Koh Abstract Thermal load on buildings is the net accumulation of heat from the Sun, sky and surrounding surfaces in the built environment. In this study, a simplified 1D heat balance model was developed to provide an overview on the variation in surface temperature of conventional and high performance façade. This was done in conjunction with a simplified view factor and convective model. The model demonstrates good agreement with the overall trend of the measured surface temperatures throughout a day for two different industrial buildings. Virtual thermal performance evaluation of different façade materials is carried out to provide an insight on the effect of the potential retrofit of the existing building with high performance facade. An accurate prediction of the surface temperature will enable an accurate prediction of thermal comfort metric, such as mean radiant temperature, and expected impact of radiative thermal loading for different façade technologies in the tropical outdoor environment Include Equation for convective term Period of measurement (Transition monsoon season). Low convective resulting radiative component being the main contributor Include only SF30% for Ayer Rajah Have publication list in final report Introduction Results & Discussion Heat Transfer in Urban System Calibration of Model Radiative Heat Transfer Direct Solar Shortwave Radiation Atmospheric Longwave Radiation Longwave Radiation emitted from Urban surfaces Convective Heat Transfer Forced Convection (Wind from Environment) Natural Convection (Temperature Difference) Conductive Heat Transfer Heat Conduction of thermal energy into building H can be varied throughout the day to fit the modelled result with the measured data to compensate for the lack of information. Water-proof concrete SF-30% [4] Mass density: Conductivity: Heat Capacity: RMS error 1790Kg/m3 0.71 W/(m K) 880 J/(Kg K) 4.12 Different types of material can be used in the model to identify possible materials being used as the surface 1D Heat Balance Model To determine surface temperature, a 1D Time-Dependent energy balance equation was used [1]. The Model was found to be able to capture the surface temperature trend of a horizontal surface with the measured irradiance data on that day. Total radiation absorbed is contributed by Direct Solar, Diffused Sky, Atmospheric Longwave and radiation reflected and emitted by urban surfaces weighted by view factor. Simplified Heat Convective model was used to describe natural convection occurring on the surface, where 𝐻 to be 5.6 as minimum value [2]. Surface temperature obtained from the model has shown to be in good agreement with the measured data (RMS < 2) For South walls of Clean Tech One and Two, even though façade technology used are different, material of the façade used is key in surface temperature change throughout the day. Objective Site Implementation of Façade Technology Calibration of model to experimented sites for both horizontal and vertical surfaces Use of calibrated model to conduct a virtual site study on the thermal performance of different façade technology Methodology Experimented Site View Factor Configuration Simulated Surface temperature reach close to 60oC due to the highly conductive material of the façade. Surface temperature reaches 2.5oC lower than the measured concrete surface. This could present possible reduction in urban heat island effect. Simple Geometrical interface was used to describe the interface between the building and the surrounding (e.g. Tree Canopy and road) Conclusion Façade Technology 1D Time-Dependent Energy Balance model presents a fast method to predict surface temperature throughout a whole day with the irradiance as its primary data input. The model is valid in condition where there is strong Solar irradiance and light wind. Using the calibrated model, virtual surface temperature simulation can be carried out to evaluate the performance of various façade technology. Aerial View of experimented sites. Solar radiation geometry between the sun and the sites were determined Aluminum Cross sectional view of the façade used by the buildings. Material of the façade was included in the implementation of the model Acknowledgment Model made use of the irradiance data collected at the rooftops used as inputs for the calculation of surface temperature. View Factor was determined using numerical Monte Carlo Integration [3]. We would like to sincerely thank JTC and SMM Pte.Ltd. for making the site available for us to conduct the measurement. References [1] Çengel, Y. A. (2003). Heat transfer: A practical approach. Boston: McGraw-Hill. [2] Qin, Y., & Hiller, J. E. (2013). Ways of formulating wind speed in heat convection significantly influencing pavement temperature prediction. Heat and Mass Transfer, 49(5), 745-752. doi:10.1007/s00231-013-1116-0 [3] Howell, J. R. (n.d.). A CATALOG OF RADIATION HEAT TRANSFER CONFIGURATION FACTORS. Retrieved from http://www.thermalradiation.net/tablecon.html#A1 [4] Asadi, I., Shafigh, P., Hassan, Z. F., & Mahyuddin, N. B. (2018). Thermal conductivity of concrete – A review. Journal of Building Engineering, 20, 81-93. doi:10.1016/j.jobe.2018.07.002